Dropping a really long object over a small, weak black hole.

[SamBridge]

So if I took a rod that had a 4 inches in radius and 5 meters long, and dropped it on a 4-inch radius black hole that hovers above ground (lets assume we have enough force to prevent the Earth from being sucked into it and to keep boht the Earth and the black hole stationary to a scientist testing the situation) in such a way that the center-of-mass-line that ran through he rod was perpendicular to the surface of the black hole, what exactly would I see? Part of the rod would look indefinitely frozen and indefinitely shrink in time while the rest of it continue to fall to the ground or something?

Edited April 22, 2014 by SamBridge

[md65536]

Do you know what calculations you might use?

 

Such a black hole is about 11.5 times the mass of the Earth. The rod wouldn't fall to Earth. I'm not sure how you'd keep those separated. There isn't sharp separation between an area where time is measured as "normal" and one where time is very dilated.

 

If you dangled a very long rod into a black hole, preventing your end from falling in, the rod would necessarily break. Along the length of the rod the farther parts would look increasingly dimmer, redder, and slowed. I guess that if the break happened when you could see it, you'd see the broken part fall in and seem to shrink or "pile up" near the event horizon without ever crossing it from your distant viewpoint.

[pavelcherepan]

I'm pretty sure first thing you'll see will be 'spagettification' - there will be a huge difference in the gravitational pull between inner and outer edges of the rod so it will be torn apart, then again, and again, and again.

 

It's possible to calculate the size of the final size of pieces that the rod will end up in - the size of pieces will be such that the difference in gravitational attaraction between inner/outer edges should be lower than the tensile strength of the material the rod is made of.

 

Then, depending on whether said black hole is rotating or not, pieces will either just come to the event horizon and would sort of get 'stuck' there progressively getting dimmer and more redshfted until they aren't visible at all. Otherwise they will spiral towards black hole with ever increasing speed, getting hotter and hotter and maybe up to the stage of emitting x-rays and then again, cross the even horizon and disappear from view after some finite time.

Edited July 10, 2014 by pavelcherepan