• Question: If black holes exist and even light is sucked into them, why isn't the whole world sucked into one?

    Asked by maddiet to Mark, Matthew, Mike, Paul, Sabina on 13 Mar 2014.
    • Photo: Sabina Hatch

      Sabina Hatch answered on 13 Mar 2014:


      Black holes uses gravitational force to pull objects toward itself. But actually gravity is by far the weakest force we know of. Even though black holes have a very strong gravitational force, its effect on an object depends strongly on the distance between them. If a black hole was close enough to our position then we would and everything around us will be pulled towards it.

    • Photo: Mike Lee

      Mike Lee answered on 13 Mar 2014:


      Luckily there is no black hole near us so we are not in danger of falling in to one.

    • Photo: Mark Jackson

      Mark Jackson answered on 15 Mar 2014:


      First a bit of physics history which is not often told.

      In 1972 a young physics Ph.D. student named Jacob Bekenstein suggested that black holes contain something called “entropy” which is basically how much information it contains. Entropy was a property commonly appearing in thermodynamics, but the idea that it would be in a black hole was strange – where would the information be? People were pretty skeptical about this suggestion. In fact, a certain other physicist named Stephen Hawking suggested what he thought was a great argument against the idea: if black holes had entropy, like other thermodynamic quantities they would also radiate. And black holes suck everything in, so they couldn’t possibly radiate! But when he started to perform the calculation, he realized something subtle: the radiate couldn’t emerge from *inside* the black hole, but it could emerge from *near* the black hole. In quantum physics there are often pairs of particles and antiparticles appearing and disappearing near the edge. And if a particle escapes from outside the black hole, the antiparticle will have to remain inside – but being an antiparticle, the black hole will *lose* energy! So he proved that black holes do indeed radiate, called “Hawking Radiation.” Not since the Poisson Dot (see http://goo.gl/yeHj2I) has someone tried so hard to prove a theory wrong, only to prove it right! Since this continues to happen until the black hole disappears, a more accurate description would be evaporation!

      To answer your question: a black hole near us would certainly suck us in. But eventually it would have to evaporate and release the matter back into space, which is why the whole Universe is not just a big black hole.

    • Photo: Paul Coxon

      Paul Coxon answered on 17 Mar 2014:


      The nearest blackhole to us is very very far away so its effect of pulling us in is very remote indeed.

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