Thunder and lightning are created using a Van de Graaff generator!
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: And this is a Van de Graaff generator! And one thing that's fun to do is to use it to make really big sparks!
The Van de Graaff generator dumps electrons onto this dome. The more electrons there are, the more 'uncomfortable' they become. Now, remember, electrons carry a negative electrical charge and like charges repel. The electrons try to spread out as best as they can.
Steve: This dome is attached to the earth through this wire and the earth is a whole lot larger than either one of these domes, so it has a lot more room for them to spread around. Eventually, so many electrons will gather on this dome that they'll be able to jump through the air to this dome. Once they're here, they'll flow through the wire and into the ground, where they can spread out as much as they like.
Van de Graaff: Snap! Snap! Snap!
Joanna: The sparks that you see are essentially baby lightning and the sounds that you hear are essentially baby thunder. The sparks are hotter than the surface of the sun and they heat the air as they pass though it. The sudden expansion of this heated air causes a shock wave that we hear as thunder.
Steve: Now, in a real thunderstorm, you see the lightning...
...and then you hear the thunder. But, now, we're seeing and hearing it at the same time. Do you know why?
Joanna: Light travels a lot faster than sound. Sound travels about one mile in five seconds. And, while that's pretty fast, light travels about a million miles in the same amount of time.
Steve: So, while the light from the spark reaches our eyes before the sound reaches our ears, we're so close to it, we can't really tell the difference. If lightning were to come through the ceiling and strike the table right in front of us, we'd see that and hear it at the same time, too.
And then, we'd probably die.
So, let's hope that doesn't happen!
Joanna: Thanks for watching! I hope you'll join us again soon for another experiment!
Steve: Sparks in the dark?
Joanna: Sparks in the dark!
Van de Graaff: Snap! Snap! Snap! Snap!
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