Episode 083 - Meteorology: Thunder and Lightning Part One
Date: 08/14/21
Link: https://www.epicureanfriends.com/thread/2135-episode-eighty-three-meteorology-thunder-and-lightning-part-one/
Summary
Section titled “Summary”The episode opens with the conclusion of the Book 6 introduction on the gods: the panel discusses Principal Doctrine 1, why a correct view of the gods is foundational to Epicurean physics, and the practical need for ordinary people to have a firm position on religion. A brief parallel to COVID-era prayer-versus-action debates arises, and the Epicurean epistemological concept of “waiting” (withholding judgment when evidence is insufficient, as found in Diogenes Laertius) is highlighted.
Martin reads Book 6, lines 68–164, opening the extended meteorological section. The panel discusses what holds clouds together, Martin explains that thunder comes from lightning (not cloud collisions) and that rumbling is the echo of a distant strike. Highlights include Martin’s observation that a whip’s crack is the first man-made supersonic event, discussion of lightning as analogous to fire (both heat air to luminescence), the Latin volans ignis (“flying fire”), the word aridus (dry) for clouds, and Lucretius’s observation that res (things) travel more slowly to the ears than to the eyes — light before sound.
Transcript
Section titled “Transcript”Cassius: Welcome to Episode 83 of Lucretius Today. I’m your host Cassius, and together with my panelists from the EpicureanFriends.com forum, we’ll walk you through the six books of Lucretius’ poem and discuss how Epicurean philosophy can apply to you today. We encourage you to study Epicurus for yourself, and we suggest the best place to start is the book Epicurus and His Philosophy by Norman DeWitt. For anyone not familiar with our podcast, please visit EpicureanFriends.com — there you’ll find our goals and ground rules, and if you have any questions about anything you hear in this podcast, you can contact us there and ask for more information. In Episode 83 we’ll read approximately lines 68 through 164 of Book Six, continue the opening of Book Six, and begin a discussion of natural explanations for meteorological phenomena such as thunder and lightning. Now let’s join Martin reading today’s text.
Martin: Unless you purge your mind of such conceits and banish them from your breasts, and forbear to think unworthily of the gods by charging them with things that break their peace — those sacred deities you will believe are always angry and offended with you — not that the supreme power of the gods can be so ruffled as to be eager to punish severely in their resentments, but because you fancy those beings who enjoy a perfect peace in themselves are subject to anger and the extravagances of revenge. And therefore you will no more approach their shrines with an easy mind; no more in tranquility and peace will you be able to receive the images, the representations of their divine forms, that form from their pure bodies and strike powerfully upon the minds of men. From hence you may collect what a wretched life you are to live. That the rules therefore of right reason may keep these evils at the greatest distance from us — though I have offered many things upon this subject before, yet much still remains to be observed, which I shall adorn with the smoothest words. And first the nature and phenomena of the heavens must be explained. And now I sing of tempests, and the flaming blasts of lightning, how they fly, and from what cause they dart through all the air — lest, when you view the several parts of heaven, you tremble, and, mad with superstition, ask: whence comes this winged fire? And to what quarter of heaven does it direct its course? How does it pierce through walls of stone? And having spent its rage, goes out again — the causes of which events, since men cannot assign by the laws of reason, they must, they suppose, be affected by the power of the gods. And thou, Calliope, my skillful muse, the joy of men and pleasure of the gods, lead on the course and guide me to the goal, that by thy conduct I may gain a crown and end the race with glory. First, the blue arch of heaven is shaken with thunder, because the airy clouds flying aloft are formed by adverse winds and strike together. For where the sky is clear, you hear no noise; but where the clouds are thick and drive in troops, thence comes a louder sound and murmurs through the air. Besides, the clouds are not so solid as stones and wood, nor so thin as mist and flying smoke — for then, depressed by their own weight, they would either fall abruptly down as stones, or like smoke they would disperse, and not be able to keep in the chilling snow and showers of hail. They give the crack through the wide space of heaven as curtains stretched upon the posts and beams in lofty theatres, unruffled by the boisterous winds and blown to pieces — they make a rattling noise like paper torn. This sound, you observe, would sound like clothes split