Dark Matter Decoder Ring...

Stars in the outer regions of spiral galaxy M74 move much more quickly than expected if they were held in orbit only by the visible matter. The best explanation is that they are being pulled by a large halo of unseen, dark matter. (Credit: Gemini Observatory/GMOS Team)

Five-sixths of the universe is missing. That statement feels strange to write, and I’m sure it feels pretty strange to read as well. Given the vastness of the cosmos–and given how little of it humans have explored–how can we know for sure that anything is out of place? The claim sounds positively arrogant, if not delusional.

And yet scientists have assembled a nearly airtight case that the majority of the matter in the universe consists dark matter, a substance which is both intrinsically invisible and fundamentally different in composition than the familiar atoms that make up stars and planets. In the face of staggering difficulties, researchers like Samuel Ting of MIT are even making progress in figuring out what dark matter is, as evidence by teasing headlines from last week. Time to come to terms, then, with the new reality about our place in the universe. Here are seven key things every informed citizen of the cosmos should know.

1. Dark matter is real.
2. Dark matter can be visible...sometimes.
3. Dark matter might show up here on Earth.
4. We might be able to create our own dark matter.
5. Dark matter is a totally different thing from dark energy.
6. The dark stuff really dominates.
7. The dark universe might have a life of its own.

Discovery Out There: Your 7-Step Guide to the Shadow Universe, Cory S. Powell