Courtesy of SLAC National Accelerator Laboratory
A member of clinical staff views an x-ray of a patient's hand on a computer screen in the Accident and Emergency department of the 'Royal Albert Edward Infirmary' in Wigan, north west England on April 2, 2015. OLI SCARFF/AFP/Getty Images
• Find out more about Chandra X-Ray Observatory at Harvard
• Check out the SLAC National Accelerator Laboratory
Hear “The Electromagnetic Spectrum Song” by The Dino Birds:
Scientists have made high-resolution X-ray laser images of an intact cellular structure much faster and more efficiently than ever possible before. The results are an important step toward atomic-scale imaging of intact biological particles, including viruses and bacteria. Here a 20-sided structure from a bacterial cell, called a carboxysome, is struck by an X-ray pulse (purple) at SLAC’s Linac Coherent Light Source. Courtesy of SLAC National Accelerator Laboratory
The Coherent X-ray Imaging experimental station at SLAC's Linac Coherent Light Source is specialized for X-ray crystallography experiments. (Courtesy of SLAC National Accelerator Laboratory)Brad Plummer
Jets in the early Universe give astronomers a way to probe the growth of black holes at a very early epoch in the cosmos. Using Chandra, astronomers recently discovered a jet in X-rays being illuminated by the cosmic microwave background. The light from this jet was emitted when the Universe was only one fifth of its present age. The main panel of this graphic shows Chandra's X-ray data combined with an optical image, while the inset focuses on the details of the X-ray emission.Chandra X-ray Observatory Center/X-ray: NASA/CXC/ISAS/A.Simionesc
Using Chandra observations, astronomers have discovered the nearest supermassive black hole to Earth that is currently undergoing powerful outbursts. This main panel shows the galaxy M51 in visible light from Hubble (red, green, and blue). The box at the top outlines the Chandra image in this study, which focuses on the smaller component of M51, NGC 5195. In the inset, a pair of arcs can be seen in the Chandra data (blue) and is evidence for outbursts from the supermassive black hole at the center of NGC 5195. Such outbursts are important in the evolution of the black hole and the galaxy it inhabits.Chandra X-ray Observatory Center/X-ray: NASA/CXC/Univ of Texas/E.
Audio Transcript
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FRANKIE BROWNEAGLE: You're listening to Brains On!, where we're serious about being curious. That's right.
[THEME MUSIC]
MOLLY BLOOM: Even if you've never had a broken bone, you're probably familiar with what an X-ray looks like. How would you describe it, Frankie?
FRANKIE BROWNEAGLE: An image of your skeleton or the bones that some people say are hidden inside your skin.
MOLLY BLOOM: And that is the X-ray that most of us are familiar with. But that's not an actual X-ray. It's an image made by capturing X-rays.
FRANKIE BROWNEAGLE: So how are these X-rays made, and how do they let us see through our bodies?
MOLLY BLOOM: And what do X-rays have to do with DNA?
FRANKIE BROWNEAGLE: Or black holes?
MOLLY BLOOM: We'll find out right now. Keep listening. You're listening to Brains On! from NPR News and Southern California Public Radio. I'm Molly Bloom, and here with me today is Frankie Browneagle from Minneapolis. Hello, Frankie.
FRANKIE BROWNEAGLE: Hello.
MOLLY BLOOM: Have you ever had an X-ray image taken?
FRANKIE BROWNEAGLE: Yes, of my bones and how they look.
MOLLY BLOOM: I've had X-rays taken at the dentist, and I am always amazed at how that quick pulse produces such a cool image. Like, it's just my teeth and my bones and my earrings. And I'm not the only one amazed by this. Several of our listeners have written in with questions.
FRANKIE BROWNEAGLE: Like Otto.
OTTO: Hi, I'm Otto from Nottingham, England. My question is, how do X-rays see our bones?
MOLLY BLOOM: To understand how this works, we first have to understand what an X-ray is exactly, not that picture that we mentioned before, but the actual ray that makes the picture possible.
