Thread: Falling into a Black Hole ... what happens?

OK ... a bit confused about the local effects of flaling into a black hole. This stems from my lack of understanding about Hawking Radiation.

If I were to fall into a super massive black hole then what happens to my space-time as I approach the EH. Does it expand as I freefall?

As I understand it the EH represents the minimum volume that can hold the amount of mass that is in each black hole. As something falls in the EH expands slightly. That is at least from the vantage point of an external observer.

For the local freefaller ... what do they experience? How do they "fit" into a volume that can not hold any additional mass?

When you fall into the Event Horizon of a black hole (let's say you are going in feet first), there is already a massive difference in gravity where your feet are compared to the rest of your body and your head. So much so that your toes would be ripped off your feet, your feet ripped off your legs and so on. The molecules would rip apart, you would be utterly destroyed. This process is called "spaghettification" since you get stretched out like, well, spaghetti..

However, let's say you were able to survive that intact. Gravity would be bending light inward so you would see much of the Universe. Also, as gravity increases, time slows down, and a Black Hole has so much gravity, time would slow down to a stand still. You would essentially be able to see the rest of the Universe happen. There are some cool computer simulated visuals out there that show what the Universe would look like to an observer falling into a black hole, I wish I had a link for you but its been a while since I saw them.

For an outside observer watching you fall into the black hole's event horizon, they would see you fall in and the image of you at that point would slow down to a stop and slowly redshift away. I don't really understand HOW that happens or why, I suppose because if gravity is causing time to slow down for you, the light coming from you to the outside observer would be slower. (the light from you just as you are hitting the event horizon, of course no more light would be coming from you after you passed through that). You however, would be seeing things speed up outside the EH.

As far as your volume fitting into the black hole, that is not a problem. All the matter in you is annilhilated, into what is unknown. I believe the polar "jets" from black holes is from matter spinning around the black hole so fast it gets ejected before falling into the event horizon, not from matter shooting OUT of the black hole. And Hawking radiation is different, it is from particle pairs right next to the black hole's event horizon - anti-particles falling away from black hole's as it's particle pair falls in before they can annhiliate each other.

Originally Posted by stereobot

When you fall into the Event Horizon of a black hole (let's say you are going in feet first), there is already a massive difference in gravity where your feet are compared to the rest of your body and your head. So much so that your toes would be ripped off your feet, your feet ripped off your legs and so on. The molecules would rip apart, you would be utterly destroyed. This process is called "spaghettification" since you get stretched out like, well, spaghetti.. .

That is only true for small black holes .... not for supermassive black holes.

Originally Posted by stereobot

You however, would be seeing things speed up outside the EH.

I am not sure about this. As your are free falling your time dilation is from SR not GR. So the universe is moving away from your and I believe the universe will appear that it is slowing down. And you will appear like you are slowing down to the universe.

Originally Posted by tom

That is only true for small black holes .... not for supermassive black holes.

I don't know if you are correct there, why would there be a difference?

Originally Posted by tom

I am not sure about this. As your are free falling your time dilation is from SR not GR. So the universe is moving away from your and I believe the universe will appear that it is slowing down. And you will appear like you are slowing down to the universe.

You very well might be correct here, I just remember reading somewhere that you would see the outside Universe move faster. I know it would blueshift, but maybe it wouldn't be speeding up... hmmm...

Originally Posted by stereobot

I don't know if you are correct there, why would there be a difference?

It is all because of tidal forces. If the EH is relatively small then tidal forces would be greater as the % would be greater between the head and toe.

For a large BH ... the difference between your head and feet would not be as great in comparison to the size of the EH ... So the tidal forces would be much less

As mass follows the inverse square rule it makes a big difference.

h--------f---------EH--Singularity
vs
h--------f---------EH-------------------------------------------------------------------------------------------------------------------Singularity

Originally Posted by stereobot

You very well might be correct here, I just remember reading somewhere that you would see the outside Universe move faster. I know it would blueshift, but maybe it wouldn't be speeding up... hmmm...

If you were hovering near the EH then the time dilation would be purely GR and the universe would appear sped up. .... as you are freefalling the effect is SR