matter. >> a pretty big deal for scientists in many ways because they've been relying on dark matter existing to explain kind of a missing quarter over the universe that doesn't work out under their math. galaxies spin so quickly they need to be heavier otherwise they'd fall apart. they keep measuring galaxies more precisely. in many ways if dark matter didn't exist, scientists would have to invent it for themselves otherwise einstein's theory of relativity wouldn't make sense. the key thing for them as they learn more about what the universe is made of, they can begin to get into greater detail about how it will proceed in the future, michael. >> so it's like a glue. why do they call it dark matter? >> well, because we don't have a name for it. they've never seen it. they don't know what it exists of. it's perhaps exists from positrons similar to electrons you see in every atom, one said we call it dark matter, we don't know what it is and if it didn't exist, we would have to invent