Suns gravity effect on earth.

[Wade]

So I came across this discussion in a reddit thread and thought I had a handle on this scenario.

If the sun suddenly vanished I understand that visually it wouldn't register for about 8 minutes but under Einstein s theory we would immediately leave the gravitational "bowl" that the sun had left. I don't think the planets would go racing off necessarily but wouldn't we start to drift?
Maybe even towards the sun? Therefore the point about the light not hitting us for about 8 minutes could increase or decrease depending on the drift? Is the earth's rotation effected by any of this? would it cease to exist, or if it did continue would it play a part in where or how fast we would drift off?


If the sun disappeared from one moment to another, would Earth orbit the point where the sun used to be for another ~8 minutes? • /r/askscience

 

[Beaumains]

According to my local expert; gravitational waves move at the speed of light. So, the earth would not feel the effects of the Sun disappearing for ~8 minutes. Then we would cease to orbit the Sun and move in a straight line into deep space. That line wouldn't exactly be straight at the beginning, it would be affected by the gravitational influence of the other planets in the Solar System, depending on where they all are at the point the Sun goes away.


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[Burnt State]

The point at which we collide with other planets, moons etc. also departing the solar sytem's vicinity and traveling at different speeds is when things get really interesting. It all reminds me of my UFO apocalypse dream I had last year. I shudder to think of such momentous events.

 

[Randall]

According to my local expert; gravitational waves move at the speed of light. So, the earth would not feel the effects of the Sun disappearing for ~8 minutes. Then we would cease to orbit the Sun and move in a straight line into deep space. That line wouldn't exactly be straight at the beginning, it would be affected by the gravitational influence of the other planets in the Solar System, depending on where they all are at the point the Sun goes away.

The problem with claiming that if the Sun were to vanish, that it would take the same amount of time for the gravitational effects to become apparent as it would for the light to go out, is that it is an assumption predicted by General Relativity Theory, but which has not been confirmed by any real world experiment. The thinking is that the effect would propagate as a gravity wave at the speed of light.

But unfortunately, gravitational waves have never been detected ( see article ), and evidence based on interpretations of Cosmic Background Radiation and other sources aren't quite the same idea as the kind of wave associated with light e.g. something emitted from a source. It's more like a compression/decompression associated with the changing distances between objects, each of which have gravity. The wave frequency is therefore dependent not on the "speed of gravity", but on the oscillation of the sources e.g. a rapidly rotating binary star system. If gravity acts on things instantaneously, then no gravity waves could be detected from single stationary objects.

Nevertheless, scientists keep searching for the source of gravity in particle accelerators, and some believe they may have found it, but the jury is not unanimous. Personally I don't think they'll ever find it by looking at particles. Other scientists are looking for gravity waves using extremely sensitive detectors e.g. LISA. But even if gravity particles or waves are found, it still doesn't mean they've solved the puzzle. The fundamental forces of nature, of which gravity is one, are imparted onto our realm by something unknown. Simply locating a particle that seems to carry gravitational properties doesn't explain how those properties got there in the first place.

Let's also not forget that while GRT is a mathematical construct that helps make calculations more accurate; that does not mean every aspect of GRT has a direct 1:1 correspondence to reality. In other words, thinking of space as curved by gravity in order to facilitate more accurate calculations doesn't mean space is actually curved. It just means that the formula resembles a curve ( e.g. logarithmic ) and from that, we can better predict where in space things will be.

So the long and short of it is that if the Sun vanished, although it's doubtful, it might just be the case that we'd feel the effects immediately. We don't know. In either case the trajectory of the Earth and everything else orbiting the Sun would change radically. The planets would keep their moons, but each planet/moon system would go drifting off in its own direction as if let go from the end of a long string spinning around an axis where the Sun used to be.

 

[bacteria_wagon]

Here's an interesting take on this scenario from Michael at Vsauce.

He does assume gravitational waves to be a real thing, so bases his presentation on that. Great thought experiment nonetheless. The conept of snowball earth travelling through the galaxy for billions of years as an ark full of extremeophiles is pretty nuts.

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