The rest of the universe appears to be made of…

The rest of the universe appears to be made of a mysterious, invisible 1 called dark matter (25 percent) and a force that repels gravity known as dark energy (70 percent). Scientists have not yet 2 dark matter directly. It doesn't interact with baryonic matter and it's completely invisible to light and other forms of electromagnetic radiation, making dark matter impossible to detect with current instruments. But scientists are confident it exists because of the gravitational effects it 3 have on galaxies and galaxy clusters.

The visible universe—including Earth, the sun, other stars, and galaxies—is made of protons, neutrons, and electrons bundled together into atoms. Perhaps one of the most surprising 4 of the 20th century was that this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe… revelation...This lecture will 5.