Freethought & Rationalism Archive

lunachick · 05-04-2003, 11:09 PM

I know nothing!

"How do you know you are standing on the equator?"

This is the question being asked of me by my neighbour who is in middle school. I can't help him.

I know about water flowing down a drain either clockwise or anti-clockwise according to which side of the equator you are on - although I've also heard that's not necessarily true?? <shrug>

But what happens when you are directly on the equator? Does your watch stop - or your compass start spinning? Or do you simply perspire all the more profusely in the equatorial heat? I haven't a clue.

Any help would be appreciated!

many thanks.

Aquila ka Hecate · 05-04-2003, 11:23 PM

HI lunachick,

Forget the rotation of water down the drain-the centifugal force exists, but it's far too small to notice in these circumstances.

Myself, I'd notice I was on the equator by the position of the sun at midday-right overhead(zenith) at the equinoxes, and a measurable,definite angle from the zenith at other times of the year.

Assuming you knew which day of the year it was, you could figure out pretty accurately that you were on or near the equator.

There's also the case of gravitational attraction being offset by the centripetal force more on the equator, so you'd weigh less for the same mass than at the poles.

These are just a couple of ideas off the top of my head-actually I'm only about 26 degrees from the equator myself.

Terri

lunachick · 05-04-2003, 11:33 PM

Hi, Terri.

The boy is only 11, so I think the equinoxes might be a bit over his head (so to speak).

I'll deliver him the weight difference answer for his science project.

Many thanks!

If anyone has any other ways of knowing if you're on the equator - keep 'em coming!

Cheers.

enigma555 · 05-05-2003, 12:41 AM

If you're on the equator, assuming there is little to no light, you can see both the north and south poles in the stellar spheres.

elwoodblues · 05-05-2003, 01:18 AM

I think the idea of weight and centripetal force is your best bet. It's reasonably intuitive, and it'd always work, no matter the season or time of day. "Imagine you're standing on the top of a spinning ball. It doesn't really throw you off. A little ways down the side, you're being spun off a little. But right on the equator, it's throwing you off the most." Try to have a globe handy when you're doing it; makes it easier to visualize.

SULPHUR · 05-05-2003, 03:32 AM

You will have to explain the earth is not round ,then bring gravitational forces into the explanation and then comes the difference between mass and weight. have fun luna

lunachick · 05-05-2003, 04:05 AM

Hey, thanks, guys.

I'll do my best to explain it to him!

...oh, shit.

Hayden · 05-05-2003, 04:34 AM

Um, it's really hot?

HR

Salmon of Doubt · 05-05-2003, 05:32 AM

I saw somewhere that said that directly on the equator water doesn't spin at all, it just goes straight down. Don't know if that's true though, as I can't remember where I saw it!

Aquila ka Hecate · 05-05-2003, 05:50 AM

SoD,

(!)
Yes, No, Not Really:

Bad Science and Coriolis Effect

explains it better than I can.

The gist is, the effect is real, but so slight that you'd need quite special equipment to make sure it wasn't due to some other, non-latitudinal cause.

Sulphur,

The weight effect is not due primarily to the oblateness of the earth, but to the centripetal force which acts in a direction opposing the gravitational.
The spin removes some of the weight.

Me Again.

05-04-2003, 11:09 PM	#1
lunachick Veteran Member Join Date: Sep 2002 Location: NZ Posts: 7,895	School kids question about the equator? Please help! I know nothing! "How do you know you are standing on the equator?" This is the question being asked of me by my neighbour who is in middle school. I can't help him. I know about water flowing down a drain either clockwise or anti-clockwise according to which side of the equator you are on - although I've also heard that's not necessarily true?? <shrug> But what happens when you are directly on the equator? Does your watch stop - or your compass start spinning? Or do you simply perspire all the more profusely in the equatorial heat? I haven't a clue. Any help would be appreciated! many thanks.

05-05-2003, 03:32 AM	#6
SULPHUR Senior Member Join Date: Nov 2002 Location: hobart,tasmania Posts: 551	and if he asks why You will have to explain the earth is not round ,then bring gravitational forces into the explanation and then comes the difference between mass and weight. have fun luna

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05-04-2003, 11:23 PM	#2
Aquila ka Hecate Regular Member Join Date: Nov 2001 Location: Luna City Posts: 379	HI lunachick, Forget the rotation of water down the drain-the centifugal force exists, but it's far too small to notice in these circumstances. Myself, I'd notice I was on the equator by the position of the sun at midday-right overhead(zenith) at the equinoxes, and a measurable,definite angle from the zenith at other times of the year. Assuming you knew which day of the year it was, you could figure out pretty accurately that you were on or near the equator. There's also the case of gravitational attraction being offset by the centripetal force more on the equator, so you'd weigh less for the same mass than at the poles. These are just a couple of ideas off the top of my head-actually I'm only about 26 degrees from the equator myself. Terri

05-04-2003, 11:33 PM	#3
lunachick Veteran Member Join Date: Sep 2002 Location: NZ Posts: 7,895	Hi, Terri. The boy is only 11, so I think the equinoxes might be a bit over his head (so to speak). I'll deliver him the weight difference answer for his science project. Many thanks! If anyone has any other ways of knowing if you're on the equator - keep 'em coming! Cheers.

05-05-2003, 12:41 AM	#4
enigma555 Regular Member Join Date: May 2002 Location: Washington, DC Posts: 282	If you're on the equator, assuming there is little to no light, you can see both the north and south poles in the stellar spheres.

05-05-2003, 01:18 AM	#5
elwoodblues Veteran Member Join Date: Mar 2001 Location: Dunmanifestin, Discworld Posts: 4,836	I think the idea of weight and centripetal force is your best bet. It's reasonably intuitive, and it'd always work, no matter the season or time of day. "Imagine you're standing on the top of a spinning ball. It doesn't really throw you off. A little ways down the side, you're being spun off a little. But right on the equator, it's throwing you off the most." Try to have a globe handy when you're doing it; makes it easier to visualize.

05-05-2003, 04:05 AM	#7
lunachick Veteran Member Join Date: Sep 2002 Location: NZ Posts: 7,895	Hey, thanks, guys. I'll do my best to explain it to him! ...oh, shit.

05-05-2003, 04:34 AM	#8
Hayden Senior Member Join Date: May 2002 Location: Wellington, New Zealand Posts: 712	Um, it's really hot? HR

05-05-2003, 05:32 AM	#9
Salmon of Doubt Regular Member Join Date: Feb 2003 Location: UK Posts: 150	I saw somewhere that said that directly on the equator water doesn't spin at all, it just goes straight down. Don't know if that's true though, as I can't remember where I saw it!

05-05-2003, 05:50 AM	#10
Aquila ka Hecate Regular Member Join Date: Nov 2001 Location: Luna City Posts: 379	SoD, (!) Yes, No, Not Really: Bad Science and Coriolis Effect explains it better than I can. The gist is, the effect is real, but so slight that you'd need quite special equipment to make sure it wasn't due to some other, non-latitudinal cause. Sulphur, The weight effect is not due primarily to the oblateness of the earth, but to the centripetal force which acts in a direction opposing the gravitational. The spin removes some of the weight. Me Again.

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