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Ideal for
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updated 11|19|2002

Lift any two JUGS at a time to transport people to the Moon or Mars for a brief brain-expanding instant

Make your set in less than 1 hour for less than $5

by Peter Kokh

You will need:

  • (3) Jugs with handles: I bought (3) 48 oz. jugs of Bleach (cheaper and more durable than half-gallon jugs of milk or jugs of liquid detergent and you can always use the bleach). I paid $1.29 each for my local grocery store's generic brand.
  • Some Styrofoam Peanuts: if you haven't saved any from packages you have received, perhaps someone you know has a supply. As a last resort, you can buy them from package mailing stores such as Mail Boxes, Etc. of from Packaging Materials suppliers. A cubic foot, more than you will need, will cost between $1 and $2. I happened to have a supply.
  • Water

Simple Instructions:

  • Earth Jug: As is (or you can replace the bleach with water)
  • Moon Jug:
    • Empty contents into spare container
    • rinse
    • fill with styrofoam peanuts
    • then add only 1 cup (8 ounces) of water (1/6th of 48 oz.)
  • Mars Jug:
    • Empty contents into spare container
    • rinse
    • fill with styrofoam peanuts
    • then add only 2 1/2 cups (18 oz) of water (3/8ths of 48 oz.)

    NOTE: The styrofoam peanuts help distribute the water evenly and prevent telltale "sloshing" - I had thought of adding Knox unflavored gelatin to gel the water / styrofoam peanuts mixture, but this proves to be unnecessary.

    NOTE: Neither the weight of the plastic jug, nor of the styrofoam peanuts are factored in, being dismissed as practically negligible. Making the exact adjustment would not materially affect the sensing of different gravities.

Some Alternatives:

  • Jugs:
    • Option: milk and cooking oil containers also have handles, but may be less sturdy
    • Option: easy grip neck milk or oil bottles
    • Option: clear bottles or jugs give the opportunity to color code the fill material to the extent practical
    • Option: 3 of any other kind of container that is securely closable and easy to grip and lift. For example, at some hardware stores, you can purchase never-used empty gallon paint cans with handles.
    • Choose the cheapest option if you have to, otherwise allow yourself to do some imagineering! Durability through constant handling and ease of lifting are the primary qualities needed.
  • Water:
    • Option: dry sand (higher density gives all three jugs more weight), or some other type of non-liquid pourable fill
    • Option: small size aquarium gravel, which comes in colors if you are using clear containers (blue for Earth, rust for Mars, gray for the Moon)
    • Rule: just use the same fill for all three jugs, in proportions specified.
  • Instructions:
    • If you select 64 oz containers (half-gallon), you will need 11 oz fill for the Moon jug, 24 oz. for the Mars Jug
    • If you select 128 oz (1 gallon) containers, you will need 21 oz fill for the Moon Jug, 48 oz. for the Mars Jug
    • If using fine dry sand or other non-liquid pourable fill, still fill the Moon and Mars jugs with styrofoam peanuts first. If the sand is dry, you should be able to sift it in the interstices. Again the purpose is to distribute the mass evenly.
    • If you are using aquarium gravel, it may take some shaking to get the required amount of fill in between the interstices of the styrofoam peanuts, in order to distribute the weight. Some trial and error experimentation may be necessary.

Replace labels with ones printed out from this page following the suggestions for type of paper and for label placement.

Label Information: These labels give the visitor all the pertinent information. No accompanying flyer is necessary. Earth is bigger than the Moon and Mars and so has the greatest gravity. The Moon is the smallest of the three and so has the least. You can tell those who ask that gravity is a function of density (indirectly of mass) and surface area (a function of the diameter).

Jug Caps may be color coded for convenience. I left the Earth Jug cap blue. I used a rust primer on the cap for the Mars Jug. I used a graytone fleck spray I happened to have on hand for the Moon Jug cap. I clearcoated the painted caps.

Instructions for painting the jugs - optional

Companion color flyer (JugFlyerBlank.pdf) ready to print and with blank space at the bottom for you to put your (or your chapter's) contact information

Box: Find or make an easy to handle cardoard box to store and transport your set.

Why Gravity Jugs? Creation of these Gravity Jugs follows on four and a half years of experience with the "Gravity Bricks" sets we have been making for chapters around the country. Over two dozen being in circulation at the time of creation of this page. They are a powerful draw to any space information booth or table. Pick up any two and you instantly "get" the difference in gravity. Because all three "bricks" are the same shape and size, the eye tells the brain to expect that they will weigh the same, and that it will take the same muscular effort to lift each. But one is unexpectedly much easier to lift than the other. Your eyes light up! You smile! For an instant you have been transported to the Moon and/or Mars and have experienced something special and different about those worlds in comparison to Earth. The overwhelming common response is - "cool"

Every space society chapter engaged in public outreach can benefit by having such a set. But making them is time consuming and costly. The Gravity Jugs is an eureka idea that came to me as the solution for a cheap do-it-yourself substitute for the Gravity Bricks, and especially ideal for those with a minimum of do-it-yourself workshop skills.

Now there is no excuse for every chapter having its own set. Every Science teacher too!

Photo of our original Jug Set
L>R Earth, Mars, Moon

Peter Kokh -

Uploaded September 20, 2002

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