WEBVTT - What's the Science of Invisibility? 0:00:00.160 --> 0:00:02.800 Guess what, mango, what's that? Will? I was reading this 0:00:02.840 --> 0:00:06.320 whole story about a bank robbery that happened in so 0:00:06.400 --> 0:00:09.440 this guy walks into two banks, one after the other. 0:00:09.760 --> 0:00:12.520 He has no mask and no face cover. I mean, 0:00:12.520 --> 0:00:14.680 it didn't seem like he was trying to hide himself. 0:00:14.720 --> 0:00:17.440 And he gets caught on camera pretty clearly, and so 0:00:17.520 --> 0:00:20.960 obviously he's apprehended not long after that. But the weird 0:00:21.000 --> 0:00:25.440 thing is when the cops come fromm he was totally baffled. Well, 0:00:25.440 --> 0:00:29.120 he kept saying, I was wearing the juice. The juice, Well, 0:00:29.160 --> 0:00:32.200 apparently he poured lemon juice all over his face because 0:00:32.200 --> 0:00:34.600 he knew it could be used as this invisible ink 0:00:34.640 --> 0:00:37.440 for writing. And the poor guy, he was really bewildered 0:00:37.440 --> 0:00:40.080 because he said he tested it out, and the cops 0:00:40.080 --> 0:00:42.440 pressed him for details, and he said the lemon juice 0:00:42.440 --> 0:00:44.440 had gotten in his eyes the first time when he 0:00:44.479 --> 0:00:46.880 poured it all over his face, and then he took 0:00:46.880 --> 0:00:49.080 a selfie to see if it had worked. And the 0:00:49.159 --> 0:00:52.159 combination of squinting and not being accustomed to taking his 0:00:52.200 --> 0:00:55.720 own photo, I mean, this this was well, it made 0:00:55.800 --> 0:00:58.560 him take a photograph that he wasn't in and he 0:00:58.720 --> 0:01:02.400 just believed that he was invisible. I know you almost 0:01:02.400 --> 0:01:04.720 feel bad for the guy, but you know, reading up 0:01:04.720 --> 0:01:07.840 on his invisible face juice made me wonder what is 0:01:07.920 --> 0:01:10.319 the science of invisibility and what are some of the 0:01:10.360 --> 0:01:13.240 things going on that we can't see? And where is 0:01:13.280 --> 0:01:36.040 my invisibility cloak? So let's dive in. Hey, their podcast listeners, 0:01:36.040 --> 0:01:38.480 welcome to Part Time Genius. I'm Will Pearson and as 0:01:38.520 --> 0:01:40.479 always I'm joined by my good friend Man Guesh, I'll 0:01:40.480 --> 0:01:42.520 Ticketer and over there on the other side of the 0:01:42.520 --> 0:01:45.200 glass with the biggest smile that you can't see is 0:01:45.240 --> 0:01:48.280 Tristan McNeil, our producer, And on today's show, we're taking 0:01:48.280 --> 0:01:50.640 a WorldWind tour of our invisible world and trying to 0:01:50.640 --> 0:01:53.400 get a better grasp of all things unseen. You know, 0:01:53.440 --> 0:01:57.240 the idea of invisibility is fascinated mankind for thousands of years. 0:01:57.680 --> 0:02:00.320 It's parts of our myths and our folklore and pop 0:02:00.360 --> 0:02:03.840 culture and even our psychology. Of course, there are lots 0:02:03.840 --> 0:02:06.080 of different kinds of invisibility, so this will be a 0:02:06.120 --> 0:02:09.960 super fun Hodgepodge episode where we cover as much as possible. 0:02:10.400 --> 0:02:12.360 We'll talk to a couple of insightful authors who have 0:02:12.400 --> 0:02:15.640 devoted years of study to stuff we can't see. So 0:02:15.639 --> 0:02:17.720 who do we have on the line today, Mango, Today 0:02:17.760 --> 0:02:20.639 we're talking to Bob Berman, one of America's top astronomy 0:02:20.680 --> 0:02:22.680 writers and author of a brand new book about the 0:02:22.680 --> 0:02:25.480 curious history of invisible light. It's called Zapped, and it's 0:02:25.520 --> 0:02:28.359 incredible and we'll have some wonderful quizzes along the way 0:02:28.360 --> 0:02:30.639 as usual. All right, So, in honor of Bob's new book, 0:02:30.639 --> 0:02:32.640 I want to dive straight into the science and talk 0:02:32.680 --> 0:02:36.680 about light, and more specifically invisible light. You know, obviously 0:02:36.680 --> 0:02:39.480 there are large portions of the electromagnetic spectrum that we 0:02:39.520 --> 0:02:42.519 have no trouble observing, but there's also a huge part 0:02:42.600 --> 