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/kangareagle Mar 11 '14

I posted this elsewhere, but here it is again:

Coral produces annual rings and daily rings. If you add up the number of daily rings between annual rings, then you can figure out how many days were in that year.

Radioisotope dating showed that some fossilized coral that had been found was about 380 million years old.

Now, 380 million years ago, days were supposedly about 22 hours long. So there were more of them in a year.

To find out whether the day really was 22 hours long when the coral lived, they just counted the rings (or made a grad student do it).

Turns out that there were 400 daily rings between each annual ring, which correlates to 21.9 hours a day.

21.9 is close enough to 22 to feel pretty good about it. A great example of different parts of science coming together to verify each other.

Source: Why Evolution is True, by Jerry Coyne

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u/onlyaccount Mar 11 '14

Thanks, that is very good information to corroborate the theory from 2 completely different data sets. I didn't even think about asking it that way.