# What is Gravity?

1. Feb 6, 2014

### Sam Ku.D

I have been wondering about this for a while! What exactly is GRAVITY? How does it work?? How are things pulled towards the earth? or any other mass??
As you know the earth is a huge electron reserve. As every matter is made up of protons and electrons! Right? My suggestion is that the Earth attracts other masses as there is a force of attraction between the Earth(electron reserve) and the mass as every mass contains positively charged protons. But the problem is, why do every things have the same acceleration due to gravity? Its 9. something right? why is it the same?
Thank you
~ Sam Ku.D~

2. Feb 6, 2014

3. Feb 6, 2014

### Sam Ku.D

but why are masses attracted towards one another?

4. Feb 6, 2014

I don't think anybody knows. According to Einstein's general relativity, gravity isn't even a "force" that attracts or repels or anything. It's the curvature of space, which is caused by the presence of mass.
Why does mass curve space? I don't think anybody knows that either.

5. Feb 6, 2014

### Palacekeep

as u have known, most of masses is neutral,because they have the same amount of protons and electrons.so, what i want say is that maybe u must give up your opinion. if you had learned universal gravitation, u would find the reason is the mass itself. if u want to know the deeper reason, maybe u should learn something about relativity theory.

6. Feb 6, 2014

### Drakkith

Staff Emeritus
The basics of gravity can be found on plenty of websites online. Wikipedia is a good place to start.

First, please be aware that personal theories are not allowed here at PF per the rules. The forum exists to teach people about current mainstream science, not to discuss non-mainstream theories from either amateurs or professionals.

That being said, your idea is not correct. Gravitation is not due to any "electron reserve". The Earth is, on average, very close to electrically neutral and would not experience any attraction or repulsion.

Consider two objects, A and B. A has 1 kg of mass while B has 2 kg's of mass. The force of attraction from the Earth's gravity on object B is twice as much as A because it has twice the mass. However, this added mass also has twice the inertia and will be harder to accelerate. The increased attraction from gravity and the increased resistance to acceleration exactly cancel each other out so that all objects accelerate at the same rate.

You can easily see this by plugging in numbers to the equation F=MA.
Rearrange to A=F/M and you can see that if F doubles and M doubles, then A MUST remain the same since no matter what you plug into F and M the ratio is always the same.

7. Feb 6, 2014

A very nice example.That was pretty understandable for a secondary student.

Last edited: Feb 6, 2014
8. Feb 6, 2014

agreed!

9. Feb 8, 2014

### haruspex

More accurately, it's curvature of space-time. This is an important detail. The concept as I understand it, which is not hugely, is that a component of the object's movement along its time axis appears to an observer to be acceleration in a spatial dimension. This immediately explains why inertial mass and gravitational mass should be always in proportion (the remarkable coincidence which led Einstein to his theory).

10. Feb 9, 2014

### Manraj singh

This might be a little aside from the topic, but gravity is deeply mysterious. The question "why does gravity exist" isn't even considered a scientific question. When a raindrop falls, it doesn't even experience acceleration due to gravity because of its buoyant force.

11. Feb 9, 2014

### mal4mac

In Einstein's model it's curvature of space-time. But this is just a model, just as "gravity is a force" is part of Newton's model. No one knows *exactly* what gravity is, and they might never know. How could you ever know that you had the final answer?

12. Feb 9, 2014

### Staff: Mentor

Drakkith is correct, this thread is closed.