Is the law of conservation of energy generally true?
Brian M asked:
I know the conservation of energy can be violated for short times, but not overall. is that right?
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I know the conservation of energy can be violated for short times, but not overall. is that right?
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When can it be violated over short intervals?
Energy is concerved (at least as a 4-vector) and space is homogeneous. Pretty much.
Comment by Ian — November 21, 2008 @ 3:54 am
It’s totally right. look at how your gas mileage is affected when the air conditioner is on. It’s totally aplicable in every day life but we usually don’t think about such things.
Comment by severedhead — November 24, 2008 @ 1:43 pm
Yes, otherwise it would not be called a law. It would be called a theory or theorem.
Comment by Mez — November 25, 2008 @ 4:43 pm
Definitely it is right. You need not have to doubt that law.
Comment by siva k — November 28, 2008 @ 10:03 pm
Depends on how you think about it.
If you are real famous people will believe everything you say.
Not every law has enough evidence only if you find evidence that is contradictory to the oringinal law.
Comment by 3.141592654 — December 1, 2008 @ 7:07 pm
If our observations are not perfect and during observation if we sleep, then the law will seem to be violated during that short time of our sleep.
Comment by pearlsawme — December 1, 2008 @ 10:44 pm
Nice question. Everybody says that energy is always and perfectly conserved, but the reality is something else. You are right, it can be violated for short times, within the Heisenburg uncertainity limits, and this has to be figured in calculations in quantum field theories. For example, a gauge boson could momentarily acquire energy out of nothing for the short time of its existence, within quantum uncertainity limits. Professional physicists know all about this, they do the math with this, but for some reason, it’s not relayed to the public.
Now let’s move to the more interesting stuff. Noether’s theorem states that conservation of energy is a consequence of temporal symmetry. That is to say, if physical equations are invariant with respect to translation in time, then energy is conserved. However, that does not mean that everything is invariant with respect to time. In more extreme cases, at the boundary beyond ordinary spacetime as we know, as for example. inside black holes or at Planck dimensions of spacetime (think really tiny now, smaller than even strings), ordinary laws of physics or even time itself breaks down, and energy may not be conserved. And some important equations in physics, such as the relativistic version of the Schrodinger wave equation, called Klein-Gordon equation, energy is not conserved either. So, in answer to your question, yes, the law of conservation of energy is generally true, because generally speaking, we’re talking about ordinary spacetime with nice well behaved symmetries that we’ve all come to rely on for our reality, but such symmetries in fact cannot be taken for granted. There is no fundamental reason why they MUST necessarily exist in all cases, nor there is any mathematical proof of that.
Comment by scythian1950 — December 2, 2008 @ 1:33 am
it is true because,
Energy can neither be created nor be destroyed.
It can be converted from one form to energy .
Comment by ADITYA A — December 4, 2008 @ 3:23 pm