How much longer will life on earth last?

We know the earth is doomed because the sun will eventually engulf the world, and our galaxy will collide with Andromeda, making even interstellar travel ultimately useless (unless we find resources on another planet that could allow help us leave the galaxy). Although, I have read that because of the vast in the galaxies, there's a possibility Andromeda may simply pass through.

But I'm getting ahead of myself. My question is about how much longer life on earth will last. Obviously, most life will have been exterminated long before the sun swells up to a red giant and engulfs the earth. The expansion of the sun will happen over time, and life on earth will gradually become more unbearable.

Life on land will vanish first, but what about ocean life? How long undersea life continue?

Originally posted by vivify
We know the earth is doomed because the sun will eventually engulf the world, and our galaxy will collide with Andromeda, making even interstellar travel ultimately useless (unless we find resources on another planet that could allow help us leave the galaxy). Although, I have read that because of the vast in the galaxies, there's a possibility Andromeda may ...[text shortened]...

Life on land will vanish first, but what about ocean life? How long undersea life continue?

The power output of the sun increases steadily as it burns hydrogen. The figure I remember is of the order of a billion years. The prediction is that the oceans will evaporate due to increased solar luminosity. The only life remaining will be extremophiles, archeans live up to 2 km deep in the Earth's crust and don't mind fairly extreme heat.

The time scale is of the order of how far into the future the earth's orbit is predictable. It's possible it will move outwards and avoid it. I think the answers they get are model dependent.

This is a link to the relevant Wikipedia page:

http://en.wikipedia.org/wiki/Timeline_of_the_far_future

Originally posted by vivify
We know the earth is doomed because the sun will eventually engulf the world, and our galaxy will collide with Andromeda, making even interstellar travel ultimately useless (unless we find resources on another planet that could allow help us leave the galaxy). Although, I have read that because of the vast in the galaxies, there's a possibility Andromeda may ...[text shortened]...

Life on land will vanish first, but what about ocean life? How long undersea life continue?

Andromeda colliding with our galaxy won't have much effect on any one solar system since it is mainly the gasses that interact with each other not the stars. But the sun going into red giant phase will do us in and it probably won't have to engulf Earth to kill most life since like he says, the oceans will evaporate and it will just get too hot except for extremophiles.

That still is hundreds of millions of years in the future. It does look like Earth has entered middle age and does not have the same future as it did the past.

Humans will have to beat the odds, that is to say, the odds of surviving as a race and as a technological one at that to have any kind of chance of living past the age of the sun going red giant.

If we survive the next 1000 years with technology intact we may have some kind of interstellar travel, but not faster than light, even 10% of c will get us out to other stars in something like a reasonable time. 40 years to Alpha Centauri. Looks like that would be iffy anyway, AC is like a sister sun to ours and may have about the same lifespan so we would need to find either a young star or an old red dwarf with habitable planets. They have a life span in hundreds of billions of years before they kick the bucket so that would be a much longer lived place to go if there was a planet in the habitable zone, or you build one there.

Originally posted by DeepThought
The power output of the sun increases steadily as it burns hydrogen. The figure I remember is of the order of a billion years. The prediction is that the oceans will evaporate due to increased solar luminosity. The only life remaining will be extremophiles, archeans live up to 2 km deep in the Earth's crust and don't mind fairly extreme heat.

The t ...[text shortened]... link to the relevant Wikipedia page:

http://en.wikipedia.org/wiki/Timeline_of_the_far_future

If human civilization is still around tens of millions of years from now, it can keep Earth habitable by gradually moving Earth away from the sun with a series of very controlled slingshots of comets or asteroids between Earth and Jupiter. We have a billion years to work with, so doing this with one modest asteroid every century or so would probably suffice. Doing it once every 10 years would probably only require a mass on a par with, say, an Imperial Super Star Destroyer.

http://www.starwars7news.com/wp-content/uploads/2014/12/Super-Star-Destroyer.jpeg

EDIT: There are, I believe, a lot of very subtle resonances between the planets we would need to take care with when moving Earth. Adjustments of the orbits of other planets, such as Mars, may also be required over the long haul. Also adjustments would need to be made to the Moon's orbit to keep it more or less the same distance from Earth. In fact the Moon is gradually moving away from the Earth a centimeter or so a year. We should fix that, I say! Move it back to where it was in the Mesozoic Era!

Originally posted by Soothfast
If human civilization is still around tens of millions of years from now, it can keep Earth habitable by gradually moving Earth away from the sun with a series of very controlled slingshots of comets or asteroids between Earth and Jupiter. We have a billion years to work with, so doing this with one modest asteroid every century or so would probably suffi ...[text shortened]... ter or so a year. We should fix that, I say! Move it back to where it was in the Mesozoic Era!

Never mind all that messing with asteroids, we can just use the force.

http://home.web.cern.ch/about/updates/2015/04/cern-researchers-confirm-existence-force

Originally posted by DeepThought
Never mind all that messing with asteroids, we can just use the force.

http://home.web.cern.ch/about/updates/2015/04/cern-researchers-confirm-existence-force

WHAT!!! That is just just the kind of stupid crackpot nonsense that gives real science a bad repatriation it ill deserves! How could they waste billions of dollars doing such .....
....
...
...Oh, right. Now I get it. It's a joke.

