# If the World Stopped Spinning?

Discussion in 'Earth Science' started by pharaohmoan, Jan 14, 2008.

1. ### gdudeasciforums userRegistered Senior Member

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Whats wronge with it?

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3. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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The rate of spin of a planet does NOT increase or decrease its gravitational pull (except for perceived gravity - if it spins fast enough you'd get thrown off).
Most certainly increasing the rotational rate does NOT increase gravity.

And for the other, sound barrier or not has no bearing on "being torn apart".
Men have ejected at supersonic speeds and survived.

And your other statement: "Gravity is made by the rotation of a mass of a object in space (such as a planet). Wich in easier terms; the bigger the planet, the hevier things are."
Also rubbish.
Those two sentences are in no way linked in reality.
The rotation is not linked to gravity (as stated): and it's not size so much as mass - it's possible to have a large planet composed of not very dense material - hence it would have a relatively low gravity.

Last edited: Oct 19, 2009

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5. ### gdudeasciforums userRegistered Senior Member

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you said "The rate of spin of a planet does increase or decrease its gravitational pull (except for perceived gravity - if it spins fast enough you'd get thrown off). "

We haven't flung off the planet even though were going at 40,000 kp/h. So then how fast does the Earth have to spin in order for people to fly off?

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7. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Should have written "The rate of spin of a planet does NOT increase or decrease its gravitational pull..." but that should have been obvious from the clause I appended.

40,000 kph?
How do you get that figure?
The equatorial circumference is 40,075.16 km and we do that in 24 hours = 1669.7983 kph.

Work it out: escape velocity is ~11 km/ sec (39600 kph), so we'd have have a "day" as short as 1.01 hours. ((24/39600)*1670)
Which also negates your supposition (based on what I wonder) that the faster the Earth spins the higher the gravity.

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9. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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No it isn't - "if the earth would spin twice as fast we the gravity would be 2x harder".
Post #35.

And again, the spin does not affect the gravity, it merely counteracts it with another force.
The Earth will still have a 1G pull regardless of spin rate.

10. ### gdudeasciforums userRegistered Senior Member

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then what is the other force?

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12. ### gdudeasciforums userRegistered Senior Member

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true. but what about the sound barrier? Even though people have bailed out at 726 mp/h i belive is the speed of sound, but what about going 2.3x faster than the speed of sound

13. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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The sound barrier as the sound barrier isn't a problem it's more the absolute (relative to the atmosphere) speed.
Accelerating rapidly into the atmosphere, or frictional heating.

And bear in mind that the atmosphere would also probably be departing rapidly...
SO you could be doing 11 km/ sec relative to the Earth's surface (i.e. what would definitely be classed as supersonic), but if the atmosphere is moving with you then you won't suffer any ill effects on that count.

14. ### gdudeasciforums userRegistered Senior Member

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The atmosphere won't be moving with you. Have you given some thought to "Newtons First Law of Motion" to everything on earth?

Last edited: Oct 19, 2009
15. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Really?
It would be moving with you for much the same reason - it's "attached" to the Earth as we are and moves with its rotation - that's why we don't have 1700 kph winds all the time.

That's why we'd get thrown off - we'd continue to move at peripheral speed which is fast enough to overcome the gravity.

16. ### gdudeasciforums userRegistered Senior Member

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but we are hevier so we will go faster then the wind. put your hand in front of you, move it as fast as you can to your right. What happends? You feel the air.

17. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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And? At no point did I say we'd move at the same speed.

Which has what to do with anything?

18. ### TBodilliaRegistered Senior Member

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Let's start with the law of universal gravitation:

F = G (M1 * M2)/r² Force equals the gravitational constant times the mass of the 1st object times the mass of the 2nd object divided by the square of the distance between them.

Where in that equation is angular velocity mentioned?

On to practical examples:
The Moon spins at about 1/28th speed of the Earth and yet is has about 1/6th of the gravity. Why? 1/6th of the mass.

Venus has a retrograde rotation, and a slow one at that. That means Venus spins backwards (from us, normal), slowly. Venus doesn't have anti-gravity. Venus is not throwing rocks off into space or having rocks float away. Venus has about the same gravity as us. Why? About the same mass.

More examples needed?

19. ### D HSome other guyValued Senior Member

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2,257
How about the Sun? It spins rather slowly, about one rev per 25 days. Yet "surface" gravity on the Sun is about 28 g. Could this possibly be because the Sun is a tad more massive than the Earth?

20. ### gdudeasciforums userRegistered Senior Member

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you can feel the air.

21. ### AlphaNumericFully ionizedRegistered Senior Member

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Actually its about 1/81 the mass but the smaller radius slightly offsets that.

22. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Yep.
And if I put my hand in the freezer I can feel an ice cube.
Which also has nothing to do with gravity or being ripped apart or the Earth stopping turning.

23. ### superstring01Moderator

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Gravity comes from the mass, not the spin.