![Image source: York University The Troubles with Times Image source: York University](http://www.timeone.ca/wp-content/uploads/2013/06/078-the-troubles-with-times.jpg)
Image source:
York University
An astronaut who travels to the nearest star and back arrives home younger than a stay-home twin. A round trip in ten years finds that the twin has aged by thirty. Atomic clocks with circumglobal tickets show a relatively smaller but precisely-as-predicted slowdown. It’s a whole new kind of jet lag.