PCMag editors select and review products independently. If you buy through affiliate links, we may earn commissions, which help support our testing. Much like Amazon Prime Day, Stuff Your Kindle Day ...

(gentle music)(gentle music)(keyboard clicking)(keys jingling)(switch clicks)(subway rumbling)(subway hisses)(announcer speaking in foreign language)(alarm chimes ...

Cosmic speed limits can be a major inconvenience but they've rarely stopped science fiction in its tracks. When it comes to space travel, Albert Einstein's theory of relativity is a major ...