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Guptar
8th Mar 2018, 07:11
If I weigh myself at the North Geographic Pole and am 100.00 kg.

If I then head south and my feet straddling the equator.

Will the centrifugal force that my body is subject to by moving much faster at the equator mean I will weight something less than 100.00kg, due to the rotation of the earth.

longer ron
8th Mar 2018, 07:23
I went from 210Lb (95kg) down to 150Lb (68kg) when I worked in Zimbabwe in the 80's but it was more due to the lack of decent chocolate/biccies/cakes etc rather than cos it was closer to the equator :)

Hokulea
8th Mar 2018, 07:28
Guptar, yes you will. About 0.35% loss of weight. Unfortunately, your mass stays the same...

Pontius Navigator
8th Mar 2018, 08:05
Isn't the reduction in weight a function of distance between the centres of Mass and not rotational speed?

Dont Hang Up
8th Mar 2018, 08:18
Yes, not only the effect of the Earth being fatter at the equator, but also the centripetal effect will both affect weight.

The total is about 0.5% of which approx. 0.35% is the centripetal effect.

The centripetal (or slingshot) effect on an airliner travelling East is around 0.8%. For Concorde at Mach 2 the effect would be 2%, which is enough to influence fuel calculations.

Hokulea
8th Mar 2018, 08:24
Mostly rotational speed (which is the 0.35% number I mentioned). There's about another 0.1% or so to add on for distance.

Beat me to it, DHU!

DaveReidUK
8th Mar 2018, 08:27
Yes, not only the effect of the Earth being fatter at the equator, but also the centripetal effect will both affect weight.

Not to mention the fact that you could take some clothes off at the Equator that you'd have been wearing at the North Pole. :O:O

Dont Hang Up
8th Mar 2018, 08:33
Not to mention the fact that you could take some clothes off at the Equator that you'd have been wearing at the North Pole. :O:O

By far the largest effect I suspect! :)

Tone
8th Mar 2018, 09:11
And let's not forget that we are living on an oblate spheroid. A body is significantly further away from the centre of mass at the equator.

DaveReidUK
8th Mar 2018, 09:13
And let's not forget that we are living on an oblate spheroid. A body is significantly further away from the centre of mass at the equator.

I think we might have already learned that.

Yes, not only the effect of the Earth being fatter at the equator

Pinky the pilot
8th Mar 2018, 09:17
In January of 1990 I was living in Waikerie, South Australia. (Around 34Deg S) and at the time I weighed 82kg. I then moved to Papua New Guinea. After about four months I was down to 68kg.:ooh:

Malaria tends to do things like that!:ugh::ugh:

PDR1
8th Mar 2018, 09:32
When I was in my mid 20s I moved about 3 miles south, and I lost a stone. It was a kidney stone, but in my book it still counts.

PDR

ORAC
8th Mar 2018, 09:39
You don’t really lose weight - it’s all just spin. Though I suppose it all comes down to your frame of reference.....

Saintsman
8th Mar 2018, 09:54
You are all talking rubbish. Your weight stays the same because the Earth is flat...

Hokulea
8th Mar 2018, 10:09
Orac - you don't understand the gravity of the situation.

redsnail
8th Mar 2018, 10:13
Hokulea, aww leave Orac alone, he's just a bit dense. :D

Loose rivets
8th Mar 2018, 12:24
Fifty year interest in gravity, and I still can't see why the inflow hypotheses can be rejected so readily.

In the late 80's I wrote to the three main magazines with the model and at least John Gribbin was kind enough to write to me - and indeed discuss it on the phone. But all to no avail.

Such a theory has to comply with General Relativity precisely and not conflict with with quantum theory where it is soundly established. But I'll tell you what, the inflow, or River models limit the closing of falling object to the escape velocity. Nothing else I can think of could achieve that in a constant set of fields.

Also, nothing in GR actually explains why mass bends spacetime. An inflow would shape an active set of fields along the geodesics that are established now.

There are so many mechanically pleasing aspects that fit but the mathematicians will present you with a big equation and say, there, that's how it works.

Even Einstein insisted that if something couldn't be explained in words, it had little merit. Can't remember the German.


Every living being is affected by gravity in one way or another, every day - yes, even those on the Space Station, yet no one knows how it works.

I want to know, and I have an increasing feeling I'm running out of time.

Fareastdriver
8th Mar 2018, 15:57
Every living being is affected by gravity in one way or another, every day - yes, even those on the Space Station, yet no one knows how it works.

If everybody on the Space Station stayed perfectly still after a time they would all end up huddled together. Should you park two redundant oil tankers in a Norwegian fiord without buffers they will migrate together and create an almost impossible task of separating them.

Gravity is the No1 effect on the Solar System and our lives.

