Episode 084 - Thunder and Lightning Part Two - Very Very Frightening
Date: 08/22/21
Link: https://www.epicureanfriends.com/thread/2148-episode-eight-four-meteorology-thunder-and-lightning-very-very-frightning-part-t/
Summary
Section titled “Summary”Before entering the passage, Cassius quotes the Letter to Pythocles on Epicurus’s method of multiple explanations: when several theories are consistent with the phenomena and none can be eliminated, all must be held open rather than one arbitrarily chosen — and Principal Doctrine 24 is quoted and analyzed in detail. The Principal Doctrines (Κύριαι Δόξαι) are briefly described for listeners new to the podcast.
Don reads Book 6, lines 173–335, covering clouds, thunder, and lightning. Martin confirms that thunder comes from lightning, not cloud collision; that clouds have no hollow caverns (verified by flying through them); and that friction producing charge separation is the correct physical intuition behind Lucretius’s “fiery seeds” — what Lucretius lacked was knowledge of electrodynamics. The episode closes with discussion of slingshot bullets, amber-rubbing as the ancients’ only form of electrostatics, and various electrostatic generators including the Wimshurst machine and Van de Graaff generator.
Transcript
Section titled “Transcript”Cassius: Welcome to Episode 84 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 where you’ll find a complete description of our goals and ground rules. If you have any questions about those, please contact us at the forum for more information. In this episode we’ll read approximately lines 173 through 335 as we continue further into Book Six on thunder and lightning. Now let’s join Don reading today’s text.
Don: And so the clouds will blaze with winged fire and tempests will shine with trembling flame, for things made hot by motion we see will fall on fire, and leaden bullets in a long course through the air have melted as they fled. Therefore this fiery wind, when it has burst the sides of this dark cloud, forces and instantly scatters many seeds of fire, which makes the sudden flash of lightning strike our sight. This happens when the clouds are thick and roll in heaps, one pile above another, with wondrous swiftness through the air. Nor must you think this false, because the clouds to us that stand below seem rather broad than deep or raised on heaps — for see how the winds will whirl along the air these rolling clouds, raised mountain high; and on the mountaintops the clouds observed are higher, some than others, and piled in heaps. And when the winds are still, the higher row will press the lower down; then you may judge of their prodigious weight and view their hollow caverns formed as it were in hanging rocks, wherein a tempest the rough winds are shut and scorned to be confined and roar with horrid noise like savage beasts within their dens, chained down — they grumble here and there on every side within the clouds, and striving to get free, roll every way about, and as they move collect the fiery seeds in great abundance and in the heated caverns toss them about until the clouds burst, and then they flash in shining flame. And for this reason, perhaps, the lightning — that swift and golden stream of pure fire — flies down upon the earth, because the clouds must needs contain within themselves plenty of fiery seeds, and such as are without moisture — bright and of a fiery color — for they must receive many fiery particles from the sun and therefore cannot but look red and send out flame. These, when the force of winds have pressed and driven into a narrow space, the fiery seeds being squeezed fly out and make that glaring flame to shine abroad. Or it lightens because the clouds above are rarified; for when the winds blow on them as they pass and gently stretch them out and wear them thin, the seeds of fire that make the light must needs fall out — but then it shines without much noise and terror and causes no confusion in the sky.
Now of what seeds the lightning is composed, its strokes will show and marks of fire it leaves behind, and steams of stinking sulfur in the air — for these are signs of fire, not wind or rain. For lightning will set on fire whole towns and with swift flames consume the houses to the ground. Nature has formed this subtle fire of seeds of heat the most minute and particles most apt to move, which nothing can resist. It passes forcibly the walls as voice and sound; it flies through stones and brass, and in a moment melts both brass and gold. It has a strange power to draw the liquor out and leave the vessel whole — this it does by loosening the texture of the cask and by widening its pores every way, so its heat may more easily find a passage through, and by the swiftness of its motion it dissolves the body of the liquor, scatters its seeds, and forces it out. And this the heat of the sun is not able to do in an age — so much stronger is the force of this bright flame, its motion more swift, and its power more irresistible.
