2006-10-19 01:54:20 · 9 answers · asked by RISHABH C 1 in Science & Mathematics ➔ Physics
You've asked a great question. Despite all the answers given here, the real answer is that we really don't know why gravity is attractive only. Yes, it's true that General Relativity tells us that gravity is curvature in spacetime, but that doesn't say why the curvature is such that the motion of inertial bodies are caused to accelerate toward each other and not away from each other. Similarly, Newton's law merely describes the effects of gravity. It does nothing to explain the nature of gravity.
As a matter of fact, our current physical theories on gravity does a very poor job of explaining its behavior and why it is so much weaker than the other forces. General Relativity only works at large distances, and utterly fails when applied to sub-atomic scales. This painfully points to the fact that we lack a true understanding of the real nature of physical reality.
It is the hopes of today's physicists that by developing a quantum version of the theory of gravity, we can finally develop a better understanding of the true nature of gravity. (There are several candidates, but the verdict is not out yet on which is the correct one. And they are: Supertstring Theory, Supergravity and Loop Quantum Gravity.)
2006-10-19 02:30:37 · answer #1 · answered by PhysicsDude 7 · 2⤊ 0⤋
Gravity is attractive maybe because mass is intrinsically positive.
Among the four fundamental forces of nature, gravity is the most enigmatic and has resisted all attempts at unification with the other three forces. A plausible quantum theory of gravity is yet to be discovered. Perhaps it could explain the coupling of Space-Time continuum to Mass and the resulting curvature which is the origin of the attractive gravitational force.
In recent years there has been an intriguing discovery in cosmology. The expansion of the Universe has been found to be accellerating instead of slowing down, given the attractive nature of gravitational force. Maybe the so-called "dark matter" is the probable cause. An enduring mystery nonetheless!
2006-10-19 09:56:22 · answer #2 · answered by quark_sa 2 · 0⤊ 0⤋
Be cause the force due to gravity is defined as:
F_g = G [(M_1)(M_2)/ r^2]
the constant G is positive, and the distance between the objects always have to be positive.
That leaves the mass. The idea of a negitive mass is absurd (as we can think of it) so this means that the force must always be positive.
BUT THEN AGAIN.
The refractive index of a material defines the direction that light will bend when it passes in to it. For years and years and years people new that that equations would work out if the index of refraction was negitive, but it was thought to be absured. Now we have a few materials that have a negitive index of refraction. It just goes to show that "nothing is impossible if you can imagine it, thats what being a scientist is all about".
Maybe in 10 years we will come up with a negitive mass material. (now wouldn't that be something)
2006-10-19 09:02:03 · answer #3 · answered by farrell_stu 4 · 0⤊ 0⤋
Don't think of gravity from the quantum viewpoint of particles, quantum is suspect on the large scale of astronomical objects. Think of general relativity and the warping of space. It is the warping of space that causes the geodesic to be a conic in the presence of mass instead of the straight line it is in flat space.
Just like you have to think of light sometimes as particles to explain some phenomena (packets of energy) and waves to explain others (interference), the behavior of gravity is easier to understand sometimes as passed by gravitrons and sometimes as a warping of space.
2006-10-19 09:14:52 · answer #4 · answered by sofarsogood 5 · 0⤊ 0⤋
It stands to reason that since there is only one type of mass that there should only be one direction for the force, unlike electric charge. I think Einstein explained it with curved space-time.
2006-10-19 09:00:05 · answer #5 · answered by justaguy 2 · 0⤊ 0⤋
Gravity is by definition and by nature an attractive force. All references to 'gravity' and 'gravitate', etc all directly refer to hauling in or attracting. If gravity done anything else but pull, i suppose it wouldn't be called 'gravity'!?
2006-10-19 09:04:35 · answer #6 · answered by deepazure 2 · 0⤊ 2⤋
Because the universe is a lonely place.
2006-10-19 08:57:04 · answer #7 · answered by Anonymous · 0⤊ 0⤋
because of centrifugal force. it will not attract if earth stops rotating.
2006-10-19 08:57:43 · answer #8 · answered by Anonymous · 0⤊ 3⤋
well, maybe there IS anti-gravity, just that no one has discovered it yet.
2006-10-19 08:59:57 · answer #9 · answered by Q 2 · 0⤊ 0⤋