Lecture 16: Page 4, Cosmology Part II

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Evidence for an Accelerated Expansion

Type I Supernova can be used to determine distances to galaxies billions of light years away. Click HERE for a movie. Recently, astronomers have used Type I SN in extremely distant galaxies to obtain distances. This is been compared to the distance obtained from Hubble's Law (redshift) below:

As we look back, the Type I SN are dimmer (farther away) than their Doppler shift would predict for a FLAT UNIVERSE. Why? The Universe is moving apart FASTER NOW than it was then. That is to say: the UNIVERSE is SPEEDING UP. This was totally UNEXPECTED!!

Einstein predicted there was a repulsive force in the universe to keep the universe from collapsing. Later we discovered the Big Bang, and Einstein always considered this cosmological constant to be a major blunder. But in a way, he was correct!