Speaker 1: Welcome to tech Stuff, a production of I Heart Radios
Speaker 1: How Stuff Works. Hey there, and welcome to tech Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with
Speaker 1: iHeart Radio and a love of all things tech, and
Speaker 1: inspired by my last episode about smoke detectors, I thought
Speaker 1: I would do an episode about radiation and radiation detectors.
Speaker 1: And I want to define terms like radiation and radioactivity,
Speaker 1: to talk about the different types of radiation there are,
Speaker 1: and to differentiate between ionizing and non ionizing radiation and
Speaker 1: chat about the technology around it. So first, what is radiation. Well,
Speaker 1: it's a fairly broad term with lots of different meanings
Speaker 1: as it turns out, but I think that's part of
Speaker 1: why there's frequently a lot of confusion around the concept
Speaker 1: of radiation. But there are a couple of definitions that
Speaker 1: for our purpose as we want to focus on, and
Speaker 1: really the one that we're truly interested in is the
Speaker 1: process of admitting radiant energy in the form of waves
Speaker 1: or particles as a definition I took from the Miriam
Speaker 1: Webster Dictionary. By the way, so radiation can involve electromagnetic
Speaker 1: waves or it might involve sub atomic particles. Uh, some
Speaker 1: radiation has the potential to be harmful, even deadly in
Speaker 1: sufficient intensities and length of exposure. Some radiation is relatively safe,
Speaker 1: particularly under specific controls. So let's start with some early
Speaker 1: discoveries of electro magnetic radiation, as those predate our understanding
Speaker 1: of particle based radiation. So our story begins in eighteen
Speaker 1: hundred with an early scientist named William Herschel. And Willie
Speaker 1: was interested in learning more about the spectrum of light,
Speaker 1: and it was already understood that if you were to
Speaker 1: pass light through a prism, you could separate light into
Speaker 1: different colors. You know, the good old roy g BIV spectrum,
Speaker 1: which stands for red, orange, yellow, green, blue, indigo, and violet.
Speaker 1: The spectrum will always be in that order. Anytime you
Speaker 1: pass light through a prism, it's going to break into
Speaker 1: those bands in that order, and those bands actually represent
Speaker 1: bands of frequencies of light waves. Herschel was wondering if
Speaker 1: the different colors of light produced different amounts of heat,
Speaker 1: So is one type of light warmer than another, So
Speaker 1: he set up a system in which he positioned thermometers
Speaker 1: at each color displayed from light passing through a prism.
Speaker 1: So he sets up a prism in his window, lights
Speaker 1: coming through it, and it's hitting a table, and it
Speaker 1: divides up into different bands of color. He sets the
Speaker 1: thermometers in each band of color, and he happened to
Speaker 1: have an extra thermometer just beyond the red end of
Speaker 1: the spectrum, so it's actually in the dark. It was
Speaker 1: beyond the range of the visible light. He had no
Speaker 1: way of knowing it, but he had, by happy coincidence,
Speaker 1: placed a thermometer right where the infrared band was. And
Speaker 1: we can't see infrared light, but that light does transmit heat.
Speaker 1: In fact, Herschel was surprised to see that it was
Speaker 1: that thermometer, the one that was in the darkness, just
Speaker 1: beyond the red range, that actually registered the highest temperature
Speaker 1: out of all the thermometers he had set out. And
Speaker 1: we often talked about heat radiating outward from a source.
Speaker 1: In eighteen o one, another big thinker named Johann Wilhelm
Speaker 1: Ritter built upon Herschel's experiment. He decided to see if
Speaker 1: perhaps there was anything beyond the other end of the spectrum,
Speaker 1: a k a. The violet end. In fact, he really
Speaker 1: discovered it sort of by accident. Ritter experimented by using
Speaker 1: a substance called silver chloride, and this is a chemical
Speaker 1: that turns black if it's exposed to sunlight. Ritter built
Speaker 1: on the understanding that blue light would produce a greater
Speaker 1: reaction in silver chloride than red light, so he did
Speaker 1: a variation on Herschel's experiment. He again used a prism
Speaker 1: to break the light into bands of color, and then
Speaker 1: within each band of color he placed a vile a
Speaker 1: silver chloride to see if the reactions were different across
Speaker 1: the spectrum of light. He could see that, indeed, the
Speaker 1: reaction did vary across the spectrum. The closer you got
Speaker 1: to the violet side of the spectrum, the more intense
Speaker 1: the reaction was, and it was most evident just beyond
Speaker 1: the violet side, in an area where there was no
Speaker 1: visible light at all. So clearly there was something going
Speaker 1: on on that end of the spectrum. So on the
Speaker 1: red end you were getting some sort of heat which
Speaker 1: we now know is infrared, and on the violet end
Speaker 1: there's something else that was really reacting to silver chloride.
Speaker 1: So Ritter would call this chemical raise, which to this
Speaker 1: very day we don't do anymore. Now today we call
Speaker 1: it ultraviolet light. Herschel and Ritter had made the first
Speaker 1: steps to increase our understanding of the electromagnetic spectrum, of
Speaker 1: which visible light is just one tiny part, and as
Speaker 1: we would build on that understanding, we'd also gain more
Speaker 1: information about what effects these types of radiation can have
Speaker 1: on us. Some of them have very little effect on us,
Speaker 1: some of them can have a drastic effect on us.
