Black Hole: Seeing Inside & Out

  • Thread starter Thread starter RAD4921
  • Start date Start date
RAD4921
Messages
346
Reaction score
1
It is pretty well known that you cannot see inside of a black hole from the "outside" universe. It is rather obvious as to why this is because gravity is so strong that everything including light gets sucked in but I just read that you cannot see the "outside" universe from inside of a black hole (assuming one wasn't crushed first). Why is this so? Thanks RAD
 
Physics news on Phys.org
I think it's because you can't see anything without a light source. Because you are now where it is completely dark, the only way you could see anything is if you turned on a spotlight or something but once you did turn that on all that light wouldn't go anywhere because it would be getting sucked in too.
 
RAD4921 said:
It is pretty well known that you cannot see inside of a black hole from the "outside" universe. It is rather obvious as to why this is because gravity is so strong that everything including light gets sucked in but I just read that you cannot see the "outside" universe from inside of a black hole (assuming one wasn't crushed first). Why is this so? Thanks RAD

It's not so.

See https://www.physicsforums.com/showpost.php?p=861282&postcount=5" of mine, and other posts in the thread.

Also, if the black hole is massive enough, you won't get torn apart by tidal forces before crossing the event horizon.

Regards,
George
 
Last edited by a moderator:
Well, at the singularity (point) nothing different exists to view...it's well, singular.

Inside the event horizon, but before hitting the singularity, I suppose time dilation would be so extreme that the outside universe unviewable.
 
Phobos said:
Inside the event horizon, but before hitting the singularity, I suppose time dilation would be so extreme that the outside universe unviewable.

No, at least not for the interior of an ideal Schwarzschild black hole. As I said in my post, images are seen - some blushifted some redshifted. Also, the scare quotes I put around 'at' mean in the limit as the singularity is approached.

The book Exploring Black Holes by Taylor and Wheeler gives a readable account of how to derive just what is seen.

Regards,
George
 
Last edited:

Thread 'Describing the Big Bang'

I started reading a National Geographic article related to the Big Bang. It starts these statements: Gazing up at the stars at night, it’s easy to imagine that space goes on forever. But cosmologists know that the universe actually has limits. First, their best models indicate that space and time had a beginning, a subatomic point called a singularity. This point of intense heat and density rapidly ballooned outward. My first reaction was that this is a layman's approximation to...
View full post »
Thread 'Dirac's integral for the energy-momentum of the gravitational field'

Thread 'Dirac's integral for the energy-momentum of the gravitational field'

See Dirac's brief treatment of the energy-momentum pseudo-tensor in the attached picture. Dirac is presumably integrating eq. (31.2) over the 4D "hypercylinder" defined by ##T_1 \le x^0 \le T_2## and ##\mathbf{|x|} \le R##, where ##R## is sufficiently large to include all the matter-energy fields in the system. Then \begin{align} 0 &= \int_V \left[ ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g}\, \right]_{,\nu} d^4 x = \int_{\partial V} ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g} \, dS_\nu \nonumber\\ &= \left(...
View full post »

Thread 'A sufficient condition for integrability of equation ##\nabla g=0##'

In Philippe G. Ciarlet's book 'An introduction to differential geometry', He gives the integrability conditions of the differential equations like this: $$ \partial_{i} F_{lj}=L^p_{ij} F_{lp},\,\,\,F_{ij}(x_0)=F^0_{ij}. $$ The integrability conditions for the existence of a global solution ##F_{lj}## is: $$ R^i_{jkl}\equiv\partial_k L^i_{jl}-\partial_l L^i_{jk}+L^h_{jl} L^i_{hk}-L^h_{jk} L^i_{hl}=0 $$ Then from the equation: $$\nabla_b e_a= \Gamma^c_{ab} e_c$$ Using cartesian basis ## e_I...
View full post »

Similar threads

I Can light be reflected in a black hole?
Replies
22
Views
1K
B Can we see 2 black holes orbiting each other?
2
Replies
57
Views
4K
I You can't actually enter a blackhole?
Replies
40
Views
3K
I Supermassive black hole, surface gravity and tidal forces
2
Replies
62
Views
7K
B Can anything work (including human brains) inside a black hole?
Replies
22
Views
1K
I Falling through the event horizon of an evaporating black hole
2
Replies
51
Views
4K
B Question about the Entropy of a Black Hole Singularity
Replies
17
Views
3K
I Escape from Two Black Holes? Solve the Mystery!
Replies
2
Views
2K
I Falling into a Black Hole: Blueshift Questions Explored
Replies
11
Views
4K
B Is there an inside to a Black Hole?
2
Replies
63
Views
4K

Hot Threads

Recent Insights

Back
Top