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 View count: 1,898,234 Likes: 27,224 Comments: 1,288 Duration: 11:21 Uploaded: 2015-07-17 Last sync: 2024-05-08 14:15

### Citation

 Citation formatting is not guaranteed to be accurate. MLA Full: "Distances: Crash Course Astronomy #25." YouTube, uploaded by CrashCourse, 17 July 2015, www.youtube.com/watch?v=CWMh61yutjU. MLA Inline: (CrashCourse, 2015) APA Full: CrashCourse. (2015, July 17). Distances: Crash Course Astronomy #25 [Video]. YouTube. https://youtube.com/watch?v=CWMh61yutjU APA Inline: (CrashCourse, 2015) Chicago Full: CrashCourse, "Distances: Crash Course Astronomy #25.", July 17, 2015, YouTube, 11:21, https://youtube.com/watch?v=CWMh61yutjU.
How do astronomers make sense of the vastness of space? How do they study things so far away? Today Phil talks about distances, going back to early astronomy. Ancient Greeks were able to find the size of the Earth and from that the distance to and the sizes of the Moon and Sun. Once the Earth/Sun distance was found, parallax was used to find the distance to nearby stars, and that was bootstrapped using brightness to determine the distances to much farther stars.

Check out the Crash Course Astronomy solar system poster here: http://store.dftba.com/products/crashcourse-astronomy-poster

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Chapters:
Introduction 00:00
How did we calculate the Earth's Size? 1:07
THE Astronomical Unit (AU) = 149,597,870.7 km 3:12
Depth Perception & Parallax 5:39
Light Years & Parsecs 7:31
Brightness Indicates Distance 9:07
Review 10:30
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PHOTOS/VIDEOS
Lunar Ecplise http://www.slate.com/content/dam/slate/blogs/bad_astronomy/2014/04/15/lunareclipse_partial_apr142014_spica.jpg.CROP.original-original.jpg [credit: Phil Plait]
Venus & Mercury [credit: Phil Plait]
Venus Transit https://www.youtube.com/watch?v=34mXua1n_FQ [credit: NASA]
Black Drop Venus Transit https://en.wikipedia.org/wiki/Black_drop_effect#mediaviewer/File:BlackDrop-Venus-Transit.jpg [credit: Wikimedia Commons, H. Raab, Johannes-Kepler-Observatory]
New Horizons Approaching Pluto and Charon https://en.wikipedia.org/wiki/New_Horizons#/media/File:15-011a-NewHorizons-PlutoFlyby-ArtistConcept-14July2015-20150115.jpg [credit: NASA/JHU APL/SwRI/Steve Gribben]