All massless particles travel at the speed of light, including the photon, gluon and gravitational waves, which carry the electromagnetic, strong nuclear and gravitational interactions, respectively. Particles with mass must always travel at speeds below the speed of light, and there’s an even more restrictive cutoff in our Universe. (NASA/Sonoma State University/Aurore Simonnet)

The Universe Has A Speed Limit, And It Isn’t The Speed Of Light

Nothing can go faster than the speed of light in a vacuum. But particles in our Universe can’t even go that fast.

Ethan Siegel
Oct 16, 2018 · 7 min read

When it comes to speed limits, the ultimate one set by the laws of physics themselves is the speed of light. As Albert Einstein first realized, everyone looking at a…