Many Universes

Great Debates
1

Quantum mechanics flawlessly describes the behavior of sub-atomic particles, however it describes them as smears, and this is at odds with what we experience.

For instance, a photon is one quanta of light. Under some circumstances, quantum mechanics says that this one photon is a rather complicated smear, occupying an enormous space. Never the less, when this photon hits a nerve cell in your eye it becomes “real”. A physicist would say that the photon’s wave function collapses at this instant. But how does the photon’s wave function decide where to collapse?

One answer to this question, known as the many universes explanation, goes back to the beginnings of quantum mechanics in the 1920’s. This explanation was favored by Neils Bhor but rejected by Einstein as being too weird.

MANY UNIVERSES EXPLANATION

The photon strikes one cell in your eye in one universe, strikes another cell in your eye in another universe, misses you in another universe. All possible scenarios are carried out somewhere because there are as many universes as there are possible outcomes.

I’ve heard this described in terms of universes being created on the spot to accomidate all possible outcomes, however in recent years physicists talk about Configuration Space. This is the space that is described by quantum mechanics where everything is a smear.

We don’t live in configuration space. We live in a place where objects are solid and well defined. However, Configuration space IS the ultimate reality. We simply live in a thread running through configuration space.

Configuration space is no more controversial than quantum mechanics because quantum mechanics describes matter in configuration space. Configuration space does exist, and if you are not blown away by that fact, then you don’t understand what I’m talking about.

Mathemeticians have long known that you can build sharp, well defined functions by combining lots of fuzzy, smooth functions. What you see around you is exactly that, a sharp, well defined world built from the enormous set of fuzzy quanta in configuration space.

2

“Fact”?

There is more than one interpretation of quantum mechanics. Some don’t include the many universes hypothesis.

3

FACT - Quantum mechanics describes matter in configuration space.

Opinion - Configuration space is “real”, whatever is meant by “real”

However - more and more people are starting to believe that configuration space is real, is the ultimate reality.

4

**Vincent Bressler wrote:

Configuration space is no more controversial than quantum mechanics because quantum mechanics describes matter in configuration space. Configuration space does exist, and if you are not blown away by that fact, then you don’t understand what I’m talking about.**

I’m not blown away by what you said and I don’t know what you’re taking about. Can you put this in simpler terms?

What is this “configuration space” ?? How do you define reality and why is this “configuration space” the ultimate reality?

Whatever you’re saying sounds interesting, but your explaination leaves a lot to be desired. I’ll admit I never took calculus in school, so please leave it out, if possible.

5

We most certainly do not live in a place where objects are solid and well defined. That’s the whole point of quantum mechanics.

Configuration space is a mathematical abstraction that originated with classical Lagrangian mechanics. Although Lagrangian mechanics ultimately led to the theory behind QM, describing physical systems in configuration space is by no means a unique feature of QM. Configuration space is just a generalization of describing systems in, e.g., Cartesian or polar coordinates.

The many universes interpretation of QM is interesting, but AFAIK it has no real value as a predictive scientific theory. You can’t even experimentally verify whether it’s true or not.

6

I agree that configuration space is a mathematical abstraction. However, I disagree that quantum probability density functions are properties of the world that we actually live in and experience. The example of the photon hitting a nerve cell is a good case in point. Quantum mechanics may say that the photon’s wave function is spread out over an area of thousands of light years. However in our world that photon either hits the nerve cell or it does not. There is a fundamental dichotomy here and the many universes interpretation is one, in my opinion rather flawed, attempt to explain what is going on.

Of course one can find many instances where quantum mechanisms is being employed in technology, like the scanning tunneling electron microscope. But look closer, if an electron “tunnels” then ultimately it has moved from point a to point b through a mid point where it can not possibly be … that’s quantum mechanics. However, what do we measure, a discrete event, either the electron tunnels or it does not.

It is not useful to say that we live in the squishy quantum mechanical world. We do not. This movement between the quantum mechanical world and our own, call it collapse of the wave function, is absolutely fundamental to understanding what is phyisical reality, and this understanding is still far beyond our mathematics.

Look at the great leaps forward in the past: Newton formulated a theory or gravity and then found the elegant mathematics that gave the theory its grounding. Einstein started by saying “what if light travels at the same speed from all perspectives” “what if there is no difference between gravity and acceleration”, the mathematics followed.

