Strikingly Little Is Known About Lightning
IRA FLATOW, host:
You're listening to SCIENCE FRIDAY from NPR. I'm Ira Flatow.
Up next this hour, you know, you've all seen that picture of Ben Franklin and his famous kite experiment, the kite and a key doing the colonial equivalent of field research on lightning. Well, now, since that was over 200 years ago, you might think that scientists have learned all there is to know about lightning. And, of course, you'd be wrong.
According to my next guest, we know surprisingly little about these common natural phenomena. We don't even know what causes it to happen. Wow, lightning is hard to study because, you know, you don't know where it's going to hit, so you can't set up your equipment to catch it in action. Maybe you go to the top of the Empire State Building or something like that. But that's not pretty practical to that. But there is a workaround, scientists at Florida Institute of Technology have figured out how to make lightning strike in a specific spot so that they can better study it.
Joseph R. Dwyer is professor of physics and space science at the Florida Institute of Technology in Melbourne, Florida. He's with us today. And you can learn about more of his work with lightning by going to sciencefriday.com, check our video pick of the week there and see the lightning that's happening. And we'll talk about that a little bit later. Welcome to SCIENCE FRIDAY.
Professor JOSEPH DWYER (Physics and Space Science, Florida Institute of Technology): Thanks, Ira. Glad to be here.
FLATOW: So you can get lighting to strike twice.
Prof. DWYER: Yeah. I mean, lightning frequently hits the same thing twice. The Empire State Building, as you mentioned, is usually hit about 20 times a year, in fact.
FLATOW: Now, why, why don't we know so much about lightning? I mean, we've been studying it - certainly, even before Ben Franklin, people are wondering about it, but he was a pretty good scientist. Why does it - what is it so hard to know about what - why lightning occurs?
Prof. DWYER: Well, you've mentioned, part of the problem, even though we get a lot of lightning in some places, like here in Florida, we don't know exactly when or where it's going to strike, and so we don't know where to point our instrument. Another problem is a lot of the action happens up inside the thunder clouds. That's where lightning gets started. A lot of the interesting physics is going on up there. And it's very difficult to make measurements inside the thunderstorm. They're big dangerous places.
FLATOW: Mm-hmm. And so you've developed a way of making your own lightning.
Prof. DWYER: Well, I didn't develop it myself, but we use it working with colleagues at the University of Florida. We have small rockets that we have a spool of copper wire in the bottom. And when there's a thunderstorm overhead, which in Florida, we don't have to wait too long for that in a sign.
And we have a thunderstorm overhead. We know lightning is going to strike some place. And so, if it's going to strike any way, why not strike here now? Launch this rocket - as it flies up in the air, wire comes off the end of the spool, and we create maybe a 200-yard-long lightning rod very quickly. And that's usually enough to cause lightning, so we can bring it down to where we want it and we can make measurements.
FLATOW: You're basically doing the exact the same thing that Ben Franklin did.
Prof. DWYER: Yeah. It's a similar idea. You do an experiment and then you do measurements, and you learn things about lightning. And Benjamin Franklin established that lightning was an electrical phenomenon. It turns out there is a lot we don't know, even in the 250 years since this kite experiment.
FLATOW: Like what?
Dr. DWYER: Well, all the questions about lightning that we don't know. They're all very basic ones, like how does it get started, how does it move? For example, it's a real mystery how lightning gets started up inside the thunderstorms. There never seems to be enough charge up there and big-enough electric field to actually make a spark. Yeah, here we see lightning all the time.
Once it gets started, we don't know how it moved - can move. Air is a really good insulator and yet lightning can forge a path through tens of miles, through air. And we don't know exactly how it does that.
FLATOW: Mm-hmm. You mean, it's not just the rain particles banging against each other that created separation of charge and a spark.
Prof. DWYER: Well, yes. I mean, we do know a few things about how thunderstorms charge. It is the ice and the water particles bumping into each other that separates the charge. We do know that that is going on inside the thunderstorms. But ones that happened, the electric field never seemed to be big enough.
Dr. DWYER: We see the charge is separated, but never seems to be enough to make a spark.
FLATOW: Mm-hmm. 1-800-989-8255. Mark in South St. Paul, Min. Hi. Welcome to Science Friday.
MARK (Caller): Hi. First off, Newton's Apple wasn't the same without you.
