In 1929 Edwin Hubble surprised many people – including Albert Einstein – when he showed that the universe is expanding. Another bombshell came in 1998 when two teams of astronomers proved that cosmic expansion is actually speeding up due to a mysterious property of space called dark energy. This discovery provided the first evidence of what is now the reigning model of the universe: “Lambda-CDM,” which says that the cosmos is approximately 70 percent dark energy, 25 percent dark matter and 5 percent “normal” matter (everything we’ve ever observed).