Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: neilep on 29/10/2024 15:41:04
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This got me thinking from my other thread regarding the absolute zero and motion of quantum stuff.Why does Quantum Stuff Still Move At Absolute Zero ? | Naked Science Forum (https://www.thenakedscientists.com/forum/index.php?topic=87081.0)
Seeing as Atoms are always moving because they always have energy !
1: Where does the energy come from ? 2: Does this make atoms (et al) Perpetual Motion Machines ?
Thank You
Quantum Entangled Wooly Cloud !
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It makes them perpetual, but not machines because any model of an atom that invokes movement must require that movement to be essentially random. Heisenberg rules!
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It makes them perpetual, but not machines because any model of an atom that invokes movement must require that movement to be essentially random. Heisenberg rules!
Maybe in the future, our descendants will be able to harness the power of this motion to make a perpetual machine ?
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Where does the energy come from ?
It was always there since the atom was made.
2: Does this make atoms (et al) Perpetual Motion Machines ?
No. A PMM is something from which indefinite work can be extracted, at however small a rate. One cannot extract indefinite energy from the motion of an atom.
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By eliminating all losses such as friction it is, in principle, possible to make a contraption that would exhibit perpetual motion. It would, however, be totally impossible to harvest any energy from this.
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Maybe in the future, our descendants will be able to harness the power of this motion to make a perpetual machine ?
Only if they repeal the most fundamental laws of physics and common sense. But I wouldn't put that past Donald Trump and the US Supreme Court..
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Yep, repeal both the first and second laws of thermodynamics and the global energy problem is solved. On further deliberation repeal of either would do the job.
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I am sure our descendants will figure it out, hopefully pre self annihilation. What we know now was magic just a few hundred years ago so I have every faith in human ingenuity to discover what we deem impossible now.
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I am fairly sure the first law is sacrosanct and will never be broken. I can foresee the possibility of very limited cases where the second law does not hold- these will be highly contrived scenarios and I don't reckon any great usefulness will arise from these. Bottom line, I don't think future generations will find a significant way around these laws. Ewe may hold a different opinion but we won't fall out over it.
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By eliminating all losses such as friction it is, in principle, possible to make a contraption that would exhibit perpetual motion. It would, however, be totally impossible to harvest any energy from this.
Maybe in the future they will be able to produce fusion machines...energy problem sorted. :)
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I am fairly sure the first law is sacrosanct and will never be broken. I can foresee the possibility of very limited cases where the second law does not hold- these will be highly contrived scenarios and I don't reckon any great usefulness will arise from these. Bottom line, I don't think future generations will find a significant way around these laws. Ewe may hold a different opinion but we won't fall out over it.
They may be able to ' bend' the rules a little....maybe they can transfer energy from one place where the physics are different.......... to us. ;)
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Good luck finding somewhere with different laws of physics. As far as we know the same laws apply everywhere.
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Hi.
I am fairly sure the first law is sacrosanct and will never be broken.
The first law is usually stated in terms of energy passing into or out of some system or body. We might assume the universe is a suitable closed system. However, General relativity only enforces a local conservation of energy principle on the universe, globally the total amount of energy in the universe could change.
E-m radiation travelling through an expanding universe increases in wavelength. The energy doesn't appear to have gone somewhere else, it is just lost. More generally, as per Noether's theorem, since an expanding universe does not posses time translation invariance, we would not expect to have a conserved quantity that we could call "Energy".
I'm fairly sure you ( @paul cotter ) already know and have heard this sort of thing before. It makes no practical difference here on earth and over timescales of a human lifespan. Over that span of time, our local bit of the universe hasn't changed very much and time-translation symmetry is a very reasonable approximation. Hence, there is an associated quantity we can call "energy" and it is independant of time (it is "conserved").
Anyway, if you ( @neilep or anyone else) want to defy the first law of thermodynamics then (I would think) the easiest approach is just to change time and space. For example, adjust the expansion rate to suit your purposes. So that's the theory bit all done and dusted. All you need next is some engineers and technologists to do their bit and make the equipment.
Best Wishes.
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Is it not the case that, where the source is receding from the receiver, the photon red shift equals the increase in gravitational potential of the transmitter?
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Alan, can't help you there, that question is beyond my pay grade. ES, that is a good question I have pondered, without any profit- where does the energy of red shifted light go? As regards manipulating space and time I don't think we have anything that could do so. To actually gain energy, which is what I believe Neilep has in mind, one would have to compress space and I have not the faintest idea of how that might be achieved. That is all I am saying, having had a few drinks tonight, if I say anymore i'm sure I will put my foot in it, as is said.
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Hi.
Is it not the case that, where the source is receding from the receiver, the photon red shift equals the increase in gravitational potential of the transmitter?
No. For a start, in the most general situation where we have a dynamic and curved spacetime, there just isn't a sensible "gravitational potential" that we can identify.
Gravitional potential is something that may seem like it should be there - but that's just what follows from Newtownian mechanics where gravity was a force.
Reference: An informal discussion appears here: https://www.nature.com/articles/314129a0.pdf
Best Wishes.
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Yet when we apply gravitational potential corrections, we get the right answer...
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Hi.
Yet when we apply gravitational potential corrections, we get the right answer...
No, I don't think we do, sorry.
There is a thing called gravitational red-shift. That's an approximation we can make when the metric tensor is spherically symmetric and static (unchanging with time), for example when light leaves from a star and travels away from it. In that situation we can assume the Schwarzschild metric is a fair approximation of the metric tensor in this region of space and time. So, yes, we can and do use these approximations when they are appropriate.
In the more general case of a metric that isn't spherically symmetric and is dynamic (evolving with time) we just can't easily or unambiguously a thing we could call gravitational potential energy.
Several attempts to identify a thing we could call gravitational potential have been made. One of the most reasonable involves the Lifshitz Psuedo-tensor. See https://en.wikipedia.org/wiki/Stress%E2%80%93energy%E2%80%93momentum_pseudotensor for more discussion.
It is, however only a pseudo-tensor not a genuine tensor which is what we would really want.
Best Wishes.
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Given that the universe is not static nor necessarily symmetric, how do current calculations of red shift match up to actual measurements for distant stars?
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Hi.
....how do current calculations of red shift match up to actual measurements for distant stars?
I don't know what the actual measurements are but I expect you can Google for results.
Ummm.... I may have misunderstood your question but if it is what I think, then half the problem will be the way we measure distances to distant stars. We can't run a long tape measure out to them so we use the technique(s) often described as being part of the Astronomical distance ladder.
So, one way to determine the distance to a distant star is to identify the red-shift in an absorption or emission line. But then... well, obviously.... you're going to get good agreement between the expected red-shift of a star at this distance and the actual red-shift you have measured - that was how you estimated the distance anyway.
If you're lucky then the thing you're looking at is a Cepheid or a Type 1a supernova, or at least seems to be in the same vicinity as one of these things, then you could estimate the distance to it another way.
I'm not sure if this connects with your earlier notions of there being a gravitational potential.
Best Wishes.
LATE EDIT:
Here's a list of some of the most distant astronomical objects, with their estimated proper distance from us and their red-shift, if you want it:
https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects#