Nuclear weapons, climate change and biological threats are the biggest concerns.

From time to time, you might notice a shot of a clock in a movie. In a film like "Back to the Future," they're key to the plot; lightning strikes the clock tower at exactly 10:04 p.m. But often, ...

When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. The smallest conceivable length of time might be no larger than a millionth of a billionth of a ...

Like a metronome that sets the tempo for a musician, a fundamental cosmic clock may be keeping time throughout the universe. But if such a clock exists, it ticks extremely fast. In physics, time is ...