When you look up at the night sky, you’re seeing the long-ago light from distant stars. But how can you know how far away they really are? You can’t exactly roll out a measuring tape. Luckily, there’s ...

Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. One of the most ...