Why does gravity work backwards?

Question

I realize that gravity is what keeps us on the earth, but think about this... If you compared the Earth to a marry-go-round or a similar ride at the fair, those try to sling us AWAY from the center. Ah! Centrifugal Force! OK, I can understand that. But, with my feeble mind, I try to apply the nature of centrifugal force to gravity and it just doesn't add up. As the earth spins, why aren't we flung into space because of centrifugal force? You will of course say "Well, it's called GRAVITY!". But then, go back and read the first few sentences of my question.

From what I understand about "artificial gravity" that will be developed for space missions, it will be generated by some sort of centrifugal force. The "gravity" will be applied to the outer surfaces of the space craft, so that your feet will be pointed outwards, and your head will be pointed inwards towards the center of the contraption.

So, how do we stay on the Earth despite centrifugal force?

Answer 1

it does wowie thts odd

Answer 2

Centrifugal force is actually a misnomer. It refers to an object's inertia, its tendency to keep on moving in a straight line. That is what pulls you out on a Merry-Go-Round.

Gravity and Centrifugal force are two different things. Centrifugal force is another name for inertia in a rotating system. Gravity is a force that causes all matter, or anything with momentum, to attract other matter or other things with momentum.

The strength of a gravitational field made by an abject increases with the objects mass. The Earth has a lot of mass, so it has a strong gravitational field. It is this field which keeps everything on the earth on the earth.

Rotating space stations use centrifugal force to simulate gravity. Centrifugal force always pushes away from the center of rotation, so if the one's feet are pointed outward, it will seem as though they are in a gravitational field, even though the gravity of the space station is very weak.

Answer 3

Centripetal force. Centrifugal force is illusory.

And it's a problem of both magnitude and direction. The amount of force "flinging us into space" due to Earth's rotation is small compared to the force of gravity (Earth is huge compared to us). Also, the direction of the pull of gravity is directly downward, towards Earth's center. The direction of the force due to Earth's rotation is perpendicular to gravity; the two aren't in direct competition.

Answer 4

see.........

in case of gravity ...... if the earth starts spinning faster enough so that the centrifugal force overcomes the gravitational force     (although there is no force of gravity at all , its just bend spacetime,,,but leave it apart...cause in general terms we tend to use the word force...)   then it can throw us apart . and if comparing a merry -go - round to the earth.....think of a merrygoround as massive as earth....

then you'll come to know about the mistake in your question

Answer 5

Everything with mass is attracted to everything else with mass. That's the force that we call "gravity". You're pulled towards everything around you, and everything around you is pulled towards you. The more mass that something has, the more it pulls other things towards it.

The reason you don't notice this most of the time si that the force of gravity is very weak; you need a lot of mass to make it really obvious.

Earth has a lot of mass, and so it pulls very strongly on you.

The centrifugal force from the earth spinning is much smaller than the force of gravity that pulls you towards the earth, so you don't get flung away.

Why is it that everything with mass is attracted to everything else with mass? In order to learn about that, you should read about "general relativity". It's a big subject, one that's too large to describe sufficiently in a post on yahoo answers.

http://en.wikipedia.org/wiki/General_rel...

Answer 6

Now I know why I rarely venture into the science section.

Geez

Answer 7

i think the problem that you are having is that when you compare the earth to the merry go round,      we are NOT being pulled toward the center of the merry-go-round by gravity.

to be slung off the earth ( like it was the merry go round) we would need a lot of energy - to  exceed escape velocity.

At that point - when we escaped the earths gravitational field, we would be more like the merry-go round experience.

Answer 8

If the Earth was spinning fast enough, not only would we be thrown off in spite of the gravity, but the Earth would fragment and scatter in all directions.

Look at a photograph of Saturn, with its 10 hour period of rotation, and see how squashed it looks at the poles.  A bit faster and it would spread out into a disc.  

The artificial gravity suggested for space stations is only concerned with centrifugal (or centripetal) force, which depends on speed and inertia.  A planet has gravity because of it's mass, not it's spin.  

"Mass attracts mass" is an observed fact.  We still aren't sure "why" it does.  We just know some of the rules for figuring out "how" it does.

EDIT

Put half an inch of water in the bottom of a bucket, then swing the bucket in a vertical circle fast enough so the water doesn't fall out.  THAT water is overcoming the Earths gravity for a short time.  That's all that the artificial gravity on a space station would be, if it was spinning.

Answer 9

To stick with the analogy, I would say that it is like you're on the merry-go-round and have a rope tying you to the center.

There is a force flinging us out, but there is a much stronger force that draws mass together that trumps that flinging force.

Answer 10

well... the gravity is way stronger than the Cent. force...