Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: FRANK SHEPHERD on 05/08/2010 11:30:02

Title: What do you see as you enter a black hole?
Post by: FRANK SHEPHERD on 05/08/2010 11:30:02

FRANK SHEPHERD  asked the Naked Scientists:
   
Hi,
 
Imagine two people, each sitting inside separate spaceships.
 
The spaceships are falling into two different black holes simultaneously.
 
If they watch each other falling, what would they see?

What do you think?

Title: What do you see as you enter a black hole?
Post by: Soul Surfer on 09/08/2010 23:49:30

This is a rather artificial and hypothetical question because it is virtually impossible for such an observation to be made.  In theory it would be a combination of the view from outside a black hole of someone falling in and the view out of a black hole for someone in the process of falling in.

The first is described as a fading, time stretched and red shifted image of the object that is falling in.   In theory this never fades but that is a bit like saying that a hot object never cools down becaus it is an exponential process and in fact the fading to invisibility would probably be quite quick.

The view looking out as you fall in is a narrowing and blue shifted image of the outside world looking directly away from the black hole. 

However that only applies to Schwarzschild (non rotating) black holes and these do not happen in reality because all black holes will be rotating ones and probably rotating quite quickly and near the limit that they can rotate (Kerr black holes)  because of this space itself is dragged round with the rotation by the gravitomagnetic effects and even something trying to head straight for the centre is forced to orbit the hole for a while so the objects would probably rapidly move out of sight of each other.