# If the planet were smaller would it still be possible to have a 24 hour day?

Given a hypothetical planet smaller than earth but otherwise the same, is it possible to still have a 24 hour day... as in make it so that the planet still takes 24 hours to make a complete rotation.

Asking it a different way for more clarity....

If the size of the planet is different but I still want a 24 hour day, what else (if anything) would I need to change to my hypothetical planet to make a 24 hour day possible. Or can I simply change the rotational speed of the planet without having to change anything else... In other words, would changing the rotational speed cause other problems (gravitational shifts, weather problems, etc.) or can I simply have a smaller planet and set the rotational speed at whatever I need to ensure the 24 hour day without any other consequences.

If there is a consequence to adjusting the rotational speed, is there anything that can conteract that (such as the presence of another moon or different distant from the sun or other factors.)

Update:

To add more to this, my only goal is to make a planet that has 24 hours in the day and is smaller than earth... I'm shooting for the same gavitational effect as earth (in other words I don't want people bouncing around lol or having superhuman strength or anything).... from what I'm seeing so far, if I adjust mass and some other nominal factors this shouldn't be a problem. I'm guessing that is correct but if anyone else has any insight, please continue to post.

Update 2:

oh and of course I want as close to the same "human friendly" atmosphere and environment as possible.

Relevance

Hypothetically, all you would have to do is change the rate of spin. However, the rate of spin will determine the centripetal force exerted against anything on the planet - more spin less effect of gravity.

Whether there will be a change in the magnetosphere, depends up the composition and relative mass of the planet.

Play around with these concepts for a while. These will not be the only factors that would affect gravity, etc.

Really the Earth is almost perfect and the more you mess around with stuff the less habitable it becomes for humans.

(but not neccesarily for other life forms)

If you change factor [blank] more and more, the planet will still be tolerable (sometimes suprisingly), but eventually you can't live on it anymore.

So a planet probably can't get too small or it will lose atmosphere, due to low gravity.

Mars is half the size of Earth. And has almost no air.

Who knows, maybe if you were omnipotent you could add air and it just might stay, but we can't do that experiment.

It'd still be a cold planet, but with oxygen, greenhouse gasses, and water.

We have so few examples that we can't tell. Titan is even smaller than Mars but has a thicker atmosphere than Earth. It's also cold. So maybe the coldness helps keep the atmosphere.

But what about Venus, Venus' atmosphere is 92 times as thick as Earth, and it's 850 degrees. How did a hot Earth-sized planet keep so much air?

So you can't say for certain. Maybe volcanos can replenish the atmosphere. It'd probably be a hostile atmosphere though (again hostile for humans)

Assuming you could get a 24-hour day Mars-sized planet in Earth orbit with breathable air then what?

Well, gravity would be low (the spinning only affects it a few percent). You'd only weigh about 40%.

The surface-area to mass is much greater. Maybe that would affect the weather.

Could it have a magnetic field? Maybe if it's core is iron like a bigger Mercury (which would also increase the weight and gravity)

Could that planet be as habitable Earth?

Ask someone who knows better, I'm npt sure.

Source(s): Even a 24:37 hours Martian day might trainwreck people's circadian rhythm after awhile.
• Anonymous

YOu need to remember, earth has only had a 24 hr day for roughly 200-250,000 years. Before that, we had a day that was 22.5 hours long.

During the jurassic period, the moon was 2x closer to the earth then it is today, this caused gravitational drag on the planet, to speed it up. The moon retreats further from the earth at about an inch a year, thus slows the planets rotation down . So in another 1-4 million years years (+-) the earth will will have a day that maybe 26hrs long,

And if we havent wiped ourselves off the planet in another 1-3 billion years, were going to lose the moon.

Source(s): stephen hawkings, universe in a nutshell

Just change the rotational speed to get a 24 hour day. The mass of the planet will affect the gravity, though. I assume you want a world where humans are stronger than natives. Be aware that that advantage would disappear in less than a year. The body will adjust and muscle tone will be lost unless the human you are using works out a lot.

Source(s): Science fiction writer with several published books.
• Anonymous

Rotational speed is independent of the planet's size, although in our solar system the large planets tend to rotate faster. Mars is considerably smaller then Earth and takes 24 1/2 hours to rotate.

The centripetal effect from rotation is not significant compared to the gravitational field of a planet.

• Anonymous

Certainly. Venus is the same size and mass as the earth, and its day is far different from 24 hours. You can posit any rotational period that you please.

yes. but it may rotate very slowly!

• Leo H
Lv 4