Wed Jan 11, 2017 10:42 pm
On 01/11/2017 04:28 AM, rickman wrote:
On 1/11/2017 3:40 AM, David Brown wrote:
On 10/01/17 15:33, Phil Hobbs wrote:
On 01/10/2017 08:27 AM, David Brown wrote:
/All/ black holes are very dense.
Nope. The bigger the mass, the lower the density. In fact not so long
ago there was significant doubt whether or not the whole universe was a
black hole (i.e. closed).
I have just done a few sums, and you are right - for supermassive black
holes, the density can be surprisingly low. The biggest ones would
float on water.
Stellar black holes are very dense, and of course tiny ones (if there
are any) are ridiculously dense.
If I am not mistaken, what spaghettifies matter falling into a black
hole is the delta in gravitational force or the gradient in other words.
With a very large black hole wouldn't the gradient be a lot less and so
less spaghettification forces? Or is this more an issue of approaching
the event horizon where the actual gradient doesn't matter?
I know from the inside the event horizon doesn't appear noticeable in
any way. I believe crossing the event horizon would be noticeable from
the outside since that it the point where even light can't make headway
against gravity. Until then you can see things between you and the
event horizon. After crossing that you can only see other things
crossing behind you.
No--the event horizon is only one way. Light falling in after you will
reach you. IIRC the only really odd thing that happens inside the BH is
that the time axis and the radial coordinate change identities, so that
there's no way to avoid hitting the singularity in a finite time.
Dr Philip C D Hobbs
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net