asunder, or flying sheets, when tossed by strokes of wind their roll and flutter through the sky. And sometimes the clouds will not directly meet and engage front to front, but in their different motions will rudely shock the sides of one another as they pass. Hence comes that dry crashing sound we hear, that lasts for some time before it breaks its close prison and grows out. All things you see from hence will shake and tremble at the dreadful clap, and the heavens — the mighty wards of this wide world — are torn and burst asunder in a moment when a collected force of restless wind gets suddenly within a cloud, and there enclosed it rolls furiously about and stretches the hollow space still more and more, until the sides grow thick and are condensed, and when it summons its whole strength and rages to get free — then comes a frightful break; it flies abroad with horrid noise. Nor is this strange, when a small bladder full of wind will likewise give a mighty crack when it is suddenly burst. When the winds strike violently upon the clouds, this may produce a noise. While we see the clouds with their rough edges are driven about in various manners — as a blast of southwest winds blowing hard upon the thick woods, the boughs give a sound and the branches rattle through the air. And sometimes a violent force of a fierce wind will be directly with all its rage upon a cloud and cut it asunder. That the winds will shatter the clouds is evident by experience. Over here below, where their power is much weaker, they will overturn the strongest trees and tear them up by the roots. And then the clouds, like waves, roll about in the wide ocean of the air and cause a roaring noise by dashing together. The same happens in large rivers and in the wide sea when it is broken and rages with the tide. And sometimes the fiery force of lightning pours from one cloud into another. If a cloud full of moisture receives this fire, it extinguishes it with great noise, as a red-hot iron just taken out of the glowing heat when we plunge it hastily into cold water. But if a dry cloud receives a flame, it takes fire instantly and rattles in the air, as when a fire raging with mighty force is driven by rushing winds upon a hill covered with low laurels and sets all in a blaze — for nothing burns with more dreadful noise and crackling flames than the leaves of the Delphic laurel, sacred to Apollo. And lastly, pieces of ice and showers of hail enclosed in mighty clouds will often sound like thunder, for the winds have driven and pressed them close. These mountainous clouds being condensed will burst and discharge their weight of ice and hail. It lightens when the clouds, by violent strokes and meeting, beat out many seeds of fire and strike as flint and steel, or stone and stone — for then the light flies out and scatters shining sparks of fire. But we never hear the thunderclap till we have seen the lightning, for the images of things approach our ears much slower than they reach our eyes. This you prove when you observe a fellow at a distance cutting down a tree — you see the blow struck before you hear the stroke. And so we see the lightning before we hear the thunder. So the noise and flame fly out together and proceed from the same cause, the same shock and bursting of the clouds.
Cassius: Martin, thank you for reading that for us today. Maybe not quite as much deep content as last week, but still a lot of interesting material. I’m particularly going to be interested in hearing some of your scientific analysis of the descriptions of thunder and things like that. But before we get started into the science of the atmospheric phenomena, we have a couple of paragraphs that continue on from last week about the more general aspects — the very first one being how to think about the gods. As further introduction to this, we’ve had some discussions on the forum over the last week or so about the distinctions between the Epicureans and the Stoics. One position that came up was that the Epicureans advised that the gods should be ignored. I think that’s not correct, and this paragraph would be a reason for that — whether you take the idealistic view of the gods or a more realistic view that Epicurus thought there really existed gods. It does seem that Epicurus thought it was important to have a positive and firm view of the gods. Rather than ignoring them, I would say he thought it was important to have a firm position on them. Now I’ve gone on too long. Who wants to comment on that first paragraph?
Don: Yeah, I think you’re right. Epicurus in his writings definitely seems to acknowledge — and Philodemus in his writings as well — that the gods are an important topic, because that’s the first Principal Doctrine. The first Principal Doctrine talks about the blessed beings and that sort of thing. But you have to have the correct view of them, as opposed to the one where they’re going to rain down punishment on your head and are concerned with every little action you take.
