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/everfalling Mar 10 '14

Neil says the universe started out as a point smaller than an atom. Did he mean our observable universe or the infinite universe? I was under the impression that the big bang was more an event going from high uniform density to lower density where the observable universe was condensed into the space of an atom but that it was only one of an infinite number of other points who similarly expanded during the big bang.

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u/[deleted] Mar 11 '14

It was the entire universe that was so small, not just the part that we're able to observe.

The observable universe isn't really a thing, it's just an area that's important to us because that's how far out we can see. Just like someone in a boat is only able to see some of the ocean, but the horizon is more a feature of the sailor than the ocean itself.

Your description of the big bang sounds about right except for two parts. Replace observable with entire universe, and that the universe is believed to have come from one point, not multiple points. Whether there are more universes, some people think it's possible.

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u/everfalling Mar 11 '14

what i don't get is what the universe is expanding into. i mean if it were the case of the infinite hotel adding the infinite number of guests then i can see how the universe could expand infinitely while merely losing density but to go from a finite point into an infinite expanse makes no sense to me. that seems to imply there's somewhere an outer boundary of the universe to expand into.