We feel a slight anxiety. The receptionist is a pleasant elderly gentleman, who nevertheless increases our unease by asking, "You're not reporters, are you? A sense of transparent culpability, not experienced since Sunday school decades ago, accompanies us into the exhibition rooms. For this museum raises one of the most profound questions that humanity can ask—Where do we come from? We move through a series of small halls, named for the Six Days of Creation. In the first, light is divided from the darkness; in the second, a firmament appears; in the third, the seas are divided from the dry land.
All this is visualized with the help of rather schematic artwork, to the accompaniment of classical music. But the hall of the Fifth Day really comes alive: there's an aquarium with real fish and an aviary with real birds, although the birds' trills and warbles are piped in. The next hall has even more living creatures: a poisonous-looking frog, a snake or its shed skin, at least , and even a herd of giant Madagascan cockroaches.
And humans, of course—represented by their skulls. In the next hall, the significance of the Seventh Day is explained: God rested from His labors, thus marking the end of the period in which He created the universe and the beginning of the period, still continuing today, in which He actively upholds His Creation. The Seven Days of Creation by no means exhaust the museum's exhibits. Other rooms take us inside Noah's Ark, to the eruption of Mount St. Helens, to the Grand Canyon, to the interior of a glacier.
We see the tower of Babel and pass through the Ishtar Gate, and we file down a corridor between portraits of creationists on the left, and evolutionists on the right—the saints and sinners of the Great Debate. If the museum based its case simply on a divinely inspired faith in what the Bible says, it would be of limited interest to us. But far from it: The museum's whole purpose is to show how we can deduce the truth of the Bible story from objective study of the world around us— from science, in fact. It could properly be called the Museum of Natural Theology, for that is the name of the venerable branch of philosophy that seeks to recognize God through Reason and the study of His Works.
In making this case, of course, the museum has to face serious obstacles. Because of the detailed genealogies recounted in Genesis, the museum needs to place the beginning of all things no more than about 10, years in the past, while most astronomers and cosmologists claim that our universe is a million times older.
The museum must compress into a mere six days processes that, in the view of the majority of scientists, took more than ten billion years. And it must make intentional what most scientists consider, in a deep sense, accidental. The museum does not shirk this challenge. It expresses open antipathy toward Christians who try to smooth over the gulf by, for example, asserting that the "days" of Creation were metaphors for 12 ORIGINS longer periods of time: that they were in fact "ages" or "eons. It also rejects the strategy, favored by some Christian groups, of pushing God's creative role backward in time, allowing the latter part of Creation to go forward by purely natural processes.
Some believe, for example, that God lit the spark of life on Earth but allowed natural selection to do the job of getting from microbes to humans. This, in fact, was the view publicly espoused by Charles Darwin, though his private beliefs, as we shall see later, were different. With discoveries in physics and astronomy, there has been pressure to push God's role back even further. The British cosmologist Stephen Hawking, in his book A Brief History of Time, tells how he attended a scientific meeting at the Vatican at which the Pope admonished the conferees not to discuss what happened before the Big Bang, because that was God's province.
Yet Hawking's lecture at the conference concerned the possible circularity of time, a hypothesis that, if true, would make the phrase "before the Big Bang" meaningless!
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How then, does the museum propose to explain the apparent discrepancies between the Bible story and the usual teachings of science? There are several basic points. One is that, according to the museum, God created all things, including living creatures, in a fully functioning, mature state. Thus, Adam and Eve were created as normal adults, in possession of navels, for example—just as they are portrayed by Diirer and a hundred other artists.
But seeing their navels, we think of umbilical cords and therefore assume that Adam and Eve were once fetuses—which they were not. And seeing the Tree of Knowledge, we assume that it was once a seed, and so on. There is the deceiving appearance of a past. The same phenomenon, the museum argues, could explain how stars appeared in the sky on the Fourth Day, even though it would take many years for photons, traveling at the speed of light, to reach us from the newly created stars.
God may have created a "functionally mature" state, including both the stars and the entire stream of photons traveling from it to us, in a single act. But seeing the photons, we naturally imagine that they originated from the star many years previously. Of course, this line of thought can lead us into dangerous territory. Is it not equally possible that the universe is much younger than the Bible tells us?
That vivid memory we have of reading this morning's newspaper, and every earlier memory—were they perhaps implanted in our brains to make us "functionally mature"? Do our past lives resemble those wildlife dioramas we loved as children: a couple of stuffed gazelles up front, and the rest painted on the backdrop? How to distinguish reality from illusion becomes an insoluble dilemma, once one posits the intentional creation of "mature" systems. The museum presents a second line of argument to explain the discrepancies between creationism and conventional science.
Most scientists, it argues, assume that natural processes have always occurred at the same rate. If the half-life of a radioactive isotope the time required for half of the atoms to decay into other atoms is now a million years, it was always a million years, because the physical laws that control radioactive decay have not changed since atoms first existed.
But, the museum reminds us, we can't go back into the distant past and measure the decay rate then; therefore, the assumption of a constant rate is unjustified, and so is any finding based on that assumption, such as the age of a rock or of a fossil embedded in that rock. The Seventh Day of Creation, when God rested, was one particular time when the rates of physical processes might well have changed. Before then, light may have traveled at infinite speed, for example, thus providing an alternative explanation for how stars were seen on the day they were created.
As a matter of fact, it is not quite right to say that scientists simply assume the constancy of process rates. Many processes on Earth, such as the rate of deposition of sedimentary rocks, have been shown to vary greatly over time. Even the constancy of the great "constants," such as the strength of the gravitational force, is open to scientific debate: there are cosmologists who have developed models in which the force of gravity has changed since the Big Bang. But we can study process rates in the past with the same kinds of certainties and uncertainties with which we study them today.
Some kinds of radioactive decay, for example, leave permanent tracks in rocks—rocks whose age can be estimated by other means, such as their degree of weathering or chemical transformation, their position in a sedimentary series, and so forth. One can count these tracks and thus determine whether the process of radioactive decay took place at the same rate in ancient times as it does today. In the end, our knowledge of process rates in the past is built on the mutual consistency of events that happened then, just as our knowledge of process rates today is built on the con14 ORIGINS sistency of events happening now.
To believe that the apparent great age of the universe is an illusion caused by decreasing process rates is really to say that time itself ran faster in the past—an assertion that belongs to metaphysics, not science. Finally, the museum confronts the findings of conventional science by contesting the findings on science's own terms—by getting into the nitty-gritty of the data and challenging every piece of evidence, and every interpretation, that runs counter to the Bible story.
Does radiometric dating of rocks at the bottom of the Grand Canyon prove them to be a billion years old? No, because if one applies the same technique to obviously recent lava flows near the canyon's rim, one gets an even earlier date—or so the museum's experts allege. Therefore the dating technique is patently untrustworthy. Did the dinosaurs go extinct 65,, years ago, as the fossil record suggests? No, because dinosaurs were frequently and unambiguously sighted by humans— they called them "dragons"—as recently as the Middle Ages. Dinosaur fossils, like all other fossils, are merely the remains of the animals that drowned in Noah's Flood.
Others survived, either by swimming or by being taken on board the Ark. At the museum, a painting of the Ark's interior shows what seems to be a stegosaurus lounging peaceably in its stall. The accompanying panel goes through the arithmetic to show that the Ark was plenty big enough to hold all 50, "kinds" of animals.
The Museum of Creation is an offshoot of the Institute for Creation Research,2 whose offices are located in the same building, and the Institute's Senior Vice President, Duane Gish, is a Berkeley-trained biochemist who yields to no one in the discussion of scientific minutiae, whether it be the proper interpretation of an indistinct band in a sedimentary rock or the assessment of transitional forms between various fossil hominids. Woe to the "evolutionist" who agrees to debate Gish on a college campus or at a church meeting: he or she will be buried under an avalanche of particularities that collectively obliterate the conventional scientific worldview.
Gish and the institute's founder, Henry Morris, have written a series of books that promote creationism as a science and label the theory of evolution a "religion"—and a false one, to boot. Of course, creationism should be taught in schools. Where does the institute stand on extraterrestrial life?
Bill Hoesch, the institute's Public Relations Officer, tells us that nonintelligent life—such as microbes—poses no problems. But there is nothing to say that microbes do not exist elsewhere. With intelligent life it's a different story, especially if that life is in an "unfallen" state.
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In retribution for mankind's Original Sin, God put His Curse on the entire universe, Saint Paul tells us in Romans "For we know the whole creation groaneth and travaileth in pain together until now". If innocent extraterrestrial creatures are laboring under this Curse, it would raise the question of whether God had acted unjustly. So creationists doubt that such beings exist. As we leave the museum and stand blinking in the afternoon sunlight, we have the sense of having torn ourselves free from a dark web of unreason, a web that might have held us in its threads until the brains were sucked out of our skulls.
We feel the impulse to flag down one of those trucks hurtling by on Route 67, to breathlessly recount our trip to Eden and the saurian Ark, as if we had just returned from an alien abduction. Surely the driver would comfort us with the assurance that everything we saw and heard was an illusion? Perhaps not. Creationism, in one form or another, is the majority worldview. Most people believe that the universe was brought into existence by divine intention, and about 40 percent of the population of the United States, according to a survey by U.
News and World Report, believes in the literal truth of the Genesis story. Henry Morris, Duane Gish, and their colleagues at the Institute for Creation Research are unusual only in the fervor with which they explore the ramifications of that belief. Of course, the Museum of Creation does represent something of an extreme position within theology. Natural theology, as practiced today, has many different perspectives on the identity of God and His role in the creation of the universe and life.
For example, one school of liberal theology speaks of God as a process that is coming into being, rather than as a substance coexistent with but transcendent over matter. Process theologians, and many other liberal theologians, would not dream of contesting the date that dinosaurs went extinct, or any other scientific findings related to our origins. Our purpose in visiting the museum was not to gain an overview of current theological perspectives, but to sample the least naturalistic among them, in order to provide a contrast with what follows: The effort to explain the origins of life by natural processes.
