A Universe Of Life: Maybe Not

This vast universe surely holds plenty of worlds where life can flourish, right? Don't bet on it, says New Mexico State University physicist Slava Solomatov.

The more scientists learn about the conditions that make life possible on Earth, the more they realize how complex those factors are -- and how a relatively small change in one condition or another could have rendered the planet uninhabitable, Solomatov said.

"It's a very finely tuned system," he said. "Some of the factors are well known, but we still don't know what all the factors are."

Solomatov has a key part in a NASA-funded astrobiology research project aimed at better understanding the origin of life on Earth and the conditions in which life might be found elsewhere in the universe. The five-year, $4.9 million grant supports the work of a dozen researchers, headed by a team at the University of Washington.

The scientists come from a variety of fields, because life requires much more than water and the right mix of elements to survive and evolve into higher forms.

Solomatov's part of the project focuses on the role of plate tectonics -- the geologic process that results in the shifting of Earth's continental and oceanic plates. Only in recent years have scientists recognized the importance of plate tectonics in maintaining Earth's long-term temperature stability, through global recirculation of carbon dioxide from the planet's interior into the atmosphere, he said.

"Because carbon dioxide is a greenhouse gas, it helps to keep our planet warm," he said. "Of course, too much of it is not good, but without this cycle over the centuries the temperature would drop and you might have the 'Snowball Earth' scenario."

Plate tectonics also provides diverse geological environments, like mountains, which promote biodiversity, Solomatov said.

No other planets are known to have plate tectonics, although some may have had the feature earlier in their evolution, he said.

Whether plate tectonics might be essential to the development of higher forms of life is unknown, but Solomatov's theoretical modeling of the complex processes aims to shed light on a number of key questions, including: What planetary conditions allow for the formation of plate tectonics? Are oceans necessary for plate tectonics? When and how did plate tectonics begin on Earth?

The question of life on other planets, or even the habitability of other planets, has long captured our imagination, but we tend to be biased in our assumptions, Solomatov said.

"We think this is normal and there should be planets all around the universe like Earth," he said. "The more I work in this area, the more I realize the chances really are very slim."

It's not enough for a planet to be the right size, to have water, and to be located the right distance from a star of the right size. Without the giant planet Jupiter as a neighbor, and without our moon, Earth might not be the living planet that it is, Solomatov said.

Jupiter has protected Earth from too many cataclysmic asteroid collisions, he explained -- but on the other hand, a neighbor much larger that Jupiter would not allow formation of an Earth-like planet in the first place. Similarly, our moon is just the right size to help stabilize Earth's spin axis and, as a consequence, the Earth's climate. With a bigger moon or no moon at all, a planet similar to Earth in other respects might not sustain life.

"At the moment there are two camps of believers," Solomatov said. "One believes in the 'Rare Earth' hypothesis and the other thinks life is smart and can adapt to extreme conditions."

The "Rare Earth" hypothesis, which takes its name from a book by University of Washington scientists Peter Ward and Don Brownlee, holds that microbial life might be common in planetary systems, but advanced life is rare.

If pushed into one camp or the other, Solomatov would choose the "Rare Earth" believers.

"We don't have enough data yet but all the evidence we have now points out that the Earth is a very special place," he said. "Maybe we should take better care of our planet."

Jupiter has protected Earth from too many cataclysmic asteroid collisions, he explained -- but on the other hand, a neighbor much larger that Jupiter would not allow formation of an Earth-like planet in the first place. Similarly, our moon is just the right size to help stabilize Earth's spin axis and, as a consequence, the Earth's climate. With a bigger moon or no moon at all, a planet similar to Earth in other respects might not sustain life.
Looks like more evidence for the "anthropic principle."

I disagree. Or rather, I disagree that it's necessarily compelling evidence. It all hinges on qualifications. "a neighbor much larger that Jupiter", he says. Well, "How much larger?" I ask. Can this Jupiter-like planet be 10% larger & still be a net benefit? 1x10¹ bigger? 1x10² bigger? 1x10³ bigger? In astronomy, these numbers are always so big, it's easy to forget that the range between two numbers is often also very big - allowing for many possibilities - even though when that range gets distilled into conversational written English it sounds impressively small. Same thing with the size of the Moon, or with the ratios of subatomic particles & basic physical constants, etc.

The other, more basic problem I have with the Anthropic Principle is that it's a logical error right from the start. As we discover nature's regularities & relationships - how the world works - we naturally ask ourselves "why?". This means, "Why does it work this way instead of all the other ways I can imagine it 'could have' worked?"

The AP argument seems to be a more sophisticated sounding version of that question. But that question is invalid. Every time we study a natural phenomenon & discover why it works the way it does, we simultaneously discover why it could not have worked any other way. We discover the regularities that give rise to the regularities we seek to explain. It literally could not have worked any other way.

Here's an example: You live in a hot climate, & you have never seen what happens to water when it goes below 32^oF. I come along & tell you that water changes drastically at 32^oF. Now you start to wonder: What could water do at 32^oF? You start to list the possibilities:

The water gets colder.
The water shrinks to 1/2 its size.
The water turns color to {red|orange|yellow|green|blue|brown|purple|gray|opaque white|black}.
The water turns solid.
The water turns jiggly, like Jell-O.
The water jumps up & sings the Michigan Rag.
The water catches fire, but emits a cold instead of a hot flame.

As your imagination wanders, you go thru all possible combinations of the above "possibilities" & more, and if your imagination is big enough, you can generate an astronomical number of "possibilities" this way.

Then I show you an ice cube. Now, what are the odds that that would happen instead of something else? Well, it all depends on how big your imagination was! So in our example, the odds of it turning out this way were vanishingly small. And yet, as you learn about molecules, molecular bonds, thermal energy, & how light waves interact with molecules of different sizes, you begin to see why almost all of your possibilities were never "possible" in the first place.

Then, your curiosity piqued, you begin to wonder why the H atoms in H₂O have to stay at 110^o (?) instead of some other angle, etc. etc., & the cycle repeats - until we get to the question of why the charge of an electron is a certain ratio to the size of a graviton (or whatever). IOW, where we are today with AP.

So, IMO the wonder that AP writers express at how "fine tuned" the universe seems to be in order to produce the universe we see is nothing more than a misunderstanding of how the hypothetico-deductive reasoning process works.

(I always wanted to use the term "hypothetico-deductive" someday!)

If we stumble across ET sometime, fine, we will deal with it.

I for one hope we never encounter a civilization more advanced than we are. If they are at all militaristic and even a few hundred years more advanced than we are -- never mind millions of years more advanced -- we're goners.

I don't know about this rare earth stuff, either, having not read the book . . . But do we really know enough about life to say that advanced forms cannot evolve unless they have an environment just like earth's? I'm skeptical.

I used to think advanced life was probably abundant in the universe, but no more; the failure of the many SETI searches of the last few decades to turn up even one, argues strongly against it, IMHO.

So I'm with you, RW . . . NASA should change the focus from searching for life to exploiting and developing space near earth.

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