But how these fires are formed and how they rage with so great force — as by their strokes to beat down towers, to overturn houses, to tear up posts and beams, to shake and tumble down monuments of stone, to strike men dead and kill whole herds at once — by what power they cause such scenes of ruin, this I shall now explain as I promised, and keep you no longer in suspense.
You are to observe then that thunder is produced from thick clouds raised high, one above another, in the air — for the thunder never roars in a clear sky, nor is it discharged from clouds that are not thick and condensed, and this is evident from common observation. The clouds thicken every way over all the heavens as if the whole mass of darkness had left the shades of hell and filled the spacious hollows of the sky, and this dark heap of clouds spreads a dreadful night over our heads and makes us tremble here below. These are the signs when a tempest is forging thunder in the air.
Besides, a black cloud is often observed at sea, below the dark regions of the clouds — it falls from the sky like a stream of flowing pitch into the water, and being full of fire and wind draws a black tempest with it, loaded with storms and thunder, so that those on land tremble and fly for shelter to their houses. Those clouds, then, you must think, are high above our heads — they could not overwhelm the earth with so much darkness were they not raised in heaps above and driven between us and the sun’s light, nor could they load the earth with so great showers and make the rivers swell and drown the plains, unless the clouds were raised in heaps in the upper regions of the air.
These clouds are fully charged with wind and fire, and thence the lightnings flash and thunders roar. For as I said above, these hollow clouds are full of fiery seeds, and many they receive from the sun’s rays and borrow from their heat; and when the wind compels them to retreat to a closer room it drives out many seeds of fire and mingles with the flame. Then the loud tempest rolls along the sky, and in its heated entrails forms and points the thunder. This wind is set on fire either by the rapidity of its own motion, or catches from the fiery seeds within the cloud; and when it is raging hot and in a flame, it collects all its fury, and then the ripened thunder instantly splits and bursts the cloud. The fiery tempest blazes all abroad with the darts of flashing light, followed by frightful noise, as if the temples of the gods above were rent asunder. The earth below trembles dreadfully at the shock, and the loud murmurs scour through all the heavens, for the whole tempest shakes and roars aloud; then grievous showers in great abundance follow the concussion, as if the skies were all dissolved in rain and poured down inundations from above. So dreadful is the clap that flies abroad with red-hot lightning when the clouds burst and storms of fiery wind rage through the air.
Or else the lightning flies when, from without, a furious wind beats hard upon a cloud replete with thunder, ripe for birth, which when it bursts, the fiery vortex falls — we in our language call it thunder — and makes its way where strokes most prevailed. Sometimes a furious wind will burst the cloud before it is set on fire, but kindles as it flies in its long passage through the air; for in its course it throws off the heavy seeds that lay behind and could not make their way, and brushed and carried off other small seeds from the air, which join and fall on fire as they fly. Just as a ball of lead melts in its course and throwing off the cold and stubborn seeds takes fire and softens in the air; and the fury of the stroke, perhaps, may raise a fire from the force of a cold wind, unkindled, beats hard with all its power, for then the seeds of fire may flow together upon the violence of the stroke, not only from the wind, but from the thing it strikes — as when we strike the flint with steel, the fire flies out. And though the iron may be by nature cold, yet when it feels the blow, the hot seeds of fire will spread abroad. And thus, whatever the lightning falls upon may easily be set on fire, if it be in its nature fit and disposed to burn.
Nor can the wind be supposed to be perfectly cold, since it is discharged from above with so much violence; and if it be not inflamed as it drives through the air, yet it must have some degree of heat when it comes to the earth. The swiftness and heavy stroke of the thunder and the violence of its fall proceed from hence: the wind, shut up within the cloud, rages in all its strength and struggles hard to get free; and when the cloud can no longer bear the fury of its efforts, it breaks out and flies abroad with mighty force, as stones and darts from mighty engines thrown.
Besides, the thunder is formed of small and smooth seeds, so subtle that nothing can withstand its force. It gets between and pierces through the smallest pores; it meets with nothing that can divert its passage, and therefore flies abroad with the swiftest motion. And then, since all bodies of weight naturally descend, when blows or outward force is added to their innate gravity, their motion doubles, and the violence of the stroke drives them downward with greater speed, and consequently they beat through everything that obstructs their motion much sooner and with more vehemence pursue their course.