0:02:45.640 that's totally invisible to us. That's the part that includes 0:02:45.680 --> 0:02:49.600 things like ultra violet light and for red light, radio waves, microwaves, 0:02:49.720 --> 0:02:52.880 X rays, gamma raves, you know, all that good stuff. Yeah. 0:02:53.200 --> 0:02:54.919 I mean, I always knew there were parts of the 0:02:54.960 --> 0:02:57.480 spectrum beyond our range of vision, just like you know 0:02:57.600 --> 0:03:00.640 there's sounds outside the limits of human hearing. But reading 0:03:00.680 --> 0:03:03.519 Bob's book put the vastness of light in a completely 0:03:03.600 --> 0:03:06.200 new perspective for me, and it really blew me away. 0:03:06.240 --> 0:03:08.639 So Burman rights, there's more light in the universe than 0:03:08.840 --> 0:03:11.119 anything else. So if you were to add up every 0:03:11.200 --> 0:03:14.120 individual light photon in the cosmos, they would account for 0:03:14.240 --> 0:03:19.240 nine point of everything there is. And those forms of 0:03:19.280 --> 0:03:22.040 invisible light you listed off, that actually makes up the 0:03:22.120 --> 0:03:24.640 vast majority of the light. I actually can't wrap my 0:03:24.720 --> 0:03:28.120 head around that fact that it seems unbelievable, but you know, 0:03:28.160 --> 0:03:30.960 our eyes are designed to recognize only the Sun's most 0:03:31.000 --> 0:03:34.280 abundant energy, so we really can only see the colors 0:03:34.280 --> 0:03:37.360 that the Sun emits most strongly. And even though the 0:03:37.360 --> 0:03:40.960 whole universe is light, the bulk of it, it's completely 0:03:41.000 --> 0:03:43.560 invisible to us. We've actually figured out all kinds of 0:03:43.680 --> 0:03:46.680 ingenious ways to measure and observe forms of invisible light. 0:03:47.120 --> 0:03:49.320 And one of the most interesting things I came across 0:03:49.360 --> 0:03:52.920 while prepping for this episode was the way human observation 0:03:53.000 --> 0:03:55.280 actually affects the behavior of light. All right, well, I 0:03:55.320 --> 0:03:57.200 think this is pretty complicated, so why don't you break 0:03:57.200 --> 0:03:59.440 it down a little. Well. When quantum theory became all 0:03:59.480 --> 0:04:02.680 the rage in the twentieth century, scientists started noticing something 0:04:02.840 --> 0:04:05.960 super weird. They found that when they use special equipment 0:04:05.960 --> 0:04:09.000 to pinpoint the location of photons, these tiny bits of 0:04:09.040 --> 0:04:12.480 matter always behaved as particles. For example, they could pass 0:04:12.520 --> 0:04:14.920 through one tiny hole or another in a barrier, but 0:04:15.040 --> 0:04:17.680 not through both holes at once. All right, so far, 0:04:17.760 --> 0:04:20.360 so good, and particles do what particles do that. I 0:04:20.360 --> 0:04:22.479 don't think there's anything weird about that, right, But the 0:04:22.520 --> 0:04:25.159 scientists also discovered that when they didn't try to determine 0:04:25.200 --> 0:04:28.320 the exact location of each photon, the photons behaved as 0:04:28.320 --> 0:04:31.200 waves instead of particles. So the photons were then able 0:04:31.240 --> 0:04:33.440 to pass through both tiny holes in a barrier at 0:04:33.440 --> 0:04:36.320 the same time. And that's something that only waves can do, 0:04:36.520 --> 0:04:40.559 not particles. Okay, alright, I spoke through soon. That's really weird. 0:04:40.640 --> 0:04:43.040 And so you're saying that light, photons and other sub 0:04:43.080 --> 0:04:46.080 atomic matter act like particles, you know, when they know 0:04:46.160 --> 0:04:48.240 we're watching, and then like waves when they know we 0:04:48.279 --> 0:04:51.320 aren't looking. Yeah, it's something like that. So obviously the 0:04:51.320 --> 0:04:54.280 photons themselves aren't aware of us watching them, but they 0:04:54.320 --> 0:04:56.960 definitely seem to act differently based on how closely we 0:04:57.000 --> 0:04:59.960 observe them. And the best explanation, at least according to 0:05:00.120 --> 0:05:03.160 most physicists, is that when we look closely, our brains 0:05:03.200 --> 0:05:05.200 halt the wave pattern so that we