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Cosmology 101: Dark Energy

In the third installment of our Cosmology 101 video series, Astronomy magazine Associate Editor Liz Kruesi focuses on dark energy.
Welcome back to Cosmology 101. In this series I give you an overview of important ideas in the area of cosmology. This video is the third in the series, and focuses on dark energy.

Astronomers determined in 1929 that the universe is expanding. This was one of the most important findings in science. In 1998, two separate groups of astrophysicists discovered that the universe's expansion is speeding up: So, something is accelerating the universe's expansion. Astronomers termed this something "dark energy," but they have no idea what it actually is.

So how did scientists discover dark energy? And what (if anything) do they know about it? These findings rely on observational tools called "standard candles."

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