Why is Earth Spinning FASTER?
Intro What if someone were to tell you that at any
given moment, you were traveling at speeds well over the speed of sound?
You might think they were crazy, given that – as best as you could tell – you were
standing on solid ground, and not in the cockpit of a supersonic jet.
Nevertheless, the statement is correct.
At any given moment, we are all moving at a speed of about 1,040 Miles an hour, thanks
to the Earth's rotation.
If that wasn't crazy enough, new studies suggest that the Earth is starting to spin even faster!
Let's take a closer look.
The Rotation of the Earth Some of the earliest astronomers in recorded
history proposed that we live in a geocentric universe in which Earth lies at the center
of everything.
According to them, the sun rotated around us, which caused sunrises and sunsets — the
same for the movements of the moon and the planets.
But even then, certain things didn't exactly line up with these theories.
For example, sometimes, a planet would back up in the sky before resuming its forward
motion.
We know now that this back-and-forth — which is called retrograde motion — happens when
Earth is "catching up" with another planet in its orbit.
For example, Mars orbits farther from the sun than Earth.
So, at one point in the planets' respective orbits, Earth catches up to the Red Planet
and passes it by.
As we pass Mars by, it moves backward in the sky and then forward again after we have passed.
Another reason that humans started to realize that we might not be the center of the universe
came from looking at parallax, or apparent change in the position of the stars with respect
to each other.
For a simple example of parallax, hold up your index finger in front of your face at
arm's length.
Look at it with your left eye only, closing your right eye.
Then close your right eye, and look at the finger with your left.
The finger's apparent position changes.
That's because your left and right eyes are looking at the finger with slightly different
angles.
The same thing happens on Earth when we look at stars.
It takes about 365 days for us to orbit the sun.
If we look at a star located relatively close to us in the summer and look at it again in
the winter, its apparent position in the sky changes because we are at different points
in our orbit.
We see the star from different vantage points.
With a bit of simple calculation, using parallax we can also figure out the distance to that
star.
Earth's spin is constant, but the speed depends on what latitude you are located at.
Here's an example.
According to NASA the circumference of the Earth is roughly 24,898 miles.
If you estimate that a day is 24 hours long, you divide the circumference by the length
of the day.
This produces a speed at the equator of about 1,037 mph.
You won't be moving quite as fast at other latitudes, however.
If we move halfway up the globe to 45 degrees in latitude, you calculate the speed by using
the cosine of the latitude.
The cosine of 45 is 0.707, so the spin speed at 45 degrees is roughly 0.707 x 1037 = 733
mph.
That speed decreases more as you go farther north or south.
By the time you get to the North or South poles, your spin is very slow indeed — it
takes an entire day to spin in place.
Space agencies love to take advantage of Earth's spin.
If they're sending humans to the International Space Station, for example, the preferred
location to do so is close to the equator.
That's why cargo missions to the International Space Station, for example, launch from Florida.
By doing so and launching in the same direction as Earth's spin, rockets get a speed boost
to help them fly into space.
Earth's spin, of course, is not the only motion we have in space.
Our orbital speed around the sun is about 67,000 mph.
We can calculate that with basic geometry.
First, we have to figure out how far the Earth travels.
Earth takes about 365 days to orbit the sun.
The orbit is an ellipse, but to make the math simpler, let's say it's a circle.
So, Earth's orbit is the circumference of a circle.
The distance from Earth to the sun — called an astronomical unit— is 92,955,807 miles,
according to the International Astronomers Union.
That is the radius (r).
The circumference of a circle is equal to 2 x π x r.
So, in one year, Earth travels about 584 million miles.
The sun has an orbit of its own in the Milky Way.
The sun is about 25,000 light-years from the center of the galaxy, and the Milky Way is
at least 100,000 light-years across.
We are thought to be about halfway out from the center, according to Stanford University.
The sun and the solar system appear to be moving at 124 miles per second, or at an average
speed of 448,000 mph.
Even at this rapid speed, the solar system would take about 230 million years to travel
all the way around the Milky Way.
The Milky Way, too, moves in space relative to other galaxies.
In about 4 billion years, the Milky Way will collide with its nearest neighbor, the Andromeda
Galaxy.
The two are rushing toward each other at about 70 miles per second.
