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So I'm not sure this is possible but I was hoping someone might be able to figure out a way for it to work.

My planet is smaller than earth. I'd say about 75% the size. However for plot reasons, I'd like the days to be 24 hours long and the years to be close to the same length as an Earth year.

I haven't exactly defined the size of the planet or its distance from its sun so these things are flexible.

So is this possible?

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  • $\begingroup$ Yes. Nothing fancy required at all. Generally speaking, the planet size does not affect its day or year. $\endgroup$ – Joe Kissling May 20 '17 at 3:17
  • $\begingroup$ Really? I thought a smaller planet would mean that it would take less time to do one revolution on its axis (thus the day would be shorter). $\endgroup$ – Olandir May 20 '17 at 3:36
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    $\begingroup$ For your purposes, the size of the planet will not influence its rate of rotation. If you want this mini earth to have a 24 hour day and a year that is 365 days long, there is no issue whatsoever. For your story make it so. $\endgroup$ – Joe Kissling May 20 '17 at 3:39
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    $\begingroup$ 75% of the mass, or 75% the radius/diameter/circumference? (Not that it matters for the question at hand.) $\endgroup$ – RonJohn May 20 '17 at 4:58
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    $\begingroup$ @a4android - if orbiting a more massive star an orbit at the distance of Mars but twice the speed should be possible, no? If you can adjust both the mass of star and planet you can find a combination allowing any desired combination of distance between star and planet and year length. $\endgroup$ – Willk May 20 '17 at 14:50
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So is this possible?

Yes, your day/night lengths are due to rotation not size, years are reliant on orbit. Mercury is much smaller than Earth but has an 88 (earth days) year. But its days are 1,408 hours long if you count using Earth hours.

Basically a year is how long the orbit of the sun takes and a day is how fast your planet rotates in relation to the Sun.

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