In a few billion years when the sun expands and grows into a red giant, how fast will it expand and “swallow” the inner planets?

Question

In a few billion years when the sun expands and grows into a red giant, how fast will it expand and “swallow” the inner planets?

In: Physics

Answer 1

Short answer: it would take 2.5 billion years (starting from 5.4 billion years up to 7.9 billion years in the future).

There’s a cool timeline of the solar system future in Wikipedia:

https://en.m.wikipedia.org/wiki/Timeline_of_the_far_future