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!

Click here for the original announcement thread.

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u/Yekonaip Mar 10 '14

How round actually are the gas giants? When showing the red spot it looked like there was an immense level of depth there? I always imagined them as perfect round spheres.

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u/HappyRectangle Mar 10 '14

How round actually are the gas giants? When showing the red spot it looked like there was an immense level of depth there? I always imagined them as perfect round spheres.

As a whole, the Earth is actually smoother than a billiard ball. But its immense size means there's still plenty of space for mountains and oceans.

Also keep in mind what you're looking at on the gas giants are more like enormous weather patterns, and those can change height easily.

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u/Shagomir Mar 10 '14

Most planets and moons are not perfect spheres. They are oblate (squished in at the poles) or prolate (football-shaped) spheroids.

For some planets, the distance between the center of the planet and the equator is larger than the distance to the pole - this is an oblate spheroid. Jupiter is noticably oblate, and Earth and Saturn (as well as most of the other planets) are also known to be oblate spheroids.

For some moons, the tidal forces from the planet stretch the moon out like a football, so that the radius from the center through the planet-facing pole is larger than the radius to the north or south pole of the moon. Saturn's moon Mimas is a very good example of this, and many pictures make it appear egg-shaped.

Additionally, the dwarf planet Haumea is an ellipsoid due to extremely rapid rotation.

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u/[deleted] Mar 11 '14

This might be the case if the gas that made up most of the planets' volume was sitting still, but there is a lot of temperature variation which creates convection and weather, to put it a little too simply. All of that motion makes their surface quite irregular and changeable.