Originally posted by humy
WHAT!!! That is just just the kind of stupid crackpot nonsense that gives real science a bad repatriation it ill deserves! How could they waste billions of dollars doing such .....
....
...
...Oh, right. Now I get it. It's a joke.

that was a "meta-joke": http://en.wikipedia.org/wiki/Meta-joke

Originally posted by humy
that was a "meta-joke": http://en.wikipedia.org/wiki/Meta-joke

I metajoke once, running for president🙂

Originally posted by humy
WHAT!!! That is just just the kind of stupid crackpot nonsense that gives real science a bad repatriation it ill deserves! How could they waste billions of dollars doing such .....
....
...
...Oh, right. Now I get it. It's a joke.

just noticed I misspelled "reputation" as "repatriation" there.

Originally posted by humy
just noticed I misspelled "reputation" as "repatriation" there.

Meanwhile, getting back to the OP, is it really withing the bounds of physics to have asteroids whip by Earth to get it to move away from the sun? If so, how far out would the Earth move in its orbit from one such encounter? Say an asteroid with 0.001 times the mass of Earth?

Originally posted by sonhouse
Meanwhile, getting back to the OP, is it really withing the bounds of physics to have asteroids whip by Earth to get it to move away from the sun? If so, how far out would the Earth move in its orbit from one such encounter? Say an asteroid with 0.001 times the mass of Earth?

You might find this mildly interesting:

http://www.theguardian.com/environment/2001/jun/10/globalwarming.climatechange

Originally posted by sonhouse
Meanwhile, getting back to the OP, is it really withing the bounds of physics to have asteroids whip by Earth to get it to move away from the sun? If so, how far out would the Earth move in its orbit from one such encounter? Say an asteroid with 0.001 times the mass of Earth?

I don't know how to do the maths for this but I have heard of the idea of defecting asteroids to defect the Earth so it takes a slightly wider orbit around the sun to counter the man made part of the greenhouse effect. But I haven't heard of using this to put the Earth far enough from the sun to stop it being overheated by the sun when the sun expands into a red giant. But, somehow, without doing the maths, I doubt there is enough asteroid material out there to do that because the total mass of the asteroid belt is estimated to be just ~4% of the mass of the Moon or ~0.05% of the Earth!

But, going slightly off-topic here, I think even if this was practical to use to slightly defect the Earth's orbit to counter the greenhouse effect, it would be far easier to use less drastic methods such as artificially slightly increasing the albedo of the Earth or simply don't put to much CO2 in its atmosphere in the first place.

Originally posted by humy
I don't know how to do the maths for this but I have heard of the idea of defecting asteroids to defect the Earth so it takes a slightly wider orbit around the sun to counter the man made part of the greenhouse effect. But I haven't heard of using this to put the Earth far enough from the sun to stop it being overheated by the sun when the sun expands into a re ...[text shortened]... ng the albedo of the Earth or simply don't put to much CO2 in its atmosphere in the first place.

You could also put Earth sized sun shades in the same orbit as Earth but far enough away from Earth to keep from going in orbit, like a moving sunshield, I think that would be a lot easier technologically speaking. There wouldn't have to be much deflection, say 10% or so reduction in sunlight would do it.

Even if we were able to make an asteroid skim by Earth to move the orbit out some, wouldn't that also mean the elliptical nature of the orbit would mean it would also approach the sun closer than it does now as well as make it go further from the sun?

Originally posted by sonhouse
You could also put Earth sized sun shades in the same orbit as Earth but far enough away from Earth to keep from going in orbit, like a moving sunshield, I think that would be a lot easier technologically speaking. There wouldn't have to be much deflection, say 10% or so reduction in sunlight would do it.

Even if we were able to make an asteroid skim by ...[text shortened]... would also approach the sun closer than it does now as well as make it go further from the sun?

not sure but I think there is a way to make the orbit of the Earth more circular as well as further from the sun.

Note that a 10% reduction in solar radiation reaching the Earth wouldn't be anywhere near enough to save the Earth even some time before the sun becomes a red giant because the sun's luminosity would nearly double before then and, when the sun does becomes a red giant, its luminosity would increase something like ~50 fold and then, much later, when its helium is exhausted, the Sun will increase its luminosity by something like 4000 fold. I believe it would be so hard to save the biosphere of the Earth that it would be actually easier to terraform and move to a suitable exoplanet.

Originally posted by sonhouse
You could also put Earth sized sun shades in the same orbit as Earth but far enough away from Earth to keep from going in orbit, like a moving sunshield, I think that would be a lot easier technologically speaking. There wouldn't have to be much deflection, say 10% or so reduction in sunlight would do it.

Even if we were able to make an asteroid skim by ...[text shortened]... would also approach the sun closer than it does now as well as make it go further from the sun?

Well, the only stable orbit where it could be placed a sun shade is the Lagrangian L1 point, only 1.5 million kilometers from the Earth, and this orbit isn't very stable, rather semistable. Any object there has always to adjust its position or else it will drift away. The fuel used would be rather substantial. Furthermore, if you put a sun shade big enough to shade all the Earth, in the form of a sail, then the solar wind will blow it from its position quite easy.

I don't think this is a usable idea, I'm afraid...