stupid physics questions

[gravy]

I haven't run it up the flag pole as-yet for its reliance on the hypothetical Unruh Effect...

How does that work?

The 'Unruh Effect'? Or do you mean in terms of its postulated part in modulating gravity? I'm not quite following, but in the meantime...

Sorry, the Unruh Effect and specifically Unruh radiation. It seems to be a recipe for escalating energy and incompatible with GR

being in a gravitational field is identical to accelerating

I'm not sure it's the case here, but sometimes the "identical" is taken too literally. In principle the two are distinguishable.

You're in the proverbial lift-like enclosed space, hereafter 'box'

#1 With your arms outstretched, drop an object from each hand.

a) under acceleration, the two objects will hit the floor spaced exactly as released.

b) in a gravitational field, the two objects will land the tiniest bit closer... triangulated on the center of gravity.

Under acceleration - lines of force are exactly parallel
In a gravitational field - slightly not

#2 Measure the force at the top of the box and compare with the bottom

Under acceleration - same top and bottom
In a gravitational field - slightly less at the top per the inverse square law

Fair enough.

If I had to put money on the winning trick, myself I'd go for gravity being unified with thermodynamics. It's a "force of order".

Is thermodynamics actually a 'thing' or a way of statistically describing things?

My (poor) understanding is it's the 2nd that leads to a quantisation which is pretty much the same bet most of physics seems to be making.

[Dio]

Thermodynamics crops up in all sorts of odd places - and some of the ways quantum mechanics is leaning in information theory start to look very thermodynamical. I get the increasing feeling that if there are fundamental laws, it's something to do with thermodynamics.

[zip accident]

Thermodynamics crops up in all sorts of odd places - and some of the ways quantum mechanics is leaning in information theory start to look very thermodynamical. I get the increasing feeling that if there are fundamental laws, it's something to do with thermodynamics.

I agree, and my belief is that natural selection is deeply connected to thermodynamics and information theory.

[Darkflame]

Is thermodynamics actually a 'thing' or a way of statistically describing things?

Interesting question. I think that comes down to philosophy as much ass science.

I mean, if someone shows you a perpetual motion machine, or one that claims to make energy, you can know its wrong as you cant get something from nothing. But arguably that's just the "statistical result" , the precise reason the machine doesn't work could come down to any number of things. Does the physics work top down from a restriction or bottom up forming it?

Entropy I think can be viewed like this too...as its the result of other rules/forces.
Or did those other rules develop because of a entropy constraint?

[Dio]

Maths and physics have this odd relationship where at some points the physics looks to be defined by the maths - rather than the maths merely describing the physics there's a way of looking at it where they actually start to create it.

I mean, one of the strengths of the standard model is the way that the particles all appear to fall out of a bit of "standard" mathematics known as a Lie group.

[Absolute_Zero]

Sorry, the Unruh Effect and specifically Unruh radiation. It seems to be a recipe for escalating energy and incompatible with GR

Ditto sorry, I can't find a way into your concern as I'm not seeing the basis.

Shot in the dark: would it help by analogy to mention that an object in orbit is experiencing transverse acceleration, perpendicular to the direction of travel, and as such its kinetic energy remains constant?

The Unruh effect is sufficiently hairy that I'm not comfortable to pronounce. Conflict with GR is to be expected since it derives from QFT.

These answers may assist... particularly the second.
https://www.quora.com/What-is-the-signi ... ruh-effect

[KlaxonCow]

my belief is that natural selection is deeply connected to thermodynamics and information theory.

Be careful with that one.

There are "intelligent design" Creationists who argue that evolution can't be true as it "violates the Second Law of Thermodynamics", because they argue that it involves an increase in entropy, which they say is never possible.

[Darkflame]

Dave Gorman did a great takedown of that "logic". Met with some famous american creationist called Dr Gish who seemed to base his whole argument on it.
Can't find a clip unfortunately though.

[gravy]

Is thermodynamics actually a 'thing' or a way of statistically describing things?

Interesting question. I think that comes down to philosophy as much ass science.

