What would happen is the Sun goes off NOW ?

[skysurfer]

Just a hypothesis. When the Sun *immediately* stops generating energy, when would we notice it ?

Are we immediately (i.e. 8:20 minutes light time) in darkness or do we notice dimming the Sun after a few days / years ?

[snas (Stuart)]

So the sun is there and then "god/thor/zeus etc" reaches down and picks up the sun (ouch) and flings it inter intergalactic space

mate I actually did a talk on this at Redlands Astronomical Society.

Yes, it will take 8 min 20 sec for us to notice it is suddenly very dark

In addition, the sun's gravity is also gone. As a result we would cease to go around and around where the sun used to be and instead would just fly off into space at a tangent to where we were in our orbit about where the sun used to be. The effect of Jupiter on our speed and direction was something that I just did not bother to go very much into, other than to mention that Jupiter would now be the largest nearby source of gravity and as such would obviously have some degree of effect on our tangential direction.

Also, we would soon start to fell rather chilly.

Stuart

[asimov (John)]

We'd all be 'snap frozen' fairly smartly I would say, lol.

[madbadgalaxyman (Robert)]

Originally Posted by skysurfer

Just a hypothesis. When the Sun *immediately* stops generating energy, when would we notice it ?

Are we immediately (i.e. 8:20 minutes light time) in darkness or do we notice dimming the Sun after a few days / years ?

The issue is, how long does it take for the change in energy output to travel from the core of the Sun to its surface. A change in the core energy output does not instantaneously change the output of energy at the photosphere.

After this initial delay, due to the time needed for energy to reach the surface of the sun, then we have about another 8 minutes!

[Steffen]

Why are you asking? What have you done???

[AstralTraveller (David)]

The answer depends on whether the Sun has simply stopped emitting radiation from its surface or whether the core stops producing energy. In the former case we freeze pretty quickly, perhaps a day or two for lakes, rivers and the atmosphere but longer for the oceans. The atm would freeze out in stages. First there would be all the water vapour, then a frosting of CO2 and after some delay there would be the oxygen, argon and finally nitrogen. The oceans would freeze over and that would slow the cooling of the deep oceans but unless the Earth is producing enough internal heat (which I very much doubt) then the oceans would also eventually freeze solid. I suspect that the core and mantle would be unaffected and so we would still have a magnetic field (for what it's worth).

In the latter case we may not see a difference in our lifetime, perhaps not for thousands of years. The Sun has a lot of stored heat and it takes a very long time for energy from the core to reach the surface. After that either 1) we slowly freeze or 2) there is a core-collapse supernova and we fry.

One thing is certain, however; there are no good outcomes.

[xelasnave]

The Sun in effect compresses space time one wonders if the space time would cause regional inflation such that the planets would seperate greatly that separation presumably instant or at a rate like Guths inflation

[sjastro]

Originally Posted by xelasnave

The Sun in effect compresses space time one wonders if the space time would cause regional inflation such that the planets would seperate greatly that separation presumably instant or at a rate like Guths inflation

Its been along time Alex.

If the Sun was to suddenly vanish one needs to consider the conservation laws for mass and energy.
According to General Relativity if such an event was to occur the loss of mass would be made up by the propagation of gravitational waves.
Gravitational waves is one of the few predictions made by GR that has not been accounted for.

Gravitational waves are a distortion of space-time and is unlike "ordinary" gravity.
Ordinary gravity has a spherical symmetry where all objects fall radially inwards towards the centre.
Gravitational waves have what is known as a quadrupole symmetry.
If the Earth was hit by a large gravitational wave, the Earth would be elongated along one direction and compressed in the perpendicular direction according to the longitudinal and transverse orientation of the wave.

So while it has nothing to do with inflation you are correct that it is a space-time effect.

Regards

Steven

[xelasnave]

Hi Steven thank you I just read and rarely post.

[DavidNg (David)]

What is the "speed" of gravity? I dare ask, ie how long would it take for the earth to spin-off from the moment of sudden disappearance of sun's gravitation force.

[sjastro]

Originally Posted by DavidNg

What is the "speed" of gravity? I dare ask, ie how long would it take for the earth to spin-off from the moment of sudden disappearance of sun's gravitation force.

This is a problem which puzzled scientists until Einstein came along.
If gravity travels at a finite speed, the Earth would advance a certain distance in its orbit before gravity would influence it.
Somehow gravity had the ability of acting on this advanced position before the Earth reached it.
A simple solution would be to claim that gravity travels at at infinite speed.

In General Relativity gravity has a rather different meaning.
The Earth is travelling along a path in curved space time. Gravity is "felt" as a reaction force much like the sideways centrifugal force acting on you as your car is driven around a bend.
Since gravity is a reaction force, the speed of gravity is no longer a relevant issue.

Gravitational waves on the other travel at the speed of light.
If the Sun disappeared, gravitational waves (if they exist) would blast Earth out of its orbit in around 8 minutes.

Regards

Steven

[Peter Ward]

If sun instantly "switched off" and you happened to be looking at it about 8 minutes later, say through your solar telescope, I'd expect you'd see a tiny black dot, at the centre of the solar hemisphere facing the earth, which quickly expands to the limb, due the size of the sun and time it takes light to travel a solar radius.

Global warming will no longer be a problem after that

[acropolite (Phil)]

Hmm so they've privatised our nearest star and Enron were the highest bidder.

[ZeroID (Brent)]

Originally Posted by acropolite

Hmm so they've privatised our nearest star and Enron were the highest bidder.

It was probably considered to be an environmental hazard and shut down with all the other Nuclear Reactors.

[bojan]

Originally Posted by sjastro

...
A simple solution would be to claim that gravity travels at at infinite speed....

Maybe a stupid question.. but still:
Could it be said that the gravitational field, associated with every particle was present from BB times (before inflation).. so every individual field of every individual particle simply moves with it and contribute to the total grav field of the larger bodies ?

[avandonk]

Originally Posted by skysurfer

Just a hypothesis. When the Sun *immediately* stops generating energy, when would we notice it ?

Are we immediately (i.e. 8:20 minutes light time) in darkness or do we notice dimming the Sun after a few days / years ?

If you mean that all nuclear reactions spontaneously cease at the core, we would not notice anything for thousands of years. It can take a photon from thousands up to millions of years to get to the surface of the Sun from the core. The photon collides many times on the way out. Even at the speed of light this random walk takes all this time.

Reminds me of the conjecture in the 1800's where the Sun was made of coal and how long it would burn for. Geological evidence showed that the Earth was thousands of millions of years old. Even an amount of coal the size of the Sun would not burn for that long with the measured energy output.

Conjecture is good as it can clarify our ideas.

Bert

[xelasnave]

I was thinking total disappearance clearly ignoring the question however when the energy stops could we see the start of a gravitational colapse and maybe an explosion this may happen pretty fast

[avandonk]

Originally Posted by xelasnave

I was thinking total disappearance clearly ignoring the question however when the energy stops could we see the start of a gravitational colapse and maybe an explosion this may happen pretty fast

Alex you are quite correct but our Sun is too small for a SN it would simply expand into a red giant when it ran out of fuel. This would take quite some time.

We have neutrino detectors at a few places around the Earth. These will tell you instantly when the Sun stops nuclear fusion as neutrinos escape from the Sun uninpeded by mere matter.

Bert

[xelasnave]

Thank you Bert

[el_draco (Rom)]

Originally Posted by Steffen

Why are you asking? What have you done???

I knew it... explains why my feet suddenly feel cold
How many times do you have to say.... READ THE MANUAL!!