What if a day were only slightly less than an hour?

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naturalplastic
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17 Jul 2019, 4:03 pm

The earth spins around on its axis, and makes one complete turn every 24 hours.

That means that if you are standing at the Equator, you are moving at almost one thousand miles an hour even if you are "standing still".

If the earth made complete turns in only 55 minutes ( day and night day and night every fifty five minutes) a person at the equator would be moving at 25 thousand miles per hour.

That means that you would be moving at escape velocity. The speed NASA has to give to rockets to get them into interplanetary space.

In fact that is part of why NASA does it rocket thing in the tropical state of Florida: the proximity to the equator gives its rockets and extra boast due to the earth's spin.


So my question is this: what if the earth did spin at 25 times its present speed? Would folks in Quito Ecuador, and in Java, go flying off into space?

And would boulders and soil at the equator also go flying off into space?

Would the whole planet start to dismantle itself? The matter right at the equator would be ejected, making the whole planet progressively less massive, giving it progressively less gravitional pull, progressively reducing escape velocity, casuing stuff progressively farther from the equator to also go flying, and ..so on... until the whole planet disappeared?



SaveFerris
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17 Jul 2019, 4:41 pm

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naturalplastic
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30 Jul 2019, 7:13 pm

SaveFerris wrote:
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That's acceleration. Not speed.

Obviously if the Earth decided to start spinning faster today- then that would take acceleration. We would all be even worse off then those test pilots in those film clips.

But if the earth had always spun 25 times faster than it does now we wouldn't "feel" it because you don't feel speed. You can only feel changes in speed.

But if the earth spun 25 times faster than it does it would be spinning at escape velocity at the Equator.



quite an extreme
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01 Aug 2019, 8:04 pm

naturalplastic wrote:
But if the earth spun 25 times faster than it does it would be spinning at escape velocity at the Equator.

I could easily sleep more then a week then. :mrgreen: But I guess the earth would be splitted and a second moon created.


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20 Aug 2019, 9:11 am

I think it would depend on whether or not it had always been at the speed, or if we were to transition form our current spin speed to a speed 24 times faster.

If we started off at our current speed, then accelerated to 24 times the speed, you would definitely see some major disruptions (the extremity of which determined in large part by how quickly we transition to our new 24x speed).

If we had always been at that speed, then there wouldn't be things like sudden expulsions of mass into space, as the relative speed of everything else would remain the same. For example, you can stand up and walk around an an airplane traveling at 500 MPH faster than the earth is rotating, and experience little ill effect (so long as you do so after the plane has reached its new 'normal' speed). This is precisely the principle of relativity.

We would experience much more centripetal force, kind of like how they create artificial gravity on space stations by spinning them. Probably Earth it would be similar to a higher gravity planets if it had consistently been spinning 24 times faster than it does now for a long time.

As an aside, to achieve this new speed, there would need to be massive changes to the surrounding and internal physical bodies, as our rotational speed is determined by the angular momentum earth has had since creation, is influenced by gravitational forces, has been spun up faster by impacts, and is also influenced by the movements of earth's inner core.



naturalplastic
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07 Sep 2019, 7:22 am

TheOther wrote:
I think it would depend on whether or not it had always been at the speed, or if we were to transition form our current spin speed to a speed 24 times faster.

If we started off at our current speed, then accelerated to 24 times the speed, you would definitely see some major disruptions (the extremity of which determined in large part by how quickly we transition to our new 24x speed).

If we had always been at that speed, then there wouldn't be things like sudden expulsions of mass into space, as the relative speed of everything else would remain the same. For example, you can stand up and walk around an an airplane traveling at 500 MPH faster than the earth is rotating, and experience little ill effect (so long as you do so after the plane has reached its new 'normal' speed). This is precisely the principle of relativity.

We would experience much more centripetal force, kind of like how they create artificial gravity on space stations by spinning them. Probably Earth it would be similar to a higher gravity planets if it had consistently been spinning 24 times faster than it does now for a long time.