Cassius: Thank you, Don. That was a long section today — about 170 lines — and I appreciate your soldiering through it. We’re really getting into a lot of details about his speculation on how thunder, lightning, and associated meteorological phenomena work. If we get too caught up in these details we’ll be less productive if we don’t also step back and talk about the big picture. So today it probably makes the most sense to pick out whatever details seem interesting, but before we do that, let’s do a little bit of the general philosophy and put it in context.
Before we get into this section, I want to refer people back to the Letter to Pythocles. Early in that letter — perhaps around line 80 in the numbering — Epicurus says, and I’ll read this section quickly: “for we must not conduct scientific investigation by means of empty assumptions and arbitrary principles, but follow the lead of phenomena. For our life has not now any place for irrational belief and groundless imaginings, but we must live free from trouble. Now all goes on without disturbance as far as regards each of those things which may be explained in several ways so as to harmonize with what we perceive, when one admits that we are bound to do probable theories about them. But when one accepts one theory and rejects another which harmonizes just as well with the phenomena, it is obvious that he altogether leaves the path of scientific inquiry and has recourse to myth. Now we can obtain indications of what happens above from some of the phenomena on Earth, for we can observe how they come to pass, though we cannot observe the phenomena in the sky, for they may be produced in several ways.” Yet he says we must never desert the appearance of any of the phenomena, and we must distinguish those things whose production in several ways is not contradicted by the phenomena on Earth.
We probably ought to talk about this for a moment, because what he’s saying is that there are going to be situations in life — especially looking up at the sky — where we have limited evidence. We don’t have enough information to eliminate every possibility, and we can come up with several possibilities that are consistent with what we see, but we’re not sure which one is correct. And he’s emphasizing that if that’s the situation, we have to accept it. We have to say there are several possibilities and we should not just arbitrarily pick one and say, “this is mine and I’m going to stick with it no matter what anyone else says and no matter what the phenomena says, even though I cannot really eliminate these other possibilities.” In this section about thunder, lightning, and meteorological phenomena, Lucretius is constantly saying, “this may be the case, or something else may be the case.” I think it’s important for people to understand that he did not see that as a contradiction of his philosophy — he saw it as an important part of it, to be honest about whether we are sure of something or not.
Okay, that’s my opening. Let’s see what people think about that. Agree, disagree, emphasize something else. What do you think, Don?
Don: Agree.
Cassius: Martin, what do you think about that?
Martin: I mean, this was very good that you added this again, because when I read this passage from Pythocles, I wasn’t sure what it means — what he means with his alternatives. Does it mean, depending on the case, this happens and at another time that happens? Or is it, we just don’t know what the one real mechanism is? And after you quoted this from Pythocles, it’s pretty much clear: it doesn’t matter. Both can be the case, and because we don’t know the difference anyway, it does not matter whether he means that we don’t know which of the one true explanations is correct, or whether sometimes this happens and sometimes that.
Don: Yeah, I would agree. It’s one of those things where you can see lightning, you can hear thunder, but what are the underlying reasons for it? And Lucretius — and by extension Epicurus — is saying, well, it could be this, or it could be this, or it could be this. They all end in the same result. We all see the lightning, we all hear the thunder, but here are possible underlying causes, with the limited knowledge and observation we can have.
Cassius: Right, and I would hammer home the point Martin made — that “it doesn’t matter.” I think people need to be careful, because Martin is correct when he says it doesn’t matter, but there are different meanings of “it doesn’t matter” and people should not think it means this is not significant. Because there’s a huge philosophical point here: if you don’t know which among these options is correct, it is wrong for you to take the position that only one of them can be correct. Epicurus says that in several ways in several different sections. One of the places he says it comes across as something to the effect that people who do that are basically like witch doctors or magicians — they’re asserting that only one thing can be true, and that’s more appropriate for a magician or wizard to do than for a reason-guided, scientifically minded person. If you don’t know which option is correct, you need to be honest and say so. But there are several that fully explain the phenomena without implying that there’s some supernatural god pulling strings behind the curtain — and that is what we really need: to be free from the doubt that there is such a god. And I don’t think he’s discounting the possibility that more observations might later point towards one alternative or another. Right now he’s saying: you can use your rational mind, look at the observations you can make, and these are some possibilities. It’s a very scientific mindset — multiple theories, no way to prove any particular one.