FRANKIE BROWNEAGLE: X-rays are like light.
MOLLY BLOOM: And simply put, light is energy.
FRANKIE BROWNEAGLE: The light we can see.
MOLLY BLOOM: And light that we can't see, like X-rays.
FRANKIE BROWNEAGLE: They're both part of what is known as the electromagnetic spectrum.
MOLLY BLOOM: This also means that X-rays, as well as visible light, are also known as electromagnetic radiation. All these words--
FRANKIE BROWNEAGLE: "Radiation," "light," and "energy."
MOLLY BLOOM: --are describing the same thing. The electromagnetic spectrum is a range of energy that goes from radio waves on one end--
FRANKIE BROWNEAGLE: That's the least energy.
MOLLY BLOOM: --to the high energy gamma rays at the other end.
FRANKIE BROWNEAGLE: So it goes from radio to microwave to infrared to visible light--
MOLLY BLOOM: Visible light is the only part that we can see with our eyes.
FRANKIE BROWNEAGLE: --to ultraviolet to X-rays and then gamma rays.
MOLLY BLOOM: Right.
FRANKIE BROWNEAGLE: It would be useful to have a way to remember that, like a mnemonic device or--
MOLLY BLOOM: Or a song, like from our pals, The Dino Birds.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"]
(SINGING) Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Yeah, here we go. Space between waves gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. It's the electromagnetic spectrum, the electromagnetic spectrum. These are the facts. We checked them. The electromagnetic spectrum.
Thanks, Dino Birds.
FRANKIE BROWNEAGLE: So these different kinds of light or radiation have different energy levels.
MOLLY BLOOM: And that helps explain why X-rays can help us see inside of things that we can't see with our naked eye.
FRANKIE BROWNEAGLE: To really understand, we're going to have to zoom in, way, way in, to an atom.
MOLLY BLOOM: Atoms make up everything. They're what our bodies are made of.
FRANKIE BROWNEAGLE: The air.
MOLLY BLOOM: This desk.
FRANKIE BROWNEAGLE: The trees outside.
MOLLY BLOOM: The water in this glass.
FRANKIE BROWNEAGLE: You get it. Everything is made of atoms.
MOLLY BLOOM: Atoms are very, very tiny, a million times smaller than the width of a human hair-- teensy tiny.
FRANKIE BROWNEAGLE: And atoms are made up of even smaller subatomic particles, like protons, neutrons, and electrons.
MOLLY BLOOM: And it's the electrons that are the star of this show.
ELECTRON: Why, naturally.
FRANKIE BROWNEAGLE: Hello. Who's there?
ELECTRON: Oh, it's just me, an electron. I can give you an insider's look at how X-rays are made.
MOLLY BLOOM: Oh. Let's hear it.
ELECTRON: OK, this is a bumpy ride. I hope you got your seat belt on. Let's start with the X-ray machine at your doctor's office. Inside that metal box is a filament, like the stuff that's in a light bulb. The filament heats up and gives up electrons, like me. Then us electrons are accelerated by a high-voltage electricity.
When we're moving pretty fast, we smash into a piece of metal, like copper or tungsten. Pow! When that happens, we knock electrons off of the piece of metal's atoms. When this happens, energy is released in the form of an X-ray.
MOLLY BLOOM: Wow. Thanks, electron.
ELECTRON: Anytime.
MOLLY BLOOM: OK, once the electrons have done their part to release the X-ray energy from the copper or tungsten metal, the X-ray machine focuses that energy into a beam that sends it out into the world.
FRANKIE BROWNEAGLE: This high energy shoots right through soft tissue, like your skin and organs.
MOLLY BLOOM: But it's absorbed by the heavier atoms, like the calcium that makes your bones or my earrings, which are made out of metal. Once it passes through you, it strikes a film that makes a picture.
FRANKIE BROWNEAGLE: That X-ray picture that you see is actually showing you the parts of the body where the X-rays couldn't pass because they were absorbed. That's why it shows your bones.
MOLLY BLOOM: So the image is sort of an absence of X-rays, kind of like how a shadow is an absence of visible light.