can see the 0:05:05.200 --> 0:05:07.800 photon in a certain place as a particle. It just 0:05:07.880 --> 0:05:10.760 makes us feel better that way. That's really insane, all right, 0:05:10.800 --> 0:05:12.960 So where does that leave us? Does light exists as 0:05:13.000 --> 0:05:16.159 a wave or as tiny bits of almost invisible matter? Yeah, 0:05:16.200 --> 0:05:19.880 it's both. So Bob Berman sums up the paradox this way, 0:05:20.200 --> 0:05:22.360 and I'm going to quote him here. He says, just 0:05:22.440 --> 0:05:25.719 a century ago, the local realism mindset of science and 0:05:25.839 --> 0:05:30.080 even common sense held that all objects, including atoms and photons, 0:05:30.320 --> 0:05:33.800 have an existence independent of our observation of them. But 0:05:33.880 --> 0:05:36.360 that's been replaced by a more modern view that our 0:05:36.400 --> 0:05:39.359 observation itself is necessary for the very existence of a 0:05:39.360 --> 0:05:42.920 photon or an electron. A spooky prospect, no kidding. Yeah, 0:05:43.000 --> 0:05:46.240 So he continues, it possessed no real existence as an 0:05:46.240 --> 0:05:49.640 actual photon or electron or whatever it was. Rather, it's 0:05:49.680 --> 0:05:54.440 observed existence is it's only existence. The observation establishes reality, 0:05:54.839 --> 0:05:58.520 nothing else is certain. That's pretty trippy. Yeah, the stuff 0:05:58.560 --> 0:06:01.440 feels so philosophical, and especially when you go from a 0:06:01.480 --> 0:06:05.040 micro perspective to a macro one, because just like with photons, 0:06:05.279 --> 0:06:08.039 the color and brightness of light doesn't exist outside the 0:06:08.040 --> 0:06:10.719 experience of the observer. We only see light as a 0:06:10.720 --> 0:06:13.200 certain color because of how it stimulates the cones in 0:06:13.200 --> 0:06:16.479 our eyes and how our brain interprets those signals. Well, 0:06:16.520 --> 0:06:18.279 that's a good point, but it's also kind of a 0:06:18.400 --> 0:06:21.520 terrifying mean. It means the external world is really just 0:06:21.600 --> 0:06:25.320 as invisible as a UV ray, because outside of human observation, 0:06:25.360 --> 0:06:28.320 there is no color or brightness. It's just this mix 0:06:28.320 --> 0:06:32.039 of different invisible energy pulses. Actually, by the way, that 0:06:32.080 --> 0:06:33.760 this is off topic, but did you read about the 0:06:33.760 --> 0:06:36.560 women that supposedly have four cones in their eyes instead 0:06:36.600 --> 0:06:39.440 of three, and as a result, they can see hundreds 0:06:39.440 --> 0:06:43.680 of millions of color. That's a wild Yeah, they're called tetrachromats. 0:06:43.760 --> 0:06:46.840 But baby, we're clinging too tightly to the human experience. 0:06:46.880 --> 0:06:49.039 And you know, I actually did some digging to see 0:06:49.040 --> 0:06:51.440 if there were any animals whose vision best ours in 0:06:51.560 --> 0:06:54.440 terms of light perception, and it turns out there quite 0:06:54.440 --> 0:06:57.400 a few that put the invisible spectrum to pretty good use. Awesome, 0:06:57.440 --> 0:06:59.640 So give me the load down. Well, one case where 0:06:59.640 --> 0:07:01.640 plenty of animals have a speed is the ability to 0:07:01.680 --> 0:07:06.680 perceive ultra violet light. Invisible UV radiation is all around us. 0:07:07.040 --> 0:07:09.280 And while it's useful for getting a golden tan, it's 0:07:09.360 --> 0:07:12.080 also a menace because exposure to it can lead to 0:07:12.120 --> 0:07:15.920 melanoma and other illnesses. But that hasn't stopped some animals 0:07:15.920 --> 0:07:18.920 from making the most of UV light. There's some species 0:07:18.920 --> 0:07:20.960 of birds that have plumage that you know, to our 0:07:21.000 --> 0:07:23.960 eyes look the same between males and females. But if 0:07:24.000 --> 0:07:26.600 your vision allows you to see the UV range like 0:07:26.680 --> 0:07:28.360 those birds are able to see it, you know you'd 0:07:28.360 --> 0:07:31.240 be able to make out the uvy markings that distinguish them. 0:07:31.640 --> 0:07:33.640 So those markings make it easier for the birds to 0:07:33.680 --> 