How would you go about building a Dyson Sphere ?
494439
With an orbit of where earth is, 149,600,000 km, that's a surface area of 7.12383E+15 km², i think...\n\nYou can fit approx. 11,700 earths in a single ring around the sun, so you can imagine the amount of materials needed for a dyson sphere is pretty massive! (although Jupiter is more than a 1000 times more massive than the earth!)\n\nI think you might even need to destroy whole solar systems to get the materials required, but the planets, moons & asteriod belt would be a good place to start, assuming you need specific materials like metals especially.\n\nDon't even think about the cost!
1059935
Build a cloud chamber and show everyone cosmic rays whizzing through them. Instructions below (its easy).
7169
You could make a cloud chamber. It's a chamber that's saturated with alcohol vapor so when a cosmic ray or radioactive particle enters the chamber it leaves a trail of mist like when a plane leaves a vapor trail. It does use dry ice and isopropyl alcohol though. It's kind of complicated but would be worth it in the end. You might even win depending on the competition.
421484
This website may help, not only does it have a picture, but it has step by step:)\nhttp://www.enchantedlearning.com/crafts/astronomy/solarsystemmodel/\nI would use the foam balls instead of the tag paper. If you need to make it to scale this website might also help:\nhttp://www.exploratorium.edu/ronh/solar_system/index.html
105012
You can build all (or most of) the platonic and archimedaic solids using Origami.\n\nYou can also buid conic sections (hyperboles, parabola, ellypse and circle) by repeatedly folding a piece of paper along the tangents, point by point, using fundamental properties of each one. (= you get them as the envelope of their tangents).
18888
You could make a cloud chamber. It's a chamber that's saturated with alcohol vapor so when a cosmic ray or radioactive particle enters the chamber it leaves a trail of mist like when a plane leaves a vapor trail. It does use dry ice and isopropyl alcohol though. It's kind of complicated but would be worth it in the end.
978352
A model volcano is always a hit. Or a model of the solar system. For the latter, just string some colored balls on the interior of a shoe box painted black. Pretty simple.
494425
You can buy kits at places like Hobby Lobby, but you can do way better on your own. I used the information in the links below to make a scale model where I used a basket ball for the Sun and various pin heads and acorns for the planets. The first link below is an on line calculator that will tell you how big to make the planets and how far apart to place them if you just enter the size you want to make the Sun. I bet you are surprised at how small and far apart the planets really are!
7127
here's a site with pics that might give you some ideas:\n\n\nhttp://www.physics.usyd.edu.au/competition/comp1998/comp98.html
671843
to make an ideal one you would look at the fluid dynamics equations.\n\nHowever ideal ones are very thin at the end and would break so to make real ones you would need some engineering know-how. So that it is strong enough and generates enough lift for your purpose.
1148382
To do it accurately you may need a PhD. \nOtherwise, build a trough with an uneven bottom.  Then build a ramp to the trough.  On the top of the ramp have a bucket that is constantly being filled with water from a fish tank pump.  Make the bucket so that when it is filled to a certain level it tips and pours down the ramp into the trough.
322239
Try Cube: http://www.cubeengine.com
247976
I painted Styrofoam balls of different sizes for my two year old daughter.  The only moon I included was ours and I attached it to the earth with a toothpick. (You could use those little crafty-puff-ball-thingies for the moons of other planets.)  I made the rings of the ringed planets with poster board that I painted and cut into a circle.  I also attached those with toothpicks. (She's two, she's not picky.)\nI used metal florist wire to make hooks that I stuck directly into the balls and attatched them directly to the ceiling with thumbtacks.\n\nHope this helps.  A 7 yr old would definitely enjoy the painting, etc. . .  Good luck!\n\n**The above mentioned technique with the ballons and paper strips is called paper mache.**
715337
I had to do the same thing.\n\nHere's what I did. it was real easy.\n\nGo to a craft store, get a plastic see through empty ball that you can take apart in halves. Then buy clear candle GEL. Get a wire for orbitals and beads for electrons.\n\nWhat you do is melt the candle gel in a pan until it is liquid, let it cool a little and pour it into half the ball, put your "orbitals" with the electrons in place on the gel, put the second half of the ball on, tape it shut and some tape and string to hang it up.\n\nIt takes about 5 minutes to make and is visible from all angles.
719052
Very very simple. Take a baloon ( white or any light color), blow it to its complete size. Then, tie it at the end so that the air does not go out of the baloon. Then paint on it as the planet should be. Par example, Paint with blue and brown for the planet Earth. If you want to hang it, use a wire.
809750
Ratio of what?\nSurface area?\nVolume?\n\nI will go with volume.\n\nassume radius of sphere is = 1\n\nsphere = 4/3pi\ncylinder = 2pi\ncone = 2/3 pi\n\neat the pi's (get rid of them) and multiply what's left by 1.5\n\nSphere:Cylinder:Cone = 2:3:1\n\nI hope that helps
667922
Either use volumes of revolution or compare cross sections of the sphere and a cylinder with a couple of cones removed. The latter is how Archimedes did it.