Today, the sun is an important source of gravity and energy. But one day it will cause the end of the earth. As the Solar systems central stellar ages, its life cycle will eventually consume our blue marble.
So how long The earth have until the planet is swallowed by the sun? Expected time of death: several billion years from now. But life on earth will end much, much sooner than that.
Earth will become inhospitable to most organisms in about 1.3 billion years due to the sun’s natural evolution, experts told Live Science. And humans could easily drive ourselves (and countless other species) to extinction within the next few centuries, at the current rate of human-made climate change is not mitigated.
Related:Is the Earth moving closer to the Sun, or further away?
Death of the Sun
The ultimate curtain for our planet is tied to the evolution of the sun.
“The Earth probably has 4.5 billion years before the Sun becomes a big red giant and then engulfs the Earth.” Ravi Kopparapu, a planetary scientist at NASA’s Goddard Space Flight Center, told Live Science. A red giant is formed in the final stages of stellar evolution, when the star runs out of hydrogen to fuel its nuclear fusion and so begins to die, according to European Space Agency.
When fusion ceases, gravity will take over. The helium core will begin to compress under gravity, which will raise the temperature. This spike in heat will cause the outer plasma layer the sun to expand dramatically. “The Sun will swell to at least the size of Earth’s orbit,” Kopparapu said.
Earth’s fate
But Earth likely won’t last those 4.5 billion years, and it definitely won’t be Earth as we know it.
“You don’t have to wait for the outer layers [of the sun] to reach Earth,” he said. The planet will experience extreme heat long before the sun completes its transition to a red giant. As the sun’s dying process increases the temperature, “the oceans will evaporate, then the atmosphere will eventually disappear, and then the tidal forces from the sun’s gravity will shatter the earth.”
About 1.3 billion years from now, “humans will not be able to survive physiologically, in nature, on Earth” due to hot and humid conditions. In about 2 billion years, the oceans could evaporate when the sun’s brightness is almost 20% more than now, Kopparapu said.
Some life can survive to this point – as “extremophiles” that live near hydrothermal vents in the ocean floor — but not humans, Kopparapu said.
“Humans – and all complex life – are extremely needy,” Rodolfo Garcia, a graduate student in astronomy and astrobiology at the University of Washington, told LiveScience. In humans, for example, a fever of only 6 degrees Fahrenheit (3.3 degrees Celsius) is life-threatening, he said.
Dangerous wet-bulb temperatures — a combination of temperature, humidity, wind speed, sun angle and cloud cover — where people can no longer cool themselves by sweating is much more imminent, just a few degrees away, Kopparapu said.
The wet bulb threshold for humans was first predicted to be 95 F (35 C), but recent research suggests temperatures as low as 86 F (30 C) can be fatal.
Some places on Earth have already reached wet-bulb temperatures above 90 F (32 C) on several occasions, and climate models predict that 95 F (35 C) will be a regular occurrence in regions such as the Middle East at the end of the century. At that temperature, animals that sweat will essentially cook in the heat, Kopparapu said. Essentially our own greenhouse gases will threaten life and society on Earth long before the sun dies.
“If we’re talking about human life, the next hundred years will be interesting,” Kopparapu said.
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