# Jeopardy: Centrigugal Force Makes You Lighter? **URL:** \ **Category:** Factual Questions\ **Created:** [November 14, 2008, 2:35am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652 "2008-11-14T02:35:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [November 14, 2008, 2:35am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/1 "2008-11-14T02:35:30Z")
On Jeopardy the other day they answered at what lattitude you way the least. The question was 0 degrees. Alex said it was because of the earth’s rotation. Is that true or is it just because the equator is further from the center of the earth’s mass? ---
**Author:** ![Saltire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saltire/32/553_2.png) [@Saltire](https://boards.straightdope.com/u/Saltire)\ **Post date:** [November 14, 2008, 2:55am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/2 "2008-11-14T02:55:40Z")
Yeah, it’s true. The rotational velocity is highest there, so the tendency to be flung outward counteracts some of the gravity. That’s also why the whole planet is slightly thicker in the middle than at the poles. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 14, 2008, 2:57am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/3 "2008-11-14T02:57:51Z")
Another reason wy you weigh less at the equator is that you are farther away from the center of the Earth. It may be that you are farther from the center at the equator than on the summit of Everest. I’d have to check. ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [November 14, 2008, 3:02am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/4 "2008-11-14T03:02:07Z")
> [@sailor](#): > > Another reason wy you weigh less at the equator is that you are farther away from the center of the Earth. It may be that you are farther from the center at the equator than on the summit of Everest. I’d have to check. Yes, I realize that. The furthest point from the center of the earth is Mt. Chimborazo, in Ecuador. ETA: Oops, you were compraing the equator (presumably sea level) to Everest. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [November 14, 2008, 4:27am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/5 "2008-11-14T04:27:22Z")
At sea level, you weigh about half of one percent less at the equator than at the poles. Roughly 65% of the difference is accounted for by rotation (centrifugal force), the other 35% by the fact that you’re farther from the center of the earth at the equator (because the earth isn’t spherical). ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [November 14, 2008, 4:30am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/6 "2008-11-14T04:30:19Z")
I’ll just note that if I place a scale on the ground at sea level and then fly an airplane at 30,000ft over the scale, I won’t weigh anything at all. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [November 14, 2008, 4:51am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/7 "2008-11-14T04:51:07Z")
> [@Sage\_Rat](#): > > I’ll just note that if I place a scale on the ground at sea level and then fly an airplane at 30,000ft over the scale, I won’t weigh anything at all. If you hop over the scale at one inch, it won’t register anything either. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [November 14, 2008, 4:56am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/8 "2008-11-14T04:56:47Z")
> [@Exapno\_Mapcase](#): > > If you hop over the scale at one inch, it won’t register anything either. You get a similar effect if you just stand next to the scale. ---
**Author:** ![Bootis](https://avatars.discourse-cdn.com/v4/letter/b/e8c25b/32.png) [@Bootis](https://boards.straightdope.com/u/Bootis)\ **Post date:** [November 14, 2008, 5:06am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/9 "2008-11-14T05:06:13Z")
Would you weigh less at the peak of Chimborazo, which is 1 degree south, than at any point at 0 degrees latitude? ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [November 14, 2008, 5:36am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/10 "2008-11-14T05:36:45Z")
[quote=“1920s Style “Death Ray”, post:8, topic:472652”] You get a similar effect if you just stand next to the scale. [/QUOTE] Actually, you might rank as a negative weight if you are over or near the scale, since you have your own gravitational attraction that pulls up on the top. I’m not sure though, since even if you weren’t there, there would be air particles. ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [November 14, 2008, 9:07am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/11 "2008-11-14T09:07:50Z")
[quote=“1920s Style “Death Ray”, post:8, topic:472652”] You get a similar effect if you just stand next to the scale. [/QUOTE] Also if you zero the scale and then eat it. ---
**Author:** ![Melkor28](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@Melkor28](https://boards.straightdope.com/u/Melkor28)\ **Post date:** [November 14, 2008, 9:12am UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/12 "2008-11-14T09:12:59Z")
What if you put the scale on a treadmill? ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [November 14, 2008, 2:20pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/13 "2008-11-14T14:20:58Z")
Could we take the scale to the bottom of the Marianas Trench? ---
**Author:** ![glee](https://avatars.discourse-cdn.com/v4/letter/g/b5a626/32.png) [@glee](https://boards.straightdope.com/u/glee)\ **Post date:** [November 14, 2008, 2:22pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/14 "2008-11-14T14:22:46Z")
All these scale posts - something’s fishy! ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [November 14, 2008, 2:53pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/15 "2008-11-14T14:53:48Z")
No! There is no latitude at which a person weighs the least. Rotational forces are a red herring, because the earth is elastic. Think about it–the substance of the earth is affected by the rotational forces as well. Any would-be deviations of the net “weight force” from a sphere shape are filled in by the earth. For more detail, read about the [Geoid](http://en.wikipedia.org/wiki/Geoid). ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [November 14, 2008, 3:18pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/16 "2008-11-14T15:18:49Z")
> [@Pleonast](#): > > No! There is no latitude at which a person weighs the least. > > Rotational forces are a red herring, because the earth is elastic. Think about it–the substance of the earth is affected by the rotational forces as well. Any would-be deviations of the net “weight force” from a sphere shape are filled in by the earth. > > For more detail, read about the [Geoid](http://en.wikipedia.org/wiki/Geoid). From your link, “The geoid is that equipotential surface which would coincide exactly with the mean ocean surface of the Earth …” and “the geoid is by definition a surface to which the force of gravity is everywhere perpendicular.” but that isn’t the same as saying that people weigh the same everywhere on the geoid. The force of gravity is the gradient of the potential in the direction _perpendicular_ to the geoid. There is no reason for this to be constant everywhere on the geoid. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [November 14, 2008, 3:29pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/17 "2008-11-14T15:29:17Z")
I suppose I should provide a link. [Here you go](http://en.wikipedia.org/wiki/Earth%27s_gravity#Latitude). > [@Wikipedia](#): > > 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. ---
**Author:** ![Flander](https://avatars.discourse-cdn.com/v4/letter/f/8c91f0/32.png) [@Flander](https://boards.straightdope.com/u/Flander)\ **Post date:** [November 14, 2008, 4:16pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/18 "2008-11-14T16:16:45Z")
Are scale-er weapons for real? ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 14, 2008, 4:43pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/19 "2008-11-14T16:43:41Z")
> [@Smeghead](#): > > Could we take the scale to the bottom of the Marianas Trench? We already did. We’ve done it 0! times. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 14, 2008, 5:08pm UTC](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652/20 "2008-11-14T17:08:05Z")
To further understand why things don’t weigh the same everywhere on the geoid, consider a contour map. Two points on the same contour line are the same height, but they do not necessarily have the same slope. Height is analogous to potential, while slope is analogous to the strength of the gravitational field. [Next page](https://boards.straightdope.com/t/jeopardy-centrigugal-force-makes-you-lighter/472652.md?page=2)