
#1
Jan713, 08:06 PM

P: 915

Is there anything lighter than light?
A photon has zero rest mass. However it has energy which is equivalent to some mass (?) Angular momentum is energy (?). The angular momentum of, say, a photon would have some energy. If we were to convert (mathematically) that energy into mass, what would the value be? (in relation to the relativistic mass of a photon) 



#2
Jan713, 11:34 PM

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#3
Jan813, 01:31 AM

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It's not terribly clear what you're asking when you ask if "momentum has mass". The best answer is probably that momentum and mass are different things, but they are both related, in a general way, to gravitation. Like forks and spoons are related , perhaps.
But would we ask "do forks have spoons"? I don't think so :(. 



#4
Jan813, 02:30 AM

P: 492

Does momentum have mass? 



#5
Jan813, 04:54 AM

P: 492

http://en.wikipedia.org/wiki/Photon 



#6
Jan813, 05:13 AM

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A photon may also have the plain old orbital type of angular momentum.




#7
Jan813, 07:26 AM

P: 5,634

Wikipedia says this: So if you pick some color light of your choice, you can figure out what fraction of it's energy is from 'spin'..... total energy is hc/λ so it looks like h/2∏ divided by hc/λ........so the 'h's' cancel ... San K : I have never thought about this issue before, so before you accept this answer, let's wait and see if anyone has corrections to make. 



#8
Jan813, 07:46 AM

P: 5,634

oops...forgot:
then yes, the graviton. How about the 'new' Higgs boson?? 



#9
Jan813, 08:07 AM

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Energy and angular momentum are separate concepts, gentlemen. To ask how much energy is due to a particle's spin is devoid of meaning!
Is the energy of a photon "small"? No. For it is totally dependent on rest frame  by suitable Lorentz transformation you can make it as small as you like, or as large as you like. Exactly the same thing applies to the (hypothetical) graviton. So its energy is sometimes less than, and sometimes greater than, a photon's energy. 



#10
Jan813, 08:07 AM

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#11
Jan813, 12:31 PM

P: 5,634

Oh yea,duh, good catch Bill K....
The link between momentum and energy is their effect on gravitational attraction...as in 'stressenergymomentum....' tensor So maybe SanK's question could be answered via a gravitational impact approach??? Compute the SET with and without angular momentum ?? 



#12
Jan813, 03:15 PM

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#13
Jan813, 03:41 PM

P: 5,634

Note also that momentum is a vector and energy a scalar....not comparable....
but both do have an effect on gravitational attraction....as does, for example, pressure... so there IS an intrinsic relationship via GR..... 



#14
Jan813, 05:20 PM

P: 832

Energy isn't a scalar, but just one component of a vector.




#15
Jan813, 05:23 PM

HW Helper
P: 3,337

Also, for a photon, its energy is equal to its relativistic mass, which is also equal to its momentum. (in natural units). So, you can see that in fact, the angular frequency of the photon is equal to the momentum (and also equal to the relativistic mass). 


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