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 ...

Tracking time is one of those things that seems easy, until you really start to get into the details of what time actually is. We define a second as 9,192,631,770 oscillations of a cesium atom.

Time dilation, a captivating concept embedded in Einstein’s theory of relativity, has been experimentally validated on Earth. With the use of ultra-precise clocks, scientists have been able to ...

Despite more than a century of efforts to show otherwise, it seems Albert Einstein can still do no wrong. Or at least that’s the case for his special theory of relativity, which predicts that time ...