FRANKIE BROWNEAGLE: Think of that picture of your bones like a shadow but with X-rays instead of visible light.
MOLLY BLOOM: But when you get an X-ray at the dentist, you wear a lead apron to protect the rest of your body from the X-rays.
FRANKIE BROWNEAGLE: This got Elijah wondering.
ELIJAH: Hi, my name is Elijah. I'm from Evanston, Illinois. My question is, why is radiation in X-rays bad for you?
MOLLY BLOOM: Remember, X-rays are part of the electromagnetic spectrum.
FRANKIE BROWNEAGLE: Let's hear it again, but this time, faster.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"] radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Yeah, here we go. Space between wave gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
THE DINO BIRDS MEMBER 1: We did it.
THE DINO BIRDS MEMBER 2: Wow.
THE DINO BIRDS MEMBER 1: We did it.
THE DINO BIRDS MEMBER 2: That's not bad. Proud of us.
THE DINO BIRDS MEMBER 1: [GIGGLES]
MOLLY BLOOM: All right, now that we have the seven parts of the spectrum in mind, let's narrow the focus a bit. Radio, microwave, infrared, visible, and ultraviolet.
FRANKIE BROWNEAGLE: Those are all considered non-ionizing.
MOLLY BLOOM: That means it doesn't have enough energy to pop off electrons from atoms like X-rays and gamma rays do.
FRANKIE BROWNEAGLE: So the thing that makes X-rays possible is also the thing that makes them potentially dangerous.
MOLLY BLOOM: Physicist Mohammad Hamidian explains.
MOHAMMAD HAMIDIAN: A huge dose of X-rays, these can lead to things like burns, and they can lead to even cancer because when you pop electrons off, for example, you're changing the DNA in your body, and so those can cause mutations. But if you do it in very small doses, the chances of that are very little.
MOLLY BLOOM: And this ionizing radiation is actually used as a treatment for cancer. Using higher doses than they would to take an X-ray image, doctors use very targeted radiation to damage the cancer cells enough so they die.
FRANKIE BROWNEAGLE: X-rays are commonly used in medical settings, but they're also used to help us see incredible tiny things and very massive ones.
MOLLY BLOOM: We'll get to that in just a bit, but first, I have another use for your laser-sharp focus. It's time for the Mystery Sound.
[DISCORDANT FUTURISTIC SOUNDSCAPE]
WHISPERING VOICE: Mystery Sound.
MOLLY BLOOM: Here it is.
[MYSTERY SOUND PLAYING]
Any guesses?
FRANKIE BROWNEAGLE: Maybe the sound of a dishwasher being shooken around.
MOLLY BLOOM: That's an excellent guess. We'll be back with the answer later in the show.
[MUSIC PLAYING]
Producers Marc Sanchez and Sanden Totten are going to debate again. But we need your help picking the match-up they're going to tackle.
FRANKIE BROWNEAGLE: There are only a few days left to vote. Head to BrainsOn.org and vote for your favorite.
MOLLY BLOOM: There are 10 to choose from, and at the moment that we're taping this episode, the top two are fire versus lasers.
FRANKIE BROWNEAGLE: And left brain versus right brain.
MOLLY BLOOM: But that could change. It is close. So head to BrainsOn.org and vote.
FRANKIE BROWNEAGLE: And while you're there, you can sign up for our newsletter or listen to our past episodes.
MOLLY BLOOM: You can also email us anytime with your questions, mystery sounds, drawings, and high-fives. The email address is BrainsOn@M-- as in Minnesota-- PR.org.
FRANKIE BROWNEAGLE: Now it's time for the Brains' Honor Roll. These are the kids who fill the show with their energy and ideas.
[MUSIC PLAYING]
MOLLY BLOOM: [LISTING HONOR ROLL]
(SINGING) Brains' Honor Roll.
FRANKIE BROWNEAGLE: You're listening to [NUU'ETAA] That's "Brains On" in Nuu'etaa. I'm Frankie Browneagle.
