Explore Alliance Presents: How Do You KNOW? – Episode #28: 'Dark Matter Part 1'

The universe has always been mysterious and strange to us, but in fact it may be stranger than we can ever fathom.

In this episode of How Do You KNOW? Dr. Barth will guide us through Henrietta Swan Leavitt's discovery of the period–luminosity relationship for Cepheids, now known as "Leavitt's law", made the stars the first "standard candle" in astronomy, allowing astronomers like Edwin Hubble to make the determination that the Andromeda Nebula was indeed another galaxy. He then picks up on Georges Lemaître's application of Albert Einstein's theory of general relativity to cosmology leading to his "primeval atom" hypothesis. But wait there is so much more...

The activities and materials provided free for the How Do You Know? program are based upon Dr. Barth’s award-winning book: Astronomy For Educators. This book is used as a resource in more than 5,700 schools across the United States and in more than 50 countries world wide. The book is published as an Open Educational Resource Text by the University of Arkansas Library Press.