Thought someone should say here - that it's not at all likely that this will happen. And if it did - unless the Earth was literally destroyed as in collapsed into a black hole, or entire surface molten - then you'd be better off creating shelters on the Earth - and - neither of those things at all likely to happen in less than a few hundred million years - millions of generations into the future.
I know this comes up so often in disaster movies and sci. fi. - and also a survey showing that many Americans think that there is a reasonable chance that an asteroid will destroy civilization within 50 years.
But that's fiction, not reality. It's a movie. Like believing there really is a land of Oz, or believing there really are talking mice, such as Mickey Mouse, or that the Flinstones is an account of the life of a real family, and that dinosaurs co-existed with humans. All great fun, but not reality.
Even when movie makers consult closely with scientific advisers, as for the film Gravity - still - they make many changes that are not consistent with scientific understanding just for the sake of a good story. Things that speed up timelines - or put things in different orbits, reverse directions of orbits, make distances between things far smaller than they are, increase the size of an effect by a couple of orders of magnitude - that sort of thing. All done for the sake of a good story - at least so they think.
It is hard to think of a single "hard science" scientific movie that is scientifically accurate in all respects.
So - when it comes to the idea of a giant asteroid threatening the Earth - it makes an entertaining story or movie, but - though there are possibilities of giant asteroids hitting Earth - the chances are that we will have evolved into new species long before that happens.
Smaller impacts yes they could happen and are a real threat that it is wise for us to take steps to avoid - up to 1 km across perhaps - more likely of hundreds of meters scale.
We have already nearly completed the survey for giant asteroids likely to hit Earth - and will probably have completed it by 2020 with 90% of all threats of more than 140 meters discovered - and none found so far - and not expected that we will find any as big as 10 km across which is what you need for a global disaster. In the exceedingly remote chance that there is one headed our way, we will surely know by 2020 or soon after - that is - except for giant comet impacts - but they are even rarer.
Giant impacts large enough to have a chance of creating a global firestorm happen every few tens of millions of years.
That is long enough for small creatures like this
Tarsier
to evolve all the way to humans.
And - unless you happen to be in the impact zone, and we'd know where that is long in advance and be able to evacuate - you'd survive in underground shelters or beneath the sea - worst effects, firestorm, is over within hours - if we can supply entire population of the Earth with several hours of oxygen each - and build underground shelters - and evacuate the impact zone itself - then we could all survive. Fifty years would be plenty of time for this,
Then would have to rebuild civilization - for first few years would need to grow crops with artificial light - would be tough times - and - would be hard to stock up enough food to last through to the first crops also - but - those challenges are the same no matter how you shelter during the disaster itself -.
Then after that - after several years for a land impact, or just a year or two for a sea impact - then clouds disperse, effects would all be over and could replant the world, before long it would be green and full of growing plants just like today - though with many species gone extinct except those we managed to save. Unlike the dinosaurs - we have seed banks that would survive the disaster so would be able to replant all the crop species humans need to survive as well as whatever else we managed to save through the event.
For larger impacts able to make the surface of our planet molten - they happened in the early solar system as you can tell from the giant seas on the Moon - but haven't happened for billions of years.
There is a tiny chance that Mercury will hit the Earth several hundred millions of years from now - and the seas will boil dry eventually unless we move the planet - but all that is so far into the future - that it's long enough for humans to evolve all the way from the first multi-cellular lifeforms. Not much point preparing for then now.
If it's a black hole, then - chances of that is even tinier - it is rare indeed for stars to pass close to each other in our galaxy - and since most stars are not black holes, is extremely rare for black holes to pass stars. And - main effect would not be destroying the Earth - but rather - disrupting the orbits of the planets in the solar system, in a similar way to a pass by of an ordinary star (gravitational effect of a black hole is indistinguishable from effect of an ordinary star if you are outside its event horizon.)
If it did hit anything, sun is most likely target for a star on a one off pass through of our solar system - but chance of that happening is minute.
Now - smaller objects of say 100 meter to 1 km - they are a cause of concern. But all those things are survivable on the Earth and going into space won't help.
Gamma ray bursts - they are easier to survive on the Earth than in space - because you already have the shielding of ten tons per square meter of the atmosphere - and if on the other side of the Earth when it happens - then will be totally shielded during the event itself.