Cassius: In addition to the quotes we’ve already included, I know there are others, and it would be negligent of me not to point everybody also to Principal Doctrine 24, which is one of the longer ones. Let me read the full PD 24 — I’ll use Bailey’s version:
“If you reject any single sensation and fail to distinguish between the conclusion of opinion as to the appearance awaiting confirmation and that which is actually given by the sensation or feeling or each intuitive apprehension of the mind, you will confound all other sensations as well with the same groundless opinion, so that you will reject every standard of judgment.”
I’ve done my best to put some emphasis as I read that, but it’s still a very confusing sentence. Nobody can really understand it without reading and pouring over it in detail. But the second part is probably more clear and more applicable to what we’re talking about:
“And if among the mental images created by your opinion, you affirm both that which awaits confirmation and that which does not, you will not escape error, since you will have preserved the whole cause of doubt in every judgment between what is right and what is wrong.”
To me that one’s pretty clear: if you have multiple opinions in your mind about what could be the case and you affirm one that still needs more evidence as being true, then you’ve preserved in your mind the error you’ve eliminated from your thought processes — the difference between being certain and not being certain — and you’ve institutionalized a wrong judgment and prevented yourself from ever coming back to correct your opinion. I believe PD 24 and these comments from Epicurus and Lucretius in other sections of the poem are all pointing in this direction: don’t be so dogmatic about something unless you are really, really, really sure you have the evidence to back it up.
Don: Whenever you were reading PD 24 and you used the words “right” or “wrong,” I immediately wondered whether it was a moral stance or a factual stance. I have to think he’s talking about right and wrong in the sense of factual accuracy. I hear people say sometimes that Aristotle or certain others have a correspondence theory of truth — meaning your opinion needs to correspond as closely as possible with what is true. That’s what I would think he means by “right and wrong” there.
Cassius: Yeah, I think the same thing. I looked it up, and the word he actually uses — interestingly, it’s not two different words. Sorry for bringing up the Greek again, but the word he uses is orthos. He says it’s either orthos or not orthos — the same word, just negated the second time. And of course that’s where we get “orthography” and “orthodox” — the word orthos means right, true, or correct. So he is talking about a factual basis there, not some moral meaning. But I find it interesting that he uses the same word and just negates it, rather than using two separate opposite words.
Cassius: I really strongly believe that PD 24 would be one of the most productive doctrines to dig into and discuss. I rarely see it discussed on the internet as often as I think it deserves, because this is right at the center of the whole epistemological — canonical — theory of knowledge that Epicurus was advocating, and it applies across the board. It’s really behind all of our discussions about the gods as well. He’s got a theory of the gods that is non-supernatural, and I feel like he probably admitted that a lot of what he was saying was speculation that could not be proved. But with this attitude of acknowledging that keeping alternate explanations in mind is sufficient, you can look at that as a weakness or understand it as a strength of the philosophy. And you have to see it as a strength, because he’s right — it is wrong to take the position that you’re confident of something when you don’t have the evidence to support it. There is no God and there is no Platonic absolute ideal dimension that you can go to and say, “there’s my answer with absolute certainty.” Everybody has to sort all these things out in their own mind with their own evidence and their own experience, and there’s no crutch or outside standard you can just look to — and that’s not a weakness of the philosophy, it’s the strength of it.
Don: Right. And I think the long text of Principal Doctrine 24 gets at the point that these are somewhat arbitrary demarcations in this list — the original Greek manuscripts just flowed together like any book, and you could easily make an argument that if you’re going to make a list, ideas based on opinion could be taken out as a separate one. But reading 24 and 25 together probably makes sense — they may have originally been one paragraph or one thought.
I should say too — we’re throwing around the Principal Doctrines here. For anybody who just happens upon this episode of the podcast: do we briefly say what the Principal Doctrines are?
