Every bulb at once?

About this video

Nur wakes up at night and her bedroom light won't come on. She looks out: the street lights are off, and so are all the lights in the houses opposite. Two explanations fit what she sees. One: there is a power cut in the area. Two: every light bulb in the street broke at the same moment. Which should she believe?

Count what each one needs. The power cut needs one thing to have happened: the electricity stopped coming to the street. The broken bulbs need hundreds: every bulb in every house and every street light, each one breaking, all at the same moment, by chance. The things an explanation needs to be true, which we haven't checked, are its assumptions. When two explanations fit the facts equally well, start with the one that needs fewer assumptions, the simplest explanation. The rule of thumb is called Occam's razor, after William of Ockham, an English thinker of the 1300s: a razor cuts away the extra assumptions that aren't needed.

The simplest explanation isn't always true; sometimes the world really is complicated. The razor tells you which explanation to try first, not which one is right. Then you test it, as always. If it's a power cut, the fridge will be off too, and the electricity company may have a message about it. If the fridge is humming, Nur needs another explanation. The razor is where finding out starts; the test is where it ends. This video goes with The Simplest Explanation lesson of Science Level 1 on Knaph.

Transcript

1. 0:00Nur's light won't come on. Nor will the street's, or any house's.
2. 0:05A power cut? Or every bulb in the street broke at the same moment?
3. 0:11A power cut needs one thing to happen. The bulbs need hundreds, all at once.
4. 0:17Start with the one that needs fewer things to be true. Occam's razor.
5. 0:23Then test it. If the fridge is off too, it's a power cut.
6. 0:29The simplest explanation is where to start, not a proof.