MOLLY BLOOM: And I'm Molly Bloom. You and your uncle translated "Brains On" into Nuu'etaa, and where did you say that was spoken?
FRANKIE BROWNEAGLE: It was from Mandan in North Dakota, in the Fort Berthold Indian Reservation.
MOLLY BLOOM: Do you speak that language?
FRANKIE BROWNEAGLE: I'm learning it, actually. I'm trying to become what my uncle says the people who make the language survive.
MOLLY BLOOM: Well, that is very, very cool. And I know we have listeners all over the world, so if you would like to record yourself saying "Brains On" in a language besides English, we would love to hear it. Send your recordings to BrainsOn@M-- as in Minnesota-- PR.org.
FRANKIE BROWNEAGLE: Now let's get back to X-rays.
MOLLY BLOOM: We know how X-rays help us see our bones, but they're used for a lot more than just that. OK, Dino Birds, one more time with the electromagnetic spectrum, please.
FRANKIE BROWNEAGLE: Yeah, and this time, extra fast.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"] Radio, microwave, infrared, visible, ultraviolet, X-rays, gamma. Yeah, here we go. Space between waves gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
[THE DINO BIRDS SIGH]
Impressive.
MOLLY BLOOM: Impressive indeed. And just like there's a spectrum of radiation, there's also a spectrum of different energies within each of those categories. There are higher energy X-rays and lower energy X-rays.
FRANKIE BROWNEAGLE: There are some very cool machines making more powerful X-rays than the ones in your doctor's office.
MOLLY BLOOM: Like the ones at the SLAC National Accelerator Laboratory, where Alan Fry is the director of Laser Science and Technology.
ALAN FRY: Rather than just slamming electrons into a piece of metal, you can set up magnets that cause the electrons to wiggle. And when electrons wiggle, they give off energy. And again, some of that energy is in the form of electromagnetic radiation. Scientists do this in a very directed way to produce very precisely defined beams of X-rays.
FRANKIE BROWNEAGLE: One machine they use is called a synchrotron.
ALAN FRY: The electrons go around in a circular ring, and there are magnets that cause the electrons to bend. Each time they bend, they give off X-rays, and depending on how much energy the electrons have, we can change the energy of the X-rays.
FRANKIE BROWNEAGLE: Using X-rays like this allows you to get a look at something that would otherwise be impossible to see.
ALAN FRY: A good example of this is the proteins that are involved in photosynthesis. Photosynthesis is the process where plants absorb energy from the sun, and they use it to break apart water molecules, which releases oxygen, and it also releases energy. And that's how plants harvest energy from the sun.
FRANKIE BROWNEAGLE: But this process happens incredibly fast.
ALAN FRY: The photosynthesis process is actually relatively slow. It takes place in a time frame that's about 1 millionth of a second. Chemical reactions-- for example, breaking the bond of a molecule-- those processes take place in a time frame that's called a femtosecond.
MOLLY BLOOM: Put another way, 1 femtosecond is to 1 minute, as 1 minute is to the age of the entire universe.
FRANKIE BROWNEAGLE: Whoa.
ALAN FRY: Our X-rays can produce little pulses of photons that only last for a few femtoseconds. It's a little bit like we've got a flash photograph cameras.
CHILDREN: Brains On!
MOLLY BLOOM: Even though the technology has improved drastically, the idea of using X-rays to understand the molecular structure of our bodies and the world around us is over 100 years old. Georgina Ferry is a science journalist. She wrote a biography of Dorothy Hodgkin, one of the pioneers of this field.
GEORGINA FERRY: If you think about engineering and you think of your body as a machine, when you make an automobile or an airplane, you have to know how all the parts fit together in order to understand how they work. And our bodies are full of molecules, all with special jobs to do, and they do those special jobs by fitting together in very particular ways.
And what X-ray crystallography allows you to do is to find out what the shapes of all those molecules are so that you can start to understand how they fit together. And in the case of the molecules in our bodies, for instance, you can start to maybe design new drugs because they'll fit into a particular space on one of these molecules that we have inside us.