Cassius: Sure, go ahead.
Don: Well, correct me if I’m wrong. They’re in Diogenes Laertius’s Lives of the Eminent Philosophers, Book 10, which is entirely dedicated to Epicurus. At the very end of that book are 40 Principal Doctrines that were presented as a summary of Epicurus’s philosophy as a whole, and Diogenes thought them important enough to include there — ending his entire work with them as well. So it’s 40 doctrines basically summarizing the whole of the philosophy. But the thing is, they were not originally numbered as 40 separate doctrines — it’s basically a book in text form, and over the years people have divided it into 40 separate doctrines, although whenever I read through them I’m not always sure whether there should be separations where the traditional separations are.
Cassius: Yeah, that’s at least what we’re talking about. And so Don — Martin — correct me where I’m wrong about what I’m about to say: I think it’s important to contrast this with the Vatican Sayings, which is also a list of doctrines but we don’t know who put that together. We don’t know anything really about that listing at all. The Principal Doctrines — as I understand it — is not really a list in the original form; as you said, Don, there are like five or six or more different titles people give to it. The Κύριαι Δόξαι or whatever the Greek is — the reason there are so many names is because this was originally, like you said, essentially one of his original letters. It was handed around just like the Letter to Herodotus or the Letter to Pythocles or Menoeceus — as Epicurus’s best summary of all of his doctrines in one place. I think this may be the one that’s referred to in the Alexander the Oracle Monger story by Lucian, where Alexander burned his pithiest list of sayings. I’ve read different commentators say so. So this document — whether you divide it into forty or four or fifty-three or however you divide it — is probably his best summary of all of his philosophy in one place. And that’s why we’re so fortunate that Diogenes Laertius decided to include it, so it got copied along with everything else.
Don: Right, right. Well, now we’re ending up spending our whole episode talking about these general things rather than the details of this passage — but I think this is very important and good stuff. It’s probably more important than some of the details of the clouds.
Don: I think that’s definitely true. I’m glad you brought it up, because if we tried to get into the weeds of whether the clouds are hollow or whether they’re this or that, we can just go in circles. But as context for the passage we read, the stuff you brought up is directly applicable. I’m glad you did.
Cassius: Okay. Well, I think that was worthwhile, but I’m also concerned that Martin is far more advanced than I am at least in the details of some of the physics of this stuff. So having said everything we said, I now think we do want to turn to the details of the paragraphs. Anything that strikes anybody’s eye as interesting to talk about, we’ll just take as much time as we need. I especially don’t want to cut out any opportunity for Martin to comment on anything that he wants to talk about. So let’s start with around line 173 and go systematically through what we read today.
Martin: Yeah, that’s already not really very clear — and also they make it hollow. I mean, I don’t remember it now. Was this in the passage before, that there was a claim that the clouds are made hollow?
Cassius: Yeah, I think he’s been talking for a while as if the clouds are hollow. And I noticed when I was editing last week’s podcast that I wasn’t clear about why I kept talking about that word “contexture” or “texture.” I started talking about how the clouds stay together and I probably ended up just being confusing about why I was even talking about that. But this issue of what holds them together, whether they’re hollow, whether they’re solid, how heavy they are — those seem to be of great significance to him as a component in how thunder and lightning are produced. So yes: he thinks there’s stuff inside the clouds that roll around and burst out at some point.
Martin: I don’t recall this hollow thing. I recall the other things you said but not that he said before that they are hollow or that they are made hollow — that sounds odd to me.
Cassius: He might not have been as clear in the earlier part, and I could be just hallucinating from my memory from last week — I probably get confused as to which week we’re talking about. But I do think that’s been one of the implications of all we’re reading here about these clouds — that they seem to have things going on inside of them, presumably wrongly.
Don: Yeah, he talks down through there about the hollow. “You can view their hollow caverns” — and I can see that if you look up at a cloud and it’s like rolling around, it almost looks like there’s little caves and indentations. It’s fascinating to look at, but that could be where he’s getting the idea that they’re hollow — it almost looks like you can see inside them sometimes when you have big puffy clouds.
