What is most of the universe made of? Scientists believe it may constitute about 80 percent of the universe but no one has directly observed dark matter. So what is it?
First, while we can't see it, we can measure it's gravitational effects. That's why scientists believe it exists. They're currently studying whether it's comprised of new kinds of elementary particles that have not yet been discovered, in other words, not protons, neutrons and electrons but something else that doesn't interact with light.
“We can measure its effects but not dark matter itself.”