The Earth is currently undergoing a brief epoch in which water is liquid on the surface and therefore able to sustain life. This places the Earth in what’s referred to as the 'habitable zone.' As the sun loses mass and slowly expands, the oceans will evaporate and the Earth will once again return to a lifeless superheated rock. As the Earth leaves the Sun's habitable zone, other planets may enter into it, creating new islands of potential life. The timer counts down the best-case scenario estimates for the habitability of Earth, in seconds (not factoring in man-made events, which subtract from the already finite time).