Cassius: As if they’re confining the wind and the fire within them. Looking at passage 173 — “when he talks about the prodigious weight and their hollow caverns where in a tempest the rough winds are shut and scorned to be confined and roar with horrid noise like savage beasts within their dens chained down” — it’s as if what we see of the outside of the clouds is concealing a bunch of stuff going on inside.
Don: Exactly, yeah.
Martin: Yeah, but that is not factual. I mean, I’ve been ascending and descending through clouds many times by airplane; I never encountered that at all.
Cassius: That would be an example of a superior bit of evidence that Martin has.
Don: Another vantage point for observation, yeah.
Martin: It’s not just the texture — we can see some outside things and there’s quite some change on the surface. But inside, the clouds appear to me as fairly dense mist and fairly homogeneous. So it’s really at the boundary between what we say is part of the cloud and what is not. This boundary is also not that sharp when we get close by, but compared to the total size of the clouds, that transition area is smaller. That’s why we perceive clouds from a distance as having fairly sharp edges — but they wouldn’t be that sharp. What’s actually going on is typically at the surface of what we perceive as the boundary of the cloud. Inside, it doesn’t look like there’s that much change.
Cassius: I would have thought that if you went up to the top of a mountain and got surrounded by clouds at the top, you might — like an airplane — presume you’re in the middle of the cloud, but maybe they just weren’t sure about that.
Martin: The thing is, when you do that, you’re already in an area where the cloud is bound — it has a boundary with the mountain and probably some intense interaction. My impression is that clouds you walk through on mountains were thinner than those we pass through with an airplane.
Don: Well, looking at the beginning of section 204 — it’s going to be the first example and it says “for this reason, perhaps.” I don’t know whether Munro and Bailey and everybody else have that “perhaps,” or whether that’s Brown putting it in, but I think that’s an example of how he knows he needs to hedge and not present that everything is absolutely clear.
Then the next sentence: “for things made hot by motion” — correct observation. And then something very interesting: “leaden bullets in a long course through the air have melted as they fled.” That is a fact I would not have expected that the ancients could have observed. From my experience with air guns — even an air gun has a lot less power than a powder-driven gun — still, when I looked at the bullets after shots, they were warmer. So it is a correct observation that bullets can be warmer after flight. But I don’t think this is from the passing through the air — it’s rather from what happens inside the gun, because even though the original force is transmitted by a spring, that spring is converted into compressing air. When you quickly compress air to fairly high pressure it becomes very hot, and this hot air gets in close contact with the bullet and transfers its heat before pushing it out. And when the expansion of the air pushes the bullet, the air cools down again — but it’s normally in close contact with the bullet. So that’s why the bullet may keep its heat, whereas the air which drove it has become cooler. Plus there will be some friction of the bullet within the barrel. But I don’t think the travel through the air will heat up the bullet further.
Don: Well, you know, my question is: what kind of bullet is he talking about in 50 BC?
Martin: Exactly.
Don: Well, they use lead shot in slingshots and probably other projectile weapons. So how did they accelerate them so quickly?
Martin: Well, you can get surprising speeds with a sling. I did a quick search on the internet for ancient lead shot, and the first article that comes up is from National Geographic — the headline is “Ancient slingshot was as deadly as a .44 Magnum.” So there you go.
Don: And of course, Munro and Bailey confirm basically what he’s saying. Munro says “nay, a leaden ball whirling through a long course even melts,” and Bailey says “yea, even a ball of lead whirling in a long course will melt.” So Bailey followed Munro almost exactly. I suspect, rather than heating from air friction, it’s that when it hits the target, the bullet deforms suddenly — internal friction from that impact produces the melting.
Martin: I think it’s rather the impact and deformation and internal friction which produces and melts it, rather than travel through the air. And mostly people will not find the shot immediately when it did not hit the target — it’s moved much further. But when it hits a nearby target, they’d be quickly enough there to find it. So it’s more consistent with this idea that it probably happened on impact.
