Dark Matter Candidates

Given the state of the state at this particular moment of our pre-dark matter/energy epoch this xkcd cartoon while humorous also pretty well encapsulates our present understanding as well as anything else presently under consideration! 

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In the Beginning...

What was going on at the beginning of time? The beginning of the universe? Can we even know what  that situation might have been? As physics finds reductionist answers to the questions of how the universe works, this is the last great unanswered question.

Sean Carroll has a presentation addressing this issue.

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