Speaker 1: And it would take a lot more time, but we
Speaker 1: would gradually begin to understand that if you look at
Speaker 1: the spectrum, it includes everything from radio waves on one
Speaker 1: extreme end of it to gamma raise on the other
Speaker 1: end of it, and these waves vary in wavelength, frequency,
Speaker 1: and energy. So on one extreme end you've got those
Speaker 1: radio waves. These can have really long wavelengths, measuring hens
Speaker 1: of miles, like sixty two miles or a hundred kilometers
Speaker 1: for wavelengths of certain radio frequencies. So if you had
Speaker 1: a perfectly steady radio wave, like just imagine, it's a
Speaker 1: perfect signal you. If you were to map it out,
Speaker 1: it would be a beautiful sign wave. If you measured
Speaker 1: from the peak at one point to the next peak,
Speaker 1: that's the wavelength. That's what would have been a hundred
Speaker 1: kilometers in distance an enormous wave. The frequency of a
Speaker 1: wave refers to how frequently a specific point on a wavelength,
Speaker 1: you know, like that peak, how frequently you could see
Speaker 1: that point on each wave pass a given reference point
Speaker 1: within a second. So with the longest radio waves at
Speaker 1: the lowest frequencies, you're talking about a frequency of around
Speaker 1: three thousand cycles per second, meaning that in one seconds time,
Speaker 1: three thousand peaks past that given point of reference. Now,
Speaker 1: one thing to keep in mind is that this is
Speaker 1: electromagnetic radiation. An electromagnetic radiation all travels at the same speed,
Speaker 1: that being the speed of light. Now, we do have
Speaker 1: to remember the speed of light isn't a constant across
Speaker 1: all media. It's a constant within each media. So we
Speaker 1: we usually when we're talking about the speed of light,
Speaker 1: we're talking about within the vacuum of space. But if
Speaker 1: light is traveling through an atmosphere or through water or something,
Speaker 1: it actually does travel at a different speed than that
Speaker 1: because it it's all dependent upon the medium. Still, electromagnetic
Speaker 1: radiation travels at that speed. So a wavelength of uh,
Speaker 1: you know, one wavelength of of a radio wave is
Speaker 1: traveling at the speed of light, as is one wavelength
Speaker 1: of gamma radiation. However, because the radio waves are so
Speaker 1: long and the gamma rays are so short in wavelength,
Speaker 1: the frequency has to be different, right. The frequency of
Speaker 1: the radio waves has to be lower than the frequency
Speaker 1: of gamma rays because you get way more gamma rays
Speaker 1: passing within a frame of a second, even though they're
Speaker 1: both traveling at the same speed. All right, That gets confusing, right,
Speaker 1: So I like to explain this with an analogy. Imagine
Speaker 1: you've got two identical straight roads, one lane wide, and
Speaker 1: they're right next to each other. Down one road, you
Speaker 1: have a series of buses, and each bus super long,
Speaker 1: measures eighteen meters in length, traveling down the road at
Speaker 1: fifty KOs per hour, and there's one meter of space
Speaker 1: in between each bus. So bus number one eighteen meters
Speaker 1: long than you have a meter, and a bus number
Speaker 1: two is eighteen meters long than you have a meter.
Speaker 1: That's dangerous, but whatever, they're traveling down at fifty an hour,
Speaker 1: perfectly in sync with each other. On the other road,
Speaker 1: do you have a series of zippy little smart cars
Speaker 1: and each smart car measures just three meters in length.
Speaker 1: They're also going down the road at fifty kilometers per
Speaker 1: hour with a meter of space in between each pair
Speaker 1: of cars. Now, individual vehicles are all traveling at the
Speaker 1: same speed, they're all traveling at fifty kilometers per hour.
Speaker 1: But the smart cars aren't as long as the buses.
Speaker 1: So if you were to have a accounter, there's someone
Speaker 1: standing by the bus lane and there's someone standing by
Speaker 1: the smart car lane, and they're holding a little counter
Speaker 1: in their hands. The person next to the smart cars
Speaker 1: is going to count way more smart cars in the
Speaker 1: same amount of time as the person counting the buses.
Speaker 1: And it's not because smart cars are traveling faster. They're not.
Speaker 1: They're just smaller, so more of them can go by
Speaker 1: within that given amount of time. The same thing is
Speaker 1: true with wavelengths of the electromagnetic spectrum red light, blue light,
Speaker 1: X rays, radio waves. They're all traveling at the same speed.
Speaker 1: They just have different wavelengths, so they have to have
Speaker 1: different frequencies. Now, as I said earlier, in those early
Speaker 1: days in the nineteenth century, we didn't have this level
Speaker 1: of understanding. We weren't aware of different wavelengths and frequencies,
Speaker 1: and we didn't know that longer wavelengths and lower frequencies
Speaker 1: of electromagnetic radiation carry less energy, whereas high frequencies and
Speaker 1: very small wavelengths of electromagnetic radiation can pack way more energy.
Speaker 1: If you were to look at the experiments of Herschel
Speaker 1: and Ritter, you might actually think that that's not the case,
Speaker 1: because the invisible light off the red end of the
Speaker 1: spectrum was carrying a lot of heat. It was heating
Speaker 1: up a thermometer more than the others, so maybe it
Speaker 1: carries more energy. And whereas the violet side you just
Speaker 1: saw silver chloride change color. So it would take a
Speaker 1: lot more experimentation to get a deeper understanding of the
Speaker 1: actual nature of electromagnetic radiation. Now to go into the
Speaker 1: full history of how that understanding would unfold is the
Speaker 1: stuff of college lecture series, So I'll just give very
Speaker 1: brief summaries to get us kind of closer to our objective.
Speaker 1: In the nineteenth century you had numerous scientists and inventors
Speaker 1: who were observing all sorts of interesting stuff that would
Speaker 1: later become integrated into our knowledge of electromagnetism. So Michael
Speaker 1: Faraday did a great deal of work exploring the relationship
Speaker 1: between electric and magnetic fields. For example, his work would
Speaker 1: inspire a Scottish physicist named James Clerk Maxwell to look
Speaker 1: into the matter further, and Maxwell made predictions about electromagnetic
Speaker 1: radiation based on those early experiments and observation, saying, well,
Speaker 1: based on what we know, I expect that will eventually
Speaker 1: find something that fits this mathematical uh example of what
Speaker 1: should be there, and his predictions proved to be accurate,
Speaker 1: and they in turn would serve as an important foundation
Speaker 1: for Albert Einstein's special theory of relativity, as the one
Speaker 1: that gives us the famous equation equals mc squared, which
Speaker 1: tells us that energy and mass are related at an
Speaker 1: intrinsic level. And Maxwell's observations about electromagnetic radiation would lead
Speaker 1: to a theory about heat radiation that in turn would
Speaker 1: be overturned by Max Planck, whose formulation of quantum hypothesis
Speaker 1: to describe how heat radiates would become the predominant one.
