How fast is the world spinning?

There are enough things to worry about in this life. Like nuclear war, climate change and whether you brush your teeth properly. Earth spinning too fast shouldn’t be at the top of your list because it’s unlikely to happen anytime soon – and if it does, you’re probably too dead to worry about it. Still, we spoke to some experts to see how everything would go.

Let’s start with the basics, for example: How fast is the Earth spinning now? It depends on where you are, because the planet moves fastest around its waist. As the Earth rotates on its axis, its circumference is the widest at the equator. Thus, for a point on the equator to return to its initial position, it would have to travel much farther in 24 hours than, for example, Chicago, located on a narrower cross-section of the Earth. To compensate for the extra distance, the equator rotates at 1,037 mph, while Chicago rotates at a slower speed of 750 mph. (This calculator will tell you the exact speed based on your latitude.)

The world occasionally changes its pace, but only gradually. This summer, for example, slipped 1.59 milliseconds from the typical return time, making June 29 the shortest day on record. One hypothesis is that changes in pressure are actually changing the planet’s axis of rotation, though not to the extent that normal people can feel the difference.

Small bumps aside, if the Earth were suddenly spinning much faster, there would be some drastic changes. Let’s say accelerating its spin by one mile per hour causes water to migrate from the poles and raise levels around the equator a few inches. “It may take several years to realize that,” says Witold Fraczek, an analyst at ESRI, a company that makes geographic information system (GIS) software.

[Related: If the Earth is spinning, why can’t I feel it?]

What is even more remarkable is that some of our satellites may have gone off course. Satellites set in geosynchronous orbit fly around our planet at a speed equivalent to Earth’s rotation, so they can stay positioned on the same spot all the time. If the planet accelerates to 1 mph, the satellites will no longer be in their proper positions, meaning satellite communications, television broadcasts, and military and intelligence operations may be interrupted, at least temporarily. Some satellites carry fuel and can adjust their position and speed accordingly, but others may need to be replaced and this is expensive. “These may disrupt the life and comfort of some people, but they should not be disastrous for anyone,” says Fraczek.

But the faster we turn around, the more disastrous things get.

You lose weight, but you cannot lose weight.

The centrifugal force from the Earth’s rotation is constantly trying to throw you off the planet, like a child on the edge of a fast carousel. For now, gravity is stronger and keeps you grounded. But NASA astronomer Sten Odenwald says the centrifugal force will increase if the Earth spins faster.

Currently, if you weigh around 150 pounds at the Arctic Circle, you might weigh 149 pounds at the equator. This is because of the extra centrifugal force created when fighting equatorial gravity faster. Press fast forward and your weight will drop even more.

Eventually, Odenwald calculates, if the equator rises to 17,641 mph, the centrifugal force will be large enough to make you essentially weightless. (So, if you’re still alive. We’ll talk later.)

Everyone would be constantly jet lagged.

The faster the earth rotated, the shorter our days would be. With a mile-per-hour increase, the day gets shorter by only about a minute and a half, and our internal body clocks, which are tied to a pretty strict 24-hour schedule, probably won’t notice it.

But if we were spinning 100 miles faster than normal, a day would be about 22 hours. For our bodies, this would be like daylight saving time on boosters. Instead of turning the clocks back one hour, you’re going back two hours every day before your body has a chance to adjust. And the varying day length will likely devastate plants and animals as well.

But all this only happens if the Earth accelerates suddenly. “If it accelerates gradually over millions of years, we’ll adapt to deal with it,” says Odenwald.

Hurricanes would get stronger.

If Earth’s rotation was slow, it would carry the atmosphere with it, and we wouldn’t need to see a big difference in diurnal winds and weather patterns. “The temperature difference will continue to be the main driver of winds,” says Odenwald. However, extreme weather can become more devastating. “Hurricanes will spin faster,” he says, “and there will be more energy in them.”