As an aside, to achieve this new speed, there would need to be massive changes to the surrounding and internal physical bodies, as our rotational speed is determined by the angular momentum earth has had since creation, is influenced by gravitational forces, has been spun up faster by impacts, and is also influenced by the movements of earth's inner core.

I already addressed some of this above.

You don't feel speed. You feel acceleration/deceleration.

Not only can you walk around a jet airliner moving at 500 mph, a "stationary" person can walk around the airport in Quito Ecuador (right on the Equator) while moving at over a 1000 mph (because that's how fast the Earth is spinning at the Equator. AND... the earth as a whole is moving around the Sun at the speed of 60 thousand miles per hour. So the "stationary" person at the airport is moving in all kinds of directions - and each one at a higher velocity than a jet airliner can move.

So the question is a bit arbitrary. If God decided to ACCELERATE the earth's spin that much right now, and flicked the switch...we would all die from the upheavels that that much acceleration would cause.

But let say God did this a million years ago. And for the shank of that time earth has spinning at a normal steady rate of once an hour.

Humans living on earth (even at the equator) would not feel the speed anymore than we feel the earth spinning now.

But even so...if you were at the Equator you might fly off into space. along with boulders, and soil, etc., because everything at the equator is moving at escape velocity.



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23 Sep 2019, 12:50 pm

there is a way to figure the centrifugal force but i don't have the math handy just now.

one time i actually re-did hal clement's calculations for his famous "mission of gravity" in which a solar day (on "mesklin") is less than 18 minutes long. i found the planet would start to lose mass at the equator & it would actually have to rotate less rapidly than that, in order to remain stable as a solid object.

Image


definitely any such body could not be spherical while made of regular planet-materials as we know it. aside from that (& gravity being considerably different from the pole to the equator, as on mesklin), the distinction between "day" & "night" would become relatively meaningless (somewhat like the difference between direct sunlight & shade, as it is for us: only occasionally a matter even of notice). i think the gravity not being the same from one place to the other would be the larger concern.


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28 Sep 2019, 3:24 am

When I read the title I thought this would be about the biological effects of living on a small planet with a 1-hour day-night cycle.

This question is less interesting to me. I don't know the answer but I do know that it is more complicated than the initial answers make out.

A simple answer is yes, if the Earth rotated at that speed we would be weightless. Spaceships can generate artificial gravity by rotating, but that's because you're inside the spaceship and being pushed out. The same effect occurs on Earth, but we are on the outside being pushed out. You are slightly lighter at the equator than at the poles.

There are more factors to consider though. Firstly, as graywyvern suggests, there are lots of implications for the planet itself. Secondly, "escape velocity" assumes no other forces act upon the object, but in this situation there would be considerable drag from the air. Thirdly, I'm sure there are a lot of relativistic considerations that I cannot properly get my head around. I know the escape velocity of the Earth depends on which way you fire your rocket - if you go against the Earth's rotation (as you always would) then it is about 25,000mph, but going with the Earth's rotation it is more like 26,000mph.



naturalplastic
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28 Sep 2019, 11:35 am

The_Walrus wrote:
When I read the title I thought this would be about the biological effects of living on a small planet with a 1-hour day-night cycle.

This question is less interesting to me. I don't know the answer but I do know that it is more complicated than the initial answers make out.

A simple answer is yes, if the Earth rotated at that speed we would be weightless. Spaceships can generate artificial gravity by rotating, but that's because you're inside the spaceship and being pushed out. The same effect occurs on Earth, but we are on the outside being pushed out. You are slightly lighter at the equator than at the poles.

There are more factors to consider though. Firstly, as graywyvern suggests, there are lots of implications for the planet itself. Secondly, "escape velocity" assumes no other forces act upon the object, but in this situation there would be considerable drag from the air. Thirdly, I'm sure there are a lot of relativistic considerations that I cannot properly get my head around. I know the escape velocity of the Earth depends on which way you fire your rocket - if you go against the Earth's rotation (as you always would) then it is about 25,000mph, but going with the Earth's rotation it is more like 26,000mph.


