Quote:
Originally Posted by GlobalExplorer
Quote:
Originally Posted by Stealth Hunter
Well, for you to be sucked up, you'd have to pass within the Schwarzschild radius of the black hole (not even light can escape when it touches the radius). If you were just a foot outside of it, you'd feel sucking sensations, but you wouldn't be pulled in. You'd hear noise from the sucking, but eventually there wouldn't be anything since the atmosphere would be completely destroyed and we'd all be dead then.
Please take note that the Schwarzschild radius has an escape speed equivalent to the speed of light.
We can calculate the Schwarzschild radius by using the equation for escape speed.
vesc = (2GM/R)1/2
If you've got photons, or objects with no mass, then you can substitute c (the speed of light) for Vesc and find the Schwarzschild radius, R. This comes out to be:
R = 2GM/c2
If the Sun was replaced with a black hole that had the same mass as the Sun, the Schwarzschild radius would be 3 km (compared to the Sun's radius of nearly 700,000 km). This means that Earth would have to get very close to get sucked into a black hole in this scenario.
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with G being the gravitational constant, M the mass, and c of course light speed
I have no time to check with the suns mass, but for an object the suns size a radius of 3km sounds way off (intuitively). If it is true, first the mass of the sun would have to contract to a sphere smaller than 3km radius.
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Well, if the sun became a blackhole it would contract in to a sphere smaller that 1mm. 3km soulds like a reasonable Schwarzschild radius to me.
However, Stealth is wrong about some other bits....
A black hole sucks in things from an infinite radius in the same way the the gravity
caused by the mass of my hand attracts things to my hand from an infinite radius.
Even the most distant stars are effected by each move of my hand, but the effect
in inversely proportional to distance and proportional to mass.
The Schwarzschild radius is not the radius at which the black hole 'sucks things in'.
It is the radius at which it becomes impossible for light to avoid heading in the
direction of the singularity. i.e. it is the radius of the black bit of the black hole
when it is looked at through a radio telescope. Outside of the Schwarzschild radius
light will just be bent by the pull of the hole. Or to be more accurate, space is bent
and the light follows it.
If our sun collapsed into a singularity, the earth would continue to orbit as the mass
and gravity of the black hole would be the same as the mass and gravity of the
former sun. However, if the earth was stationary at the time, it would certainly get
sucked in from far outside the Schwarzschild radius.
If you where a foot outside of the Schwarzschild radius, but not moving closer to
the hole, you would be experiencing a force of gravity several million times that of
the Earth. That is not good for your health or completion.
