Why Every Dog Should Love Quantum Physics 4: Lasers

How to Teach Physics to Your Dog is now listed as “In Stock” at Amazon, so it’s the perfect time to order a dozen or so copies for your last-minute holiday gift needs.

“But, wait,” you say, “why do I want to teach my dog physics? Particularly quantum physics– why does anyone need to know that?”

The answer is: “Lasers.” Lasers are pretty awesome, right? Let’s ask an expert:

If I were creating the world I wouldn’t mess about with butterflies and daffodils. I would have started with lasers, eight o’clock, Day One!


OK, maybe he’s a bad one to ask. Still, lasers are pretty awesome, and lasers wouldn’t work without quantum mechanics.

To make a laser, you need a gain medium that consists of some material (gas atoms, ions in a solid matrix, a semiconductor diode) which can be excited to a higher-energy state, from which it will return to a lower state, emitting a specific frequency of light. This is exactly the situation that drove Niels Bohr to make the first quantum model of a hydrogen atom: Bohr needed to explain the spectrum of light emitted by excited hydrogen atoms (and all other atoms, but hydrogen came first), which consists of a few very specific frequencies of light. To explain it, he needed to introduce the idea of discrete quantum states of the electrons inside the atom, with the electron moving between states by emitting light whose frequency depends on the energy difference between the two states.

Bohr’s ad hoc assumptions were later justified with the development of the Schrödinger wave equation and Heisenberg’s matrix mechanics, which kicked off the great revolution in modern physics that we know as quantum mechanics. So, a laser is an essentially quantum device.

And lasers are everywhere, from supermarket check-out scanners to CD/ DVD/ Blu-Ray players. If you’re reading this via the Internet, lasers were almost certainly involved in transmitting the message to you, via fiber-optic communications networks.

So, if you want to know why quantum physics matters, lasers are one of the many reasons. That’s why any self-respecting modern dog should know about quantum physics, and why humans should want to teach them.

6 thoughts on “Why Every Dog Should Love Quantum Physics 4: Lasers

  1. To late. 🙂 I got my hands on the dissertation of an uncle when he graduated on the behavior of solid state lasers. Didn’t understand half of it at that time (at age 15) but it got me interested.

  2. Plus, they make great dog toys. Not as satisfying to chase as bunnies made of cheese, but much more accessible to the average dog.

  3. Dr. Geoffrey Landis published a novella with Edison, Tesla, and Mark Twain as characters. There’s a spark of evidence in Tesla’s papers (good enough for Science Fiction) that Tesla was the first human to get a crystal to lase.

  4. HEY! There is nothing in your listed bio about RUGBY!!! Please fix this ASAP – or at least by the 2nd, 3rd & 4th editions.

  5. While we’re on the topic of Niels Bohr, could you please not pronounce not his first name “Neeyels”? There’s only a single short vowel in it, namely the one you already say correctly (more or less) after “eey”.

    On behalf of all Danes, thank you.


  6. Cats are actually much more interested in quantum mechanics. My cat has spent many afternoons sitting on the couch doing calculations on how to quantize gravity in a way that correctly reduces to general relativity in 3+1 dimensions.

    And she also contemplates other hard physics questions, like, where does the little red dot hide when you turn the laser off?

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