Speaker 1: But all of that is a little outside of our scope.
Speaker 1: So the point I wanted to make is that the
Speaker 1: nineteenth century was a boom time for scientific observations and discoveries,
Speaker 1: and the things we would learn would serve us well
Speaker 1: as we moved into the next phase of understanding of radiation.
Speaker 1: And what it's all about. So the other big discoveries
Speaker 1: that relate to this episode came about at the end
Speaker 1: of the nineteenth century, so we get to look at
Speaker 1: both ends of the eighteen hundreds. In eight Vilhelm runjeon
Speaker 1: which I mentioned him in the last episode, he was
Speaker 1: experimenting with a cathode ray tube, and I talked about
Speaker 1: that again in the Smoke Detective episode. Essentially, these are
Speaker 1: devices that produce streams of electrons by heating up a
Speaker 1: filament inside a glass vacuum tube, kind of similar to
Speaker 1: a light bulb. Runjen found that as he applied an
Speaker 1: electric voltage to the cathode ray tube a light detection
Speaker 1: screen in his lab that was made out of barium
Speaker 1: platina cyanide fluorest, it actually lit up. It detected light
Speaker 1: even though there was no visible light there. So he
Speaker 1: began to experiment with this phenomenon, this invisible light that
Speaker 1: was causing this this detector to light up, and that
Speaker 1: included putting objects between the cathode ray tube and the screen,
Speaker 1: and he saw that whatever was coming out of the
Speaker 1: tube seemed to be penetrating through objects and it was
Speaker 1: still hitting the screen on the other side. He found
Speaker 1: that if he put photographic film, the energy would interact
Speaker 1: with the photographic film, and if you put something in
Speaker 1: between the film and the cathode ray tube, he could
Speaker 1: get a really interesting image of it. Uh, it's like
Speaker 1: you could see through certain stuff pretty clearly. So, for example,
Speaker 1: his hand, he put his hand in front of it
Speaker 1: and he took a photo. Then the picture would show
Speaker 1: the skeleton in hand. It would it would show through
Speaker 1: the soft tissues of his hand, and he thought, well,
Speaker 1: this is interesting. He discovered a new type of radiation
Speaker 1: and he called it the X ray because what the
Speaker 1: heck was going to call it? It was an unknown quantity,
Speaker 1: and in mathematics we often refer to unknown quantities as X,
Speaker 1: like solve for X. So it was meant to be
Speaker 1: a placeholder. X rays just it turned into the permanent
Speaker 1: name for the stuff. Now. Initially, no one was aware
Speaker 1: that X ray radiation was potentially dangerous with its shorter
Speaker 1: wavelength and higher frequency and energy than visible light. In fact,
Speaker 1: no one was even sure that was another form of light.
Speaker 1: They thought it might be, but they weren't certain, and
Speaker 1: that wouldn't be proven until nineteen twelve. But people began
Speaker 1: to understand that there was some potential danger the X
Speaker 1: rays fairly early on. In eighteen nineties six, the year
Speaker 1: after Runton's UH discovery, the journal Nature published an article
Speaker 1: with the title The Harmful Effects of X rays. And
Speaker 1: in that article there was a story about a guy
Speaker 1: who had worked as an X ray demonstrator in London,
Speaker 1: and he described the effects of X ray exposure that
Speaker 1: he experienced, particularly on his hands, after working for a
Speaker 1: full summer doing demonstrations with X ray machines for several
Speaker 1: hours a day, I'm going to quote an excerpt. In
Speaker 1: the first two or three weeks, I felt no inconvenience,
Speaker 1: but after a while appeared on the fingers of my
Speaker 1: right hand many dark spots which pierced under the skin,
Speaker 1: and gradually they became very painful. The rest of the
Speaker 1: skin was red and strongly inflamed. My hand was so
Speaker 1: bad that I was constantly forced to bathe it in
Speaker 1: very cold water. An ointment momentarily on the pain. But
Speaker 1: the epidermist had dried up, had become hard and yellow
Speaker 1: like parchment, and completely insensible, so I was not surprised
Speaker 1: when my hand began to peel. From that point, the
Speaker 1: guy goes on to describe how things got even worse,
Speaker 1: like he began to lose fingernails and stuff. But I'm
Speaker 1: gonna leave out the rest of the grizzly details. The
Speaker 1: point is people are starting to notice that the longer
Speaker 1: someone was exposed to X rays, the more severe the
Speaker 1: consequences seemed to be. Short exposures did not appear to
Speaker 1: be as serious, but this was something that people were
Speaker 1: starting to get a little concerned about that would grow
Speaker 1: in the years to come. But first, let's take a
Speaker 1: quick break before we jump into that discussion. Okay, so
Speaker 1: before we took our break, I was talking about how
Speaker 1: people were beginning to understand that X rays could be dangerous.
Speaker 1: That didn't stop early irresponsible implementations of X ray machines. However,
Speaker 1: people thought of these as curiosities. They were things to
Speaker 1: be celebrated and experienced. Thomas Edison thought everyone would have
Speaker 1: one in their own home and thought perhaps they should
Speaker 1: have them, because again, they didn't understand the dangers yet.
