Dr. Al Grauer hosts. Dr. Albert D. Grauer ( @Nmcanopus ) is an observational asteroid hunting astronomer. Dr. Grauer retired from the University of Arkansas at Little Rock in 2006. travelersinthenight.org

Today's 2 topics:

- Being night sky friendly means that you only use outdoor lighting fixtures which direct light onto the ground where humans need it.

- In 1933 Fritz Zwicky suggested that the high speeds of galaxies in the relatively distant Coma Cluster are indicative of some type of invisible material which is pulling on them.  

 

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