WHAT DO YOU KNOW ABOUT DARK ENERGY?
DARK ENERGY 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 discoveries of the 20th century was that this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe. The rest of the universe appears to be made of a mysterious, invisible substance called dark matter (25 percent) and a force that repels gravity known as dark energy (70 percent). Dark energy is the name given to the mysterious force that's causing the rate of expansion of our universe to accelerate over time, rather than to slow down. That's contrary to what one might expect from a universe that began in the Big Bang. Astronomers in the 20th century learned the universe is expanding. In physical cosmology and astronomy , dark energy is an unknown form of energy that affects th
