a different kind of "physics coincidence"

[Metric]

As is sometimes discussed here, there are some very interesting and very improbable-looking physics coincidences that seem to be necessary for the universe to look anything at all like ours (very small changes in fundamental laws and parameters result in a universe that looks completely different from our own). But save all that for another day -- I'd like to talk about another kind of "coincidence" that I have never heard people talk about. In fact, it may not be a coincidence at all (I haven't thought it completely through yet), but it seems to be a fun idea to toss out here for various thoughts and opinions.

The main pillars of modern physics are quantum theory, relativity, and statistical mechanics. One can think of the scale of these theories as being governed by some "fundamental" constants, h, c, G, and k (Planck's constant, speed of light, Newton's constant, and Boltzmann's constant). But note the following:

In ordinary "human scale" units,

1) h is very tiny (the most general quantum effects are hard to see)

2) c is enormous (special relativistic effects are hard to see)

3) G is tiny (general relativistic effects beyond simple Newtonian gravity are hard to see)

4) k is tiny (thermodynamics is an extremely good approximation -- large fluctuations from thermal equilibrium are essentially never seen)

Now, the interesting thing is that these points conspire to create a situation in which a huge amount of physics can be done (Newtonian physics) in which none of the fundamental "pillars" are actually taken into account! For one thing, this is why physics students start out learning Newtonian physics (it's range of applicability is huge), and for another thing, it guarantees that physics will be an amazingly subtle subject as perceived by humans -- practically all of the fundamental rules are divorced from the "human scale" of experience. It also guarantees that the "human scale" of physics is mathematically the easiest to analyze.

So, the questions of interest to me are the following:

1) Must this be the case? Is it essential for life to evolve on a scale in which the fundamental "pillars" can always be "approximated away?" (equivalently -- will every intelligence that evolves necessarily find the subject of physics to be subtle and profound?)

2) Must it be the case that "life scale" physics will always be the easiest to handle mathematically (it will always be the easiest to access experimentally, of course -- but the question of mathematical access seems subtly different to me).

[Sharkey]

Mathematical representations and the experiments to which they correspond are images of each other. It is not surprising they would develop in parallel.

Most of the reasoning capacity possessed by humans is on the human scale, so that is where most of the physics will be. As any culture advances and refines itself, certain of its practices will become more sophisticated. In the case of Western culture, this process has lead to a subtler experimental construct and with it the “fundamental pillars” in the corresponding idealism.

[Matt R.]

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2) Must it be the case that "life scale" physics will always be the easiest to handle mathematically (it will always be the easiest to access experimentally, of course -- but the question of mathematical access seems subtly different to me).

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I think this is a consequence of your first question -- the fundamental pillars being approximated away. So, I would say the answer to #2 is yes, if #1 is yes as well. "Life scale" physics is, as you said in #1, an approximation to the truly complex stuff you see in the conventionally unobservable world. Thus the math is inherently less complex at this level because we've approximated away all the intricacies about how things really work.

I do not know what I think about #1. I think a place to start would be to ask questions like, "What if the speed of light was not constant to all observers?" or "What if quantum physics behaved exactly like classical physics?" I.e., what if our "intuitive" understanding of the universe and what we observe was how things worked on every level? On the surface it appears that the universe does not have to operate at a "profound" level -- we could conceive of a simple universe were Newtonian mechanics is correct on every scale. But, I have a hunch that if you delve deeper this would have a drastic impact on the universe we observe. I think I would need an understanding of quantum mechanics to be able to ask such questions. Right now I don't know what impact QM has on the macroscopic world, so I can't really hypothesize what the macroscopic world would be like without it.

[chezlaw]

Its hard to put this isn't precise words but it seems that life requires a degree of stability in the environment but not too much.

Life evolves fairly near but not too near the sun because it needs the energy from the sun to drive it forward without being destroyed as fast as it is created.

