When will the world really end?

Billions of years from now, life on Earth will be extinguished when the dying sun scorches the surface of our planet. New research has aimed to determine what the last life forms on Earth will be, and what kind of abodes they will cling to before the Earth becomes sterilized.

We are fortunate that our planet orbits a star that has a long main-sequence lifetime. However, the sun’s luminosity is gradually increasing, and in about one billion years the effects of this will start to be felt on Earth.

Surface temperatures will start to creep relentlessly upwards over the next few billion years, which will increase the amount of water vapor in the air. This will act to further increase temperatures and will thus signify the beginning of the end for life on Earth.

The rising temperatures will cause excessive amounts of rain and wind, and thus increase the weathering of silicate rocks, which will suck extra carbon from the atmosphere.

Ordinarily, the carbon is replaced via plate tectonics in the carbon-silicate cycle as it is released in volcanic gases. However, the oceans will start to evaporate as the temperatures continue to rise, which will probably put a stop to plate tectonics as scientists believe that water is an essential lubricant for the motion of tectonic plates on Earth. This will deplete the number of active volcanoes, and the carbon will not be replenished in the atmosphere.

The lack of carbon dioxide will effectively choke plant life on Earth, since plants require atmospheric CO2 for their respiration. The death of oxygen-producing plants will in turn lead to less oxygen in the atmosphere over a few million years. This will spell disaster for the remaining animal life on Earth, with mammals and birds being the first to become extinct. Fish, amphibians and reptiles would survive a little longer, as they need less oxygen and have a greater tolerance to heat.

The last type of animal present on the far-future Earth would likely be invertebrates. Once the insects finally succumb to the increasing temperatures, the Earth will once again be solely populated by microbial life, just as it had been for the first few billion years of our planet’s history. The last lingering life will desperately seek out niches of the planet that are still habitable, but even extremophile forms of life will find this to be a challenge.

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