|
|
Post by abacus9900 on Mar 23, 2011 21:04:48 GMT 1
We have already discussed the 2nd. law of thermodynamics at length but what about the first law? According to Wikipedia: "The first law of thermodynamics is an expression of the principle of conservation of energy. The law expresses that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed. It is usually formulated by stating that the change in the internal energy of a system is equal to the amount of heat supplied to the system, minus the amount of work performed by the system on its surroundings." en.wikipedia.org/wiki/First_law_of_thermodynamicsNow can someone please express that in normal language? Thank you. |
|
|
|
Post by speakertoanimals on Mar 23, 2011 22:01:47 GMT 1
Well, I'd call that pretty basic! If you can't get your head round that, you're stuck!
WHAT is it about the passage quoted that you don't understand, or is it just another wind-up....................
|
|
|
|
Post by abacus9900 on Mar 23, 2011 22:10:29 GMT 1
Well, I'd call that pretty basic! If you can't get your head round that, you're stuck! WHAT is it about the passage quoted that you don't understand, or is it just another wind-up.................... Point is, you can't ask a piece of text questions. |
|
|
|
Post by Progenitor A on Mar 24, 2011 8:24:38 GMT 1
We have already discussed the 2nd. law of thermodynamics at length but what about the first law? According to Wikipedia: "The first law of thermodynamics is an expression of the principle of conservation of energy. The law expresses that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed. It is usually formulated by stating that the change in the internal energy of a system is equal to the amount of heat supplied to the system, minus the amount of work performed by the system on its surroundings." en.wikipedia.org/wiki/First_law_of_thermodynamicsNow can someone please express that in normal language? Thank you. Well, I have seen simpler expressions of this law, such as 'energy cannot be created or destroyed the total energy in a system is always constant' The law is of course, an hypothesis that is contradicted by other physical hypotheses Trouble is, these laws were formulated by clever engineers with dirty finger-nails scribbling on oil-smudged pieces of paper, their purpose being to establish solid principles to get their Manchester heat engines working as efficiently as possible to make them rich, and for that purpose they are fine I do not think that they were ever intended for metaphysical purposes, which is how many physicists regard them today They were not meant to be general statements, simply working practice, I think For when we do get metaphysical, the laws are self-evidently contradicted. Take for example the BB If no energy can ever be created then the universe was always there! The energy just somehow how coalesced to create the BB. As we know that goes against other physical (metaphysical) hypotheses that demand that the BB - the universe, was created out of nothing at all Now, take our universe as it is. It should be of constant energy according to that law. and that sounds pretty reasonable prima facieHowever there are physical (metaphysical) hypotheses that state that new energy is being constantly created in the universe. Indeed, our old favourite QM makes that quite a central plank of its dogma Some Cosmologists say that the rate of expansion of the Universe has accelerated and decelerated over the life time of the universe, and that cannot have happened without some additional energy being created, can it? And just take the expansion of the universe itself where many scientists consider it is expanding at an accelerating rate. Just consider that! All that matter accelerating! As it accelerates it gains kinetic energy! So the energy of the universe is by definition increasing! Now lets go back to the 1st Law OK for Manchester heat engines Bit tattered around the edges, (not to say shredded) when pencil-wielding mathematicians get their well-manicured hands upon it Either modern physics is bollocks Or the 1st Law of thermodynamics is bollocks Take yer pick matey! |
|
|
|
Post by speakertoanimals on Mar 24, 2011 13:26:56 GMT 1
NM, you're talking nonsense, I'm afraid! The conservatoin of energy (and momentum, and angular momentum) comes from the symmetry of the laws of physics under translation in time, translation in space, or rotation.
As regards the universe, the universe could have arisen as a quantum fluctuation IF the total energy was zero, the positive energy of matter and radiation balanced by the negative energy in curved spacetime.
Pretending that the law of conservation of energy is dodgy is just daft, I'm afraid. Quantum theory says energy conserved on average, that is the point about the Heisenberg uncertainty principle -- you can violate for a short time, but that is all, and the size of the amount of energy borrowed determined how quickly it has to be paid back! Hence the greater the energy of a quantum fluctuation, the shorter it lasts. But you still get energy conservation on average.
|
|
|
|
Post by carnyx on Mar 24, 2011 15:11:40 GMT 1
And, can we detect these quantum fluctuations? Would they manifest themselves as 'noise'?
|
|
|
|
Post by speakertoanimals on Mar 24, 2011 15:29:39 GMT 1
These quantum fluctuations in empty space give rise to the Casimir effect (a very small force between two uncharged parallel metal plates), and to slight perturbations in the energy levels of atoms.
The 'noise' in effect is the fact that the lowest energy state of a quantum system isn't at zero, even at zero temperature. Hence we have all those weird effects for liquid gases at low temperatures. Its all zero-point energy in effect, just for different systems, whether it is for an atom or molecule, or for the em field in empty space. The lowest energy isn't zero.
|
|
|
|
Post by carnyx on Mar 24, 2011 18:34:36 GMT 1
Ah! so could those slight perturbations in those atoms generate EM waves?
And could they be the contributors to that 'background radiation'
|
|
|
|
Post by speakertoanimals on Mar 24, 2011 21:26:45 GMT 1
No, its a perturbation to the computed energy level from theory, NOT saying that atoms somehow suck up energy from the vacuum and re-radiate it as some sort of fuzzy background................
WHY not just learn the basics, WHY attempt to try and criticise basic cosmology when you don't even know the basics as regards matter and radiation.......................
|
|
|
|
Post by abacus9900 on Mar 24, 2011 21:28:18 GMT 1
No, its a perturbation to the computed energy level from theory, NOT saying that atoms somehow suck up energy from the vacuum and re-radiate it as some sort of fuzzy background................ WHY not just learn the basics, WHY attempt to try and criticise basic cosmology when you don't even know the basics as regards matter and radiation....................... STA I may have to find a more helpful science MB. |
|
|
|
Post by speakertoanimals on Mar 24, 2011 21:35:26 GMT 1
Good luck with that! Mind the door on your way out..............
|
|
|
|
Post by abacus9900 on Mar 24, 2011 21:53:03 GMT 1
Charming.
|
|
|
|
Post by speakertoanimals on Mar 24, 2011 22:29:20 GMT 1
compared to your general level of responses to me? What was it you called me last time round?
don't let me detain you from your search for a nicer board...........
|
|
|
|
Post by carnyx on Mar 24, 2011 22:29:56 GMT 1
@sta
The Casimir pressure is by no means insignificant. Even at nanotechnology levels it approaches one bar (15 psi in old money) and gets rapidly stronger at intermolecular distances, as it has that 1/D^2 property and where lots of vacuum spaces still exist.
.And your
is an admission of sorts, I suppose. Has this energy density been quantified and equated to the 'background radiation' ?
|
|
|
|
Post by speakertoanimals on Mar 24, 2011 22:34:55 GMT 1
Except the point about vacuum fluctuations is that they appear then disappear! So, you get particle-antiparticle pairs like electrons and positrons being created, but we DON'T see these, because they annihilate almost as soon as they were created. The only time we would see them is when one is captured by a blackhole (Hawking radiation), which is why blackholes are totally black!
I never said the Casimir effect didn't matter -- the force is measurable else we wouldn't have discovered it in the first place.
But it doesn't explain WHY space seems to be filled with a uniform gas of photons, at a particular and INCREDIBLY uniform temperature............
|
|