FLATOW: Thank you very much.
(Soundbite of laughter)
FLATOW: You must be very old.
(Soundbite of laughter)
MARK: Well, I'm no loss for years.
FLATOW: Thank you.
MARK: The question I have is that many years ago, I heard the fact that -excuse me - one lightning bolt, it's, well, 30,000 volts to jump one inch. And it's said 10 miles for bolt could be one bolt could be enough to power the city of New York for a couple of years. The question I have is, anyone ever thought of the idea of possibly trying to capture the lightning to - if we could store electricity to power our cities?
FLATOW: Yeah, that's what Franklin was trying to do too, wasn't he?
MARK: True. Then the other question, I'm wondering is brought up as a - does there any idea about the blue sprites that the astronauts have seen with thunderstorms?
FLATOW: Let me look - thanks for calling. Let me get some answers to your question.
Prof. DWYER: Yeah, right.
FLATOW: Joe, what do you think?
Prof. DWYER: Okay. Well, first, using lightning as a power source. I really wished that that were true, but unfortunately it doesnt quite work. Even though there's a lot of power generated by lightning, the currents can be maybe 30,000 amps. The voltages could be hundreds and millions of volts. The power is not delivered over a long period of time. Lightning is very fast. And so if you sort of captured all the lightning you possibly could and got all the power that you possibly could over a fairly large area, you'll still only be able to power 100-watt light bulb on average. So it's not really a practical energy source.
FLATOW: Mm-hmm. Is it true that lightning, the strike that you see, actually starts at the ground and goes up to the cloud?
Prof. DWYER: Some lightning can start on - from objects near the ground, tall towers - Empire State Building is an example. But most lightning, the vast majority, starts up inside the thunderstorm and then propagates down to the ground. As it gets close to the ground, there are sparks that raise up immediate for the last, say, 50 yards.
FLATOW: Mm-hmm. And why does it branch like it does? It almost seems like it takes steps to get down to...
Prof. DWYER: Well, that's exactly correct. Lightning doesn't travel in sort of a straight uniform way. It will move forward maybe 50 yards, pause, almost like it runs out of steam, and then suddenly step forward or leap forward another 50 yards or so. And then it - as it leaps forward, sometimes it branches. This process is called the stepping process. It's the step leader that allows lightning to propagate. And one of the mysteries is why does lightning step? We actually don't know.
FLATOW: Mm-hmm. And I would imagine something that is that powerful must give off more than just light rays, maybe...
Prof. DWYER: Yes, that's right.
FLATOW: ...(unintelligible) other things?
Prof. DWYER: Yeah, so it's interesting. So, just an example of the state of the field. Back in 2001, we discovered that lightning emits X-rays. Nobody knew this before. We did work on this with the University of Florida, Florida Tech, and also college at New Mexico Tech did work on this. And it's an amazing fact that, you know, like I said, 250 years since Franklin's kite experiment, it took us that long to find out that X-rays come from lightning. I mean, that's pretty basic.
FLATOW: That sounds dangerous. I mean, X-rays?
Prof. DWYER: Well...
FLATOW: How strong are those X-rays?
Prof. DWYER: Well, the X-rays that are emitted by lightning near the ground, which - that's what would affect most people if they were near lightning, they're scientifically interesting but the doses are not significant enough to hurt anybody. In fact, you'd probably get a bigger dose from X-rays when they take you to the hospital and X-rayed your head rather than from the lightning.
FLATOW: Mm-hmm. I just got a couple of more questions in. Corey(ph) from Columbus. Hi, Corey.
COREY (Caller): Hi. Yeah, I wanted to see what we know about the relationship between lightning and the Earth's magnetic field and what we know about lightning on the other planets in the solar system?
FLATOW: All right. Thanks for the call.
Prof. DWYER: Okay. As far as I know there's almost no relationship between lightning and magnetic field, in terms of the magnetic field affecting the lightning. Now, lightning can disturb the magnetic field up in space, in the magnetosphere, and it can actually cause radiation, electrons to precipitate down on the Earth sort of by jiggling the magnetic field. So lightning affects the field a little bit, but magnetic field doesn't affect the lightning as far was we can tell.
Prof. DWYER: Regarding the lightning in other planets, we do know that lightning is common on Jupiter, Saturn. Apparently, there's lightning on Venus and possibly some of the other planets as well.