A certain 'smoothness' in the environment is optimal and maybe this accounts for why life has emerged at the 'smooth' point on the physical scale.

chez

[MathEconomist]

I think a significant portion of this is a function of our understanding of physics rather than physics itself. I think there is some extent to which we are guaranteed to find those areas most close in scale and applicability to us to be relatively simple and widely applicable. You could try confirming this by looking at other fields of study as well, but it's my experience that this is generally true, which makes me think it is a consequence of the way we understand things rather than the things themselves.

[gumpzilla]

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2) Must it be the case that "life scale" physics will always be the easiest to handle mathematically (it will always be the easiest to access experimentally, of course -- but the question of mathematical access seems subtly different to me).

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Well, this is a tough question to discuss, I think. In what sense do you mean mathematically easy? Even at the Newtonian scale we can come up with horrendously complicated abominations of mathematics. I think the thing that makes it simple is that the abstractions that present themselves allow for simplification and approximation, and those abstractions are generally going to be easier or more straightforward when dealt with at the level of sensory experience.

[Metric]

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2) Must it be the case that "life scale" physics will always be the easiest to handle mathematically (it will always be the easiest to access experimentally, of course -- but the question of mathematical access seems subtly different to me).

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Well, this is a tough question to discuss, I think. In what sense do you mean mathematically easy? Even at the Newtonian scale we can come up with horrendously complicated abominations of mathematics. I think the thing that makes it simple is that the abstractions that present themselves allow for simplification and approximation, and those abstractions are generally going to be easier or more straightforward when dealt with at the level of sensory experience.

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This is an interesting point of view, and I think some of the other posters are tending to agree, but I don't believe it's the whole story.

There is no doubt that one can always construct a difficult problem in any given regime of physics, but consider the following: In Newtonian physics, big difficulties in analysis arise at the level of the three-body problem. In GR, this happens already at the level of the two-body problem. And in quantum field theory, it happens at the level of the zero-body problem! I think there is more going on here than just our familiarity and natural intuition for "life scale" physics.

So, I suppose another way of asking the question is the following: Could it ever happen that intelligent life evolves in a regime where quantum effects are "life scale," and such life immediately needs to construct QM to explain everyday things, only later to discover that an enormous "large scale" regime exists in which the mathematical difficulties of QM essentially evaporate? (and similarly for the other "pillars" mentioned in the original post)

I think that a convincing argument one way or the other could potentially be a very interesting and general principle, and may find its way into "anthropic arguments" used, for example, in selecting superstring vacua (it is actually a bit of an embarassment that superstring theory has to resort to these sorts of arguments, but nevertheless there are indeed serious attempts to use them).

[Metric]

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2) Must it be the case that "life scale" physics will always be the easiest to handle mathematically (it will always be the easiest to access experimentally, of course -- but the question of mathematical access seems subtly different to me).

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I think this is a consequence of your first question -- the fundamental pillars being approximated away. So, I would say the answer to #2 is yes, if #1 is yes as well. "Life scale" physics is, as you said in #1, an approximation to the truly complex stuff you see in the conventionally unobservable world. Thus the math is inherently less complex at this level because we've approximated away all the intricacies about how things really work.


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The more I think about this the more I tend to agree with the above paragraph...

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I do not know what I think about #1. I think a place to start would be to ask questions like, "What if the speed of light was not constant to all observers?" or "What if quantum physics behaved exactly like classical physics?" I.e., what if our "intuitive" understanding of the universe and what we observe was how things worked on every level? On the surface it appears that the universe does not have to operate at a "profound" level -- we could conceive of a simple universe were Newtonian mechanics is correct on every scale. But, I have a hunch that if you delve deeper this would have a drastic impact on the universe we observe. I think I would need an understanding of quantum mechanics to be able to ask such questions. Right now I don't know what impact QM has on the macroscopic world, so I can't really hypothesize what the macroscopic world would be like without it.

