Gravity... is it an Effect or a Force?

[Hearly]

Ok, I'm sick (sore throat, and fever) so I've been re-reading some of the Good stories out there that also deal with FTL travel, and such..

It got me thinking a bit about gravity... Now I believe Einstien said Gravity is Curved Space-time, Hence it is an effect of that.. (the deeper you are in a gravity well/Curved space-time, the more acceleration is pushing you down towards the center)

But there is also people and books that say the Gravity force is carried by the particle called the Gravitron...

Now if Gravity is carried by a particle, doesn't there have to be an Anti-Particle for it? Just like an Electron vs Positron, etc..

The closer you get to the Speed of Light, the More mass you have, and once you hit the speed of light (if possible) you'd end up turning yourself and ship into a black hole... (either by closing yourself off from our space-time or breaking throu it..)

Now thinking about what I posted above, If Gravity is a force like the other ones, and is carried by a particle, it should be entirely possible to have Anti-gravity, But if Gravity is an Effect of Curved Space-time, then anti-gravity shouldn't be possible...

ya I know I'm babbling a bit, but I was just trying to figure it out in my own mind, and thought I'd ask your guys thought on it..

[Tylhandras]

I, for one, do not think we as a planet have the necessary level of science to make that determination.

Thats not to say that gravity doesn't behave much like a photon does. Though now that I think about it, that could be a valid theory for gravity as well.

Who knows? I don't.

[Fel]

There are three basic schools of thought on the nature of gravity.

1: Gravity is a "field," an area of energetic force that exerts itself against objects, and has unlimited reach: that is, the gravity field of one object affects every other object in the universe. Gravity is an energetic force, but does not affect other forms of energy directly, only indirectly, because gravity has a tangible effect on space, warping and distorting it. Distance and/or size makes this effect on distant mass negligible. Gravity, being an energy field, travels in coherent waves that can be measured, but thus far no attempt to measure a "gravity wave" has succeeded. This theory has some following.

2: Gravity is the effect of mass on the fabric of space, something akin to the field theory above, but this effect is passive and not active--that is, there is no coherent energy to be measured. Mass, energy, and even light is affected by gravity because it follows the curve of space gravity creates. This theory has two branches of theory as to gravetic motion: one theory is that gravity extends at a set speed (though possibly undefinable) as "ripples" in space, and since it has speed, it can be measured as "gravity waves." The second theory is that gravity simply affects space, and this spatial effect is felt instantaneously everywhere at once. Neither of these branch theories has been proved, because if gravity does have a set speed, it is so massive that it simply cannot be measured (in other words, faster than light. But before you say "relativity allows nothing to travel faster than light," recall that relatively only applies to phenomena that have mass. Gravity, being a passive effect, has neither mass nor energy, and thus is not affected by relativity. Gravity, if it does move at a set speed, would move at the speed of light to the speed of light, as it were, and would be the absolute fastest natural phenomenon in the universe known to man). This theory has well represented following.

3: Quantum Mechanics attempts to define the force of gravity in quanta, as discrete, measurable packets of energy (this is a fundamental aspect of quantum mechanics, converting all forces and measurements into bundles of energy of i power, kind of like an atom of energy. This is the smallest possible energy unit of that type.) Quantum mechanics tries to rationalize gravity by converting gravometric force into quanta of units called gravitons, which flow toward the point of gravometric focus. We haven't studied gravity yet in physics, so I don't know much about this theory. I'm very interested to learn more about it, though.

[Spec8472]

There are three basic schools of thought on the nature of gravity.

Very nice explanations, thanks



(FWIW: #2 as described by Fel is the theory used in the Honor Harrington universe for their FTL Comms using "Grav Pulses")

[Shadowhawk]

Aaaaaaaaargh.

That said, hypothetical graviton particle is boson particle, like photon (boson electromagnetic interaction), and like photon is it's own antiparticle. Hypothetical, because we don't have (yet) quantum theory of gravity, and there are a few different approaches to it, some from the general relativity (gravitation) side, some from quantum field theory (quantum mechanics) side - that includes all the (super)string theories.

Besides, special theory of relativity tells us that FTL travel might cause problems with causality (killling your own grandfather like).

[Fiferguy]

It makes me wonder, if gravity is nothing more than warped space time (I think about a ball sitting on a stretched cloth for example), wouldn't it be possible to have a rise in it as well? In effect, having an anti-gravity, because space time was sloped away from a certain point in space?

