Where There’s Thunder, There’s Lightning Science

IRA FLATOW: This is Science Friday. I’m Ira Flatow. You know how the saying goes. Where there’s thunder, there’s lightning. Because as you know, lightning’s super hot flashes create the shockwave that we hear as thunder. 

[THUNDER] 

Oh, I love that sound. You know, you would think all these centuries after Ben Franklin captured lightning in a bottle, that we would know everything about it. But you know what? Lightning is more complicated and mysterious than what old Ben could have imagined, or what you might have learned in grade school. Like, lightning is just a build-up of charge grounding itself, right? 

Well, it’s really not that simple. Researchers are still puzzling out what initiates the actual bolt. Which ones are the most dangerous? And how can we predict lightning to protect people and structures? A lightning bolt is more than meets the eye. Why does it flash? Why does it branch? Why does a lightning flash sometimes start from the bottom, starting in tall buildings or structures and flashing up, flashing up into the atmosphere? Plus a few other mysteries. 

Our friend Amy Nordrum, news editor at the IEEE Spectrum has been reporting in depth as scientists work to map the mysteries of lightning. Welcome, Amy. 

AMY NORDRUM: Hi, Ira. 

IRA FLATOW: She’s here to help me as my voice goes away. Good to have you here this week. If you have a question, our number is 844-724-8255, 844-SCI-TALK. Or as usual, you can tweet us at @scifri. Let me bring in one of the researchers from Santis Tower. Dr. Farhad Rachidi is a professor at the Swiss Federal Institute of Technology in Lausanne, Switzerland. Welcome to Science Friday. 

FARHAD RACHIDI: Thanks, Ira. Hi. Hi, Ira. Hi, Amy. 

IRA FLATOW: Amy. 

AMY NORDRUM: Hi. 

IRA FLATOW: Why don’t you get us started here? 

AMY NORDRUM: Yeah, Farhad, so what do we know about how lightning forms in storms, and what triggers it to strike? 

FARHAD RACHIDI: Well, lightning is an electric discharge, the same kind of discharge that occurs when you walk across a carpet. And charges are separated by friction. And when you get close to an object like a door knob, there is a discharge. And so these extra charges return to the ground. 

So lightning is, to some extent, similar to this phenomenon, except that its path length is a few kilometers. It’s kind of a gigantic electrostatic discharge, which basically discharges to electrically charged region, either in the atmosphere or from a point in the atmosphere and the ground. 

AMY NORDRUM: And why does it happen– 

FARHAD RACHIDI: And of course– yeah. 

AMY NORDRUM: Why does it happen in some storms, but not every storm? 

FARHAD RACHIDI: Because lightning requires that positive and negative charges be separated in the cloud. And this happened in some of the clouds and in which there is an electrification process which occurs, which is quite complex, following some convection processes, which are still being studied by scientists. 

So basically what happens is that there are these updrafts, and various particles in the cloud collide to each other, and charges get separated. So typically, you have ice crystals which become positively charged and move upward. And the lower part of the cloud becomes negative, which is some kind of a mixture of ice and water. 

And so you need to have this charge separation, and this separation of the charge would generate an electric field. And it is when this electric field exceeds some kind of a specific threshold, then it creates a breakdown and leads to the initiation of the lightning discharge. 

IRA FLATOW: Now, Amy, I understand that you got started studying lightning because of a special tower that has an affinity for lightning bolts, it turns out. 

AMY NORDRUM: Yes, actually, this is a site called Santis Tower, which Farhad is very familiar with. That’s how I originally started learning about it. I write for a publication that covers a lot of electronics and electrical technologies, but we’re always writing about electricity that we produce, and generate, and distribute. And when I stumbled across the Santis Tower research, I realized, well, lightning is its own electrical phenomenon that we really don’t have that much to do with. 

And this mountaintop tower in the Swiss Alps is struck by lightning more than 100 times a year, possibly more frequently struck than any other object on the planet. And Farhad and his team have instrumented with all kinds of different gadgets to be able to understand and study lightning better. 

IRA FLATOW: Well, so what’s the most mysterious thing to you that we still don’t know about how lightning works? 

FARHAD RACHIDI: Yeah, well, as you said, more than 250 years ago, Benjamin Franklin demonstrated with his famous kite experience the electrical nature of lightning. And nearly 300 years after and despite the lots of studies and considerable progress also, lightning remains enigmatic and not fully understood. And what is interesting is that even the very initiation of the lightning discharge is not quite well understood. 

