So, how can you safely show the changing sun to a large group of people without having them line up forever to look through a telescope with a solar filter, or having a lot of equipment?

A group of astronomers have a solution: Get a disco ball.

If you set up a disco ball in a sunlit room, they say, it will project tiny images of the sun onto the walls, similar to how a pinhole camera works. But a disco ball can show the state of a solar eclipse or the presence of sunspots, and allow dozens of people to see it simultaneously.

"Commercial disco balls provide a safe, effective and instructive way of observing the sun," a group of astronomers from several universities wrote in a pre-print paper published on arXiv. The paper explores the optics of solar projections with disco balls, and the researchers found that while sunspot observations are challenging, the solar disk and its changes during eclipses are "easy and fun to observe."

They also explore the disco ball's potential for observing the moon and other bright astronomical phenomena.

The astronomers note that simple pinholes have been used to observe the sun since antiquity, along with other commonly used tools for projecting eclipses, such as pinhole projectors, colanders, or tree canopies.