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    I was listening to radio 2 factoids earlier and one claimed that you would weigh less during a full moon then at any other lunar stage.

    Im no physicist but pondered on why for a while...

    If this is indeed true does anyone know why? The only explanation I could think of (which may well be wrong) would be that this with the moon directly in front of us and the sun directly be behind, their gravitational pull would be at its greatest and weakest on the earth for each respectively. With tidal effects and the differences in distance from the sun during our year surely this effect would not be noticable though?

    Can anyone throw anything out there?
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    if you transform into a werewolf then you usually weigh about 20% more.
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    Surely it'd be at new moon, when the sun and moon are aligned? (leaving out issues of order of magnitude compared to other effects like latitude.)
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    but werewolfs always look so scraggy and underfed?

    and yeaa ignore my suggestion... ive just realised that would be a lunar eclipse, not a full moon :s

    i recon its codswallop to be honest
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    Something about that theory doesn't sound right. The size of the moon doesnt change with each lunar stage, it just changes its position in relation to where the sun is meaning that there is less/more light reflected off of the moons surface.

    So yeah, it sounds like, as you said, a load of codswallop.
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    Well it depends. You would weigh less when the Moon is directly above you, as the Moon's gravity pulls you up a little bit. It would be like standing on some scales holding a helium balloon, you would weigh slightly less than usual.

    But I don't think a full Moon is necessarily when the Moon is directly above you.
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    I'm not convinced if gravitational fields cancel each other out...
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    (Original post by ashy)
    I'm not convinced if gravitational fields cancel each other out...
    Sure they do. They're vector fields and so cancel.
    Another way to think of it is that gravity is basically a force, and forces certainly cancel - so why wouldn't gravity:

    fake edit: source - http://sci.tech-archive.net/Archive/.../msg01491.html
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    (Original post by M_E_X)
    Sure they do. They're vector fields and so cancel.
    Another way to think of it is that gravity is basically a force, and forces certainly cancel - so why wouldn't gravity:

    fake edit: source - http://sci.tech-archive.net/Archive/.../msg01491.html
    I understand that, I'm just considering it from curving space point of view. I understand how the force above you will detract from the force below you, producing a different resultant, but somehow I doubt it's that simple with gravity. I would be as though you're being acted on by two separate forces rather than one resultant. You wouldn't be lighter, you'd be pulled apart.

    Granted this doesn't explain Lagrange points, so I guess it is that simple :tongue:
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    (Original post by ashy)
    I understand that, I'm just considering it from curving space point of view. I understand how the force above you will detract from the force below you, producing a different resultant, but somehow I doubt it's that simple with gravity. I would be as though you're being acted on by two separate forces rather than one resultant. You wouldn't be lighter, you'd be pulled apart.

    Granted this doesn't explain Lagrange points, so I guess it is that simple :tongue:
    But your "weight" is just the amount of force pulling you towards Earth. If there is a force pulling you in the opposite direction, producing a different resultant (as you say in your post) then surely that's equal to less weight.

    Anyway! Some of the stuff you talk about (curving space and whatnot) is way above my understanding. Where / what year do you study at?
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    (Original post by M_E_X)
    But your "weight" is just the amount of force pulling you towards Earth. If there is a force pulling you in the opposite direction, producing a different resultant (as you say in your post) then surely that's equal to less weight.

    Anyway! Some of the stuff you talk about (curving space and whatnot) is way above my understanding. Where / what year do you study at?
    Yes I agree in principle I just think there's more to the story when it comes to gravity as it's a force field rather than a force as we'd understand it in that framework.

    I have a physics degree from Imperial College I haven't studied any of the "curving space stuff" as such, that's just me connecting the dots from various pop science books I've read :tongue: I would have liked to have done GR, but I'm no theorist :tongue:
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    (Original post by Scipio90)
    Surely it'd be at new moon, when the sun and moon are aligned? (leaving out issues of order of magnitude compared to other effects like latitude.)

    A minor point but a new moon is when the Earth casts a shadow on to the moon, i.e. its between the sun and moon.

    For maximum pull away from the Earth's surface you'd be needing a solar eclipse, i.e. both the sun and moon pulling you in the same direction, creating a bigger pull instead of working against each other at new moon.
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    (Original post by div curl F = 0)
    A minor point but a new moon is when the Earth casts a shadow on to the moon, i.e. its between the sun and moon.

    For maximum pull away from the Earth's surface you'd be needing a solar eclipse, i.e. both the sun and moon pulling you in the same direction, creating a bigger pull instead of working against each other at new moon.
    Isn't when the Earth casts a shadow on the Moon a Lunar eclipse? A new Moon is when you can't see the Moon at all, which is about when the Moon is aligned with the Sun but it is only exact during a Solar eclipse. So that would be the best time to weigh less because of gravity.
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    (Original post by div curl F = 0)
    A minor point but a new moon is when the Earth casts a shadow on to the moon, i.e. its between the sun and moon.

    For maximum pull away from the Earth's surface you'd be needing a solar eclipse, i.e. both the sun and moon pulling you in the same direction, creating a bigger pull instead of working against each other at new moon.
    Not really sure what you're saying here, when the earth casts a shadow on the moon it's a lunar eclipse, which occurs at full moon, not a new moon, which is when a solar eclipse occurs.
 
 
 
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