The gods exist, he said, but they are irrelevant. Our world assembled itself spontaneously, by the aggregation of atoms moving through a boundless extent of space. No Prime Mover was needed. Nor did the origin of life require divine intervention. Here we call on a group of five scientists—Jeff Bada, Stanley Miller, Gustav Arrhenius, Leslie Orgel, and Gerald Joyce— who are the closest thing to disciples of Lucretius that one may hope to find in the world today.
Not that they are concerned with the entire panoply of Creation. It's that "golden rope" part that obsesses them. Can one explain the origin of life without it? It turns out to be a Herculean undertaking. Yet the La Jolla scientists actually devote the bulk of their attention to terrestrial life—to "endobiology," if you like. Admittedly, we're biased by what we know about life on Earth.
But I think the consensus is, if we can understand the processes that lead up to the origin of life, then given the proper conditions, it will probably be a universal process. In fact, his research has taken him onto the high seas—he has sampled fluids emitted by deep-sea volcanic vents, for example.
His office is no more than a few hundred feet from the ocean, at the Scripps Institution of Oceanography. And the ocean, Bada and his colleagues believe, is where life most probably originated. But water alone isn't enough. Terrestrial life is made of carbon-containing molecules—organic compounds—many of which also contain nitrogen, oxygen, and other elements. And assembling these molecules takes energy. As mentioned earlier, Charles Darwin publicly expressed a belief that Earth's first creatures were divinely made.
Perhaps he felt that he had rocked the boat sufficiently with his theory of evolution—that he would endanger the seaworthiness of his whole enterprise if he went further. But in a private letter, written in , he did put forward the idea that life arose spontaneously, "in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. In the Russian chemist A. Oparin suggested an answer. In this "reducing" hydrogendonating atmosphere, a large variety of organic molecules formed and were washed by rain into the ocean, gradually building up a "prebiotic soup.
Haldane, who had been thinking independently along the same lines. The very first organisms, Oparin believed, were extremely simple: they didn't need to have complex metabolic pathways because everything was available in the soup—both molecules to make up their structure such as amino acids and molecules to break down for energy.
It was the ultimate free lunch. Eventually, of course, the goodies ran out, and organisms had to learn how to make an honest living. However long that initial period may have lasted—a hundred thousand years, a million years, ten million years—it could have been no more than a moment in the Earth's history. In , as a graduate student working in the laboratory of Harold Urey at the University of Chicago, Miller performed an experiment that made him famous and established origin-of-life research as an experimental science.
Subsequent experiments of a similar kind have revealed that a wide variety of amino acids, as well as the nucleosides that are the building blocks of DNA and RNA, are readily formed in experiments of this kind. Thus, Miller's work suggested that the building blocks of life were indeed there, free for the taking, in the Earth's primordial ocean. It was just a matter of putting them together into an organism. Asked what it was like to have performed such a famous experiment while a graduate student, Miller tells us: "I'm sure it helped my career.
But in terms of famousness—I don't know. A lot of people felt that it wasn't really science. It was attacking a problem that people didn't think about. This is on account of changing views about the composition of the Earth's early atmosphere. To understand this change, we must take a look at how scientists think the Earth and its atmosphere were created. According to current consensus, the Earth formed by the gathering together "accretion" of smaller objects, or "planetesimals," in the disk of gas and dust orbiting the evolving Sun, 4.
The main period of accretion lasted about million years. During this period, the heat generated by frequent impacts kept the Earth in a molten state. For several hundred million years after that, sporadic large impacts probably prevented life from establishing itself. One such impact—by an object at least as large as Mars—is thought to have kicked a large amount of material from the Earth's mantle into orbit around the remainder of the planet.
This orbiting material eventually accreted to form the Moon. It was once generally believed that the Earth's original atmosphere was drawn directly from the disk of gas and dust from which the solar system formed. If so, it would have resembled the present atmosphere of Jupiter and Saturn, being rich in hydrogen and hydrogen-containing molecules, such as ammonia and methane, and lacking molecular oxygen O2. This would have been a strongly reducing atmosphere and would have been appropriate for the synthesis of organic compounds by the methods that Urey and Miller proposed.
But according to the majority of contemporary researchers, the Earth was too small to attract or hold on to such a primordial atmosphere. The main gases produced by these processes would probably have been water vapor, nitrogen, carbon monoxide CO , carbon dioxide CO2 , and hydrogen. Hydrogen, however, is light enough to escape from the atmosphere into space and, therefore, would not have accumulated in significant concentrations.
Compounds such as methane and ammonia, if they were generated at all, would likely have been kept at very low concentrations by the destructive effect of the Sun's ultraviolet radiation. Geochemists have had a much harder time figuring out how organic molecules could have been generated in this neutral or mildly reducing atmosphere, compared with the strongly reducing atmosphere favored by Oparin, Urey, and Miller. It's not completely impossible.
These compounds can go on to build larger organic molecules. Still, the process is not very efficient. He suggests to us, for example, that methane might have been released from the deep-sea volcanic vents. The vents don't release methane now, admittedly, but they might have done so, Miller says, when the Earth's atmosphere and oceans lacked oxygen. There would still be the problem of how to protect that methane from the Sun's ultraviolet radiation once it entered the atmosphere.
But by happenstance, the Cornell astronomer Carl Sagan shortly before his death in , along with Chris Chyba, came up with a theory to explain how methane might have been protected. Sagan and Chyba came upon this idea because just such a smog layer does surround another body in the solar system— Saturn's largest moon, Titan see Chapter 3. We say "by happenstance" because Chyba and Sagan had not set out to rescue the Miller-Urey hypothesis. They wanted methane in the Earth's early atmosphere for a quite different reason.
Early in the 20 ORIGINS Earth's history, the Sun was not as bright as it is at present because its nuclear fires were concentrated in a relatively small sphere near its center. Thus, the early Earth received about 30 percent less sunlight than it does now. By rights, this should have allowed the oceans to freeze solid.
And once they had frozen solid, even the present-day Sun would be powerless to melt them because the ice would reflect most of the Sun's rays back into space. Chyba and Sagan were therefore looking for some way by which the early Earth might have been kept warm in spite of the Sun's faintness. A blanket of methane would do the job nicely, since methane is a greenhouse gas: it allows incoming sunlight to pass through to warm the Earth's surface, but it blocks the outgoing infrared radiation.
Ammonia, another powerful greenhouse gas, may also have played a more significant role than previously thought. In spite of these various mechanisms by which the Milley-Urey hypothesis might be rescued, enough doubts have been sown to motivate a search for alternatives. Jeff Bada, as well as Chyba and Sagan, have explored the viability of another theory: the idea that the organic compounds in the prebiotic soup were not synthesized on Earth at all but were brought to Earth by infalling meteorites, comets, and dustgrains.
All three of these kinds of objects can contain significant amounts of organic compounds. Meteorites, especially the class of meteorite known as carbonaceous chondrites, can contain as much as 5 percent organic material. The Murchison meteorite, for example, a carbonaceous chondrite that fell in Australia in , has been found to contain over seventy different amino acids, including eight of the twenty amino acids that are the building blocks of terrestrial proteins. Where these organic compounds originally came from is a topic we explore in Chapter 4.
Many organic compounds come in two mirror-image versions, which differ only in the three-dimensional arrangement of the bonds around one or more of the carbon atoms. The two arrangements are called, by convention, "left-handed" or "right-handed. Most probably, the choice of left-handed amino acids was made because there was a small excess of left- over right-handed amino acids in the prebiotic soup.
But it is very difficult to see how the local synthesis of amino acids on Earth the hypothesis favored by Stanley Miller could lead to more than the tiniest excess of one handedness over the other. In the early , several groups of organic chemists reported finding an apparent excess of left-handed amino acids in carbonaceous meteorites. This opened the door to a new hypothesis: the prebiotic soup was biased toward left-handed amino acids because meteorites, comets, and dust grains imported more left handed than right-handed molecules. The findings were not terribly convincing because of the possibility that the meteorite samples had become contaminated with left-handed amino acids of terrestrial origin.
In , however, John Cronin and Sandra Pizzarello, of Arizona State University in Tempe, reexamined the issue by looking at the chirality of individual amino acids in the Murchison meteorite, as well as in another carbonaceous chondrite. They found that it wasn't just the familiar amino acids used in terrestrial biochemistry that were biased toward the left-handed form, so were some exotic amino acids that are never found on Earth except in meteorites.
This finding seems to have disposed of the contamination issue and suggests that there was indeed a left-handed bias in the supply of amino acids that reached Earth from space. This in turn raises the question of why the extraterrestrial 22 ORIGINS supply should be biased toward one chirality, a question that we will discuss in Chapter 4. To evaluate the possible contributions of terrestrial-versus-extraterrestrial supplies of prebiotic chemicals, Bada tried to estimate how much organic material is reaching the Earth today.
He suspected as originally suggested by Edward Anders of the University of Chicago that the bulk of the material would be brought in on very small dust grains—perhaps 50 microns in diameter or so a micron is one-thousandth of a millimeter, or 0. Grains of this size don't heat up excessively as they enter the atmosphere; instead, they quickly decelerate and drift safely to the surface. To find these grains, Bada used the services of a group of French researchers, who collect and melt ice from the Antarctic—the land surface least contaminated by human activities.
Starting with tons of ice, Bada ended up with micrograms millionths of a gram—i gram is 0. He then analyzed this material for the presence of organic compounds and found amino acids—not just the usual amino acids that are found in terrestrial organisms which might represent contamination but also amino acids that play no part in terrestrial biochemistry and that therefore are almost certainly of extraterrestrial origin.
Micrometeorites in the millimeter-size range are generally heated to incandescence as they enter the Earth's atmosphere, producing the familiar "shooting stars," and any organic freight is therefore destroyed. But there is a range of larger objects—say cabbage sized or thereabouts—that bring organic compounds to the surface intact.