0:07:36.520 find a meh definitely, but that's actually only part of it. 0:07:36.840 --> 0:07:39.520 Some other birds determine which chicks to feed based on 0:07:39.560 --> 0:07:42.520 how much UV light you know their heads reflect. For 0:07:42.560 --> 0:07:45.000 whatever reason, the heartier birds tend to have a shinier 0:07:45.040 --> 0:07:47.800 crest than their weaker siblings, so when the mama bird 0:07:47.840 --> 0:07:50.600 has limited food to share, she'll go with whomever has 0:07:50.640 --> 0:07:53.640 the most shine. There's also the fact that urine and 0:07:53.680 --> 0:07:56.200 feces of mice and other small prey are visible in 0:07:56.240 --> 0:07:59.400 the ultraviolet range, so birds that are sensitive to UV 0:07:59.560 --> 0:08:02.600 light can use these traces to track their prey even 0:08:02.640 --> 0:08:05.040 in a place where everything is uniform in color, you know, 0:08:05.080 --> 0:08:07.920 like a green field or something like that. But you know, 0:08:08.000 --> 0:08:10.280 birds aren't the only ones that can do this. You 0:08:10.280 --> 0:08:13.520 have rodents and bats and even some marsupials that can 0:08:13.560 --> 0:08:17.320 see UV light for similar reasons. So I actually think 0:08:17.320 --> 0:08:20.360 I read something about butterflies also having great ev perception, 0:08:20.400 --> 0:08:22.600 and I think they use it to identify which flowers 0:08:22.640 --> 0:08:25.320 are currently producing nectar based on the color of the 0:08:25.360 --> 0:08:27.480 petals or something. Well, yeah, I'm glad you mentioned that, 0:08:27.480 --> 0:08:31.040 because butterflies with a high sensitivity light are often considered 0:08:31.040 --> 0:08:34.599 to have the widest visual range of any form of wildlife. 0:08:35.160 --> 0:08:37.760 It's crazy the invisible world might be the most visible 0:08:37.800 --> 0:08:41.320 to butterflies of all things. But before we move on, 0:08:41.360 --> 0:08:43.400 there's one last animal I want to talk about, and 0:08:43.440 --> 0:08:47.160 that's the reindeer. So I'm sure there's a Rudolph joke 0:08:47.200 --> 0:08:51.480 in here somewhere, but not telling reindeer can see ev risk. Well, 0:08:51.520 --> 0:08:54.080 it sounds strange at first, but reindeer of evolved to 0:08:54.080 --> 0:08:57.000 take full advantage of the ultraviolet range. And they're not 0:08:57.040 --> 0:08:59.480 the only ones. There are other Arctic mammals who make 0:08:59.520 --> 0:09:01.800 their home at the Earth's polls, and they have to 0:09:01.840 --> 0:09:04.560 deal with much higher levels of UV light. Yeah, the 0:09:04.559 --> 0:09:06.920 thinning ozone layer doesn't block as many rays as it 0:09:07.080 --> 0:09:10.200 used to, especially in those upper latitudes. Yeah, exactly. So 0:09:10.240 --> 0:09:12.640 there was this study of the University College of London 0:09:12.720 --> 0:09:15.680 and the University of Tromso in Norway, and they found 0:09:15.720 --> 0:09:18.719 evidence that not only a reindeer resistant eye damage from 0:09:18.720 --> 0:09:22.280 intense UV rays, they're also able to see UV light 0:09:22.559 --> 0:09:25.160 and this helps them find food and avoid predators. And 0:09:25.559 --> 0:09:29.000 in the winter, reindeer primarily do two things. They eat 0:09:29.040 --> 0:09:31.880 lichen and they try to avoid being eaten by wolves. 0:09:31.960 --> 0:09:34.320 And wouldn't you know it, lichen and the fur of 0:09:34.360 --> 0:09:38.640 wolves both absorb UV light. So because snowy landscape strongly 0:09:38.679 --> 0:09:41.800 have reflect UV rays, you got reindeer that can spot 0:09:41.880 --> 0:09:45.120 lichen and wolves with ease. Yeah. That's really cool, And well, 0:09:45.160 --> 0:09:47.079 I think you and I could nerd out on reindeer 0:09:47.120 --> 0:09:50.280 facts for a while, Like how Norwegian scientists wanted to 0:09:50.280 --> 0:09:52.480 get closer to reindeers so they could study them better, 0:09:52.520 --> 0:09:55.920 So they wore polar bear costumes and did that work. No, 0:09:56.120 --> 0:09:58.680 not at all, like it's scared off the reindeer. But 0:09:59.120 --> 0:10:02.760 they also wrote a scientific paper on reindeers reactions to costumes, 0:10:02.880 --> 0:10:06.120 and we're hoping to redo the study with better costumes, 0:10:06.120 --> 0:10:07.880 like like a clown costume. I like how they just 0:10:07.920 --> 0:10:10.160 went off track there, Like that didn't work, So let's 0:10:10.160 --> 0:10:12.880 just do costumes. How about clowns? How about police officers? 