The Varieties of Scientific Experience: A Personal View of the Search for God

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hydrocarbon at Titan. [3] So just think of that environment. There's land; probably there's ocean. The land is covered with this organic muck that falls from the skies. There is a submarine deposit underneath this ocean of liquid ethane and methane of more of this complex stuff, and then down deep is frozen methane and frozen water and so on.

Now, that's a world worth visiting. What's happened to that stuff over the last 4.6 billion years? How far along has it gotten? How complex are the molecules there? What happens when occasionally there is an external or an internal event that heats things locally and melts some ice and makes some liquid water? Titan is a world crying out for detailed exploration, and it seems to be a planetary-scale experiment on the early steps that here on Earth led to the origin of life but there on Titan were very likely frozen, literally, at the early stages because of the general unavailability of liquid water.

Likewise, there is a very stunning range of studies-mainly in the last two decades-of interstellar organic matter: not just a multiplicity of worlds in our solar system but the cold, dark spaces between the stars are also loaded with organic molecules.

we are looking toward the center of the galaxy in the direction of the constellation Sagittarius. You can see a set of dark clouds, some quite extensive, some much smaller. It is in these giant molecular clouds that well upwards of 50 different kinds of molecules have been found, most of which are organic. And it is precisely in such dark clouds that the collapse of solar nebulae is expected to happen, and therefore the forming solar systems should be composed, in part, of complex organic matter. The conclusion is that complex organic materials are everywhere.

Now let's return to the question of the origin of life on Earth. The organic stuff could have fallen in during the formation of the Earth, or it could have been generated in situ from simpler materials on the Earth in the same way as on Titan. At the present time there is no way of assessing the relative contributions from these two sources. What seems clear is that either source would be sufficient-adequate.

The Earth formed from the collapse of lumps of matter of the sort we talked about earlier, condensing from the solar nebula. Therefore in its final stages of formation, it was collecting objects that collided at high velocity and produced a set of catastrophic events, including the melting of much of the surface. This, it turns out, was not a good environment for the origin of life, as you might have suspected. But after a while, when the final sweeping up of the debris in the solar system was more or less completed, water delivered from the outside or outgassed from the inside started forming on the surface, filling in the ancient impact craters. And a trickle of material was still falling in from space. At the same time, electrical discharges and ultraviolet light from the Sun and other energy sources produced in-

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digenous organic matter. The amount of organic matter that could have been produced in the first few hundred million years of Earth history was sufficient to have produced in the present ocean a several-percent solution of organic matter. That is just about the dilution of Knorr's chicken soup, and not all that different from the composition either. And chicken soup is widely known to be good for life. In fact, it is just this warm, dilute soup, in the words of J. B. S. Haldane, who was one of the first two people to realize that this sequence of events was likely, in which the standard scenario for the origin of life occurs.

In the laboratory -we can take molecules of water, ammonia, and methane-rather like the ones we've been talking about for Titan-and dissociate them by ultraviolet light. The fragments make a set of precursor molecules, including hydrogen cyanide, which then combine and, in water, form the amino acids. In such experiments not just the building blocks of the proteins but the building blocks of the nucleic acids are routinely produced. There is a range of subsequent experiments, in which the smaller molecular building blocks join together to form large and complex molecules.

If we look at the fossil record, we find that there is a range of evidence for microfossils dating back not just to the beginning of the Cambrian but dating back to as much as 3,500 million years ago.

Now, just think about these numbers. The Earth itself forms about 4,600 million years ago. Because of the final stages of accretion, we know that the Earth environment was not suitable for the origin of life back then. From studies of the late crater-ing on the Moon, it looks-since the Earth and the Moon were presumably in the same part of the solar system then as now- as if the Earth was not in a suitable state for the origin of life until perhaps 4,000 million years ago. So if the Earth is not appropriate to the origin of life until 4,000 million years ago and the first fossils are around 3,500 million years ago, then there are only about 500 million years for the origin of life. But those earliest fossils are by no means extremely simple organisms. They are, in fact, colonial algal stromatolites, and a great deal of evolution had to precede them. And that therefore says that the origin of life happened in significantly less than 500 million years. We don't know how much less. Six days was once a popular hypothesis. It's not excluded by these data, but at least it cannot be as long as 500 million years. It must have happened very fast. A process that happens quickly is a process that in some sense is likely. The faster it happens, the more likely it is. There is a difficulty in extrapolating from a single case; nevertheless this evidence suggests that the origin of life was in some sense easy, in some sense sitting in the laws of physics and chemistry. And if that's true, that is a very important fact for the consideration of extraterrestrial life.

There is a classic objection to this kind of argument about the origin of life. As far as I know, this objection was first posed by Pierre Lecompte du Noiiy in a 1947 book called Human Destiny and is regularly rediscovered about once every half decade. It goes something like this: Consider some biological molecules. Not all of them. We'll give the evolutionists the benefit of the doubt. Let's just take a small, simple one, not something thousands of amino acids long. Let's pick an enzyme with a hundred amino acids. That's a very modest enzyme. Now, a way to think of it is as a kind of necklace on which there are a hundred beads. There are twenty different kinds of beads, any one of which could be in any one of these positions. To reproduce the molecule precisely, you have to put all the right beads-all the right amino acids-in the molecule in the right order. If you were blindfolded while assembling a necklace from equally abundant beads, the chance of getting the right bead in the first slot is 1 chance in 20. The chance of getting the right bead in the second slot is also 1 chance in 20, so the chance of getting the right bead in the first and second slots simultaneously is 1 chance in 20². Getting the first three correct is 1 chance in 20³, and getting all hundred correct is 1 chance in 20¹⁰⁰. Well, you can see 20¹⁰⁰ is 2¹⁰⁰ x 10¹⁰⁰. And since 2¹⁰ is a thousand, which is 10³, then 2¹⁰⁰ is 10³⁰, so this is the same as 10¹³⁰. One chance in 10¹³⁰ of assembling the right molecules the first time. Ten to the hundred-thirtieth power, or 1 followed by 130 zeros, is vastly more than the total number of elementary particles in the entire universe, which is only about ten to the eightieth (10⁸⁰).

So let's imagine that every star in the universe has a planetary system like ours. Let's say one planet has oceans. Let's suppose that the oceans are just as thick as ours. Let us suppose that there is a few-percent solution of organic matter in every one of those oceans and that in every tiny volume of the ocean that has enough molecules there is an experiment happening once every microsecond to construct this particular hundred-amino- acid-long protein. So in the ocean every microsecond an enormous number of these little experiments are going on. And identical things are happening in the next star system and the next star system, filling an entire galaxy. And then not just in that galaxy but in every galaxy in the universe. It turns out that if that sequence of experiments had gone on for the entire history of the universe, you could never produce one enzyme molecule of predetermined structure. And in fact it's much worse than that.

If you did that same experiment once every Planck time, the shortest unit of time that is permissible in physics, you still couldn't generate a single hemoglobin molecule, from which many people have decided that God exists, because how else do you make these molecules? If you haven't heard this before, doesn't this seem like a pretty compelling argument? Strong argument, right? A whole universe of experiments once every Planck time. Can't beat that.