The surface layers of these meteorites do heat to incandescence during passage through the atmosphere, but their interiors remain cold. Much larger objects strike the Earth's surface with such force that the heat of impact destroys any organic compounds they contain. However, large objects not uncommonly break up in the atmosphere.
This happened, for example, with the "Tunguska object"—thought to have been a stony meteorite about meters across—that exploded in the air over Siberia in In such cases, the resulting fragments could descend to the surface more gently. There is another potential mechanism by which meteorites can contribute to the Earth's inventory of organic compounds, even if its own organics are destroyed on impact. But like that mechanism, the shock-synthesis of organic compounds works best in a strongly reducing atmosphere and is therefore not really a means to explain how organics could form in a more plausible early atmosphere.
Bada, as well as other researchers such as Chyba and Sagan, have gone through the arithmetic to see if enough extraterrestrial organic material could have reached the early Earth to make a reasonably thick "prebiotic soup. But in fact there is a process that destroys organic compounds in the ocean: this is the cycling of seawater though the deep-sea volcanic vents.
Seawater in the vicinity of the midocean ridges percolates down to the magma beneath the seafloor, where it is heated and returned to the ocean through the vents. Bada has verified this by directly sampling the water as it passes through the vents, both in the Pacific Ocean and in the Gulf of Mexico: it is indeed "clean. Therefore one doesn't have forever to build up a prebiotic soup, and the rate at which organic compounds accumulate is crucial.
The bottom line, according to Bada, Chyba, and Sagan, is as follows. If the early Earth had a strongly reducing atmosphere, organic compounds from all sources would have built up to a steady-state concentration of about o. Not quite chicken broth, but in the same ballpark. If the atmosphere were neutral or mildly reducing, on the other hand, the prebiotic soup would have been a thousandfold more dilute—only about a milligram per kilogram of seawater.
Of course, no one knows how thick a soup would be needed to allow life to get rolling. And it's possible that the concentration of organic material could build up to higher levels in certain favorable locations—in drying tidal pools, for example. But still, the thousandfold difference makes the original reducing atmosphere, and the MillerUrey mechanism, very attractive.
What's more, says Bada, the MillerUrey mechanism produces "better-quality" chemicals: a wide range of amino acids and nucleosides, whereas what comes in from space tends to be much more restricted—glycine the simplest amino acid and a lot of pretty useless compounds. Specifically, he pointed out that ferrous iron sulfide and hydrogen sulfide, both of which are present at the vents, constitute a powerful reducing system that might be able to convert carbon dioxide a gas that is released from the vents into a variety of organic compounds.
These compounds, he suggested, might remain adsorbed onto the iron sulfide crystals where they were generated, thus building up high concentrations of organic molecules near the vents. If so, a prebiotic soup in the free ocean might be completely unnecessary. Wachtershauser's "ironsulfur world" has garnered considerable attention, particularly in the light of evidence, discussed later, that heat-loving organisms are the ancestors of all present life-forms on Earth. According to Miller and Bada, however, Wachtershauser's scheme doesn't hold up in practice.
Miller and Bada believe that the proposed reactions, although theoretically feasible, require the reactants to jump over energy barriers that are not easily crossed in the absence of catalysts. The vents don't make organics, they destroy them. Gustaf is the grandson of Svante Arrhenius, a brilliant and unorthodox Swedish physicist who won a Nobel Prize in for a fundamental discovery in electrochemistry—that electricity is carried in solution by charged ions. But Svante also wrestled with profound questions about life and the universe.
For like everyone in that period, he thought that the universe was infinite in time. It was more natural to believe that it was everywhere, that it cruised around from one place to another. Rather than worry about how life was created here on Earth, it made more sense to think how it might be transported here from elsewhere.
He felt that he had hit upon a new way by which spores might be transported across space, through the pressure exerted by light. This phenomenon of light pressure, or radiation pressure, had just recently been discovered. Svante Arrhenius's theory of "panspermia" ran into a serious problem in when the French plant physiologist and radiation pioneer Paul Becquerel showed that small organisms in space would be rapidly killed by the sun's ultraviolet radiation. Later, the discovery of cosmic rays made the survival of tiny spores in space even less plausible.
Yet, Svante Arrhenius held on to his theory with almost mystical fervor. He found enormously appealing the notion that all organisms in the universe were related. Perhaps life had always existed, and the question of how it might be created was therefore superfluous. Gustaf Arrhenius, now in his seventies, betrays his Scandinavian origin with his accent, his careful choice of words, and his urbane 1. And something still draws him to the chilly North, for he has recently spent time prospecting for geological specimens on the western coast of Greenland.
There, he and his colleagues found what may be the most ancient remaining traces of life on earth. Searching for the origins of life in the geological record has, of course, occupied scientists for generations. Fossils are abundant in sedimentary rocks as old as the Cambrian, a period about to million years ago when life diversified into all kinds of exotic and soon-to-be-discarded forms. But before the Cambrian, it gets difficult. Organisms were mostly microscopic; or, if larger, they lacked the hard body parts that readily fossilize. Even worse, the more ancient sedimentary rocks themselves become harder to find, and when they can be located, they mostly turn out to have spent time at high temperature and pressure in the depths of the Earth, an experience that plays havoc with any fossils that the rocks may have contained.
The oldest clearly recognizable fossilized organisms were found in the late in Western Australia by William Schopf of uciA. Schopf s organisms were filamentous microbes, very much resembling certain kinds of modern cyanobacteria—bacteria that get their energy from sunlight and that release oxygen in the process. The morphological similarity between the 3. Arrhenius knew that Schopf s organisms were not likely to have been the Earth's first inhabitants—they were too complicated. So Arrhenius and research fellow Steve Mojzsis went looking in the Isua formation of West Greenland, which contains the oldest known sedimentary rocks—rocks that were laid down about 3.
Arrhenius and Mojzsis did not find any recognizable organisms in these rocks, which have been subjected to periods of intense heat and pressure since their deposition. But they did find microscopic grains of apatite, a form of calcium phosphate that is generally produced by living organisms rather than by geochemical processes. And within these grains were patches of carbonaceous material that might be the charred residues of ancient organisms.
To pin down the matter a little more closely, Arrhenius and Mojzsis wanted to know the isotopic composition of the carbon in these patches. That is because the enzymes that handle carbon work better on the light 12C isotope than on the heavier 13C isotope. The even heavier 14C isotope does not come into the picture, because it disappears by radioactive decay over much shorter time periods than we are considering here.
Schidlowski had interpreted this finding to mean that the carbon was of biogenic origin. In a machine somewhat resembling an electron microscope, a tiny beam of positively charged cesium ions was aimed at the individual carbonate patches. The carbon atoms were vaporized and fed into a mass spectrometer, which sorted them out by mass and electric charge. It turned out that the carbon isotope ratio was indeed that expected for carbon of biogenic origin, confirming Schidlowski's interpretation. He can say nothing about what kind of organisms they might have been, except that, given their selectivity for 12 C over 13C, they probably had enzyme-catalyzed metabolic pathways not unlike those of organisms existing today.
Earth's first organisms, therefore, should have lived long before that period. These discoveries radically alter the scenario for the origin of life on Earth. Before the discoveries were made, it was possible to believe that the Earth lay fallow for a billion years or more, cool enough to sustain life, and rich in every nutrient required for life—yet stubbornly lifeless.
What was missing, it seemed, was only the pinch of fairy dust that set everything into jangling motion. The origin of life was a probability barrier—an unlikely event that took long ages to happen, even when all circumstances seemed to favor it. But now it begins to look like the very opposite: that life arose at the very first possible moment—or even earlier! But when was the "first possible moment"? That depends on what happened to the Earth during its first billion years, and unfortunately the history of this period is hard to reconstruct.
Very large impacts, massive enough to completely vaporize any oceans that may have existed, probably continued until at least 4. Even after that period, however, major impacts apparently continued. In fact, to judge from the craters on the Moon, whose ages have been established by the study of samples returned by the Apollo astronauts, intense bombardment continued until at least 3.
How can this be reconciled with an apparent origin of life well before 3. One possible answer is that life arose on the deep-ocean floor, in an environment protected from all but the most cataclysmic impacts. This environment would also have been safe from another hazard— ice. For according to some theorists, the oceans did indeed freeze over repeatedly, to a depth of thousands of feet, only to be melted by the next all-incinerating impact.
Not for nothing are the Earth's first million years referred to as the Hadean Eon—the "age of Hell. Arrhenius has a different, somewhat unconventional answer to the paradox. A third possibility remains unspoken—that the elder Arrhenius was right, and the Earth was indeed seeded by living organisms from other worlds. As we shall see, that could have happened otherwise than by means of light-borne spores. Leslie Orgel, whose laboratory is at the Salk Institute, across the road from UCSD, is another distinguished elder statesman of science.
Like Arrhenius, he has eschewed retirement in favor of a continued struggle with the vexatious problem of how life originated. As if worn down by the effort, the British-born chemist affects a hangdog world-weariness. When asked his opinion of some new theory, Orgel is likely to remark that "it's no worse a possibility than the others.
Hearing that we were working on a book about life in the cosmos, Orgel comments simply: "My opinion is that we have no way of knowing anything about the probability of life in the cosmos. It could be everywhere, or we could be alone. He has concerned himself with the question of how one might get from a prebiotic soup of organic chemicals to an actual living system. He has concluded that the life that we're familiar with today—based on the triumvirate of DNA, RNA, and protein—was almost certainly not the original form of life on Earth. Instead, it was likely preceded by another, radically simpler form of life, in which RNA ruled alone.
RNA plays several key roles in the execution of that information, that is, in carrying out the synthesis of proteins under genetic instructions. Proteins are largely responsible for the structure of living matter and, as enzymes, for catalyzing the innumerable metabolic reactions of 'life'—including the reactions that lead to the assembly of DNA and RNA. Seemingly, neither could come into being without the other, yet the idea that they arose simultaneously and by chance strains credulity. They rejected proteins as the primordial macromolecules because there was no obvious way by which proteins could replicate themselves.
