Science Reader Question: What’s a Few Minutes Between Friends?

Photo of satellite orbiting the Earth

Without relativistic time adjustments, our satellites would get out of sync with receivers on the ground. (Photo by Unsplash)

HC asks:

How would you describe time?

Last week I went a bit esoteric, musing that time is the feature of the universe that makes forgiveness necessary. Now let’s try something a bit more basic. Time is the feature of the universe that we measure with clocks. As banal as that statement may be, it is possibly the only statement about time one can make with certainty. Time allows us to decide which events come before which other events and how rapidly or slowly the second followed after the first. And since time is associated with measurement, it’s tempting to measure ourselves with it. Did we spend our time well? Are we managing it as efficiently as possible? But if we measure our worth with time, what happens if not everyone agrees on the same measurement?

Durations, as it turns out, are not universally agreed upon. Under the right conditions, I could measure the time between event A and event B as 1 minute while you measure that same interval as 2 minutes. We would observe the exact same events, our watches would both work correctly, and yet we’d still get different answers. Fortunately, those conditions are pretty far removed from what we normally experience. You’d have to be moving really fast, or experiencing big differences in gravity, or trying to measure very tiny time intervals. People who move no faster than 100mph or so on the surface of the Earth and who only care about differences of minutes or seconds will never notice. But GPS satellites notice. They need to be synchronized with earthbound receivers for the whole system to work. And they travel fast enough and under different enough gravity while trying to synchronize time so precisely that if we didn’t account for the differences predicted by Einstein’s relativity theories, we’d all be lost. So as counter-intuitive as it seems, time is not absolute.

Still, that doesn’t mean anything goes. One other consequence of Einstein’s theory is that we still agree about the speed of light, no matter how fast we are going. The effects of gravity make things slightly more complicated, but even then lightspeed still represents an absolute limit on how fast matter can travel. I choose to employ these relativistic realities as a reminder of how I ought to measure my worth. Time is not the ultimate arbiter of my value; I am measured against the Light of the world.

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Andy Walsh

Andy has worn many hats in his life. He knows this is a dreadfully clichéd notion, but since it is also literally true he uses it anyway. Among his current metaphorical hats: husband of one wife, father of two elementary school students, reader of science fiction and science fact, enthusiast of contemporary symphonic music, and chief science officer. Previous metaphorical hats include: comp bio postdoc, molecular biology grad student, InterVarsity chapter president (that one came with a literal hat), music store clerk, house painter, and mosquito trapper. Among his more unique literal hats: British bobby, captain's hats (of varying levels of authenticity) of several specific vessels, a deerstalker from 221B Baker St, and a railroad engineer's cap. His monthly Science in Review is drawn from his weekly Science Corner posts -- Wednesdays, 8am (Eastern) on the Emerging Scholars Network Blog.

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