Cassius: I mean, things can heat up going through the air and pushing the air back, but I’m skeptical whether a slingshot could get the velocity. And if we touch a car, it will not get hot even if you drive at 200 kilometers per hour on the German Autobahn — it’s not going to melt. According to Scientific American, a heavy sling bullet or stone could reach speeds of up to 100 miles an hour, and I wouldn’t think 100 miles an hour would be enough to melt lead.
Martin: Exactly. Plus lead has a very high density, which works against the heating.
Cassius: Well, it’s interesting to compare this to last week’s discussion of whips breaking the sound barrier — I would never have thought about that either. Maybe there’s more to this than my scientific knowledge can construct. I’m also wondering if there were different alloys of lead he might be talking about, or whether these are firsthand observations or stories told to him — “oh yeah, we flung it and it melted in the air, it was amazing.” Things made hot by motion — on its face, that aspect is very acceptable. Friction creates heat. And of course our NASA astronauts would tell you that things falling through the atmosphere can get pretty hot, as those capsules return to Earth.
Don: Meteors — they had meteors, but they wouldn’t have known what that was.
Cassius: You know, that’s a great point though. Meteors might be —
Don: And they definitely did because they would use iron from meteorites that they found in metallurgy.
Martin: If they realized that meteors were in flames as they travel through the air because of the friction with the air, that would be largely correct if they understood that. On the meteorites, on impact they get extremely hot — the pressure and temperature are so high that they can produce diamonds.
Cassius: We’re not making much progress through the passage today. Well — I mean, we’re making great progress. Our discussion has been excellent. But our progress through the numbered passages is slower than anticipated, so we probably need to come to an end pretty soon. Martin, do you see anything further in these passages that you want to pick out?
Martin: Yeah, I would like to remark on this “motion” thing. If we look just very basically, there is something correct about it: this motion and friction produce charge separation. And this charge separation is the driving force which produces lightning. Now, all his alternative explanations about fire particles — of course, that’s nonsense. But the basic idea that motion and friction are involved is correct. It’s just that at that time they didn’t have any sufficient knowledge of electrodynamics to put this together — how this works to produce the lightning. It’s not that the clouds are loaded with fire particles. It’s that electrical charges are separated, and that mounting potential difference between these charged clouds — and also the charge difference between cloud and ground — produces the lightning. Not something about fire.
Cassius: That’s a really good observation. Yeah. I think the only way he can imagine something being “on fire” is if it involves fire particles — going back to almost Empedocles, who was the one with the earth, air, fire, and water thing. So he can’t imagine something producing light that isn’t related to fire. I’m not going to let this episode finish before I use this word at least once: what we’re talking about, right Martin, is electrostatic charges, right?
Martin: Yes.
Cassius: Okay. Now I’m thinking — I don’t remember this for sure — but is it possible that even in Lucretius they would have known the same thing we do, that in winter time when we put on some kind of cloth that rubs against our body and then touch something metal, you get a static electric discharge?
Martin: No, that is if you wear synthetics. They didn’t have synthetics at that time. If you use natural fiber, you are less likely to get that. I had a pullover made from synthetics and that effect was really strong — just pulling it over, a few times I got a spark right in the eye, which was very painful. I ruled it out by switching to a natural-fiber pullover.
Cassius: Wait a minute — you mean our observation of electrostatic discharges in winter in our houses is based on synthetic materials? What about Wimshurst machines and all those different things that produce electrostatic charges by friction? And Ben Franklin with his kite and his Leyden jars — those aren’t dependent on synthetics, are they?
Martin: No, no — that is a different thing. But the one thing the ancients knew was amber. By rubbing amber against a particular other material, you get a very strong separation of charges, and with that they could produce sparks already. So that is the only thing I’m aware of that the ancients knew a little bit about electricity.
Cassius: Okay. So they’re not shuffling across the floors of their atriums in Herculaneum with shoes on, creating the kind of static discharges we see today with synthetics. But if amber is available, they would have had some point of comparison. I guess if you see a static discharge off your finger or whatever, it’s not so hard to analogize that to a lightning bolt.
Martin: No, I think it is, because it’s very small and you barely see it. The reason that the lightning is so huge is not obvious from that. This knowledge of electricity as such we have only since maybe the 15th century.