0:10:12.960 --> 0:10:15.000 Science is great, but what I was saying was I 0:10:15.040 --> 0:10:16.960 think we should shift the topic a little. All right, well, 0:10:16.960 --> 0:10:18.319 what do you what do you want to talk about? 0:10:18.480 --> 0:10:21.880 Secret messages? So last year a group of scientists and 0:10:21.880 --> 0:10:24.480 friends developed a special kind of paper that can carry 0:10:24.520 --> 0:10:27.280 secret messages. It looks just like plain old paper, but 0:10:27.400 --> 0:10:30.400 you can use different wavelengths of UV light to read, write, 0:10:30.480 --> 0:10:33.200 or even erase the messages that can't be seen invisible light. 0:10:33.360 --> 0:10:36.040 So how does that work? So apparently the paper has 0:10:36.080 --> 0:10:39.679 this special kind of molecule bonded to its cellulose fibers 0:10:39.720 --> 0:10:42.600 that reacts and turns fluorescent when exposed to UV light. 0:10:42.960 --> 0:10:44.840 The idea is you can write messages on the paper 0:10:44.920 --> 0:10:47.360 using a stencil to produce dark and bright areas that 0:10:47.400 --> 0:10:50.760 react differently under the UV lamp. But the really cool 0:10:50.800 --> 0:10:54.520 thing is that the process is completely reversible. You can 0:10:54.600 --> 0:10:57.160 expose the used paper to a shorter wavelength of UV 0:10:57.320 --> 0:11:00.040 light that erases the message completely, and that way of 0:11:00.080 --> 0:11:02.280 paper can be used over and over. I mean, it 0:11:02.400 --> 0:11:05.320 is kind of cool, but what's the advantage over you know, 0:11:05.360 --> 0:11:08.600 the disappearing reappearing and visible length that our kids play 0:11:08.640 --> 0:11:10.400 with and stuff like that. So why is this better 0:11:10.440 --> 0:11:12.680 than that? So not only are the messages on this 0:11:12.720 --> 0:11:16.160 paper undetectable under visible light, they also can't be dissolved 0:11:16.200 --> 0:11:19.120 with other chemicals. So it's the super useful tool in 0:11:19.200 --> 0:11:23.480 anti counterfeiting and tracking operations. A good job, France, you know. 0:11:23.520 --> 0:11:25.640 I actually want to dive into some of the historical 0:11:25.640 --> 0:11:29.560 obsession with invisibility and the ridiculous potions humans used to make. 0:11:30.080 --> 0:11:31.640 But before we do that, how about we check in 0:11:31.640 --> 0:11:33.240 with Bob Burman and see if he can tell us 0:11:33.240 --> 0:11:35.800 a little about the cool properties of light and how 0:11:35.880 --> 0:11:41.880 humans have managed to turn something invisible to our advantage. 0:11:42.520 --> 0:11:45.480 So in this episode on All Things Invisible, we've been 0:11:45.480 --> 0:11:47.920 talking a little bit about this great book, Zapped, and 0:11:48.000 --> 0:11:51.160 we're really lucky to have one America's top astronomy writers 0:11:51.160 --> 0:11:53.160 on with us and the author of this book. It's 0:11:53.480 --> 0:11:56.640 Zapped From infrared to X rays, The Curious History of 0:11:56.679 --> 0:12:00.439 invisible Light. Bob Berman, Welcome to part time genius. Thank 0:12:00.480 --> 0:12:02.240 you great to be here. All right, well let's just 0:12:02.280 --> 0:12:04.800 start with the basics. So can you explain to us 0:12:04.880 --> 0:12:08.880 where light comes from. Well, all lights, except for gamma rays, 0:12:08.880 --> 0:12:13.719 comes from one source only, and that is atoms. If 0:12:13.720 --> 0:12:18.319 the atomy gets excited in any way, electricity, collisions, anything 0:12:18.360 --> 0:12:21.200 can may be excited, madam, so that the electrons are 0:12:21.200 --> 0:12:24.240 In the case of hydraten, it's only got one electron 0:12:24.679 --> 0:12:28.280 jumps to a higher orbit because it's excited. It really 0:12:28.280 --> 0:12:30.440 doesn't like to be