Mass of Light Watch

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MRLX69
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#61
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#61
Elpaw is right on this one. Rest Mass is constant.
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Newton
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#62
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Look to be honest... We can carry on about this for ages... I do not mind... But it is only fair, in my opinion, to say that yes light, in general, does have mass.

Newton.
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Newton
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#63
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(Original post by MRLX69)
Yes the mass does increase but it's different from the REST mass.
LOOK EVEN HE SAID IT! IT DOES HAVE MASS WHICH INCREASES!

Newton.
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MRLX69
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#64
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I think light has mass also. But the rest mass is different from the mass travelling at 999ms^-1. That's all i'm trying to say.

I think light must have mass because it has momentum.
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elpaw
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http://www.weburbia.demon.co.uk/physics/light_mass.html

the short answer is no, light does not have mass, because it is atheistic :p:
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Newton
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#66
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Ponder about this will you...

Einstein's work:

m_0 is the rest mass

Newton.
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john !!
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#67
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light does not have a rest mass
it is massless
however it has a momentum
may be hard to swallow but it's true.
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MRLX69
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#68
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(Original post by Newton)
LOOK EVEN HE SAID IT! IT DOES HAVE MASS WHICH INCREASES!

Newton.
lol, yes i did say it. But what I don't understand is that if matter is meant to have infinite mass when travelling at c, why don't light have infinite mass?

Unless energy and mass is constantly interchanging... :confused:
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MRLX69
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#69
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(Original post by mik1a)
light does not have a rest mass
it is massless
however it has a momentum
may be hard to swallow but it's true.
I REALLY don't understand, how can something have mommentum without mass?! cool pic Newton.....hmmmmm..... *pondering*
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elpaw
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#70
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(Original post by MRLX69)
lol, yes i did say it. But what I don't understand is that if matter is meant to have infinite mass when travelling at c, why don't light have infinite mass?
because it only has infinite mass if it has rest mass. light has rest mass 0 and therefore not infinite mass at c (look at newtons attachment, m0 = 0)
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john !!
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(Original post by Newton)
Ponder about this will you...

Einstein's work

m_0 is the rest mass

Newton.
what's to ponder? it's a relativistic transformation
mass = restmass*(1/(1-(V^2/c^2))
same with time and length contraction... whether it's true or not I'm not sure; I haven't seen it in any book I've read.
is m0 is zero then so too is m.
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Newton
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#72
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Oh come on World... Do you not remember Einstein trying to fool the world with his "Cosmological" constant!?
Newton.
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MRLX69
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#73
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But if light have no rest mass, how can mass increase at c when there's no mass in the first place?
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jpowell
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#74
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This is getting to be another quack science thread. Why on earth do we have to waste out time talking about very old problems. The concept of light having momentum has been around since Maxwell's time, just look at his equations, they state that electromagnetic waves have momentum.
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john !!
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(Original post by MRLX69)
I REALLY don't understand, how can something have mommentum without mass?! cool pic Newton.....hmmmmm..... *pondering*
Because p=mv only applies for v<<c
this has already been said before

And what does the cosmological constant have to do with anything?
There is a lot of experimental evidence for relativity
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MRLX69
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#76
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(Original post by AntiMagicMan)
This is getting to be another quack science thread. Why on earth do we have to waste out time talking about very old problems. The concept of light having momentum has been around since Maxwell's time, just look at his equations, they state that electromagnetic waves have momentum.
Why can't we just debate about it for ourselves? :aetsch:

I'm reading some of maxwell's things at the moment... I'm getting a good idea of why light has momentum but no rest mass..... but it's all very odd
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Newton
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#77
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Yes but then is that not because all of E-M waves are made out of photons... This will just keep going around in circles...

Newton.
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jpowell
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#78
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No, it isn't because light is made of photons. The momentum of light can be derived using purely classical physics.

Sorry to say this MRLX69, but there isn't much here to debate. There is only stuff that you can learn. I can teach you the modern ideas about light, that they have no rest mass but momentum, I could even show you how to classically derive the momentum of an electromagnetic wave. But you cannot really debate it, as it is all stuff that has been figured out a long time ago.
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MRLX69
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#79
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(Original post by AntiMagicMan)
No, it isn't because light is made of photons. The momentum of light can be derived using purely classical physics.

Sorry to say this MRLX69, but there isn't much here to debate. There is only stuff that you can learn. I can teach you the modern ideas about light, that they have no rest mass but momentum, I could even show you how to classically derive the momentum of an electromagnetic wave. But you cannot really debate it, as it is all stuff that has been figured out a long time ago.
yea... I just read it up, lol......

By the way, light isn't made of photons. It's just a model.
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john !!
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(Original post by Newton)
Have you not read what I just said if for relativistic quantaties dealing with particles travelling at the speed of light p=(E/c) and E=m(c^2) then p=mc=mv but v=c.

He mislead the world. What evidence except that of light bending during an eclipse, in the 1920s I think.

Newton.
same to you. It was said before that
E=mc^2 is a simplification in the special case when v=0

there is also new evidence, read a physics magazine or something, the theory predicts the mass of the earth will cause a drag in spacetime which was detected a few months ago on a satellite. there have been numerous testings of special relativity, including equivalent atomic clocks, one on a fast moving plane and one on the ground. the clocks did not agree after the experiment. and then there was the michleson-morley experiment that did away with the ether, the opposition theory.
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