From today’s Boston Globe:

Scientists say they have proof of dark matter

For decades, many scientists have theorized that the universe is made up of nearly undetectable mysterious substances called dark matter and dark energy. But until yesterday there was no proof that the subatomic matter exists.

After studying data from a long-ago collision of two giant galaxies, researchers now say they are certain dark matter exists and plays a central role in creating and defining gravity throughout the universe.

While the scientists are not sure exactly what dark matter is, since they have yet to identify it in a laboratory, they said the workings of the universe cannot be explained without it.

The finding will have potentially great impact on an active debate among physicists and cosmologists about not only dark matter, but the workings of gravity. Indeed, the theory of dark matter evolved largely to explain the finding several decades ago that there was not enough visible matter in the universe to produce and account for the gravity needed to keep galaxies from flying apart.

“A universe that’s dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking,” said Doug Clowe of the University of Arizona in Tucson, leader of the NASA-Harvard University study. “These results are direct proof that dark matter exists.” [full text]