FRANKIE BROWNEAGLE: The technique of X-ray crystallography was discovered in 1912.
MOLLY BLOOM: The basic idea is that you take something very small--
FRANKIE BROWNEAGLE: Like a part of a cell.
MOLLY BLOOM: --and make a crystal out of it.
FRANKIE BROWNEAGLE: Then you shine an X-ray on the crystal.
GEORGINA FERRY: If you fire a beam of X-rays into a crystal that you've made in that way, it scatters the X-ray. And if you then catch those scattered X-rays on a film, you get a pattern of spots. And the pattern of spots can tell you where all the atoms are in the molecule, and so you can calculate what the inside of that molecule looks like.
MOLLY BLOOM: Before computers, this process took a long time.
GEORGINA FERRY: What you had to do was calculate how intense those spots were. And the only way to do that in the early days was to have a kind of reference, set of spots of different brightnesses, and you'd hold your set of reference spots up against the picture and say, is that a darker one or a lighter one? And you'd make a note of that.
FRANKIE BROWNEAGLE: Early computers of 1950s made it easier to calculate, but the process was still long.
MOLLY BLOOM: It took Dorothy Hodgkin three years to figure out the structure of penicillin, seven years for vitamin B12, and 35 years for insulin, which she finally cracked in 1969.
FRANKIE BROWNEAGLE: Today, powerful computers make the process much faster.
GEORGINA FERRY: But what tends to take a long time now is things like getting the crystal in the first place. We have a lot of very interesting but complicated protein molecules that sit on the surfaces of our cells and act like little gateways, and because they like to live in a membrane, it's very difficult to get them out. There are still many molecules that we don't know the structures of, and lots of people all around the world are still working very hard to discover the structures of those molecules.
FRANKIE BROWNEAGLE: One of the people using X-rays to study molecules is Hao Wu.
MOLLY BLOOM: In her Harvard lab, she uses X-ray crystallography to study the immune system.
HAO WU: So when I first saw these crystals, I was like, oh my god, how can I touch this? I feel like it's so fragile that I'm going to break it because they're just so beautiful I didn't want to destroy them.
FRANKIE BROWNEAGLE: The crystals she works with are incredibly tiny. You can't see them with the naked eye.
HAO WU: It does take some dexterity, actually, to handle your crystals. But it's really amazing once you're able to look at the diffraction pattern out of those crystals and thinking that those pattern tells you exactly the molecular arrangement of your protein.
MOLLY BLOOM: So X-ray crystallography is used to help us understand the mysteries at the smallest atomic level.
FRANKIE BROWNEAGLE: But X-rays are also used to help us understand mysteries on a very different scale, the mysteries of the universe. I talked with Dr. Belinda Wilkes.
MOLLY BLOOM: She is the director of NASA's Chandra X-ray Observatory.
FRANKIE BROWNEAGLE: What is X-ray astronomy?
BELINDA WILKES: X-ray astronomy is the study of X-ray emission from celestial sources. It's nothing to do with medical X-rays, although one of the principles is very important, and that is medical X-rays are used because the X-rays penetrate your body, and X-rays coming from sources out in the universe are actually very useful for seeing all the way into the center of those sources.
In terms of the X-rays from the celestial sources, like stars and black holes, we can see right into the core of those sources with the X-rays because the X-rays come all the way out. And the other material around, sort of similar to the skin in your arm but is dust and gas, and that does not stop the X-rays. They still come out.
So we can see X-rays from things that are buried in huge amounts of material. We cannot see the visible light from those sources, but we can see the X-rays. So it's very helpful for us to look in the X-rays and find things that we couldn't see otherwise. That's one thing.
Another thing is that the sources that give us X-rays are actually the hottest and most violent places in the universe. That's how the X-rays are produced. So for example, when a star dies and goes supernova, the first thing we see is X-ray emission.
FRANKIE BROWNEAGLE: If black holes don't emit light, how can you see the X-rays then?