Cassius: Yeah, in elaborating on that — sometimes we talk about whether Epicurus is taking a practical position or a rigorously logical theoretical position on certain things, and who he’s talking to. I always come back to the idea that Epicurus wants to talk to ordinary people, and a lot of ordinary people are never going to be able to get out of their minds this worry about the gods. Many of us today, especially the more advanced you get into physics and think about things, get comfortable with the idea that gods are just not something you should be worried about and it drops out of your mind. But as a practical reality, the great majority of the people in the world are not in that camp. They’re always going to have nagging doubts about religion and the gods. They need something to fill that spot in their minds, something to hold onto when the topic regularly comes up — something quick and easy to understand. And so by taking the position that perfect gods are not going to be concerned about what we do any more than we are concerned about what ants do, I do think that gives a lot of people something to hold onto, a position about religion they can be confident of and not be constantly plagued by doubts about.
Don: You know, Lucretius is even saying, it seems to me, that whenever people are looking for an explanation for things they fall back on the idea — “well, it’s the gods’ will, I have to pay attention to what the gods want, or they’re going to be mad at me.” And if you don’t understand lightning and thunder — which is what he’s going to go through for the next number of lines — it’s easy to just fall back on those easy black-and-white answers for complex problems. The gods, when misunderstood, provide that sense of relief when people need to be practical and actually confront the problems in front of them rather than simply praying for answers they need to be dealing with themselves.
Don: Oh my gosh — it seems like the current context of the world. I see so many of my friends and people I’m associated with in day-to-day life, and when dealing with something like COVID-19, there’s just so much discussion of “let’s pray that we get well, that God protects us from this plague” — and if they do get sick, it’s pray, pray, pray, pray, pray. When in fact, at least from my perspective, there are so many more practical things that need to be done. If you just get caught up in the prayer and letting God take care of it — fatalism, that there’s nothing you can do to affect anything — you’re not going to take the steps you could otherwise take to potentially save your life or the lives of your friends. One of the memes I’ve seen recently is that “the COVID virus is everywhere, God is everywhere too.” And my first thought to that was: well, can we get a vaccine for Him too?
Cassius: That’s right, that’s right! Oh my gosh, there are so many different clichés like that floating around. Martin, I’m droning on — you have thoughts on this particular point?
Martin: No, because it’s just a resumption of what Lucretius had in earlier passages already — that the gods should not be feared and we should not stick to those old superstitions concerning the gods. And Lucretius really does seem to do that — he seems to recapitulate a lot of things, just to emphasize it over and over. If he hasn’t mentioned it for a while, he brings it up again: “okay, now remember I said this back a while ago, I’m going to re-emphasize it now.” That seems to be a recurring theme throughout the poem.
Cassius: Yeah. So we can just pass on — as already discussed — things like “forms from their pure bodies which strike powerfully upon the minds of men.” I mean, I don’t know whether people are really expected to take it seriously that these forms strike powerfully upon their minds or not, but regardless, the bottom line is the same: religion is a concern for many many people, and even those of us who have largely dismissed it as a concern are constantly affected by people around us for whom it is a concern. And so there are just many aspects to that that warrant discussion. Like you said earlier, Don — it’s the number one Principal Doctrine. Although it’s sometimes hard to look at the forty doctrines and figure out exactly the priority ranking, it’s hard to dismiss that when you place something first you’re saying there’s some importance to it. He does the same thing in the Letter to Menoeceus too.
Don: Right, right — no doubt he thought it was a tremendously important topic. And if you did not get it right, you would be leading a wretched life.
Cassius: And I think it’s the whole idea — we’ve talked about how the physics are the foundation upon which the philosophy is built — and I think having a right view of religion and the gods is another one of those foundational bricks. If it’s not in place you can’t really start building on top of it; it makes for a wobbly foundation. I really think he considered this to be a part of physics. I know from a practical point of view, when I try to organize things on the forum, I divide philosophy between physics, ethics, and epistemology. And that’s probably a traditional breakdown. But the gods are probably going to go under physics, because taking a position as to how the gods fit into the nature of the universe is extremely important.