I can't think of a single natural disaster in reality that fits this profile where the Earth is a more difficult place to survive the disaster than in space.
As for technological disasters - those are surely more likely to affect space colonies than the Earth as they are more dependent on technology.
Global warming will only raise the temperature by 5C in worst case scenario. We could theoretically put the Earth into a runaway greenhouse effect - which over a very long period of time would make Earth like Venus - but that needs more than ten times the total of all our oil, gas and coal reserves so in practice it's not possible for humans to do that no matter what we do.
Prmordial micro black holes - if they are common - then stars would be blinking out all the time and we don't see that. And sun again is most likely target not the Earth.
Micro black holes created in particle experiments - that's already been looked at - most likely is that they immediately explode in a burst of gamma rays. But if that theory is wrong - they are created traveling at speeds far higher than escape velocity of Earth or our solar system and would disappear into space. If by chance they did get created with zero velocity - and are stable - then - because they are so tiny they would swallow up matter so slowly just one proton or electron at a time from time that again they are no hazard.
So - I think we need to check carefully and it was necessary to do a mini black hole review for the LHC and should continue to review such experiments and make sure they are safe. But - I don't think a black hole swallowing up the Earth is a likely disaster.
Better to think about things that might happen - such as the smaller asteroids of 100 meters to 1 km. For those then the thing to do is to map them and find out where they are - and that is exactly what we are doing with spaceguard.
Also - things like nano technology and artificial biochemistry - they need extreme care. Again going into space not likely to help - the space colonies most likely to want to use and develop such techniques and might well be the cause of any such disaster as be a way of escaping it, plus also adds potential disasters due to any life forms they might return to Earth if such exist..
As for practicality of sending billions of people into space - not possible right now. But we do have a billion airplane flights a year. So if it does ever get as easy to go into space as to fly to another continent - then we could do it probably. But no need to do this to escape any disaster that anyone has thought of so far - in reality - rather than in movies.
I'm not saying we shouldn't go into space. But going into space to escape disasters on the Earth simply seems a wrong headed misguided thing to do - when you start to look into the details - though at first sight it seems to make sense. The reason being that there is nowhere in space that is worth escaping to.
We need to have other reasons for this.
I know this comes up so often in disaster movies and sci. fi. - and also a survey showing that many Americans think that there is a reasonable chance that an asteroid will destroy civilization within 50 years.
But that's fiction, not reality. It's a movie. Like believing there really is a land of Oz, or believing there really are talking mice, such as Mickey Mouse, or that the Flinstones is an account of the life of a real family, and that dinosaurs co-existed with humans. All great fun, but not reality.
Even when movie makers consult closely with scientific advisers, as for the film Gravity - still - they make many changes that are not consistent with scientific understanding just for the sake of a good story. Things that speed up timelines - or put things in different orbits, reverse directions of orbits, make distances between things far smaller than they are, increase the size of an effect by a couple of orders of magnitude - that sort of thing. All done for the sake of a good story - at least so they think.
It is hard to think of a single "hard science" scientific movie that is scientifically accurate in all respects.
So - when it comes to the idea of a giant asteroid threatening the Earth - it makes an entertaining story or movie, but - though there are possibilities of giant asteroids hitting Earth - the chances are that we will have evolved into new species long before that happens.
Smaller impacts yes they could happen and are a real threat that it is wise for us to take steps to avoid - up to 1 km across perhaps - more likely of hundreds of meters scale.
We have already nearly completed the survey for giant asteroids likely to hit Earth - and will probably have completed it by 2020 with 90% of all threats of more than 140 meters discovered - and none found so far - and not expected that we will find any as big as 10 km across which is what you need for a global disaster. In the exceedingly remote chance that there is one headed our way, we will surely know by 2020 or soon after - that is - except for giant comet impacts - but they are even rarer.
Giant impacts large enough to have a chance of creating a global firestorm happen every few tens of millions of years.
That is long enough for small creatures like this
Tarsier
to evolve all the way to humans.
