It seems I am quite comfortable with the idea that the Universe could happen by accident in such a way that we just happen to be here. If it were any other way we wouldn't be here and none of this would matter. Chaos is my friend.
Now, many cosmologists speculate that we live in a "multiverse," with big bangs exploding all over the cosmos, each creating its own bubble universe with its own laws of physics. And lucky for us, our bubble turned out to be life-friendly.
But if you really want to start an argument, ask a room full of physicists this question: Are the laws of physics fine-tuned to support life? Many scientists hate this idea -- what's often called 'the anthropic principle.' They suspect it's a trick to argue for a designer God. But more and more physicists point to various laws of nature that have to be calibrated just right for stars and planets to form and for life to appear. For instance, if gravity were just slightly stronger, the universe would have collapsed long before life evolved. But if gravity were a tiny bit weaker, no galaxies or stars could have formed. If the strong nuclear force had been slightly different, red giant stars would never produce the fusion needed to form heavier atoms like carbon, and the universe would be a vast, lifeless desert. Are these just happy coincidences?
This sounds like it's coming right out of science fiction. Somehow, future people can go back in time and have some role in creating the universe. It's pretty far-fetched.
It is pretty far-fetched until you stop to think that there is nothing in the laws of physics that singles out one direction of time over another. The laws of physics work forward in time and backward in time equally well. Wheeler was one of the pioneers of this underlying time symmetry in the laws of physics. So he was steeped in the fact that we shouldn't be prejudiced between past and future when it comes to causation. The particular mechanism that Wheeler had in mind has to do with quantum physics. Now, quantum physics is based on Heisenberg's uncertainty principle. In its usual formulation, it means that there's some uncertainty at a later time how an atom is going to behave. You might be able to predict the betting odds that the atom will do this or that, but you can't know for certain in advance what's going to happen. Now, this uncertainty principle works both ways in time. There's no doubt about this. If we make an observation of an atom in a certain state now, then its past is uncertain just as its future is uncertain.
But what's so hard to fathom is that this act of observation, which has been observed at the subatomic level, would affect the way matter spread right after the big bang. That sounds awfully far-fetched.
Well, it's only far-fetched if you want to think that every little observation that we perform today is somehow micromanaging the universe in the far past. What we're saying is that as we go back into the past, there are many, many quantum histories that could have led up to this point. And the existence of observers today will select a subset of those histories which will inevitably, by definition, lead to the existence of life. Now, I don't think anybody would really dispute that fact.
What I'm suggesting -- this is where things depart from the conventional view -- is that the laws of physics themselves are subject to the same quantum uncertainty. So that an observation performed today will select not only a number of histories from an infinite number of possible past histories, but will also select a subset of the laws of physics which are consistent with the emergence of life. That's the radical departure. It's not the backward-in-time aspect, which has been established by experiment. There's really no doubt that quantum mechanics opens the way to linking future with past. I'm suggesting that we extend those notions from the state of the universe to the underlying laws of physics themselves. That's the radical step, because most physicists regard the laws as God-given, imprinted on the universe, fixed and immutable. But Wheeler -- and I follow him on this -- suggested that the laws of physics are not immutable.
I love it. It validates the way I have intuitively thought about the universe most of my life. Everybody loves validation.
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