[monstertank]

Obviously gravity works on particles to condense into stars, which create light...so I'm guessing it's not talking about that?

[jacquesm]

You added 'particles'.

[joadha]

The authors added "electromagnetic field", which also happens to involve particles.

[jacquesm]

To create one, yes. But to propagate it, no.

[computerfriend]

Photons are particles.