Superluminal

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12-06-2006, 07:02 PM
Oneironaut Zero

The proposition of black holes:

Quote:

If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of 500 to 1, a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light, and consequently supposing light to be attracted by the same force in proportion to its vis inertiae (inertial mass), with other bodies, all light emitted from such a body would be made to return towards it by its own proper gravity. -John Michell[/b]

Is the "falling body" the same as any object that gets "swallowed" by a black hole? (by the way, here is a pretty interesting article about a recent event CNN.com
If so, does this mean that, "at the surface" of this black hole, this star (or any other thing which has come in contact with a black hole) was travelling faster than the speed of light? Or am I misreading?

And if this is correct, does this not contradict Einsteins theory on the impossibility of superluminal travel?
12-07-2006, 12:00 AM
TheNocturnalGent

A black hole is basiclly a star whose gravity has become so strong that it has collapsed on itself and nothing, not even light can escape it. Einsteins realativity theory explains the basics of a black hole. The escape velocity needed for particles of light is lower than the amount of gravity being put on the light. Black holes and stars' gravity also cause time dialation. Mercury is close enough to the sun to experience this and i cant rememeber exacly how, but it has somthing to do with the rotation and the speed at which we view it orbiting the sun... SO if you were to look at a star and a black hole and a planet within the plain of the universe from the top it would look like this...

http://photos-466.ak.facebook.com/ip..._8466_5273.jpg

But when you throw in the dialation of time in space and you look at the grid from the side it looks like this....

http://photos-467.ak.facebook.com/ip..._8467_5494.jpg

Time and space becomes streched and distorted due to the high gravity, the larger the mass, the higher the affect.
12-07-2006, 12:38 AM
Oneironaut Zero

Now, the affect of a black hole, and its mechanics, I somewhat understand. (I think)
I do know about the gravity of black holes and stars affecting time.

My question (though I don't think I quite asked it clearly) deals with this portion of Michell's statement:

Quote:

a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light[/b]

Does this mean that any object (say, the star) passing the event horizon, into a black hole, acquires a velocity greater than light? (which is how it seems to read)
Or is it simply traveling as fast as light (in which case, the above statement seems kind of misleading)?

Quote:

The escape velocity needed for particles of light is lower than the amount of gravity being put on the light.[/b]

Now, this kind of confuses me too. Wouldn't the escape velocity needed by particles of light (I'm assuming you mean to escape out of the black hole) have to be higher than the gravity?

Would your statement mean that the escape velocity needed for light (let's say 5mph, which isn't true, but may serve as an example) being lower than the amount of gravity being put on the light (let's say 10mph) cause an object being sucked into the black hole's gravity to travel faster than light, or is it the dilation of time that's causing my confusion?

Ugh...I don't usually deal with this type of stuff, but I'm interested out of sheer curiosity...

....and my brain already hurts. @_@
12-07-2006, 03:18 AM
TheNocturnalGent

""""Would your statement mean that the escape velocity needed for light (let's say 5mph, which isn't true, but may serve as an example) being lower than the amount of gravity being put on the light (let's say 10mph) cause an object being sucked into the black hole's gravity to travel faster than light"""

thats about the jist of it. the escape velocity of a black hole is anything above the speed of light to infiniti. So if the speed of light is 5mph then the escape velocity cant be measured because we are unaware of anyhting faster than light that we can use to measure the gravity of a black hole, so a black hole, in that context can have the escape velocity of anyhting above 5mph, so it can be 5.00007 mph or it may be 10000mph, but its hard to tell because we have no way of determining its speed because any kind of radar or lightbased device would be sucked right into the gravitational field of the "black hole."

The same goes for an object that is heading for a black hole and lets say for the sake of argument that it reaches the speed of light ebfore it reaches the black hole. It would still be there and moving tward the black hole but it would be visualy uindetectable becasue light is moving too slow to bounce off of the object. Also as you reach the speed of light time for the person/object warpsfor that person or object. What seems like 20 years may actually be 2000 years andyou will be 20 years older, biologically, but those not traveling at the speed of light would be 2000 years old, a.k.a. dead.
12-07-2006, 05:26 PM
Neruo

Black holes will be black holes for ever am I right? Couldn't it be that black holes 'eat' everthing and that is the whole big-bang-big-crunch thingy basically? I can imagen a black hole growing so much it 'eats' a galaxy..

Or is there some point at wich explosion takes place?

Anyhow, the pictures... that dude posted are quite intresting, I knew heavy objects warp the time/space 'field', but can someone explain that, I don't get what is really does... time goes 'slower' in a black hole? Or faster? (looking for the outside).
12-07-2006, 11:27 PM
qzole

There was a good SG episode with a blackhole :P
So, when you are near a black hole, and I watch you from here on Earth (wich is impossible, becouse if you would be near a blackhole, light couldn't bounce off you and come to Earth, instead it would fall in the black hole), I will see you move superslow, well actually, hmmmm.... if a black hole distorts time, wich means anything near it is also distorted in time, so if you go near a blackhole with lightspeed, I'll see you go there with snail speed...

And if a black holes gravity field is "infinite", it would mean you are sucked in, but for the outside viewers, you will never reach the black hole, and for you 9284694563249357986534434 billions of thousands of years pass in a blink, and you would be the first to experience how does it feels to crash into a black hole, wich you can't share with anyone, becouse we are all dead, and you are pummeled into a black hole, and can't get out (IF you survived the crash...)
12-08-2006, 05:46 AM
Pyrofan1

Quote:

Originally Posted by Neruo

Black holes will be black holes for ever am I right?
[/b]

Black holes will eventually explode.
12-30-2006, 06:32 AM
Umbrasquall

That's just a theory. And black holes don't "grow" they're infinitely dense points of mass aka singularities. Which is also just a theory heh.

And actually you'd hit the black hole instantaneously, and die. Time doesn't slow down for you, it just seems to the outside that you're slowing down because the optical trick of light in a near event horizon environment plays on your eyes.