Gravity and time

This announcement was really exciting for me. Scientists now have proof that Einstein’s time dilation effect works at the quantum level, not just in macroscopic space. Even better, it’s time dilation due to gravity, not velocity.

Everyone (OK, lots of people) is/are familiar with the concept that if I travel at lightspeed for a few years of my subjective time and return home, thousands of years may have passed at home. That’s been a science fiction staple since the 60s. But fewer people are aware that Einstein’s general theory of relativity also predicts that time passes differently in gravity wells due to the warping of space-time. The larger the gravity differential in frames of reference, the larger the time delta. The example the Quanta article uses, that living on the top of Everest will make you age a tiny bit faster than living at sea level is a good one. Time moves more slowly at the bottom of a gravity well.

This was a big part of the story in the movie Interstellar (one of my top 10 movies ever), when part of the crew traveled to a planet with intense gravity due to its proximity to a black hole, and the hours or so they spent there meant that their crew mate who stayed on the ship had aged 30 years when they returned. (They didn’t really model the gravity very well in the film; it would have smashed them like a bug…so some hand-waving was involved.)

But back to reality. The method used to measure gravity’s effect on quantum processes was ingenious. They used a laser to excite a tiny cloud of strontium atoms, so that their electrons would change quantum states predictably. By measuring the frequency (time) of each state change at the top and bottom of the cloud, they could see and measure the effects of gravitic time dilation.

The mysterious nature of gravity and its role in how the universe works is one of my favorite subjects. It’s great to see a little of the mystery peeled back.