The effect of having no sun...

[EvilBiker]

OK, a question:

I was having a discussion about JK's lil comment about gravity/marbles on the highway (from a past thread) with a physics doctorate the other day, and he posed this question:

If the sun suddenly disappeared *poof*, we would only notice it gone after 4 minutes in terms of light, right? However, what other effects would manifest themselves?

I assume that the earth's orbit around the now non-existent sun would disappear, and we would take up a new path through the galaxy dictated by the presence of other large planetary entities, for one thing. The earth's spin, IMO, would stay the same, as this effect is not governed by the sun's influence...or is it?

The main question is this: would the loss of the sun's influence become effective immediately, whatever the effect would be, or would there be a delay, as we would see in terms of the light from the sun reaching us after 4 minutes?

I leave it to the forum to debate - my conversational companion could not give me an answer. He said we do not know enough about the instantaneous effects of the forces involved to make a judgement.

 

[pgwenthold]

OK, a question:

I was having a discussion about JK's lil comment about gravity/marbles on the highway (from a past thread) with a physics doctorate the other day, and he posed this question:

If the sun suddenly disappeared *poof*, we would only notice it gone after 4 minutes in terms of light, right? However, what other effects would manifest themselves?

I assume that the earth's orbit around the now non-existent sun would disappear, and we would take up a new path through the galaxy dictated by the presence of other large planetary entities, for one thing. The earth's spin, IMO, would stay the same, as this effect is not governed by the sun's influence...or is it?

The main question is this: would the loss of the sun's influence become effective immediately, whatever the effect would be, or would there be a delay, as we would see in terms of the light from the sun reaching us after 4 minutes?

(actually 8 minutes, but that doesn't matter)

It depends on the speed of gravity waves. Assuming gravity waves move at speed c, then it take just as long for the effects of the loss of gravity to be felt.

 

[arcticpenguin]

Curently accepted theory says that gravity travels at the speed of light, so it would take the 8 minutes for the gravitational effects to be felt.

The earth's spin was started by solar system effects, but now that it's going, inertia will keep it spinning a good long time.

Not that we'd live long enough to find out.

 

[EvilBiker]

Re: Re: The effect of having no sun...

(actually 8 minutes, but that doesn't matter)

It depends on the speed of gravity waves. Assuming gravity waves move at speed c, then it take just as long for the effects of the loss of gravity to be felt.

Ya, sorry about the 8 minutes, my bad

Can we assume that gravity waves move at c? Sure, it's a convenient datum, but do we have any idea besides speculation?

 

[biglee]

Re: Re: Re: The effect of having no sun...

Ya, sorry about the 8 minutes, my bad

Can we assume that gravity waves move at c? Sure, it's a convenient datum, but do we have any idea besides speculation?

The speed of gravity was recently measured, http://www.newscientist.com/news/news.jsp?id=ns99993232 although some controversy exists.

The absence of light would be noticeable. I believe the Earth would also slip out of its orbit, similar to what would happen if you were to let go of a rock tied to a string and twirling it around you. I expect there could be some major earthquakes as a result. We'd freeze to death not too long afterwords.

 

[Michael Redman]

The effect of gravity can't move faster than light, or we could transmit information faster than light, simply by moving stuff. I assume that the earth would fly off at a tangent to the point in its orbit where it was when the gravity of the sun stopped. Would the moon continue to orbit the earth just as it has? I would think so. How fast would we freeze?

Interesting question.

(edit: looks like someone was thinking what I was thinking.)

 

[EvilBiker]

The effect of gravity can't move faster than light, or we could transmit information faster than light, simply by moving stuff.

Nice point. However, has this ever been tested? I would assume not, as we are talking seriously massive bodies here - the gravitational effect is miniscule for (JK anti-plug) marbles, for eg.

I assume that the earth would fly off at a tangent to the point in its orbit where it was when the gravity of the sun stopped. Would the moon continue to orbit the earth just as it has? I would think so. How fast would we freeze?

Nods on tangential movement, my thoughts exactly, though probably not truly tangential, as other planetary bodies would still have an effect.

I would assume the moon would orbit as before, with a slight aberration, as it is locked to the earth (major sphere of influence).

Freezing: interesting question - I think it would take some time. Our core is still molten, so there would be some heat given off from within. When it comes to survival, I surmise we would survive for some time, as we have fossil fuels to use for heat generation. Wouldn't be easy, though - forget a million year species survival time...

 

[Michael Redman]

I bet we would die off fast. There is heat from the core, but not enough (pure guess) to keep surface water liquid. Perhaps the atmosphere would get dangerously cold in only a few days, and people would start to die off from exposure. I doubt we could expend enough energy to make much of a difference, except to keep the richer people of the world warm for a few more weeks.

We would die from starvation pretty quickly, even if we didn't die from the cold.

 

[Dragonrock]

I bet we would die off fast. There is heat from the core, but not enough (pure guess) to keep surface water liquid. Perhaps the atmosphere would get dangerously cold in only a few days, and people would start to die off from exposure. I doubt we could expend enough energy to make much of a difference, except to keep the richer people of the world warm for a few more weeks.

We would die from starvation pretty quickly, even if we didn't die from the cold.

