# Why don't we feel Earth spinning?

Staff member

#### Majik

I would argue that the statement in the article: "Our planet is rotating much faster than that" is incorrect.

Rotation is measured in angular velocity (so degrees per hour, radians per second, revolutions per minute, etc. )

If we use the commonly-used units of rpm, earth is rotating at 0.000694 RPM which is far slower than any roundabout would rotate at whilst being used. It's twice as slow as the hour hand on a clock. Most roundabouts would rotate several times per minute which is over 10,000 times faster than the earth's rotation.

Now, if you take tangential velocity as your measurement, that would certainly be more on the earth (at least at most places): the tangential velocity at the equator is over 1,000 mph. But that's a measurement of tangential speed/velocity, not strictly of "rotation".

Cheers,

Keith

ClimberT8

#### ClimberT8

I would argue that the statement in the article: "Our planet is rotating much faster than that" is incorrect.

Rotation is measured in angular velocity (so degrees per hour, radians per second, revolutions per minute, etc. )

If we use the commonly-used units of rpm, earth is rotating at 0.000694 RPM which is far slower than any roundabout would rotate at whilst being used. It's twice as slow as the hour hand on a clock. Most roundabouts would rotate several times per minute which is over 10,000 times faster than the earth's rotation.

Now, if you take tangential velocity as your measurement, that would certainly be more on the earth (at least at most places): the tangential velocity at the equator is over 1,000 mph. But that's a measurement of tangential speed/velocity, not strictly of "rotation".

Cheers,

Keith
Thank you for pointing out the ill-definedness of "faster": angular vs tangential velocity, as well as frame of reference issues for rectilinear motion.

#### ClimberT8

I'm not sure what the writer means by "feel". You can certainly  see Earth's rotation, easiest at sunset or sunrise when the horizon is near enough to the sun, or by looking at a shadow near noon time or at a beam spot from a hole.
You can sense it thermally, obviously. And if you've experienced a cyclone or anti cyclone you've certainly "felt" the earth's rotation. You can "touch" the earth's rotation via tides.
So what is lacking is not the feeling, it is the attribution to a casual model.

#### VeryCurious

I do not agree to the comparision between smooth motion in car and spinning of Earth. Earth's spinning is a circular motion, which is an accelerated motion, and we should feel acceleration. The spinning produces slightly less effective weight on Equator than on Pole. The reason we don't feel the spinning is because it is just 0.35 % of our weight at maximum. At larger scale, the wind systems do feel the spinning, and the cyclonic storms spin clockwise in Southern hemisphere and opposite in Northern, because the Earth spins.

Majik

#### Majik

I do not agree to the comparision between smooth motion in car and spinning of Earth. Earth's spinning is a circular motion, which is an accelerated motion, and we should feel acceleration.
This is fair IMO.

As you point out, the spinning results in a decrease in effective weight near the equator. And we do sense weight: if we wear a heavy overcoat we can feel it. If we are on a fairground ride that drops, we feel lighter.

But, as you also point out, the difference is very small. It's basically the difference in weight you would feel if you drank a large glass of water.

Cheers,

Keith

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