Who wants to run out and try this? Stephen Fry uses a green laser and a few shouted obscenities from the cast of QI, and bursts three balloons with a laser. He then fails to burst the fourth, but fortunately there's a quick-fix with a magic marker.

This is a fun little segment that gives you a use for your leftover New Year's Eve balloons, which also makes you think twice about dismissing the claim that lasers can damage people's eyes. (I still doubt they can do much unless they're held right on the eye for a long period of time, but this does give me more respect for their abilities.)

When we look at white objects, we're seeing every wavelength of light jetting out at us in a confused tangle. When we look at a black surface, no light is coming out of the object, but light is still going into the object. (Okay, technically infrared and ultraviolet light, which we can't see, could be coming out. But there's still a lot of visible light that's being pumped in but not out.) Light is a form of energy, and if it's not coming out of the object as light, it's staying inside and warming the object as heat. In the demonstration above, Stephen Fry uses a laser on black balloons. The balloons have to be heating up, taxing the rubber. After just a second or two, they burst. A white balloon, which reflects the light, can vent the energy as light well enough to stay intact. How is this fixable? Just give the balloon a new coat of paint. A little work with a magic marker and the balloon absorbs the energy enough to burst.

Via The BBC and The Naked Scientists.