HAO WU: Yes, actually, that's a very good question. We don't see the Black holes themselves. What we see is a lot of material around the black holes that is trying to fall in because a black hole is very big and massive. It's small in size, but it's big in terms of the amount of mass, so it has a very strong gravitational force. The gravitational force is what keeps us on the Earth. If we jump up, we come back down.
Well, for a black hole, that force is much, much stronger, so it pulls in everything around it. So all the gas and the material and some of the stars and the galaxy in which it sits get pulled down into the black hole. And because they're all trying to go in there at the same time, the material gets very hot, and that gives us X-rays. So we can see quite close to the black hole, but at some point, we cannot see beyond what's called the event horizon of the black hole, which is the definition of how big it is.
FRANKIE BROWNEAGLE: How far can X-rays reach?
HAO WU: We can see X-rays coming from the most distant things in the universe, so right to the edge of the universe. Some of them actually get to us. They are emitted by material around a very big black hole, what we call a supermassive black hole. Right close to the beginning of the universe, when we look at things that are further away, we're actually looking back in time as well. And that light can reach us so that we can learn about the first black holes that were ever born in the universe through looking at them in X-ray light.
OPERA SINGER: (SINGING) Brains On! [CLEARS THROAT]
MOLLY BLOOM: OK, let's hear that mystery sound one more time.
[MYSTERY SOUND PLAYING]
Any new guesses?
FRANKIE BROWNEAGLE: Maybe it's in space being thrown around.
MOLLY BLOOM: That's good because it is related to X-rays in some way. Any other thoughts?
FRANKIE BROWNEAGLE: Maybe it could be the galaxy X-rays that make special sounds when they pass by.
MOLLY BLOOM: That is an excellent guess. Here's the answer.
CARLOS CAMARA: That was the sound of peeling Scotch tape.
FRANKIE BROWNEAGLE: What?
MOLLY BLOOM: I know, right? So you were wrong, but does it sound familiar to you now that you know what it was?
FRANKIE BROWNEAGLE: Yes.
MOLLY BLOOM: So here to tell us how Scotch tape relates to X-rays is Producer Marc Sanchez.
FRANKIE BROWNEAGLE: Hi, Marc.
MARC SANCHEZ: Hi there.
MOLLY BLOOM: So what does Scotch tape have to do with X-rays?
MARC SANCHEZ: Well, it starts with this guy.
CARLOS CAMARA: Hello, my name is Carlos Camara. I am the chief scientist at Tribogenics, a company that I cofounded about six years ago to develop X-rays from triboluminescence.
MOLLY BLOOM: What is triboluminescence?
FRANKIE BROWNEAGLE: Yeah.
MARC SANCHEZ: Well, triboluminescence is the emission of light from friction or rubbing two materials together. Back in 2008, Carlos was studying triboluminescence with a bunch of materials that are known to give off visible light. That's the light we can see. So for his experiment, in order to see the light, it had to be extremely dark.
Picture this, Carlos is down in the basement of his lab at UCLA. It's pitch black. He basically has to feel his way around with his hands. One of the other materials that he was working with was called mica, which is a flat, flaky mineral. The layers of mica are often stacked on top of each other, like the pages of a book.
CARLOS CAMARA: There have been reports from Russian scientists claiming that crushing mica in a vacuum would not only make visible light but would also make X-rays. We became very interested on this because the difference between visible light and X-rays is a factor of about 10,000.
MARC SANCHEZ: That's a 10,000-volt difference in energy when you crush mica in a vacuum. And before you ask, he's talking about a vacuum chamber.
MOLLY BLOOM: Not the kind of vacuum you use to clean a carpet.
MARC SANCHEZ: Right.
FRANKIE BROWNEAGLE: That's what I was thinking.
MARC SANCHEZ: See? Well, a vacuum chamber is a space that is completely void of matter. So this mica exists all by itself.
CARLOS CAMARA: So I had a roll of Scotch tape amongst all the other materials and tools that I had in front of me, and I'm feeling around with my hands because it's completely dark. And as I peel the roll of Scotch tape, I see that it makes more light than anything else that I'm trying.