FLATOW: When I was in Antarctica many decades ago, people were - would communicate with ham radio and they would listen. And they would hear little -they said were little sprites of lightning that were coming down that would make little noises that they're propagated down the magnetic field.
Prof. DWYER: Mm-hmm.
FLATOW: Is that how it works? It'll - just follows the magnetic field of the Earth (unintelligible)?
Prof. DWYER: Yeah, there are some waves that can follow the field lines and come up one side and down the other, yes. So that is one way that lightning can affect, for example, the magnetosphere.
FLATOW: Susan(ph) in Pennsylvania. Hi, Susan.
SUSAN (Caller): Hi, there.
FLATOW: Hi, there.
SUSAN: My question for you was - and I've always heard that myth that you should not be talking on a phone or in the shower when there's a thunderstorm because you could get struck.
Prof. DWYER: Well, that is absolutely correct. You know, if you're - first of all, being inside the house is a good thing if there's a thunderstorm. If you can get inside, that's a really good idea. But once you're inside doesn't mean you're perfectly safe. You really don't want to have an electrical connection between you and the outside world. You don't want to provide a path for the lightning to get you.
And if you're talking on a phone that has a wire between the - your ear and the outside world, well, that can be bad.
FLATOW: What about the shower?
Prof. DWYER: Yeah. I mean, there are - the plumbing, for example - lightning -even though maybe the metal pipes don't necessarily connect to the outside world directly - maybe there's plastic pipes in the middle. But, lightning can come in, say, on the phone line and then spark to the pipes, and then the pipes can spark to you.
Prof. DWYER: So not a good idea to be near any pipes. You don't want to be washing the dishes or taking a bath. And you just simply don't want to be messing around with electrical equipment.
FLATOW: There you go, Susan, you are right.
SUSAN: Wow, thank you.
FLATOW: You're welcome. Have a good weekend.
SUSAN: You too.
FLATOW: 1-800-989-8255. Paul(ph) in Smithtown, Long Island. Hi, Paul.
PAUL (Caller): Hi, good afternoon.
FLATOW: Hi, there.
PAUL: Great show.
FLATOW: Thank you.
PAUL: I was just curious - and I'd like an example. How hot is a strike or a bolt of lightning? Have they measured it?
PAUL: And what...
FLATOW: The Johnny Carson question...
PAUL: ...kind of damage can it give?
FLATOW: ...how hot is it.
PAUL: How hot?
Prof. DWYER: Well, that I can tell you. You know, we know a lot about what lightning does but not how it does it. And so here's something that we know that lightning does. We know that the hottest part of the lightning is called the return stroke - can heat the air up to about 50,000 degrees Fahrenheit. That's five times the surface temperature of the sun.
PAUL: Okay. And when it hits the earth, does it reduce in BTUs or whatever measurement you guys use?
Prof. DWYER: Well, I mean, the energy does dissipate into whatever it hits. I mean, it could - it can, you know, melt objects. It can blow up trees, you know? The energy goes some place.
FLATOW: What - let's go down to the basics. If lightning is electricity, I don't see electricity, right? Electricity is invisible. What am I actually seeing then?
Prof. DWYER: Well, just like you don't see electricity but you see the effects of electricity...
Prof. DWYER: ...like an incandescent light bulb. You see the electricity flowing through the tungsten film. In heating it up, it gets hot and then it glows. That's exactly what lightning does. It - a lot of currents go in through air, which is so hot it's now become a conductor, and it heats up the air. That's what emits the light. I mean, it's hotter than the sun. It's emitting the light just like the sun is emitting light. And of course, hot air expands very quickly, and that rapid expansion of the air makes the thunder we hear.
FLATOW: Hmm. Talking with Joe Dwyer about lightning this hour on SCIENCE FRIDAY from NPR. I'm Ira Flatow.
People, you know, people love to talk about this stuff. And it's fascinating to hear that you know so little about it after all these years.
Prof. DWYER: Yeah, it's a fun topic for a scientist.
FLATOW: Yeah. How long have you been studying it?
Prof. DWYER: For about 10 years now. I've been a professional physicist for about 16 years, but the - I changed fields 10 years ago and started studying lightning and I never had so much fun.
(Soundbite of laughter)
FLATOW: Let's go to Barbara(ph) in Rogue River, Oregon. Hi, Barbara.