We are at the very beginning in our understanding of the relationship between configuration space and the physical reality that we exerience every day. I’m not a mathemetician, I don’t intend to spend my life working out those details, but I’m asking you, “What if configuration space is more than a mathematical abstraction? What if configuration space is the ultimate physical reality? What if the universe that we live in is one evolving set of interference patterns in configuration space?”

7

This is in response to Freyr:

Quantum mechanics says that each particle of matter is not a discrete point but a smear, a wave. However, whenever we observe that wave we see a point because the wave collapses.

We know that the wave is there because we can see evidence of it’s affects on the things around it and because we can use the quantum mechanical description of the wave to predict behaviour of the particle. In fact quantum mechanics has been astoundingly successful in this regard.

The rules that determine when a wave function collapses are bizarre. It has been experimentally determine that wave functions collapse whenever there exists the possibility that a wave/particle could be observed, irregardless of whether the particle was actually observed.

Clearly these rules about observation are built into the universe and the universe is something quite different than what we experience.

Configuration space is the space where wave functions exist and never collapse but merely react with / interfere with one another. Somehow we are confined to a relm which is but a small slice of configuration space. In effect, our universe is one particular interpretation of where all the particles that exist are at each instant, whereas configuration space is the sum of all possible interpretations, of which our universe is but one.

One other universe would initially differ from ours only in the position of a single photon. In other words, this other universe would be essentially identical to our own, but going out in time each wave function collapse in that other universe would be independent of what happened in our universe, eventually, through the myriad of purely arbitrary events that make up our history and theirs, the two histories would diverge.

Configuration space has essentially an infinite amount of space for this sort of thing.

By the way, there is a great deal of interest in quantum computation these days. A quantum computer performs parallel processing using a very large number of universes in the configuration space.

8

The “Pilot Wave” hypothesis, in which a pilot wave travels backward in time to collapse the wave function at a quantum event is an alternative theory. If I recall correctly, Von Neumann dismissed it with a proof but said proof has been found to be flawed.

I personally like the parallel universes theories but not ones that are created at every quantum event. If we live in a four spatial dimensioned multiverse (not to mention the theoretical eleven dimensioned one) there are already an infinite number of 3D universes, just like there are an infinite number of square inches piled up in a cubic inch.

What if particles somehow resonated with their corresponding particles in the other universes? In most universes, the particles are in roughly the “same spot”. In some universes, the particles, through some chance event, have been thrown half way across the universe. The particles “know” this distribution and it is reflected in our smeared interpretation until we measure the location of “our” (this universe’s) particle.

9

My understanding is that a quantum computer performs logical operations on uncollapsed wave functions in configuration space. Stated differently, a quantum computer works by coherently controlling particles across parallel universes. The answer for the quantum computation however is a real piece of information in our universe that is arrived at by collapsing these wave functions, whereupon the sea of possible outcomes is reduced to one number, the correct number for our universe.

There are some severe restrictions governing the operation of a quantum computer because it is necessary to manipulate the waves without collapsing them.

10

OK, I’m glad you clarified that. Before, you said “Configuration space does exist” was a fact, and that we should be blown away by that fact. There are few facts when it comes to the underpinnings of physical theory.

Einstein (and Infeld) said it pretty well in The Evolution of Physics: “Physicial concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. In our endeavor to understand reality we are somewhat like a man trying to understand the mechanism of a watch. He sees the face and the moving hands, even hears its ticking but he has no way of opening the case. If he is ingenious he may form some picture of the mechanism which could be responsible for all the things he observes but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism and he cannot even imagine the possibility of the meaning of such comparison.”

11

I agree that it may not be possible for anyone to prove that a particular ultimate theory of physical reality is correct. Any such theory must be consistent with what we observe, but that is not enough. The closest that we may ever come to “proving” such a theory is when we find one that reduces to mathematics with a beautiful simplicity.

However, there remains this stunning duality in that we have a very successful theory in quantum mechanics that is utterly at odds with the real universe that we are confined to. It appears that quantum mechanical entities exist in a relm that is far larger than the universe in which we are confined. Is that quantum mechanical universe, that configuration space the “ultimate reality”. That may be impossible to prove, but the mathematics of configuration space are beautiful and simple and are a completely accurate predictor of what actually happens in our little neck of that vast woods.

12

IMHO, it’s an interesting (and yes, mind-boggling) idea to be kept in our back pockets for now. Until there is evidence of its existence, there is no need to invoke it to explain our universe when Relativity & QM already do so well. Of course, Relativity & QM don’t mix when it comes to singularities, so new theories are still to be developed to explain the workings of the universe.