• Question: Could one get behind a black hole? Or are they spheres? As well as that, how come black holes haven't destroyed the universe in the couple billion years they've had to get going?

    Asked by infintaneousdeath to Joel, Kristian, Tim, Venus, Zachary on 14 Nov 2013.
    • Photo: Kristian Harder

      Kristian Harder answered on 14 Nov 2013:

      Yes, you can get around black holes. They are kind of spheres of materials, and you can circle around them and look at them from all sides. 🙂 A much bigger question is whether you could get *inside* one, but it is unlikely that anyone could survive getting in. I don’t think anyone has tried though, and even if anyone did, due to the nature of a black hole they couldn’t send a message to us outside telling us whether it worked. 🙂
      Black holes haven’t sucked up everything in the universe for the same reason that the sun hasn’t sucked up the planets in the solar system yet. Unless you aim directly at a black hole (or a sun), you end up in an orbit around it rather than falling into it. And without friction or any big objects coming close enough to disturb your orbit dramatically, you’d stay in that orbit for billions of years. That’s for example happening with our galaxy. Scientists suspect that there is a black hole at the centre of our galaxy, but we and all the stars around it just keep circling around it. Only objects in the very centre of the galaxy, with their rather chaotic paths due to large number of massive objects in little space, really end up falling into the black hole.
      Eventually, of course, if you wait for much much longer, every object will sooner or later hit the path of a black hole, get absorbed, and the universe will become darker and darker… But the universe is so huge that despite the large number of galaxies and stars and black holes in it, the chance to cross the path of a black hole is so low that billions of years have not been enough for the black holes to suck up everything else in the universe.

    • Photo: Tim Hollowood

      Tim Hollowood answered on 15 Nov 2013:

      yes you can go round a black hole…they are spherical like a planet. Black holes haven’t destroyed the universe as Kristian explains very beautifully but it seems that they are crucial for the fact that galaxies exist in the form they do. Every galaxy has a supermassive black hole at its centre even our own Milky Way. So we are beginning to see that black holes are very important otherwise our galaxy wouldn’t exist in the form it is and so maybe we wouldn’t exist.

    • Photo: Zachary Williamson

      Zachary Williamson answered on 15 Nov 2013:

      Black holes are spherical, so yes you can travel around them. They haven’t destroyed the universe because their ability to suck in matter is limited by their mass, which in most cases isn’t usually that large.

      For example, you can look at telescope pictures of nearby galaxies, and the center-parts of most galaxies will be almost completely empty. That’s because almost every galaxy we know of has a supermassive black hole in the middle that’s chomped on all the nearby matter. But, as I said before, their reach is limited. Space is big. Really, really big. And even the largest black holes are ‘only’ the size of our Solar System, which compared to the rest of the universe is absolutely tiny.

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