The sun will last, at its current brightness for 9 billion more years. When light (photon particle) is generated inside the sun, it takes a long time to bounce around inside to later escape and travel. It's consensus that the very similar apparent sizes of the moon and the sun as seen from earth is a coincidence (as already answered.
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Besides the moon, the sun has a tidal component for the earths oceans, and when that crashes into continents the energy absorbed comes from the. How long until the sun gets burned down to the point where it cannot sustain.