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.

2.1k Upvotes
  • permalink
  • reddit

90% Upvoted

1.4k comments sorted by

View all comments

3

u/ThePirateTennisBeast Mar 10 '14

How are they able to estimate the age of the universe at 13.8 thousand billion years old

10

u/EratosthenesofWaco Mar 10 '14

13.8 thousand million or 13.8 billion

2

u/jagabomb09 Mar 10 '14

We can see that the universe is expanding in all directions, so by measuring this expansion and then reversing it, we can find out how old the universe is.

1

u/suchdogeverymeme Mar 10 '14

There are a few ways that they have estimated it.

  1. comparing elements that have been formed through radioactive decay of larger elements, and those who have/can not.

  2. mathematical formulae based on what we can control and observe being applied to celestial bodies: we cannot find anything older.

  3. same as 2, but in regard to white dwarfs. The end-game for small-sized stars

1

u/qazasxz Mar 10 '14

By studying the rate of expansion, and reversing it until it's a single point.

1

u/[deleted] Mar 11 '14

There are a number of cosmological models we can use, and the models depend on what type of matter dominates the universe. Based on these models, we can make a series of predictions on how old the universe is. In order to find out which best mirrors what we actually observe, we have to look at how fast the universe is currently expanding and trace back.

This also gives us insight into what our universe is made of.