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Loop of pumped fluid slowly falling into black hole. 
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#1
Dec1012, 03:24 PM

P: 18

You have this loop of water (or some other "incompressible" fluid) with a nuclear powered water pump that constantly pumps the water in a circle. This loop is slowly lowered near the event horizon of a black hole, lets even make it a super duper massive black hole to minimize tidal effects, it's "slowly lowered" so we don't have a super fast moving loop of water, and my pump is nuclear powered so it can pump against massive head pressure :)
So what happens when part of the loop crosses the event horizon? Specifically what does the fluid do? Now obviously the fluid can't get pumped back out past the event horizon, and in an ideal case fluid wouldn't be pumped into the now missing part of the loop because the fluid would occupy that space and there'd be no way to put more in there... however since it's within the event horizon no information about there being fluid can make it back outside, so how would the fluid outside of the event horizon "know" that it can't go into that other section of pipe. I know that it would be pulled into the SMBH eventually, but what happens to the fluid which the pump is trying to move through the loop. Reason for question: I was watching Stargate and was thinking about this and all these shows that have this "portals" to move you from one location to the next, more specifically that these portals are one way only (yeah you can go both ways in Stargate but you have to reopen it from the other side IIRC). So I started wondering about how that would affect the physiology of life going through these one way portals, now it's glossed over as "fictional" but still had me wondering, blood is pumped in different directions in the body, nerve endings send electrical signals in different directions too, and blood (or electrical signals) pumped "forward" in your body wouldn't be able to come "back" until you completely went through said portal. So rather than come up with this question, I simplified using the only oneway portal I know of (event horizon) and used a loop of fluid. 


#2
Dec1012, 03:29 PM

Mentor
P: 11,928

You can get a pipe through the event horizon, if you just let it fall (and hope that tidal forces are small enough). 


#3
Dec1012, 04:33 PM

P: 18

*sigh* ok my head hurts and I still need to write a final for one of my astronomy classes. 


#4
Dec1012, 06:55 PM

P: 166

Loop of pumped fluid slowly falling into black hole.
I think it's an interesting question even if the formulation is a little.. odd.. ;) Why not simplify. I'm inside the EH of an SMBH holding one end of our carbon nanotube rope, you're on the outside holding the other. I give it a yank. Do you feel it?
The science says "nope" so the question is, what happens to the rope. Does it just stretch or break apart? 


#5
Dec1012, 07:45 PM

P: 700

Now we all know that is impossible because nothing can travel at C. It won't make sense until you revisualize motion through space and time as a single path through 4space. Imagine a clock moving through 4space, leaving an imaginary line behind it. Every time the clock ticks it leaves a dot on the line. The length between the dots is always the same. If the dots are at the same x coordinate they are 1 second apart on the t coordinate, if they are 300,000 km apart on the x coordinate then they are at the same t coordinate. If both the x and t coordinates change then the Pythagorean theorem describes the relationship between how much they each change. Intuitively we separate time from space and measure time in seconds and space in meters, but this distinction is purely artificial. 1 second actually does equal about 300,000,000 meters. Seconds and meters are different units for the same quantity. Gravity twists these coordinates so that what looks like a space coordinate from a distance (like distance from a black hole) becomes a purely time coordinate at the event horizon. At that point the ship is not actually moving toward the black hole at 300,000 km/s which would be impossible, it is moving toward it at 1 second per second. The B.H. is no longer in front of the ship, but in it's future. 


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