How does dark energy affect the universe's expansion? Measuring past expansion history should tell us the future expansion without ever having to count any galaxies. To measure this we need to measure the redshift-distance relationship, which we will talk about in detail in this episode.

Originally released by Knowledgemotion, 2016. Streaming video file encoded with permission for digital streaming by Infobase on February 21, 2020.

What Does Dark Energy Really Do? (9:50); .