BARBARA (Caller): Hello.
FLATOW: Hey there.
BARBARA: Hey, I had an experience happen to me, and I don't really know why. Maybe you could explain it. But we had an electrical storm, lots of dark clouds, lots of wind, thunder and lightning. And when it kind of calmed down, I had looked outside and noticed that my little table outside with the aluminum umbrella has - well, the umbrella had detached and had blown off, so I walked out there. And I started dragging it back towards the table. And then after about 10 feet, I saw this bright light - I mean, it's just flashing, this white light. And I dropped the umbrella and ran back inside. And there was no lightning, there was no thunder but it was very strange.
Prof. DWYER: So the light was coming from the umbrella?
BARBARA: You know, it was around there. It was very bright (unintelligible)...
Prof. DWYER: Okay. Well, I'm not sure exactly what happened, but one scenario is that there were still large electric fields from the nearby thunderstorms and there was coronal emission coming off of the umbrella. It's basically getting ready to spark. And if that's the case, actually, you're lucky you weren't hurt because you could've...
BARBARA: I know.
(Soundbite of laughter)
Prof. DWYER: You could've been struck by lightning.
FLATOW: You dodged that bolt. Don't try that again, Barbara, okay?
BARBARA: I will. I will.
FLATOW: All right. Thanks for calling. What is heat lightning? You hear it but you don't see it, or you see little flashes and then there's no storm anywhere?
Prof. DWYER: Yeah, a lot of people think that it's somehow, this lightning, is just made from the atmosphere, from the heat, but that's not true. It's actually just normal lightning that's occurring in thunderstorms that are too far away to hear the thunder. So, you know, you have a thunderstorm maybe 20 miles away, you can still see the lightning, but thunder can't travel that far. Especially, heat lightning refers to inter-cloud lightning, lightning that lights up the clouds. So it's just normal lightning - you're just seeing it from a different perspective.
FLATOW: Let me see if I can get a quick question from Mark(ph) in Kansas City. Hi, Mark.
MARK (Caller): Hello, good afternoon. I have a home which sits on a hill in the country, just outside of town, and I'm actually more concerned out here about lightning than I am tornadoes. And I've investigated the possibility of putting a lightning rod on my house. And I was just wondering if you're expert had an opinion about whether or not they were effective.
FLATOW: Another Ben Franklin out there.
Prof. DWYER: Okay, well, you're smart to be more afraid of lightning than tornadoes because actually lightning kills more people in the United States, on average, than tornadoes. And about lightning rods - yes, absolutely. Lightning rods are a good idea. They will protect your home or that will protect structures. And nothing is 100 percent, but they are a significant improvement.
FLATOW: Do they draw the electricity out of the atmosphere before it forms a lightning bolt? Like, suck it off beforehand, so that the lightning bolt doesn't strike?
Prof. DWYER: Actually, the way it works is that as the lightning is coming down, it's getting ready to strike something on the ground. And if it's going to strike the area - your house or the area around it, there's nothing you really can do to divert that. But what you can do is that it's going to strike your house anyway, you can give it a safe place to strike. And the idea is the lightning rods, really tall and pointing. It's kind of like, you know, when you walk up to a door know after walking across the carpet, your finger comes to the door knob, you get a spark. You know, your finger is long and pointy. And so the - you get the spark that readies us up to catch the lightning coming of the lightning rod and not off your chimney, say.
FLATOW: Hmm. And the pointy part is important then?
Prof. DWYER: Yeah, the idea is you want to build up to concentrate the charges on the tip and build up the field to get the spark. And then, of course, if you want to safely divert the current down to the ground and not through your electronics or your wiring or your plumbing.
FLATOW: So you really enjoy watching electrical storms?
Prof. DWYER: I love watching thunderstorms. We get a lot of them down here in Florida. In fact, that's one of the reason why I started studying lightning is - I grew up in California, I didn't see too much lightning where I grew up. But here in Florida, in the summer, especially, we get thunderstorms almost every afternoon.
FLATOW: Yeah, I love watching them down there, too. Thanks for joining us.
Prof. DWYER: A pleasure.
FLATOW: Good luck to your watching those lightning bolts.
Prof. DWYER: Thank you.
FLATOW: Joseph R. Dwyer is a professor of physics and space scientist at the Florida Institute of Technology that's in Melbourne, Florida.
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