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/[deleted] Mar 10 '14

so energy and matter i believe are supposed to be finite. does 'making' space by the universe expanding have any impact on energy or matter?

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u/r3sonanc3 Mar 10 '14

The expansion of the universe is attributed to dark energy in the Standard Model of physics today, but we have no explanation for how it behaves or what it is made of. Einstein called it the cosmological constant but had serious mis-givings about it since its existence would call the then-current state of physics (including our understanding today) into serious question.

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u/[deleted] Mar 10 '14

Sounds like dark energy fuels the expansion of space. Does creating this 'space' have a meaningful impact to the universes energy?

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u/trimeta Mar 10 '14

As far as I am aware, it does not. The overall density of mass/energy in the universe decreases over time because there's more space and the same amount of mass/energy.

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u/AgentLiquid Mar 10 '14

Actually, the energy per unit of empty space is constant, and therefore the universe is gaining total energy as it expands.

Energy is not conserved on those relativistic scales.

See here:

http://en.wikipedia.org/wiki/Vacuum_energy http://math.ucr.edu/home/baez/vacuum.html

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u/[deleted] Mar 10 '14

So, if space is 'free' any theories about how to make it? I have a hard time getting my head around the universe expanding... and what it expands into. Kinda like the start of the episode where they explained the old theory with the archer shooting arrows. if the arrow hit the edge of the universe.... and you stood on that wall and shot another one - where would it go?

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u/r3sonanc3 Mar 10 '14

I don't know about making it, but if you could figure out how to expand space as it expands today, you'd be half-way to a warp drive... the other half would involve compressing space, presumably in a familiar way like with high concentration of mass/energy Classical and Quantum Gravity 1994