Earth Spin

[portocat]

How fast does the earth spin?  It must be going pretty fast if we don't fall off, and if it is going fast, how come we dont feel dizzy?

[jake-the-peg]

I make it about 16-17 thousand kilometers an hour at the equator.

But it's the revolutions a second that makes you dizzy we do less than a thousanth of 1 rpm

[JudgeJ]

Are you sure you didn't get the decimal point wrong, jake?

I make it about 1,700 kph (Earths circumference = 40,000km (approx.) divided by 24 (hours).

By the way, portocat, we don't fall off because the earth's gravity attracts us to its surface. The centrifugal force of the earth's rotation (the same force that throws your laundry to the side of the spin drier) actually offsets gravity, albeit by a tiny amount.

[mibn2cweus]

Around 1.00273790926 times each day at the north pole.  Just seems slower cause were goin round the sun wonct yearly.

[mibn2cweus]

Right about now the Earth would be spinnin bout 53615kph round the sun.  Wouldn't recommend no cus words tward our maker just yet.

[secretsquiz]

the speed we're moving depends on whereabouts in the world you are.

the closer you are to the equatorm,

[portocat]

do you think it will ever stop spinning?

[secretsquiz]

oops! my finger slipped - damn keyboard!

anyway...

the closer you are to the equator, the faster you'll be moving. london moves at approximately 998mph (or so bill bryson tells me!)

[jake-the-peg]

whoops yes my bad.

The dizzy thing is interesting because it becomes a problem if you're looking at atificial gravity in a space station as in the 2001 film.

As I recall some of the work done on this showed that a rotating space station producing the same gravity as on earth would need to be over a kilometer in diameter in order to stop people from feeling nausious.

[JudgeJ]

It is unlikely to stop, portocat, but it is slowing down.

I gave an answer to an earlier question on AB which explains:

The earth’s period of rotation is actually slowing down. There is evidence to suggest that the day was as short as 10 hours when the earth was first formed.

This slowing down is mainly caused by the “tidal” effect that the moon has upon the Earth’s rotation. The tidal effect caused by the moon’s gravitational “pull” causes the earth to “bulge” towards the moon. This happens to all celestial bodies but can be seen quite clearly on Earth by the twice daily movement of the sea known as the “tides”.

This daily distortion of the Earth’s shape is causing a gradual loss of its angular momentum (i.e. the energy it has by virtue of its spinning) and it is gradually, but very definitely, slowing down.

Eventually the Earth will become “tidally locked” with the moon and the same point on earth will always face the moon. This is because the Earth will take the same time to rotate once on its axis as the moon takes to revolve around the Earth.

This has already happened to the moon. The tidal effect of the earth upon the moon was far greater because the Earth is about 100 times more massive than the moon, so Tidal Locking of the moon occurred much sooner. The moon takes 28 days to revolve around the Earth and the same time to rotate once on its axis. As a result we always see the same face of the moon facing the Earth and it was not until the 1960’s when a spacecraft first revolved around the moon that photographs of the far side were taken.

[portocat]

this is very interesting.  Have you heard of the poles on the earth swapping?  I have heard theories that this caused the ice age and the demise of the dinosaurs.  Is there any proof re this, and do the poles have anything to do with the spinning?

[CT]

The poles on the sun swap due to its rotation, or more accurately, the differential rates of spin. The nearer the sun's equator, the faster it rotates. It is the difference in speed of rotation that causes the magnetic field to get twisted round and eventually flip. This occurs every 11 years. The earth is more complicated because of its different structure.