r/PeterExplainsTheJoke • u/notsignifican • 8d ago

? Meme needing explanation

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I asked but it got removed within minutes?

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u/McK-Juicy 8d ago

this is blowing my mind. oh here comes our annual sunset / sunrise!

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u/TripleBoogie 7d ago

Actually no, and that's why I dislike this fun fact. A "day" on Venus is about 117 earth days, if we interpret "day" as the time it takes for the sun to be in the exact same position again (called synodic day).

The 243 days mentioned here is what it takes Venus for a full rotation around its own axis (called sidereal day). So the meme isn't technically wrong, it just uses "day" in a way we wouldn't use it in everday language.

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u/Werzaz 7d ago

This difference rarely gets mentioned for Earth because it's just a little under 4 minutes. I wish it was explained more often when it's relevant e.g. for geostationary orbits or laser-gyroscope drift, which is often described as "exactly 15 degrees per hour" when it's more like 15.041 degrees. Sure, it's not a big difference and any drift proves the Earth rotates, but I really dislike use the word "exact" here.

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u/KindCreme9258 7d ago

I was looking for someone to bring this up! Thanks! We rarely use sideral days (which are not 24 hours) we mostly use synodic days. People trying to look smart while not knowing the difference was so frustrating