Today I read an article in scientific American titled, “Earth’s Days are Numbered”. The article started off with an estimate of the number of years the Earth will be able to support life as we know it; 1.75 billion. While that number is longer than most can even comprehend, it is still less than might have been previously thought. New models and forecasts for the sun put the Earth closer to the inside edge of the habitable zone than we previously thought.
The habitable zone is the area in which water can liquefy. Too far away and the water will freeze, too close and it will be gas, both rendering it useless to any life we know of. Though in a human lifetime the habitable zone seems static, over the life of a star the habitable zone can fluctuate dramatically. As a star reaches the end of its life and starts to expand it will push the habitable zone outward as well. The habitable zone’s current rate of movement is around one meter per year.
With this model researchers have been attempting to see planets that may be in the habitable zone of their star when we are moving out of ours. While it is interesting to see new potential homes for Earth’s life, it has been suggested that the formula the researchers used for the model is too simple. Without important information regarding the atmosphere and tectonic activity of the planets in question it is impossible to say if they could actually support life in the future. Though the primary use of this model has been for extra solar planets it has also been used closer to home. In around one billion years mars will be entering the habitable zone, if humans are still living, they may find refuge from the sun there.
Though the habitable zone may be redefined in the future, this still give us a rough idea of which planets could conceivably support Earth’s carbon based, water dependent life. One thing that I could not help but think though is that this may be a bit too premature. A billion and a half years is a really long time, longer than anything I can even imagine. I find it hard to believe that there will even be humans in a billion years, and if there are they will probably not share much in common with us. This may be pessimistic, but I think that by the time we are in need of a new planet, Humans will not be around to deliver life to it.
The article can be found here
