More Filamentary Science

"Dark matter" is so called because it doesn't reflect or emit radiation -- that is, if it exists, which has been kind of hard to prove because "radiation" includes light, and visual sense organs that use reflected light as their method of perception have a hard time seeing such material.

It's predicted in several theories about how the universe is put together. Astronomers and cosmologists know that the universe has been expanding since the initial singularity usually called the Big Bang. By looking at stars and seeing how much their light wavelengths have shifted, they can see how fast something is moving away from us, and thus what that rate of expansion is.

The problem has been that the expansion speed isn't what it should be based on the amount of matter that the universe is estimated to maintain. The gravity of all the objects in the universe affects the speed of expansion, but there's too little matter to slow it down to the rate that's been measured.

Enter dark matter, which if it exists could account for the slower-than-predicted speed of expansion. But it's only been theorized until now, with the possibility that it might be detected through what's called "gravitational lensing." This is when there's a concentration of matter between a source of light, like a star or a galaxy, and the Earth. The mass of that concentration affects the light via gravity, bending it. Scientists measure the degree of bending and determine the size of whatever's in the way.

A researcher at the University of Michigan found exactly that effect when studying two distant star clusters. He knew that they had some of the super filaments of gas connecting them, but the light bending was more than the gravity of the filaments would suggest. The most likely candidate: Dark matter.

Although it can't be seen or otherwise directly detected, some of the models of how the universe works suggest that as much as 80 percent of the universe's entire mass is dark matter. Rumors that the possibility of having 80 percent of your mass visually undetectable has piqued serious interest in Hollywood are as yet unfounded.