If the Sun were to suddenly disappear

[Hugh]

If the Sun were to suddenly disappear, would the Earth instantly fly off into space along a straight line or would there be an approximate 8 minute delay before it did so?

[pat]

Are you looking for opinion or answers?

The relativity answer is "8 minute delay". Scientists are still looking for evidence of gravitational shockwaves from cataclysmic events to verify this aspect of relativity.

[Nick]

Why would it take 8 minutes to do so? Light takes 8 minutes to get to earth, but the gravity of the Sun would take immediate effect... right? :?

[pat]

According to relativity, light is the fastest thing there is. You cannot send any information faster than light. If gravity moved faster, you could send a signal to someone by moving a mass back and forth. They could watch for the corresponding changes in the gravitational field and decode the message before light got to them. Relativity says you can't.

A slightly more technical explanation.... everything moves through space-time, even gravity. By virtue of the way space and time are related in space-time, there is no way to get the ratio of space covered to time spent up over the speed of light.

[moonlord]

That is, all force fields move at speed light, right?

Oh and BTW, doesn't this fit to Relativity forum?

[houserichichi]

No, all force fields do not move at light speed.

The force carrier of the electromagnetic field is the photon, of the strong field is the gluon, of the gravity field (will be) the graviton, and of the weak field are the W's and the Z.

The photon, gluon, and (predicted) graviton are massless. The W's and the Z are not. Any massless particle necessarily travels at the speed of light whereas anything with mass can not. Thus the weak field travels slower than light while the other three do not.

Even then, strong force can be attributed to pions (depending on exactly what we're referring to) in which case it too is slower than light since pions have mass.

[moonlord]

So that's why all struggle to observe a graviton...

[Hugh]

Here is an interesting page on this topic: "The Speed of Gravity - What the Experiments Say" at http://www.metaresearch.org/cosmology/speed_of_gravity.asp, which shows how gravity may be much faster than light.

[houserichichi]

Unfortunately for us van Flandern's paper was written back in the late 90s so finding any public debate on it was a bit difficult. I did, however, come across a little tidbit where John Baez (yes, "that" Baez) piped in and directed the reader to his own site where something he wrote directly smacks van Flandern's paper. Read it here.

To quote from the messages I read (not on Baez' site):

there isn't really anything
to say about van Flandern's misunderstandings of general relativity
that hasn't already been said before.

...

By the way, Paul might enjoy reading an article in the physics FAQ
that was written precisely to address the issue that van Flandern
seemed to find most persistently confusing: the issue of whether
general relativity succeeds in incorporating the principle that
no causal influence travels faster than light. (It does.)

[darthbadass]

No, all force fields do not move at light speed.

The force carrier of the electromagnetic field is the photon, of the strong field is the gluon, of the gravity field (will be) the graviton, and of the weak field are the W's and the Z.

The photon, gluon, and (predicted) graviton are massless. The W's and the Z are not. Any massless particle necessarily travels at the speed of light whereas anything with mass can not. Thus the weak field travels slower than light while the other three do not.

Even then, strong force can be attributed to pions (depending on exactly what we're referring to) in which case it too is slower than light since pions have mass.

Carrier particles are BS, pure and simple. Particles do not carry forces, fields carry forces. They say the photon is the carrier of the EM force is the photon but this is simply not true: photons are by-products of EM interactions. Personally I do not believe in gravitons but if there is one then it is a by-product of gravitational interactions, just as gluons and W/Z bosons are by-products of the strong and weak forces. Fields, not particles, are where the answer lies. There would be no 8 minute delay as gravity propagates (nearly) instantaneously, gravity is faster than light.

[jinydu]

Well, field theories can incorporate time delays as well. For instance, I was taught in physics class that in Maxwell's electromagnetism, disturbances in the electromagnetic field cannot propagate faster than the speed of light.

[houserichichi]

Carrier particles are BS, pure and simple. Particles do not carry forces, fields carry forces. They say the photon is the carrier of the EM force is the photon but this is simply not true: photons are by-products of EM interactions. Personally I do not believe in gravitons but if there is one then it is a by-product of gravitational interactions, just as gluons and W/Z bosons are by-products of the strong and weak forces. Fields, not particles, are where the answer lies. There would be no 8 minute delay as gravity propagates (nearly) instantaneously, gravity is faster than light.

Carrier particles exist and have been detected. They are fluctuations in the fields that propagate throughout the universe. They exist within quantum fields. The W/Z vector bosons and the photon have been detected and measured. The graviton awaits the same. When it's found we won't attribute gravity to the graviton in the sense that classical QM did to the photon and W/Z bosons, but instead will attribute it to some gravitational field just like modern QFT does to the photon and W/Z bosons. So yes, particles really aren't the be-all, end-all of the forces, but they are what we measure and one of many ways to tell the properties of the fields in which they live in.

The graviton is predicted to have zero mass. It therefore travels at the speed of light. Explain why you think otherwise.

[WalkingEagle]

If the Sun were to suddenly disappear, would the Earth instantly fly off into space along a straight line or would there be an approximate 8 minute delay before it did so?

We wouldn't ever know.

We would all be dead in a very short time.

But to answer your question.... No. Wouldn't the gravitational pull of Jupiter and the other gas giants prevent that?

[jinydu]

But to answer your question.... No. Wouldn't the gravitational pull of Jupiter and the other gas giants prevent that?

No, the gravitational pull of Jupiter on the Earth is orders of magnitudes weaker than the gravitational pull of the Sun on the Earth, not nearly enough to stop the Earth from flying away.

[moonlord]

We wouldn't ever know.

We would all be dead in a very short time.

Not necessarily. We could know the truth, for very little time, that's true, but the information travels quickly these days .

