If you’ve ever spent a night staring at the Moon, you may have noticed something a bit strange. A quick flash. A fairy-like shimmer. Maybe a soft glow that seems to creep across the surface. For centuries, people have described these brief flickers of light, now known as transient lunar phenomena, or TLPs.

The first detailed record came in 1787, when British astronomer William Herschel spotted a glowing patch on the Moon that lingered for hours. He compared it to the brightness of a nebula and couldn’t explain what he was seeing. Centuries later, scientists are still chasing the same question.

Modern observations show that these lights come in many forms. Some are faint and diffuse, while others flare bright enough to be seen from Earth without any sort of magnification. According to Anthony Cook, a physics researcher at Aberystwyth University, roughly 3,000 have been logged through telescopes and cameras. Their duration ranges from milliseconds to hours, and those differences offer clues about what’s happening on the lunar surface.

What Are those Weird Lights Sometimes Seen on the Moon?

The quickest flashes are usually caused by meteoroids striking the Moon. Even a rock small enough to fit in your hand can create a burst of heat and light when it hits. High-speed cameras finally captured these impacts in the 1990s, confirming centuries of speculation. Since then, the European Space Agency’s NELIOTA project has documented nearly 200 more, many during meteor showers. What once seemed random now looks more like a steady rhythm of collisions.

Longer-lasting lights may have other explanations. Studies suggest that radon gas trapped under the surface occasionally bursts free during small moonquakes. As the gas decays, it releases a faint glow that can be seen from Earth. These outbursts often line up with regions rich in radioactive elements, which adds more credibility to the idea.

A few reports describe lights that last for hours. Some researchers believe solar wind might be stirring up lunar dust, lifting charged particles high enough to scatter starlight back toward us. Others think these events could be illusions created by satellites or atmospheric effects on Earth.

For a place that’s been studied from every angle, the Moon still has a habit of making us feel like we really don’t know anything about it at all.