Don’t worry, you should feel fine. This isn’t going to be a doomsday treatise that keeps in line with such films as Deep Impact, Sunshine, or Armageddon. There are no reports of gamma ray bursts heading our way for me to report on; no Planet X slowly cruising towards us on a collision course like in Melancholia. No, the end of Earth as we know it will be far less immediate than any Hollywood story currently out there or in development. The raw deal according to a recent article published in Astrobiology by Andrew Rushby is that the Earth has spent about 70% of its lifetime in the Sun’s habitable zone and in time will be consumed by the expanding growth of the sun. But let’s not give away all of our possessions just yet. The end of the world won’t exactly happen any time soon.
Keep in mind scientists have to consider how long a planet has been within this habitable zone for it to develop signs of life: a planet forms, 1 to 2 billion years to form microscopic life, another 3 or so billion years for the development of man, add in some time for the development of technology. Now, according to Rushby and his associates, they have to consider the long term sustainability of the star itself. With all this information to consider it will help astrobiologists narrow down the number of planets that they consider to actually have life sustaining qualities.