I mean, if someone shows you a perpetual motion machine, or one that claims to make energy, you can know its wrong as you cant get something from nothing. But arguably that's just the "statistical result" , the precise reason the machine doesn't work could come down to any number of things. Does the physics work top down from a restriction or bottom up forming it?

Entropy I think can be viewed like this too...as its the result of other rules/forces.
Or did those other rules develop because of a entropy constraint?

Conservation of energy makes a bunch of testable assertions so is likley on a better footing than saying the universe will definitely die a heat death after a while.

Entropy is actually the thing I don't get with thermodynamics because you choose the configuration space and course chunking of it yourself (if I understand it correctly) to get an entropy figure.

I do feel at ease with QM being statisticaly based.







Well entropy is a core component of thermodynamics and again measures a subjectively chosen metric at

[Dio]

If there's one thing I'm sure we've got wrong it's the current formulations of QM. We're missing a trick somewhere. I don't see either the Copenhagen Interpretation or the many-worlds explanations as at all likely.

[KlaxonCow]

Is thermodynamics actually a 'thing' or a way of statistically describing things?

Mind you, in the Einsteinian view, gravity isn't really "a thing" either.

Mass / acceleration distorts local spacetime. With lots of mass in close proximity, it accumulates. A distortion of a distortion of a distortion, as it were. Until spacetime is curved and contorted into twisted geometries where a planet, trying to head off in a straight line, per the laws of motion, finds itself going around the Sun, as the Sun's mass has twisted that "straight line" back round on itself.

In this view, gravity isn't really "a thing" but just the structural geometry of spacetime itself. The "graviton" a purely imaginary particle, just because sometimes it's much easier to do the maths pretending spacetime is flat and then imagining these "graviton" particles exerting a pull on things. But that's just an abstraction. In GR, there is no particle or force or anything, it's all just spacetime geometries.

I mean, at this level, is anything "a thing"?

E = mc^2. Mass and energy equivalence. Mass could be seen as just "highly condensed energy" that only gains its tangibility as "mass" through its interaction with the Higgs boson (somehow, as I confess I don't understand the details of that exactly).

It all gets very Descartesean. What is "certain knowledge" anyway, right?

[gravy]

Nah what I'm getting at is thermodynamics is a study of average behaviour of a mass of things, much like Netwon's laws of motion applied to macroscopic objects.

It's an approximation appropriate for a certain scale; Newton works great for rockets but is just wrong for values way outside of the scale / energies we live at.

Isn't the same true of thermodynamics?

[Dio]

I don't think so. Conservation of energy is absolute, isn't it?

Do you mean that the concept of thermodynamic entropy is meaningless at certain scales - for example if you're considering the behaviour of a single Feynman diagram? True in the classical definition I guess, which requires a temperature to function. But if you start considering the formulations that describe thermodynamic entropy in terms of information entropy, as far as I'm aware it works even down to that level (Maxwell's demon being the typical thought experiment that illustrates that there is a tight link, since without considering the information entropy the demon appears to violate the second law).

I'm not absolutely certain, but entropy seems like something real to me, and I'd put thermodynamics on the top of the list of unlikely physical law violations.

[gravy]

I'm not saying it's not a inviolable law, I'm saying if it is then what's the case?

We don't have a model where Information entropy works at extremes. Black holes are a big problem AFAIK

If the universe had enough mass to pull itself back into a big crunch that'd violate the 2nd law wouldn't it? You'd end with a system that evolves over time to have the same entropy as its initial state.

I know it's more than likely we have an expanding universe but my rubbish understanding is there's nothing fundamentally precluding that our a universe would be that way.

[venusian]

So does an expanding universe make increasing entropy inevitable? Extant matter/energy becomes increasingly thinly spread until it's infinitely thinly - uniformly - spread and thus indistinguishable from full entropy. With increasing volume, things fall apart from each other statistically more often than they come together: as a direct analogy to increasing disorder.

Perhaps the 2nd law is an inevitable consequence of there not being enough mass in the universe to pull it back together i.e. expansion and the 2nd law are different views of the same property.

But the effects of the 2nd law seem to apply locally too. Does this only happen because we live in a universe where the 2nd law applies overall? If we lived somewhere that was contracting, or has the potential to contract, would the 2nd law be inverted locally? Maybe inside a black hole?