# The Naked Scientists Forum

### Author Topic: Do you weight less when standing under the moon?  (Read 4023 times)

#### EvilHomer15

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##### Do you weight less when standing under the moon?
« on: 12/07/2011 18:51:31 »
Hallo naked scientists.

I have read in a book the other day, that water is globally affected by the moon and sun. Something to do with mass gravitational influence.
The movement of the moon causes tides in oceans, and generally all water on this planet. I found this to be interesting.

My question is of a similar science:
How does it affect water, and elements in other states of matter in general (solid and gas)?
Will a human being weight less when he is standing underneath the moon, compared to when he is not?

EvilHomer15

#### syhprum

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##### Do you weight less when standing under the moon?
« Reply #1 on: 12/07/2011 21:35:23 »
Taking into account the relative distance to the Moon compered to the distance to the centre of the Earth and the relative mass of the Moon compared to that of the Earth and applying Newtons inverse square law I would expect a reduction of 0.000346% of your weight
« Last Edit: 12/07/2011 21:39:35 by syhprum »

#### syhprum

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##### Do you weight less when standing under the moon?
« Reply #2 on: 13/07/2011 09:15:56 »
I have been working on an idea to harvest energy from this variation in weight a large mass could be supported on springs that would rise when the Moon was overhead and could yield power as it sinks when the moon is the other side of the Earth.
Would any correspondents skilled in arithmetic care to help me put some figures into the design of such a machine to compute the power output

#### Don_1

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##### Do you weight less when standing under the moon?
« Reply #3 on: 14/07/2011 08:40:59 »
........ I would expect a reduction of 0.000346% of your weight

Not really enough to get you any stars at the next Weightwatchers inquisition then eh?

#### Don_1

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##### Do you weight less when standing under the moon?
« Reply #4 on: 14/07/2011 08:51:39 »

Would any correspondents skilled in arithmetic care to help me put some figures into the design of such a machine to compute the power output

I think it is not so much the mathematics which would give you problems as the production of such high precision springs and maintaining that high precision long enough to make the venture worthwhile.

Would it not be a better plan to utilise the system which nature has already provided? ie. Tidal power.

#### graham.d

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##### Do you weight less when standing under the moon?
« Reply #5 on: 14/07/2011 14:35:43 »
A pedantic point, Syphrum:- The sprung weight would be higher when the moon was on the other side as well as when it was overhead, just like the high tides. So twice per day. Please send me a proportion of the fortune you make with this invention as I think I just doubled the power output :-)
« Last Edit: 14/07/2011 16:57:40 by graham.d »

#### Geezer

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##### Do you weight less when standing under the moon?
« Reply #6 on: 14/07/2011 18:22:54 »
I have been working on an idea to harvest energy from this variation in weight a large mass could be supported on springs that would rise when the Moon was overhead and could yield power as it sinks when the moon is the other side of the Earth.
Would any correspondents skilled in arithmetic care to help me put some figures into the design of such a machine to compute the power output

You better not do that. If you do, you'll slow the Moon down and it will crash into the Earth. (Or maybe it will  drift away into the solar system  )

#### CliffordK

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##### Do you weight less when standing under the moon?
« Reply #7 on: 14/07/2011 20:54:27 »
I have been working on an idea to harvest energy from this variation in weight a large mass could be supported on springs that would rise when the Moon was overhead and could yield power as it sinks when the moon is the other side of the Earth.
It sounds like a tide generator to me.  I.E.  Rather than making your own "mass", utilize the oceans that are a few miles deep and thousands of miles wide.

Your generator would have to have a lot of mass on a very fine balance.  I would ask whether a large ship's draft would change with the moon.  With any luck, the ship's draft might change less than an inch due to the moon's gravitational pull, but if it was located in the ocean, the elevation of the ship would change by several feet due to the tides.

I have troubles envisioning a generator that is based on a massive pull on a very short stroke, and only two strokes a day, but in theory it would be possible.  Perhaps you could use the changes in elevation to run a water pump feeding a turbine.

#### Geezer

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##### Do you weight less when standing under the moon?
« Reply #8 on: 14/07/2011 22:07:50 »
Of course, you could always invent a hydroelectric generator that tapped into tidal energy instead.
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(Thinking)
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Wait a minute, didn't somebody do that already?

#### The Naked Scientists Forum

##### Do you weight less when standing under the moon?
« Reply #8 on: 14/07/2011 22:07:50 »