It's known indirectly through its gravitational effects (based on these, scientists think dark matter
outweighs ordinary matter by a factor of at least five).
This and several other lines of evidence point to the existence of a mysterious form of invisible matter that exerts a gravitational influence on other matter and
outweighs ordinary matter by a factor of about 6 to 1.
In fact,
it outweighs ordinary matter by about five to one.
Dark matter's composition is unknown, but it is thought to
outweigh ordinary matter by five to one.
We know of its existence only by its gravitational effect, even though it may
outweigh ordinary matter five to one.
Not exact matches
Dark
matter, the mystery mass that, according to data from the Wilkinson Microwave Anisotropy Probe,
outweighs ordinary atoms by more than five to one: That was Zwicky's.