[justforfunhere]

>> the sun will enter the final phase of its life. Its core of hydrogen fusion will expand and, in doing so, inflate the outer atmosphere of the star into gross proportions. It will swell and become a red giant star that will engulf Mercury and Venus and incinerate Earth.

Does anybody know what is the timescale we are talking about here? From start of inflation of Sun's outer atmosphere to engulfing of earth?