Gravity: Sun Moves 10 Miles - Effects on Earth?

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In summary, gravity as such doesn't take any time - it's a property of the local space time around you. Changes in gravity (like you describe) propagate at the speed of light - they must since you can use them to send information.
  • #1
jefswat
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So suppose we are on Earth and the sun moves 10 miles farther away in one second. When do we feel the changed effects of the gravitational attraction here on earth. Is it immediately or after at least ~8 minutes(time it takes light to get here)?
 
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  • #2
Gravity as such doesn't take any time - it's a property of the local space time around you.
Changes in gravity (like you describe) propagate at the speed of light - they must since you can use them to send information.
So if the sun disappeared we wouldn't notice any change in our orbit for 8mins.
 
  • #3
Ok, that's what I figured but I don't remember reading anywhere that explicitly said that
thanks
 
  • #4
Note that it's very difficult to create a gravitational "surprise" because of conservation of energy and momentum. The most sudden thing the sun could do gravitationally, even in theory, is explode into two parts which separate in opposite directions. Even then, the gravitational field at the Earth would not change until the parts had separated far enough for the sum of the potential due to the two parts to be noticeably different from the original total effect.
 
  • #5
mgb_phys said:
Changes in gravity (like you describe) propagate at the speed of light - they must since you can use them to send information.

How do you do that?
 
  • #6
Well there is the information that the Sun is still there!
In theory you could move a large mass and detect the change in gravity at a distance (I didn't say it was easy) if you could measure the gravitational effect instantly on say Pluto you could use it to rig interplanetary horse races before the TV pictures of the winner arrived.
 
  • #7
mgb_phys said:
Changes in gravity (like you describe) propagate at the speed of light
What changes in gravity propagate faster than the speed of light? I think you answered my original question though
 
  • #8
mgb_phys said:
Well there is the information that the Sun is still there!
In theory you could move a large mass and detect the change in gravity at a distance (I didn't say it was easy) if you could measure the gravitational effect instantly on say Pluto you could use it to rig interplanetary horse races before the TV pictures of the winner arrived.

I was thinking that the gravitational response would be slower than c. If the sun disappeared instantly then we would see that it had gone a short while before the Earth headed off at a tangent. It must be reasonably easy to test with a torsion balance, or, hopefully, a more sophisticated equivalent, a large block of lead and an interferometer and away you go.
 
  • #9
jefswat said:
What changes in gravity propagate faster than the speed of light? I think you answered my original question though
No changes propagate faster than light - what I meant to say was.
1, gravity doesn't travel - it's already there
2, changes in gravity do travel - at c
 
  • #10
mgb_phys said:
No changes propagate faster than light - what I meant to say was.
1, gravity doesn't travel - it's already there
2, changes in gravity do travel - at c

ok, you had me confused for a minute there
 
  • #11
Don't all four forces propagate at the speed of light...and how about the theoretical Higgs ocean..that too?? It seems to be a hint at least that they were all unified at some point...
 

1. How does the sun moving 10 miles affect gravity on Earth?

The sun moving 10 miles does not have a direct effect on gravity on Earth. Gravity is primarily determined by the mass of an object, not its position.

2. Will the sun moving 10 miles closer to Earth make things heavier?

No, the sun moving closer to Earth would not make things heavier. As mentioned, gravity is determined by an object's mass, not its position. The sun's mass has not changed, so its gravitational pull on Earth remains the same.

3. Can the sun's movement affect the tides on Earth?

Yes, the sun's movement can affect the tides on Earth. The sun's gravity, combined with the moon's gravity, causes the tides to rise and fall. However, a 10-mile movement of the sun would not have a significant impact on the tides.

4. Would the Earth's orbit be affected by the sun moving 10 miles?

Yes, the Earth's orbit would be affected by the sun moving 10 miles. Any movement of the sun would alter the gravitational forces acting on the Earth, potentially changing its orbit. However, the change would be very small and not noticeable to us.

5. Are there any potential dangers or consequences of the sun moving 10 miles?

No, there are no known potential dangers or consequences of the sun moving 10 miles. The sun is constantly in motion, and small changes in its position have minimal impact on Earth. The Earth's orbit and rotation are stable and would not be significantly affected by the sun's movement.

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