• Question: is there any chance of the world ending?

    Asked by _jessiemanhi to Chris, Josh, Rebecca, Rob, Susan on 19 Jun 2015. This question was also asked by dumbo, CharizardXXX, Morag Marks.
    • Photo: Susan Cartwright

      Susan Cartwright answered on 19 Jun 2015:

      In the foreseeable future, no.
      The only things I can think of that would cause a genuine end of the world (as in, destruction of the entire planet) are the last stage of the Sun’s life before it becomes a white dwarf, and a collision with a large asteroid.

      A collision with a large asteroid is possible – see the dinosaur killer, which was actually quite small by asteroid standards, only about 10 km across. The asteroid 1036 Ganymed (not to be confused with Jupiter’s moon Ganymede) is about 30 times as massive; it doesn’t cross the Earth’s orbit at the moment, but a close approach to Mars (whose orbit it does cross) might conceivably direct it our way at some point in the distant future. However, we do keep an eye on all those asteroids known to cross the Earth’s orbit, and there are currently none with a significant chance of hitting us in the foreseeable future.

      When the Sun enters the stage of its evolution called the asymptotic giant branch, it will swell to be a giant star so large that it will swallow up the Earth entirely. This is definitely the end of the world, but is not scheduled to happen for about another 6 billion years.

      Catastrophes like a nearby gamma-ray burst could easily sterilise the Earth, but would not destroy it. Whether that counts as the end of the world depends on your definition!

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