# B If the Sun disappeared, would the Earth continue to orbit?

1. Dec 27, 2016

### Ka Driver

If the sun suddenly disappeared, we wouldn't know it for about eight minutes because that's how long it would take the light to travel the distance between the sun and the earth.

But I've often wondered; if the sun suddenly disappeared, would the earth continue in its orbital path around the sun for eight minutes, or would it immediately fly off into outer space, off its orbital path around the sun, the instant that the sun disappeared?

Does gravity travel at the speed of light? I guess we won't know the answer to this question until we figure out what gravity is.

2. Dec 27, 2016

### CWatters

3. Dec 27, 2016

### Cutter Ketch

Yes, the speed of light, and neither gravity nor light would tell you the sun disappeared until 8 minutes had passed. I doubt you would know after 8 minutes either. Whatever monumental cataclysm annihilated the Sun probably won't be too healthy for the Earth.

4. Dec 27, 2016

### CWatters

I think it might be quite a slow death.

5. Dec 27, 2016

### Cutter Ketch

Oh! I guess "whatever cataclysm" didn't consider ALL the possibilities!

6. Dec 27, 2016

### Ka Driver

That is a fantastic article. Thank you

7. Dec 27, 2016

### K. Doc Holiday

8. Dec 27, 2016

### jbriggs444

What are you calculating? That is, what formula are you using with what inputs and what result?

The only quote I see that seems vaguely relevant from the referenced web site is just an upper bound:

"
determining that the speed of gravity was between 2.55 × 10^8 and 3.81 × 10^8 meters-per-second, completely consistent with Einstein’s predictions
"

9. Dec 27, 2016

### dkotschessaa

No, the article says that tests confirm it to be close to $c$. 2.993 × 10^8 m/s (the lower bound given) is 290,000,000 m/s.

10. Dec 27, 2016

Staff Emeritus
Where does it say that?

11. Dec 27, 2016

### Staff: Mentor

There has been a pretty massive Mentor cleanup in this thread. Please try to keep responses on-topic and mainstream.

12. Dec 27, 2016

### rootone

That would require instantaneous transmission of information, something which never has been observed, and is incompatible with relativity.

13. Dec 28, 2016

### PhizWiz

The Earth would not necessarily cease to orbit. To disappear does not mean that the sun no longer exists, it simply mean that it cannot be seen.

14. Dec 28, 2016

### Rx7man

I can't guess on what would happen in the first 8 minutes.. but if the sun just magically disappeared (became mass-less), Yes, the earth would fly off into outer space.. and probably assume some other orbit at some point in time

15. Dec 28, 2016

### dkotschessaa

Actually now, that's the interesting part. What is the probability of it finding something else to orbit? I would say pretty low (near zero) in general, just by virtue of scale. Can we orbit one of our nearby gas giants? Where would we need to be in our orbit to get picked up by Proxima Centauri A or B?

The probabilities would be fun to calculate. And by "fun" I mean probably horrible.

-Dave K

16. Dec 28, 2016

### Rx7man

There also is a whole lot of stuff out there.. I mean Haley's comet takes 77 years to orbit and leaves our solar sytem...

17. Dec 28, 2016

### jbriggs444

One has the [local] principle of conservation of energy to deal with. The sun cannot simply go away. It could, however, split into two pieces that fly away in opposite directions without violating any conservation laws. The gravitational effects of such an event would propagate at the speed of light.

The Earth is already in orbit within the Milky Way galaxy. Sending the sun away would not change that.

18. Dec 28, 2016

### dkotschessaa

I guess it depends on how far "out there" you are thinking. I am thinking on a universal scale there is a whole lot of nothing, but locally I suppose there is plenty of stuff for earth to come into contact with. But orbit?

-Dave K

19. Dec 28, 2016

### Rx7man

When you see the Hubble pictures, and see that "haze" which consists of large celestial objects you can't even see, and the sky is FULL of that.. and you give yourself enough time to get out there (millions/billions of years?) I think it's likely the earth would end up in orbit somewhere.. perhaps an orbit with a 50 million year period? Perhaps it would collide with something rather than orbit? I can't say!

20. Dec 28, 2016

### Rx7man

The question to me sounded like a theoretical situation where no laws apply.. the sun just ceases to exist instantaneously with no other effects