Turtles All The Way Down

There’s a old theory, that was most famously cited in Stephen Hawking’s book, A Brief History of Time:

Turtles All The Way DownA well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever”, said the old lady. “But it’s turtles all the way down!”


We always try to understand the world around us. We live and learn about the things we see and touch. We make stories to explain what these things are, and why they behave the way they do. Humans have a tendency to make up stories, stories that explain the world as best as we can.


Richard Feynman was a wonderful storyteller. He was also one of the greatest physicists of our time. A man with limitless curiosity and strong character. This is a short excerpt from an old interview with him, in which he explains why he cannot explain how magnets work. This is the integrity of a physicist who refuses to cheat. Most people, he explains, have a problem separating the analogy from reality. Where does the analogy end and reality starts? It doesn’t. There are turtles all the way down.

If you want to hear more of his stories, read his highly recommended autobiography, Surely You’re Joking, Mr. Feynman!


So what is a good explanation? Most scientists will tell you a good theory predicts a phenomenon, and thus both explains the existing knowledge base and is then confirmed by observation. Testability is not enough, though.

Even old myths were testable. When the ancient Greek believed winter is caused by the sadness of gods. In this myth, there’s a sad story of forced marriage. This is a theory that is easy to test (and prove false, because when it is winter in Greece, it is summer in Australia). However, we could have spun a different story which would have been testable. For example, having the sad god walk the Earth once a year, bringing winter where ever he goes.

The problem is that this explanation of winter has nothing to do with the seasons, because none of the details of the story has anything to do with seasons, so they are easy to vary. Today we explain seasons by the tilt of the Earth towards the sun. This is a good explanation because it is hard to vary. The degree at which the sunlight hits the Earth causes it to heat in the summer. This works on any object, anywhere, with any light source. You cannot change this explanation, without destroying many other explanations to other, linked phenomenon.

If someone tells you that real estate prices will keep getting higher, and they can’t give you a hard to vary explanation, they are really telling you a wizard did it. Look back onto the news reports from the last year. A whole lot of wizardry was going around during this recession.

Like Richard Feynman, be wary of bad explanations (and economists).

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  • I interpret Feynman differently.

    I don’t think he’s trying to separate the hocus-pocus theories from the generalized, testable ones. I think he’s trying to uncover what “an explanation” is.

    An explanation consists of describing a phenomena as a causality of other, “well-known” phenomena. As per his example – I slipped because I was standing on ice. If I hadn’t the faintest clue about ice being slippery, or would I have been extra-curious, this wouldn’t count for an explanation.

    So, I slipped because I was standing on ice, which is made of water and actually expands when it freezes, thus my pressure caused a small amount of liquid to form on top which caused considerably less friction. And so forth.

    When asked about magnets, Feynman explains that there is no analogy or retraction to be used, since the magnetic force is one of the building blocks of physics. It’s an axiom. Everything in the world is explained by using magnetism; So magnetism couldn’t be explained using anything else.

  • Think of each time Feynman asks “Why?”, or each answer, as another turtle. There are turtles all the way down. Magnetism happens to be the bottom turtle (one of a few), on which the world stands. It’s almost useless asking why the world is standing on this particular turtle.
    I agree with your interpretation of Feynman answer. He is willing to explain things as they are, and refuses to use bad analogies. The turtle cannot be like an elephant, even if you know what an elephant looks like and never saw a turtle.
    And now comes the creationist and says the same. At least we have some proof about our turtles, as they provide good explanations for how the world works. Creationists can only say they’ve read it in a book somewhere.

  • I see now.

    So to clearly reiterate the concept of the post, it is that any theory, scientific or other, requires a set of axioms to stand upon.

    Those of the scientific nature tend to be well-defined, cover all cases, and small in number (which is the flip-side of your “easy to vary”).

    On a side note,
    I think this also explains the confusion of quantum mechanics. It seemed as if they’re adding a gross “exception” to an otherwise perfectly ordered system.

  • As always, you state things better than I can.

    On a side note,
    I should stop writing posts after midnight. Posts are like Gremlins.