A spacecraft traveling at 99 percent the speed of light toward Alpha Centauri would cross 4.3 light-years in what feels like months to its crew, while decades tick by on Earth. That asymmetry is not ...

A pair of scientists from the UK recently published a pre-print research paper discussing the theory of a universe with no beginning. Imagine it: our universe has always existed. The Big Bang either ...

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com. Why does time change when traveling close to the ...

Physicists have transferred time and frequency information over a distance of more than 100 km in free space, far exceeding the previous record. The technique, which makes it possible to synchronize ...

The principle of relativity, as initially described by Galileo, posits that the laws of physics remain consistent regardless of an observer's relative motion. Einstein's special relativity ...