The Perimeter Institute Lectures Wind up with the Black Hole Wars

Leonard Susskind

The very interesting series of Perimeter Institute Lectures run at the Bruce County Museum this fall is now complete for the year.  It is to begin next fall again.

It certainly is a treat to be able to see some of the world's greatest minds on display in a very comfortable setting.

Today, November 19's lecture featured Professor Leonard Susskind from Stanford University in California.

What's been amazing about these lectures is how funny and entertaining these people are.  We know that as a rule comics are very smart, but sometimes at least very gifted people are funny too!

Professor Susskind led off with an explanation of why his presentation was so low tech (using an overhead projector).  It seems that when he was 25 and just finished his PhD, he had the opportunity to give a lecture at the Princeton Institute for Advanced Study.

Very famous people were in the audience and Susskind was nervous, very nervous.  They had an early version of the overhead that required him to put a piece of paper and 'crank' it into position under intense light and therefore heat. Picture a crank and a heat and light chamber.

His mother had bought him a new suit and he accompanied it with a cheap tie, not tied correctly leaving a long 'tail'.  As he fumbled the next document into the display chamber, his tie got caught and he could not extract it.  Finally it burst into flames and he was rescued by some of the famous people in the first row, which included Robert Openheimer.

During his lecture today on Black Holes, he inadvertently put his slide on the podium, squared it and then looked at the screen.  Seeing nothing, he was mystified.  The audience began to titter.  Realizing his mistake, he gathered the errant slide and put it on top of the overhead viewer showing good humour.

He led into the lecture by referring to a 25 year long discussion about the nature of Black Holes.  On one side was the famous Hawking and on the other the great Gerardus 't Hooft teamed with Susskind himself

He told an amusing story about being out on the town in San Francisco with 't Hooft and Hawking.  They were at the top of Telegraph Hill, which is known from many movies and TV Series episodes with cars careening down it. (picture Steve McQueen)

Evidently to the horror of Susskind and 't Hooft, Hawking's wheel chair got out of control and he shot down the hill with the physics guys reviewing the true nature of gravity's effect on the Cambridge genius.

When they finally caught up with the famous man, he was grinning wildly.  Keep in mind that 25 years later, unable to speak, he still wants to go up in space and become weightless.

(next column)

13/01/2009 04:23 PM


So what were these Black Hole Wars all about.  According to Susskind, Hawking is a man who reaches out and is not conservative in the sense of science.  He takes risks in his theories and likes to tip his hat at basic laws.

If you look at the picture above you see a Black Hole.  It has these powerful gravitational forces that don't allow light to escape and therefore everything is dark.  At the centre of our own Milky Way there is a Black Hole.  How do we know anything about them, if we cannot see them? 

We know because of what's around them is drawn toward what is called the Event Horizon.  That's depicted in the band like circle around the hole above.  Beyond that point nothing can escape.  It's like getting too close to Niagara.  If you cannot go faster than the flow, you are sucked in for good.  In the case of the Black Hole this happens at the event Horizon because nothing can go faster than the speed of light and so nothing can escape.  So in order to resist, you have to go the other way at near the speed of light, but your mass would grow and resist your efforts, so away you go into the hole.

So what was the 'war' all about?  Hawking said and proved, at least to himself and many others, that all 'information' going into a Black Hole is lost forever.  This is information in the most general sense.  Our body is an information cache because it is us.  It has it's own matter and organization. So our information is how we are organized.  That's the case with all matter and energy.

Well, 't Hooft and Susskind disagreed because lost information violated one of the most basic laws of Physics  ... nothing is ever lost.  It just changes form.  For example, if two trains crash head on, lots of information is really not lost.  It's converted into heat, but that's just another form of information.

They posed a number of thought experiments like Einstein used to do.  One had Alice going over the edge of the Black Hole and being observed to do so by her friend Bob and according to Hawking, being lost forever.  But how do we know?  We can't get a message from her because according to Hawking, she is just blitzed ... poof.

But, 't Hooft and Susskind pointed out that according to Thermodynamic principles, information is never lost.  It can be scrambled, dispersed, converted from one form to another, but never lost.

From elementary physics we know that information in a chamber of gas is proportional to volume.  Like the room you're sitting in reading this has your computer, some chairs, books and air.  The amount of 'information' is proportional to the volume or is it?

According to Susskind, the 25 year war ended when Hawking agreed that the information in the Black hole is really proportional to the surface area of the Black Hole.  That is a Black Hole is kind of like a space hologram with all the event information stored is some form on the  surface.

Stated as Susskind and 't Hooft would phrase it

"...For a Black hole, the principle states that the description of all the objects which fall in is entirely contained in surface fluctuations of the event horizon."

".... the theory suggests that the entire universe can be seen as a two-dimensional information structure 'painted' on the cosmological horizon, so that the three dimensions we observe are only an effective description at low energies."

So maybe Alice is recorded on that rim of the horizon as she disappeared from the mystified and cautious Bob's view?

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