So I mean, if I can summarize the thing, is that in order to have lightning initiated, you need an electric field exceeding a critical value and this value is about 1.5 million volts per meter at the altitude of about five or six kilometers. Now the problem is that despite extensive measurements, either using balloons, aircraft, rockets, et cetera, fields inside the cloud have really exceeded 200,000 volts per meter. That is 1/10 the required field. 

And of course, some explanations have been proposed by scientists to solve this puzzle. For example, that it’s possible that stronger fields exist only in a relatively small region, which make them difficult to measure. But there is another interesting discovery some 20, 30 years ago back in 1990. So it’s quite recent where it has been demonstrated that lightning emits high energetic radiation. 

Actually, lightning is quite unique. I mean, there is no other phenomena, neither in nature nor manmade, that produce electromagnetic fields in so wide spectrum from very low frequencies, to radio frequencies, to microwave, and x-rays, and gamma rays. And these studies have shown that the energies of x-rays and gamma rays can be quite high, even much higher sometimes than the energy of a chest x-ray. 

And this actually is interesting because it suggests the existence of energetic electrons, which are moving extremely fast. And what is interesting is that there is a different type of discharge, which is called runaway breakdown, which requires indeed a smaller electric field of about 200,000 volts per meter, which is consistent with the data and which involves these energetic electrons. 

So this has been basically an important discovery in order to better understand the initiation of lightning. But still, there are many obscure points, as for example, what are the seed particles that are needed to produce this kind of specific breakdown? So I would say there are lots of things that are still unknown and people working on them. But even the very initiation of lightning is still a mystery today. 

IRA FLATOW: Let me bring out someone who works exactly– good segue for me, Farhad. Because I want to bring out a researcher who works on understanding where lightning comes from. And that is Bill Rison. He is a professor of electrical engineering at New Mexico Tech in Albuquerque. Welcome, Bill. 

WILLIAM RISON: Hi, thank you. 

IRA FLATOW: What do you– you were listening. Do we still not understand how lightning starts? 

WILLIAM RISON: We’re starting to understand better how that happens. Farhad talked about one mechanism as being what’s called relativistic runaway, electron avalanche in which electrons are accelerated in a smaller electric field, but are still able, through relativistic properties, to gain the necessary energy to start a discharge. 

However, our research, if you were to see that, basically, the discharge would propagate in the direction that the electrons are moving, which is in the opposite direction of the electric field. Our research is showing that the breakdown propagates in the direction of the electric field opposite the direction the electrons are moving. 

So it’s probably not relativistic runaway electron avalanche. It’s something that you can’t produce in the lab because in the lab, you can’t get such strong fields over the distances needed. But it’s a system of streamers. A streamer is an electrical discharge which doesn’t actually heat up the air, but just frees electrons. And the [? positive ?] breakdown propagates in the direction of the electric field, which is not what the relativistic runaway electron avalanche would predict. 

AMY NORDRUM: And Bill, do we know what might stir up these small pockets of more powerful electric fields and cause these breakdowns to form in the first place? 

WILLIAM RISON: Well, it’s not really a small pocket of fields. It basically is a field which probably extends 500 meters or so in distance. And it’s just something that we haven’t seen in the lab because we can’t in the lab produce the conditions which are produced in the thundercloud to get this. So while we still don’t really understand the mechanism for how exactly this works, we now have seen the evidence of what’s going on. And now the rotations are trying to get a better understanding of what physically is happening. 

IRA FLATOW: Let me go to the phones, because a lot of people have so many questions. Let’s go to Oregon. Mike, hi, welcome to Science Friday. Hi there, Mike. Are you there? 

MIKE: Thanks. I’m here. 

IRA FLATOW: Go for it. 

MIKE: Hello, how are you this morning? 

IRA FLATOW: Fine. 

MIKE: I live in La Grande in Northeast Oregon, and I’m a lookout for the US Forest Service. And I understand cloud lightning, and I understand lightning that comes out of the cloud and strikes the ground. But last weekend, we had massive lightning storms that lasted for hours last Friday and Saturday, including a lot of lightning that came as [INAUDIBLE] from the cloud and never struck the ground. And I don’t understand that. I don’t understand the science behind it because I thought they all even struck the cloud or stayed in the cloud. So if I could get an explanation for that, I would appreciate it. 

