If center of galaxy is supermassive blackhole

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  • #26
Drakkith
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can we use black hole gravity to help increase speed of spacecraft?

I use to watch documentary about idea to explore solar system, it seem that swing ship across planet and it's gravity can help increase speed of the ship.

can we use black hole in same theory?
Sure, but only if the black hole were moving in a favorable direction. A spaceship steals some of an planets orbital angular momentum when speeding up and gives the planet some when it slows down, but this is only relative to a "fixed" observer, in our case the Sun. Note that the sun is moving too, but in regards to the solar system it is stationary. See here for more: http://en.wikipedia.org/wiki/Gravitational_assist
 
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In simple terms, The Black Hole is sucking in everything in the Galaxy. Eventually even those of us on the outer perimeter will be sucked in. We are all doomed. Though this may take another 30 billion years,
 
  • #28
DaveC426913
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In simple terms, The Black Hole is sucking in everything in the Galaxy. Eventually even those of us on the outer perimeter will be sucked in. We are all doomed. Though this may take another 30 billion years,
No. This is wrong.

1] Black holes have no more sucking ability than any other body (or collection of bodies) of the same mass.
2] Milky Way's BH is on the order of a million solar masses, but the galaxy's core contains hundreds of thousands of times more mass than that in the form of stars. The BH is a pretty small player in the gravtiational grand scheme of things.
3] http://physicsworld.com/cws/article/news/41370" that suggests the BH's appetite is one hundred times smaller than the 1% previously thought.
 
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  • #29
cepheid
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In simple terms, The Black Hole is sucking in everything in the Galaxy. Eventually even those of us on the outer perimeter will be sucked in. We are all doomed. Though this may take another 30 billion years,
Really? I thought that was going to happen, like, at the end of 2012 or something...:rolleyes: :tongue2: :devil:

In all seriousness though, DaveC's point below (highlighted by me) cannot be emphasized enough:

No. This is wrong.

1] Black holes have no more sucking ability than any other body (or collection of bodies) of the same mass.
To drive this point home: As a simple thought experiment, if you could magically and instantaneously replace our sun with a black hole of the same mass, the orbits of Earth and the other planets would not change. Outside the event horizon, matter interacts gravitationally with the black hole in exactly the same manner as it would with any other body of the same mass. It's only beyond the event horizon from which matter cannot escape and is doomed to be "pulled in" to the singularity. Black holes don't suck.
 

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