I've been told that as a particle reaches the speed of light, the energy of the particle adds to the mass of the particle. I thought this would be a good place to start asking my questions, so here it goes: Would this apply to large objects as well? Why does energy add to mass?

The mainstream view is more the other way round: Mass adds to the total energy. This is true for any speed of an object and indeed applies to large objects, too. But since many processes involving large objects leave the total mass constant, this is of practical irrelevance in many cases. Asking for a "why" is not exactly very physical. It seems to be a fact, so any argument against this would merely prove that nature cares little about human reasoning. If you mean "why" in the sense of "how can I make sense of it?" then I recommend considering mass as a form of potential energy.

 

EDIT: And btw, this has nothing to do with Quantum Theory.

Edited October 28, 201213 yr by timo

EDIT: And btw, this has nothing to do with Quantum Theory.

 

Agreed. Moved to the relativity sub-forum.

The mainstream view is more the other way round: Mass adds to the total energy. This is true for any speed of an object and indeed applies to large objects, too. But since many processes involving large objects leave the total mass constant, this is of practical irrelevance in many cases. Asking for a "why" is not exactly very physical. It seems to be a fact, so any argument against this would merely prove that nature cares little about human reasoning. If you mean "why" in the sense of "how can I make sense of it?" then I recommend considering mass as a form of potential energy.

 

EDIT: And btw, this has nothing to do with Quantum Theory.

Bolded mine

 

This is how I make sense of it:

if I observe an object, say a planet, getting away from me at near the speed of light, I should observe its mass increasing. And reversely an observer on this planet should observe that the Earth is increasing in mass.

Edited October 28, 201213 yr by michel123456