How do we know how long the Sun has left to live? | 7 things we need to know

You'll often hear people say that the Sun has about 5 billion years left to live before it runs out of fuel. But where does that number come from? It's quite a simple back of the envelope calculation but there are 7 key things we need to know before we can do that... For more on why E=mc2 see this article from Ethan Seigel: https://www.forbes.com/sites/startswi... To find out more on helioseismology and how we "listen to the Sun" check out this lecture:    • How We See Inside a Star With Sound   02:08 - the calculation of the lifetime of the Sun 05:23 - how we know the mass of the Sun 07:54 - how we know the distance between the Earth and the Sun 08:39 - how we measure the brightness of the Sun 09:44 - why E=mc2 11:04 - how we know the Sun is powered by nuclear fusion 13:35 - how we measured the mass difference between 4 Hydrogen atoms and 1 Helium atom 16:58 - how we know the core of the Sun is where nuclear fusion takes place (helioseismology) 19:02 - how we know how old the Solar System (and therefore the Sun) is ----- You can pre-order my book ' Space: 10 Things You Should Know' as a hardback (UK only) or e-book (worldwide): http://bit.ly/SpaceDrBecky ----------- Follow me on Twitter:   / drbecky_   And on Instagram:   / drbecky_s   Don't forget to subscribe and click the little bell icon to be notified when I post a new video! ------ Dr Becky Smethurst is an astrophysicist researching galaxies and supermassive black holes at Christ Church at the University of Oxford. http://drbecky.uk.com