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How Long is a Day on the Sun? The Answer is a Hot Mess

A day is measured by how long it takes “a planet to spin around and make one full rotation.” On Earth we know that is roughly 24 hours, but within our own solar system a day can be as short as 10 hours, like it is on the fast-spinning Jupiter, or an interminable 5,832 hours, like it is on slow-moving Venus (that’s 243 days here on Earth).

But what about the big yellow thing that keeps us warm—the Sun? How long is a day there? The answer is simple: “It depends.” Oh, wait, that’s not simple at all.

Fortunately for us, MinutePhysics is here to explain why, and it turns out the answer to that question is all a matter of perspective.

If a day is how long it takes for the Sun to “come back overhead,” that only matters if you are standing on it upside down, which would make the days “infinitesimally short.” If you look at it from the perspective of neighboring stars, and how long it takes the sun to spin back around to them, it matters where on the sun you are talking about. The sun, “a big ball of flowing, gassy plasma,” is so big that at its equator a day would be about 24-and-a-half earth days, but at its slower moves poles it would take about 34 earth days.

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Even if we just assign the sun’s length of day at the earthly time of 86,400 seconds it would still be different, coming in at an extra .2 seconds thanks to gravitational time dilation.

So what’s the best answer? The one that judges how long a day would be if you were actually on the sun, because, relatively speaking, it’s the easiest answer to understand: one day there would equal your last day.

What other seemingly simple question would you like MinutePhysics to tackle next? Tell us today in the comments below.

Image: MinutePhysics

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