Bill Beaty 2003

Tie a piece of carrot to a mylar helium ba lloon. The weight of the carrot will drag it down. Nibble the carrot smaller. If you do it carefully, you can find the weight that cancels out the bouyancy. It will neither rise nor sink. Instead it will drift annoyingly around the room.

Years ago there was a helium tank at work, and I had a mylar "emergency blanket" in my car. I have an idea: giant floppy balloon! So I duct-taped the mylar into a roughly tetrahedral bag-shape about 80cm across and filled it with gas. It gave considerable lift, and it needed a considerable counterweight in order to attain neutral bouyancy. I tied a plastic cup full of water to the bag and adjusted the amount of water.

Brainstorm! Cover the whole thing with duct tape so the counterweight is distributed completely evenly. There would be no single weight at the bottom. That way it would behave like a boulder in free fall: it would remain in whatever orientation I put it in (rather than rotating to put the weight at the bottom.) And when gently spun (or after any collision) it should continue rotating around any axis for a long time.

So I started applying 20cm strips of black duct tape to the mylar bag, letting it stablize before applying the next strip to the (new) top location. That way it tells me how to distribute the duct-tape-mass evenly (I always put the next piece of tape directly across from the heaviest spot.) Then I applied smaller and smaller strips as I got closer to zero lift.

It worked great. I ended up with a huge, black, misshapen "boulder" which drifted around the room. If bumped, it would rotate end over end like an asteroid. I could grab it and fling it at somebody, and it would strike them with considerable impact (since it probably massed about half a kilogram not including the surrounding air mass it would entrain.) When thrown, it looked very unnatural, since we'd expect an object to fly in a parabolic trajectory. This one was completely straight. It also seemed very strange to encounter a large thing drifting around in the warehouse. After about half a day it settled to the floor as a bit of helium slowly escaped and increased the downwards net force so much that air convection could no longer waft it around the space. But I could then remove one or two tape strips from the bottom to restore it to "zero weight" again.

Next time: use white tape instead of black, then use an airbrush or spray paint to sketch in lots of lunar craters. Or perhaps print out some actual asteroid photos on 11x17 paper and plaster them all over the surface with #33 spray-on rubber cement (then add some extra helium to compensate.)

Someday I also want to make about fifty of these things and leave them in a big lab at work early in the morning before the victims arrive.

Anyone remember the Rocky & Bullwinkle episode about the old prospector and his mine where he was digging out negative-mass mineral called "upsi-daisium?"


Want books? Try searching

(try " science experiment project" too)
Created and maintained by Bill Beaty. Mail me at: .