there. So in a fraction of 0:12:30.440 --> 0:12:35.160 the second, it'll tumble down closer to its nucleus, and 0:12:35.320 --> 0:12:39.080 that is what causes any kind of light. And the 0:12:39.120 --> 0:12:42.400 distance that it tumbles down determines the color of the 0:12:42.520 --> 0:12:47.720 light and therefore whether it's visible or invisible. So I 0:12:47.760 --> 0:12:49.920 know you talk about this in your book, but what 0:12:49.960 --> 0:12:52.760 did ancient people think about light? And were they aware 0:12:52.760 --> 0:12:56.840 of invisible light? They felt about light as at first 0:12:57.600 --> 0:13:01.040 something that comes from the eye, and then later on 0:13:01.200 --> 0:13:04.800 as an interaction between a beam from the eye and 0:13:05.160 --> 0:13:08.240 external objects. So they got it wrong for a long time. 0:13:08.920 --> 0:13:12.760 They realized that it involves something very fast speed, but 0:13:13.400 --> 0:13:18.760 nothing more than that, and nobody foresaw invisible light until 0:13:19.000 --> 0:13:22.320 the time of the Renaissance of the Middle Ages. It 0:13:22.440 --> 0:13:26.040 was one of those things that no wise person or 0:13:26.160 --> 0:13:31.520 Greek philosopher, or scientists or religious order, nobody came up 0:13:31.559 --> 0:13:34.320 with the idea that there might be kinds of light 0:13:34.480 --> 0:13:38.199 out there that our eyes can't see well. In the Renaissance, 0:13:38.200 --> 0:13:40.520 as you mentioned, you know, with this idea of invisible 0:13:40.600 --> 0:13:44.080 light being a possibility, how did this start to be discovered? Well, 0:13:44.080 --> 0:13:47.400 it's really William Herschel who found the first kind. He 0:13:47.520 --> 0:13:51.720 projected sunlight through a prism piece of cut glass onto 0:13:51.720 --> 0:13:55.839 a tabletop, so you had the whole rainbow of colors. 0:13:56.040 --> 0:13:59.200 And then he put a thermometer in each color, and 0:13:59.280 --> 0:14:01.920 he had other themometers on the side in the darkness 0:14:02.640 --> 0:14:06.080 to act as controls. And so he noticed that when 0:14:06.120 --> 0:14:08.360 the thermometer was in the blue or the green part 0:14:08.360 --> 0:14:11.720 of the spectrum, the temperature went up very little. In 0:14:11.760 --> 0:14:13.840 the yellow and went up more, and the red they 0:14:13.880 --> 0:14:16.720 went up still more. But then he took a break, 0:14:17.679 --> 0:14:20.200 and when he came back some minutes later, the sun 0:14:20.200 --> 0:14:23.640 had moved across the sky, so the spectrum on the 0:14:23.680 --> 0:14:27.600 table had shifted, and now his thermometer on the table 0:14:27.720 --> 0:14:31.280 was no longer in the visible light instead of was 0:14:31.280 --> 0:14:35.720 sitting in a spot of darkness outside of the spectrum, 0:14:35.800 --> 0:14:37.600 just beyond the red end of the spectrum. And he 0:14:37.680 --> 0:14:40.480 looked down on it, and now the thermometer was crazy. 0:14:40.520 --> 0:14:45.560 Who had it was registering much more heat than any 0:14:45.640 --> 0:14:50.440 color did. And so he repeated this and he realized 0:14:50.520 --> 0:14:53.760 that the blank spot beyond the red part of the 0:14:53.800 --> 0:14:58.720 spectrum was heat, was producing more heat. Well, he realized 0:14:58.720 --> 0:15:01.040 it had to be an invisible kind of light that 0:15:01.160 --> 0:15:06.160 was creating the heat. And he called these calorific rays. 0:15:06.240 --> 0:15:09.280 Later on we came to call it infrared. So that 0:15:09.400 --> 0:15:13.480 was the first kind of invisible light ever discovered. Wow. Wow. 0:15:13.480 --> 0:15:15.600 And you also talked in the book about the discovery 0:15:15.720 --> 0:15:18.920 of of X rays and I'm curious what the you know, 0:15:18.960 --> 0:15:22.440 the public response was to this discovery. Well, X rays, Yeah, 0:15:22.440 --> 0:15:26.680 that changed the world too. That was Renkin, and he 0:15:26.840 --> 0:15:29.800 was boy. He had fame, and he would have had 0:15:29.840 --> 0:15:32.600 fortune too if he had patented it, but he didn't. 0:15:33.600 --> 0:15:36.440 Generously just allowed the world to use it, and