Nucleic acids, on the other hand, have the nucleotide base-pairing mechanism: guanine to cytosine and adenine to thymine or to uracil in RNA. This mechanism would offer at least the theoretical possibility of replication without any assistance from proteins. Of the two nucleic acids, Orgel, Crick, and Woese favored RNA as the first-comer because of the relative ease with which the building blocks of RNA could be synthesized.
There are three challenging requirements for an "RNA world. Second, there must be a mechanism for an RNA molecule to assemble polymerize from those building blocks without the help of protein enzymes. And third, there must be a mechanism for RNA molecules to form copies of themselves replicate , again without the help of proteins. In this diagram a short stretch of the familiar double helix, formed by twin sugar-phosphate backbones, has been untwisted to reveal the molecule's ladder-like structure.
The four bases are adenine A , thymine T , cytosine c , and guanine c. In RNA, the sugar is ribose rather than deoxyribose, and thymine is replaced by uracil. Nucleosides are nucleotides without a phosphate group. As we've mentioned, the bases may have been available from reactions in the primordial soup, or may have been imported on micrometeorites.
But making ribose and adding it on to the bases is more problematic. The difficulty is that, while it is possible to find circumstances in which ribose is made, it generally shows up as a small constituent in a mixture of many different molecules. Some of these molecules are likely to interfere with subsequent processes, just as mixing different-sized ball bearings will bring a machine grinding to a halt. Still, Orgel is reasonably optimistic that a plausible pathway will eventually be found, perhaps involving inorganic catalysts such as mineral surfaces.
Mineral surfaces might also play a role in the polymerization of RNA. James Ferris, who directs the New York Center for Studies of the Origins of Life, has managed to get ribonucleotides to assemble into short chains on the surface of a kind of clay called montmorillonite. Again, it seems as if further research may find circumstances in which long chains of RNA will be formed. Getting RNA to replicate is the toughest problem. For this to happen, new ribonucleotides must bind to the existing chain, following the rules of base pairing: uracil binds to adenine, cytosine to guanine.
The new chain, with a base sequence complementary to the original one, must now serve as the template for a second round of ribonucleotide binding, which produces a thirdgeneration chain identical to the first. Unfortunately, although Orgel has had some limited success with the first round of copying, he has not been able to get both steps to happen. No RNA molecule has been replicated in the laboratory without the aid of protein enzymes.
If someone found a magic mineral which you shook up with formaldehyde or cyanide and phosphate, and out came ribose phosphate—then the whole problem would be different. Some simpler system had to precede it. Among the candidates for such a system is a macromolecule called peptide nucleic acid PNA. This molecule is not known to exist in nature; it was designed by Peter Nielsen of the University of Copenhagen.
Anything much more complicated than that is implausible. It's so hard to make RNA. If nothing simpler can replicate, that would be a strong argument for the existence of God. The organisms would not travel as free-floating spores, of course. Rather, they would travel in the interior of meteorites.
It's now well established that meteorites have traveled from the Moon and from Mars to Earth. Doubtless, they have traveled in the other direction too. Deep inside the meteorite, microbes would be shielded from harmful radiation, and the near-absolute-zero temperatures would keep the frozen organisms in pristine condition. Takeoff and reentry are problematic, off course. But we know that the interiors of meteorites can remain cold during reentry.
As for the initial impact that kicks the rock into space, Orgel draws an analogy to the circus performers who allow themselves to be shot from guns. Bada and Orgel are members of a NASA committee that concerns itself with the possible risks of bringing samples of extraterrestrial rocks back to Earth. Could microbes from another world set off a lethal pandemic here?
The maverick British cosmologist Fred Hoyle has been saying so for years; in fact, he believes that some of the great epidemics of human history were caused by bacteria and viruses that came from space. If so, the microbes would likely be similar enough to us in their basic biochemistry that they might be able to subvert our metabolic pathways, just as pathogenic terrestrial microbes do. But if those microbes belonged to a completely independent Life, he tells us reassuringly that "they could only eat us—nothing more subtle.
I suspect we have, haven't we? Nothing's known about it—what more is there to say? All theories are bad. Where Orgel is cautious to a fault, Joyce is brazenly optimistic. A couple of years ago, he asserted that life would be created in a test tube by the end of the twentieth century. Of course, that brings up the question: What is life'? Philosophers, theologians, and scientists have been torturing themselves over this for centuries. The folk definition of life is "that which is squishy. For a scientific definition, Joyce offers the product of a NASA workshop on the subject: life is a "self-sustained chemical system capable of undergoing Darwinian evolution.
Of course, that definition wouldn't sit well with the people at the Museum of Creation, who don't believe that evolution happens. And later, we will have the opportunity to question other aspects of it: whether, for example, a nonchemical system such as a computer program could ever be considered "alive. A "self-sustained" system, by the way, doesn't mean a closed system.
To maintain itself in the face of the second law of thermodynamics—the inevitable increase in disorder or entropy in a closed system—life must use energy from outside the system. This energy could be sunlight, it could be chemical energy locked in minerals, organic compounds, or other living creatures, it could even be electricity or gravitational energy. But whatever the energy source, this requirement ensures that life can only be understood in terms of its relationship with the environment. Joyce thinks that between life and non-life there's a sharp boundary. The origin of life wasn't the sequential appearance of gradually more lifelike' systems, from ones that were i percent living to ones that were percent living.
Systems gradually became more complex, certainly, but the appearance of life was at the point where such systems were able to record their phylogenetic history—which means informational macromolecules that can be replicated. In fact, he trained with Orgel at the Salk Institute before organizing his own lab at Scripps. But rather than focus on how RNA came to be, Joyce is engaged in the attempt to create a self-sustaining, evolving RNA system in a test tube.
He wants to bring the RNA world back to life. These molecules have the property not only of encoding information, but also of catalyzing enzymatic reactions—a function generally performed by proteins. Rather, it's simply that the particular sequence of nucleotide bases in a ribozyme causes the RNA molecule to fold up into a three-dimensional shape that is capable of catalyzing a particular reaction, just as the particular sequence of amino acids in a protein gives the molecule its particular enzymatic talent. If it could be found, many of the problems faced by Orgel would be circumvented. But no such ribozyme exists in the world today, as far as anyone knows.
If it existed in the RNA world, as Joyce believes, it has long since gone extinct. So how to re-create it? Just trying out a bunch of randomly chosen RNA sequences doesn't seem like a workable strategy, given the numbers involved. The molecule would probably have to be at least fifty bases long to do a reasonable job, but there are about possible RNA sequences of this length—that's one with thirty zeroes after it. If you laid out the sequences from here to the most distant observable object in the universe, you'd have to pack a hundred billion different sequences into every millimeter of the way.
Joyce's solution is to make evolution run backward. He starts with an existing ribozyme that can, to some limited degree, carry out a reaction that is a part of the desired "replicase" function. For example, it might be able to join two short stretches of RNA.
He puts this in a test tube along with a set of molecules, including DNA, protein enzymes, and nucleotides, which collectively allow the ribozyme to replicate. Within an hour, a single ribozyme molecule has multiplied a trillionfold. The trick is that Joyce arranges things so that the ribozyme's enzymatic activity is made part of the replication process. Thus, any ribozyme molecule that by chance mutates slightly, so as to perform a better enzymatic job than its peers, replicates faster.
It becomes the dominant type of molecule in the tube. Thus, the mixture self-evolves in a direction set by the experimenter.
The aim is to have the ribozyme evolve to a point where it can do without the DNA and proteins. In other words, the ribozyme has to evolve backward from our present world to the RNA world. Joyce hasn't achieved that yet. Continuous in vitro evolution, as it is called, seems to be a powerful technique for moving in a directed fashion through "sequence space"—the multidimensional realm of possible RNA sequences. One wonders what Darwin would think if he could learn of all the head-spinning theories, tortuous experiments, and confusing blind alleys that have bedeviled efforts to breathe life into his "warm little pond.
It's hard to say. But Leslie Orgel, who in many ways is the most pessimistic of the La Jolla scientists, nevertheless maintains a basic loyalty to the idea of a natural origin. The polymers that are the chemical basis of life are complicated. To assemble them by chance rolls of the dice seems to ask too much, even with an astronomical number of planets on which to roll them and 15 billion years to roll them in, for astronomical numbers are no match for hyperastronomical improbabilities.
Fred Hoyle put it succinctly, when he commented that the chances of forming the simplest life by random processes were about the same as the chances that a whirlwind sweeping through a junkyard might put together a Boeing airliner. Joyce's in vitro evolution hints at such a force.
But what is needed, it seems, is a theory that explains the self-organization of complex systems at a more fundamental, abstract level. In Chapter 6, we will visit one place where the search for such a theory is underway. In spite of the partial and incomplete picture that the La Jolla researchers have been able to paint, there is the thread of a story. There is something ominous about those transitions. These human analogies are foolish, of course, when talking about evolving chemical systems, but they're hard to avoid.
We ask Orgel whether he thinks that our own biological world will in time be taken over by the next level of complexity. We're thinking of intelligent computers or some such thing. But Orgel, ever the chemist, has his own ideas. Alkaloids are elaborate, nitrogen-containing compounds that include, for example, heroin and caffeine. And then one of them turns out to be a Frankenstein. De Duve, C. Vital Dust: Life as a Cosmic Imperative.
New York: Basic Books, Orgel, L. El Nino's battering storms brought mayhem to coastal California, but as they charged inland, a succession of mountain ranges squeezed the wrath out of them, and they had nothing but nourishing showers for the sunken valley on California's eastern border. Desert sunflower seeds, dormant for decades, have sprouted and blossomed by the million, carpeting the valley floor with a cloth of gold.
Yet one part of the valley has resisted the urge to bloom. At Badwater, the lowest and hottest spot in the Western Hemisphere, not a living thing is to be seen: all that meets the eye is a blinding expanse of white. Water reaches this spot, to be sure. It falls as rain. It trickles down from Telescope Peak, the n,ooo-foot summit that guards the valley's western wall. And the Armargosa River, usually a stony wash, but now almost fit for kayaking, brings runoff from the desert hills of western Nevada.