Cassius: Okay. “So that the rules of right reason can keep these evils at the greatest distance from us — I’ve offered many things before, and yet there are many things still to be observed, which I shall adorn with the smoothest verse. And first, the nature and phenomena of the heavens must be explained.” And I know Don’s thinking — I really like the way he says “I sing of tempests and the flaming blasts of lightning.” He does have a way with words. It’s one of the reasons I haven’t learned Latin — I can look it up in dictionaries, I’ve got some basic understanding of the grammar, but Lucretius is one of those things where it would be nice to really be able to appreciate the Latin.
Don: Yeah, because if this is an inaccurate transposition of the emotion of it — about the flaming blasts of lightning, “how they fly and from what cause they dart through the air, lest when you view the several parts of heaven you tremble and mad with superstition ask: whence comes this winged fire?” — it’s very dramatic.
Cassius: “The causes of which events, since men cannot assign by the laws of reason, they must, they suppose, be affected by the power of the gods.” There it is again.
Don: Yeah. We probably ought to mention in this context the passage in Diogenes Laertius where he talks about the idea of “waiting” — because when they talk about “cannot assign by the laws of reason” and “they must, they suppose, be affected by the power of the gods,” I think that’s part of the Epicurean analysis too: you have to keep in mind that when you do not have enough evidence to come to a conclusion, you don’t come to a conclusion until you get that evidence, and if you can’t get it, you hold it in a different category of thought. You don’t act like it’s something certain that you can never doubt or challenge.
Cassius: Right. So that “waiting” concept that is directly in Diogenes Laertius is pretty critical here. And Martin, you probably have something to add on that — the idea of waiting when the evidence isn’t clear. How would you describe it in the way you think?
Martin: If there’s no need to take a position and the evidence is not clear, then just waiting is the right thing to do. Of course, if we need to take action because of some urgency, then we need to do a best guess. But if the evidence isn’t clear enough, it’s better to wait if you don’t have to take any action.
Cassius: That’s a really good contextual way to look at that, Martin. If it’s not an emergency, you can wait for additional evidence. But if you have to take action and need to make a good enough guess — yeah. I really like that. That’s a great point.
Don: Oh, I had to look up the Latin — you sort of challenged me there. And it does actually say volans ignis in the original — so that’s “flying fire.” Great line.
Cassius: Okay. Last week we talked about the Calliope reference, so I don’t guess we came up with anything new on that since last week. That’s just a teaser to make people go back and listen to last week’s episode. “By thy conduct, I may gain a crown and end the race with glory” — there’s been a number of references throughout the poem to this being a race and to gaining a victory at the end of it. Okay, now Don — we get into the section you’ve been waiting for: the thunder, lightning, and all of the fire and brimstone.
Don: Paean anax! And what is Paean anax?
Cassius: That’s Epicurus’ expletive. And how does it translate, literally?
Don: Now you put me on the spot. I was thinking you had that one at the tip of your tongue.
Cassius: I was thinking you had that one at the tip of your tongue.
Don: I have the Greek at the tip of my tongue; I don’t have the English. It’s a reference to Apollo, I know. I think it’s basically “my god.”
Cassius: Okay, yeah — we’ll come back to that. I keep saying I’ve been dreading this section — it looks like there’s about a thousand lines of thunder and lightning and earthquakes, and then he finally starts talking about disease and the plague of Athens. But there’s a lot of meteorological and geological phenomena to wade through in the next few hundred lines.
Cassius: Well, of course, this is another area of expertise of our friend Martin from Germany, who’s expert in everything physics-related. So I’m sure meteorology is a topic he’s well versed on. This paragraph 96 — one part that interests me is the discussion of the texture of clouds, that they’re not like mist and flying smoke because then they’d either fall down like stones or disperse. I’m not really sure what it is that keeps a cloud together. When you look up in the sky and see all these fluffy white things, what does keep them together, Martin? Do you know?
Martin: Oh, that I couldn’t just say out of the pocket. But actually, they are like mist — the mist we see here on the ground is basically clouds on the ground. Up there in the clouds there are nothing else, and typically the mist — but that can come with variations. Some are just like the mist we normally know: liquid, small droplets of water. But in other cases they may be frozen.
Cassius: You may be asking a question that’s totally irrelevant to everybody in the world other than the fact that it strikes me as interesting. But obviously, mists and things like flying smoke do eventually disperse. What is it that kind of keeps them together initially? Is there any merit to the question at all? The clouds do kind of stay together for significant periods of time when you look up in the sky. What is it that creates this dividing line?
