A tachyonic antitelephone would allow you to phone someone back in time. Because tachyons go faster than the speed of light, they would travel back in time to before you ever made your phone call.

You can think of it like mailing selfies home from long, round-trip vacation. Just as the spaceship was traveling faster than light, you are traveling faster than snail-mail, so you beat some (or ...

In 1907, the old smartypants dreamed up something now known as a “tachyonic antitelephone,” a device using tachyons — faster-than-light particles so imaginary that even theoretical ...