Key section being: >> Excluding planetary engineering, by the time the two galaxies collide, the surface of the Earth will have already become far too hot for

Key section being: >> Excluding planetary engineering, by the time the two galaxies collide, the surface of the Earth will have already become far too hot for liquid water to exist, ending all terrestrial life; that is currently estimated to occur in about 0.5 to 1.5 billion years due to gradually increasing luminosity of the Sun; by the time of the collision, the Sun's luminosity will have risen by 35-40%, likely initiating a runaway greenhouse effect on the planet by this time.