The finding suggests that these galaxies … are very likely enveloped by something very massive.” So reflected Jin Koda, astronomy professor at Stony Brook University, on the discovery this June of more than 800 dark galaxies in the (appropriately named) Coma Cluster. Many are located in a part of the cluster subject to tidal forces that should destroy them, if they were made entirely of visible matter.

So something else—not visible—must be bulking up their mass and protecting them.

While the cosmological version is the most famous, it is far from the only dark matter story in science. There are silent neurons, missing fossils, and nighttime animal migration; death and conception; algorithms both genetic and man-made. Seeing, it turns out, isn’t the only path to believing.

Welcome to “Dark Matter.”