But once at Badwater, the water turns bad. It lingers for a few days in a shallow, mineral-charged lake, and then evaporates, or is sucked into the insatiable salt. With matted curly hair and beard, his shirt hanging half out of his jeans, he looks a little unkempt, and understandably so. He has spent one night sleeping at the side of the road and another in the campsite at Furnace Creek. His travel budget doesn't extend to motel rooms, it seems, and certainly not to a suite at the pricey Furnace Creek Inn. Besides, McKay is used to living rough. He has prospected for life in some of the world's least hospitable places: the Canadian Arctic, the wind-stripped Gobi Desert of Mongolia, the nitrate-laden expanses of Chile's Atacama Desert, and—on many occasions—the bone-dry interior of Antarctica.
Most of the time, he finds what he is looking for. Badwater is no challenge. McKay scans the featureless expanse with a practiced eye, selects a likely spot, and digs his penknife an inch into the salt. He removes what looks like a scoopful of fancy Italian ice cream: salt, for sure, but tinted in kaleidoscopic layers of pink and orange and green and black.
They face death by osmosis, of course—getting all the water sucked out of them. But they fight fire with fire: they jack up the concentration of solutes inside—potassium and small organic molecules—to match the concentration of sodium chloride outside, so water doesn't move either way. They feed off whatever organic material drifts down from the sky, and they carry out a primitive kind of photosynthesis. They don't do it with chlorophyll, but with rhodopsin, the same molecule you see with, or a close relative. Well, a lawyer's working on it, and will perhaps discover that the ITAR fears are overblown.
Or not. At any rate, you can still apply to me on an individual basis to get the code if you're a "U. Don't be confused by the title referring to the "program", since the report is not about software. The report is a nice way of getting a pretty-detailed understanding of all the different hardware Raytheon produced for the program, including all the AGCs, DSKYs, and associated ground-support equipment, which is pretty hard to get piecemeal from other documentation.
I'm sure there's nothing in the diagram that you can't get already from the many DSKY engineering drawings we have, but it may be useful for those of you who have been working on constructing your own DSKYs. Or at least, that's the conclusion I've come to, and until there's some reasonable independent review of the code, I fear that my inferences are the only ones that count. Hopefully I'll eventually turn out to be wrong.
When I say it's incomplete, I don't mean that there are pages missing from the program listing, or anything of that nature. The Flight Program listing we have is completely self-contained, and can be assembled without error No, what I mean is that the Flight Program was not the only program that needed to be loaded into LVDC core memory to get a complete working system. At the present time, I believe that the missing program would have been the Preflight Program. The Flight Program and Preflight Program would have interacted via certain addresses hard-coded into those programs. Unfortunately, right now, when the Flight Program calls routines that are supposed to reside at those addresses, there's simply nothing there, and chaos would ensue.
For example, I think that one thing the Preflight Program probably had was the self-test routine. Very handy! And very unhandy not to have it. By the same token, a self-test routine is hardly essential to the operation of the system, and it might be possible to make the Flight Program happy simply by sticking some kind of relatively-simple replacement for it at its specified hard-coded address. And all of the other problematic addresses I've seen similarly relate to code that might be painlessly worked around.
But I don't have a complete survey of all the offending missing code, and can't really make too positive a claim at this point. Time will tell how serious a problem this turns out to be. More updates to description of LVDC assembly language. There are 6 rope modules in total denoted B1 through B6 , so we now have dumps of every module plus an extra dump, which happens to be of module B3.
In fact, used together as-is, they don't form a set of ropes that works at all. Nevertheless, it's entirely possible that one may be able to create working software from them using judicious reverse engineering. We'll see! However, given that I haven't yet documented the new assembler itself, nor even put the finishing touches on it, that don't expect that the presentation of it is perfect by any means. Added a copy of the Apollo 11 Operations Checklist to the document library. This was already available at the Apollo Flight Journal , so please feel free to examine there instead.
The rate of scanning aperture-care boxes has slowed down somewhat recently due to circumstances, but is due to pick up again to a much higher rate in the near future. It turns out that my instructions for downloading a Virtual AGC "installer" for Windows may have been a tad thin in terms of explaining how to actually run the program once it has been downloaded.
So I've pepped up that explanation to make it a lot more explicit. Don Eyles has sent us a couple of Apollo 14 related documents, which are useful for information about the pad loads, as well as for deducing the locations in memory of certain variables, which may or may not assist in the current attempt of reconstructing various AGC software versions: Preliminary Apollo 14 Erasable Load Aborted Luminary simulation.
This is significant because it turns out that model also DSKY front cover added a couple of weeks ago was not the one called out for DSKY model at all, and that is what should be used. This was not just an oversight, though! The problem is that drawing simply isn't dimensioned very thoroughly, whereas is dimensioned quite thoroughly, so the hope was that would be a good substitute. Alas, it was not! Some of the dimensions specifically the width and height of openings for the indicator lamps from drawing are not compatible with the other constituent assemblies in DSKY Thus while the new models for are intended to be exact representations of the original drawing, there's not enough detail on the original drawing to insure that; so the new models contain both elements from , as well as measurements which were fortunately able to be gotten from a physical module.
Nevertheless, the potential for error remains and thus the models may need to be further adjusted over time. Rather than enumerate those documents here, I'd suggest looking for the icon on the document-library page. It should be noted that the first two of those models listed below are created from the external dimensional properties of "Specification Control Drawings" SCD. That's significant because the these assemblies were manufactured independently, and while they are really themselves assemblies, the internal characteristics of the assemblies are well, were known only to the manufacturers of the assemblies.
In other words, there are no available drawings describing their internal structures. Consequently, you can't simply 3D print them and expect that they'll do anything for you, particularly since they contain circuitry not represented by the 3D models. They'll need to be reverse engineered in order to reproduce their electrical and behavioral characteristics. The third model is also problematic, because we don't have the latest revision of its original drawing.
That's significant, because most DSKY's specify use of configuration of the part, while the most-recent drawing we have covers only up to configuration Consequently, the 3D model also conforms only to configuration rather than to the necessary , and therefore also likely requires modification. Admittedly not every single one! I probably should have mentioned too that the models being added so far are intended to precisely capture the original Apollo engineering drawings, and hence do not include any optimizations for for example 3D printing; alternate 3D models with such optimizations may be added in the future.
Also, for those who haven't stayed atop the behind-the-scenes discussions, it's perhaps useful information that the models are in STEP format, which can be imported into most 3D modeling programs, but specifically into the open-source FreeCAD modeler. I probably should summarize what those parts are, too, rather than forcing you to figure it out for yourself. Here's the complete list so far: A, rear cover E, adapter plate , digital indicator connector plate A, alarm indicator connector plate A, front cover E, front housing Mike has confidently reconstructed yet another AGC software version, this time Artemis As you may recall, Artemis 72 is the software actually flown in the Apollo 15 through 17 Command Modules.
But Artemis 71 was originally intended to do so. Artemis 72 flew instead, because of a bug fix. As with all these software reconstructions that have been appearing lately, we have no actual assembly listing of Artemis 71 to work from. Nevertheless, the clues present in the Artemis 72 assembly listing, in concert with the Artemis 71 memory-bank checksums which we have from engineering drawing , allow us not only to infer the required changes, but to verify them afterward.
Great work, Mike! Reworked a lot of the discussion of LVDC assembly-language coding , on the basis of my improved understanding of it, and particularly an explanation of the LVDC preprocessor. We've had our first submission of 3D models to our mechanical-drawing repository , for some DSKY parts. They look pretty swell to me. Thanks, Manoel da Silva Casquilho! Unfortunately, Manoel had to deal with some pretty poorly-written instructions in so far as the requirements on the 3D models, as well as practically non-existent instructions on how to actually submit them to the repository, so I've rewritten quite a lot of the section on our electro-mechanical page describing that stuff.
A handful of documents added to the library a few weeks ago have now been removed. Well, perhaps a handful and a half. For the most part, I've done this by expunging the files themselves, but leaving the hyperlinks on the document library page and striking them out thusly so that it's easy to see what has been removed. I don't actually know if it was necessary to remove them, but it has been done as a precaution.
Hint: We don't. Can you spell "time bomb waiting to go off"? I just spelled it out for you. Or perhaps, "closing the stable door after the horse has bolted"? For what it's worth, I think the documents are available on The Wayback Machine 's cache of NTRS, if you can figure out how to find them, and with luck perhaps they'll return here at some point. A bargain, to a thrifty hawk! Fortunately, anyone who can prove they're an American can naturally apply directly to me to get a copy of the transcribed software.
However, you might want to wait until it's decently proofed first and the assembler itself is ready. Clarified explanation of LVDC assembler behavior for lines having no punch-card sequence number. Made procedure for acquiring LVDC software listing from me quite a bit less painful. Mike has added yet another AGC software reconstruction, this time of the Comanche 51 source code. Comanche 51 was the program that was first targeted for the Apollo 11 Command Module, though it was Comanche 55 that eventually flew in the mission.
Reconstruction of all these intermediate AGC software versions may strike you as merely an intellectual game, which I suppose it is in some ways, but it has serious benefits as well. Having Comanche 51 rather than just Comanche 55 gets us that much closer to the goal. But we'll see what we'll see! Mike has added reconstructions of the Luminary 97 and 98 source code , following the same procedure as for the Luminary and 69 rev 2 reconstructions over the last couple of days.
There's slightly less confidence in the Luminary 98 reconstruction than in the 97 reconstruction, since back in Luminary 98 was just development software en route from 97 to 99, so its ropes were never manufactured nor its memory-bank checksums recorded. However, if Mike's Luminary 98 reconstruction were in error, his 97 reconstruction would probably be in error as well In other words, while we're less confident of the Luminary 98 reconstruction than in the 97 reconstruction, we still have a pretty high degree of confidence in it.
