[Alan McDougall (OP)]

Centrifugal force.

If one took a hypothetical rope, half the diameter of the earth or radius, and swung it around at a 1000 miles per hour (the same speed the earth revolves around the celestial poles it must generate a force similar to gravity.


If the earth did not revolve, there would be no centrifugal force and it would seem logical that due to the absence of this action, our weight must differ minutely on the surfaces of revolving and non-revolving earths.

Could the Naked Scientist come up with an answer please?

Regards

Alan

[Bored chemist]

There is a difference, but it's small.
Imagine that you are at the north pole, the earth's spin is just turning you about a vertical axis, so there's no centrifugal force. You still weigh pretty much the same there as at the equator.
Actually this is complicated by the fact that, at the poles, you are slightly nearer to the centre of the earth so that also makes you weigh more.

[RD]

In combination, the equatorial bulge and the effects of centrifugal force mean that sea-level gravitational acceleration increases from about 9.780 m·s-2 at the equator to about 9.832 m·s-2 at the poles, so an object will weigh about 0.5% more at the poles than at the equator.

http://en.wikipedia.org/wiki/Earth%27s_gravity

If the Earth stopped rotating I think the equatorial bulge would disappear and the Earth would become truly spherical,
 rather than an oblate-spheroid.

[Alan McDougall (OP)]

Bored Chemist and others

Thank you for your answers which cleared it up for me nicely.

There is a difference, but it's small.
Imagine that you are at the north pole, the earth's spin is just turning you about a vertical axis, so there's no centrifugal force. You still weigh pretty much the same there as at the equator.
Actually this is complicated by the fact that, at the poles, you are slightly nearer to the centre of the earth so that also makes you weigh more.

Just a point about your above quote, in another thread I asked how our weight would differ in a deep hole. The concensus was that one would weigh less. But you say at the poles we weight minutely more. This goes counter to the other explanation. RD calculation was an 0.5 difference which is considerable

Regards

Alan

[lyner]

This goes counter to the other explanation

No, the explanation is fine.
When you are down in a hole, there is some mass 'above you' or, more precisely, you are inside a thin shell of the Earth which has no net contribution to your weight - so you weigh less.
On the North Pole, all the mass is 'beneath your feet' and you are nearer the Centre of Mass -  so you will weigh a bit more.

[Alan McDougall (OP)]

Sophie,

Nice explanation I really understand it now, thanks

Alan