Notion of matter, space and time

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  • #51
Eh
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Originally posted by wuliheron
I hate to be the one to inform you, but E=MCC is far from an uncertain proposition. It is an absolute and unrelenting statement about existence.
That has nothing to do with the uncertainty of QM. The uncertainty principle rather bluntly states that you cannot know the precise position and momentum of a particle at the same time. The most common interpretation is that particles simply do not posses both attributes at once. But that is all. QM does not say the definition of fields and particles is uncertain, nor that mass and energy are the same thing. Just because the energy distribution in uncertain, does not mean physical laws must fail.
 
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  • #52
Eh
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Originally posted by Royce
No, I'm not sure of anything at this point. My understanding was the same as yours; but, others seem to think that photons have all of the same attributes as matter and matter has some of the attributes of energy. I'm not sure that any concensus was reached and it rapidly went over my head. It is a thread on the physics forum now on page 3 entitled Photons started by me, Royce, if you want to read it.
Well it gets confusing when someone mentions that light does have mass - but only relavistic mass. The important thing to remember here is rest mass. Light does not have it, and in science it is not considered matter. Neither are the other messenger particles.
 
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  • #53
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Originally posted by Eh
That has nothing to do with the uncertainty of QM.
Prove it. Theoretical physicists have been arguing for decades whether Relativity is subject to QM or vice versa. If you can prove the two have nothing to do with each other, at the very least, you will make some of the greatest minds on the planet look like fools.
 
  • #54
Eh
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They are talking about general relativity, not special. In fact, special relativity is an important aspect of quantum field theory, which has been quite successful. It seems to be the curved spacetime of general that causes so much difficulty.

Actually, you caught me before I finished editing a post. The uncertainty of QM is associated with energy, but does not mean physical laws and definitions are also uncertain.
 
  • #55
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Originally posted by Eh
They are talking about general relativity, not special. In fact, special relativity is an important aspect of quantum field theory, which has been quite successful. It seems to be the curved spacetime of general that causes so much difficulty.

Actually, you caught me before I finished editing a post. The uncertainty of QM is associated with energy, but does not mean physical laws and definitions are also uncertain.
Experiments are still being conducted to see if protons die or not, and whether or not the speed of light changes over time. Whether the laws of nature are unvarying is still up in the air and very much the subject of study today.

At issue again is whether or not nature is fundamentally chaotic, as QM asserts, and if so why do we perceive just a few things as virtually unchanging in a universe that is otherwise changing constantly. On these issues Standard theory has nothing to say and precisely because it has not been fully integrated with Relativity yet it remains suspect.
 
  • #56
Eh
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Whether or not the speed of light varies, or if protons decay or not isn't the point. The claim that E=MC2 contradicts QM is wrong.
 
  • #57
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Originally posted by Eh
Whether or not the speed of light varies, or if protons decay or not isn't the point. The claim that E=MC2 contradicts QM is wrong.
And why is that? As far as I can see E=mcc makes a fundamental metaphysical assertion about nature that contradicts QM which strongly implies there is no metaphysical basis for nature... unless you consider chaos to be "principle."
 
  • #58
Eh
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QM makes no such metaphysical statements, and therein lies the problem. As I said, the uncertainty principle is only a matter of the energy level and position of a particle.
 
  • #59
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Originally posted by Eh
QM makes no such metaphysical statements, and therein lies the problem. As I said, the uncertainty principle is only a matter of the energy level and position of a particle.
Thus far there are eight parameters of subnuclear particles which QM is applied to. It applies to not only the energy levels and position, but to the spin, magnetic moment, and other measurable characteristics. In recent decades this list has been slowly expanding to include characteristics such as the "shape" of what have otherwise been described merely as point particles. To assert that Uncertainty principle applies only to the energy level and momentum of a particle is absurd.
 
  • #60
Eh
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Spin has to do with energy, and the properties of fields such as EM do as well. So the uncertainty applies there. Really, it's not really debatable. The uncertainty principle by definition, only deals with the energy and position. It does not make the metaphysical claims you say it does.
 
