# The Naked Scientists Forum

### Author Topic: View from inside a black hole  (Read 1207 times)

#### syhprum

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##### View from inside a black hole
« on: 31/01/2012 21:46:00 »
If one was to pass thru the event horizon of a super large black hole and looked back what would one see? and would one continue to accelerate towards the centre and at what rate ?

#### Soul Surfer

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##### Re: View from inside a black hole
« Reply #1 on: 31/01/2012 23:31:51 »
Once you are inside the event horizon you see exactly the same thing in every direction and that is whatever "the centre" of the black hole looks like.  This is because in every direction rays of light are bent round to reach the centre

You could also see or detect blue shifted photons and particles falling in from outside.  There might be an extreme tunnel vision image of a small area of the outside world exactly opposite the direction you are being accelerated.

You would continue to accelerate towards the centre at an accelerating rate as the gravitational field gets stronger towards the centre The actual values of acceleration depend on the size of the hole but for a one billion solar mass black hole about 20 astronomical units across (the size of the orbit of Uranus) your initial acceleration just inside the event horizon would be about 1,500 times the earths gravity or 15,000 meters per second per second

However once your velocity was relativistic your velocity increase would reduce but your kinetic energy would still increase in line with the amount of gravitational potential you have fallen through.  the limiting velocity is of course close to that of light.  your view of what is around you would also be distorted by relativistic effects expanding and blue shifting what is in the direction of travel and red shifting and compressing what is opposite to your direction of travel.

Because you are in free fall you would not feel this high acceleration until the differential gravitational field became strong enough to tear you apart in the last tiny bit of your fall .  You would be falling for around an hour or two before you got to the centre.

This of course assumes that you are falling through empty space

main information source  http://xaonon.dyndns.org/hawking/
« Last Edit: 31/01/2012 23:36:57 by Soul Surfer »

#### imatfaal

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##### Re: View from inside a black hole
« Reply #2 on: 01/02/2012 10:12:58 »
Once you are inside the event horizon you see exactly the same thing in every direction and that is whatever "the centre" of the black hole looks like.  This is because in every direction rays of light are bent round to reach the centre

You could also see or detect blue shifted photons and particles falling in from outside.  There might be an extreme tunnel vision image of a small area of the outside world exactly opposite the direction you are being accelerated.

Soulsurfer - not sure about this.  You will certainly not see anything from the centre - but light from the outside will still be detectable.  I visualize it as follows (thinking of little packets of light and obviously ignoring real physical effect of being torn apart) - looking outwards, the blackhole behind you would act as an enormous gravitational lens - eg light from over your left shoulder, which in normal circumstances you could never normally see will be bent back and you will be able to see the source.  From everywhere apart from mysterious centre there will be light that normally you couldnt see that will be bent back to your perception - ie you wouldn't see space in the same way as normal  - but you could still see it (in fact I think you would see almost 360 degrees).  The closest real world analogy I can think of is the fish eye effect of taking a photograph from under very still water - the refraction means that you get a complete hemisphere picture.  in the water example the light is directed by the refraction, in the black hole by gravity

#### Soul Surfer

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##### Re: View from inside a black hole
« Reply #3 on: 02/02/2012 23:12:22 »
Thats just what I said in a simple version

#### The Naked Scientists Forum

##### Re: View from inside a black hole
« Reply #3 on: 02/02/2012 23:12:22 »