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Mass energy equivalence 
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#1
Jun1211, 07:47 AM

P: 9

I understand energy mass equivalence, but when mass is changed to energy what happens to it's gravitational field?



#2
Jun1211, 08:05 AM

Sci Advisor
Thanks
P: 4,160

Nothing. Stays the same. Whatever form the 'energy' takes: kinetic energy of the decay products, photons, etc, all those things are sources of gravity also. At least initially until things fly apart, the gravitational field will be the same.



#3
Jun1211, 08:07 AM

Mentor
P: 17,330

Mass is not the source of the gravitational field. The source of the gravitational field is the stress energy tensor:
http://en.wikipedia.org/wiki/Stress%...3energy_tensor The mass only gravitates in the first place because it has a lot of energy. 


#4
Jun1211, 09:42 AM

PF Gold
P: 4,087

Mass energy equivalence
I think the radiation would have to be kept in a perfectly reflecting box, or the gravitational field would change for a nearby observer. If the matter and antimatter are in the box, then anihilate, the field produced by the box and contents would not change. Pedantic is my middle name.



#5
Jun1211, 11:26 AM

Emeritus
Sci Advisor
PF Gold
P: 5,597

In GR, there is no uniquely defined measure of massenergy that is conserved in all spacetimes. As DaleSpam pointed out, it's the stressenergy tensor that is really fundamental in GR, not massenergy. However, there are scalar measures of massenergy such as ADM and Bondi mass that are conserved in specific types of spacetimes, such as asymptotically flat spacetimes. The distant, static field of a system in an asympotically flat spacetime is determined by its ADM or Bondi mass in exactly the way you would think. ADM and Bondi "mass" include both mass and energy (because otherwise they wouldn't be conserved). So the short answer to your question is yes if you're talking about the distant, static field, in an asymptotically flat spacetime, and no otherwise  which is not that different from the Newtonian answer. Ben 


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