Here is a Q&A interview with me in the LA Times, to which I link only reluctantly, as somehow they managed to take a picture that makes me look like I’m wearing a bad toupee. And a halo! So that’s a mixed bag.
The interview was spurred by the recent Scientific American article on the arrow of time, and most of the questions are pretty straightforward queries about entropy and cosmology. But at the end we veer into matters theological:
Does God exist in a multiverse?
I don’t want to give advice to people about their religious beliefs, but I do think that it’s not smart to bet against the power of science to figure out the natural world. It used to be, a thousand years ago, that if you wanted to explain why the moon moved through the sky, you needed to invoke God.
And then Galileo and Newton came along and realized that there was conservation of momentum, so things tend to keep moving.
Nowadays people say, “Well, you certainly can’t explain the creation of the universe without invoking God,” and I want to say, “Don’t bet against it.”
I’m not really surprised that people bring up God when asking about cosmology; the subjects are related, like it or not. But I really do want to separate out the science from the religion, so in the context of an interview about physics I’m reluctant to talk about the existence of God, and I haven’t really perfected an answer when the subject comes up.
Anyone who reads the blog might be surprised to hear that I don’t want to give people advice about their religious beliefs — I do it all the time! But context is crucial. This is our blog, and we write about whatever we’re interested in, and nobody is forced to read it. Likewise, if I’m invited to speak or write specifically about the subject of religion, I’m happy to be perfectly honest about my views. But in a context where the explicit subject is supposed to be science, I would rather not bring up God at all; not because I’m reluctant to say what I believe, but because it gives a false impression of how scientists actually think about science. God just doesn’t come up in the everyday activities of a working cosmologist.
This was the second recent incident when I was prodded into talking about atheism when I would have liked to have stuck with physics. At my talk in St. Louis in front of the American Astronomical Society, I was introduced by John Huchra, the incoming AAS president. He had stumbled across “Why (Almost All) Cosmologists Are Atheists,” and insisted that I tell everyone why. So I gave a version of the above argument, presumably in an equally clumsy fashion: whether or not you choose to be religious, it’s a bad idea to base your belief on natural theology (reasoning towards God from evidence in the physical universe), as science has a way of swooping in and explaining things that had previously been judged inexplicable by purely natural means.
And I think that’s very true, but I think something stronger as well: that claims about God can be separated into two classes — (1) those that are meaningless, and (2) those that can be judged by standard criteria for evaluating scientific claims, and come up wanting. But it’s an argument I just don’t want to force on an audience that came for some science. After all, there are plenty of claims that I think are true, but I don’t feel an urgent need to insist on every single one of them in every imaginable venue.
For example: with the acquisition of a reliable low-post presence in the form of Elton Brand, the Sixers will be challenging for the Eastern Conference title this year and for the foreseeable future. Undoubtedly true, and an important fact about the universe that everyone should really appreciate, but not something I’ll be bringing up at my next physics seminar.
Q1: I guess that depends on your definitions. Mine were that a disconnected part of space counts as a “baby universe”; this is pretty standard in the field, actually. There would be some event in spacetime where the baby pinched off from the parent universe.
Q2: See here.
Q3: No, I wouldn’t assume that. It might be a reasonable starting point, but we should keep an open mind.
Sean, Thanks for the reply. Some more questions:
Q1. What event in space-time would cause a baby universe to “pinch off” from the parent? What would cause such an event? How would one then physically differentiate between the two universes?
Q2. If the baby universe has been part of the parent, why would one think that time would then be allowed to move backward, while all other laws of physics are presumably the same.
Q3. Is this baby universe hypothesis the only “reasonable” explanation for Time’s Arrow?
Q4. Is the reason the entropy could not have been low at the Big Bang because this was when the (parent) universe was very chaotic and random and therefore at a very high entropy state?
Thanks, Larry
Larry Goenka:
Q1. How can you define another “baby universe”? I thought by definition, the universe was infinite, and so this is an inherent contradiction. Where would the physical “boundary” between our universe and this “baby universe” occur?
——————–
I can think of one simple model which might help visualize this. There is a construction in complex variables call Riemann sheets. A complex plane with some function that is multiply valued around a pole after a 2-pi rotation around the plane “jumps” to another complex plane. This jump is called a branch cut. Then on the second complex plane the function upon a 2-pi rotation jumps to a third one and so forth. These complex planes are infinite in two dimensions, but there are an infinite number of these. One might think of an infinite stack of CD on a rack, but where the radius of these disks “goes to infinity.”
These planes are connected by this branch cut, which serves in a sense as something similar to a singularity. In fact these occur with a path around a singularity. So we might think of these planes as connected to each other through these singularities. In a more complicated situation such as cosmologies these universe are connected by singularities, such as black hole interiors and the initial singularity of a cosmology. We then of course have to throw quantum mechanics into the gemish so these singularities are in some ways associated with amplitudes for spacetimes and fields. Further, all of these singularities might in fact be the same singularity, but with different quantum amplitudes we observe in each specific instance that obtains, whether that is a black hole, the big bang or maybe a quantum fluctuation of spacetime.
