Physics Help Forum The formula E = mc^2 never have been proved?

 Special and General Relativity Special and General Relativity Physics Help Forum

Feb 24th 2018, 10:15 AM   #21
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 Originally Posted by Ziang This is a link galileo.phys.virginia.edu/classes/252/mass_and_energy.html
That website is misleading. The box isn't a fake as the author claims. A.P. French from MIT created a similar derivation which takes into account a non-rigid box and arrives at the same result. The article was published in the American Journal of Physics.

Feb 24th 2018, 01:51 PM   #22

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 Originally Posted by Pmb benit13, Dan - Have you read Einstein's 9105 paper on mass-energy equivalence.? Einstein didn't use the gamma factor because the derivation was for a slowly moving body. When he later derived the same result for EM radiation there too the gamma factor is absent. Its only for a particle moving at a speed comparable to the speed of light that gamma comes into play. In that case it cannot be avoided.
Actually,yes I have. I have forgotten who first used the used the $\displaystyle \gamma$ notation.

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 Feb 24th 2018, 02:23 PM #23 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 995 Are y'all sure about that? Here is an extract from (the admitedly English translation) of the 1905 paper On the Electrodynamics of Moving Bodies A Einstein June 30 1905. Here he is clearly using beta instead of gamma, quite liberally in the equations above. Here also is Wiki on the subject which shows that symbology has changed as beta is now used for something else. https://en.wikipedia.org/wiki/Lorentz_factor Attached Thumbnails   topsquark likes this. Last edited by studiot; Feb 24th 2018 at 04:11 PM.
 Feb 24th 2018, 03:41 PM #24 Forum Admin     Join Date: Apr 2008 Location: On the dance floor, baby! Posts: 2,468 I did read it, but perhaps not recently enough. See here. -Dan __________________ Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup. See the forum rules here.
 Feb 24th 2018, 07:45 PM #25 Junior Member   Join Date: Feb 2018 Posts: 7 If the equivalence can come from absolute space and time then why absolute space and time is not a possible candidate for reality?
Feb 26th 2018, 07:00 AM   #26
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 Originally Posted by Ziang This is a link galileo.phys.virginia.edu/classes/252/mass_and_energy.html

I think the key here is two sentences:

"Now it is known from Maxwell’s theory of electromagnetic waves that a flash of light carrying energy E also carries momentum p=E/c. Thus, as the flash leaves the bulb and goes down the tube, the box recoils, like a gun, to conserve overall momentum. Suppose the whole apparatus has mass M and recoils at velocity v. Of course, v<<c."

and

"The only way this makes sense is to say that to counterbalance the mass M moving d backwards, the light energy must have transferred a small mass m, say, the length L of the tube so that

Md=mL
and balance is maintained"

You have light carrying momentum and interacting with matter? Furthermore, you have light transferring mass to a box? That's not classical thinking at all.

Note that Maxwell's insight into light carrying momentum was key to moving scientists away from classical thinking and into contemporary thinking, so the same idea is used to propose a thought experiment into how one might derive $\displaystyle E = mc^2$ without knowing about the photon. That's fine, but it seems we're following history now rather than finding an alternative that neglects contemporary ideas.

Feb 26th 2018, 10:15 AM   #27
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 Originally Posted by Ziang If the equivalence can come from absolute space and time then why absolute space and time is not a possible candidate for reality?
Because it contradicts reality. Just because something can be derived without using the properties of spacetime it doesn't imply that everything can.

 Feb 26th 2018, 07:35 PM #28 Physics Team   Join Date: Apr 2009 Location: Boston's North Shore Posts: 1,570 For those who didn't read this entire thread, the claim The formula E = mc^2 never have been proved? is invalid. First because no formula in any science can ever be proven and second because its been born out by experiment on a daily basis in every particle accelerator in the world for close to a century.

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