# Opposites Atract

1. Apr 22, 2004

### Atrius

Good old newton, "For every action, there is an equal, yet opposite, reaction."
Also magnetics, opposites atract, similar repulse. So let me get to the point. What is the opposite of gravity. Anti-gravity is simly the absence, isn't it, and also, if gravity pulls down, wouldn't it push from the other side?

2. Apr 22, 2004

### mathman

There is no physical evidence for "antigravity", although there is something speeding up the expansion of the universe, but it is not the opposite of gravity.

3. Apr 22, 2004

### IooqXpooI

I just stated it in the theory 'Reverse Gravitational Force'!

4. Apr 23, 2004

### EL

With equal, opposite reaction, it is ment a force of equal magnitude but in the opposite direction! It does not have to do with different kind of forces. So "antigravity" is not something arising from this law.

5. Apr 23, 2004

### WWW

Exactly like there is no evidence to water from a point of view of a fish.

And what if the Big-Bang is a white-hole?

Last edited: Apr 23, 2004
6. Apr 23, 2004

### Staff: Mentor

That makes no sense whatsoever.

edit (clarification): the first part is wrong and irrelevant, the second part is meaningless.

Last edited: Apr 23, 2004
7. Apr 23, 2004

### WWW

And why it is "... makes no sense whatsoever" or "wrong and irrelevant" or "meaningless"?

Last edited: Apr 23, 2004
8. Apr 23, 2004

### matt grime

the big bang is an event, a white-hole is...?

as for the fish thing... well, the mind boggles as to how there could be anyway of validating that hypothesis.

9. Apr 24, 2004

### WWW

from what point of view?

10. Apr 24, 2004

### matt grime

Erm, ok, it's not an event, so in the theory of the universe in which one has a "big bang" it doesn't happen, and there is no "start" to the universe. Sorry, but to me that doesn't seem reasonable. But then I'm an ignorant pure mathematician who doesn't know what a white hole is, but I would guess it is the opposite (in your favourite sense) of a black hole. And as such will be an object and not an event. (Distinguish between, say, the formation of an object as an event and the object formed.)

Last edited: Apr 24, 2004
11. Apr 24, 2004

### pallidin

Fair questions. Some observations...

- Gravity does not "push from the other side" because it pulls from ALL sides!

- When most people refer to "anti-gravity" they are refering to a device, technology or method to "shield" or mitigate gravity effects in one or more directions. This is not "true" antigravity. In any event, gravity "shielding" has never been shown to exist, but would be one hell of an achievement if done!

- True antigravity would have, among a myriad of other effects, the ability to push away mass as opposed to attracting it. But that is a VERY simplistic statement. For example, just because two opposing magnets push away from each other, their gravitational influence potential of attraction between them is still very much there. In the cases of opposing magnets, the magnetic repulsion is simply greater than the gravitational attraction.

12. Apr 25, 2004

### Nigel

Gravity is attractive simply because it is a shielding effect by mass from the pressure exerted inward by continuum of space caused by the radial motion of matter in all directions outward with a speed increasing linearly with observable distance (Hubble law). Magnetism and electrostatic force are both also inverse square laws but they are attractive or repulsive because they each depend on continuous exchange of energy (not quantum exchange).

When two opposite charges are brought together, they shield each other from energy coming from the surrounding universe, and are therefore pushed together by that energy which has a momentum of p = E/c where E is energy and c is the velocity of light. On the other hand, when two similar charges are brought together, you get repulsion because they mutually exchange energy and recoil apart. There is no real possibility of anti-gravity unless you can control the Hubble expansion of the universe! (Technical and mathematical details: http://members.lycos.co.uk/nigelbryancook/)

Last edited: Apr 25, 2004
13. Apr 25, 2004

### Antonio Lao

For gravity, there is only attraction.

For static electricity (stationary charged particles), there is attraction of "opposite" and repulsion of "similarity." Coulomb's law.

For dynamic electricity (moving charged particles), there is repulsion of "opposite" electric currents and attraction of currents going in the same direction. Like magnetisms attract and opposite magnetisms repel.

When these electric and magnetic phenomena are combined for the vacuum, gravity can be defined as the difference of electric force and magnetic force of the vacuum. When electric is dominant the result is gravity. When magnetic is dominant the result is antigravity.

14. Apr 25, 2004

### ophecleide

If object A exerts a gravitational force on object B, I think the equal and opposite force you're looking for is the gravitational force of B on A.