# Earth's Spinning Speed

TaurusSteve
Apparently, right now the Earth is spinning at 1,000 mph! From https://www.space.com/33527-how-fast-is-earth-moving.html
"Earth's spin is constant, but the speed depends on what latitude you are located at. Here's an example. The circumference (distance around the largest part of the Earth) is roughly 24,898 miles (40,070 kilometers), according to NASA. (This area is also called the equator.) 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 (1,670 km/h). [How Fast Light Travel?]

You won't be moving quite as fast at other latitudes, however. If we move halfway up the globe to 45 degrees in latitude (either north or south), you calculate the speed by using the cosine (a trigonometric function) of the latitude. A good scientific calculator should have a cosine function available if you don't know how to calculate it. The cosine of 45 is 0.707, so the spin speed at 45 degrees is roughly 0.707 x 1037 = 733 mph (1,180 km/h). 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."

Can anyone explain all of this please? In layman's terms!

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Homework Helper
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Summary:: How fast is the Earth spinning and why don't we feel it?

Apparently, right now the Earth is spinning at 1,000 mph! From a search "We do not feel any of this motion because these speeds are constant. The spinning and orbital speeds of Earth stay the same so we do not feel any acceleration or deceleration. You can only feel motion if your speed changes."
Can anyone explain all of this please? In layman's terms!

You feel the force of gravity pulling you towards the Earth. If the Earth was not spinning the gravitational force would feel slighlty stronger, as some of the force is used to keep things on the surface spinning about the axis.

The required centripetal force is very small, so the variation in gravity from the pole to the equator is not very large.

In general, you are only subject to a force if you are accelerating. If you are in an aeroplane at 600km/h, you don't feel anything due to the speed of the plane. There are no forces on you to keep you moving at this speed.

Rotational motion, however, does involve acceleration. In this case towards the centre of the motion, which is what "centripetal" means.

sysprog and Ibix
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It's wrong (edit: the quote in the OP, I mean not PeroK, who posted just before I did).

Also, the Earth doesn't spin at 1000mph. Points on the equator travel at 1000mph compared to the center of the Earth, but the poles don't move at all - they just turn in place.

You feel effects of the Earth's spin - but it's just a part of the feeling of having weight. Gravity pulls you down. But things tend to fly off spinning objects, so away from the poles you the spin of the Earth tries to throw you off - i.e., upwards. This is the same effect that presses you against a car door when you turn a corner. If we could stop the Earth spinning, you'd find that you weighed more at the equator than you did before we stopped the spin. But since we can't stop the Earth, the effect of the spin is ever-present, just like gravity.

On a large scale, the spin of the Earth is quite noticeable. Artillery has, for quite some time now (World War II certainly), had to include corrections in the gun laying calculations to allow for the spin of the Earth. And it's the driving force behind hurricanes spinning.

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sysprog and PeroK
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By the way, OP, you should get into the habit of saying where you are quoting from, providing a link if possible. Some sources are good; some are just a bit oddly written; some are bad. If you say where you found something then we can take a look and see if you've missed some context or the source is just poor.

It's also really important for you to have an idea where your information comes from. If you keep track, you'll start to recognise for yourself what's good and what's bad - how to spot parallels between sources, and conversely contradictions and problems. If you don't know where you read something, though, you can't develop that skill.

sysprog and Nugatory
sysprog
What about the 23.5 (approximately, with respect to the solar orbital plane) degree tilt? (seasons are consequences of that, if the location is not at the equator or near one of the poles)? Does the spin include a gyroscopic effect that can be felt if one moves along a line of longitude or 'on the map' angularly? Can we at least just barely feel the tilt?

Mentor
What about the 23.5 (approximately, with respect to the solar orbital plane) degree tilt?
The orbital tilt affects where we see the sun in the sky, but has no bearing on the Earth as a spinning ball. There is the Coriolis effect which can be detected as one moves along lines of longitude, but that’s completely caused by the earth’s rotation about its axis, isn’t affected by the tilt of the axis,

DEvens, davenn, Ibix and 1 other person
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What about the 23.5 (approximately, with respect to the solar orbital plane) degree tilt? (seasons are consequences of that, if the location is not at the equator or near one of the poles)? Doesn't the spin include a gyroscopic effect that can be felt if one moves along a line of longitude or 'on the map' angularly? Can we at least just barely feel the tilt?
The axial spin is all but fixed with respect to the stars. The little bit of "wobble" or precession of the axis takes some 25,000 yrs to complete one cycle. So the Earth's tilt with respect to its orbit does not produce any significant effect that you could feel.

davenn, Ibix and sysprog
How fast is the Earth spinning and why don't we feel it?
You already have the numbers on how fast?

We don't feel it, because we don't have sensory organs that are sensitive enough to pick up the small effects.

davenn
Gold Member
The value of the free fall acceleration varies by only 0.034 m/s2 due to Earth's spin. This is a tiny fraction of the free fall acceleration itself, about 9.8 m/s2. Plus, you would have to travel from pole to equator to experience this tiny difference. It's too small to feel, but it's not too small to be measured.

vanhees71 and sysprog
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Summary:: How fast is the Earth spinning and why don't we feel it?

it takes an entire day to spin in place.
You know it completes one rotation in one day.
if you want to know it as rpm. then divide one revolution by the number of minutes in a day - very slow indeed.

The hour hand on a clock has an rpm twice as fast as that of the Earth's rotation rate.

vanhees71
Gold Member
You know it completes one rotation in one day.
We can't 'feel' that but the fact that the Earth bulges at the equator demonstrates that the Forces involved are actually significant but on other scales of time and mass.

vanhees71 and 256bits