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April 20, 2020 - The Great Debate

The Great Debate  The “Great Debate” about the size of the universe took place 100 years ago this week. Lick Observatory’s Heber Curtis argued that the universe is composed of many “spiral nebulae” (galaxies) like our own. Mount Wilson Observatory’s Harlow Shapley contended that spiral nebulae were nearby gas clouds, and there was only one galaxy in our universe. Curtis put the Sun near the center of our small galaxy, but Shapley placed it far from the center of a large universe/galaxy.  Shapley turned out to be more correct regarding the size of the universe, although he grossly underestimated its size, and Curtis was right about our galaxy being just one of many in the universe. In this Hubble image, light from galaxies billions of light-years away is distorted by the gravity of a cluster of closer galaxies.

Image credit: Credit: ESA, NASA, J.-P. Kneib (Caltech and Observatoire Midi-Pyrénées) and R. Ellis

Weekly Calendar

April 20 - 26, 2020

Holidays - Sky Events - Space History


Monday 20

Moon at apogee

1972: Apollo 16 lands on Moon

Tuesday 21

Lyrid meteor shower

1997: Cremated remains of 24 people launched into orbit aboard Pegasus rocket in first space funeral

Wednesday 22

New Moon 10:26 PM ET
Lyrid meteor shower

2010: X-37B spacecraft launched

Thursday 23

1858: Max Planck born
1962: Ranger 4 launched
1963: M2-F1 lifting body first free flight
1996: Priroda module launched to Mir space station

Friday 24

1970: China becomes fifth nation to launch its own satellite
1990: STS-31 Discovery launched

Saturday 25

1962: Second Block I Saturn C-1 (SA-2) launched
1990: Hubble Space Telescope deployed
2003: ISS Expedition Seven crew launched on Soyuz TMA-2

Moon phase Sunday 26

Uranus in conjunction with Sun
Vesta 0.1° south of Moon
Venus 6° north of Moon

1920: Shapley-Curtis debate on the nature and distance of spiral nebulae
1993: STS-55 Columbia launched

Suggestions for new history dates or better links? Corrections for errors on this page? Please e-mail me.