Feature

In the dark

What is the universe made of?

By Alexandra Witze

- More than 2 years ago

In ancient times, listing the ingredients of the universe was simple: earth, air, fire and water. Today, scientists know that naming all of that, plus everything else familiar in everyday life, leaves out 95 percent of the cosmos’s contents.

Without an as-yet-unidentified material called dark matter, clusters of galaxies wouldn’t hold together. Nicolle Rager Fuller
Caption (photo, p25): In this false-color image of galaxies colliding, the majority of the mass (blue) is separate from most normal matter (pink), direct evidence of dark matter.