IRA FLATOW: All right, Bill. Bill, can you fill us in on what is the difference between cloud to cloud lightning and cloud to ground lightning? 

WILLIAM RISON: There’s really no difference in terms of the actual physical mechanism. Basically, lightning tries to go from one region of charge to another region of charge. And that charge can either be inside the cloud, or it can be in the ground. And lightning finds the easiest way to get from one point to the other. 

So if the easiest point is the one charging into the cloud to another charge in the cloud, it will stay entirely within a cloud. It can go from one cloud to another cloud. It can go from the cloud outside of the cloud and die before it goes anywhere else. Or it can go from the cloud to the ground. Or it can go from the cloud up into the ionosphere. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios, talking about lightning today. Our number, 844-724-8255. You can also tweet us at @scifri. Amy Nordrum, who’s editor at the IEEE Spectrum who loves lightning herself, is here to join me. 

AMY NORDRUM: Yeah, I actually used to be terrified of thunder storms when I was growing up. I was always really scared of them and would run into my parents’ room and sleep there whenever they happened. And I’m mostly over that now, but I’m totally fascinated by it. 

So Farhad, we were speaking a little about the different types of lightning that can occur. I know upward lightning is the most common type of lightning that happens actually at Santis Tower where you’re doing your work. So tell us a little about that and what some of the other ways are that scientists classify lightning. 

FARHAD RACHIDI: Exactly. So most of the lightning flashes actually occur within the cloud. And I mean, we believe, like, maybe 75% of lightning discharges occur within the cloud or in between the clouds. And about 25%, they terminate their path to ground, and these are called cloud to ground lightning. 

And cloud to ground lightning, they can be classified in terms of their direction of propagation and also in terms of the charge that they are carrying to the ground. So they can be downward negative or positive. So that means that they initiate from inside the cloud and then move towards the ground. And they carry either negative or positive charges. 

So actually, it happens that about 90% of cloud to ground flashes are downward negative probably because the lower part of the thunder cloud is charged negatively. So there is more chance that this type of lightning is more likely to occur. And about 10% of cloud to ground lightning flashes are downward positive. 

IRA FLATOW: Does that mean it starts on the ground and goes upwards? 

FARHAD RACHIDI: Actually, we can. So both these downward negative and positive, they start in the cloud and go down. And one can see actually when you look at the lightning discharge, you can see the direction, whether upward or downward, by looking at the direction of the branches. 

Now if you look on images of lightning or the next time you are in the middle of a thunderstorm, you will see that most of the lightning flashes in the direction of the branches are downward. And this indicates that most of the lightning flashes are downward, except when you have very tall structures. So when you have very tall structures, then you can have, let’s say, an upside down lightning or an upward lightning, in the sense that lightning is initiated from the ground and developing upward. 

And this is called upward lightning and it is only produced from the tip of tall objects, typically 100 meters or taller. So for instance, in New York, where you are, so most of the lightning discharges to the Empire State buildings or other tall buildings are upward flashes. Or if you look at other pictures of lightning to some tall structures like– I don’t know– Eiffel Tower in Paris or CN Tower in Toronto, they are upward flashes. That means that they are initiated from the structure. 

And so this is a quite new type of lighting. I think maybe 150 years ago, when there was no tall structures, probably there were no or very little upward lightning discharge. And this is quite interesting because of course, now we have a lot of tall structures. And one particular type of tall structures is wind turbines, which are becoming taller and taller. And we know that one of the main causes of damage of wind turbines are lightning strikes. 

IRA FLATOW: Wow. 

FARHAD RACHIDI: And this is due to, of course, downward lightning, so they attract– I mean, some of the downward lightnings are terminate on to one of the blades of wind turbines. But also, most of the lightning flashes to the wind turbines are actually upward lightning that is initiated by the turbine itself. 

IRA FLATOW: All right, we’re going to come back and talk lots more about lightning with our guests. 844-724-8255. You can tweet us at @scifri. We’ll be right back after this break. Don’t go away. 

This is Science Friday. I’m Ira Flatow. We’re talking about the wonder and mystery of lightning, how it’s both powerful and unpredictable. And you know, it claimed the lives of more than 2,000 people around the world every year, not to mention the property damage. 