[Hugh]

If the Sun were to suddenly disappear, would the Earth instantly fly off into space along a straight line or would there be an approximate 8 minute delay before it did so?

We wouldn't ever know.

We would all be dead in a very short time.

What's your definition of a very short time? I think there would be some humans that would find a way to live at least a few months, if not years. We can live off of canned food, stored water and use heaters or fire to keep from freezing.

But to answer your question.... No. Wouldn't the gravitational pull of Jupiter and the other gas giants prevent that?

My question deals more with what happens to the Earth at the instant the Sun theoretically disappears, and if there is an 8 minute delay before it changes its trajectory.

We could know the truth, for very little time, that's true, but the information travels quickly these days .

The people living on the side facing where it was would spread the news to the others fast. We'd have nighttime everywhere on Earth.

the gravitational pull of Jupiter on the Earth is orders of magnitudes weaker than the gravitational pull of the Sun on the Earth, not nearly enough to stop the Earth from flying away.

There might be a possibility of this happening in a certain sense. They might end up orbiting each other.

The pull of Jupiter on the Sun itself is enough to cause the Sun to orbit Jupiter at a center of mass near the surface of the Sun, so Jupiter pulls on the Sun quite a bit.

The Earth and Jupiter orbit the Sun in the same direction. Let's say that when the Sun disappears, the two planets are positioned so that there is an optimal vector direction so that they head off in the same direction.

Earth's orbital velocity is about 30 km per sec., Jupiter's is about 13, so the Earth would eventually catch up to it, it would increase in speed more as it approached it. Let's say it headed off just at the right angle so that it didn't hit it, but entered orbit with it. It's possible.

[jinydu]

Yes, it probably is possible, but extremely improbable, given the relatively weak gravitational force between the Earth and Jupiter and the vast distance separating them (far larger, even during closest approach, than the distance separating the Earth and the Sun).

[Hugh]

When the original question was posted on the Fourth Dimension Discussion Forum, here is what Mghty Moop had to say about it:

However i beleive that in order to get a grasp of this question one needs to define what gravity is. now as we all know acceleration creates the effect on increased mass by cover a shorter distane in increased time, as with acceleration all gravity is is the intertial force created by the temoral motion of mass through time, why does create an intertial force? this is because this 'time' travel bends the pacetime continuam. so were a mass suddenly to dishappear one must suggest as to whether the space time continuam would instantaneousely leap back to the position it would have been in without the mass or would the process take time, i believe that it is very messy and probably inefficient to imagive gravity as a particle wave of any sort. perhaps the answers to such questions about gravity could be answered better by investigating the 'elasticity' of space time rather than the speed of a particle. however the only way to investigate such a theorum would be near the boundary of a black hole so it may be some time before we could answer a question like that

[papernuke]

to me it would be 8 min because even if light suddenly stops, there would still be leftover gravity that is still pulling, because you only stopped the supply not the stream, there is still a little stream to last 8 min

[Hugh]

to me it would be 8 min because even if light suddenly stops, there would still be leftover gravity that is still pulling, because you only stopped the supply not the stream, there is still a little stream to last 8 min

If one is spinning a rock tied to the end of a string around in a big circle, and the string breaks, does the rock fly off instantly or is there a delay?

[Nick]

I agree with icon. Hugh, the Sun doesn't work that way. Here's a better analogy:

You are watering your flowers. It takes 2 seconds for the water from the tip of the hose to hit the flowerbed. If you suddenly turn off the hose, the flowers will still get 2 more seconds of water. Think about it.

[houserichichi]

If one is spinning a rock tied to the end of a string around in a big circle, and the string breaks, does the rock fly off instantly or is there a delay?

There's a delay. It's just so small that you don't know it. If the length of string was a light-minute away it would take 1 minute for the rock to actually go off on its own. No information can be transmitted faster than light.

[Hugh]

There's a delay. It's just so small that you don't know it. If the length of string was a light-minute away it would take 1 minute for the rock to actually go off on its own. No information can be transmitted faster than light.

If the string breaks near the rock, it flies away almost instantly. If the string were to totally vanish, it flies away almost instantly.

The exact nature of gravity is still not yet fully understood, so we really don't know for sure if there would be an 8 minute time delay.

[Nick]

What does gravity have to do with it? You're cutting off the supply, so the last 8 minutes of sunshine that is still coming would pour onto the Earth's surface.

[Hugh]

What does gravity have to do with it?.

The speed and method with which gravity travels is essentially what matters here.

[houserichichi]

If the string breaks near the rock, it flies away almost instantly. If the string were to totally vanish, it flies away almost instantly.

I think the big kicker to what you said is "almost instantly". Almost is a relative term and instantly is something that is well defined. That's like saying a number is almost infinite. I'll admit, I hadn't considered the case when the string breaks near the rock, however. As far as I understand it nothing, not even the transfer of information, exceeds the speed of light. Superluminal scissors makes for an interesting google search. I think it was discussed years back!

[Hugh]

I think the big kicker to what you said is "almost instantly". Almost is a relative term and instantly is something that is well defined.

Well, when you're talking in terms of the distance between the Earth and Sun, "almost instantly" and "an eight minute time delay" is a big difference.

I'll admit, I hadn't considered the case when the string breaks near the rock

Gravity may involve the exchange of gravitons between the Earth and Sun, and if the Sun were to vanish, then that exchange process might be instantly affected at the Earth.

As far as I understand it nothing, not even the transfer of information, exceeds the speed of light. Superluminal scissors makes for an interesting google search. I think it was discussed years back!

The difference though, is that with the superluminal scissors, it involves the geometrical points on the tips of a huge pair of scissors moving faster than light, not actual matter, and this involves the speed with which the force of gravity can affect things.

There is a page discussing this with some interesting links at: http://en.wikipedia.org/wiki/Speed_of_gravity