Everything in the universe is, therefore, in motion.
But what happens when this motion suddenly changes?
Spinning Faster New research suggests that our home planet
is in a hurry.
On June 29, 2022, Earth completed the shortest day since scientists started keeping records
in the 1960s, pulling off a full rotation 1.59 milliseconds faster than usual.
Terrestrial haste is a trend.
In 2020, the planet recorded the 28 shortest days on record, and it kept spinning rapidly
into 2021 and 2022.
Before scientists could even verify that record-setting day time of June 29, our world almost outdid
itself: It blazed through July 26, 2022, 1.50 milliseconds ahead of schedule.
Scientists believe that we will likely see more record-short days as Earth continues
to accelerate.
However, the fact that the Earth’s days are getting shorter is no cause for alarm
because the actual time difference amounts to fractions of a second over the course of
a year.
But what is weird is that, while scientists know that changes to the Earth’s inner and
outer layers, oceans, tides, and climate can affect how fast it spins, they don’t know
what’s driving the current haste.
Nobody’s perfect, not even our planet.
On average, Earth rotates on its axis every 24 hours or every 86,400 seconds.
But for various reasons, from the planet’s imperfect shape to its complicated interior,
every day is not exactly the same length as the day before.
What’s more, a day lasting exactly 24 hours is merely a standard we’ve come to expect
right now.
Earth's rotation is slowing down over the long term thanks to the Moon's pull on our
world.
Just a few hundred million years ago, for example, a day on Earth was only 22 hours
long.
In millennia to come, an average day on our planet will last far longer.
So, what gives with the shorter days of late, which buck the long-term trend?
One hypothesis that’s been floated so far has to do with the “Chandler wobble.”
Discovered in the 1800s, the phenomenon explains how the not-quite-perfectly-round Earth wobbles
ever so slightly, like a spinning top as it slows down.
Scientists observed that the wobble had mysteriously disappeared between 2017 and 2020, which could
have helped the Earth finish the day a bit faster.
Another idea is that climate change might affect the rotational speed of the planet.
When glaciers melt into the ocean, the shape of the Earth changes slightly, becoming flatter
at the poles and bulging at the equator.
But scientists say this effect can't explain why the planet suddenly would spin faster
because melting glaciers should have the opposite effect: The planet's moment of inertia would
increase, which would slow us down.
Other reports state that the likely culprit is more mundane.
One of the possibilities is the exchange of momentum between the Earth and the atmosphere.
The sum of those two is a constant, which means, for example, if the atmosphere slows
down, then the Earth speeds up.
Or conversely, if the atmosphere speeds up, then the Earth slows down.
The same thing can happen deep inside our world: It's possible for the deep core and
the mantle — the large layer that exists between the core and the surface — to move
at slightly different speeds.
There could be an exchange of angular momentum between the Earth's deep core and the mantle.
Both of those effects can either pump speed into the surface of the Earth or take the
speed out of the surface of the Earth.
But the dynamics of the atmosphere and the Earth’s interior are so complex that it’s
impossible, at least right now, to point to one of these factors as the sure cause of
the planet's brisk pace.
Nature does not always adhere to the rigidity of a clock or a calendar, and planetary timekeepers
are accustomed to making a few tweaks.
A leap year, for example, exists because we need an extra day every four years to keep
the 365-day calendar in sync with the Earth's revolution around the sun.
Because the day is getting longer over time as Earth's rotational speed slows down, timekeepers
toss in a leap second now and then to keep human time in step with the solar system.
With Earth accelerating, we face an unprecedented possibility: adding a "negative leap second."
In other words, if the planet continues to spin too fast, then by the end of the decade
clock masters may need to delete a full second.
For example, they might have the clocks skip from 23:59:58 on Dec. 31, 2029, to 00:00:00
on Jan. 1, 2030.
Scientists state that the possibility of a leap second five years ago was near impossible,
but over the last 2 years, there has been clear evidence that our planet is speeding
up.
And now, if that speed-up were to continue, we could need a negative leap second in about
seven years, maybe eight.
Outro If you liked this video, please consider taking
a look at this one which discusses what would happen if the Earth started spinning backward.
What do you think would happen if the Earth stopped spinning altogether?
Please share your thoughts in the comments section below.