Speaker 1: People would even have X ray parties in which guests
Speaker 1: would take X ray photos of themselves, you know, of
Speaker 1: their foot, or their hand, or even their face, and
Speaker 1: they would get to keep the photographs at the end
Speaker 1: of the party. Shoe stores installed X ray fluoroscopes to
Speaker 1: get a look at a person's foot, And while a
Speaker 1: person visiting the store wouldn't likely walk away with a
Speaker 1: lethal dose of radiation, the folks who were working at
Speaker 1: the store were exposed to X rays much more frequently
Speaker 1: and for longer durations, and many of them would suffer
Speaker 1: the consequences. But all of those awful discoveries would take
Speaker 1: some times, so people didn't immediately notice the issues. Meanwhile,
Speaker 1: let's get back to the discovery of radioactivity by talking
Speaker 1: about the other kind of radiation, not the electro magnetic type.
Speaker 1: So in eighteen ninety six, which was that same year
Speaker 1: that the Nature article about the dangers of X rays
Speaker 1: came out, there was a physicist named al Marie Beccarel
Speaker 1: who was wondering if some materials he was working with
Speaker 1: might produce the same sort of energy that Rundgen's X
Speaker 1: rays seemed to create. One of those materials that Beckerel
Speaker 1: was working with was a crystal made up of uranium salts. Now,
Speaker 1: the various materials Beccarel had interest in all shared a
Speaker 1: common trait. They were all phosphorescent, so they could all glow,
Speaker 1: and he wondered if they were giving off the same
Speaker 1: sort of invisible light stuff that run Gen was observing
Speaker 1: with X rays. So Beckarel set up an experiment. He
Speaker 1: put down a photographic plate. He totally covered it so
Speaker 1: that one of it would be exposed to light because
Speaker 1: that would activate the photoreactive chemicals on the plate. And
Speaker 1: on top of the covering he put a selection of
Speaker 1: his phosphorescent crystals to see if any of them would
Speaker 1: interact with the photo reactive chemicals. And he exposed the
Speaker 1: whole thing to the sun, you know, thinking that the
Speaker 1: sun would charge these various crystals. And at the end
Speaker 1: of the experiment he discovered that out of all the
Speaker 1: different things he was testing, only one seemed to have
Speaker 1: any effect at all, and that was the rock crystal
Speaker 1: that was actually made up of uranium salt, and that
Speaker 1: was the only one that seemed to have fogged up
Speaker 1: the the photoplate. So he thought, well, I'll do a
Speaker 1: longer test. I'll leave it out in the sun longer,
Speaker 1: see if I get a bigger, more clear result. But
Speaker 1: the weather at that point wasn't cooperating. It had gotten cloudy,
Speaker 1: so he couldn't put it out in the sun. So
Speaker 1: he takes his photographic plates and his uranium salts and
Speaker 1: he stores them away and waits for the weather to
Speaker 1: get better. So they were actually stored next to each
Speaker 1: other in a dark cabinet. Several days later, as the
Speaker 1: weather was starting to finally clear out, he was getting
Speaker 1: ready to conduct his experiment, but he decided, you know what,
Speaker 1: before I do this, I better make sure these photographic
Speaker 1: plates are still good, because the chemicals can actually expire,
Speaker 1: and I'd be wasting my time if they aren't working anymore.
Speaker 1: So he picks one and develops it, and it happened
Speaker 1: to be one that was close to the iranium salts.
Speaker 1: Rock He was surprised to discover that the bits of
Speaker 1: the photographic plate that had been close to those uranium
Speaker 1: salts had images on them, even though the salts had
Speaker 1: not been exposed to sunlight. They've been stored in a
Speaker 1: dark cupboard, and he concluded that the uranium salts themselves
Speaker 1: were giving off some sort of emission that was being
Speaker 1: captured on this photographic plate. Henri Becarel had a couple
Speaker 1: of enterprising and brilliant assistants. One was Pierre Curie and
Speaker 1: the other was Marie Sklodowska, who would marry Pierre and
Speaker 1: become Marie Curie. She uh really was fascinated by radioactivity,
Speaker 1: and together with her husband, they began to study the
Speaker 1: ranium salts as well as looking for other similar materials
Speaker 1: that seemed to display this radioactive phenomena. They tested some
Speaker 1: mining operation waste. It's called a pitch blend. The mining
Speaker 1: operations were happy to get rid of it because it
Speaker 1: was just run off from their operations, and they found
Speaker 1: that it could contained traces of radioactive material, and eventually
Speaker 1: they were able to separate a small amount of it
Speaker 1: from the rest of the pitch blend, and it would
Speaker 1: later be called radium. It was far more radioactive than
Speaker 1: the uranium salts they had already worked with. The Curies
Speaker 1: and Beckrel would receive the Nobel Prize in Physics for
Speaker 1: their discoveries. Runen also received one earlier for his discovery
Speaker 1: of X rays, and then Pierre Curie would later tragically
Speaker 1: die in a traffic accident. Marie would go on to
Speaker 1: discover another radioact development, this one called polonium, and she
Speaker 1: would receive a second Nobel Prize, though that second one
Speaker 1: was in chemistry. She's one of only a few people
Speaker 1: who have ever received more than one Nobel Prize. Now,
Speaker 1: one thing Beckerel did with his own research was proved
Speaker 1: that the energy coming out of this uranium salt was
Speaker 1: not the same thing as X rays, and he did
Speaker 1: this by testing the uranium salts against X rays with
Speaker 1: a device that could generate a magnetic field. So X
Speaker 1: rays would pass through the magnetic field unimpeded. And that's
Speaker 1: because X ray radiation has no electric charge, and thus
Speaker 1: it has no magnetic field of its own, so it's
Speaker 1: not affected by magnetic field. It just passes through. Is
Speaker 1: that there's nothing else there but the radiation coming from
Speaker 1: the uranium salts bent upon encountering the magnetic field, and
Speaker 1: that told Beckarel that whatever was coming out of the
Speaker 1: uranium salts had an electric charge to it, because it
Speaker 1: had to have an electric charge in or to have
Speaker 1: its own magnetic field and thus be either attracted or
Speaker 1: repelled by the magnetic field and his testing vice. So
Speaker 1: Beckerel tested numerous types of radioactive substances using this approach
Speaker 1: and observed three basic results. Either radiation would bend one
Speaker 1: way using certain radioactive materials, and he would conclude, this
Speaker 1: is a positive radiation material because it is being attracted
Speaker 1: to the negative side of the magnetic field and repelled
Speaker 1: by the positive side, or it would bend the other way,
Speaker 1: so he would have the opposite conclusion. Okay, this is
Speaker 1: negative radiation because it's being attracted to the positive side
Speaker 1: and repelled by the negative side, or it passed straight
Speaker 1: through like X rays, and it would have no electrical
Speaker 1: charge at all, so it would be neutral. So you
Speaker 1: had positive, negative, and electrically neutral radiation. In their work,
Speaker 1: the Curies and Beckarel noted that prolonged exposure to some
Speaker 1: of these radioactive materials would result in injuries and ailments,
Speaker 1: like if you handled some of the more radioactive stuff
Speaker 1: like radium for any length of time, you could actually
Speaker 1: get burns on your skin, and you could suffer radiation sickness,
Speaker 1: which includes symptoms like nausea, but the extent of the
Speaker 1: damage was unknown for years. Marie cry died in nineteen
Speaker 1: thirty four of a plastic anemia, which was probably a
Speaker 1: consequence of her exposure to radioactive material over the years.