Don: This is completely off the top of my head, but there have to be different temperature differentials in the atmosphere — at different altitudes it’s going to be colder or warmer, and that’s what… Because the thing that always gets me is whenever you can see for miles and miles, the bottoms of the clouds just look flat, and you can tell there’s some sort of barrier keeping them that way. There have to be different temperature differentials and wind velocity and that sort of thing.
Cassius: One of the things that always strikes me about clouds is that they look so solid, but you can look away from one for a few minutes and look back and it’s already changed its shape. But if you sort of stare at it, you can’t really see it change — it’s so slow, it just seems so solid.
Don: Yeah. Of course, we talk a lot about limits and boundaries and so forth. I’m kind of thinking to myself: what is it that gives us the perception that there is a boundary between a cloud and the part of the atmosphere not within that cloud? Because we’re going to spend a couple of paragraphs here talking about how he thinks thunder results from things rolling around inside the clouds. What is it that gives a cloud its shape at all? Because I’m sure there’s not a very bright dividing line between the edge of the cloud and the surrounding atmosphere.
Don: The thing that gets me is there are so many different shapes of clouds. You look in photographs online to identify different types of clouds, and it amazes me there are so many — types of clouds I have never seen that you’ll see photographs of online. Some of the mammatus clouds, I believe, are those large globular sort of looking clouds that are just wild looking.
Cassius: Yeah. Or Martin — maybe what I should be trying to frame the discussion as: I presume we don’t think this is a current scientific description of the way thunder and lightning work, but it’s not entirely off base, is it?
Martin: Yeah, it’s interesting. He bases a lot on observations, and when he sticks close to the observation it’s correct. And when he tries to infer too far away, then it gets a bit off — like that he thinks clouds are not mist, but they are like mist. And this seems to be a recurring theme: his powers of observation are remarkable.
Don: And I think so many times he’ll say things that even I haven’t thought of before, if I’ve looked at a particular phenomenon. But then whenever he goes, like Martin says, beyond the observation, it’s like — well, you can see the progression at least. You can see he’s made the observation and he’s trying to make a physical explanation: it’s not a supernatural phenomenon, there are no gods involved, here’s a naturalistic physical explanation for what I’m seeing. The fact that it’s factually wrong doesn’t strike me as important as that he’s looking for that natural physical reason.
Don: Yeah, in fact — I don’t spend very much time on the seashore or sailing, but I thought the discussion of the flapping cloths and sheets was pretty interesting as a comparison for how the sound from those can maybe be compared to thunder. Do you have a comment about that part, Martin? I guess flags flapping in the wind do create a sort of sharp clap — I don’t even fully know how flags or sheets or sails flapping in the wind really create that sharp clap you hear from them.
Don: I would think he could have used the idea of a whip too.
Cassius: A whip, yeah.
Don: Do you know how that stuff works, Martin?
Cassius: That’s a very technical term — “stuff.”
Martin: This particular sharp clap of the whip — it’s done by a skillful handler who brings his whip into a wave motion. The whip is typically designed so that it becomes thinner toward the end, so the acceleration increases along the tip. What happens is the tip of the whip accelerates to a speed higher than sound. The tip of the whip is probably the first object ever accelerated by man to above the speed of sound. And at the same time, from the vibration, it also gives off some sound, and because that movement is faster than the speed of sound, these sound waves are compressed into something like a shock wave — basically the same thing as when a supersonic jet goes above you. So the same thing is produced by the whip.
Don: I had never thought of that before — that the whip is the first man-made object to travel faster than sound. That’s a great way to look at that.
Martin: You don’t need high technology. You just need to design the whip properly and skillfully enough to use it, and then with just normal muscle force you get that tip faster than the speed of sound.
Cassius: Oh that’s great. That never occurred to me before, but you’re absolutely right. And I’ve definitely learned something there. Well, how does that work in comparison with sails or flags or other clapping sounds that come from cloth? They don’t go with the speed of sound, do they?
Martin: No, no, no. Normally not. And you will also not perceive those normally as sharp as the sound from the whip.
