the poles, allowing abodes for simple life. [ 49 ] [ 50 ] Earth's surface temperature, even at the poles, reaches an average of ~420 K (147 °C, 296 °F). At this point life, now reduced to unicellular colonies in isolated, scattered microenvironments such as high-altitude lakes or subsurface caves, will completely die out. [ 45 ] [ 56 ] [ d ] 3 billion Median point at which the Moon's increasing distance from the Earth lessens its stabilising effect on the Earth's axial tilt . As a consequence, Earth's true polar wander becomes chaotic and extreme. [ 57 ] 3.3 billion 1 percent chance that Mercury 's orbit may become so elongated as to collide with Venus , sending the inner Solar System into chaos and potentially leading to a planetary collision with Earth. [ 58 ] 3.5 billion Surface conditions on Earth are comparable to those on Venus today. [ 59 ] Assuming both survive the Sun's expansion, by this time the Earth and the Moon become tidelocked , with each showing only one face to the other. [ 72 ] [ 73 ] Thereafter, the tidal action of the Sun will extract angular momentum from the system, causing the lunar orbit to decay and the Earth's spin to accelerate. [ 74 ] The cosmic microwave background cools from its current temperature of ~2.7 K to 0.3 K, rendering it essentially undetectable with current technology. [ 76 ] 450 billion Median point by which the ~47 galaxies [