Speaker 1: It certainly would have increased the odds of her developing that,
Speaker 1: and that's something that is is good to just mention
Speaker 1: in general is that when we think of radiation, we
Speaker 1: often think of the radiation sickness, the sort of acute
Speaker 1: symptoms you can have if you have a sudden exposure
Speaker 1: to an intense amount of radiation. But in many ways,
Speaker 1: the consequences of exposure to radiation are really more about
Speaker 1: the increased risk of developing UH conditions like cancer. UH.
Speaker 1: And it doesn't necessarily mean that if you do develop cancer,
Speaker 1: that it was a direct result of that exposure to radiation,
Speaker 1: but rather or that the exposure to radiation increased the
Speaker 1: odds that you would develop cancer. It's a complicated thing
Speaker 1: to look at because without knowing all the variables, you
Speaker 1: cannot say conclusively that X caused why, but you can't
Speaker 1: say that X made Y way more likely. That's what
Speaker 1: we think with Currie, that she probably developed a plastic
Speaker 1: anemia as a consequence of this exposure to stuff like
Speaker 1: radium over the years. Many of her belongings and even
Speaker 1: a cookbook she used, are actually stored in shielded containers
Speaker 1: to this day because they're still radioactive dangerously. So the
Speaker 1: lack of understanding about the consequences of radiation exposure would
Speaker 1: have many more nasty consequences, just as it had with
Speaker 1: the X ray fad. For example, because radium is phosphorescent,
Speaker 1: it was seen as a useful material for stuff like
Speaker 1: the hands of watches, like analog watches. He would paint
Speaker 1: an analog watches minute and our hands with radium, and
Speaker 1: that would make it glow in the dark and made
Speaker 1: it really easy to read the time, even if you
Speaker 1: were in low lighting. While the amount of radium on
Speaker 1: these watches was very very small and not likely to
Speaker 1: harm somebody who was wearing the watch, the employees responsible
Speaker 1: for painting the watch hands received way more radiation exposure. Colloquially,
Speaker 1: they were called radium girls, and the management positions at
Speaker 1: these facilities frequently had significant protection from radiation, but the
Speaker 1: same could not be said for the women on the
Speaker 1: front lines, the women actually doing the work painting the
Speaker 1: radium onto these watch hands. It also wasn't uncommon for
Speaker 1: a worker to lick the end of her brush to
Speaker 1: shape it so that she could more easily paint the
Speaker 1: watch hand. So that meant these workers were occasionally depositing
Speaker 1: little amounts of radium directly on their tongues. They were
Speaker 1: ingesting radium. Radium when ingested, will deposit itself in bone,
Speaker 1: much like calcium would, so several of the workers would
Speaker 1: ultimately grow ill with radiation sickness. A group of five
Speaker 1: of them later brought a lawsuit against their company. That
Speaker 1: company was the United States Radium Company. They charged them
Speaker 1: with being irresponsible in areas of health and safety, and
Speaker 1: in turn that prompted a detailed study into what the
Speaker 1: long term effects of radium exposure are and it's awful
Speaker 1: that our knowledge came at such a steep price. At
Speaker 1: the same time, the results of that study would lead
Speaker 1: to massive changes in health and safety regulations for the
Speaker 1: benefit of workers in the United States. From these discoveries,
Speaker 1: physicists began to learn more about the nature of radioactive
Speaker 1: material in general. They observed that there were different kinds
Speaker 1: of radiation beyond just calling it positive, negative, or electrically neutral.
Speaker 1: Some radiation seem to have more penetrative abilities. They could
Speaker 1: penetrate further into solid matter than other types of radiation.
Speaker 1: So you might have one type of radiation that isn't
Speaker 1: able to penetrate solid matter effectively, and another one seems
Speaker 1: to go right through stuff as if there's no problem.
Speaker 1: A physicist named Ernest Rutherford conducted numerous experiments with radioactive
Speaker 1: material and at this point we were beginning to understand
Speaker 1: that radioactivity was a process in which certain materials undergo
Speaker 1: a process called decay, and that is the form that
Speaker 1: they are in. The radioactive form is inherently unstable. You
Speaker 1: can if you want to think of it in terms
Speaker 1: of want, I mean putting motivation is ridiculous because we're
Speaker 1: talking about atomic particles here. But it's a form of
Speaker 1: an atom that does not want to be that form.