Cassius: Yeah, that’s very true. The whip sound is very sharp — like you say, it’s almost like a jet.
Martin: My best guess for the flag movement is that it’s moving waves. And if a wave hits the end, depending on how it goes — I forgot the details on this one — that wave gets reflected when it hits the end of the flag, and this leads to a sudden movement at the end of the flag. That might be responsible for the sharp crack. Because if the reflection inverts the phase, then it should move very suddenly to the other side.
Don: Well, in regard to the whip — I don’t intuitively think that the whip operates by pushing significant amounts of air, because the tip is so small there’s not that much air being pushed around. But with a flag, or with a theater curtain, or with sheets blowing in the wind, I can see more of an issue — they probably do produce their noise by doing something with the air around them.
Martin: They’re moving waves, and these waves push around the air, and that then generates sound.
Cassius: Interesting. Well, now you’ve got me fascinated with the whip thing too. I guess they had whips for a long time in human history, and there’s no reason to think this would be invented at a particular location or time. I guess Epicurus would have been familiar with whips and how they make those noises.
Don: The Romans were definitely familiar with whips.
Cassius: That’s exactly where my thought was going, but I wasn’t necessarily going to say that. But now that you’ve said it, Don — yes. Whipping people and animals has been a tradition of many types of humans for many different years.
Martin: But normally, if you use the whip properly, you don’t even need to hit the animal. So the animals react to that sound. The sound is just made in the air, not when the whip hits some object.
Cassius: That’s a great point too. So the special shepherds won’t hit the sheep with the whip — they just want the noise to scare them enough to move them in the right direction.
Martin: Yeah. And the sound is different when the whip hits something than this crack from reaching supersonic speed.
Cassius: Well, I’m reading through several of these passages trying to find a place to jump on. So as far as what we think the truth is today about thunder and lightning — you’re not going to have sound from just clouds coming into contact with each other. The sound is generated by a lightning strike. Is that correct, Martin?
Martin: Yes, that is normally correct. At least the loud sounds are created by the lightning, and most lightning happens actually between clouds — it doesn’t reach the earth. So depending on conditions, you may not even see it, but you can hear the thunder.
Cassius: What about the rumbling as opposed to a sharp lightning clap? Does the rumbling have any different source to it?
Martin: When the rumbling is there, it comes from far away. That means this written sharp sound of the lightning gets reflected by a lot of objects in the area — by mountains, buildings, and things like this. And as they arrive from different total distances, they arrive here at different times. So that’s why the rumbling is drawn out.
Cassius: Okay. So Lucretius is spending some significant time here talking about the composition of the clouds and how that might affect the noise. I see references to rain and hail and sleet and snow. Is there any current viability to the approach that a cloud with a lot of moisture coming into contact with a cloud that doesn’t have as much moisture would have some relationship to the noise generated?
Martin: You can easily produce some sound, so I wouldn’t completely exclude that some relative movement of clouds may in certain conditions produce slight sound. It will not be like that from thunder — nothing particularly loud — but I wouldn’t completely exclude the possibility.
Cassius: Well, I do see one thing worthy of at least a reference — about how in section 145 there’s the mention of “as when a fire raging with mighty force is driven by rushing winds upon a hill covered with laurels and sets all in a blaze — for nothing burns with more dreadful noise and crackling flames than the leaves of the Delphic laurel, sacred to Apollo.” There’s a couple of points there that might be of interest. I’ve never thought of laurel leaves as being particularly combustible. What do you think about fire making noise? I guess there is crackling — the crackling flame comes from the combustion of the material that’s being consumed, right? Or does the fire itself in the air generate sound?
Martin: Everything is there — the oxygen, the fuel — so it’s an interaction between the air around it and of course if you push around air this will produce sound. So it is a reasonable analogy for Lucretius to be talking about fire and using it as another point of reference, just like he can hear claps from cloth and flags and curtains flapping.
Cassius: I think it’s interesting too that he uses the analogy of a blacksmith putting a red-hot iron into cold water — he’s trying to extrapolate from that as well. That’s an interesting little observation. I thought there might be something interesting to say about the leaves of the laurel sacred to Apollo being particularly combustible, but I don’t know how I could derive any meaning from it — he seems to think those make a particularly dreadful noise. I don’t know why.
