From the February 2009 issue

The curious matter of the missing matter

Scientists still can't account for about 40 percent of the stuff of stars, planets, and people.
By | Published: February 23, 2009 | Last updated on May 18, 2023
Some 23.3 percent of the cosmos exists in the form of dark matter, while 72.1 percent — according to the latest and most precise measure — is dark energy. The nature of dark matter and dark energy remains a mystery. But surprisingly, so does much of the universe’s normal, or “baryonic,” matter — the stuff, like you and me, made of protons and neutrons.