How does gravity work?

Question

We are doing a topic on forces in science class, and I am struggling to comprehend how gravity works. Due to my personal curiosity, I would really like to have it explained to me in plain English. Thanks!

Answer 1

According to general relativity theory, the pull is caused by the way in which space-time is curved in the presence of mass. In such a curved space-time, other particles will follow the straightest possible path. Let me give an example outside of gravity theory. The straightest possible path in ordinary (flat) space is a straight line. On the surface of a sphere however, the straightest possible path between two given points is an arc of a great circle. Now for an analogy taken from the book "Gravitation" by Misner, Thorne and Wheeler: Envisage two ants that walk on the surface of an apple, going parallel to each other in the direction of the stem (where the surface is depressed). If one approaches the stem on the left side and the other on the right side, they will at the depression move closer together and then separate again, AS IF BEING DRAWN TOWARDS each other. However, they were just going along their straightest path possible. This analogy shows that the geometry of your space(-time) determines your shortest paths. It is important to note that it is the shortest possible path in space-time, not just in space. To see that the latter is ruled out, compare the trajectories from off a tower of a bullet launched at high speed and a ball launched at low speed, in the same direction. In space, their trajectories are curved differently, but in space-time (where the velocity comes into play with time) the curvatures will be the same!).



At the next and probably deepest level of complexity you might rightfully ask: why and how does matter bend space-time?

The simple answer is we do not really know yet.

So there's a science project for you ;-)

Answer 2

Mass is a property of matter. Gravity acts upon that mass. Gravity is an attractive force. Any object is attracted to another object by the forces of gravity, the only conditions are how much and how far. Two grains of dust in deep space will attract each other by gravity the same as two galaxies at a great distance. A large object like a planet has an incredible amount of pull but it can only pull relative to the mass of the other object. Newton's law of gravity describes a force that decreases with the SQUARE of the distance. For every factor of 2 the distance increases, the gravitational attraction decreases by a factor of 2 × 2 = 4. There is however no real limit to the distances that gravity can pull once you accept the weaker pull at that distance. Einstein's gravity is described as matters mass and it's deformation on the fabric of space time.

Take the earth as represented by a heavy bowling ball. Take that ball and place it on a springy trampoline, you will notice it will sink partially as the ball stretches the fabric of the trampoline. In this example the trampoline fabric represents the fabric of space time and it's deformation by the mass of the ball. If you were to place another bowling ball suitably close to the first the balls would move towards each other and finally collide at a common point. Gravity acts in a quite similar way.

Answer 3

According to Sir Newton, gravity, or gravitation, is a natural phenomenon in which objects with mass attract one another. Mass attract one another; meaning mass attracts mass. It (the force) can be calculated by F= G ((m1*m2)/(d^2)); where G is the Gravitational Constant.

Study about Galileo's experiments and the Law of Universal Gravitation (otherwise, you will know nothing, because mathematics s the language of science, not simple English).



However, Einstein (and others) formulated the Equivalence Principle, where it is said that observations made within a gravitational field and an accelerating body is the same. This leads to the General Theory of Relativity (GTR).In GTR, effects of gravitation are ascribed to spacetime curvature instead of a force; mass causes the curvature in spacetime.



For references, I started with Hewitt's Conceptual Physics, but I think Wikipedia is accurate enough.

Answer 4

It is very difficult to explain gravity in simple English, because it is a very difficult topic to easily understand.



But it is basically the attraction of two objects of mass. It is caused by the curvature of spacetime, which is basically a figure of 3 physical dimensions (the ones which we live in) and the fourth dimension being that of time.



So any two objects which have mass will cause a gravitational field between them. So you and I, technically have a gravitational force between one another. The equation however will show that the force caused by this field is dependent on our masses and the distance between us. Because these values are so small the force is going to be practically 0. The masses of the earth and the moon are so large that it will induce a gravitational field strong enough to cause rotation.

Answer 5

I'm not sure anyone really has a feel for it (although I'm sure someone does!), except to say it requires higher-dimensional thinking. They say it's a warping, or partial transposition of space and time.



I always figured if time's moving forward, then a little bit of that motion is being translated into space (hence if time were to reverse itself, so would gravity. My "proof" is in playing a video of something falling, backwards).



Of course the problem with that idea is that if time is "moving" forward, then it's moving as compared to what? When we say something moves through space, it's with respect to time, so what is time moving with respect to? I think the idea is that it's not... and neither does an object actually "move" through space. It's like individual still frames on a movie film. Motion is just the illusion created by the patterns & multi-dimensional geometric orientations of our physical reality.



When you notice that gravity is identical to a constant acceleration, also identical to a constant velocity around a circle (a warped path) - this is called centrifugal force. Inertia says that motion (and path) tends to remain constant, and there is a kind of resistance to any change. Since it is possible to replicate gravity with pure inertia of constant velocity in a curved path, it raises the question along with what is gravity... what is inertia? and why is inertia?



These are all different multi-dimensional (beyond 3 dimensions) viewpoints of the same one phenomenon. So what's the phenomenon?



The best way to understand it is to play with it in your imagination. That's what Einstein did!

Answer 6

Gravity acts like a constant force being applied to anything with mass on the planet. The force is 9.8N on earth sea level an will cause an object to have an acceleration toward earth of 9.8ms-2 in ideal condition.