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Physics Girl

Is energy always conserved?

Season 1 Episode 19 | 5m 16s

When light passes through the universe and is redshifted by the expansion of space itself, how is energy conserved? The stretched light has a longer wavelength and therefore a lower energy. Is energy conserved? If so, where does it go?

Aired: 08/07/16

Rating: NR

Video has closed captioning.

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