Moon’s Supersonic Shadow Created Waves During the Solar Eclipse

By Laura Geggel

When the moon’s shadow zipped across the United States during the Great American Solar Eclipse this past August, the shadow traveled so fast it created waves in Earth’s upper atmosphere, a new study finds.

During a solar eclipse, the moon passes between the sun and Earth, casting its shadow in a narrow path across parts of the planet. Since the 1970s, researchers have suspected that the moon’s shadow, which travels at supersonic speeds during a solar eclipse, could create waves in the ionosphere— a part of Earth’s upper atmosphere that has electronically charged particles.

But they hadn’t been able to prove it until now, the researchers told Live Science.

Bow waves

Researchers suspected that the moon’s shadow could “make waves” because when the moon travels between the sun and Earth, its shadow blocks the sun’s energy, rapidly cooling the area beneath it. But because the shadow moves so quickly, anything in its wake is swiftly reheated. This sudden temperature change was thought to generate waves in “the atmosphere at altitudes where the ozone layer and water vapor efficiently convert solar [ultraviolet] radiation to heat,” the researchers wrote in the study.

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