Descriptions of gravity in texts are confusing to me because they describe the attaction between objects as though it was the the property of the objects.
We reject the concept of "action at a distance" (i.e. lifting your coffee cup with your mind) and yet we accept that the moon, 250k miles across a vacuum is able to drag the earth's oceans around. We calculate trajectories of space probes using the "gravity" of planets to accelerate rockets.
Models of gravity are equated with balls rolling round a vortex.
But space is a vacuum. Yes there are particles and "solar wind" but the theory of "aether" has been debunked. Planets and suns don't float in some soup that can be swirled by the passage of an object. Still, they seem to act as though they do.
Isn't gravity acceleration(s)? First, from the Big Bang and including all events since then, a genealogy of events (frictions).
Earth & moon each wiggling separately to a very old dance.
2006-12-15 05:56:01 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
Physics has a lot to say about your questions, but the answer to what you're asking is equivalent to a three-year graduate course.
Gravity is one of the four (maybe five) fundamental forces of nature. (They are: the electromagnetic force, the strong force, the weak force, gravity, and maybe Dark Energy.) All of them work through "action at a distance". The way this is dealt with in modern physics is through "fields". The fields are a property of the vacuum, and they mediate forces and the movement of particles (or strings).
The central problem in current physics is that the field representation of gravity is fundamentally different, and incompatible with, the fields for the other forces. In General Relativity, the gravitational field is represented as the curved geometry of spacetime. This is an extremely accurate representation of gravitational force, and can be used to make highly accurate predictions about motion. The only problem is that this model of gravity is incompatible with the model for the other forces and with quantum mechanics.
2006-12-15 06:52:28 · answer #1 · answered by cosmo 7 · 1⤊ 0⤋
Gravity is considered a warping of space-time in relativity, but for everyday purposes, like navigating a space craft or calculating the size beam needed for a bridge span, the old model of it being a force proportional to mass and inversely proportional to distance is totally relevant and absolutely not outdated at all.
The old action at a distance argument has been sidestepped by saying that it is a field that acts, and the field is everywhere. But gravity is no different from electromagnetic force or the two nuclear forces in that respect.
2006-12-15 14:00:04 · answer #2 · answered by campbelp2002 7 · 3⤊ 0⤋
The concept of gravity is that anything that has mass, has gravity. With all the mass that the Earth contains, it holds more gravity than a human being. However, the human being still pulls the Earth towards itself just the same as the Earth pulls the human down towards the Earth itself. See the article in Wikipedia about "Newton's Law of Universal Gravitation"
2006-12-15 14:35:09 · answer #3 · answered by Maverick 6 · 0⤊ 0⤋
Gravity is, much like centripetal force, something that seems to exist but really is an artificial concept to make it easier to do calculations.
In reality the space time fabric is bent, and any action (or is it reaction?) isn't "at a distance" at all. The moon is just falling towards the bottom of locally bent space.
2006-12-15 14:27:31 · answer #4 · answered by Anonymous · 0⤊ 1⤋
You can try jumping out the window, and then let us know if gravity is outdated.
2006-12-15 14:16:23 · answer #5 · answered by Stan the Rocker 5 · 1⤊ 1⤋