With me is IEEE Spectrum news editor Amy Nordrum, who’s been reporting on new strides in lightning research this year, how researchers are getting closer to understanding lightning’s origins and predicting lightning strikes. We’ve been talking this hour with Bill Rison, professor of electrical engineering in New Mexico Tech in Albuquerque, New Mexico, who’s had to leave us this hour. And Dr. Farhad Rachidi, a professor at the Swiss Federal Institute of Technology and Lightning Research in Lausanne, Switzerland. 

When we left, you were talking. You just got an idea about wind turbines and how the lightning travels up from the turbine blades up into the sky. 

FARHAD RACHIDI: Right, absolutely. 

IRA FLATOW: Wow, so does that mean they are in danger? If we go into a wind turbine society, we’re in danger of losing them, or do they have protection on them? 

FARHAD RACHIDI: They have protection on them, but it is becoming a challenging problem to protect them, because actually, until maybe 10 years ago, in order to design, let’s say, an efficient lightning protection system, basically what people do, they look at the lightning incidents in the region the wind turbines are to be erected. And they look, for instance, at that region and they see that OK, the statistics show that there are maybe three, four lighting flashes per square kilometer there. 

But the problem is that once the wind turbines are erected, these turbines, which should have been struck by lightning once a year or once every two or three years, they are struck by lightning 10, 20, 30 times a year. And this is because they are initiating these upward lightning discharges. 

IRA FLATOW: That is amazing. 

FARHAD RACHIDI: And– yeah, absolutely. 

IRA FLATOW: So we have to find a way then of protecting these turbines better. 

FARHAD RACHIDI: Absolutely. Absolutely. Understand, especially considering the fact that upward lighting flashes, they are characterized by different characteristics. Their electric current has different characteristics compared to downward flashes. And sometimes the lightning protection system is designed based on the characteristic of downward flashes. 

IRA FLATOW: Wow, that’s interesting. All right, we have a lot of calls. 

FARHAD RACHIDI: And there are– 

IRA FLATOW: I want to get to them before we run out of time. I don’t mean to interrupt, but there’s so many people. First of all, let me go to calls that we’ve gotten during the week here. Here is a question from Steven in Sacramento. 

STEVEN: I was wondering if we could harvest lightning for energy like we do for wind and solar. 

IRA FLATOW: And that is a common question we are getting today. Could we harvest electricity? 

FARHAD RACHIDI: Actually, not really. Actually, lighting is not a very interesting source of energy. Actually, there’s lots of energy in a lightning discharge. So each cloud to ground lightning involves an energy of more than one billion of joules. 

But there are two problems that we face in order to use this energy. First of all, of course, there are lots of lightning discharges over the years. So we think that there is about 50 to 100 flashes to ground per second over the planet. So if we were able to capture all these lightning flashes, which is, of course, an impossible thing to do, but assuming that we could capture all these flashes, that this would correspond to maximum power available, which is quite significant. 

But there is another problem, is that most of this energy is converted to thunder to hot air to radio waves. And there is only a very small fraction, which is available at the channel base. So the electrical energy that we could store and we could capture and store at the base of the channel is quite a small fraction of energy. And I think the total energy in a single flash, assuming it could be captured, would only operate a single light bulb for a few months or so. 

IRA FLATOW: Wow. 

FARHAD RACHIDI: So it is not a very good and efficient way of harvesting lighting– 

AMY NORDRUM: Well, Farhad– 

FARHAD RACHIDI: –energy. 

AMY NORDRUM: Farhad, I know you have big plans next year to start triggering lightning actually up at Santis tower in the Swiss Alps at your lightning research facility. So how do you plan to do that, and why do you want to do it? Why are you interested in doing that? 

FARHAD RACHIDI: Yeah, absolutely. So perhaps I can say a few things about triggering lightning. So actually, one of the main challenges of lightning research is to obtain experimental data because of the random nature of lighting and the fact that inside high voltage laboratory, we cannot really reproduce lightning, as Bill was saying. 

So we need to do experiment on real lightning. And there are different ways of obtaining data on lightning. One is the use of tall towers which are struck by lightning often. And so that’s what we do. Another technique that has been used for decades is the artificial initiation of lightning using rockets. And this has been used for research purposes. 

