Scientists looked at the rate of expansion of the universe to find out how quickly it is slowing down. The reason they thought it was slowing down is because there's all this stuff in the universe. Scientists have no idea what dark energy is, which is separate from dark matter.
In the early 1900s, Henrietta Leavitt made one of the most important discoveries in the history of astronomy: a yardstick to measure distances to faraway stars. Using this tool, scientists eventually transformed our understanding of the universe. They realized space was expanding, that this expansion was accelerating, and that ultimately, everything will end.
This episode originally ran on June 30, 2021.
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