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There are certainly some very important macroscopic consequences of QM (the stability of all nuclei and atoms, elimination of infinities in radiation spectra, the "solidness" of matter, etc.), but it only becomes clear that "QM is the answer" when you look at a more general range of quantum phenomena at the scale of Planck's constant.

[yukoncpa]

Man’s understanding of the world around him begins with the obvious and works it’s way in both ( multiple) directions to more and more complicated extremes. The Plank constant and the constancy of the speed of light is a culmination of many years of pondering that has taken our understanding to two extremes. Long before Newton, we understood the world to consist of 4 elements - math before Newton must have been extremely simple in comparison, and yet Greek math was a giant leap of understanding in the ancient world.

[IronDragon1]

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I think that a convincing argument one way or the other could potentially be a very interesting and general principle, and may find its way into "anthropic arguments" used, for example, in selecting superstring vacua (it is actually a bit of an embarassment that superstring theory has to resort to these sorts of arguments, but nevertheless there are indeed serious attempts to use them).

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I have just been reading about this stuff for the past few weeks so I'm no expert but if string landscapes on the order of 10^500 different vacuua (?) are real then wouldn't some form of anthropic agrument help in explaining how we reached whatever stable/metastable vacuum conditions that allow our existence?

[cambraceres]

The study of physics is old and natural, and indeed any other lifeforms that emerge in this place or any other will study physics and philosophy as a matter of course. The study of these subjects by whatever beings should pursue them, must be done through the application, or at least under the auspices of a logical order. This logic is totally dependent on the nature of these beings in relation to their environment. All understandings come from the way beings interface with outward reality and themselves. In no other context can anything be understood. In this way, reality dictates the level and elements of our whole thought process.

Cambraceres

[Metric]

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I think that a convincing argument one way or the other could potentially be a very interesting and general principle, and may find its way into "anthropic arguments" used, for example, in selecting superstring vacua (it is actually a bit of an embarassment that superstring theory has to resort to these sorts of arguments, but nevertheless there are indeed serious attempts to use them).

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I have just been reading about this stuff for the past few weeks so I'm no expert but if string landscapes on the order of 10^500 different vacuua (?) are real then wouldn't some form of anthropic agrument help in explaining how we reached whatever stable/metastable vacuum conditions that allow our existence?

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The embarassment stems from the fact that superstring theory has been sold as a theory with no free parameters -- this generated a lot of excitement, the idea that the theory was so unique that the detail of the universe could arise from some very general principles without need for something like "fine tuning."

Then, come to find out, we have this enormous "landscape" of superstring vacua (note that superstring theorists will never, ever refer to it as a "parameter space!"). In some sense, then, the excitement of having a theory unique from first principles has been lost. So now we need some way to select the correct vaccum out of the "landscape." The hope was that the theory itsself could provide a way to do this, but the fact that people are now taking anthropic arguments seriously does not speak well to this hope.

And my final objection is this -- suppose that anthropic arguments cut down the number of "possible vacua" from 10^500 to a mere 10^100 (I do not know the actual numbers involved, but take this for example). I suppose this counts as "great progress" in that they have improved the precision of the theory by 400 orders of magnitude. On the other hand, you're stuck with exactly the same qualitative problem at the end of the day. I suppose it is rather ironic that I'm essentially pondering a new (to my knowledge) anthropic selection principle in the original post.

[cambraceres]

The fact that capable minds are positing solutions using anthropic arguments is not all that odd. Little can be said to be odd in the eyes of a haggard theoretical physicist. Appealing to distasteful solutions has been standard since the Quantum Revolution. I think it was Pauli who said, in reponse to a counterintuitive argument, that it was weird, but maybe not weird enough. The thick jungle of physical law seems to be beyond our simplification in this last era.

This situation has put physicists in the position of being incapable of emabarassment.

You remember when all the discussion was centered around the supergravity debate. Physicists fought like dogs for 15 years over whether the world is described in 11 dimensions or 12, only to find out if they work together and define one in terms of the other, progress was made.

Cambraceres