Speaker 1: It's unstable. So these materials will spontaneously but not necessary early,
Speaker 1: quickly break apart and give off energy and subatomic particles
Speaker 1: as they decay to a more stable form. Rutherford classified
Speaker 1: three types of radiation. He said this was all based
Speaker 1: off the penetrative properties of radiation, how far they could
Speaker 1: penetrate into matter. The three types he classified were alpha radiation,
Speaker 1: beta radiation, and gamma radiation. Alpha particles had the least
Speaker 1: amount of ability to penetrate matter, and gamma rays were
Speaker 1: the opposite. They could very easily penetrate matter. Upon further study,
Speaker 1: scientists discovered that an alpha particle is relatively massive on
Speaker 1: the atomic scale of things. It actually consists of an
Speaker 1: ejected helium nucleus. A helium nucleus is two protons and
Speaker 1: two neutrons. This is the type of radiation given off
Speaker 1: by a mera sirium to forty one. That's the radioactive
Speaker 1: material that's inside smoke detectors that I talked about in
Speaker 1: the last episode. The ionization chambers have this type of
Speaker 1: radioactive material in them, so you probably have some of
Speaker 1: the stuff in your house right now. Alpha particles are
Speaker 1: not able to penetrate matter very well, and they're big
Speaker 1: enough and slow enough that they can't really get through skin,
Speaker 1: at least not most of the time, so they're not
Speaker 1: likely to have it affects you. Uh. They can't even
Speaker 1: go through very much air. After a couple of inches,
Speaker 1: they've lost the energy to move forward. Breathing in alpha
Speaker 1: particles would be a real risk, and you wouldn't want
Speaker 1: to swallow any of it either, so you don't want
Speaker 1: to come into contact with the stuff, But having it
Speaker 1: enclosed in a smoke detector in its own little chamber
Speaker 1: in the smoke detector is more than enough protection that
Speaker 1: you wouldn't receive any sort of significant radiation exposure from
Speaker 1: the ameer sirium inside a smoke detector. You would receive
Speaker 1: way more if you just went outside for a few hours.
Speaker 1: So it's not that big. It's it's it's like background
Speaker 1: levels of radiation UM. Beta particles are lighter than alpha particles,
Speaker 1: and they move fast. They're actually ejected electrons. They can
Speaker 1: travel further than alpha particles through the air. An alpha particle,
Speaker 1: like I said, I can only move a couple of inches,
Speaker 1: but beta particles can move several feet. They're also moderately penetrating.
Speaker 1: They can pass through human skin, at least under the
Speaker 1: surface level of human skin, So if you're in contact
Speaker 1: with beta emitting material for a prolonged amount of time,
Speaker 1: you could suffer a skin injury like a skin burn. UH.
Speaker 1: Stuff that emits beta radiation includes carbon fourteen, sulfur thirty five,
Speaker 1: and strontium ninety UH. Those numbers at the ends of
Speaker 1: those names are important that designates isotopes. Isotopes are forms
Speaker 1: of an atom that have a different number of neutrons,
Speaker 1: but of course they have the same number of protons
Speaker 1: and electrons. If you start having different number of protons,
Speaker 1: then you end up with a different element. So the
Speaker 1: most common form of carbon is carbon twelve. Carbon twelve
Speaker 1: has six proto ons and six neutrons, but you can
Speaker 1: also find carbon fourteen that has six protons and eight neutrons,
Speaker 1: but it's unstable. It will undergo radioactive decay over time,
Speaker 1: so it will spontaneously decay and give off beta emissions.
Speaker 1: Gamma radiation, like X ray radiation, is a form of
Speaker 1: electromagnetic radiation. If you were to look at the full
Speaker 1: spectrum of electromagnetic radiation, radio waves are on one end
Speaker 1: with a very long, low frequency low energy waves. Gamma
Speaker 1: rays are on the opposite, so this is the very
Speaker 1: very very short wavelengths incredibly high frequencies. They pack a
Speaker 1: ton of energy in them. X rays are slightly less energetic,
Speaker 1: but there are still far more powerful than visible light,
Speaker 1: which is why they can penetrate through solid objects better
Speaker 1: than visible light could, and gamma rays are even better
Speaker 1: at it than X rays are. These rays are electrically neutral,
Speaker 1: so magnetic fields won't cause them to change their paths.
Speaker 1: They'll just keep going straight. They can travel many feet
Speaker 1: through the air. They can penetrate several inches into human tissue.
Speaker 1: In fact, it requires significant shielding to protect against gamma radiation.
Speaker 1: Radium two twenty six amidst gamma radiation, as do several
Speaker 1: other radioactive materials, And this is really dangerous stuff. It
Speaker 1: will not turn you into the Incredible Hulk, but it
Speaker 1: might cause nasty, nasty problems for you. Now, in addition
Speaker 1: to all these observations and the growing realization that some
Speaker 1: forms of radioactivity posed a serious health hazard to humans,
Speaker 1: scientists discovered that these forms of radiation would interact with
Speaker 1: other particles and ionize them. That is, when the interaction
Speaker 1: would happen, the particles would have electrons split off of them,
Speaker 1: and by particles, I'm really talking about atoms and molecules,
Speaker 1: I shouldn't use the word particle. I should say these
Speaker 1: atoms are molecules. When they would encounter this kind of radiation,
Speaker 1: they would have electrons stripped away, and the remaining molecule
Speaker 1: or atom would end up having a net positive charge
Speaker 1: because it just lost electrons. Electrons have a negative charge.
Speaker 1: Were referred to this general type of radiation as ionizing radiation.
