How does gravity work?

Answer 1

All particles of matter attract each other. The more particles there are, the greater the attraction.

Dense and large planets and stars have a huge gravitational pull due to the (very, very, very.....) large amount of particles contained within them. This is why all planets revolve around the Sun. It contains more than 99% of the solar system's mass and has the most gravity.

Gravity can work over vast distances. The nearest stars with are light years away have a gravitational effect on our solar system.

Answer 2

Gravity from the Sun acts on Earth in exactly the same way as gravity from the Earth acts on the ball.

The problem with the ball thrown up in the air is that the Earth is getting in its way. If you could throw the ball hard enough and make it fly in the right direction, you could put it in orbit around the Earth. That is how people put satellites in orbit around the Earth. First, place the satellite on a rocket that will take it to a certain altitude. Once the rocket attains the right speed and direction, it releases the satellite, which then keeps orbiting the Earth without touching the ground. In the figure below, on the left I show the ball being thrown from a point A on Earth, following the continuous line, and falling on point B. If the ball could change its trajectory at the highest point and followed the dotted line, it could enter orbit around the Earth. All this of course requires the strength provided only by a rocket.

The Earth is being pulled by the Sun all the time in an orbit that has the shape of an ellipse. In the case of the Earth the ellipse is almost a circle. The ball that has been thrown up is also being pulled by Earth's gravity and is really in an elliptical orbit. Now suppose that we could instantly shrink the Earth to the size of a super massive boulder of, say, a mile in radius just after the ball is thrown. The strength of gravity only depends on the mass of the attracting bodies. Therefore if the Earth kept all its mass during the shrinking process, it will continue to attract the ball with the same force and nothing has changed, except that now the ball will go through point B and fall down for miles and miles. It won't necessarily strike the shrunken Earth. Instead it will swing around it.

Let's see what happens as the ball moves around the shrunken Earth. The ball tries to keep at all moments a straight line trajectory and will resist any attempt to change this trajectory. This property is called inertia and it is a law of nature. The inertia of a body increases as its velocity increases. As the Earth pulls the ball, it makes it move faster and increases its inertia. It is this inertia what gives the impression that the ball is resisting gravity and accelerating away from the Earth. Actually what is happening is that the ball is trying to follow a straight line trajectory.

Gravity gets stronger as the distance decreases. Therefore the ball also feels a stronger pull as it approaches Earth. When the ball recedes from Earth, gravity gets weaker. The velocity and inertia of the ball also decrease and its trajectory bends and makes the ball turn around. The inertia of the ball counters gravity in such a way that the trajectory of the ball is an ellipse, a closed orbit. One needs to use calculus to show this mathematically.

In the case of the real Earth orbiting the Sun the situation is the same, except that Earth's orbit is nearly a circle with the Sun near its center as shown in the figure on the right (sizes not drawn to scale). Here too the Earth's inertia counters gravity at all times, increasing when the Earth gets slightly closer to the Sun, and decreasing when it gets farther.

Now imagine that the Sun expanded so much that it engulfed the Earth's orbit. Actually this is expected to happen some five billion years from now. Clearly the situation would be the same as that of the ball that is thrown from Earth's surface and falls on another point of Earth. The Earth's orbit wouldn't make it too far if the Sun were the same size as the Earth's orbit, would it?

Answer 3

Many of the answers you have received dealt with describing gravity (i.e. with Newton's Law). I'm guessing that you are asking what the mechanism is. How one mass affect the other just because it's there. I'm guessing you are looking for a theory for gravity, an explanation, not just the description.
Newton's Law is a description. Newton himself said, "I frame no hypothesis." He had no idea how gravity worked.
The first well-accepted explanation (and the one with the most evidence and backers) is Einstein's Theory of General Relativity. It's hard to explain quickly, especially without diagrams, but try this:
Einstein proposed that mass curves the space around it. We don't notice the curve of space, but the effect is that objects that are "really" travelling straight lines follow the curve of space (or space-time, actually). Their paths looked curved to us. We explain the (apparently) curved paths by saying that the objects are being attracted by a gravitational force coming from the mass.
It's kind of like centrifugal force: If you are in a box (e.g. a car) going around a curve, you feel a force toward the outside. Looking down from the top, an observer sees no force to the outside. The observer says that your body is just trying to go straight and the outside edge of the box is coming in to make you go in a curve. INSIDE the curving box, centrifugal force is real. Looking from the outside, though, there is no such thing. Centrifugal force is a fictitious force.
Einstein proposed that if space is curved, then when we think we are going at uniform speed in a straight line (through spacetime), we are really accelerating. So we should see a fictitious force. It is mass that curves space so we see that fictitious force near the mass. That force is gravity.

Answer 4

Being one of the fundamental forces in Nature what is know about gravity concerns the well known law of gravitation due to Newton and the relativistic view as a space-time distortion effect from masses. The actual "pictorial" details of how gravity works are NOT understood fully. The interaction requires an exchange particle named the graviton which has been theoretically postulated but which has defied experimental verification.

Answer 5

Gravity is not well understood.
The model of general relativity is that masses warp the space-time fabric in their vicinity. This in turn causes other masses to accelerate towards them. The common analogy is imagining a bowling ball on a mattress (where the bowling ball is a mass and the mattress is space time; other smaller masses such as marbles would move towards it).

Answer 6

The earth's gravity keep us from floating like in outer space. All mass exert gravity?

Answer 7

gravity is the attraction between two bodies placed having a definite mass.
it is given by formula g=GMm/r*r
where g is acceleration due to gravity, G is gravitational constant,M and m are the masses of the two bodies placed, r is the distance between them.

for ex. you and your computer are also exihibiting gravity towards each other. but as the two masses are very small therefore force of attraction is very less.

in case of earth and us the mass of earth is very large also the radius of earth is 6400 km therefore the force of attraction is very large. hence as a result we get attracted towards the very strongly and it is very hard to escape earth gravitational field.
however it can by a speed of 11.2km/s i.e. escape velocity

you may refer to books for further query