Watch: If Earth spun sideways, extreme winters and summers would doom life as we know it
- Earth spins on a 23.5-degree tilt, which is responsible for the seasons as we know them.
- But if Earth's axis tilted to 90 degrees, extreme seasons would cause intense climate change on every continent.
- During the summer, the Northern Hemisphere would experience nearly 24 hours of sunlight for months, which could melt ice caps, raise sea levels, and flood coastal cities.
- In the winter, it would get nearly 24 hours of complete darkness, killing plants, ecosystems, and crops.
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Early in the history of our solar system, something mysteriously knocked Earth slightly off its axis. So today we tilt at 23.5 degrees. If it tilted any more, or the Earth spun sideways on its axis, it wouldn't take long before utter chaos ensued.
One of the most important consequences of Earth's axial tilt is the seasons. Seasons happen because the tilt points different parts of the planet toward the sun at different times of the year. But the tilt also means that different parts of the globe receive different amounts of sunlight during each season
That's where a more extreme tilt starts to cause problems. Right now, during the summer in the Northern Hemisphere, places far north, like Utqiagvik, Alaska, receive 24 hours of sunlight for 82 days straight. Because Earth is tilted far enough on its axis that as the planet rotates, Utqiagvik never leaves direct sunlight.
On the other hand, the contiguous United States (US) receives a max of 17 hours a day, because after that it rotates out of daytime sunlight and into night. But if we tilted Earth's axis even more, to 90 degrees, the US would get sunlight 24/7, around the clock, for months on end. And it's not just the US; the entire Northern Hemisphere would be like this.
At first, animals would take advantage of the extra light to find and eat more food, just like Alaskan birds, which feed their chicks extra nutrition in the summer, resulting in faster-growing babies than their southern counterparts. And plant growth would explode since they get their energy directly from sunlight. Farms in northern Alaska, for example, grow cabbages the size of rottweilers in the summer.
But while animals and plants would thrive, humans wouldn't. We evolved to be active during the day and sleep at night. But if we were exposed to unending sunlight, our brains would stop producing the hormone melatonin, which we need to sleep at night. And that could lead to sleep deprivation, depression, and, ultimately, a more severe, chronic version of these symptoms called seasonal affective disorder, which already affects 9% of Alaskans, compared to just 6% of the entire United States.
But that's less of a worry than the floods. Temperatures at the North Pole would more than double, to 38 degrees Celsius (°C) from 15.5°C. That's hotter than temperatures at the equator today. As a result, Greenland's ice cap would melt, causing sea levels to rise by 7 metres (m), and flood nearly every coastal city on Earth. Say goodbye to New York, Copenhagen, and Tokyo. To make matters worse, the warmer seas would trigger stronger and more frequent hurricanes, which form when seawater evaporates at the surface.
And the weather wouldn't get better when winter comes six months later. Out of reach of the sun's direct beams for months at a time, the hemisphere would get colder than any winter on record. Swirls of frigid air, called a polar vortex, which are normally dissipated by warm air in the tropics, could travel all the way down to the equator. Imagine blizzards in Florida, Brazil, Kenya! And all those thriving plants, they'd die from a lack of sunlight. Agriculture would collapse as ecosystems crumble and mass extinctions pile up.
And there would be even more floods, because meanwhile, the Southern Hemisphere is getting toasty and the South Pole is home to 90% of the world's ice. The constant sunlight would raise its temperature to 38 °C from -28 °C, melting the ice and raising sea levels by a whopping 61m. That's almost as tall as the Leaning Tower of Pisa. Greenland's flood would look like a puddle in comparison.
So all in all, while a few extra hours in the summer sun would be nice, let's leave the extra seasons to Alaska and be glad the Earth is tilted exactly as it is.
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