How much longer will the Earth last?
What is the estimated remaining life time for the earth?
The upper limit on the lifetime of Earth is about 5 billion years. In about 5 billion years, the Sun will have used up its hydrogen reserves and will expland to become a Red Giant, with a radius of about Earth's orbital distance. The Earth will most likely be swallowed up when this occurs.
The Earth will only make it that far, however, if it avoids a collision with an asteroid or comet large enough to blast it apart. The movies Armageddon and Deep Impact seem implausible, but an Earth-destroying collision is possible. For example, a theory for the formation of our moon is that a body the size of Mars collided with the Earth, throwing debris into orbit that collected to become the Moon. A slightly larger body would have destroyed Earth. According to experts, a "civilization-threatening" impact (such as the one that ended the age of the dinosaurs) occurs about once every 200,000 years. The frequency of an Earth-threatening impact is much much larger, but it is still possible that a body large enough to destroy Earth may arrive in the next 5 billion years. However, civilization may have developed technology that could allow us to alter the path of such an asteroid or comet and save the Earth. So, actually, it's hard to say just how much longer Earth will be around. But I'd venture to say a long, long time!
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