More S.A.D. trivia
- Thread starter Ross
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Trick question Ross?
The correct phase would be 'what is the acceleration of gravity?' ... which would be 32.2 feet per second squared. Incremental speed can be determined at time increments, while ultimate speed would be infinity in a vacuum. A free-falling body would be ultimately reach a stabilized speed based on the increment of friction ... say about 120 mph (???) for a free-falling man. Speed skiers have reached speeds exceeding 140 mph with advances in aerodynamic shapes & friction reducing materials.
The correct phase would be 'what is the acceleration of gravity?' ... which would be 32.2 feet per second squared. Incremental speed can be determined at time increments, while ultimate speed would be infinity in a vacuum. A free-falling body would be ultimately reach a stabilized speed based on the increment of friction ... say about 120 mph (???) for a free-falling man. Speed skiers have reached speeds exceeding 140 mph with advances in aerodynamic shapes & friction reducing materials.
Re: Trick question Ross?
The acceleration of gravity on earth is well known. But I don't know if a star 5 million light years away from earth blew up and scattered its mass across space how long it would take for the perturbation in the in the gravitonal field to be detected. It would take 5 million years for the light from the event to reach earth.
The acceleration of gravity on earth is well known. But I don't know if a star 5 million light years away from earth blew up and scattered its mass across space how long it would take for the perturbation in the in the gravitonal field to be detected. It would take 5 million years for the light from the event to reach earth.
The change in gravity would be manifested to any measuring device as a change in energy. I believe the speed of light is the limiting factor for energy as well as matter, so we won't be around to measure it! -Paul
The reference star may have blown itself apart 4.5 million years ago and we may be looking a fossil light from a star that no longer exists. Would the measurable gravitional field from the star last as long as light. Arriving as it were in a long pulse and then vanishing along with the light?
If you shine a search light at a wall from an angle, say 45 degrees. The light hits the nearest part of the wall at some point. At a later point the beam of light hits the wall at the far end of the beam. How fast does the wave front travel across the wall?
How then do you explain the bending of magnetic fields/forces. I spent some time as an anti-submarine warfare tech in the U S Navy and we used magnetic anomoly detection gear to find subs that were underwater where we couldn't see them, but we could see what they did to the earth's natural magnet forces. I wish I could remember more of what they taught us, but I think they re-formatted my "personal hard drive". ; )
Star light is continuous but can also be bent by passing other stars. place a small magnet on a table and over lay it with a sheet of paper sprinkle iron filings on the paperand observe the pattern. Next lift the paper off and place a small nail near the magnet but not touching repeat the paper and filings routine.
Gravity
However, IMHO, in order to answer the question "what is the speed of gravity", I believe you must first answer the question "how is the force of gravity propagated"?
If gravity is propagated by waves ...
http://www.space.com/scienceastronomy/090819-gravitational-waves.html
than it might be reasonable to infer that the "speed of gravity", ie the speed at which the force of gravity propagates thru space should be the speed of light.
Edit ... Kloudie's reference article pretty much says the same
Ross, You pose a difficult question best answered by a PhD in physics.
However, IMHO, in order to answer the question "what is the speed of gravity", I believe you must first answer the question "how is the force of gravity propagated"?
If gravity is propagated by waves ...
http://www.space.com/scienceastronomy/090819-gravitational-waves.html
than it might be reasonable to infer that the "speed of gravity", ie the speed at which the force of gravity propagates thru space should be the speed of light.
Edit ... Kloudie's reference article pretty much says the same
Bent Space explanation
The mass of matter bends space. I think that is the best explanation to understand gravity. As the star explodes, its mass is redistributed. I believe that space is supposed to respond instantaneously to the change in mass. I am not sure if there is a relationship between the distance from the mass and any time it takes for space to change its shape. If anyone really cares, I could ask an old friend who is an astrophysicist and get back to you all.
The mass of matter bends space. I think that is the best explanation to understand gravity. As the star explodes, its mass is redistributed. I believe that space is supposed to respond instantaneously to the change in mass. I am not sure if there is a relationship between the distance from the mass and any time it takes for space to change its shape. If anyone really cares, I could ask an old friend who is an astrophysicist and get back to you all.
If the force of gravity is accelerated, then why wouldn't the propogation of gravity also be accelerated to the point where speed is 'instantaneously' infinity?
I don't know I have asked two PhD Physicists and they didn't have answers either.
Newton's Law
It seems to me that gravity has no speed component as it is a Force that is a function of the masses of 2 objects separated by some distance as described in Newtons Law of Universal Gravitation.
F = GM1M2/R^2
F is the gravitational force
G is the universal gravitational constant
M1 is the mass of the 1st object
M2 is the mass of the 2nd object
R is the distance between the objects
No speed .... all magic !
It seems to me that gravity has no speed component as it is a Force that is a function of the masses of 2 objects separated by some distance as described in Newtons Law of Universal Gravitation.
F = GM1M2/R^2
F is the gravitational force
G is the universal gravitational constant
M1 is the mass of the 1st object
M2 is the mass of the 2nd object
R is the distance between the objects
No speed .... all magic !
Attachments
Of course gravity has a speed component, just as any other field. This problem is analogous to the problem of speed of current in an electrical circuit. When one closes a light switch in a room, the drift velocity of carriers (electrons) is slow enough that it takes an appreciable fraction of a second for any given carrier to reach the light bulb. Yet the bulb lights nearly instantaneously because the field propogates along the wire at the speed of light (a line of bb's in a straw may individually move slowly when a force is applied, but the one at the far end will move immediately because the force field propogates immediatly). Einstein and Hawking spent their lives attempting to unify gravity field behavior with EM fields and it is yet to be done. However, it seems that c is the limit and so gravity fields would propogate at c.
By the way, Ross, the oblique wavefront problem is analogous to shining a flashlight out the front of a ship moving at c. The beam front will still not exceed c due to relative length contraction and time dilation in the fixed frame of reference.
By the way, Ross, the oblique wavefront problem is analogous to shining a flashlight out the front of a ship moving at c. The beam front will still not exceed c due to relative length contraction and time dilation in the fixed frame of reference.
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