And in that way, would a black hole, to my knowledge the ultimate expression of gravity, be just the opposite in another universe? I remember in my astronomy class that the professor talked about a postulated white hole as the output of a black hole from this universe in another dimension, but that they hadn't found any yet. Could it be that a white hole is an anti-gravity area of space?

I do have to agree with Tylhandras though. I just don't think that we as a species have enough understanding to truly know what's going on out there. I just leave it like this: It works. Why question a good thing?

[matrix]

Isaac Asimov once wrote a story where one guy developed an anti-gravity field but it had one draw back in the sence that the energy off gravity reversed was so great that any object entering the field was instantly excellerated to the speed of light in the direction it was moving when it entered the field.

P.S. I can't remember which story it was but it was released in his I Robot Compendium.

[Shadowhawk]

The problem with antigravity (at least in general relativity scneario) is that it needs m^2 < 0 (well, approximately).

[Phantom]

Not even going to touch this one ...


Phantom

[Were_Fan]

The problem with antigravity (at least in general relativity scneario) is that it needs m^2 < 0 (well, approximately).

Perhaps there will be a breakthrough when a different approach is used, not just in gravity research, but in relativity also. Frame of reference is important when making observations. We can't get out of gravity's frame of refernce so our observations may be flawed.

For example, classical Euclidean geometry said that given a line and a point, there is only one line through the point that would be parallel to the original line. That held true until someone started out with the premise that there were either NO parallel lines or there were multiple/infinite lines parallel to the original. Thus, non-Euclidean spherical and hyperbolic geometries were born.

We assume the speed of light is the fastest attainable speed in our universe? What if it isn't? Only the Faey know and Fel isn't telling. LOL

[MISER]

My opinion of gravity differs on the basis of whether it is a rock or an apple that falls and hits you on the head....

[Shadowhawk]

The problem with antigravity (at least in general relativity scneario) is that it needs m^2 < 0 (well, approximately).

Perhaps there will be a breakthrough when a different approach is used, not just in gravity research, but in relativity also. Frame of reference is important when making observations. We can't get out of gravity's frame of refernce so our observations may be flawed.

I don't quite understand that, but the laws governing general relativity can, and usually is, written in invariant form, the same in all the frames of references.

Besides, general relativity tells (or rather is based on the observation that) us that a large set of frames of reference are interchargeable (like inertial frame with constant gravitic field is eqivalent to accelerating frame of reference with no gravity).

[MommyDoom]

(MommyDoom's eyes cross and she hears this whooshing sound in her head as she tries to read the posts listed under this topic, making it as far as the 4th or 5th word in Fel's post and then gives it up utterly as a bad job)

Ack. Oop. Urp.

Pardon me.

[Were_Fan]

The problem with antigravity (at least in general relativity scneario) is that it needs m^2 < 0 (well, approximately).

Perhaps there will be a breakthrough when a different approach is used, not just in gravity research, but in relativity also. Frame of reference is important when making observations. We can't get out of gravity's frame of refernce so our observations may be flawed.

I don't quite understand that, but the laws governing general relativity can, and usually is, written in invariant form, the same in all the frames of references.

Besides, general relativity tells (or rather is based on the observation that) us that a large set of frames of reference are interchargeable (like inertial frame with constant gravitic field is eqivalent to accelerating frame of reference with no gravity).

You mentioned "based on the observation" in your post. That is the key. Our theories are all based on our observations. Our frame of reference is our 3 dimensional universe. (For the purpose of illustration, I'll skip time as a 4th dimension) How can our observations be incorrect?

Picture a two dimensional "paper" world being changed by a 3D entity. The 3D entity takes a "pencil" and draws a line. The 2D entities perceive only the contact point between the "pencil" and their "paper" universe. Many 2D'ers may perceive the appearance of the line as magic but some try to explain the line with science. However, they have no concept of a 3rd dimension and don't realize the contact point of the "pencil" and their "paper" is an infinitely small part of the "pencil".

Consider a bicycle at night with a wheel light. To a stationary observer from the side, the light appears to be somewhat like a bouncing ball going down the street. From a point in line with the axle, the light appears to be going in a circle if the frame of reference does not rotate with the axle. From behind, the light appears to be bouncing straight up and down. All observations are correct from their relative frame of reference.

We observe gravity from our 3D/4D universe frame of reference and we can't change the frame of reference. What might we be missing?

[Halcyon]

Uhhhh....the room is spinning... or is it some gravitational force at work?