In a new study conducted at the University of East Anglia in the United Kingdom, researchers have estimated that the earth will be able to support life for another 1.75 to 3.25 billion years, unless there's a nuclear holocaust, a planet-killing asteroid event, or some other errant catastrophe in the interim.
What will inevitably do earth in are astronomical forces that will push the planet out of its habitable zone, and into the hot zone. These zones are defined by the state of a planet's water. Liquid water exists on earth, as it's just the right distance from the sun to prevent it all from freezing or evaporating. Over billions of years, the earth will slowly enter the hot zone, which has prompted researchers to take a look at other planets in our solar system.
The study's primary concern was to get a better idea of how extraterrestrial life might evolve elsewhere, and how long it takes a sentient species to evolve, against a planet's time in a habitable zone. The team calculated that earth's habitable zone classification might span a maximum of 7.79 billion more years, though we've already ran through 4.5 billion of those. Mars still has another 7 billion years, and is the closest - so moving there would be anyone's best bet. Other planetary habitable zone lifetimes in our solar system range from 1 billion to 54.72 billion years.
One might wonder why any of this is relevant, considering that human evolution has been but a hiccup in the formation of the solar system, and that we might evolve into space gods like the Q Entity in a billion years - or devolve into planaria-like beings. Either way, single-celled life first appeared on earth roughly 4 billion years ago. Then we had "insects 400 million years ago, dinosaurs 300 million years ago and flowering plants 130 million years ago," according to research project lead Andrew Rushby, who adds, "anatomically modern humans have only been around for the last 200,000 years — so you can see it takes a really long time for intelligent life to develop."
With all the new data, Rushby's team was able to implement a new system to gauge how long a planet would have, to support the evolution of life, as it exists in a habitable zone. Rushby adds, “Of course, much of evolution is down to luck, so this isn’t concrete, but we know that complex, intelligent species like humans could not emerge after only a few million years because it took us 75 per cent of the entire habitable lifetime of this planet to evolve. We think it will probably be a similar story elsewhere.”
Regarding exoplanets, the team calculated that Kepler-22b has perhaps been habitable for 6 billion years, and Gliese-581d for 54.7 billion years. As our technology advances, we'll be able to get a better idea of what's actually going on in those planets; Rushby adds, “As it stands, we don’t have the technology to explore these planets to discover if there is alien life, but I’d certainly mention Kepler-22b and Gliese-581d as planets that we should keep an eye over the next two or three hundreds years of human existence as our technology develops.”
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