# What does mass-energy allow a particle to do

The mass energy of a photon is 1*10^-18 eV/c^2
The mass energy of an electron is .5 MeV/c^2
The mass energy of an up quark is 2.3 MeV/c^2
The mass energy of a down quark is 4.8 MeV/c^2

I don't understand what these quantities enable to the particle to do. If we know these quantities then what can we infer about the particles behavior?

Orodruin
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The mass energy of a photon is 1*10^-18 eV/c^2

This looks like an experimental upper bound. Photons are assumed to have zero mass.

Particle masses can be used in several fashions, for example to see if a decay or a particle reaction is kinematically allowed or to compute the trajectory of a particle in an electromagnetic field.

Particle masses can be used ... to compute the trajectory of a particle in an electromagnetic field.

Could you go into more details? Are you saying that mass-energy can be used to predict motion? If a down quark nears an up quark what quantities predict its movement? Does a photon have zero mass or zero mass-energy? I'm pretty sure that the photon only interacts with an electron. If so what happens when a photon near an neutrino or a quark?

Staff Emeritus
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I think you need to ask a more specific question. Suppose I asked this:

The mass of a fly is about .01 g
The mass of a herring is about 500 g
The mass of a giraffe is about 1500 kg
The mass of a sperm whale is about 13000 kg

I don't understand what these quantities enable to the animal to do. If we know these quantities then what can we infer about the animals' behavior?

You probably wouldn't know where to begin, right? Same problem here.

Dale
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I don't understand what these quantities enable to the particle to do.
It lets them do the same thing as any other form of energy: work.