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Can a lead balloon fly? Can tooth fillings pick up radio stations? Each week millions watch and , aka the , test urban legends on their Discovery Channel TV show. Peter Aldhous joined them on set in San Francisco to find out how these special-effects wizards became standard-bearers for TV science

Which of the myths you鈥檝e worked on have given you the most satisfaction?

Jamie Hyneman: A favourite is when we investigated whether a can fly. Think about what it takes to build a bag out of lead that鈥檚 0.007 of an inch (0.2 millimetres) thick, weighs 28 pounds and is 14 feet across. What we had to go through to where it actually floated with helium was just thrilling.

Adam Savage: Another time we wanted to know whether a penny dropped from the Empire State Building will kill you. We鈥檇 done a piece to camera talking about the mathematics of its terminal velocity, and then I came up with the idea of creating a wind tunnel with a different velocity at the bottom than at the top. A tumbling penny should move up and down in the wind tunnel, and it did. That is the kind of thing I really enjoy.

What do you hope the viewers will learn from the show?

AS: A fan emailed me recently to say: 鈥淚 heard a myth that the Eiffel Tower weighs less than the column of air that describes its extent.鈥� Ten minutes later I had it all plotted out and it鈥檚 absolutely true. I even accounted for the lowering of the density of the air at the top of the tower. If someone watches our show and realises that this is a simple thing to do, then that鈥檚 what we鈥檙e trying to communicate.

JH: We鈥檙e not scientists by training. But if I were to say one thing, it would be that using your head is actually a lot of fun. I don鈥檛 normally associate TV with a whole lot of cerebral activity, and people tend to think of using your head as some kind of work, but we鈥檙e just having a ball.

鈥淚 don鈥檛 normally associate TV with a whole lot of cerebral activity鈥�

There鈥檚 an element of danger in your tests. Have there been any close calls?

JH: There have, and we generally don鈥檛 talk about them. The most frequent safety hazard involves moving heavy blast shields that have broken fingers and caused herniated discs.

AS: We have had a few wake-up calls in the course of shooting this show, but we鈥檝e taken them incredibly seriously. After testing 600 myths in 2000 separate experiments 鈥� a lot of them being set up in lethal situations, close enough for us to watch them 鈥� you do start to feel like your number鈥檚 up. So we take that very, very seriously.

How would you describe your different approaches to testing a myth?

AS: Mostly, we will play devil鈥檚 advocate about any point that the other brings up. Each of us has a vision in our head, and to get into each other鈥檚 heads involves a process we call鈥� arguing.

How do you go from an initial idea to the segments that we see on TV?

AS: Some ideas come from the fans, some come from our producers, and a good proportion come from me and Jamie.

JH: For us it鈥檚 all about satisfying our curiosity. Often it鈥檚 some kind of paradox we want to investigate, or just an excuse for us to build something that鈥檚 crazy. I think the rest is just being methodical. We have to tell a story with a beginning, middle and end. It turns out that the scientific method and the classic narrative structure work really well together.

You often have sample sizes of one or two, but science is all about replication. How do you respond to that criticism?

JH: People simply wouldn鈥檛 watch it if we were just repeating things over and over again. We do them as compactly as we can to keep up the energy level and flow. We intend these shows to be thought-provoking, not definitive.

AS: I think the part of the scientific enterprise that we do illuminate is that it鈥檚 a messy, creative process that changes your whole understanding. We鈥檒l spend half an episode finding that we鈥檙e asking the wrong question.

Your fans certainly like !

JH: If they鈥檝e criticised us that means they鈥檝e actually thought about what we鈥檙e doing, and that鈥檚 the biggest compliment that we could possibly get.

AS: We鈥檝e done a dozen episodes at least where we鈥檝e gone back and tackled stories that we鈥檝e done before, where either we didn鈥檛 tackle it with the right equipment or we didn鈥檛 have enough data, or we got new information.

When you are testing your own reactions, might you bias your results because you have expectations about the outcome?

AS: That鈥檚 a good point and makes me think that we should demonstrate experimental bias on the show. It was an issue when we investigated 鈥渂eer goggles鈥�: whether drinking alcohol can make people seem more attractive. I spent a long time with a friend of mine who鈥檚 a statistician to try and remove as much of the bias as possible.

Do scientists contact you about your tests ?

JH: One that comes to mind was from in Tennessee. We鈥檇 blown up an airplane as part of a story about whether shooting a gun inside a pressurised airplane would make it explode. The people at Oak Ridge had been trying to get funding to do exactly that kind of test, so they wanted access to the footage.

Are there any myths where the underlying scientific phenomenon remains a mystery?

JH: was based on a that had somebody igniting a bucket of thermite on top of ice, and there was an explosion. The speculation was that the heat caused the water in the ice to decompose into hydrogen and oxygen, which exploded. The problem as I saw it was the volume of hydrogen and oxygen that would have to be created instantaneously, and then ignite, seemed to be too large. So I speculated that the steam reaction, possibly coupling with some decomposition of the water, aerosolised the thermite that then flashed.

AS: I鈥檝e also been told that it鈥檚 what happens when you make water move directly from a solid to a gas.

It sounds like something that readers of our might answer.

AS: We鈥檝e been getting all sorts of explanations from all over the web, but we don鈥檛 know which is right. So perhaps you guys can help us out.

Know the explanation? Let us know!

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