Don: I’ve never burnt laurel wood myself, so I’m not quite sure. And the only other thing we could squeeze out of that is that even though it’s sacred to the god Apollo, it’s still going to burn.
Martin: I still don’t fully understand this paragraph. I understand that if lightning hits dry leaves, yes, it’s likely to cause a fire. But he also seems to be talking about fire in the cloud, and I don’t see how that will happen, because normally the clouds are made of mist, or you have rare cases where clouds are made of dust. But this dust is normally not combustible, unless it’s something man-made like sawdust that can catch fire.
Cassius: Yeah, it almost seems like he’s trying to say that there are dry clouds and wet clouds.
Martin: Yeah. What Don was saying is that he perhaps wrongly thinks that some clouds may be more dry than others. I guess maybe it’s not wrong to say some clouds carry more rain than others. Are clouds all just water vapor? Are they made up of anything besides water vapor?
Martin: No, no, no — they are droplets, so that’s why we see them. Water evaporates on the ground, the air rises, water vapor mixes into the air, and when it gets to the cooler temperature up there it reaches saturation temperature, the water condenses into droplets. And if it’s very cold, they may freeze. These very high cirrus clouds you see normally in fair weather are high up and made of small pieces of ice, whereas the lower clouds are normally water droplets.
Cassius: But that might explain our difficulty with this passage — we today would presume that every cloud is made up of water vapor. We would not think there could be a “dry cloud,” because all clouds are made of water vapor. But maybe he didn’t understand that and thought some clouds could be made up of something besides water vapor.
Martin: There can be dust clouds. And I think in Italy you see them more frequently than in Germany, because the Sahara is quite close — they don’t need to pass the barrier of the Alps to get there. So I’m pretty sure it was a common sight in antiquity to see dust clouds from the Sahara above the area.
Cassius: That could definitely be true. And we could also be putting too much weight on just this particular translation. Maybe “dry cloud” is not actually in the Latin.
Don: And sure enough, there is the word — aridus — in the Latin, meaning dry, withered, parched. So he is definitely talking about dry clouds.
Martin: The only thing which doesn’t fit is that a dry cloud will burn. Dust is basically ground-up stone, and stone doesn’t burn.
Cassius: Yeah, because it does look like he’s clearly talking about a cloud receiving flame and then bursting into flame, to explain the lightning. And obviously we would not agree that that flame is exactly what’s going on. But I guess that’s one of the key aspects of this whole discussion — in looking at thunder and lightning, he’s equating lightning to a form of flame. Which I think we presumably would not do, right, Martin? Or is there any analogy or relevance between lightning and flame?
Martin: The analogy is both temperature. If you see a fire, the air becomes hot enough that it emits visible light with sufficient intensity. And that’s the same thing with lightning — when it passes through a channel of ionized air, it heats it up sufficiently that this air becomes hot, and that’s why we see the light. So it would not be completely wrong to talk about lightning in terms of fire. The only thing is that normally up there you don’t have something to feed the fire — that’s why it’s just a shock. It heats up the air during the discharge and cools down very quickly. That’s why it’s just a flash. Whereas when lightning hits the ground and combustible material, you have something that can maintain the fire, and you see the lasting effect of material burning.
Cassius: Well, that’s point number two of my basic physics education for today — first I did not understand how whips work, and now I find it reasonable to analogize lightning and fire. I thought that was just something you wouldn’t even consider an appropriate reference, but there’s more to it than I realized.
Don: Yeah, I think it’s interesting too. We were talking briefly about his powers of observation, and I thought it was interesting in paragraph 164 — talking specifically about images moving faster than sound. He talks about somebody cutting a tree down, and you see them moving the axe before you hear the stroke on the tree. And he even says we see the lightning before we hear the thunder.
Cassius: You know, I wonder if it goes into next week — but when you say that, Don, it seems to me I picked up a reference to, I guess we’re closing in on line 164 — the end of the material we had for today. I thought I saw something even more specific that used the word “image” going back to Epicurus’s discussion of images. Seems like I saw some reference in this material today where he was making an example of how images move more slowly than something else.
