Imagine if the Earth suddenly stopped spinning. The first thing you’d notice is that you’d gain weight, but that would be the least of your worries. The spin of our planet is crucial, giving us the time of our lives. At the equator, the surface of Earth, and everything on it, is spinning around at 465 meters per second. As you move closer to the poles, you don’t have to move as quickly to complete Earth’s daily rotation. For instance, in San Francisco, the Earth is driving east at 368 meters per second.
If we could float above the surface independent of the Earth’s rotation, the Earth would spin underneath us at a remarkable speed. However, when we jump straight up into the air, the Earth doesn’t move underneath us because we continue to spin with it. We are all spinning with the Earth, and that’s why slamming on a set of magical planetary brakes that caused everything classically called earth to stop spinning would be catastrophic.
Immediately everything that wasn’t Earth, and wasn’t safely at the poles, would continue moving as it had been, and be flung due east at more than a thousand miles an hour. You wouldn’t be flung into space because escape velocity is 24,800 mph, but your body would instantly become a 9.5-inch caliber bullet. More accurately, a supersonic tumbleweed. Because the atmosphere would more gradually slow down, people in airplanes, assuming they could navigate the resulting storms, might have a better chance of surviving. Astronauts aboard the ISS would fare even better. But it is unlikely that anyone would be waiting for them down on the ground. Runways would just be entrances to the new planet-sized graveyard, created by the no longer spinning Earth.
People really near the poles might be okay but only at first. Gusts of wind, as fast as those near an atomic bomb detonation, would blast past the surface and up into the sky forming worldwide storms of unprecedented magnitude. The friction alone, caused by the now stopped Earth colliding with these winds, would be enough to cause massive fires, unparalleled erosion, and damage to anything strong enough to stay put after the initial braking. The Sun would seem to freeze in the sky as days became not 24 hours long but 365 days long.
Without spinning innards, Earth’s protective magnetic field would cease to exist and we would be dosed with deadly amounts of ionizing radiation from the Sun. The oceans would surge onto land in tsunamis kilometers high and wash over nearly all dry land, before migrating to the poles, where gravity is stronger, no longer held to the ocean basins by the inertia Earth’s spin gave them. Earth itself, no longer bulging an extra 42 kilometers around its equator because of its rotation, would slowly compress into a more perfect sphere than it is now. This could possibly allow the oceans to eventually return somewhat.
If the Earth is spinning so quickly, why can’t we feel it? Why doesn’t the Earth’s rotation make us dizzy? Luckily for us, the change in velocity is just too gradual. The Earth is too huge. It’s like driving in a car that takes 6 hours and six thousand miles to make one left turn. It’s not sudden enough to register with our senses. But that change in velocity is real and it makes us weigh less, because of inertia.
On our spinning planet, your velocity is constantly changing but always tangential to the circular path you are being dragged along. Now, because inertia is a property of matter, which includes your body, without a force acting upon us we would slowly leave the surface of Earth. Luckily, the Earth is exerting a force on us. A center-seeking, centripetal force, delivered by gravity. The centripetal force required to keep you along a circular path with Earth is subtracted from Earth’s total gravitational pull on you. The remaining force simply pushes you down, toward the center of the Earth – it gives you weight.
We know exactly how long a second is. The outermost electron of an atom of cesium 133 is alone. When the atom is undisturbed, only the nucleus interacts with this outermost electron, tickling it regularly and rapidly between two levels. After 9,192,631,770 oscillations between those two levels, one second has passed. Exactly. That is literally the definition of a second. We can measure and count those oscillations. It’s how atomic clocks work. Making atomic clocks, the most accurate measurement device ever built by humans, to measure anything.
We can’t define a second more simply, as say, 1/60th of 1/60th of 1/24th of a day because of Earth’s spin. It’s too irregular. Little changes in the distribution of mass on Earth, caused by earthquakes or melting ice or man-made dams or technically even you walking up stairs or downstairs, cause Earth’s rotational speed to change. Like a figure skater moving their arms further away from or closer to their bodies. Now add on top of that the fact that tides, caused by the Moon, drag against Earth’s rotation and you wind up with an unstable rotation speed that is predominantly slowing down.
