Something fascinating happened during the Great American Eclipse in August of 2017 in the Earth’s upper atmosphere, and scientists have only just now recognized this bizarre phenomenon. They discovered that the eclipse actually left a “wake” in the atmosphere as if it were a ship moving through an ocean.

It’s the first time scientists have ever detected such a thing, although it has been theorized before. Researchers at the Massachusetts Institute of Technology and the University of Tromso in Norway detected the waves in the ionosphere.

By passing in front of the sun, the moon blocks heat from reaching the Earth, and as the moon moves out of the way, it creates a bow wave effect that acts as a ripple through the atmosphere. A huge network of Global Navigation Satellite System receivers enabled scientists to detect this phenomenon for the very first time.

“We were looking at some phenomena that were expected but never had the chance to be observed,” study author Shun-Rong Zhang from the MIT Haystack Observatory told Gizmodo. “That was the surprise we found… we had a large coverage and our system is sensitive enough to be able to see these smaller variations. That was really very interesting to us.”