What is the speed of gravity?
Say the sun suddenly disappeared. How long would it take for the Earths orbit to change? Is it the speed of light or slower?
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“The acceleration due to gravity is not the same at all places on the earth’s surface. But it never differs much from 32.1740 feet per second per second.” -from The Wonders of Physics, a deluxe golden book, Text by Irving Adler, The Golden Press, New York, copyright 1966 by Western Publishing Co.
Due to centrifugal force, if the sun suddenly disappeared, and no other forces acted on it, the earth would fly off into space in a straight line, going the same speed it was while orbiting the sun.
Nothing can travel faster than the speed of light so it would take eight minutes before the loss of the sun’s gravity could be noticed on Earth. Now gravitational waves can be detected distortions in the fabric of space/time due to black hole collisions etc have been observed to move at light speed.
It is the speed of light. If the Sun were to instantly disappear it would take 8 minutes 20 seconds before the lights went out and Earth began heading out into space. We would still have Earth gravity so we’d probably only notice the darkness and cold.
Gravity is a force that’s generated between 2 objects and is based on the mass of the objects as well as the distance between them. If you take two objects, and put them on a desk, they are actually pulling towards each other. The thing is, the pull between those objects and the Earth is SO MUCH stronger that it’s basically negligible. Also, there is friction on the desk that resists the objects from moving towards each other.
I’m told this is an actual, practical problem though for when very large ships get close to each other. They are so massive, and there is much less friction between them in the ocean that they will try to gravitate towards each other (I’m not 100% confident in how true this is though because I can’t remember the original source).
Light exerts a small pressure. Because it has a finite speed, light from the sun strikes the Earth at a small angle, but the effect is very small. If gravity acted at that same angle, the Earth’s orbit would gradually increase. I am told it would double in about two centuries.
But why do people think “nothing moves faster than the speed of light”? It’s because they think they know something and they don’t. Remember, light is electromagnetic, and gravity is not.
Two conductors separated by an insulator form a capacitor and will store an electric charge. The charge is stored in the insulator. The amount of charge depends on the material in the insulator and scientists call that (Greek letter) eta. If the insulator is a vacuum, the charge does not go to zero. A vacuum will store an electric charge. The measurement for a vacuum is called eta sub zero.
When a charge moves it generates a magnetic field in whatever material surrounds the path, called core. The amount of field depends on the material in the core and scientists call that (Greek letter) mu. If the core is a vacuum the field does not go to zero. A vacuum will store a magnetic field. The measurement for a vacuum is called mu sub zero.
Engineers use a simple formula to calculate the speed at which a signal moves through a transmission line based on the measured mu and eta. If you plug in mu sub zero and eta sub zero you get the speed of light in a vacuum, exactly.
MATTER is made of electrically charged particles. MATTER can’t move faster than the speed of light. Gravity does not involve charged particles, so its speed is not limited.
@gorillspaws The force is not negligible at all. A common demonstratioon in science fairs is to put two bowling balls on a stick and suspend the stick with recording tape. This is placed behind a clear plastic barrier and a concrete block is placed on the observer side. Visitors can then move the block and watch the suspended ball move toward it. There is a noticeable “thunk” when the ball swings against the plastic barrier.
@SmartAZ You are absolutely correct. Gravity effects can be seen.
In 1797 Cavendish determined the mass of the Earth by suspending 1.6 pound balls near two 348 pound lead balls and measuring the deflection: about 0.1 inch.
His values were very similar to the best results we can do today.
Cavendish Gravity Experiment
Interesting. I thought it was weaker than that.
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Gravity moves at the speed of light.
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