And - unless you happen to be in the impact zone, and we'd know where that is long in advance and be able to evacuate - you'd survive in underground shelters or beneath the sea - worst effects, firestorm, is over within hours - if we can supply entire population of the Earth with several hours of oxygen each - and build underground shelters - and evacuate the impact zone itself - then we could all survive. Fifty years would be plenty of time for this,
Then would have to rebuild civilization - for first few years would need to grow crops with artificial light - would be tough times - and - would be hard to stock up enough food to last through to the first crops also - but - those challenges are the same no matter how you shelter during the disaster itself -.
Then after that - after several years for a land impact, or just a year or two for a sea impact - then clouds disperse, effects would all be over and could replant the world, before long it would be green and full of growing plants just like today - though with many species gone extinct except those we managed to save. Unlike the dinosaurs - we have seed banks that would survive the disaster so would be able to replant all the crop species humans need to survive as well as whatever else we managed to save through the event.
For larger impacts able to make the surface of our planet molten - they happened in the early solar system as you can tell from the giant seas on the Moon - but haven't happened for billions of years.
There is a tiny chance that Mercury will hit the Earth several hundred millions of years from now - and the seas will boil dry eventually unless we move the planet - but all that is so far into the future - that it's long enough for humans to evolve all the way from the first multi-cellular lifeforms. Not much point preparing for then now.
If it's a black hole, then - chances of that is even tinier - it is rare indeed for stars to pass close to each other in our galaxy - and since most stars are not black holes, is extremely rare for black holes to pass stars. And - main effect would not be destroying the Earth - but rather - disrupting the orbits of the planets in the solar system, in a similar way to a pass by of an ordinary star (gravitational effect of a black hole is indistinguishable from effect of an ordinary star if you are outside its event horizon.)
If it did hit anything, sun is most likely target for a star on a one off pass through of our solar system - but chance of that happening is minute.
Now - smaller objects of say 100 meter to 1 km - they are a cause of concern. But all those things are survivable on the Earth and going into space won't help.
Gamma ray bursts - they are easier to survive on the Earth than in space - because you already have the shielding of ten tons per square meter of the atmosphere - and if on the other side of the Earth when it happens - then will be totally shielded during the event itself.
I can't think of a single natural disaster in reality that fits this profile where the Earth is a more difficult place to survive the disaster than in space.
As for technological disasters - those are surely more likely to affect space colonies than the Earth as they are more dependent on technology.
Global warming will only raise the temperature by 5C in worst case scenario. We could theoretically put the Earth into a runaway greenhouse effect - which over a very long period of time would make Earth like Venus - but that needs more than ten times the total of all our oil, gas and coal reserves so in practice it's not possible for humans to do that no matter what we do.
Prmordial micro black holes - if they are common - then stars would be blinking out all the time and we don't see that. And sun again is most likely target not the Earth.
Micro black holes created in particle experiments - that's already been looked at - most likely is that they immediately explode in a burst of gamma rays. But if that theory is wrong - they are created traveling at speeds far higher than escape velocity of Earth or our solar system and would disappear into space. If by chance they did get created with zero velocity - and are stable - then - because they are so tiny they would swallow up matter so slowly just one proton or electron at a time from time that again they are no hazard.
So - I think we need to check carefully and it was necessary to do a mini black hole review for the LHC and should continue to review such experiments and make sure they are safe. But - I don't think a black hole swallowing up the Earth is a likely disaster.
Better to think about things that might happen - such as the smaller asteroids of 100 meters to 1 km. For those then the thing to do is to map them and find out where they are - and that is exactly what we are doing with spaceguard.
Also - things like nano technology and artificial biochemistry - they need extreme care. Again going into space not likely to help - the space colonies most likely to want to use and develop such techniques and might well be the cause of any such disaster as be a way of escaping it, plus also adds potential disasters due to any life forms they might return to Earth if such exist..
As for practicality of sending billions of people into space - not possible right now. But we do have a billion airplane flights a year. So if it does ever get as easy to go into space as to fly to another continent - then we could do it probably. But no need to do this to escape any disaster that anyone has thought of so far - in reality - rather than in movies.
I'm not saying we shouldn't go into space. But going into space to escape disasters on the Earth simply seems a wrong headed misguided thing to do - when you start to look into the details - though at first sight it seems to make sense. The reason being that there is nowhere in space that is worth escaping to.
We need to have other reasons for this.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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