almost 0:15:36.720 --> 0:15:41.200 right away people realized the value in medicine that you 0:15:41.240 --> 0:15:43.880 could use X rays and find a bullet wear a 0:15:43.920 --> 0:15:47.000 bullet was my body for someone who had been shot 0:15:47.200 --> 0:15:51.240 or were broken, bones were broken, And but nobody knew 0:15:51.280 --> 0:15:53.960 at the time that X rays also had a dark side, 0:15:54.680 --> 0:15:57.160 that it could produce harm as well as benefits. What 0:15:57.280 --> 0:16:00.160 new opportunities for the use of invisible light are the 0:16:00.200 --> 0:16:04.160 horizon and things like medicine or technology or culture, well 0:16:04.240 --> 0:16:07.360 everywhere you know, we use that more than visible light 0:16:07.680 --> 0:16:13.240 these days. Everybody knows about microwaves and used in for 0:16:13.880 --> 0:16:17.600 not just our ovens, but for broadcasting on the GPS 0:16:17.680 --> 0:16:20.000 signals that come down to us from the radio part 0:16:20.000 --> 0:16:23.040 of the spectrum. Really the microwave part of the spectrum. 0:16:23.120 --> 0:16:25.840 So whenever we use our GPS in our cars, or 0:16:25.920 --> 0:16:29.520 when when we're on a camping trip, or use our 0:16:29.600 --> 0:16:33.320 cell phones, those are all parts of the radio spectrum. 0:16:33.480 --> 0:16:36.520 And then we know about the infrared. We use heat labs, 0:16:36.600 --> 0:16:41.080 we use garage door openers, that are they're using infrared 0:16:41.120 --> 0:16:45.440 and ultra violet. That's boy, that's the one with the 0:16:45.480 --> 0:16:49.120 two edged sword. Ultra violet is both the most dangerous 0:16:49.320 --> 0:16:53.480 form and the most valuable for our health. And what 0:16:53.640 --> 0:16:56.840 makes UV rays so harmful to us, Well, they're the 0:16:56.920 --> 0:17:00.760 beginning of the part of the spectrum that has the 0:17:00.800 --> 0:17:04.440 power to ionize and others to strip electrons from adams 0:17:04.880 --> 0:17:09.680 and therefore to change genes, to change chromosomes, to alter DNA, 0:17:10.720 --> 0:17:13.720 and that could give rise to cancer, and it does 0:17:13.840 --> 0:17:18.080 the eight thousand or so melanoma deaths per year. Skin 0:17:18.200 --> 0:17:24.399 cancer are caused by generally too much UV, usually from 0:17:24.440 --> 0:17:29.399 from from a bad sudden burn in our youth. And uh, 0:17:29.600 --> 0:17:33.240 and that's why people nowadays know that they should be 0:17:33.240 --> 0:17:37.120 putting on sunscreen and wearing hats and stuff like that. 0:17:37.640 --> 0:17:41.199 But bad thing has happened from that too, in that 0:17:42.000 --> 0:17:46.320 we've now blocked so much of the UV. That's strange 0:17:46.359 --> 0:17:50.000 things are happening to our bodies that that most even 0:17:50.119 --> 0:17:53.399 doctors are not aware of, although many are like like, 0:17:53.400 --> 0:17:58.399 like what you do have some examples of this? Yeah, yeah, 0:17:58.480 --> 0:18:00.919 and this has started. If I could give just a 0:18:00.960 --> 0:18:03.240 bit of background, There was a time, of course, when 0:18:03.280 --> 0:18:06.080 we were an agricultural society and we were out of 0:18:06.600 --> 0:18:08.720 doors a lot, and we got plenty of sunlight and 0:18:08.760 --> 0:18:12.199 therefore plenty of ultravolet, which is a few percent of 0:18:12.240 --> 0:18:15.600 the sunlight and stimulates our bodies to produce U V 0:18:17.080 --> 0:18:21.280 a vitamin D very quickly. That UV induced vitamin D 0:18:21.840 --> 0:18:27.600 is such a avalanchingly fast process that we get more 0:18:27.760 --> 0:18:30.320 U V from twenty minutes in the strong sunlight then 0:18:30.359 --> 0:18:34.280 you would from drinking two hundred glasses of milk. So 0:18:34.359 --> 0:18:40.440 somehow our bodies want lots of vitamin D production from UV. 0:18:40.720 --> 0:18:44.480 It's a natural thing. But as we moved indoors to 0:18:44.560 --> 0:18:48.880 be a manufacturing society, and then starting in the fifties 0:18:48.880 --> 0:18:51.760 and sixties had air conditioning so that we didn't have 0:18:51.880 --> 0:18:55.320 to open windows, and glass blocks UV and so it 0:18:55.520 --> 0:18:59.280 blocks the vitamin D production on our skin. And then 0:18:59.640 --> 0:19:02.960 worst of all, this is something that they Vitamin D 0:19:03.119 --> 0:19:06.119 Council talks about a lot because the doctors there, like 0:19:06.240 --> 0:19:10.600 John Cannell like are really getting frustrated with the fact 0:19:10.640 --> 0:19:14.359 that we've turned into kind of a race of of 0:19:14.600 --> 0:19:18.600 of mold people where we're blocking the sun entirely and 0:19:18.640 --> 0:19:21.480 not getting enough sunlight. They see it that it wasn't 0:19:21.480 --> 0:19:24.040 that many decades ago. The kids after school. Of course, 0:19:24.080 --> 0:19:26.919 during school they're not getting any UV and therefore not 0:19:27.000 --> 0:19:30.280 producing any vitamin D. But after school kids used to 0:19:30.320 --> 0:19:34.160 play outdoors and parents used to say, yeah, come back 0:19:34.200 --> 0:19:37.439 at dinner time, and between they'd be out doing whatever 0:19:37.480 --> 0:19:40.960 in the playground or climbing trees, and then that changed, 0:19:41.600 --> 0:19:44.800 so their UV levels in their and their blood has 0:19:44.880 --> 0:19:47.840 dropped to really, really low levels. So what does this 0:19:47.960 --> 0:19:52.480 do is turns out that u V is one of 0:19:52.480 --> 0:19:57.959 the strongest prevent ers of cancer. It stops cancers from growing, 0:19:58.640 --> 0:20:02.320 so when they're tiny, pre detectable tumors, they don't get 0:20:02.359 --> 0:20:05.480 any bigger. This year, for example, it was found that 0:20:05.600 --> 0:20:13.840 pancreatic cancer is prevented by by adequate vitamin D triggered 0:20:13.880 --> 0:20:16.960 by ultra violet light. So there are a lot of 0:20:17.240 --> 0:20:22.840 health benefits also psychological benefits in terms of treatment for 0:20:23.000 --> 0:20:26.840 depression and and things like that. If you get enough 0:20:27.600 --> 0:20:33.959 sunlight induced h vitamin D, it's hard to strike that 0:20:34.000 --> 0:20:37.840 strike that perfect balance. Now you're so right. At the 0:20:37.880 --> 0:20:40.320 same time, you don't want to burn. So the people 0:20:40.400 --> 0:20:44.120 like Dr Canell in the Vitamin D Council, they say 0:20:44.160 --> 0:20:46.440 that we should get as much sun as we can 0:20:47.080 --> 0:20:53.400 without burning, because everybody is so different and how much 0:20:53.440 --> 0:20:56.320 sun they can handle before they start to burn. You know, 0:20:56.480 --> 0:21:01.000 blue eyed, blonde people tend to burn fast, and camp 0:21:01.320 --> 0:21:03.840 shouldn't get as much. Well, there are a thousand other 0:21:03.920 --> 0:21:06.879 questions we could ask. This such a fascinating book. I 0:21:06.920 --> 0:21:09.440 hope all of our listeners will check out zapp. But Bob, 0:21:09.480 --> 0:21:11.520 thanks so much for joining us on Part Time Genius. 0:21:11.800 --> 0:21:27.200 It's been a pleasure. Thanks so much. You're listening to 0:21:27.240 --> 0:21:29.600 Part Time Genius and we're talking about the peculiar allure 0:21:29.640 --> 0:21:32.720 of turning invisible, So mego. We mentioned at the top 0:21:32.760 --> 0:21:34.560 of the show that humans have been obsessed with the 0:21:34.640 --> 0:21:37.399 idea of invisibility from millennia, so I thought it might 0:21:37.400 --> 0:21:38.560 be fun to take a look at some of the 0:21:38.600 --> 0:21:41.760 weirdest attempts to go invisible that people have tried all 0:21:41.760 --> 0:21:44.560 over the years. Yeah, so I'm definitely game. I spent 0:21:44.680 --> 0:21:47.320 some time looking up medieval recipes and spells to turn 0:21:47.359 --> 0:21:51.240 yourself invisible, and as you might guess, they're insane. So 0:21:51.920 --> 0:21:54.199 one of my favorites is from the Ashmole, which is 0:21:54.280 --> 0:21:58.560 this anonymous fifteenth century manuscript that collected over a hundred 0:21:58.600 --> 0:22:02.479 eighty magical and magical recipes in English and Latin. So 0:22:02.520 --> 0:22:05.600 this is the invisibility spell. It goes, if you wish 0:22:05.640 --> 0:22:08.320 to be invisible, take a dead dog and bury it, 0:22:08.480 --> 0:22:11.120