That’s because it goes back to that weird phenomenon we talked about earlier: Earth is spinning faster around the equator.

If the Earth did not rotate at all, the winds from the north pole would blow in a straight line towards the equator and vice versa. But as we turn, the path of the winds deviates to the east. This curvature of winds is called the Coriolis effect, and it’s what makes a hurricane spin. And if the Earth rotates faster, the winds will deviate further east. “This effectively makes the spin more violent,” says Odenwald.

Water would cover the earth.

The extra velocity at the equator means that water in the oceans will start accumulating there. 1 mph faster, the water around the equator will go a few inches deeper in just a few days.

100 mph faster, the equator would begin to choke. “I think the Amazon Basin, Northern Australia, and islands in the equatorial region, not to mention the islands, would all have been submerged,” says Fraczek. “I’m not sure how deep underwater, but I would estimate it to be 30 to 65 feet.”

Fraczek says that if we doubled the speed at the equator to make the Earth spin 1,000 miles faster, it would “clearly be a disaster.” Centrifugal force would pull hundreds of feet of water to the waist of the Earth. “I think everything in the equatorial region will be covered in water, except for the highest mountains like Kilimanjaro or the highest peaks of the Andes.” This extra water will be drawn from the polar regions where the centrifugal force is lower, so the Arctic Ocean will be much shallower.

100 mph faster, the equator would begin to choke.

Meanwhile, the added centrifugal force from spinning 1,000 mph faster means water at the equator will more easily fight gravity. Fraczek predicts that the air in these areas will be heavier than moisture. In these regions, which are covered with dense fog and dense clouds, it can rain constantly, as if they need more water.

Finally, at about 17,000 miles per hour, the centrifugal force at the equator matches the force of gravity. After that, “we might experience back rain,” Fraczek predicts. “Water droplets can start moving in the atmosphere.” At that point, Earth would be spinning 17 times faster than it does now, and there probably wouldn’t be many people left in the equatorial region to admire the phenomenon.

“If these poor few people were still alive after most of Earth’s water had been transferred to the atmosphere and beyond, they would want to get out of the equatorial region as soon as possible,” says Fraczek. Be in the polar regions, or at least in the mid-latitudes.

Seismic activity shakes the planet.

At very high speeds of about 24,000 mph and over thousands of years, the Earth’s crust would eventually change as well, flattening at the poles and swelling around the equator.

“We would have tremendous earthquakes,” Fraczek says. “Tectonic plates move rapidly, and that would be disastrous for life on Earth.”

How fast would the world spin in the future?

Believe it or not, Odenwald says Earth’s speed is constantly fluctuating. Earthquakes, tsunamis, large air masses, and melting ice sheets can change the rotational speed in milliseconds. If an earthquake swallows part of the earth, it shrinks the planet’s environment. never so little, effectively speeding up how fast the Earth completes its rotation. A large mass of air can have the opposite effect, slowing our turns a bit like an ice skater whose arms are out instead of pulling in.

Earth’s rotation speed also changes over time. About 4.4 billion years ago, the Moon was formed when something very large hit the Earth. Odenwald calculates that at that time our planet was probably in the shape of a flattened soccer ball and was spinning so fast that each day could only last about four hours.

“This event significantly distorted the Earth’s shape and almost completely shattered the Earth,” says Odenwald. “Will this happen again? We better not hope!”

[Related: 10 easy ways you can tell for yourself that the Earth is not flat]

Since the moon’s formation, Earth’s rotation has slowed to about 6.8 km/s every 10 million years, mostly due to the moon’s gravity on our planet. Therefore, it is much more likely that Earth’s rotation will continue to slow down rather than speed up in the future.

“There is no plausible way for the Earth to spin so dramatically,” says Odenwald. “It would have to be hit exactly by the right object for it to spin faster, and that would liquefy the shell so we’d be dead anyway.”

This post has been updated. Originally published on May 17, 2017.

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