What if the Earth spun sideways on its axis

The Earth spins on a 23.5-degree tilt, which causes the seasons. But if the planet tilted more, all the way to 90 degrees, it would throw the world into chaos. The Northern Hemisphere would experience a six-month-long winter that would devastate the ecosystem and destroy crops. After that, a six-month-long summer that would melt the ice caps, raise sea levels, and flood coastal cities.

Video Transcript

- Early in the history of our solar system, something mysteriously knocked Earth slightly off its axis. So today, we tilt at 23.5 degrees. But what would happen if we tilted even more? What if Earth spun sideways on its axis?

Well, 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, and 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 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 from 15.5 degrees Celsius. That's hotter than temperatures at the Equator today. As a result, Greenland's ice cap would melt, causing sea levels to rise by seven meters 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 sea water 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 degrees Celsius from negative 28 degrees Celsius, melting the ice and raising sea levels by a whopping 61 meters. 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.