But in some sort of strange mental conniption, I belatedly find that I never did that on our Colossus page! I guess it's because so much data was pouring in from Don Eyles at the time that I was thinking only about the Lunar Module and not about the Command Module at all. Well, I have finally taken care of it now! Mike has added a reconstruction of the Luminary source code , following the same process as for yesterday's reconstruction of Luminary 69 rev 2.
Admittedly not quite as exciting as yesterday's reconstruction if you're only interested in software actually flown. On the other hand, it is becoming increasingly obvious that the more software versions we collect the easier it is to fill in the gaps between them, so it's nothing to be pooh-poohed by any means!
Plus, various Apollo 13 documents referenced Luminary anyway, and were never revised for , as far as we know. I've adjusted the size of the youtube video thumbnails I've embedded in the tables on the Luminary and Colossus pages, since I notice they were so big that when the windows were made smaller the text overflowed to the right and needed scrollbars to see. I can't get rid of this effect entirely, but making the thumbnails smaller mitigated it somewhat.
In other words, Cowlark is a lunar lander game which can be run on the AGC. Fun stuff, though I'm not sure programming in Cowgol actually gives you "the AGC programmer experience". As you may have noticed in looking at the Luminary and Colossus pages, it sometimes happens that when somebody gives us a listing of an AGC program, it may not be quite the software revision used in a flown mission, but since I figure we're never going to get the exact revision I end up just shrugging and saying it's good enough.
But you know, my "figuring" has been known to be wrong Such is the case with the Lunar Module software for Apollo The actual flown revision was really Luminary 69 Rev 2, whereas the printout we got from Don Eyles was simply Luminary Does Luminary 69 work when you fly a simulated Apollo 10 mission? Certainly, no problem! But it would even better to have the precise revision used, wouldn't it? That's were some of the engineering drawings I my sole contribution to this discussion!
These drawings, through , astoundingly list all of the memory-bank checksums for lots of AGC programs This information, which may seem rather pointless on the face of it, actually opens up the door for reconstructing a lot of software revisions we don't have. This is especially true for Luminary. Thus from the descriptions of the changes, we can attempt to back-port those changes as observed in later revisions of the software into earlier versions of the software and then check if those changes produced the proper memory-bank checksums!
We've done this in the past in the handful of cases where we knew the checksums of unavailable software revisions, but we never had such checksums for a large number of missions to work with before. In the case of Luminary 69 Rev 2, Mike Stewart has stepped in and reconstructed it overnight, using exactly the method described above. Thanks, Mike, once again! So while yesterday we had Apollo 10 LM software that was "close enough", today we are pretty sure we have the exact software used in the mission.
All index pages and the engineering-drawing search engine have been updated, but the assembly drilldowns have not yet. Added three new documents to the library thanks, Graham! Replaced the LVDC software sample images with higher-quality ones of the same pages. Since Aurora and Sundial were used for checkout of the LM and CM guidance systems, respectively, I infer from that Retread must also have been used for system checkouts at some point, but was then obsoleted.
As usual, the full-quality scans are at our Internet Archive site. Thanks, Don! A few more miscellaneous documents have been added to the library thanks, Graham! However, Mike has managed to find documentation that both of those assemblies held SUNDIAL E software anyway, so it hardly matters which one was installed in the computer.
Added a series of documents thanks, Graham Donald! We don't have the source code yet, since the restoration team has been so busy, but presumably Mike will churn it out for us in the reasonably-near future by comparing to similar program versions and judicious disassembly. The idea, of course, is to try and find the other half of it later. Added another couple of documents to the library , this time peripherally related to Apollo Incidentally, I was remiss yesterday in not thanking Graham Donald for sending these docs over to me.
Added a handful of notes on lunar descent, and particularly delta guidance, to the document library. I won't itemize them individually here. Just look for the icon. Or at least, a perfectly legible scan is ready, though I may make a better one later. I've actually been taking this opportunity to try out different digitizing methods, so I've scanned the thing 4 times so far.
That's because I've been very dissatisfied with the AGC listings I scanned in the past, and I wanted to perfect my method once and for all. But because I'm experimenting, the scans aren't quite as pretty yet as I'd like. Getting better, though. I kind of think it doesn't. I hope we'll eventually find out for sure that it doesn't, and I'll then be able to post the scans online.
So if you want the scanned program listing, you'll not only have to email me directly apply to me in person , but you'll also have to provide reasonable proof that you're a U. The upshot is that if it turns out ITAR does restrict access and the listing does end up somehow in foreign hands, and somebody does show up at my door with a subpoena I've also done a preliminary pass on looking through the listing and have written up all my observations and inferences about the the syntax and pseudo-operations of LVDC assembly language, as well as about the ASRAM program itself.
That's a prerequisite for getting a working LVDC assembler, which along with transcribing the listing's source code is hopefully the next step. And no, sorry, once I have transcribed the source code, it won't be freely distributable either until ITAR questions are resolved for the better. The full assembly listing of the LVDC flight program mentioned over the course of the last week or so has suddenly and unexpectedly become available. Page-image scans haven't been prepared yet, but this availability has necessitated quite a few changes in the LVDC page , as various speculations have suddenly been converted either to facts or fantasies.
Obviously, many additional relevant changes are expected in the year future. More page images of the LVDC flight program have come in. I've had to reorganize the underlying storage of these items a bit by taking the LVDC page images out of the GitHub repository. Otherwise, if new images kept coming in — something of which there's no assurance whatever — they'd begin to overwhelm it. But the change should be completely transparent to anyone looking at the website. The executive summary is "no" to the former and "maybe yes, maybe no" to the latter. Anyone with a better understanding of the legalities related to this than I am I've added still more flesh to my inferences about the LVDC assembly listings.
The description of the LVDC's STO instruction was shockingly deficient in terms of how it covers subroutine linkages — namely, it didn't , and indeed provided misleading information — so I've fixed it up. This is particularly true for the many assembly-language pseudo-ops that have appeared that we've never seen any references to before A handful of additional source-code pages from the LVDC flight program mentioned yesterday have been added.
All things considered, they've added more to my confusion than they've subtracted. It's just a few pages of trig and square root routines, but you can see from the snapshots that there's a full or at least very substantial program listing beyond just those few samples. Unfortunately, my anonymous informant does not indicate that we will be receiving the full listing, and indeed implies very strongly that we will not. So I can't you promise anything further. Which is disappointing. But the very positive takeaway is that assembly listings of the LVDC flight program do still exist I've removed some anecdotal bits of info from the LVDC page , relating to who wrote the software and how it was written, because I no longer have confidence in those anecdotes.
None of the technical info has changed. Finally finished updating all of the assembly-drilldown support for the engineering drawings added last week, and specifically for the Block II IMU. In other words, all engineering-drawing support is now up-to-date again, until I bring in a new batch of scans in a few weeks. Updated all drawing titles for the scans added yesterday, so that they correspond to the actual title blocks of the drawings rather than to abbreviated titles from the aperture-card metadata on the index pages and in the engineering-drawing search engine.
Some but not yet all assembly-drilldown support was added for the new drawings as well. The total number of engineering-drawing scans is close to 22, now. This is work in progress and not yet completed. Go figure! In particular, it consist of "modules", plugged into a backplane, with each module being either a regular analog circuit or else a "logic-flow" circuit consisting entirely of NOR gates. I suppose it's reasonable that once they had a design paradigm they'd probably stick with it, but it's still fun to see. But it's also based on a circuit-design practice that we associate only with Block I and early Block II.
For that information you have to look at an entirely separate drawing, the so-called "signal wiring" diagram. That design practice fortunately fell out of favor quickly in the AGC schematics thank heaven! As a result, I can't claim total confidence of the NOR-gate pin numbers used in the CAD transcription, due to the difficulty of proofreading them; on the up side, though, probably nobody will ever notice if I didn't get some of them quite right! Weird, since our GitHub repository is set up to do a trial build whenever a commit to it is performed which it did, and naturally, failed , and to email me about failures which it didn't, as far as I can tell.
At any rate, I've added the missing file now. But a couple of extra instructions have now been added that may do the trick. Is it a complete fix? Time will tell. At any rate, thanks to Gavin Eadie for pointing out the problems and at least part of the fix! The discussion of "signal wiring diagrams" had to be modified slightly for the case of CDU logic-flow diagrams, and I took the opportunity to make the description easier to use during the actual CAD-transcription process. Plus, the Internet Archive has finally finished its processing of drawing-box , so all of the hyperlinks to the drawings should now be working.
Unfortunately, the so-called "derive" operation that the Internet Archive uses to process these drawings has not yet completed, so hyperlinks into the latter portion of aperture-card box may not yet be functional. Links into box , on the other hand, are okay. Hopefully it won't take too much longer for the hyperlinks in box to become available. At any rate, at last count the collection of engineering-drawing scans stands at about Processing not completed yet at archive. We have been given a version of the AGC software that we didn't previously have!
Rather, the AGC-restoration project which you may have gotten wind of was allowed to borrow core-rope modules containing RETREAD 50 from the Computer History Museum, thus allowing them to obtain a dump of the ropes, and for good measure regenerating the source code for it. And we're the beneficiaries! You'll see that a link to it now appears at the bottom right of the banner across the top of all our pages. It's not quite complete yet, but feel free to check it out! Added various more Grumman LM drawings to the miscellaneous drawing index page.
I'm almost up-to-date with all of them, but there's still a tiny bit left to do. Corrected my misspelling of Tim Good's name. It's a short name, so it seems like it would have been easy enough to get right the first time. On the other hand, that's what I said about the Block I drilldowns before, so time will tell.
Some of the textual formatting the engineering-drawing search engine does in showing its results has been pepped up some of the new types of drawing numbers like Grumman and MIL. I mean, really, who would suspect that something called a "cover" or a "plate" is really an assembly? I ask you. I never even bothered to look at them.
