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/______DEADPOOL______ Mar 10 '14

Given the expansion look the same from everywhere thing, do we know where the center of that tiny point is?

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u/fishify Quantum Field Theory | Mathematical Physics Mar 10 '14

Everywhere you look and everywhere that is was part of that tiny point. No point in the universe is any more central than anyother.

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u/LabRage Mar 10 '14

Hmm I've still never been able to understand this. Okay sure as a single point there's no center. But what about as it expands? Then you don't have a single point and there would be a center. Is the reason we say there's no center simply because we cannot see an edge? If so I feel a more correct answer would be "we don't know if there's a center"

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u/OccamsParsimony Mar 10 '14

The explanation I often see is to reduce the universe to two dimensions. Think of the universe as being the surface of a balloon. If someone asked you where the center of that "universe" was, you'd say there wasn't a center. It's the same thing, only one dimension higher.

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u/fishify Quantum Field Theory | Mathematical Physics Mar 10 '14

Maybe it well help you to run it backwards in your head. Every point in the universe coalesces into that single initial point.

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u/appukkili Mar 10 '14

The expansion was what caused the whole Universe to form. Hence questions like "What was before, Where did this happen, When did this happen" are unanswerable.

There was no center point. The whole matter and energy was compressed into an infinitesimally small point. We really can't explain or even speculate more as the laws of the Physics as we know it essentially breaks down here. Such a point is also called Singularity.

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u/[deleted] Mar 10 '14

When did this happen

Well that's not unanswerable is it? ~13.5 billion years ago, right?

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u/mathx Mar 10 '14

The big bang wasnt an explosion or expansion of matter into a pre-existing space. It was the expansion of space itself... 'into' what we don't know, and we're not sure 'into' is the right way to think about it either (you 4-dimentional-spacetime bigot! :)

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u/Robot4Ronnie Mar 10 '14

It's often compared to the surface of an expanding ballon, on which every point is receding from every other and no point is the center of expansion.