• Question: how strong is a black hole

    Asked by 883sptm42 to Ollie on 2 Mar 2018.
    • Photo: Alexander Burke

      Alexander Burke answered on 2 Mar 2018:


      Good question. I had to take out a notepad to figure this one out. One could measure the “strength” of a black hole by its surface gravity. Before I go into this I need to explain a few things!
      1. Every black hole has an event horizon. This event horizon is a sort of membrane (ultra-thin film) such that if anything was to pass through this membrane then it cannot escape… it will eventually be sucked up by the black hole. Even light which could travel around the earth more than 7 times a second, the fastest thing in the universe, couldn’t escape the grasp of black holes if it passes through the event horizon.
      2. The surface gravity of a black hole is defined as (this is very complicated): The force required, as far away from the black hole as you possibly can go (at infinity), to hold an object completely still at the event horizon. The lighter the black hole the larger the surface gravity. The heavier the black hole the smaller the surface gravity. Rather strange right? This confused me at first as well.
      Now that those complicated terms are dealt with… if I was to ever fall into a black hole I would always choose the larger one. Since it has a smaller surface gravity at the event horizon I would not feel any pain once I passed through this bit. In fact, for a long time, I wouldn’t feel any pain at all until I got close to the center and I am now stretched into a long string of atoms (our very own building blocks). I would then be sucked into the singularity and dissapear forever (perhaps thrown into another universe..? who knows). This process is called “Spaghettification”… not even kidding!
      It wouldn’t be fun falling into the smaller black hole… I would likely be stripped into my fundamental building blocks far away from the event horizon!

      To summarise… the smaller the black hole the stronger in terms of gravity at the event horizon.

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