Susskind, Alice, and Wave-Particle Gullibility

I’ve been reading Leonard Susskind’s Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics.

Yes, I’m slow – it was published in 2008.

Susskind begins Chapter 4 with a picture and some remarkable lines – you’ll see them below – from Lewis Carroll’s 1865 masterpiece Alice’s Adventures in Wonderland. During the mad tea-party the Mad Hatter implies that light has both particle and wave properties – he appears to forsee the quantum phenomenon of wave-particle duality, something physicists didn’t think of until the following century. When they did, it settled a centuries’ old argument that began with Descartes, Hooke, and Huygens claiming that light is a wave, opposed by Newton who said it’s a particle.

The Mad Hatter and Dormouse at tea. Drawn by John Tenniel, 1865.

Is Light a Wave or Particle?

1865 was a great year for books – not only did the world receive the mega-selling classic Alice’s Adventures in Wonderland, but it also got James Clerk Maxwell’s A Dynamical Theory of the Electromagnetic Field, a mini-selling classic.

Maxwell’s epoch-making equations revealed that electricity and magnetism are actually, at the deepest level, the same force – the electromagnetic force – and that light, the carrier of electromagnetic energy, is an electromagnetic wave. In the late 1880s, Heinrich Hertz’s brilliant experiments confirmed Maxwell’s work and seemed to settle the question forever – light is a wave, not a particle.

Well, it was settled until 1905, Albert Einstein’s miracle year, when, in four classic papers, Einstein changed our world forever. He showed in one of these papers that the photoelectric effect is best explained if light behaves like a particle.

How infuriating – just when everyone had finally, at long, long last agreed light is a wave, Einstein had thrown a quantum curveball. Surely his work was crazy! Most physicists thought so, believing Einstein had messed up somewhere. They went on believing this until 1923, when Arthur Compton’s X-ray scattering experiments proved Einstein right – light could definitely behave like a particle. Yet there was a huge amount of evidence that light behaved like a wave – for example, it produced interference patterns.

Physicists realized that light’s behavior depends on circumstances – it can behave either like a wave or a particle (never both at the same time) depending on how you observe its behavior: this is wave-particle duality.

Wave-particle duality was soon mainstream science.

So did Carroll predict this in 1865? Let’s read Leonard Susskind’s quote from Alice’s Adventures in Wonderland:

Alice, the March Hare, Dormouse, and the Mad Hatter at tea. Drawn by John Tenniel, 1865.

There was a table set out under a tree in front of the house, and the March Hare and the Hatter were having tea at it: a Dormouse was sitting between them, fast asleep, and the other two were using it as a cushion, resting their elbows on it, and talking over its head. ‘Very uncomfortable for the Dormouse,’ thought Alice; ‘only, as it’s asleep, I suppose it doesn’t mind.’ Ever since her last science class, Alice had been deeply puzzled by something, and she hoped one of her new acquaintances might straighten out the confusion. Putting down her cup of tea, she asked in a timid voice, “Is light made of waves, or is it made of particles?” “Yes, exactly so,” replied the Mad Hatter. Somewhat irritated, Alice asked in a more forceful voice, “What kind of answer is that? I will repeat my question: Is light particles or is it waves?” “That’s right,” said the Mad Hatter.

For the life of me, I couldn’t remember this dialogue taking place in Alice’s Adventures in Wonderland, so I checked. Sure enough it turns out that Lewis Carroll’s prose gives way to Leonard Susskind’s. You can probably guess where.

In case you can’t, everything written after “I suppose it doesn’t mind” is Susskind.

What’s funny is finding websites that quote Susskind’s words and believe they were truly written by Lewis Carroll in 1865. It’s easy to find them – search the web using a direct quote like: “putting down her cup of tea, she asked in a timid voice.”

Search Results

I’m not sure if Susskind intended his spoof to fool people, although I have a sneaking suspicion that he did. He’s an engaging writer, and I enjoyed the book.