So basically, this technique is based on firing of a small rocket, which trades a grounded wire. So we offer a preferential path to the lightning. So of course, we have to launch the rocket when the electric field, that ground is sufficiently high, so that there is a good chance of triggering a lightning. And then– 

IRA FLATOW: So you’re doing Ben Franklin’s experiment over again, just with a rocket, instead of a kite. 

FARHAD RACHIDI: Absolutely. So we make that the lightning discharge goes to a specific point in the ground at which we have some sensors to measure lightning [INAUDIBLE] and then we have lots of other equipment around to measure other things. 

IRA FLATOW: Let me– 

FARHAD RACHIDI: So this is a way– yeah. 

IRA FLATOW: I want to bring in another guest to talk about predicting lightning because while we can’t yet predict lightning, we can detect it when it happens all over the world, including in the Arctic. It’s not a common occurrence, but something that has happened repeatedly this last Saturday. I want to bring on one of the people responsible for monitoring lightning flashes around the world. That is Dr. Ryan Said. He is a research scientist and electrical engineering for the Finnish company Vaisala, which runs the Global Lightning Detection Network. Welcome to Science Friday. 

RYAN SAID: Happy to be here. Thank you. 

IRA FLATOW: So you help and maintain two big lightning detection networks, one for the US, one that covers the whole world. What is the point of that? 

RYAN SAID: Yeah, so we continuously monitor lightning all over the world. And as Farhad was saying, there’s a lot of lightning to monitor, 50 to 100 flashes every single second. And we do this by using networks of GPS synchronized radio receivers. As Farhad was saying, each lightning flash has a lot of electrical currents. And they essentially act as broadcast antennas in the sky. And then we measure the radio waves that they emit at these remote sensors to locate where the lightning is. 

AMY NORDRUM: And like Ira was saying, lightning was detected in the Arctic this last weekend. And I understand your network was involved. How common is that? 

RYAN SAID: Yeah, the conditions for lightning in the Arctic are fairly unusual. You need warm moist air and some vertical instability. And that’s much more common over the tropics or in mid-latitudes during the local summer. That said, each summer, we typically detect a few thunderstorms in the Arctic region. 

But this one was really notable from the standpoint of how many flashes we detected. In fact, the global network saw over 600 lightning events within 600 miles of the North Pole. And that’s over three times as many events as we’ve seen in any previous storm in that region, although to be fair, we only have records going back to 2012. 

IRA FLATOW: Let’s go to the phones to Massachusetts. Hi, Michael. Welcome to Science Friday. 

MICHAEL: Hi. Hello, how are you? 

IRA FLATOW: Hi there, go ahead. 

MICHAEL: So yeah. One of my favorite stories from my dad, who was a Navy pilot, is he was hit off of Lockerbie, Scotland by lightning. And lightning actually entered the aircraft and propagated on the inside as a ball of lightning or plasma, and then exited. How common is this? You guys ever heard of that before? 

IRA FLATOW: Wow. Wow. 

RYAN SAID: Yeah, so ball of lightning is a really interesting anecdotal phenomenon. It’s usually characterized by some luminous ball which is usually associated with a nearby thunderstorm. But interestingly, this phenomena hasn’t been reproduced in a controlled experiment. So it’s still an outstanding question in the lightning community. 

IRA FLATOW: Well, let me ask both of you. So it’s safe if lightning hits a plane? We should not be worried if we’re in an airplane [INAUDIBLE] lightning striking it? 

FARHAD RACHIDI: Well, in principle, I think airplanes are well protected against lightning. And what is interesting is that every commercial airplane is on average struck by lightning once a year. And again, as for the case of tall structures, which initiate their own lightning, most of these lightning flashes that strike airplanes are initiated from the airplane itself. That is, you can see that I mean from the airplane up, you have branches, which are towards the sky, and from the airplane down, the branches are towards the ground, which indicate that the point of initiation of lightning was the airplane itself. 

IRA FLATOW: Wow. 

FARHAD RACHIDI: Now the traditional airplanes, which are made essentially of metal, they are very well protected against lightning. We know that metallic enclosures typically protect everything which is inside from the outside electromagnetic [INAUDIBLE] whatever that could be. But today, we are using more and more composite material. And because of that, the protection of, let’s say, modern aircraft is becoming more and more complex and challenging. 

IRA FLATOW: Wow, that’s a very interesting thing to learn. Yes, Amy? 

