How Much Time Do We Have Left on Earth

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Let’s face it: The planet is heating up, Earth’s population is expanding at an exponential rate, and the the natural resources vital to our survival are running out faster than we can replace them with sustainable alternatives. Even if the human race manages not to push itself to the brink of nuclear extinction, it is still a foregone conclusion that our aging sun will expand and swallow the Earth in roughly 7.6 billion years.
So if you’re planning to live forever, you’ve got about 2 billion years to find a new planet to inhabit.
According to new research, it’s impossible for life on Earth to endure much longer than that. Earth exists, and has always existed, in what’s known as the habitable zone — the area around a star at which liquid water can flow. But as stars, like our sun, fuse hydrogen into helium, the amount of heat they emit increases over time, reports The Guardian, pushing the line of the habitable zone farther away from the star and scorching regions nearby.
In research published September 19 in the journal Astrobiology, a team led by Andrew Rushby from the University of East Anglia in the United Kingdom used models of stellar evolution to estimate how long Earth and other planets will stay in their habitable zones. They found that somewhere between 1.75 billion and 3.25 billion years from now, the sun will heat the Earth so much that oceans will evaporate and life will be wiped out, according to a University of East Anglia news release.

“We would see a catastrophic and terminal extinction event for all life,” Rushby said in the release. “Of course, conditions for humans and other complex life will become impossible much sooner — and this is being accelerated by anthropogenic climate change. Humans would be in trouble with even a small increase in temperature, and near the end only microbes in niche environments would be able to endure the heat.”
So, according to famed theoretical physicist Stephen Hawking, it’s time to free ourselves from Mother Earth. “I believe that the long-term future of the human race must be in space,” Hawking tells Big Think. “It will be difficult enough to avoid disaster on planet Earth in the next hundred years, let alone the next thousand, or million. The human race shouldn’t have all its eggs in one basket, or on one planet. Let’s hope we can avoid dropping the basket until we have spread the load.”

Hawking says he is an optimist, but his outlook for the future of man’s existence is fairly bleak. In the recent past, humankind’s survival has been nothing short of “a question of touch and go” he says, citing the Cuban Missile Crisis in 1963 as just one example of how man has narrowly escaped extinction. According to the Federation of American Scientists there are still about 22,600 stockpiled nuclear weapons scattered around the planet, 7,770 of which are still operational. In light of the inability of nuclear states to commit to a global nuclear non-proliferation treaty, the threat of a nuclear holocaust has not subsided.
In fact, “the frequency of such occasions is likely to increase in the future,” says Hawking, “We shall need great care and judgment to negotiate them all successfully.”

Even if humans manage to avoid a nuclear stand-off over the next thousand years, our fate on this planet is still pretty much certain. University of Sussex astrophysicist Dr. Robert Smith says eventually the aging Sun will accelerate global warming to a point where all of Earth’s water will simply evaporate.”Life on Earth will have disappeared long before 7.6 billion years,” says Smith, “Scientists have shown that the Sun’s slow expansion will cause the temperature at the surface of the Earth to rise. Oceans will evaporate, and the atmosphere will become laden with water vapor, which (like carbon dioxide) is a very effective greenhouse gas. Eventually, the oceans will boil dry and the water vapor will escape into space. In a billion years from now the Earth will be a very hot, dry and uninhabitable ball.”

“The nearest star to Earth is Proxima Centauri which is 4.2 light years away,” says University of Michigan astrophysicist Katherine Freese, “That means that, if you were traveling at the speed of light the whole time, it would take 4.2 years to get there.”

Unfortunately, at the moment we can only travel at about ten thousandth of light speed, which means if man were to use chemical fuel rockets similar to the those used during the Apollo mission to the moon, the journey would take about 50,000 years. Without the use of a science-fiction-like warp drive or cryogenic freezing technology, no human would live long enough to survive the journey. In addition, “the radiation you would encounter alone would kill you, even if you could get a rocket to go anywhere near that fast,” says Freese.

On the upside, if man ever develops the technology to travel at the speed of light while remaining shielded from cosmic radiation, he could effectively travel into the future. “A five year trip at light speed could push an astronaut forward by 1000 earth years,” says Freese, “If he wanted to see if any humans were still around by then.” If humans are still around when the oceans get close to boiling, our best bet for a new home is Mars, according to Rushby, as the red planet remains in the habitable zone until the sun dies, about 6 billion years from now.

Humans may well have evolved into a new form by then, Rushby told The Guardian. Indeed, a primary aim of the study was not necessarily to plan a timeline for Earth, according to Discovery, but to study the rates of evolution of intelligent life.

Since discovery of the first exoplanet — a planet around another star — in 1995, thousands of potential exoplanets have been detected throughout the universe. Rushby and his team used their model to estimate habitable zone lifetimes of eight exoplanets. Knowing that it took about 75 percent of the Earth’s current 4.5-billion-year lifetime for humanity to evolve, scientists can extrapolate and imagine the possibilities of intelligent life elsewhere.

“The amount of habitable time on a planet is very important because it tells us about the potential for the evolution of complex life, which is likely to require a longer period of habitable conditions,” Rushby said. “Looking at habitability metrics is useful because it allows us to investigate the potential for other planets to host life, and understand the stage that life may be at elsewhere in the galaxy.”