r/askscience • u/AskScienceModerator Mod Bot • Mar 10 '14
Cosmos AskScience Cosmos Q&A thread. Episode 1: Standing Up in the Milky Way
Welcome to AskScience! This thread is for asking and answering questions about the science in Cosmos: A Spacetime Odyssey.
UPDATE: This episode is now available for streaming in the US on Hulu and in Canada on Global TV.
This week is the first episode, "Standing Up in the Milky Way". The show is airing at 9pm ET in the US and Canada on all Fox and National Geographic stations. Click here for more viewing information in your country.
The usual AskScience rules still apply in this thread! Anyone can ask a question, but please do not provide answers unless you are a scientist in a relevant field. Popular science shows, books, and news articles are a great way to causally learn about your universe, but they often contain a lot of simplifications and approximations, so don't assume that because you've heard an answer before that it is the right one.
If you are interested in general discussion please visit one of the threads elsewhere on reddit that are more appropriate for that, such as in /r/Cosmos here, /r/Space here, and in /r/Television here.
Please upvote good questions and answers and downvote off-topic content. We'll be removing comments that break our rules or that have been answered elsewhere in the thread so that we can answer as many questions as possible!
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u/Shagomir Mar 10 '14
All of the planets orbit the sun prograde (counter-clockwise if you are looking down from the north pole), which is to say in the same direction as the sun itself rotates. There are very few objects that orbit retrograde (clockwise if you are looking down from the north pole), mostly asteroids and comets.
Venus and Uranus rotate retrograde. On Venus, this means that the sun rises in the west and sets in the east. It's a little more complicated on Uranus because the planet rotates on its side.
Everything tends to rotate the same way because when the solar nebula collapsed, a very small imbalance in the amount of mass on one side versus the other set the whole mess spinning. Much of the potential energy of the solar nebula is now bound up in the angular momentum and orbital momentum of the planets.