More than 100 years ago, Albert Einstein applied his general theory of relativity to the universe as a whole. According to ScienceDaily, he found that his equations did not describe a universe that stayed static forever, but one that would expand or contract.
That result ran against the common belief at the time that the universe was unchanging. To make his model fit that view, Einstein added a cosmological constant, or lambda, which could counterbalance gravity and keep the universe stable.
Einstein later dropped the idea, and he reportedly referred to it as his “greatest blunder.” But after Edwin Hubble found evidence that the universe is expanding, the equations Einstein had worked with helped lay groundwork for later cosmology, including ideas that supported the Big Bang theory.
Then in 1998, astronomers found that the universe’s expansion was not slowing down — it was speeding up. ScienceDaily reports that the simplest explanation was again Einstein’s cosmological constant, now associated with dark energy. That discovery led to the current best-known model of the universe, called LCDM cosmology, which combines lambda with cold dark matter.
