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Author Topic: Can gravity make you fat?  (Read 3798 times)

Offline Geezer

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Can gravity make you fat?
« on: 06/05/2010 07:24:44 »
I understand that gravity not only pulls you towards the Earth, but it also exerts a force that tends to pull "outwards" (when you are standing up of course). Does this mean that you'll be fatter when you are standing on the Earth than when you are standing on the Moon?

Also, can I use this as an answer when Mrs G asks,

  "Does this dress make me look fat?"


 

Offline JP

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Can gravity make you fat?
« Reply #1 on: 06/05/2010 10:43:41 »
Hmm... I would think it would pull you inwards, wouldn't it?  Every point on your body has a net gravitational force down towards the earth's center.  If you're really wide, I think this would tend to pull you down and squash you inwards at the same time.

 

Offline Geezer

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Can gravity make you fat?
« Reply #2 on: 06/05/2010 17:50:53 »
I think it might be different if you don't treat the Earth as a point mass.
 

Offline JP

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Can gravity make you fat?
« Reply #3 on: 07/05/2010 03:47:41 »
If you don't consider the earth as a uniform sphere, then yes, you might have side-to-side forces.  There's also forces from your legs on the earth (and the earth on your legs).  I think any of these effects are going to be minute in terms of squashing or fattening you for anything human-sized.
 

Offline Geezer

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Can gravity make you fat?
« Reply #4 on: 07/05/2010 05:29:32 »
If you don't consider the earth as a uniform sphere, then yes, you might have side-to-side forces.  There's also forces from your legs on the earth (and the earth on your legs).  I think any of these effects are going to be minute in terms of squashing or fattening you for anything human-sized.

Well, I just said fat. I didn't say how fat  ;D

I think it might still apply (ever so slightly) even with a uniform sphere. The elements of a person (standing straight up) that are "off the center line" will experience a very slight outward bias because the lateral forces will not quite sum to zero.

 
 

Offline JP

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Can gravity make you fat?
« Reply #5 on: 07/05/2010 10:16:12 »
Why would they get an outward force?  I might be missing it, but if every point on your body is being pulled (as a result of the net force) towards the earth's center, then your "edges" would seem to get pulled downward and towards your center.  Actually, if you're in free fall, this is what's called "spaghettification" (one of the greatest technical terms ever invented).  You tend to get stretched out along the axis pointing towards the center of the object and squashed inwards perpendicular to that.  In other words, you'd get tall and skinny. (See http://en.wikipedia.org/wiki/Spaghettification, for example.)

Of course, if you're not in free fall, then the fact that the earth is pushing back up (and radially outwards) on your feet gives you outward forces.  I think these end up beating out gravity. 

Quote
Also, can I use this as an answer when Mrs G asks,

  "Does this dress make me look fat?"
Yes, indeed!  I think experimental testing of this is in order.  When you recover from injuries sustained in the experiment, you'll have to let us know your findings.   ;D
 

Offline Geezer

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Can gravity make you fat?
« Reply #6 on: 07/05/2010 18:37:23 »
I think I better produce a diagram to 'splain what I'm on about. Stay tuned....
 

Offline JP

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Can gravity make you fat?
« Reply #7 on: 07/05/2010 19:03:24 »
I'm expecting a masterpiece.   :)
 

Offline gem

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Can gravity make you fat?
« Reply #8 on: 07/05/2010 23:47:25 »
I understand that gravity not only pulls you towards the Earth, but it also exerts a force that tends to pull "outwards"
Yes it causes partial cancellation of gravitational force.

Why would they get an outward force?  I might be missing it, but if every point on your body is being pulled (as a result of the net force) towards the earth's center,

I think it might be different if you don't treat the Earth as a point mass.

An important point to remember when considering earths force field is that the vector field in question does not exist.

It is only a map of the net vectors which give a direction, a particle in that location in that moment will take.

This only a mathematical tool sometimes called a Kuhnian construct.

The net vector part of the force field is the product of and linked inseparably to the lines of force one object exerts on another object or a collection of other objects from where they actually are. 

meaning that every particle that makes up a human body does indeed have a aspect of outward force in the direction of its interaction with all particles where ever they may be along the lines of force.

May be the shape of the average interaction is the shape of a cone so fortunately only a percentage of this force actually shows up on the bathroom scales,so we don't even have to measure it.


I think it might be different if you don't treat the Earth as a point mass.
Yes last time i looked it didn't appear to be one.

when asked any questions by my other half i have two stock answers 'yes dear' and 'no dear'    "Does this dress make me look fat?"  just better make sure your listening to the question.
 

Offline Geezer

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Can gravity make you fat?
« Reply #9 on: 08/05/2010 00:48:39 »
I'm expecting a masterpiece.   :)

You are going to have a long wait!

You're right. As your diagram explains, the forces tends to make you thinner, not fatter.
 

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Can gravity make you fat?
« Reply #9 on: 08/05/2010 00:48:39 »

 

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