speed of light

How fast is gravity?

Gravity is the most familiar of the known forces, but it seems to be eternal and unchanging. However, scientists believe that gravity moves with a specific speed. In this video, Don Lincoln describes a fascinating observation that definitively measures the speed of gravity.

Pound for pound, of all the particles with mass, neutrinos are the fastest, almost traveling at the speed of light … but not quite. So exactly how fast are they? Neutrino physicist Kirsty Duffy and Durham University neutrino theorist Jessica Turner discuss how fast the elusive neutrinos can travel.

Physics students often ask how it is that a massless photon can have momentum. In this video, Don Lincoln shows that the question arises from a misuse of equations and also shows that, when you think about it, it’s not surprising at all.

Traveling faster than light is one of humanity’s dreams. Sadly, modern physics doesn’t cooperate, but there are examples where it really is possible to travel faster than light. Don Lincoln discusses ways in which the universe breaks the ultimate speed limit.