This image was on NASA’s website recently:

It’s a real depiction of something happening right now, but apparently there’s no need to resort to Douglas Adams to explain it — or maybe there is:

Have you ever been hit by a beam of high energy particles from above? Surely you have — it happens all of the time. Showers of high energy particles occur when energetic cosmic rays strike the top of the Earth’s atmosphere. Cosmic rays were discovered unexpectedly in 1912. … Although many of the low energy cosmic rays come from our Sun, the origins of the highest energy cosmic rays remain unknown and a topic of much research. This drawing illustrates air showers from very high energy cosmic rays. Cosmic rays may even be important to Earth’s weather — common lightning may be triggered by passing cosmic rays.

If I recall correctly, didn’t the Vogons provide some sort of unintelligible advance warning?