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Subject:
General Theory Question - Gravity
Category: Science > Physics Asked by: geoffreysteven-ga List Price: $50.00 |
Posted:
11 Nov 2005 09:10 PST
Expires: 11 Dec 2005 09:10 PST Question ID: 591920 |
IS it true that a object a spinning object exerts a slightly stronger force of gravity that a non spinning object? Since spacetime is warped by the mass of an object, if the object is rotating then it would also twist space time as well as warp it. Much like a ball on a bed would would cause it to sink, but if it was spinning, the sheets would wrap around the ball as well. Is this true? I have heard that it is of the more viable the theories to explain dark matter. |
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There is no answer at this time. |
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Subject:
Re: General Theory Question - Gravity
From: qed100-ga on 11 Nov 2005 09:41 PST |
Hello, Yes, this is, roughly speaking, true in general relativity. In fact, even disregarding the "frame dragging", a spinning object has more energy than one which is stationary, and so has a stronger gravitational field. But- this increase is more than offset by the classical centrifugal effects of the rotation, and so an object weighs less on a rotating Earth (at latitudes well away from the north & south poles) than on a static one. |
Subject:
Re: General Theory Question - Gravity
From: geoffreysteven-ga on 11 Nov 2005 11:36 PST |
So that would mean that the gravitational effects an object places on another is based on its ENERGY - which warpsthe space, which of course it a function of its mass and other factors (ie momentum). FRame dragging aside. So that would also mean that if you have a very fast moving object (ie a particle moving near the speed of light or two neutron stars in a close decaying orbit) their warping of 3d space is much much higher than a stationary object. |
Subject:
Re: General Theory Question - Gravity
From: qed100-ga on 11 Nov 2005 12:43 PST |
Yes, that's right. In general relativity, the metric properties of space surrounding an enclosed region are determined by the momentum/energy (what some people call "momenergy"; they are the space/time components of the momenergy vector) content of that region. |
Subject:
Re: General Theory Question - Gravity
From: kottekoe-ga on 11 Nov 2005 16:54 PST |
The gravitational effects from spinning objects are quite complicated, though totally negligible for any but the most extreme astronomical objects. In fact, two spinning objects will behave gravitationally like magnets, with the possibility for both attractive and repulsive forces, in addition to the attractive force, which will almost always be huge compared to the "magnetic" gravitational effects. All of this is described by Einstein's equation that relates the curvature of space to the "stress-energy tensor". The mathematical details are complex and difficult to describe. The most commonly studied case is a rotating black hole. Very weird geometrical effects occur if the black hole is spinning fast enough (very roughly speaking, the rotational velocity at the event horizon is close to the speed of light). For the earth, you can safely ignore all of this, unless you put a super precise, superconducting gyroscope in orbit around the earth and observe it for a year looking for a totally miniscule precession (this experiment is being done and is called Gravity Probe B). As others have pointed out, the centrifugal force for someone standing on the equator is not negligible. |
Subject:
Re: General Theory Question - Gravity
From: keyrlis-ga on 14 Nov 2005 01:00 PST |
So suppose that by some exceptionally large sequences of coincidence and chance (or by well-applied knowledge) there is a toroidal (doughnut shaped) solid of very densely packed material, stable enough to avoid collapsing into a singularity. If this mass were to somehow be rotated at a high speed along its axis, it would have an extremely high energy, correct? And were it to not only be capable of this rotation, but around its own circular focus (think donuts with a hula hoop through them, the hula hoop rotating them in a circle, but also the doughnuts spinning around where they are located on the hula hoop). The potential energy of this object alone would be enormous, much less its effects on our relativistic space. Add to this simply its gravity, and the possibilities are numerous. Would there be a point in the middle of this ring where the rules of our universe would no longer apply? Would that space outside of our perception contain the original super-force before the symmetry fractioning spoken of by string theorists? What would happen to a particle/object accelerated into the focus of this huge amount of high gravity, high energy space? Would it gain so much mass in its acceleration that it would tip the gravity of the structure into a collapse, or accelerate through the loop and continue on? What if the particle is rotating in the opposite direction? Would it be more or less energetic than a particle rotating in the same direction as the loop? Sorry, got lost on a rant. Thanks for your time. keyrlis@gmail |
Subject:
Re: General Theory Question - Gravity
From: qed100-ga on 14 Nov 2005 08:38 PST |
Hello, You said: "there is a toroidal (doughnut shaped) solid of very densely packed material, stable enough to avoid collapsing into a singularity." It's interesting to note that, regardless the structural integrity & stability, such a body would inescapably collapse into a black hole were its mass to be within its own Swartzchild radius. (Swartzchild radius = radius of a mass's own event horizon) And yes, your spinning toroid could be endowed with a very large kinetic energy due to its rotary motion. But there's no reason of which I'm aware for the center point to be exceptional. In fact, if the total mass is less than black hole critical, the center point will actually have zero gravitational field. The spatial curvature would be flat at that point, with zero potential energy. As for counter-rotating masses, their energy doesn't cancel. Energy is a scalar quantity, meaning that it doesn't matter the direction of motion. If there is relative motion, then there is kinetic energy. |
Subject:
Re: General Theory Question - Gravity
From: quantummechanique-ga on 04 Dec 2005 03:03 PST |
http://www.powerballs.com/ Try this and you can feel the force yourself ;) |
Subject:
Re: General Theory Question - Gravity
From: i_know_everything-ga on 31 Jul 2006 17:24 PDT |
Yes it's true. And if the object is spinning fast enough (and is strong enough, which i doubt, to stand the centrifugal forces exerted by the rotation upon itself). It can create a closed timelike loop around itself. |
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