So I've made a tentative new beginning with some updates to the drilldowns, but there's a long way to go. Check them out! One drawback with them is that while each drawing calls out the drawings for its sub-assemblies, it does so only by drawing number and no drawing name. Furthermore, the drawings themselves have only numbers in their title blocks, and have no actual titles. So I can't personally tell you what most of the assemblies are. Anyone who wants to offer up a solution to this conundrum, please do so, since it will make figuring out these assemblies quite difficult!
Next batch Partial update with respect to the completion of scans for aperture-card box and the beginning of box Added electrical CAD transcriptions for drawings A and , though stupidly on my part it turns out that I was confused and didn't realize that the latter isn't actually used in any of the major assemblies I'm providing drilldowns for.
I was unable fill in the Apollo 1 engineering drawings on the Colossus page, because with the current information there's no way to narrow it down to less than a half-dozen or so configurations. Perhaps after more revisions of the Block I drawings are scanned, I'll be able to narrow it down a lot further. I realize I've been somewhat lax about linking in relevant engineering drawings on some of the web pages that could actually benefit from them, in particular the Block I and yaDSKY pages , so I've fixed up those pages somewhat.
In some roundabout fashion, that also rubbed my nose in a couple of DSKY assemblies I forgot to provide enough info to drill down, so I've fixed them as well. Comments have also been added to the yaDSKY page concerning using the engineering drawings for very accurate recreations of DSKY physical dimensions, coloring, brightness, and so on. Gene Dorr thanks, Gene! Lots of new mil-specs related to visual DSKY authenticity have been provided as well. Well, that's how these things go, I suppose. Even in spite of that I'd say the drilldowns are now probably pretty reliable with respect to the engineering drawings we've been able to collect so far, and hopefully whatever remaining problems there are won't cause too much pain.
I've chosen to go ahead and simply remove the old manually-created drilldowns Both the old and new drilldowns had some errors with respect to each other, but neither seemed to be obviously better in that respect. It will be some time before I'm able to fully debug the new drilldown.
I haven't made many changes the last couple of weeks because I've been drastically revamping the way the electro-mechanical page displays the hierarchy of engineering drawings. I won't bore you with details, except to say that generation of this hierarchical representation is now automated, whereas before it was entirely manual, and that this will have and already does have tremendous advantages. There is still a lot of stuff to check and presumably fix! Nevertheless, I've decided to take it live rather than to keep dragging my feet on it.
The older, manually-generated presentation continues to be provided as a fallback, and will remain until the new presentation firms up a bit. The presentation-generation software may also be useful to some users, particularly if they need to have part-count data, since the software outputs JSON in addition to HTML.
Moreover, there's a comparison program that can compare two different assemblies, given their JSON. The new representation appears to have a lot more missing drawings in it than the old one does, but that's a bit misleading. Naturally, they'll never fill in completely. Hopefully those problems are fixed now, but there is still work to be done on checking the CM portion of the table. Additionally, though, it has been determined that all of the Block II AGC part numbers previously missing from the table due to a lack of drawings are really related to parts with available drawings via external changes to the AGC rather than internal ones.
This has provided the opportunity to add drilldowns for all of those previously-missing part numbers as well A side effect of these problems was that on the yaDSKY page of the website , the mission-by-mission arrangements of the DSKY indicator lamps and their colors that I posted yesterday also had errors, because they were based on the wrong DSKY part numbers. That has been fixed, with the result not too surprisingly that the Apollo 12 LM did have the same indicator lamp arrangement as the other missions, rather than a different one as I claimed yesterday, and Apollo 5 did as well.
This issue with Apollo 5 is actually slightly interesting, in that it turns out there were engineering drawings both for the configurations MIT delivered to NASA and separate engineering drawings for those NASA actually installed in the spacecraft. That distinction, along with some other subtleties, escaped me when creating the drilldown table. Who knew? Well, obviously, a lot of people other than me!
There are changes like that across the board, though only this one involved a change in the DSKY's lamps. Just one more reason to be careful, I suppose. The approaching 50th anniversary of Apollo 11 has sparked interest from various writers, and in reviewing some of our online materials so as not to make a complete fool of myself when talking to them, I can't help but notice various stuff that is out of date on the website.
Hopefully I've been able to make a dent in those, though I'm sure I haven't caught everything. Speaking of which, I had apparently forgotten to make any comments here about the new article by Brian Hayes in American Scientist magazine, "Moonshot Computing". In particular, Virtual AGC gets a short section of it's own. But size, I've heard, isn't everything It's a terrific article! On the yaDSKY page , the mission-by-mission arrangements of the indicator lamps and their colors were previously speculative. But by navigating through our recently-created engineering-drawing tree , I was able to fill them in for every mission.
It turns out there had been errors in the DSKY indicator lamps for Apollo 12 and 17, and that I had never gotten around to specifying the colors at all. I haven't actually made any changes to the software related to this fix, but I'll get around to it at some point. See also the renderings of the CAD as image files. But wait , you say, didn't you just add a different drawing A yesterday and say exactly the same thing about it?!!! Why yes, I did, thank you for noticing.
DSKY is one of only a handful of cases I've encountered in which there's an inconsistency in its drawing tree as to which schematic is applicable. The indicator driver module assembly for DSKY calls out schematic drawing , whereas the relay circuit assembly of that selfsame indicator driver module assembly calls out schematic drawing instead.
The two schematics are almost, but not quite, identical. Unfortunately there's no way to know for certain which is which with the information we have at present. Often in this case, we'd resort to looking at AC Electronics document ND, but it is also inconsistent, calling out schematic in some places, but showing circuitry from in others. Nevertheless, there are quite a few circumstantial reasons to believe that is the correct one You can read all of my reasoning on that, in my usual boring detail, on any of the DSKY drawing-tree pages.
Back when I originally did the engineering-drawing drill-downs for the various AGC and DSKY models that are listed on the electro-mechanical page , there were a number of drill-downs I couldn't complete, due to missing drawings. Well, there are still missing drawings, but in the meantime we've acquired lots and lot more scans than before, so it should be possible to fill in some of those gaps.
While it's still early in the process of filling in the gaps, here are some of the assemblies whose drill-downs have been addressed so far: AGC model xx oscillator module, B7. AGC model xx erasable driver module, B9-B AGC model xx rope driver module BB DSKY model keyboard module D8. DSKY model Chapter 4 will tell you everything you want to know, I would suppose, about TDRR's, and will help to explain the TDDR numbers that pepper the revision blocks in the Apollo engineering drawings.
Unlike my normal practice, I took some liberties with this one, in that the latest revision of the original drawing we have is "A", but it is missing its 2nd sheet the bill of materials. I therefore transcribed sheet 1 from the original A, but I transcribed sheet 2 from the original , thus producing a hybrid revision that I call "A".
I've compared the resistor, capacitor, and inductor values between the two sheets to insure there are no obvious revision mismatches between the two sheets, but there's no way to detect incorrect part numbers for things like diodes and transistors. Not that it matters too much, since you probably can't get those diodes or transistors any longer, but I still don't like it.
More fixes to the master engineering-drawing index and search engine. At any rate, I've created a little python program to track down certain types of obvious problems in the drawing indices, and I've been fixing those. Mostly they've just been trivial things like missing commas that don't make any difference, but it did manage to find and fix drawing titles that were previously completely wrong , so I'm happy! I'm sure there are still other errors that I haven't been able to find yet that will only be detected over the course of time.
I only hope I didn't break the search engine in the process I also found and fixed a number of boo-boos related to module B8 in the existing html files and drawing search-engine. Hartmuth Gutsche tells me that the Apollo online digital archive of the University of Alabama at Huntsville , having apparently been offline for a couple of years, has returned from whatever limbo it may have been in.
It contains around a thousand documents. I've leafed through all of them and pulled down 40 or so for our own digital library page just in case the UAH site decides to disappear again. You can find them in our library by looking for the icon. As you might imagine, though, given that almost all of this stuff came from Marshall Space Flight Center, most of the UAH documents relate to the big rocket, and mostly have little direct relevance to what's going on here at Virtual AGC. Thymo van Beers sent me a list of various boo-boos in my own AGC developer documentation that need to be fixed, and after lazily sitting on that list for a while — a couple of months, it looks like — I've finally gotten around to incorporating his suggestions.
Thanks, Thymo! The titles in the box index and in the drawing search engine and thus all available engineering drawings now again correspond to those given in the drawing title blocks rather than in the aperture-card metadata. The engineering-drawing search engine has been updated to include the new scans. However, the titles shown in the index for box or in the search engine are still the character abbreviated names from the aperture-card metadata, rather than the full ones from the drawings' actual title blocks.
So that's something I'll still want to fix up, hopefully in the near future. Updated the discussion of aperture cards in the FAQ. Added engineering-drawing index pages for aperture-card boxes and , and updated the page for box to include the previously-unscanned final half of the box. The changes are completely preliminary, and probably error-ridden, since although I have all of the scanned drawings in hand, I haven't posted them online yet. Somewhat pepped up the engineering-drawing search page I added yesterday, so that the search results have much more intuitively obvious search titles and URLs.
Of course, as always on this site, I make no pretense that " more intuitively obvious" is the same as merely "intuitively obvious", and in fact as I recall being taught in school, I should probably be saying something like "less intuitively unobvious". But you get the idea. Basically, you can enter a drawing number or a search term for the drawing titles, and get back a list of links directly to the individual scans. It's not perfect, but it holds the promise of being a lot more convenient that the method we've had so far of just browsing around on a selection of overlapping drawing-index pages until you find what you want.
Check it out! So I created a little program which I cleverly call "eelint" to locate such problems in the schematic files, after which I then went through and "fixed" all of them. I also reran ERC electrical rule check , netlist generation, and image rendering on the schematics I fixed, just to make sure I didn't break stuff in the process of fixing it. I ran into the slight problem that KiCad ERC had itself broken in the meantime, so I had to wait a few days for a kind KiCad developer to make it work for me again.
