Is the sub-atomic world some kind of perpetual motion engine?

[Simon666]

Originally Posted by ServiceSoon

Show me a perpetual motion machine and I'll get you a Nobel Prize.

Superconducting wire. Where is my Nobel Prize? I can add it to the one given to the EU. That's TWO on my desk.

[lenny]

Originally Posted by Roboramma

No, he was simply pointing out that no one is afraid to contemplate laws of physics in which energy is not conserved, which you seemed to be implying.

my apologies if my words were misleading in that direction: i did NOT intend to imply anything of the sort! there are nice counterexamples in the 40's/50's where energy only "statistically conserved."

rather i argued (#18) that no one has "showed conservation of energy", and that it is currently inconceivable that one ever will in many relevant macroscopic scenarios.

TubbaBlubba repeatedly (#19, #24, and i had thought in #38) made naive claims claiming the absence of evidence as evidence of absence
(as you noted in #20).

i took his #38 as supporting Cuddles #30 claim that showing conservation of energy on planetary scales was "quite easy really. Conservation of energy is one of the fundamental bases of all our ideas about physics." which fails Logic 101 as an argument. i first read TubbaBlubba's post as supporting that falasy; i now see he might have intended something else.

what was your intention TubbaBlubba?

[TubbaBlubba]

Originally Posted by lenny

my apologies if my words were misleading in that direction: i did NOT intend to imply anything of the sort! there are nice counterexamples in the 40's/50's where energy only "statistically conserved."

rather i argued (#18) that no one has "showed conservation of energy", and that it is currently inconceivable that one ever will in many relevant macroscopic scenarios.

TubbaBlubba repeatedly (#19, #24, and i had thought in #38) made naive claims claiming the absence of evidence as evidence of absence
(as you noted in #20).

i took his #38 as supporting Cuddles #30 claim that showing conservation of energy on planetary scales was "quite easy really. Conservation of energy is one of the fundamental bases of all our ideas about physics." which fails Logic 101 as an argument. i first read TubbaBlubba's post as supporting that falasy; i now see he might have intended something else.

what was your intention TubbaBlubba?

My intention is to not discuss science with people who believe science requires formal logical proofs of theories.

[lenny]

Originally Posted by TubbaBlubba

My intention is to not discuss science with people who believe science requires formal logical proofs of theories.

so there we do not clash; surely any connection between science and formal proof is tenuous at best.

the question under discussion was an empirical one, specifically whether or not one could establish the conservation of energy on planetary scales.

[TubbaBlubba]

I'm fairly sure planets suddenly being governed by different laws of physics would've been discovered by now.

Deep out in the cosmos, it's tougher, but AFAIK no one has yet come up with a theory that explains the cosmos better than general relativity, which more or less assumes the cosmological principle. Until someone does or it turns on we can't explain the physics of say, distant stars using our established laws, I think we can assume the principle holds true.

[lenny]

the question is an empirical one, limits to what we can measure which apply as much to the earth and the moon as anywhere else.

the point is that while we have stong evidence placinfg constraints on the conservation of energy in the lab, we have no such evidence, nor can we conceive of an experiment that would provide such evidence, that energy is conserved on planetary scales, or "in the sun".

we often do a thought experiment: considering a large sphere around the moon, and argue that the energy moving in through this surface minus the energy moving out, plus the increase in energy inside will sum to zero.
i am not arguing that this is not true; merely pointing out that we have no empirical evidence that it is true. violations vastly greater than those we can rule out in the lab would be undetectable.

we have faith in the conservation of energy on these scales, we believe it holds, but the evidence for it absent.

Originally Posted by TubbaBlubba

I'm fairly sure planets suddenly being governed by different laws of physics would've been discovered by now.

so i do not see how your comment applies to this argument.

[Roboramma]

A similar argument suggests that we don't have evidence that conservation of energy holds when I am wearing a tutu (I've never worn a tutu)

[quarky]

Originally Posted by Roboramma

A similar argument suggests that we don't have evidence that conservation of energy holds when I am wearing a tutu (I've never worn a tutu)

You would look good in a tu-tu.

(hey, it's a scientific fact.)

[Ziggurat]

Originally Posted by lenny

the point is that while we have stong evidence placinfg constraints on the conservation of energy in the lab, we have no such evidence, nor can we conceive of an experiment that would provide such evidence, that energy is conserved on planetary scales, or "in the sun".

That's not really true. The evidence is less direct, but it's not nonexistent.

In particular, there's a very rigorous mathematical theorem which states that for every symmetry in your physical laws there will be a corresponding conservation law. The fact that our laws of physics are translation-invariant (meaning the laws of physics don't vary from location to location) leads to momentum conservation, for example. And the fact that our laws of physics are time-independent leads to the conservation of energy.

If conservation of energy is to be violated, that will require that the laws of physics vary in time. And that would produce signs other than just the violation of energy conservation. It's true that variations could always be too small to observe (but the energy conservation violations would then be correspondingly small), but that problem exists whether you're talking about experiments in lab or observations of distant astronomical phenomena. Our precision may be greater in the lab, but the basic problem remain the same.

[lenny]

Originally Posted by Ziggurat

It's true that variations could always be too small to observe (but the energy conservation violations would then be correspondingly small), but that problem exists whether you're talking about experiments in lab or observations of distant astronomical phenomena. Our precision may be greater in the lab, but the basic problem remain the same.

i agree that the basic problem remains the same. apologies if i spoke loosely.

there does seem to be a difference between measurements on the lab, where we can work vary hard to find inconsistency and have not yet found it, and measurements on the scale of a planet which we have never attempted and for which we can only conceive (today) of obtaining a very loose bound on consistency. of course today's laws of physics give us no reason to expect anything different on planetary scales... and defending that last statement leads to circularity.

[Ziggurat]

Originally Posted by lenny

of course today's laws of physics give us no reason to expect anything different on planetary scales... and defending that last statement leads to circularity.

Certain kinds of changes in the laws of physics from one location to another will show up even over vast distances. In particular, atomic and molecular spectra are sensitive to the laws of quantum mechanics, and unless the changes happen in very specific ways (or below our detection threshold), then we could see signs of it. That doesn't preclude any possible position dependence to the laws of physics, but it does constrain such changes. Beyond that, though, it's not so much circularity as it is Occam's Razor. The simplest scenario would be universal laws of physics, that accurately describes what we can currently observe, so that's a preferable model to one in which the laws of physics are not universal. Occam's Razor doesn't tell you that the simpler explanation is correct (or even that it's more likely to be correct), but it does tell you to stick with simplicity until it's inadequate. That time has not arrived.

[quarky]

nice.