In each issue of Nautilus, we shine a spotlight on one “Ingenious” scientist whose work makes us reconsider our world and ourselves. The Ingenious for our first issue, “What Makes You So Special,” is Columbia University astrophysicist Caleb Scharf, who contributed an essay about our place in the universe and talked about his life and thoughts at length in a video interview. The video segment below focuses specifically on the question of extraterrestrial life and what it has to do with us. Below the video clip is a transcript.
(Also see our preview issue, in which Ingenious Peter Ward told the amazing story of how his life intertwined with the cephalopod called nautilus.)
Is there other life in the universe?
I think the discovery of so many planets out there and so many diverse planetary systems has really rejuvenated the idea that there is life out there somewhere, and it’s rejuvenated interest in the question of, well, how complex does that life get? Is there other intelligent life out there? And for many people it’s created a sense of optimism and absolutely created the sense that there is now such a playing field to look at, that surely there has to be something out there…
We simply don’t yet understand the specific nature of many of these planets, we don’t know exactly what the surface environments are, what the history of these worlds is. We also still have a big question about our own origins, the origins of life on Earth, the interlink nature of life in our planetary environment across billion of years. We don’t quite know how all of that works out. The fascinating thing I think for many of us, and certainly for me, is that the very existence of other planets, other stars, other planetary systems, is we now have the opportunity to place ourselves in some sort of context.
How is human life related to the universe?
All life on this planet as we know of comes from essentially the same set of building blocks. These are, if you boil it all down, it comes down to the heavy elements. And so heavy elements, this has almost become a bit of a cliché, but we are the stuff of stars. All the heavy elements in the universe, anything heavier than helium and hydrogen, have been formed in the interior of massive stars that are now dead. They’ve all exploded and they’ve given up their existence in order to spread elements out across the cosmos, which eventually end up coagulating into planets and coagulating into creatures like us. So the atoms of carbon and oxygen and iron in your body, in my body, were once a million miles down inside the core of a long dead star. So in that sense we’re very much the detritus of generations of stars.
And furthermore these elements didn’t just miraculously appear on the surface of our planet, they were an integral piece of formation of the earth. And so some of the atoms in my body and your body undoubtedly rained down as our planet was forming as pieces of cometary material, pieces of asteroids, and it could’ve taken place over a quite extended period, long after the sort of young Earth was present. And so it’s kind of fascinating to think that different pieces of our bodies have had such radically different pathways through the universe, yet they all ultimately come from the deep interior of stars. And that is the result of deep physics, the physics of fusion, the physics at an atomic and sub-atomic scale.
What kind of life could be out there?
The chemistry of the universe is carbon chemistry; it absolutely is. No matter where you look, you see carbon molecules. That’s because of the nature of the carbon atom. Now of course that rests on deeper fundamental physics, but if you ignore that for the time being, it is what it is. And carbon atoms form an enormous array of molecular structures, more than really anything else in the universe.
We see them in space, we see them in interstellar gas and dust, we see them in other planetary systems, other forming planetary systems and so on. We see them in the detritus in our own solar system, the meteorites that fall down on the earth and then cometary material. And there is really no obvious step or no obvious shift from that chemistry to the chemistry of life. Now we don’t know how you make the transition from this abiotic chemistry, this unliving chemistry, to what we would consider living chemistry; that’s still a big question.
How could life emerge?
For a long time, just to give you an example, people talked about the origin of life on Earth, and they talked about how improbable it seemed to be that a selection of basic atoms and molecules could somehow suddenly assemble themselves into the first self-replicating organism, or first self-replicating structure. And the argument was really a statistical one. If you looked at the permutations and combinations and the amount of time available, you simply couldn’t come up with anything plausible; it would take longer than the universe had been around for this to happen.
But that was based on an understanding of how molecules and atoms assemble and how complex structures begin to emerge out of simple rules, that was rather naive. We now know, or we now see that things emerge. Complex systems seem to just emerge from simpler underlying rules, and it’s because of the interaction not of two atoms and two molecules, but a billion. And now the fact that things emerge, you might say, well, maybe that was laid down at a deeper level, and at some levels surely it was. But that’s perhaps missing the fact that often the sum of the parts ends up being much greater than those parts!
Can complex Life Emerge Elsewhere in the Universe?
Given that we see the formation of molecules that are just a step away from things like amino acids and more complex structures throughout the universe, we see them in interstellar space, they literally form over millions of years of cold chemistry in the vacuum of space. And we detect them, and some of those molecules eventually end up being processed and put on the surface of young planets at some level, that young planets may receive a sort of starter mix of this cosmic chemistry, which appears to be all the building blocks that make life as we know it.