About a million years ago I read a story that had this as the plot line. For whatever reason the earth was knocked out of orbit and the atmosphere was liquified due to the cold. People survived but digging tunnels that were close to the core and were kept warm. They would travel to the surface and since the gases liquified at different temps, they just had to dig down to the correct layer to get oxygen. This just reminded me that the story was called A Bucketful of Air.

 

[toddjh]

I would assume the moon would orbit as before, with a slight aberration, as it is locked to the earth (major sphere of influence).

Yeah, the moon would stay pretty much the same.

Freezing: interesting question - I think it would take some time. Our core is still molten, so there would be some heat given off from within. When it comes to survival, I surmise we would survive for some time, as we have fossil fuels to use for heat generation. Wouldn't be easy, though - forget a million year species survival time...

The oceans would help us a lot. That much water retains an awful lot of heat; the best estimates I've heard is that shallow water (such as near coastlines) would stay liquid for about seven years, and it would likely take centuries to freeze all the way to the bottom. Atmospheric temperatures near the liquid water will hover somewhat below freezing -- cold, but not unworkable, especially in areas of the world that are used to it already.

The big problem would be starvation. Without photosynthesis to drive agriculture, expect billions to starve to death within months -- and the total collapse of all governments far earlier. But, in a coastal area with abundant resources and a good industrial infrastructure (say, the U.S. eastern seaboard), I bet pockets of humanity could survive for decades, burning what would then be a substantial stockpile of oil and coal to keep food production going.

Jeremy

 

[Dancing David]

Major bummer man, yeah great story a bucketful of air, I couldn't remember the name.

 

[fishbob]

If the sun suddenly disappeared *poof*, we would only notice it gone after 4 minutes in terms of light, right? However, what other effects would manifest themselves?

The mechanism that makes the sun go poof would probably have a real big effect on the earth too.

If the sun is blown up, we get blown up too.
If the sun is moved away somehow, the gravity of whatever moves it would pull us along. (A real big truck?)

 

[sickstan]

I can't imagine an experiment that would poof a large object without causing some effect of the poofing. For example, if I had a heavy steel sphere, how could I get rid of it fast enough to measure the effect on the small rock sphere nearby? If I swooped a big crane by and swiped it, the crane is probably big enough to produce its own gravitational influence. If I blasted it with antimatter, the expanding cloud of plasma would produce forces on nearby matter... Can any of you think of a reasonable experimental way to *poof* an object?

 

[Guest]

Re: Re: Re: Re: The effect of having no sun...

Dear Mr. biglee,

In that article, it says that the interval for their measurement is basically [.6, 1.2].

It will be interesting to see if they can make better, and more, measurements.

Sincerely,

S. H.

 

[zakur]

About a million years ago I read a story that had this as the plot line. For whatever reason the earth was knocked out of orbit and the atmosphere was liquified due to the cold. People survived but digging tunnels that were close to the core and were kept warm. They would travel to the surface and since the gases liquified at different temps, they just had to dig down to the correct layer to get oxygen. This just reminded me that the story was called A Bucketful of Air.

"A Pail of Air", by Fritz Leiber. First appeared in 'Galaxy' magazine, 1951.

 

[DanishDynamite]

sickstan:

Can any of you think of a reasonable experimental way to *poof* an object?

No, not off hand. I seriously doubt anybody can. My best attempt would probably be a fast moving 1000 solar mass black hole which passes near the sun and is 90 degrees perpendicular to the ecliptic.

The assumption of a near-instantanous disappearance of the Sun is mostly a thought experiment.

 

[GreyWanderer]

The assumption of a near-instantanous disappearance of the Sun is mostly a thought experiment.

Yeah, so just assume it disappears by magic

(I know magic is hard to accept for you sceptics, but just for this thought experiment)

 

[jj]

For there to be only awful results, it has to be "by magic", otherwise we have to account for the mass/energy of the sun somehow, or the gravity well that sucked it off (that would run away with the earth too, poof).

If the sun turned into energy, we would literally never know. All that energy hitting the earth at C would just make us a teeny-tiny bit of plasma floating off to make a new star.

 

[Dragonrock]

"A Pail of Air", by Fritz Leiber. First appeared in 'Galaxy' magazine, 1951.

Like I said, it was a very long time ago, I really thought it was a bucketful but I guess it was a pail.

 

[PixyMisa]

A bit of digging turned up this fascinating study of this very topic:

Richard R. asks:
What is the speed of gravity?

I have wondered if a star were to suddenly disappear, would its gravitational effects on Earth instantly disappear, thus showing that gravity works instantaneously. But, from watching numerous documentaries on the coyote and roadrunner, I've seen that many times a coyote may run off a cliff and there is a delay until he starts to fall. This shows that gravity does not have an infinite speed as its effect are not instantaneous as it takes time for gravity to reach an object of mass. So what is the speed? What I did was make a simple experiment where I placed a gerbil in a small centrifuge, subjecting it to four times the force of gravity. I then placed the centrifuge in the microwave and set the power at 50%. The result was that the gerbil exploded after 26.35 seconds. Since I would like to keep this segment accessible to the layman, I'll just say that the resultant calculations based on that evidence shows conclusively that the speed of gravity is between 8 and 8 billion miles per hour, give or take twenty orders of magnitude.

I wonder if that was our RichardR?