While scientific predictions of the future can never be absolutely certain, present understanding in various fields allows for the prediction of far future events, if only in the broadest strokes. These fields include astrophysics, which has revealed how planetsand stars form, interact, and die; particle physics, which has revealed how matter behaves at the smallest scales; evolutionary biology, which predicts how life will evolve over time; and plate tectonics, which shows how continents shift over millennia.
All projections of the future of the Earth, the Solar System, and the Universe must account for the second law of thermodynamics, which states that entropy, or a loss of the energy available to do work, must increase over time. Stars eventually must exhaust their supply of hydrogen fuel and burn out. Close encounters gravitationally fling planets from their star systems, and star systems from galaxies.
Eventually, matter itself is expected to come under the influence of radioactive decay, as even the most stable materials break apart into subatomic particles. Current data suggest that the universe has a flat geometry (or very close to flat), and thus, will not collapse in on itself after a finite time, and the infinite future potentially allows for the occurrence of a number of massively improbable events, such as the formation of a Boltzmann brain.
The timelines displayed here cover events from roughly eight thousand years from now[a] to the furthest reaches of future time. A number of alternate future events are listed to account for questions still unresolved, such as whether humans will become extinct, whether protons decay, or whether Earth will survive the Sun's expansion into a red giant.