Pack up your troubles in your old kit-bag And smile, smile, smile While you've a lucifer to light your fag Smile, boys, that's the style! What's the use of worrying? It never was worthwhile So pack up your troubles in your old kit-bag And smile, smile, smile

LEONARD SUSSKIND: ...it takes an infinite amount of time from the perspective of the outside observer for anything to get to the horizon. So in a sense, nothing ever gets there. And, uh, our description of the black hole from the outside should be then, a shell called the horizon inside of which there is nothing that will ever be important to us because from our perspective nothing ever fell through. And all the matter that fell onto the horizon is in this progressively thinner and thinner... it’s a kind of sediment. A sedimentary structure that just falls towards the horizon, never quite getting there. Now there are two things which are infinite, first for a classical black hole, the first is the time that it takes for anything to get to the black hole’s surface, and the second is the amount of information that you can hide in this thin sedimentary le- in this thin sedimentary structure that just approaches the horizon. There is no limit classically on how much structure of this kind you can have at the horizon of the black hole. Structure I mean information. Bits of information. Bits of information in classical physics can be encoded in arbitrarily weak signals or arbitrarily low frequency of energ- uh, sorry arbi- arbitrarily low energy. And so these weak signals can carry any amount, any number of bits. Any number of bits of information. And so the hidden information at the horizon of a black hole can be infinite in classical physics. Hidden information has another word- that word is entropy. So in classical physics, some people sometimes think that Bekenstein discovered that black holes have entropy. Not at all. What he discovered is that they don’t have too much entropy. That the amount of entropy they have is in fact finite. So we’ll come to that in a moment. So those two things that are infinite- the time that it takes to fall from the horizon from the outside and the amount of information that can be stored on the horizon. BRIAN GREENE: With General Relativity, we learn that the gravitational force is best described in terms of warps and curves in space and time. And that’s most directly evident at the edge of a black hole where gravity is strong and the warpage of space and time is strong. And the way we see that is if you were to go to the edge of a black hole but say have strong rocket engines so you don’t fall over the event horizon, so that you can actually say, stay in orbit around the edge of a black hole- time for you would slow down compared to the rate of the passage of time of somebody far away. So for instance, you might stay around the edge of a black hole for a week, but when you come back, say to Earth, you might find that 10 years have gone by, because your week was in slow motion. Time is running slow compared to the rate at which time was elapsing on Earth. In fact, if it was a strong enough black hole, a big enough black hole, and if you got close enough to the event horizon to the edge, (be careful, don’t fall over but stay just outside) you might spend a week at that black hole and you come back to Earth it might be a million years or a billion years have gone by. That’s the way in which black holes warp the passage of time.