Monday, 10 March 2014

Explanations

I am going to tell you one of my favourite stories about a scientist revealing a gaping hole in the trousers of his superhero costume  about Einstein, no less  but unfortunately it will require me to explain some technical concepts, and I must offer a disclaimer in advance. Several disclaimers, in fact.

Explanations of any kind are a weighty responsibility. I have to be sure I really do know what I'm talking about, and there's nothing the human brain does better than convince you that you know what you're talking about. I was once entering a concert in Los Angeles that would include Tchaikovsky's 1812 Overture, which is probably one of the most famous and recognisable pieces of music in the Western world, and I overheard a little girl ask her mother what it was about. The mother confidently replied, "The War of 1812." If you read my last post, you'll guess that I did precisely nothing to correct either the daughter or her ditzy mother. All the experience did was burn a horrified memory into my brain, from whence it is broadcast back to you now.

The dangers of this sort of self-delusion are even greater when trying to explain complicated physical theories. In some cases I'm protected by a clear knowledge of my ignorance. For example, quantum mechanics. After my last quantum mechanics exam at graduate school, I was called into the professor's office, and he told me, "We're going to let you pass, but if ever in your future research you need to do any quantum mechanical calculations  don't! Get someone else to do it for you, because you obviously don't understand a thing."

This is the memory that flashes through my mind when some hapless student comes inexplicably to my office and says, "Excuse me, I'm having a problem with my quantum mechanics homework. Can you help?"

I'm immediately thrown into a panic, and will blurt out the first excuse that leaps into my mind.

"I'm sorry, I have to leave now to go and pick up my son from school."

"Now? It's only 11 o'clock in the morning."

"I have to get him early. He was stabbed in the playground."

"Stabbed!? Where to do you send him to school?"

"South Central LA."

"In America?"

"And what with the long flights from the UK, and dealing with huge Californian hospital bills, and nursing him back to health, and maybe rethinking our choices about his education, I expect to be away for the rest of the course. So ask your questions to someone else."

I only say this because I'm terrified they want help with some fiendish calculation involving Clebsch-Gordon coefficients. In reality they just want to know how to spell Schroedinger. But in matters of scientific explanation, it's always better to err on the side of caution.

With non-technical "popular" explanations it is far worse. Let's be honest here. You know and I know that popular explanations of science are a cheat. Any given scientific concept will be based on a host of other concepts, each of which requires days or weeks or longer of mulling over and confusion and "But what about..?", until you can finally delude yourself that you've made sense of it and move on. It requires years of training, and even among the seething ranks of tenured academics, there are only a handful who know what the hell they're talking about. So it is entirely dishonest, not to mention insulting, to sum up an entire research field in four sentences and then say with a smug smile, "Simple, huh?"

For an excellent illustration of these things, I turn, as one so often does, to good old Feynman, whose educational skills were a fantastic contradiction in themselves. He is famous as a great educator, yet trained an appallingly low number of graduate students. He wrote a classic series of entry-level university textbooks, which are notorious for being impossible to teach from. He claimed that if you couldn't explain a scientific concept to a child, then you didn't properly understand it. Yet he also provided what I consider one of the greatest examples of the difficulty of teaching scientific concepts to the uninitiated. When asked to explain how magnets work, he essentially refused:
If I said that magnets attract as if they were connected with rubber bands, I would be cheating you, because they're not connected with rubber bands… If you were curious enough you'd ask me why rubber bands tend to pull back together again, and I would end up explaining that in terms of electrical and magnetic forces  which are the very things I was using the rubber bands to explain, so I have cheated very badly, you see.
This very quotation ran through my head when my seven-year-old son asked me how magnets work. If he was stuck in a hospital bed for several weeks recovering from stab wounds, perhaps I could have come up with something reasonable, but I'm told that this is not the right attitude to parenting. Instead I simply stood in front of him for a full thirty seconds with my mouth hanging open, until he decided to go and find a normal parent to play football with.

It's no better when I come across someone in a pub who exclaims, "I love physics! I know all about Professor Hawkins, and I've watched all of the TV shows from Professor Brian Cox! I find physics fascinating!"

The classic wits of centuries past would have known how to respond. Churchill wouldn't have hesitated to remove his cigar from his mouth, puff out his chest, and agree, "Physics truly is fascinating, sir, but you are not."

I'm left trying to explain black holes. A black hole is an object with a gravitational pull so strong that even light cannot escape. Why can't light escape? Because the escape velocity is greater than the speed of light, and nothing can go faster than the speed of light. Why not? Because Einstein worked out that this is a logical consequence of Maxwell's theory of electromagnetism, which predicts the same speed of light in vacuum, irrespective of your relative velocity to the source. And why does Maxwell's theory predict that? That's an extremely good question, and I'm afraid I don't know the answer, and I doubt I can find out right now while we're talking here in this pub.

But it's unlikely we'll have got to such a deep level, because my intrepid interlocutor was very likely either (a) one of those irritating people who try to convince you that surely things can travel faster than the speed of light, it's just that we haven't worked out how yet, or (b) an ordinary human being who was lost at "escape velocity" and has realised that making sense of this could take many months indeed, and, anyway, much like Forster's Mrs Munt, they've secured their nut, in the form of a one-line description of a black hole that might come in handy one day in a pub quiz, and now they're ready to go off and find a normal person to talk football with. Plus, that wasn't even very technical  the same explanation could have been delivered by an above-average high school student or a below-average university graduate. What would happen if I were to try and explain the subtleties of a scientific argument that even Einstein got wrong?

I suppose we'll find out in my next post, when I try to do exactly that. Just don't expect me to do it very well.


5 comments:

  1. Poor kid. Not sure where he's going to find a normal parent to play football with . . .

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  2. Whose QM class did you have in grad school?

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    1. Hmmm.... I remember being very disappointed that Merzbacher had quit teaching QM a couple years before I got there, then re-started a couple years after I took it because of the disastrous instruction in the intervening years. (For which I can thoroughly vouch.)

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    2. I don't remember much about Hernandez's course -- I suppose that was part of the problem. But I did go to some good summer parties at his house, and there was very good sangria, so I can't really complain. I just regret that I missed the bad old days when he smoked during his own lectures, and contemptuously blew smoke at anyone who complained.

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