AMY NORDRUM: And then Ryan, I know lately, you’ve been working on trying to measure another particular type of lightning called hot lightning for the first time. So what is that? 

RYAN SAID: Yeah, the first thing to know about hot lightning is it’s not actually any harder than normal types of lightning. But it’s called that because of its capacity to heat up an object that is struck. So a lightning flash to the ground consists of multiple current surges. They are called return strokes. They’re very powerful, but they are very short. They last for less than about 1,000th of a second. 

And the difference with hot lightning is it has something called a continuous current that continues to flow for attending to 100 times longer. And it’s this sustained current that causes the extra heating. And actually, this can cause– more likely to cause forest fires or maybe damage a wind turbine blade, to bring in the topic from earlier. 

The problem is our ground based networks aren’t able to detect this continuing current. We can just tell where the impulsive part strike the ground. But now there is a new weather satellite that was recently launched that has a new lightning sensor that is able to detect these continuing currents. So this is really a game changing opportunity for us, where now not only can we tell where the lightning struck the ground, but we can identify those that pose more of a hazard from the perspective of heating. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios. We have a cut from Richard from Madison, Wisconsin who sent us a story on our Science Friday Vox Pop app about a close call with lightning. 

RICHARD: The craziest lightning I’ve ever seen, or I should say felt, struck me while I was holding an umbrella in a wide open parking lot. I felt some tug on the umbrella like static electricity, and it pulled me and the umbrella up. And the next thing I knew, I heard a very loud blam. I was on the ground, and there was a woman about 50 yards from me, screaming, are you OK? Are you OK? 

RYAN SAID: Wow. 

IRA FLATOW: Wow. Ryan, is that common? How fearful should people be? I mean, holding an umbrella in a parking lot during a lightning storm, not a great idea. 

RYAN SAID: Yeah, lightning is very dangerous– very high electric currents and voltages involved. And most injuries happen not from direct lightning strikes but from a lightning strike nearby. And that’s because as the lightning channel starts to make its way towards Earth and when it’s about 50 yards up or so, you can have these upward leaders that come up to meet it. And so there can be a pretty wide area where you have these electrical sparks coming up from the ground that can be quite dangerous as well. So that might have been what was happening in this case. 

AMY NORDRUM: And Farhad, can you tell us a little about how lightning manifests in different kinds of weather? Like, you think about heat lightning, or hear about thunder snow. What’s going on there? 

FARHAD RACHIDI: Yeah, you can have– I mean, generally, lightning occurs within the thunderstorm. But you can have also lightning occurring in other conditions. For example, in volcano clouds. So I mean, I think everybody has seen images of lightning discharge over different types of volcano eruption. It can also occur in a sandstorm. So there are many observations. So the same phenomenon that leads to the separation of charge in a thundercloud, similar phenomena can occur within a sandstorm and produce some lightning or lightning like discharges. 

And what is also interesting is that lightning is not an only terrestrial phenomenon. It has been observed also on other planets. So we have optical and the radio noise data that have been, I would say, interpreted to indicate that there are lightning discharges on different planets of the solar system at least on Venus, Jupiter, I guess, also on Saturn. So it can occur in different conditions. 

IRA FLATOW: Wow. 

FARHAD RACHIDI: But of course, the main condition is related to thunderstorm. 

IRA FLATOW: And Ryan, how does a lightning rod protect you? I mean, how do we get protected? And does it offer a cone of protection around us? 

RYAN SAID: Yes, so as I was mentioning earlier, the lightning channel that’s coming to the ground is going to make a contact somewhere. So the point of a lightning rod is it encourages attachment to the lightning rod itself, and then that is safely connected through some conducting mesh down to the ground. 

So if you have a lightning discharge that’s going to happen nearby, it helps move that dangerous current in a safe path down to the ground and hopefully not strike another part of your structure and cause more damage. 

IRA FLATOW: Wow. So many questions, so little time. Thank you all for joining us today, especially Amy Nordrum, news editor at the IEEE Spectrum. 

AMY NORDRUM: Thanks, Ira. 

IRA FLATOW: I’m glad you’re appreciating thunderstorms now. 

AMY NORDRUM: I know. Me, too. 

IRA FLATOW: That’s great. Farhad Rachidi, lightning researcher at the Swiss Federal Institute of Technology, and Ryan Said, research scientist for Vaisala, and thank you all for joining us today.

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