Speaker 1: It has created ions. Not all radiation is ionizing. Radio
Speaker 1: waves for example, are not ionizing radiation, nor are microwaves
Speaker 1: or visible light. These types of radiation don't have enough
Speaker 1: energy to ionize other particles, and it's why it's safe
Speaker 1: for us to broadcast radio waves and to walk around
Speaker 1: with radio waves going all over the place. They don't
Speaker 1: affect us, we don't interact with them. Makes sense that
Speaker 1: we would evolve in such a way where the radio
Speaker 1: waves wouldn't affect us. This is why if you were
Speaker 1: to live next to a cell phone tower, you would
Speaker 1: not receive harmful radiation in the form of ionizing radiation,
Speaker 1: because that's not the type that cell phone towers can emit. Uh,
Speaker 1: they just don't pack the punch at ionizing radiation like alpha,
Speaker 1: beta and gamma radiation as a different story, That stuff
Speaker 1: really can mess us up, and for that reason, it's
Speaker 1: a good thing to be able to detect it so
Speaker 1: that we can remove ourselves or the radioactive material from
Speaker 1: the environment that otherwise would pose a real threat to
Speaker 1: our long term health. So when we come back, I'll
Speaker 1: talk more about what is actually going on with the
Speaker 1: radioactive interactions in our bodies, as well as the device
Speaker 1: used to detect it, and it's typically called a Geiger counter.
Speaker 1: But we'll be right back and I'll talk about then. Okay,
Speaker 1: So radiation interacting with the human body that ionizing radiation
Speaker 1: can damage the cells in our body. Now, we have
Speaker 1: systems in our body that are really good at repairing damage,
Speaker 1: So it's entirely possible to encounter radiation suffer some damage
Speaker 1: as long as the damage. As long as the radiation
Speaker 1: wasn't so intense and the exposure so extreme that you
Speaker 1: didn't have uh, mortal wounds from acute exposure, you might
Speaker 1: very well recover without any issue. But radiation can damage
Speaker 1: the d n A inside ourselves, and occasionally that can
Speaker 1: lead to other big problems, such as the development of cancer,
Speaker 1: which is why we say exposure to radiation increases your
Speaker 1: risk of developing cancer. It doesn't necessarily mean that we
Speaker 1: can easily draw a line from exposure to development, but
Speaker 1: we certainly know that it increases your risk of developing it.
Speaker 1: It could be the reason that someone develops cancer. But
Speaker 1: there's so many variables it's impossible to say in any
Speaker 1: you know, given case, uh, specific cases, you might be
Speaker 1: able to trace it down, but now in general, you
Speaker 1: can't just easily make that that conclusion. It is clear
Speaker 1: that acute exposure to high levels of of ionizing radiation
Speaker 1: will cause injury and sickness and increase risk of more
Speaker 1: serious health problems further down the line. So we want
Speaker 1: to be able to detect that stuff early before we
Speaker 1: risk having a longer exposure to it. Radiations invisible frequently
Speaker 1: exposure to lower levels of it could be very harmful,
Speaker 1: but they might not be noticeable. We might not register
Speaker 1: it just from our own personal experience. So how do
Speaker 1: we detect it? And that's where we get to the
Speaker 1: Geiger Counter. It's named after a guy named Hans Geiger Counter.
Speaker 1: Now I'm just kidding, it's actually just Hans Geiger. Some
Speaker 1: people actually call these devices Geiger Mueller counters, because another
Speaker 1: guy named Valter Mueller took Geiger's design and tweaked it
Speaker 1: a bit about two decades after the initial invention of
Speaker 1: the Geiger counter to improve its performance. Some folks just
Speaker 1: shorten this down to GM counters. But Hans Geiger was
Speaker 1: a physicist who worked very closely with Ernest Rutherford, whom
Speaker 1: I mentioned earlier as being the smarty pants who was
Speaker 1: classifying radiation as alpha, beta, and gamma, and Geiger came
Speaker 1: up with a device that initially was meant to detect
Speaker 1: alpha particles. He would eventually expand it so he could
Speaker 1: detect other types of radiation too, and he did it
Speaker 1: with a pretty clever approach. Al Right, so I mentioned
Speaker 1: that these types of radiation have enough energy to ionize
Speaker 1: particles right to create electrically charged particles by stripping away electrons.
Speaker 1: So ions have a net electrical charge there. It's either
Speaker 1: positive or negative in general, but in this case we're
Speaker 1: talking about positive ions. And the movement of electrically charged
Speaker 1: particles has a name. It's electricity. That's what that is.
Speaker 1: So thought Geiger. If I can create a device that
Speaker 1: detects the presence of ions, then it stands to reason
Speaker 1: that something in the area is causing these ions to
Speaker 1: form something like radioactive material over time. Geiger counters, like
Speaker 1: I said, would be able to detect all sorts of
Speaker 1: different types of radiation, but initially it was all about
Speaker 1: alpha radiation. And here's how it would work. A typical
Speaker 1: Geiger counter has a meter that's connected to a wand
Speaker 1: or tube. So the meter is your indicator. The meter
Speaker 1: is what tells you if you get a hit, if
Speaker 1: there's a spike that indicates radiation. Inside the tube or
Speaker 1: the wand is a chamber, and inside the chamber is
Speaker 1: a low pressure gas and typically there's a a window
Speaker 1: made out of plastic on one side of this chamber.
Speaker 1: Also in that same chamber with the low pressure gas
Speaker 1: is a thin metal wire of tungsten. You can almost
Speaker 1: think of it as like the filament on a light bulb,
Speaker 1: and the fire runs to the end of the tube
Speaker 1: that leads into the the cable that in turn attaches
Speaker 1: to the meter, and at the end of that wire
Speaker 1: there is an electrode with a high positive voltage. Now
Speaker 1: the other end of the wire is not connected to
Speaker 1: another contact. There's no complete circuit here, so you just
Speaker 1: have a very high positive voltage on the wire. But
Speaker 1: it creates an electric field between the metal wire and
Speaker 1: the outside of the tube. So if the gas inside
Speaker 1: the tube, this low pressure gas, encounters ionizing radiation, then
Speaker 1: that radiation will strip electrons away from the gas molecules
Speaker 1: inside the chamber. The stripped electrons, because of their negative charge,
Speaker 1: will immediately zap the toungusten wire inside this one because
Speaker 1: again we've applied a strong positive voltage to that wire.
