In part 4, the planet Earth is beginning to experience some of the worst tectonic events in millions of years. In today’s entry, the planets plight continues to worsen, until it reaches a point of absolute no return…
1.4 million A.D.: The star Gliese 710 passes as close as 1.1 light years to the Sun before moving away. This may gravitationally perturb members of the Oort Cloud — a halo of icy bodies orbiting at the edge of the Solar System — thereafter increasing the likelihood of a cometary impact in the inner Solar System.
2 million A.D.: Pioneer 10 passes near the bright star Aldebaran.
4 million A.D.: Pioneer 11 passes near one of the stars in the constellation Aquila.
8 million A.D.: The Martian moon Phobos comes within the Roche limit, at which point tidal forces will disintegrate the moon and turn it into a ring of orbiting debris that will continue to spiral in toward Mars. Also, the LAGEOS satellites’ orbits will decay and reenter Earth’s atmosphere, carrying with them a message to any far future descendants of humanity, and a map of the continents as they are expected to appear then.
10 million A.D.: The East African Rift valley is flooded by the Red Sea, causing a new ocean basin to divide the continent of Africa.
11 million A.D.: The ring around the Mars — the remains of the moon Phobos — hits the surface of the planet.
50 million A.D.: The Californian coast begins to be subducted into the Aleutian Trench due to its northward movement along the San Andreas Fault. Africa’s collision with Eurasia closes the Mediterranean Basin, creating a mountain range similar to the Himalayas. Also around this time, if not achieved previously, the entire Milky Way galaxy could be colonized, even at sub-light speeds.
100 million A.D.: Earth will have likely been impacted by a meteorite comparable in size to the one that triggered the Cretaceous-Paleogene (K-Pg) extinction event 65 million years ago.
225 million A.D.: The Sun completes it’s current rotation around the galactic center.
230 million A.D.: Beyond this time, the orbits of the planets become impossible to predict.
250 million A.D.: All of the continents on Earth are becoming a supercontinent, the first such event since Pangea broke up 450 million years beforehand. Possible names for the new supercontinent could be Amasia, Pangea Ultima, Pangea Proxima, or Neopangea.
500-600 million A.D.: Estimated time before a gamma ray burst, or massive, hyperenergetic supernova, occurs within 6,500 light-years of Earth; close enough for it’s rays to affect Earth’s ozone layer and trigger a mass extinction, assuming the hypothesis is correct that a previous such explosion triggered the Ordovician-Silurian extinction event. However, the supernova would have to be precisely oriented relative to Earth to have any negative effect.
600 million A.D.: Tidal acceleration move the Moon far enough from Earth that total solar eclipses are no longer possible. Also at this time, the Sun’s increasing luminosity begins to the disrupt the carbonate-silicate cycle; higher luminosity increases weathering of surface rocks, which traps carbon dioxide in the ground as carbonate. As water evaporates from the Earth’s surface, rocks harden, causing plate tectonics to slow and eventually stop. Without volcanoes to recycle carbon back into the Earth’s atmosphere, carbon dioxide levels begin to fall. By this time, they will fall to the point where C3 photosynthesis is no longer possible. All plants that utilize C3 photosynthesis, about 99% of all present-day plants, will die.
800 million A.D.: Carbon dioxide levels fall to a point where C4 photosynthesis is no longer possible. Multi-cellular life dies out.
1 billion A.D.: The Earth has become too hot to support life, since the sun has grown in size. The average temperature on Earth has reached 320 Kelvins (47 degrees Celsius/116.6 degrees Fahrenheit). The oceans evaporate. Pockets of water may still be present at the poles, allowing abodes for simple life.
1.3 billion A.D.: Eukaryotic life dies out due to carbon dioxide starvation. Only prokaryotes exist.
1.5-1.6 billion A.D.: The Sun’s increasing luminosity causes it’s circumstellar habitable zone to move outwards; as carbon dioxide increases in Mars’ atmosphere, it’s surface levels rise akin to Earth during the Ice Age.
2.3 billion A.D.: The Earth’s outer core freezes, if the inner core continues to grow at it’s current rate of 1 mm per year. Without the liquid outer core, Earth’s magnetic field shuts down.
2.8 billion A.D.: Earth’s surface temperature, even at the poles, reaches an average of 420 Kelvins (147 degrees Celsius/196.6 degrees Fahrenheit). At this point, life, now reduced to unicellular colonies in isolated, scattered microenvironments such as high-altitude lakes and subsurface caves, will completely die out.
3 billion A.D.: Median point at which the Moon’s increasing distance from Earth lessens it’s stabilizing effect on the Earth’s axial tilt. As a consequence, Earth’s true polar wander becomes chaotic and extreme.
3.3 billion A.D.: There is a one-percent chance that Mercury’s orbit could become so elongated as to collide with Venus. The collision would cause chaos in the inner Solar System, and potentially lead to a planetary collision with Earth.
3.5 billion A.D.: Surface temperatures on Earth are comparable to present-day Venus.
3.6 billion A.D.: The Neptunian moon, Triton, falls through the Roche limit and disintegrates into a planetary ring system comparable to the one around present-day Saturn.
4 billion A.D.: The Milky Way and Andromeda galaxies collide and begin to merge, forming the Milkomeda Galaxy.
5.4 billion A.D.: The Sun has become a red giant.
7.5 billion A.D.: Earth and Mars may become tidally locked with the expanding Sun.
7.9 billion A.D.: The Sun reaches the tip of the red giant branch, swelling to it’s maximum radius of 256 times it’s present-day value. As a result, Mercury, Venus, and possibly the Earth, have been consumed and destroyed. During this time, it’s possible that Saturn’s moon Titan could achieve surface temperatures necessary to support life.
8 billion A.D.: The Sun becomes a carbon-oxygen white dwarf with about 54.05 percent of its present mass.