Now, these changes are incredibly slight, but over time they add up. In 140 million years, a day on earth will not be 24 hours long, it will be 25. That might not sound like much but in order to do important things, like deliver accurate GPS information, we need a more accurate timekeeping device than that. So, as a solution, scientists keep the pace of seconds using atomic clocks, TAI time. And other scientists measure the changing speed of Earth’s rotation by observing distant stars and quasars. Now, every few months they find out just how behind or ahead Earth is running, and if it’s getting too close to being a second off, they decide to add or subtract the second from the current year. The result is the time used almost everywhere, including your phone: UTC.
Since this system began in 1972, 25 leap seconds have been added. What this means is that clock time is, and has to be, a manufactured product with upgrades and tune-ups administered periodically, after defects are noticed. The time we give to now and the future is only ever approximate. That’s weird but it’s also entirely not weird. As Demetrios Matsakis, the Chief Scientist of Time Services for the US Naval Observatory puts it, “we save lives and we end lives. We add time and we can take time away, but in both cases we do so without completely understanding exactly what life is, or what time is.” Regardless, thank you for spending some of yours with me…and as always, thanks for watching.
Build a simple model to demonstrate Earth’s rotation. Use a globe or a ball to represent Earth and a flashlight to represent the Sun. Rotate the globe to show how day and night occur. Discuss how the speed of rotation varies from the equator to the poles.
Conduct a classroom experiment using a spinning top or a rotating chair. Have a student spin the top or sit on the chair and then abruptly stop it. Observe and discuss the effects of inertia and how it relates to the catastrophic consequences if Earth suddenly stopped spinning.
Research different types of natural disasters that could occur if Earth stopped spinning, such as massive storms, tsunamis, and fires. Create a presentation or poster to share your findings with the class, explaining the science behind each disaster.
Use a bar magnet and iron filings to visualize magnetic fields. Discuss how Earth’s magnetic field protects us from solar radiation and what would happen if it disappeared. Create a diagram showing the magnetic field lines around Earth.
Use a formula to calculate how much you would weigh at different latitudes due to Earth’s rotation. Compare your weight at the equator, mid-latitudes, and poles. Discuss how the centripetal force affects your weight and why you weigh less at the equator.
earth – the third planet from the sun in our solar system; the planet on which we live – The earth is home to a diverse range of ecosystems and life forms.
spinning – rotating rapidly around an axis – The Earth is constantly spinning on its axis, completing one rotation every 24 hours.
weight – the force with which a body is attracted toward the Earth or another celestial body, equal to the product of the object’s mass and the acceleration due to gravity – The weight of an object on Earth is greater than on the moon due to the difference in gravitational pull.
equator – an imaginary line drawn around the Earth, equally distant from both poles, dividing the Earth into northern and southern hemispheres – Countries located near the equator experience higher temperatures throughout the year.
poles – the two points on the Earth’s surface that are farthest from the equator, located at the north and south ends of the planet – The Arctic Circle is located near the North Pole, while the Antarctic Circle is near the South Pole.
catastrophic – involving or causing great damage, suffering, or destruction – The earthquake had a catastrophic impact on the region, leaving thousands of people homeless.
storms – violent disturbances of the atmosphere characterized by strong winds, rain, thunder, lightning, etc. – The severe thunderstorm brought heavy rain, strong winds, and lightning to the area.
magnetic field – a region around a magnetic material or a moving electric charge within which the force of magnetism acts – The Earth’s magnetic field helps protect the planet from harmful solar radiation.
oceanic displacement – the movement or shifting of water in the ocean caused by factors such as tides, currents, or seismic activity – The tsunami resulted in significant oceanic displacement, leading to massive waves hitting the coastline.
rotation – the circular movement or spin around an axis – The Earth’s rotation causes day and night, with one complete rotation resulting in a full day.
