Curious about how the world works?

Today You Should Know is a free weekly email newsletter designed to help you (and me) learn something new every Friday.

I tackle interesting questions that have popped into my head (or sent in by readers). The answers are always easy to understand, never boring, and sometimes include my own silly diagrams to get the point across.

Here’s what Today You Should Know nerds have to say about the newsletter:

Check out past editions of the newsletter:

• How are sloths not extinct yet from natural selection?

• What do our recyclables become?

• Why can't robots check the "I'm not a robot" checkbox?

• Why doesn't the United States use the metric system?

• How do court reporters type so fast?

• What causes the screeching sound in subways?

• What is quantum entanglement?

• How is non-alcoholic beer made?

• And many more…