Where Does The Sun Get Its Energy?

The sun has been producing light for about five billion years but where does all its energy come from? The most common idea is that the sun is burning gas - like a giant fireball in the sky....

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it's another beautiful day in SydneyI'm out enjoying the Sun and looking to find out if anyone knowsWhy the Sun shines?So the sun gives us a lot of ... ? - Heat? Sunshine?Provides energy (yes) heat energyWhere is the sun get that energy from?I have no ideaSome kind of chemical reaction...Mmmmmmmm...yeah gas explosionsDoes it burn gas?- It burns gases? - It's burning air - FireThe fire that's on the sunBut is the Sun really a giant ball of fireI mean wouldn't go out after five billion years?This is one of the things that you just assume you know, but you don't actually knowSo in this bucket I have the components of the SunWell, I have protons and neutronsThere's some electrons but I didn't bring themMost of...