Another Take on my Gravity Question?

Question

Okay so my last gravity question is a /fail because I didnt, perhaps, explain what I was looking for.

Let's say you and 12 friends were sitting in orbit around the sun (equally spaced in distance so that the first was essentially the same distance as Mercury and the last was about the same distance as Neptune ) with a tool that could measure the gravity and light provided by the sun.

Now let's say that the sun just winked out of existance, that it just stopped existing.

What would each person notice first, the loss of sunlight or the loss of gravity and how much of a difference in time would there be? Would the "lag" be greater the further out from the sun you go?

Answer 1

Your question is really about the propagation speed of gravity. It's still debated among scientists. The 1993 Nobel Prize in physics was awarded to a team who reached this conclusion based on astronomical observations. Watch for results from the LIGO (Laser Interferometer Gravitational-Wave Observatory) and LISA (Laser Interferometer Space Antenna) projects, and the work of Joseph Taylor and Russel Hulse at Princeton.

Gravitation is an extremely weak force, very hard to measure. It's hard to set up an experiment with changing gravitational fields. I wouldn't call it conclusive yet, but I think most physicists would place their bets that gravitation propagates at the speed of light.

So, to answer your question, I would place my bet that each person would experience the loss of gravity and the loss of light at the same instant, Mercury first.  Their motion would cease to be orbital, but just linear.  But there's no way they could measure the change in gravity directly.  All they could do is observe that their motion relative to the star field was now linear, not elliptical around the sun.

Answer 2

No one can tell for sure. Gravity doesnt have to move at the speed of light, i have seen estimates that put it 10^10 times larger than lightspeed. Not confirmed.

Answer 3

Gravity is thought to move at the same speed as light.  It's much harder to measure, though so it's very hard to prove.

So, each person would stop orbiting and move in a straight line a the same moment that they stopped seeing the light of the Sun.  Of course, since the speed of light is finite, the Neptune orbit person would feel these effects later.

The Mercury person was moving faster in orbit, and so would forever move faster.

Now if instead of vanishing, the Sun somehow became a black hole of the same mass, then no one would feel much in the way of gravity change.  It'd just get darker and colder.  Same orbits.

Answer 4

Not sure about the first guy, but 2-12 would notice the gravity first because the sunlight would have been eclipsed by the butt in front of them anyways.  Then again, I guess it would depend on the size of the guy in front's butt...