Don: I see it now. It does say it in Brown, line 164: “for the images of things approach our ears much slower than they reach our eyes.” So he is making a direct observation that sound would travel less quickly than light. But I’d have to dig back into the word “images” here to see whether that would also apply to his generic term of images — when he talks about everything giving off images, which are not necessarily the same as light. This may be a reference to him saying that images of things don’t travel at the same speed as light does. I’m probably putting too much weight on that right now. I’ll just maybe make a note that somebody studying the detailed analysis of Epicurean views of images might want to look at that one. It clearly is saying that light travels faster than sound.
Martin: Yeah, but it’s a bit of an odd formulation to talk of “sound images.”
Don: Well that’s exactly why I raised that issue. Let’s look at the other translations — Munro says “because things always travel more slowly to the ears than to the eyes.” And I’m sorry, that was Munro. Bailey says “things” too — so I don’t know whether they’re using the same technical term of “image” or not, because if he just says “things travel more slowly to the ears than to the eyes…” And I think it is “things” because — from what I can see here in my rudimentary Latin — he uses res for “things.” So the things move, and the Latin is talking about the oculī, the eyes, and the aurēs, the ears.
Cassius: Are you seeing res in this particular passage? Did you have the Loeb in front of you?
Don: Correct. It’s on line 166 — looks like the last word on that line. But it is interesting to think too — the basic principle of Epicurean physics being that all atoms travel at the same speed, at least initially. They all move in a straight line at the same speed until acted upon by the swerve or by bumping into another atom.
Cassius: Yeah, the bumping into other atoms would clearly restrict their ability to move in a straight line. Is it the case, Martin — going back into particle physics — that at the atomic level, even if they bounce off each other, the total motion may be the same speed as straight-line motion? Or at the very ultimate subatomic level, are some particles moving faster than others?
Martin: No, that’s not a correct assumption. Photons travel at the speed of light, and about everything else is slower than that typically, and it varies. Depending on what is moving and what has accelerated it, it can be much slower than the speed of light.
Don: One thing I think too — if he’s using res to mean “things” or “objects,” and the things or objects reach our eyes before they do our ears, he could just be referring to the fact that the object out there reaches our eyes first before it reaches our ears — instead of actually talking about the images or particles or atoms reaching our eyes. Since he’s using the word “things” or “objects,” it could be hedging his bets a little bit.
Cassius: Yeah. Well, we may be coming close to the end of what we can get out of today’s material. I don’t have in front of me what we’re going to do next week to build a bridge.
Don: I think there’s more thunder and lightning and rain and earthquakes, yeah.
Cassius: Have I mentioned this before?
Don: Yeah, yeah — because you’re still waiting for the death and destruction part.
Cassius: The sweet release of death. I see that we’re stopping at 164 today, but 173 is going to continue on with clouds and thunderbolts, so we may be directly involved in thunder and lightning for at least another week or two. We may have to get a guest meteorologist or something.
Don: Yeah, boy — we may have two more episodes on it the way I’m seeing here. It looks like we may be basically talking about thunder and lightning all the way until… I wonder if we do that all the way till we get to the plague of Athens. I see wind on line 295. But wait a minute — somewhere in here we get into magnetism, which I’m very interested to talk about. I think that’s up around line 900 or something like that.
Cassius: So there are some other interesting issues besides meteorology. We might want to consider reading more than a hundred lines — see how we can split this up so that we’re not talking about clouds for four weeks, taking our listeners into consideration. We don’t want to overburden them with clouds. I’ll definitely look at that when preparing the text for next week and see if we want to read a little longer than usual.
Cassius: Well, let’s go ahead and start wrapping it up for today. Now that you’ve educated me on whips and fire and clouds, Martin — do you have any other general comments?
Martin: No, I’m fine. I’ve said everything.
Cassius: Okay, very good. Don?
Don: I’m good for today.
Cassius: Okay, well, let’s wrap it up. That will make it easier for me to edit and get it out hopefully earlier this week. We’ll come back next week and continue with meteorology. Thanks a lot — bye bye.