Stargazers in parts of Europe were stunned by an unusual sight on Monday evening: a large, glowing blue spiral in the sky.

On Twitter, the Met Office explained: “This is likely to be caused by the SpaceX Falcon 9 rocket, launched earlier today. The ...

You might think that explaining why the sky is blue would be kind of simple. But even a brief explanation of it requires a lot of science. The colors of everything you see are produced in ...