In the late 60s, the Byrds recorded a Bob Dylan song whose refrain reminds of a recent gedanken (thought) experiment proposed by physicists at Dartmouth and Santa Clara University. The line from the song is “Ah, but I was so much older then, I’m younger than that now.” I commend the rest of the song and the lyrics to you as it is as timely today as in 1968. But I digress.
Einstein famously postulated the “twin paradox” where one twin gets on a spaceship and, after traveling close to the speed of light, returns younger than his/her other twin who remained behind. This effect was shown in the movie “Interstellar” although the time dilation was experienced because of a black hole gravitational field rather than light-speed travel.
The new experiment involves not twins, but a pair of quantum atomic clocks. If you start the clocks simultaneously then according to Einstein, the one that travels close to the speed of light should return with an earlier time than its twin clock. But according to Quantum Mechanics, it doesn’t. Instead, it returns in a “superposition” of states. It is both the same time AND the earlier time as its twin clock. If we, humans, could pull this off on our macroscopic scale, we would never be late for anything.
This is one of the few solid connections between Relativity and Quantum Mechanics. The mathematics is daunting. The conclusions are bizarre. But then, there’s hardly anything about our world today that seems “normal” anymore. Maybe bizarre is the new normal.