[common_sense_seeker (OP)]

Is it not counter-intuitive to think that the Earth bulges at the equator due to it's rotation, yet the surface gravity (0.99732g) is less than if you were at the poles? Surely the fact that there is more mass between an object at the equator and the center of the Earth should be a factor in the explanation? But there is no mention of this in the textbook reason, which is not very convincing in my opinion. Does anyone agree that this is highly counter-intuitive?

[rosy]

Nope, makes perfect sense. Will try to find a diagram that explains it nicely when I get a minute.

[Bored chemist]

CSS,
You must think it's really counter intuitive. You have posted at least 3 times about it.
Actually it makes perfect sense, but you don't understand it.

[lyner]

Intuition is a really bad basis for Science, in any case. Work it out properly and it gives you the right answer. What more could you ask?

[LeeE]

Groan...........

[blakestyger]

CSS - Gravity calculation involves mass and distance.

[lyner]

CSS: But there is no mention of this in the textbook reason,

And which textbook have you been reading?
I wonder whether you have actually read a serious textbook or if you would have understood what it said. Any graduate level book will explain the matter perfectly adequately - you may need to be able to follow the integration, though.

[Bored chemist]

I think this is more "school playground" level than graduate level. Most kids understand that a merry go round throws you off because it spins. It seems css has failed to understand this (or he's a troll).

[turnipsock]

where are the sun and moon in this?

[common_sense_seeker (OP)]

Jeez, I willing to admit I've made a mistake if need be. I'll take a proper look at the standard solution in my own time. Just thinking out loud, that's all.

[Don_1]

Would centrifugal force play a part in this?

[common_sense_seeker (OP)]

I think this is more "school playground" level than graduate level. Most kids understand that a merry go round throws you off because it spins. It seems css has failed to understand this (or he's a troll).

It's not as clear cut as may think. The Moon isn't spinning about it's own axis in the same way that the Earth is. But it still has gravitational anomalies that aren't easy to explain. It also has flattening, and has a lower average equatorial surface gravity. Therefore it can't be due to centrifugal force.

If the Earth stopped spinning, would it suddenly change to more surface gravity at the equator, due to the loss of centrifugal force?

[common_sense_seeker (OP)]

The standard argument would suggest that it would due to loss of centrifugal force. Would surface gravity then be greater at the equator than at the poles? The Moon isn't spinning though and this still has a lower surface gravity, suggesting that this may be the case for the Earth as well. Could the answer be due to irregularities of the gravitational field of the core, which are fixed?

[BenV]

CSS - please don't start new topics to discuss subjects already under discussion in existing threads.  I've merged this one into the existing one.

Oh, and you've shown that you're not reading anyone's posts by yet again claiming that the moon doesn't spin.  The moon spins once per month, hence why it's always the same face towards us.  Place an apple on a table - orbit around that apple making sure you're facing it all the time - have you rotated - of course you have! 360 degrees!

People will be hard pushed to take you seriously when you repeatedly make very simple errors like that.

[Bored chemist]

"The Moon isn't spinning about it's own axis in the same way that the Earth is."
What, exactly, will it take to get it into your thick head that the moon is spinning?

"Jeez, I willing to admit I've made a mistake if need be. "
No, you are quite clearly not because you repeat the mistake, even after it has been pointed out to you.


"If the Earth stopped spinning, would it suddenly change to more surface gravity at the equator, due to the loss of centrifugal force?"
Yes; got a problem with that?

Of course there would be what politicians would decribe as "a period of adjustment" where everything came to a screeching halt from up to about a thousand miles an hour.

[niall]

OK, so, back to the point  []

Its all very well saying "go and do the integration" but not everyone can do it and its only one way of "explaining" it. I think the main issue you are having, css, is that

there is more mass between an object at the equator and the center of the Earth

. I'm not sure, but, the Earth's rotation causes the bulging round the middle of the Earth. This means that its stretched and there is not more mass as the Earth is less dense. There is exactly the same mass as anywhere else on the Earth's surface but you are further away from the middle so the field is less.

[turnipsock]

The moon has stopped 'spinning' in relation to the earth. The Earth will eventually stop spinning in relation to the sun. The earths spinning is going to be further slowed by all these wind farms and tidal energy things, is our PM unaware of Newton's laws?

[common_sense_seeker (OP)]

OK, so, back to the point  []

Its all very well saying "go and do the integration" but not everyone can do it and its only one way of "explaining" it. I think the main issue you are having, css, is that

there is more mass between an object at the equator and the center of the Earth

. I'm not sure, but, the Earth's rotation causes the bulging round the middle of the Earth. This means that its stretched and there is not more mass as the Earth is less dense. There is exactly the same mass as anywhere else on the Earth's surface but you are further away from the middle so the field is less.

Good point. Only less dense matter at the equatorial bulge could explain it. I'm dubious about this though. I think centrifugal force would tend to make less dense material migrate away from the equator, like bubbles in a washing machine on spin mode.

[lyner]

neill - that is a fair comment about not everone being able to do the integration. BUT, if you're going to challenge the existing theory you have to have some basis. Anyone who can't do the integration is not really in a position to challenge its results.
Most of this stuff is not a matter of opinion. The results at cutting edge of Science are open to opinion but 'informed' opinion is the only opinion which is worth anything. Some of the views you can read in these forums are incredibly arrogant; they discount, at a stroke, all the seriously good work which has been done 'at the coal face' by people with wisdom, knowledge and skills. None of these seem to be part of css's repertoire.

To prove my point, look at his last post. The bubbles (less dense) in a washing machine are actually forced into the middle and the water (the more dense) goes to the outside. His comment is just nonsense. (Has he ever actually been in a spinning washing machine to see?)
If you want a really graphic demonstration of this effect, take a helium-filled party balloon on a string into a car. When the car goes round a corner the balloon will lean INTO the bend for the same reason.

[Bored chemist]

OK css. The next mistake you have made and repeated (but claim to be willing to accept) is not to realise that the mass of the earth is exactly the same wherever you are.
So, to say the mass is more when you are at the equator is simply wrong. The whole thread doesn't make sense because the title is nonsense.
Also, as has been pointed out before, at the equator you are further away from most of that mass, so it has less efect and that reduces the net effect of gravity .
Again, as has also been pointed out, any child in the playground will tell you that things that are spinning tend to throw you off.
I don't understand how you could have been unaware of this (even before it was pointed out) but since you have now been told about it why don't you accept it?

The obvious conclusion is that you are either very stupid, trolling, or both.