Lawrence B. Crowell
Hi John,
My current email, which Sean has, is samacox@comcast.net. I made a brief reply to your note and saw it was not on the thread…but no big deal. I was just basically agreeing with your feelings about momentum. I already said my piece about diety, which of course is the subject here…
The thread continues to be interesting…
“It’s surprising, the number of things God has seen fit to outsource to mathematics.”
Lawrence Cromwell, Thanks for the explanation. Some questions:
Q1. Is it fair to use complex variable theory to represent physical space? Should we also be describing the laws of physics in complex variables?
Q2. A branch cut is perhaps more like a discontinuity rather than a singularity?
Q3. One can have many multi-valued functions in complex variable theory. But this has no relationship to the real world. Why would you believe that this model would apply to explain multi-verses?
Q4. What would be an example of multiply-connected planes in real life? How can one assume that laws of physics are somewhat arbitrarily transferred to such planes?
Q4. What physical event would cause such planes to be formed and connected?
Thanks, Larry
Sam,
Since you did read it, I’ll let it slide. Like everything else, our thoughts and expressions end up fading away fast enough anyway.
The issue of deity, I suppose, is how we deal with that.
Hi John,
The SR, GR and QM universe is so logically counterintuitive, it seems almost anythng could be true. Intuition is important in conceptualizing, of course, but relying on intuition, or worse, common sense, can be like building ones house on the sand!
By the way, everything you say and do…your thoughts and expressions, are important in a determinstic universe. What you write, you literally write “in stone”. What we believe may be inconsistent- or consistent- with the nature of reality, but somehow it has a place in the overall process of discovery.
I’m reminded of the really weird ideas of Sir Isaac Newton on religion, and the strange ideas of Hoyle and Dirac. Their strange ideas were just a part of their being human. Everybody, including non-scientists, has strange ideas. In a way, we “brainstorm” our way through life! Our life makes sense to us, at our frame of reference, but to others we seem, at least- different! I’m reminded of the old Pennsylvania Dutch saying: “I think everybody is crazy but me and thee…and sometimes I wonder about thee!”
Sam,
LOL. We all feel the need to push the envelope, without popping it. Problem is, eventually it does pop and we are continually picking up the pieces and trying figure out how they went together, if they ever did go together. As the old saying goes; Open a can of worms and you need a bigger can to get them back in. It’s all about the journey, because there is no destination.
To Larry Goenka:
A1: I wrote that more as a way of analogy. However, one can work general relativity with complex variables or higher up with quaternions. In a more direct way complex variables play a central role in quantum mechanics.
A2: The branch cut is a discontinuity associated usually with the integration of a function around a pole.
A3: This is a subtle issue. If you look at the 1984 paper by Hawking & Hartle they compute the amplitude for a transition to a deSitter space using complex variables. They do some pretty ornate integrations by “skating on the complex plane.” So behind the scenes complex variables do play a role, particularly when quantum mechanics is thrown into the mix.
A4: We don’t sense imaginary quantities directly, but we can infer them. A wheel rolling on a flat surface might be one analogue of this, where with every 2-pi rotation it marks out an equal length. In electronically modulated music where there is a phase shift in a note is close to an example. Another is a note where the harmonics which make it up are modulated. This gives the auditory perception of an sequence of notes ascending a scale, but it never really does. It is an acoustical analogue of the Escher drawing of the cyclical waterfall or monks climbing a staircase that closes on itself. The illusion is an artifact of projecting down to two dimensions, and we know that there must be something similar to a branch cut which creates a stack of these staircases linked together to make sense in three dimensions. In such projections there is a “blow up of a point” which plays a role similar to a singularity.
These waves are classical waves, though mathematically we often write them according to complex variables. The analyst then does a “take the real part” at the end. Quantum waves are complex valued, but observable aspects of QM are determined by the modulus square of these wave functions.
A5: The model is really purely mathematical. If it has some applicability to physics it is used.
Lawrence B. Crowell
Lawrence Crowell:
Appreciate the clarifications, thanks.
The interesting thing about the explanation for Time’s Arrow is that it points to bizarre constructs such as other universes and time moving backward (all clearly well beyond what we see and observe in this universe). Similarly, String Theory points to ELEVEN dimensions and parallel universes.
To me, this leaves the door wide open for a Spiritual dimension to our existence.
Sam,
Actually it’s not counterintuitive. The intellectual mind is a linear narrative, so describing time as a linear dimension is profoundly intuitive. In fact, it is Edgar Allen Poe, the narrativist, who is given credit for first proposing space and ‘duration’ are the same effect. The primary artifacts of our collective inquiry, from the Bible to Big Bang Theory, are build on this beginning to end construct. So saying it’s all ‘written in stone’ is a logical conclusion, but doesn’t this quantum decoherence across time contradict the principle that energy is neither lost, necessarily to the past, or gained, necessarily from the future?
The basic principle of relativity is that neither the point of reference, or the frame of reference is absolute, but that they move relative to one another. The scenery moves past you, as you move through it. But somehow it becomes my hobby horse when I try applying this very basic principle to the apparent dimension of time and observe that events go from being in the future to being in the past, as the content of this dimension goes from past to future, yet it is perfectly logical to propose multiple universes in order to explain this one.
So, yes, I do wonder who is crazy.
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