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Death from Space

Entry 841, on 2008-08-28 at 20:53:33 (Rating 2, Science)

As I mentioned a couple of days ago I'm listening to an audio book called "Death by Black Hole" by astrophysicist and science populariser Neil deGrasse Tyson. The section I'm currently listening to is concerned with potential space-based disasters which could cause widespread devastation of the Earth.

There are several possibilities which have varying degrees of certainty and might happen over widely varying timescales. There are also some that we can prevent and others that we could avoid, but what should we be doing in relation to these events?

How about this one. In trillions of years all of the stars will have used up their fuel and the universe will be gradually expanding and cooling with no further sources of heat and light, or any other type of energy such as that required by life. I can't think of any way of avoiding this problem except perhaps storing a source of trillions of years of more energy and ignoring the natural sources like stars. Or maybe finding a way to tap vacuum energy in some way. Its a long way in the future anyway so probably not worth getting too concerned about!

On a much shorter time scale we have the collision of our galaxy with its nearest large neighbour in space, the Andromeda Galaxy. This is due to happen in a mere 7 billion years. Various disasters could happen here. Because galaxies are mostly empty space its unlikely that many stars will collide but gas clouds would and planet orbits could easily be disturbed which might cause the Earth to fly off into interstellar space away from the warmth of our Sun. Survival options here include moving to planets orbiting other stars and hoping that some of them aren't affected or even moving out of the galaxy completely.

Before the galaxies collide there is another problem to deal with though. In about 5 billion years our Sun will no longer be able to produce energy in the efficient way it does now. It will turn into a red giant star and the Earth will be contained inside its 3000 degree surface. Clearly this is not a good thing for Earth and it gets worse. Our planet's orbit will decay because of friction with the Sun's hot gas and it will spiral into the core where it will be totally destroyed by temperatures of millions of degrees. Again our best hope is to move to another planet with a younger star although its quite possible to survive in spaceships which might not be near any stars.

But let's get on to events which might happen in a bit less time. What about cosmic rays from a nearby supernova? These could easily destroy the Earth's atmosphere by eliminating the ozone layer then allowing ultraviolet light in to convert the oxygen and nitrogen in the lower atmosphere into free atoms. This isn't quite as bad as what I have already discussed: all we have to do is survive without a life-sustaining atmosphere for a while.

A gamma ray burst from a hypernova generates 1000 times the power of a supernova (or one trillion times the energy of the Sun for a brief period). The energy is in a narrow beam though so the event would need to be fairly close and aimed in the right (or wrong) direction. There is a serious theory that this might have caused at least one mass extinction in the past though, so it cannot be ignored.

That's all the exotic stuff out of the way, what about something as mundane as an asteroid or comet collision? We are now in the area of events which could happen at any time and which we know for sure have happened in the past. The extinction of the dinosaurs is commonly blamed on a collision and, even if there were other factors involved, it must have been a major contributing factor.

We know there are several large asteroids which have orbits bringing them near the Earth and we reasonably theorise that there are many more smaller objects we don't know about. Since this disaster is the most likely to cause widespread devastation on Earth we will be tracking all of these objects carefully right? Well no. There is an effort to discover and track near-Earth asteroids but it is inadequate for providing any real protection.

Since we can't travel to other planets yet we need to protect this one. There are various mechanisms which could force the object away from its collision course or even destroy it on space but these rely on plenty of time so we need a much better survey of what's out there. Well the science funders don't seem to consider it that important and its not really happening so I guess we'll just have to hope that nothing hits us before a planetary defence system is set up.

Comment 1 (1570) by cameron on 2008-08-29 at 20:50:48:

hi hey ive been seeing some crazy videos on you tube about this nibiu planet? if its real or not then late last night i found a web site with some really good debate on the existance/nonexistance of nibiru. on a video about it on you tube someone made the claim that it can now be seen in our southern skies- he said he has photos from new zealand? the video claimed it can be seen as a red cross so today a grabbed a little tele scope from work and want to see it for myself have you ever seen it or heard of anyone who has seen this star that appears as a red cross in our skies. any response to this would be a welcome one mate

Comment 2 (1572) by OJB on 2008-08-29 at 22:34:58:

Huh? Are you for real? I have heard of Nibiru before. Its a load of pseudo-scientific nonsense, as far as I know. Have a look at the Wikipedia entry for a summary.

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