Quantum Mechanics, Onions, and a Theory of Everything | Astrophysicist Lawrence Krauss| Big Think

Well, common sense is useful for certain things. And of course, from an evolutionary perspective, common sense arose to stop us from being eaten by lions on the Savannah, but not to understand quantum mechanics. There's no sense in which our brains, the early evolution of our brains, needed to know anything about quantum mechanics or relativity.

And what's amazing is that nevertheless, those brains that arose to solve human problems on everyday scales have allowed us to explore the universe on scales that are quite different. And scales where everything that we think is sensible goes away, on quantum mechanical scales where particles can be doing many things at the same time, or when you're moving very fast and your perception of time can change compared to mine.

And what we've learned, of course, using those principles going beyond common sense, is that the universe, our myopic views of the universe are just that: they’re myopic. The universe at its fundamental scales looks quite different. And in fact, I begin my new book with one of my favorite allegories: Plato's allegory of the cave, where he likens our existence to people trapped in a cave, being forced to look at the shadows of reality from the light cast behind them on a wall.

And he said the job of a scientist, essentially, is to interpret those shadows to understand the reality underneath. And when we look at the universe around us, we're seeing the shadows of reality. And what we've been able to do is peer underneath to discover the real world, which is really quite different.

And just as for those individuals, their common sense would tell them that the world is two-dimensional because all they see is the projection of reality, we, for us, our common sense tells us that the world is three-dimensional, but we've learned, in fact, that the universe isn’t; it's at least four-dimensional: the three dimensions of space and one dimension of time that are tied together, yielding a reality at its basis, which is really quite different from that which we experience.

That's just one example of the many ways we've been able to dive down underneath this fabric that's shielding the real world underneath. And the fabric is what perhaps our common sense is based to understand, and what's underneath—it’s not too surprising that it doesn't seem sensible because it describes realms of the universe that we literally did not evolve to originally understand.

And as I say, it's an amazingly fortuitous accident that our brains evolved so we could understand those regions as well. The question arises, naturally, once we understand at a fundamental level that the universe looks quite different than we perceive it to be: whether what we're now discovering is truly fundamental or whether we dive down deeper and the universe will look different still?

Richard Feynman argued that way. He basically said, “Will we have a theory of everything, or is the universe like an onion and you peel back one layer and there's another layer, and it's an infinite number of layers of onions (or turtles all the way down depending upon how you want to describe it)?”

The answer is: we don't know. We don't know if there is an ultimate theory of everything. But it really doesn't matter in many ways. What we want to understand the universe better today than we did yesterday. We want to expand our understanding, and that's what we try and do.

And science often works by baby steps. One of the things I describe in my book is the long series of baby steps that took us to where we are now, from our understanding of the universe on the scales that we see in this room to the fundamental scales. There were many steps that took us there.

And the process is exciting, and every new step of discovery is exciting, and every time we make a new discovery there are more questions than there are answers. And so there's guaranteed job security, it seems to me, for scientists, and I don't have any great expectations that there is a theory of everything or a need to know that theory. To me, the questioning and the search is as exciting in some sense as the answer.