On the plus side, though, KiCad's ERC capability once it was working again had advanced somewhat since I had originally run it on these schematics, so it also found a handful of actual electrical problems for me that I was able to fix. Thus the exercise wasn't entirely pointless. For anyone unlucky enough to have hardcoded some links or shortcuts to the PNG files in our rendered CAD folder , I'm pretty sure that I ended up changing the names of a few of those files, so you might want to check your links. My apologies for that.
Revisions "-" and "A" for AGC differ only in the backplane signal for connector pin Revisions "-" and "A" for AGC differ only in the backplane signal for the inputs and outputs of gate are no-connects on the former but not the latter. There's no electrical difference from A for AGC Differs from A for AGC only in the backplane signal used for connector pin However, this is a change only on the backplane wiring and not within the module itself, so it is not an electrical change within the module.
The miscellaneous engineering-drawing index had been formatted fine for the situation in which it was the only drawing index, but has become inconsistently formatted with respect to what are becoming the main drawing index tables for aperture card boxes , , , etc. I have reformatted it to be consistent with those other index tables. This is really less significant for a user of the website and more significant for the situation I'm in, of needing to cut-and-paste, merge, and sort to create a master index table that doesn't explicitly appear on the website There's also a place there for storing 2D CAD transcriptions of scans of the original Project Apollo mechanical drawings, but people have expressed so little interest in that compared to interest in 3D models that we'll probably be able to count them on the fingers of one toe.
Because of teething difficulties at the beginning of this process of scanning entire boxes of aperture cards, there are several instances in type 02 documents in which page 18 was misinterpreted as page 1, and thus the page 18 scan overwrote the page 1 scan; similarly, in which page 28 overwrote page 2 and page 38 overwrote page 3. This has been fixed in the Box , Box , and Box indices.
I hope. There are also related cases in which multiple microfilms of the same drawing appear in the aperture-card boxes, but only once in our collection due to overwriting of files of the same name; this will be eliminated in future boxes i. Fixed up the currently partial index for aperture-card Box the full titles of the drawings. As some sort of asinine tribute to the sickening power of cut-and-paste for evil, I had apparently titled drawings through in Box as "signal wiring diagrams", when they are really "logic flow diagrams".
That's fixed. On the various engineering-drawing index pages, which usually provide links to our Internet Archive site for the individual drawing scans, there are warnings that using the Internet Archive's "save image as" function will usually give you an inferior image quality. However, I've found much better workarounds for that problem than when I originally wrote the warning, so I've modified those pages to give better advice about the workarounds.
I module A5 electrical schematics. For the pages used to provide indices for the drawings scanned from NARA SW aperture-card Box and Box , I've replaced the abbreviated, error-laden drawing titles originally taken from the aperture-card punches with the actual titles taken from the title blocks of the drawings. I haven't had a chance yet to do that for Box , however. I've also changed the titles of the "type 02" documents Configuration and Acceptance Test Requirements documents on the Miscellaneous drawing index page to more-accurately reflect what those documents are.
The upshot is that the affected drawing-index pages now correspond better to the drawings themselves, and should thus be easier to use. So I just hope it's good enough! So far, I think it is. Ask me again if I think so 10 boxes or boxes from now. I've added a page for the scans from Box , although the box is presently incomplete due to issues with the scanner, which I hope will be resolved fairly quickly, but am unsure enough of that to post the partial contents that have already been scanned Or to put it more bluntly, the scanner is broken and needs to be repaired.
While I'm as OCD as the next guy, and sadly probably more so, it's actually quite a lot of work to provide these drilldowns. For now, I've just made the beginning steps associated with adding support for the CDUs Coupling Data Units in the not-too-distant future. The CDUs manipulate data from the spacecraft into a format in which the AGC can input it, and conversely to manipulate data output by the AGC into a form in which the spacecraft can use it. Think of it as a set of analog-to-digital and digital-to-analog converters.
In modern terms that sounds like a big "so what? Up to now, I have only been picking and choosing the drawings I thought were absolutely needed, in order to save time and effort. However, complete scans have the advantage of overlooking nothing, and of producing much-more-legible scans. The process will take years. NARA SW has boxes, nominally of "aperture cards" each, with each aperture card holding a microfilm slide of one scanned page.
So it's unclear just how many will need to be scanned in the end The first two of these complete boxes, and , have now become available. In order to keep our web-pages containing the drawing indexes from spiraling too far out of control, this has necessitated a change to the structure of the drawing indexes. Instead of a single, huge drawing-index page such as we had previously which had about entries before complete boxes started becoming available , there will now be a series of such index pages, each relatively limited in scope This is a closely related drawing to the previously-transcribed A for Block II AGC , so I corrected various bugs in the existing A transcription at the same time.
Which is good since I hadn't really proofed A very well, apparently, and can now regard it as "proofed". However, I was unable to find any differences whatever between and A, other than the fact that the latter had a different revision written in its revision block, so it's unclear to my why they felt called upon to release revision A at all. They certainly could have save me some bother if they hadn't bothered. This is a closely related drawing to for Block II AGC , so I corrected various bugs in the existing transcription at the same time.
I also noted that several of the web-pages for Block II AGC model mistakenly called out drawing due to ambiguities in the original drawings, and so fixed those pages to call out what I think is the correct drawing instead. The two implementations appear identical at a glance, but have some pretty significant differences when you start looking at the details. Unfortunately, they fall into a kind of "uncanny valley" yes, I know I'm using the term incorrectly in which they are so similar that I felt I should create by adapting the CAD for , and yet at the same time so different that I may have ended up spending more time correcting the adaptation than I would have simply by transcribing from scratch.
On the good side, I suppose, it means that when I proofed I was really doing an extra proofing of by proxy, and thus was able to see and correct errors in it that I hadn't seen in my first proofing of it. On yet a third hand, however, both of them are so complex that I won't feel too confident in either of them until I've seen a simulation of some kind. The nature of which is yet to be determined. Of course, you have to take that "all" with a grain of salt, since there's at least one known missing original drawing later-model NAV DSKY keypad which I obviously have not transcribed, and I haven't bothered with creating a schematic for the wiring that interconnects all of the DSKY modules.
But I'm pronouncing it "done" anway. It is unclear whether or not it applies to later models, because we don't presently have the drawing of the parent assembly that would tell us whether or not it does. For some reason, even though we acquired the basic Block I electrical schematics and document ND last year , it never occurred to me to update the Block I page with little details like that.
I've just been spending so much effort acquiring engineering drawings and doing CAD transcriptions that it slipped my mind. Time sure flies. It's worth noting that document ND does have schematics in it for modules D17 and D18 , which presumably do represent the final models of the DSKYs. I've not compared E and D in detail to the schematics in ND, though a superficial comparison does show that our schematics for D17 are definitely not the final form of the design though D18 may be.
This power-supply module appeared in later Block I AGC models, but seemingly not in the early models. Alas, there's really no good way to point out which ones these are, so I'd just suggest doing a numerical or textual search to see if anything you're looking for is there.
This turned out to be a bit trickier than usual because of a conundrum I ran into in the process, namely that the connector pins in the schematic are numbered in an impossible way. And having no idea what that meant, it brought me to a screeching halt, mid-transcription. I was tempted to just call it all a mistake on the original engineer's part, and renumber the connector pins as I liked in the transcribed CAD.
But that strategy was a bit tricky to rationalize, since the original drawing was at revision "F" and thus had already been through multiple revisions without this problem if it was one! Not only that, but the partial schematics that had been redrawn in AC Electronics document ND agreed with the impossible numbering in the schematic, to the extent that ND deigned to provide those kind of details. So what was happening? It was maddening! Had the spacetime continuum become not merely warped, but completely bent?
Was it a sign at last that those fakers back in the 60's had slipped up, and I finally had the evidence in hand to out the whole fraudulent "moon landing" hoax as a public disgrace? Had I, indeed, finally slipped into madness or senility and needed to be carted away to an institution of some appropriate flavor where I would only be fed soft foods in perpetuity and given pills in little paper cups to be swallowed under the watchful eyes of white-coated people?
Fortunately, no. I asked for help in resolving the problem, and as it often turns out in these situations, Mike Stewart thanks, Mike! Thus the pin numbering for module B11 is the opposite of that for module B10, even though the two are physically identical. This entirely resolves the paradox. And that, children, is how my sanity, the integrity of the Project Apollo, and indeed the entire structure of spacetime, were saved on this day, the Nones of March, in the year of our Lord or not, if you disagree !
The modules in question are basically all of the analog "B" modules as opposed to the digital "A" modules. What this nonsense statement means is that the reference designators have been corrected to hopefully agree with those physically marked on the original modules, as opposed to using many reference designators arbitrarily assigned by the KiCad program. If that still sounds completely opaque Suffice it to say that it's a fix for an inconsistency with respect to the original design that has been bugging me for months and months, so I'm glad that it has finally been taken care of.
Particularly useful was a much newer revision of drawing the index of LM guidance systems than we had had before, because this later revision removes all of the guesswork and even some literal TBDs about the flight models of the LM AGC and DSKY that had previously infested the electro-mechanical page. The fact that it was almost identical to yesterday's drawing E only circuits an differing a bit, I think sped up the transcription process considerably.
Note that this is for the early Block I AGC models and only, whereas the later models and use a different drawing for module B31 that I haven't transcribed yet. Like all of the analog modules transcribed so far that are based on reusable hierarchical circuit blocks, I haven't yet adjusted the reference designators in the child circuit blocks to correspond to those shown on the associated insulator drawings. When I get around to that, there will be a script to do the job in an automated fashion.
For now, though, that means that those reference designators on the child sheets have been chosen arbitrarily by KiCad. However, in the PNG renderings of the CAD files, they show up as identical to those shown on the original drawings, and you have to actually edit those components in KiCad to find out the actual reference designators used in the netlists. There is also a folder of visual renderings of those CAD files as images.
Specifically, these are transcriptions of drawings B, G, and portions of A. The circuitry for later Block I AGC models , were from a different drawing which has not yet been transcribed. Specifically, these are transcriptions of drawings C, B, and portions of A. This happens to be the last of the Block I AGC logic modules as opposed to analog and interface modules — i.