Groundloop
8th Mar 2018, 16:04
Lot of people talking about weight but then quote figures using the kg, a unit of MASS. The unit of weight is the Newton.:ok:

WingNut60
8th Mar 2018, 16:18
If you really want to lose weight (and probably quite a bit of mass in the process) try digging your way down to the earth's core. The closer you get to the centre the less you will weigh.

Saintsman
8th Mar 2018, 16:29
If you really want to lose weight (and probably quite a bit of mass in the process) try digging your way down to the earth's core. The closer you get to the centre the less you will weigh.

That's because of all the effort involved. Exercise is one of the best ways to lose weight.

WingNut60
8th Mar 2018, 16:34
That's because of all the effort involved. Exercise is one of the best ways to lose weight.

Not just that. For all practical purposes, at the centre of the earth you will be weightless, the mass of the earth pulling on you equally from all directions.
Theoretically at least.

RAT 5
9th Mar 2018, 14:09
And let's not forget that we are living on an oblate spheroid. A body is significantly further away from the centre of mass at the equator.

If you really want to lose weight (and probably quite a bit of mass in the process) try digging your way down to the earth's core. The closer you get to the centre the less you will weigh.

These 2 statements seem in conflict?? I'd been shown an experiment where an increase in altitude, at the same spot, reduced the number shown on a weigh scale. The 1st statement might seem to agree with that, relative to the centre of our core; the 2nd one contradicts it.

Answers on a postcard to.......

PDR1
9th Mar 2018, 15:27
And let's not forget that we are living on an oblate spheroid. A body is significantly further away from the centre of mass at the equator.

If you really want to lose weight (and probably quite a bit of mass in the process) try digging your way down to the earth's core. The closer you get to the centre the less you will weigh.

These 2 statements seem in conflict?? I'd been shown an experiment where an increase in altitude, at the same spot, reduced the number shown on a weigh scale. The 1st statement might seem to agree with that, relative to the centre of our core; the 2nd one contradicts it.


No, it doesn't. "Weight" is the force you feel dure to the mutual gravitational attraction between you and the planet. If you go beneath the surface of the planet some of that attraction is pulling you "up" as well as "down". If you get to the actual centre of the planet then all of the force will be pulling you "upwards" in all directions and you'd be "weightless", but you wouldn't feel it because you'd have been vaporised by the molten magma long before you got there...

PDR

longer ron
9th Mar 2018, 16:42
Always nice to have a Mass Debate ! :)

ZOOKER
9th Mar 2018, 16:49
Tone,

Point of order,

We actually live on a 'Geoid'.

I suspect that Guptar would also weigh less when The Sun and Moon are overhead, especially during a 'Total Solar Eclipse'.

Even more so if the equatorial eclipse occurred at the zenith, with The Moon at perigee and The Earth simultaneously at perihelion.

Mr Optimistic
9th Mar 2018, 17:11
As far as I know, you don't ' feel' your weight. You feel the reaction from what is supporting you. No matter, you'll still be just as fat :)

Ancient Observer
9th Mar 2018, 17:47
Unless you are a Welsh Rugby player.

Tone
9th Mar 2018, 18:28
Zooker
An oblate spheroid is a surface of revolution obtained by rotating an ellipse about its minor axis (Hilbert and Cohn-Vossen 1999) I thought that's what we lived on - oh well.

I put some comparitive figures into the spreadsheets I used in times gone by and found that a strapping Eskimo who tipped the scales at 100kg at the north pole would be a mere 99.312kg on top of Everest. Obviously well worth the effort.

ZOOKER
9th Mar 2018, 18:54
Tone, it's not far off, but the Earth departs from a true oblate spheroid in several places...Not by great amounts admittedly. I think The Indian Ocean is one of them?

The term 'Geoid' doesn't really help much, because it really just means 'Earth-shaped'.

Many U.K. Aerodrome charts now have a reference to 'Geoid Undulation', not sure what it means though, or how it affects a/c operations.

ORAC
9th Mar 2018, 19:47
WGS84 (https://en.wikipedia.org/wiki/World_Geodetic_System) did the mapping for the gravitational variations.

Geoid is the shape the earth would take up under only the influence of its own gravitational and rotation. But of course, ignoring the sun and other planets, it’s not - the earth and moon are gravitationally coupled and the centre moves as the two perform the dance of the heavens.....

https://en.wikipedia.org/wiki/Barycenter

ZOOKER
9th Mar 2018, 20:43
ORAC,

If I remember it correctly, the 'Earth-Moon System' rotates around its common centre of gravity, called the 'Barycentre', which, (due to the distance between the 2 bodies, and their mass difference), lies below The Earth's surface.

Mr Optimistic
9th Mar 2018, 21:16
Indeed so. Important if you need to understand tides.