Weirdly, spaceships have no direct way to gauge their own speed. Luckily, we can use some physics tricks to figure it out.

If you watch a NASCAR race closely, one moment always stands out for how quickly it happens: the pit stop. Cars dive onto pit road, a crew of specialists jumps over the wall, and seconds later the ...

You know your chronological age. But do you know your biological age? For the former, you just count the number of candles on your birthday cake. But for the latter, a newly trendy measure of how fast ...