How do you think the Earth will finally come to an end?

For life on this planet, it seems certain that once the Sun continues to evolve into a slightly brighter star, the surface temperature of the Earth will increase by 20 - 50 degrees. More water will be evaporated from the oceans, thereby increasing the greenhouse heating of the Earth. This will become a runaway process, probably in another 500 - 700 million years and will convert the Earth into a twin of Venus. It will be inhospitable for life of any kind by this time. The final coupe de grace will be delivered some 5 billion years later when the Sun becomes a red giant star, and its surface swells to envelop the orbits of Mercury and then Venus. The Earth may well loose its atmosphere at this time.

More immediately, there are many asteroids that periodically cross the orbit of the Earth, and new ones are discovered every month. Many of these will probably impact the Earth, with the same force and consequences as the one that struck the Earth 65 million years ago and caused mass extinctions of the dinosaurs. We are actually overdue for such an impact on a statistical basis, but the known asteroids of the right size are so few in number that no such impact is likely within the next million years or so. Still, there are MANY, MANY known asteroids in the 100 meter to 500 meter size class that could deliver a major blow to the Earth's biosphere, possibly in the next 10 - 100,000 years. Millions of people might die from direct consequences of the impact such as coastal tidal waves. e


Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.