Don: The only thing I found in a quick search: in about 600 BC, the ancient Greeks discovered that rubbing fur on amber — as Martin said — produced a static charge. They said it caused an attraction between the two, and what the Greeks discovered was actually static electricity.
Cassius: That kind of reminds me — we’re still going to get to the magnetism stuff, but it’s still further down. I realize I’m going to jump way ahead here in the text review, but I want to say this before I forget it by next week. The last part — paragraph 335 — says “since all bodies of weight naturally descend, when blows or outward force is added to their innate gravity, their motion doubles.” I wasn’t sure whether he was talking about just gravity in the common sense — if it’s heavy, it falls — or whether he’s talking about the atoms themselves falling because of their weight, and whether there’s a connection there. I certainly think there’s a connection. And that’s really behind my original question about what keeps a cloud together — whatever it is that pulls things together, whether it’s hooks on atoms or temperature differentials.
Martin: It has nothing to do with gravity or cohesion or adhesion forces, because they are just very local. What Norman — what you hinted at was more correct: there are differences in temperature gradients and pressure gradients, and those govern where you have condensed droplets of mist and where you don’t. That’s what gives clouds their shape.
Cassius: That makes sense — different temperature gradients in the air, so the water vapor condenses more in some areas than in others.
Cassius: All right, let’s not try to pull any more passages in for today. We can come back next week, cover anything we want to pull out of these, and maybe read some more too — just keep reading through this dense material on thunder and continue to have our parallel discussions, picking out whatever we think is appropriate. I think we’re up to about line 239, so Martin, your remarks from before cover the next paragraph too?
Martin: Yes, my remark covers through to paragraph 239, so the next ones to discuss would be from 246 onwards.
Cassius: Okay, let’s do that then. Next week we’ll read some more and potentially look at 246, but we won’t re-read 246 through 335 again necessarily.
Martin: That works.
Cassius: So Martin, as we close for today, what general thoughts do you have?
Martin: I think I mentioned two general thoughts already. I have no more general thoughts.
Cassius: Okay, good, good, good. All right, Don — for today?
Don: I think I’m good. I would be remiss though if I did not at least quote the Bohemian Rhapsody: “Thunder and lightning, very, very frightening.”
Cassius: That’s all right. Well, I know when I was growing up I used to be just fascinated by electrostatic discharges. There’s the Wimshurst machine — the one with rotating counter-rotating plates that collect the static discharge and then you can move the arms together and get about an inch of spark. I always found all that stuff fascinating.
Cassius: Is that a Van de Graaff generator?
Don: Van de Graaff is the one with the belt in it. That’s the one I think is associated with Tesla — the big ball at the top, then a tower with a belt within the tower, and that’s apparently what can produce really high voltages.
Cassius: And of course back when — since I’m like an ancient person — I actually remember, Martin, you probably do too, and Don: cars used to have ignition coils. And those were fun to play with if you could get a battery connected to an ignition coil — you can really generate some sparks with those too.
Don: We need to talk about your childhood.
Cassius: Yeah, and static electricity to me has always been fascinating because that’s where you get your “free energy” from — you’re supposed to get wires hanging miles long in the atmosphere and collect static electricity as your new upcoming energy source. Martin, I would be disappointed in you if you were not a big Tesla fan, right?
Martin: What?
Cassius: You’re not?
Martin: But definitely not, because I think he was over the top. He was not German, right? He was like Serbian, or something like that?
Don: I think he was Czech, no?
Martin: I mean, he was some sort of a genius, but he overestimated a lot of things, made bad guesses, and anything outside of his core areas he just didn’t really nail.
Cassius: I like the way you said “some sort of a genius.” That’s exactly the impression I have too — he was borderline insane it seems like, but seemed to be a very smart guy as well. Okay, for the record: he was Serbian, an ethnic Serb.
Martin: No, not Chinese.
Cassius: All right, Martin — you must be spending too much time in Thailand lately. It’s good to get you back in Germany and reconnect with your background. There are so many fascinating German inventors over the years. Okay, we’ll do that another time. Thanks everybody for your time today. I’ll try to edit this into something coherent and we’ll come back in a week. Thank you very much.
Don: All right. Have a good weekend. Bye.