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  • #61
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Originally posted by Eh
Spin has to do with energy, and the properties of fields such as EM do as well. So the uncertainty applies there. Really, it's not really debatable. The uncertainty principle by definition, only deals with the energy and position. It does not make the metaphysical claims you say it does.
Exactly, they are all inter-related and which position you choose to view the subject from is entirely subjective. Is it really merely energy and position, shape and spin, or whatever? To assert that it is merely the position and energy levels is to assert the reductionist position which remains unproven and, in fact, is contradicted by the theory itself and the observational evidence.
 
  • #62
Eh
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They are all fundementally the same thing. So the uncertainty of position and momentum of a particle can be related to the equivalent for fields. Remember that quantum theory is a theory about energy. It is not a theory of space and time, and it certainly is not a theory about the laws of physics. In fact, quantum field theory itself is built on these physical laws, (the postulates of special relativity are included) and requires a backdrop of spacetime.

So QM in its current state does not say there is no metaphysical basis for nature. A quantum theory of spacetime simply does not yet exist.
 
  • #63
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Originally posted by Eh
They are all fundementally the same thing. So the uncertainty of position and momentum of a particle can be related to the equivalent for fields. Remember that quantum theory is a theory about energy. It is not a theory of space and time, and it certainly is not a theory about the laws of physics. In fact, quantum field theory itself is built on these physical laws, (the postulates of special relativity are included) and requires a backdrop of spacetime.

So QM in its current state does not say there is no metaphysical basis for nature. A quantum theory of spacetime simply does not yet exist.
Again, exactly! Quantum theory is an ad hoc theory arrived at by default precisely because no other theory at the time could describe what was being observed. Whether or not such a theory can be said to possess a metaphysics or not is extremely debatable and the subject of controversy. Exactly what QM describes and does not describe is the entire focus of the theory!
 
  • #64
Eh
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There is no debate though, that current quantum theory does not describe spacetime itself. In fact, quantum theory assumes a fixed background of some absolute spacetime metric in which events of the quantum world take place. Since spacetime seems to be fundemental in nature, it will take a TOE to see what metaphysical claims about the ultimate reality of the world quantum theory can make.

In it's current form, QM is not contradicted by Einstein's famous equation, and simply does not deal with the issue of space and time.
 
  • #65
r637h
Thank you for your answer concerning spin.I suppose spin is considered a quantum unit. The same way with quarks: since they have mass, they must obey quantum principles.

My statement concerning concerning Physics vs. Philosophy (more properly, Metaphysics) was intended as analogy, not a logical proposition.

Back to Planck: I believe the hypothesis is that, before Planck time,
there was no dichotomy between matter and energy. Some believe it was singularity (particle, if you will) and some believe there was only energy; I believe the concepts are moot. The laws of Physics did not exist before Planck time. We can't ever know (a bold statement) what existed before Planck time, because it cannot be measured.
 
  • #66
ando
Question for the gurus:

Have a running debate with a friend of mine that says if I run 1 mile then I will have burned the same energy when I walk a mile. I say that since E=MC2, then the ammount of energy I burn increases exponentially as I increase my rate of travel. Does anyone have a difinitive answer to this question? Could you possibly quote sources or provide a URL to an essay or article that explains this?
 
  • #67
FZ+
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You are both wrong.

Your friend is wrong because the way your body does work is not an ideal system. You are not working up some potential or something, but rather the running or walking movement, and the use of your muscles is extremely inefficient. There is an optimum rate of motion for your muscles that would save more energy and give the most effective technique, minimising waste heat.

You are wrong because you misuse E=mc^2. E= mc^2 is a conversion formula from mass to energy for resting objects. The human body sadly does not run on nuclear power...
 
  • #68
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Originally posted by FZ+
The human body sadly does not run on nuclear power...
Sadly? Let us be happy we have all the nuclear power we need, but in safe distance for the next couple of biliion years.
 

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