And even if you survived to see the collision, you wouldn't personally be harmed. As Dubinski points out, galaxies may collide but stars don't, they are far too small.
Is it actually that simple? I don't know but there's a couple of things I'd worry about.
Firstly while a collision with a star is wildly unlikely, a near miss
might disrupt the earth's orbit, which might be just as disastrous for humans. Granted we'd have a vast period of time in which to prepare for it. (I don't know what the probability of a sufficiently close approach is, though.)
Secondly stars aren't the only things found in galaxies, there's dust and gas as well. I don't know if it's hot and dense enough to present a problem for us though, but the 100M degrees people quote for collisions in other galaxies doesn't sound hopeful.
Near misses. The spiral arms of a galaxy like the Milky Way have a density of about 0.003 stars per cubic light year and are about 1,000 light years thick. The solar system would come within 1,000 AU of another star in about one in seven dives through such a galaxy. Things would be a bit more exciting in a dive through the core, 3,000 light years across and with 2 stars per cubic light year; then we might expect to come within 10 AU of a couple of stars or so on each dive through that galaxy: exciting, but not obviously more of a danger to life and limb than the star we currently have within 1 AU of us.
As for the temperature of the interstellar medium (http://en.wikipedia.org/wiki/Interstellar_medium), remember that it is not very dense (even the densest molecular clouds (http://en.wikipedia.org/wiki/Molecular_cloud), at 106 atoms per cubic metre). The Earth is bathed in the solar wind, with a temperature of millions of kelvins, and it doesn't seem to do us much harm. The interstellar medium is much less dense than the solar wind.
If Mstar=1E30kg (about half the sun), Mearth=1E25kg (a slight overestimate), r=1E11m (a bit under 10AU), we get F = 1E33.G = 1E23N (about) giving a=F/Mearth=0.01m/s^2. Integrating over a year gives 315km/s, albeit presumably in a varying direction, about ten times the earth's current max orbital speed of 30km/s, which suggests cause for concern. (The sun would be moving in the same direction but, of course, much less.)
Numbers from wikipedia, calculations on the back of a bit of scrap paper, please do check for errors l-)
Yes, if it happened to end up near Saturn (or Uranus or Neptune) then that could lead to gas giants flying around in potentially dangerous ways, but there's loads of space for them to avoid one another in - I don't thnk there's any particular reason that the interloper should spend much time near the ecliptic.
But before it turns into a red giant, the sun is expected to grow in brightness by 10%; at some point (1 billion years time?) the Earth's land surface will be uninhabitable and then a bit later (3 billion years?) the oceans will boil and the Earth will resemble Venus.
If we still have a technological society in a billion years it wouldn't surprise me if our descendants were able to adjust the earth's orbit to keep it hospitable. Though if they enjoy a challenge they might prefer to try turning the sun back down.
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(no subject)
Date: 2006-09-09 12:13 am (UTC)Cartesiandaemon: I'm fed up of opressing news, I'll see if there's anything else on livejournal.
Cartesiandaemon: Aaah!
(no subject)
Date: 2006-09-09 11:04 am (UTC)It's 3E9 years away yet.
You'll most likely be DEAD first.
(no subject)
Date: 2006-09-09 11:40 am (UTC)(no subject)
Date: 2006-09-09 11:50 am (UTC)Is it actually that simple? I don't know but there's a couple of things I'd worry about.
Firstly while a collision with a star is wildly unlikely, a near miss might disrupt the earth's orbit, which might be just as disastrous for humans. Granted we'd have a vast period of time in which to prepare for it. (I don't know what the probability of a sufficiently close approach is, though.)
Secondly stars aren't the only things found in galaxies, there's dust and gas as well. I don't know if it's hot and dense enough to present a problem for us though, but the 100M degrees people quote for collisions in other galaxies doesn't sound hopeful.
(no subject)
Date: 2006-09-09 04:10 pm (UTC)As for the temperature of the interstellar medium (http://en.wikipedia.org/wiki/Interstellar_medium), remember that it is not very dense (even the densest molecular clouds (http://en.wikipedia.org/wiki/Molecular_cloud), at 106 atoms per cubic metre). The Earth is bathed in the solar wind, with a temperature of millions of kelvins, and it doesn't seem to do us much harm. The interstellar medium is much less dense than the solar wind.
(no subject)
Date: 2006-09-10 11:31 pm (UTC)(no subject)
Date: 2006-09-11 09:37 am (UTC)If Mstar=1E30kg (about half the sun), Mearth=1E25kg (a slight overestimate), r=1E11m (a bit under 10AU), we get F = 1E33.G = 1E23N (about) giving a=F/Mearth=0.01m/s^2. Integrating over a year gives 315km/s, albeit presumably in a varying direction, about ten times the earth's current max orbital speed of 30km/s, which suggests cause for concern. (The sun would be moving in the same direction but, of course, much less.)
Numbers from wikipedia, calculations on the back of a bit of scrap paper, please do check for errors l-)
(no subject)
Date: 2006-09-11 10:04 am (UTC)(no subject)
Date: 2006-09-11 10:11 am (UTC)(no subject)
Date: 2006-09-12 09:11 am (UTC)Would you like to reconsider that thought? (Or do I hear Galileo turning in his grave?)
(no subject)
Date: 2006-09-12 09:15 am (UTC)(no subject)
Date: 2006-09-10 06:06 am (UTC)(no subject)
Date: 2006-09-10 11:16 am (UTC)(no subject)
Date: 2006-09-10 06:26 pm (UTC)(no subject)
Date: 2006-09-11 12:20 pm (UTC)(no subject)
Date: 2006-09-11 09:17 pm (UTC)