I think that you have it backwards. Escape velocity is the same regardless of whether its against or with the earth's rotation, but you get a free boost if you go with rotation. At the equator you are already moving at a thousand miles per hour. So you only need to accelerate the space craft to 24K mph, and you let the earth do the rest. And that is why NASA shoots rockets at Cape Canaveral in Florida, and not in New England. Florida doesn't spin as fast as the equator, but its faster than the rest of the more northerly US.

Relativity? Relavitity is only a factor when youre talking about significant fractions of the speed of light. We are talking about a mere 25K mph. Or less than eight miles a second. Thats less than one twenty thousandth of the speed of light. So Einstein can be ignored because the effects of relativity would be negligible at that low a speed.

The atmosphere does create drag that keeps objects from escaping. A hunting rifle and the sixty foot long guns of the Battleship Missouri both have the same muzzle velocity (half of a mile a second) but very different ranges (one mile, and 23 miles) because drag with the air effects a small bullet more than it effects a 2700 pound shell as long as a human is tall.

But in our scenario the air itself is being whipped around at escape velocity, and its getting saturated with soil and rocks and water flying upward.



quite an extreme
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01 Oct 2019, 4:00 pm

naturalplastic wrote:
But in our scenario the air itself is being whipped around at escape velocity, and its getting saturated with soil and rocks and water flying upward.

That's right. Beside of this the earth would be flattened and this would cause an equatorial velocity beyond the escape velocity. This would cause a lot of stuff to escape and surround the earth first but form a second moon afterwards once the tidal forces brought the material to higher orbits. Just my imagination of this ...


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naturalplastic
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01 Oct 2019, 5:56 pm

quite an extreme wrote:
naturalplastic wrote:
But in our scenario the air itself is being whipped around at escape velocity, and its getting saturated with soil and rocks and water flying upward.

That's right. Beside of this the earth would be flattened and this would cause an equatorial velocity beyond the escape velocity. This would cause a lot of stuff to escape and surround the earth first but form a second moon afterwards once the tidal forces brought the material to higher orbits. Just my imagination of this ...


More, or less, how I envision it.

The earth gets flattned. It might flatten out. Stuff flies off. Rings or moons would form as stuff buds off. As the earth looses all of its material around the equator its gravitation gradually goes down. Which means escape velocity goes down. Which stuff that was near, but not at, the equator, that was near but not quite at escape velocity, is now at the slightly lower escape velocity. So it goes off flying into space. Which cause mass and ergo gravitation strength of the to weeken a little more, cause more stuff to fly off, and so on. Finally the whole planet self distructs into nothing.



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01 Oct 2019, 5:58 pm

If the earth rotated on its axis fully in less than an hour.....there would be no life as we know it.



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21 Oct 2019, 8:56 pm

naturalplastic wrote:
So my question is this: what if the earth did spin at 25 times its present speed? Would folks in Quito Ecuador, and in Java, go flying off into space?

No but if you jumped straight up at the speed you wouldn't come back down.


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naturalplastic
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21 Oct 2019, 11:55 pm

RetroGamer87 wrote:
naturalplastic wrote:
So my question is this: what if the earth did spin at 25 times its present speed? Would folks in Quito Ecuador, and in Java, go flying off into space?

No but if you jumped straight up at the speed you wouldn't come back down.


Okay. So why not? Why wouldn't folks in Quito go flying off into space if points at the Equator moved at escape velocity while the Earth rotated?



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22 Oct 2019, 1:43 am

All the dirt, stones and air would also escape.
The planet would lose mass and the escaped things would likely form a ring, like those around Jupiter.
The planet would shrink until the velocity on the equator (which is proportional to radius in a rotating rigid object) became lower than orbital velocity. However, that would make the planet lighter, making the orbital velocity lower, too.
I could probably calculate it for a uniform planets but you know that planets aren't uniform. The dense, metallic core would remain.
We would end up with a lot smaller planet with rings. No atmosphere and no water, gases would escape the first and light fluids would quickly follow. New moons may form from debris in the rings.
:cyclopsani:

If you want a specialist to do the Math thoroughly for you, you can submit it for XKCD What If: https://what-if.xkcd.com/ . Randall seems to love this kind of questions.


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