Yes I was going to comment on the dry ice bomb, but wanted to make sure no one wrote about it yet. You referenced it, but I wanted to explain it in detail in the hopes that, since people are going to try it regardless of if they know how, at least they will know what’s going to happen, haha.

NOTE TO TIM: If you think this is stupid, I’m fine with you vetoing this comment, but I figured an educated person trying this was better than an uneducated one.

Like Jason said, it can be dangerous!! So, if you just can’t get over the urge to see it in person and try one, first make sure you are OUTSIDE, and in a very open area with no other people, animals, or anything else of value nearby.

Chop up some dry ice so that it is in small enough pieces to fit through the opening of a 2 liter bottle. Take the 2 liter bottle, and fill it a little over half, to 2/3 full of warm water. Do not use hot water, since that will make it pressurize too fast! You’ll get the same affect with warm water anyway. You take the funnel and place it in the bottle. Pour only about 1/4 cup dry ice in the funnel, and as soon as it is all in the bottle, seal it with the cap as fast as you can, and throw it as far away from you as you can, without throwing it high in the air, so it doesn’t hit the ground hard.

Wait 10 seconds or less, and it will build up enough pressure to blow the bottle open :)

Oh, and if this is illegal in North Dakota, then no I have never tried this :D

Paul

In regards to your dry ice video, this appears to be some form of the leidenfrost effect hXXp://en.wikipedia.org/wiki/Leidenfrost_effect –

In short, it’s similar to the way water beads up on a hot skillet by floating on vapors.

In this case, the vibration seems to be occuring because of gas escaping by way of temperature exchange. The coin heats up the dry ice creating CO2 (gas). The gas expands and escapes from behind the coin pushing the opposite side of the coin against the other wall of the CO2(solid). Rinse and repeat until the coin has cooled.

The leidenfrost effect has also been suggested as the way firewalkers walk on hot coals.

I’m not a physicist, but my science teacher showed us a video in 8th grade illustrating this concept. Hope this lends a little clarity to the vibrating coin puzzle.

Best Regards!
-michale

I’m sorry I missed your trip to Sydney all those months ago.