So, suppose one learns all these

equations, but then finds himself in the

unfortunate position of falling into a

black hole. What would they see?

>> Great question. There's actually two

different perspectives you could take.

One is the perspective of me watching

you falling into the black hole. The

other is the perspective of you falling

into the black hole. What I see, first

you'll go faster and faster and faster

towards the black hole [music] as you

fall down the gravitational potential.

But then something strange will happen,

which is you'll stop going faster and

you'll start going slower. And the

reason you're going slower is that as I

watch you, you start to get

gravitational time dilation as you fall

down here. And I start to see you

[music] running slow, your clock running

slow. As I watch you, and presumably

using light to watch you, that light

gets more and more red shifted. The

wavelength gets longer and longer. The

longer the wavelength of light, the

harder it is even to really see you. And

eventually [music] I just stop seeing

you entirely. There's a final photon

that I see that that you emit, and then

you just fade to [music] black. I never

see you cross the event horizon.