Common misconceptions thread
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12-01-2012, 07:21 PM
Join Date: Aug 2010
Location: Richmond, B.C.
Just gonna copy my response from the "Enormous Black Hole Discovered" thread.
Originally Posted by
Plan The Parade
Are there any stars that are big enough to go supernova and cause a black hole of this size? This seems very unprecedented.
It also makes you realize that, if a black hole appeared anywhere close to our solar system, we are screwed (unless nuking black holes works).
Here's something that I'll add to the common misconceptions thread.
Black holes are not magic vaccuum cleaners. If faraway giant star does not have enough mass right now to suck in the earth, then it will still not have enough mass to suck in the earth when it collapses.
If the sun somehow turned into a black hole with the exact same mass, none of the planets would be sucked in. The orbits would be almost the exact same.
To add to the above:
Black holes were theorized first as a very good approximation of a stellar body from far away. It wasn't until several (can't remember dates) years later that people realized that this very useful approximation had ugly, ugly properties when you got very close to it.
They created this approximation because Einstein's field equations for GR are horrendously scary.
Moral of the story: from far away (ie: outside the event horizon), treat the movement and gravitational effect of a black hole the exact same way as you would treat a star of equal mass.
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