Home

 › 

Articles

 › 

Concepts

 › 

How Fast Is the Earth Actually Spinning?

Sphere of nightly Earth planet in outer space. City lights on planet. Life of people. Solar system element. Elements of this image furnished by NASA

How Fast Is the Earth Actually Spinning?

Key Points

  • The Earth used to spin much faster, with days lasting only four hours about 4.5 billion years ago.
  • Geophysicists estimate the Earth’s rotational speed at about 1,670 kilometers per hour, which decreases as you measure closer to the planet’s north and south poles.
  • The moon’s gravity and relative location have slowed down the Earth’s rotation over time, and the melting ice caps could potentially lead to changes in how the Earth rotates.
  • The first instrument to provide direct evidence of Earth’s rotation was invented in 1851 by Léon Foucault, and the invention of the atomic clock in 1949 allowed scientists to identify an even more precise number for Earth’s velocity.
  • The Earth’s rotational velocity plays a role in several aspects of its character, including the reason why we have 24-hour days and the planet’s form, which is not perfectly round.

Have you ever looked at your clock and wondered why there isn’t more time in a day? Well, what if we told you there used to be much less? Okay, it was about 4.5 billion years ago, but days on our planet lasted only four hours. The length of our day has a lot to do with how fast the Earth is spinning.

There are a lot of factors that affect the rotational speed of our planet. From the Moon’s relationship to our melting ice caps to even earthquakes, measuring its velocity takes careful practice and equipment. Keep reading to learn more about how it works.

How Fast Is the Earth Spinning?

Measuring how fast the Earth is spinning isn’t a simple task. Geophysicists use atomic clocks, which can tell time to the nanosecond, to accurately determine where the planet sits at a given time. Along with this knowledge, they use satellites to observe the rotation and any given variations.

On average, geophysicists estimate the Earth’s rotational speed at about 1,670 kilometers per hour (or 1,038 miles per hour). This number actually decreases as you measure closer to the planet’s north and south poles. Factors such as atmospheric and gravitational influences can cause the speed to fluctuate.

The Earth’s rotational velocity plays a role in several aspects of its character. For example, It’s the reason why we have 24-hour days. Compared to Saturn, which spins at about 36,840 kph, the Earth’s days last nearly 2.5 times longer.

Additionally, the planet’s speed has an effect on its form. If you were to look at the Earth from space, you’d notice that it’s not perfectly round. The Earth actually flattens at the poles and bulges at the equator. The faster it spins, the further the planet’s mass spreads, and vice versa.

Saturn planet with rings in outer space among star dust and srars. Titan moon seen. Elements of this image furnished by NASA.
Spinning at a speed of 36,840 kph, Saturn’s days only last about 10.7 hours.

When Did We Start Measuring Earth’s Rotation?

You can trace speculation of Earth’s rotation back to Greek astronomers, but the first instrument to provide direct evidence didn’t come about until 1851. Léon Foucault invented the pendulum, which teetered in a circular motion. Demonstrating the foundation of the Coriolis effect, astronomers and physicists began studying the phenomenon. 

Foucault’s experiments provided the information needed to accurately measure Earth’s velocity, even with varying conditions such as natural disasters. However, with the invention of the atomic clock in 1949, scientists were able to identify an even more precise number. Advanced technology allows us to practically see into the past and future.

Speed of Earth’s Rotation Over Time

We’ve discovered that the Earth used to spin much faster. However, the Moon uses its gravity and relative location to slow our planet down. At the start of its lifetime, the moon was much closer to the Earth. Spinning at a speed related to a four-hour day, the Moon began to fall out of orbit. The farther it got, the slower our planet’s rotation.

Additionally, the Moon has slightly slowed it down over time due to its gravitational pull on the oceans. Where it sits relative to the Earth causes our bodies of water to bulge toward it. Now, because our planet spins faster than the moon orbits, that bulge is ahead. Pulling against the natural direction of orbit, the ocean bulge forces the Earth to slow its rotational speed.

HEXEUM telescope
The gravitational pull of the Moon helps to slow our planet down.

The Future of Earth’s Rotation

At the current moment, geophysicists have their eyes on the melting ice caps and its effect on how fast the Earth is spinning. When these heavy glaciers melt and their weight is reduced, the earth under them rises up, redistributing the planet’s mass. This could potentially lead to changes in how the Earth rotates.

As our planet’s temperatures continue to rise, we also watch for the effects of natural disasters such as earthquakes. Alongside the melting ice caps, an overheating of our planet causes more intense phenomena. These can result in much quicker rotational effects.

So if you’re looking for more time in your day, you might take a look at your carbon footprint. Managing surface temperature balances our oceans, keeping them ideal for the moon’s gravitational pull and forever slowing the Earth’s pace, 1.7 milliseconds every century.

Frequently Asked Questions

How fast does the Earth spin?

The Earth spins at an average rotational speed of approximately 1,670 kilometers per hour at the equator. That’s equal to about 1,038 miles per hour.

Is the Earth slowing down?

Yes, the Earth is gradually slowing down in its rotation, with the length of a day increasing by approximately 1.7 milliseconds per century due to factors like tidal interactions with the Moon.

Is it bad if the Earth slows down?

The gradual slowing of the Earth’s rotation has minimal immediate impact on daily life, but over extremely long periods, it can have subtle effects on climate, ecosystems, and geological processes.

How does the rotational speed affect the way the Earth looks?

If you looked at the Earth from space, you would see it flattens at the poles and bulges at the equator. The faster it spins, the further the planet’s mass spreads, and vice versa.

To top