Why does gravity exists??????????

Question

why two bodies always attract why cant they repel each other?
what is the source of gravity?????????

Answer 1

If you're trying to visualize it, there are a couple of images that you can use as props. Imagine that I have a bowling ball and I drop it into the middle of a mattress. Now imagine that I take a marble and drop it onto that mattress. The path of the marble will be altered by the curvature that (in this case, the weight) of the bowling ball creates along the mattress, and the marble will roll down into the dip that it created.

Now imagine that the universe retains the same qualities of the mattress, but -- to explain it VERY SIMPLY, because there are many more likely dimensions -- it's three dimensional, and when you drop the bowling ball, it's "suspended" (like a marble in Jell-O), and the path that it creates along it in space encompasses the entire ball, and becomes greater with mass.

There you have an extremely short and deceptively simple answer that will help introduce you to the tougher concepts.

Pick up a copy of Hyperspace, by Michio Kaku, the cofounder of superstring theory. He's a brilliant physicist and a fun read.

Answer 2

Nobody knows why gravity exists, nor do we know why the other forces exist. We can only describe them and their effects.

Gravity is the most difficult force to examine because it is by orders of magnitude weaker than any other force. Imagine - a toy magnet defeats the gravitational field of our entire planet when it lifts a paper clip off your desk!

During the last century or so, physicists have managed to unify some of the forces of nature in their search for a theory of everything. First, electricity, light and magnetism were shown to be different aspects of the same force which we now call electromagnetism (scientists aren't always very original in naming things (except when it comes to quarks)).

Not too many years ago, electromagnetism was unified with the weak nuclear force, which causes radioactive decay. Sure enough, they named it the 'electro-weak' force. When this force eventually gets unified with the strong nuclear force (which holds atomic nuclei together despite the repulsion of all those protons), let's hope they use a little more imagination for the name.

SInce all these forces exist in the same universe at the same time, it's reasonable to assume that they are all related to each other somehow, or were in the very beginning. So far they're pretty sure that gravity 'separated' from the other forces at 10^-34 second after the Big Bang, a *very* short time (if time meant anything back when it was just being created along with everything else).

So the connection between gravity and other forces is remote, but it has to be there. String theory is one attempt to untangle the relationship ;) and is presently incomplete, but promising.

Answer 3

I'm sorry. But JimWV may have been teaching physics for 36 years, but his explanation is not correct. First, his understanding of what happens as two massive masses interact gravitationally as they approach each is not correct. Gravity is a "Central" force, meaning that the influence of the force is reduced as the distance increases, but it never exactly goes to zero.

As for why gravity exists; this is at best a philosophical question that really has no answer. To say that gravity exists because of the presence of mass, or the effect that mass has on the curvature of space begs the question of what mass really is at the basic level and why certain elementary particles have mass and others do not. Theories can accurately model physical effects and make very precise predictions. But the fundamental "why?" can never really be answered. You might as well ask why the universe exists.

Answer 4

Imagine you were on top of a fairly tall building watching kids play marbles on the ground below. You noticed several unusual things. When most people shot, their marbles went in straight lines. However, when some shots went near a certain spot of ground they went straight for a while then were deflected suddenly to the right where they continued in a different direction. Still others, coming even closer to that spot were captured, travelling in ever smaller circles until they finally came to rest in the center of the spot. On reflection you would probably realize that even if you couldn't see it because of your height and also the fact that you were looking straight down, the spot was actually a bowl shaped depression in the ground. Now. Isn't that what happens when we fire a rocket in the vicinity of a planet? If we miss the planet completely the rocket continues in a straight line. If it grazes the planet's gravitational field it is deflected toward the planet. If it comes even closer to the planet it goes into orbit around the planet and eventually spirals closer and closer until it crashes into the planet. That's what scientists think gravity is. Just as the depression in the ground was a warpage of the two dimensional (flat) surface into the third dimension (depth), gravity is the warpage of our three dimensional space into the fourth (or some other) dimension. This warpage is caused by anything which has mass. Notice that the center of the warpage itself is the center of the object which causes the warpage. That's why gravity appears to come from the center of the earth. Now, to the other part of your question. Why does gravity attract instead of repel? If you followed the above analogy that question should be answered. But consider other attractive forces. Magnets both attract and repel depending upon their polar orientation (fancy way of saying depending upon which way you turn them). Go back to the beginning example. What if the depression in the earth had been a hill? Imagine the kids pushing cars toward each other from opposite sides of the hill. It would become increasingly harder to push the cars toward each other as they reached the top of the hill and if the kids released their cars at the top they would move rapidly in opposite directions. This is exactly what happens when we move two like poles of a magnet (south and south or north and north) together. Just as we couldn't see the depression in the earth because of our distance and the fact that we were looking straight into it rather than looking at it in cross section, we can't see either the negative warpage in space that causes gravity or the negative and positive warpage that causes magnetism because we are trapped in three dimensional space. In the latter case we can do a simple demonstration using iron filings which gives us a pretty good idea of where the warpage is.

Answer 5

I don't think we know the cause or source of gravity. Newton did not say what it is he showed us it's affect on other objects and developed a way to mathematically predict it's affect. Gravity just "is". Time just "is". The speed of light just "is". Math & Physics describe them and predict them very accurately. However, the secrets of "why" are not known yet. Newtons laws of physics fail in certain instances. Einstein found equations that answered those problems.

Answer 6

Gravity exists so it makes you more down to earth at least every once in a blue moon.
Two bodies donot always attract. stupid men repel me instantly.
The source of gravity is described in all elementary physics books.

Answer 7

the source of gravity? your mass. if you have empty space, a (outer space), and then there are random pieces of debris here and there, they would stick togeather to form one single mass because of gravity how else would the earth had formed?. they can repel each other, of they have the same charges. think of a magnet, or two protons. that's why there are neutrons so that it holds the protons together in the nucleus (of an atom0

Answer 8

Einstein described gravity as the curvature of space. In other words as space curves around the earth, gravity is formed. Also there is entropy which is like an opposite force to gravity, where gravity holds things together entropy causes molecules to disperse. Without gravity we would just float around all the time.

P.S. I read up on this stuff a while back, please don't quote me on it.

Answer 9

What we call gravity is caused by the presence of mass, like a planet, star, or something as small as an atom. Einstein showed that mass causes a curvature or distortion of space itself, and since everything is embedded in space it must follow the shape of space. Where there's a mass, that curvature is inclined towards the center of the mass and any other mass will try to move in that direction.

Why mass distorts space isn't known, just as exactly why mass itself behaves the way it does is not known.

Answer 10

Gravity is the Universal Law that states that every particle in space exerts a force that attracts every other particle in a magnitude that is the sum of the squares of their distances and the product of their masses