Speaker 1: So the electrons having the negative charge are attracted to
Speaker 1: the positive charge of the tungsten wire. UH This usually
Speaker 1: means that there's a big rush of electrons. As electrons
Speaker 1: are moving, they will bash into other molecules, which will
Speaker 1: strip over other electrons, so you'll get a quick zap.
Speaker 1: Then you typically have to quench the Geiger counter, but
Speaker 1: that really doesn't matter for the rest of this discussion.
Speaker 1: I mean, it matters, but we're gonna focus on how
Speaker 1: this is detecting things. So you get a bunch of
Speaker 1: electrons that hit this tungsten wire that creates a pulse
Speaker 1: of electricity, and the pulse is what feeds through a
Speaker 1: cable that goes to the meter, and the meter registers
Speaker 1: that there's been a pulse of electricity, which means that
Speaker 1: there's been the generation of ions inside this chamber, which
Speaker 1: in turn means you've encountered some sort of ionizing radiation. Uh.
Speaker 1: The wire might also pass the signal through an amplifier.
Speaker 1: The amplifier will increase the power of that signal and
Speaker 1: send it to a loud speaker, and that's where you
Speaker 1: get that clicking noise. So if you've ever seen a
Speaker 1: movie where someone's using a Geiger counter and you're hearing
Speaker 1: a series of clicks, that's because the idea is that
Speaker 1: the wires picking up electric pulses due to ions, and
Speaker 1: then that's being sent to a loud speakers, so that's
Speaker 1: what's making the clicking noise. The beauty of this design
Speaker 1: is that it isolates the ions source from the environment.
Speaker 1: Right the source of the ions is this gas inside
Speaker 1: a chamber. The gas is kept separate from the surrounding environment,
Speaker 1: so you don't have to worry about somehow encountering ions
Speaker 1: out in the wild, Like if you were standing next
Speaker 1: to an ion generator. Let's say you've gotten ionization purifier,
Speaker 1: something that's meant to purify the air in your room,
Speaker 1: you shouldn't get a readoubt from your Geiger counter because
Speaker 1: the ions being generated by this ionization chamber would not
Speaker 1: be interacting with the gas inside the Geiger counters chamber. Instead,
Speaker 1: the only time the gas and the Giger counter should
Speaker 1: be ionizing at all is if you're coming into range
Speaker 1: of ionizing radiation. So dependent upon the intensity of the
Speaker 1: readelts you're getting, you would know kind of how much
Speaker 1: radiation you were experiencing at any given moment. And again,
Speaker 1: radiation exposure on its own does not immediately mean that
Speaker 1: you mutate or you you know, suffer terrible injuries unless
Speaker 1: it's an incredibly intense amount of radiation uh at very
Speaker 1: high energies. But it does mean that you need to,
Speaker 1: you know, get out of there and to find some
Speaker 1: other place to be. One thing I didn't really talk
Speaker 1: about in this episode was the concept of half life's
Speaker 1: and that is important because half life's also give us
Speaker 1: an idea of how long radioactive material could potentially remain dangerous.
Speaker 1: And when you're looking at half lives that are on
Speaker 1: thousands of years, you're talking about uh, time that extends
Speaker 1: beyond that which humans have been on Earth right as
Speaker 1: at least as human beings as we understand them, but
Speaker 1: we might trace it back to an earlier evolutionary form
Speaker 1: of humans. But you start looking at some of these
Speaker 1: materials and you realize, wow, this stuff is going to
Speaker 1: be radioactive for longer than humans have been walking around
Speaker 1: on Earth as human beings. Uh. That's why you get
Speaker 1: people who are concerned about things like nuclear power, where
Speaker 1: one of the byproducts of nuclear power tends to be
Speaker 1: nuclear waste that is radioactive. Some of that nuclear waste
Speaker 1: will be radioactive and dangerously so for a relatively short time.
Speaker 1: But there are other types of nuclear waste that will
Speaker 1: be radioactive for a very long time and sure in
Speaker 1: uh it's not emitting radiation at a level high enough
Speaker 1: for it to you know, be dangerous if we don't
Speaker 1: treat it carefully, but it's persistent and and long time
Speaker 1: exposure to it will increase our risk of developing really
Speaker 1: nasty diseases like cancer, So that's where that concern comes in. Now.
Speaker 1: There are a lot of different approaches to nuclear power
Speaker 1: to mitigate the creation of nuclear waste, and there are
Speaker 1: a lot of plans on what to do with that
Speaker 1: nuclear waste to try and keep it far enough away
Speaker 1: from people to not be a problem, but that all
Speaker 1: runs into a lot of other social issues that are
Speaker 1: harder to solve than technical issues. Um. On the flip side,
Speaker 1: we're also looking at possibilities like fusion power, which is
Speaker 1: very different from the fission process that generates a lot
Speaker 1: of nuclear waste, but those are topics for a different episode.
Speaker 1: I hope you have a greater understanding of how radiation
Speaker 1: works and what it actually means, as well as how
Speaker 1: Geiger counters work. Again, I think it's a very elegant
Speaker 1: way to try and detect radiation it's not so much
Speaker 1: detecting the radiation directly, but rather the effects of radiation
Speaker 1: on something that we can more easily observe directly. And
Speaker 1: I think that's a very clever approach to uh to
Speaker 1: creating a meter. If you guys have suggestions for future
Speaker 1: episodes of tech Stuff, reach out to me and let
Speaker 1: me know. On social media, the handle at both Twitter
Speaker 1: and Facebook is exactly the same. That handle is text
Speaker 1: stuff H s W and I'll talk to you again
Speaker 1: really soon. Text Stuff is a production of I Heart
Speaker 1: Radio's How Stuff Works. For more podcasts from I heart Radio,
Speaker 1: visit the I heart Radio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.