Seraph062 t1_j3kn3ic wrote
Reply to comment by quarter-water in TIL Pluto hasn't completed an orbit around the sun since its discovery. Pluto's orbit takes about 248 years, and Pluto was discovered in 1930. by irbinator
> a day (one complete rotation) is 175 Earth days lol
A day isn't really a complete rotation.
A complete sidereal rotation (i.e. the time it takes to complete a single 360 degree rotation) on Mercury is about 59 Earth days.
However 'a day' is generally measured with respect to the parent star, and since Mercury is moving around the sun that represents a moving target, and it takes 175 Earth days for the sun complete one cycle in the sky (e.g. local noon -> local noon).
quarter-water t1_j3lm3a4 wrote
You're right, I added the parts in parenthesis after but it's not totally correct. The 175 day is how long someone on Mercury would feel like "a day" ie from noon to noon.
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