MARC SANCHEZ: So Carlos and his team of researchers did what any curious scientist does.
CARLOS CAMARA: We naturally decided to take the roll of Scotch tape, put it in a vacuum chamber. And sure enough, it made more X-rays than anything else we had tried.
MARC SANCHEZ: Remember how exciting atoms can make them release electrons and X-rays? The same thing is happening here with Scotch tape. Carlos and the other researchers were actually able to use a few pieces of tape to take a crude X-ray picture of a finger. Once they did this, pieces of a puzzle started to fall into place.
CARLOS CAMARA: In particular, we discovered that not simply unsticking a roll of tape would make X-rays, but if you had the right materials, you can have simply two rollers rotating against each other, making X-rays. So at that point, it became clear to us that there was a possibility of actual useful applications of this very simple effect.
[SCOTCH TAPE BEING PEELED]
Our first product is an X-ray fluorescence analyzer. It's an instrument that can basically tell you what material you're looking at, and it tells you the composition.
MARC SANCHEZ: The device is this little boxy thing with a handle. It looks similar to a radar gun if you've ever seen one of those. And when you squeeze the trigger, it emits a burst of X-ray light.
CARLOS CAMARA: Every element has a unique X-ray energy fingerprint. And the way it works is that if you shoot X-rays at a material, you can excite the electrons of the material in the X-ray energy, and so the X-rays that glow back at you from the material uniquely identify what atoms are present.
MARC SANCHEZ: But what Carlos is really excited about is the possibilities for portable X-rays. His team is developing a portable X-ray device that is about the size of a soda can.
CARLOS CAMARA: In comparison, the most portable sources that would get the similar job done currently available are much, much larger and heavier, about the size of a small oven.
[SOUND EFFECT]
So imagine in disaster relief.
MARC SANCHEZ: So there's an earthquake or tsunami somewhere. Lots of people in need of medical attention.
CARLOS CAMARA: Imagine if you had a briefcase that could be just as good as an X-ray medical suite that you have in the hospital.
MARC SANCHEZ: It's not totally 100% as good as a hospital, but Carlos thinks that you could be on the ground with these suitcase X-ray machines, basically carrying the room of a hospital in one hand.
[MUSIC PLAYING]
And if you guys want to see triboluminescence in action, Carlos gave me a couple of really cool experiments you can try at your very own home. One is the Scotch tape method he used, and the other involves candy, specifically wintergreen candy, like LIFE SAVERS.
First off, you need to find a really dark space, maybe a closet, someplace where there's as little light as possible. Take either the tape or the wintergreen LIFE SAVERS into the space and let your eyes get used to the dark. This might take about four or five minutes, but be patient because it's worth it.
If you unspool the tape, you should see a faint blue glow coming from where the sticky part leaves the rest of the roll. And the LIFE SAVERS, they are going to glow green. You can either chew them with your mouth-- open, I guess-- or you can put them in a plastic sandwich bag and crush them with pliers. And there you have it, triboluminescence.
FRANKIE BROWNEAGLE: That's amazing.
MOLLY BLOOM: Thanks, Marc.
MARC SANCHEZ: You're welcome.
[THEME MUSIC]
FRANKIE BROWNEAGLE: X-rays are radiation.
MOLLY BLOOM: Or light.
FRANKIE BROWNEAGLE: Or energy.
MOLLY BLOOM: A part of the electromagnetic spectrum.
FRANKIE BROWNEAGLE: These high-energy rays can penetrate tissue and allow us to see our bones.
MOLLY BLOOM: And they can also help us understand the structures of the smallest proteins and molecules through X-ray crystallography.
FRANKIE BROWNEAGLE: And by picking up X-rays from space, we can learn a lot about the universe.
MOLLY BLOOM: That's it for this episode of Brains On!
FRANKIE BROWNEAGLE: Brains On! is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Many thanks to [INAUDIBLE], Vincent [? Monas, ?] Megan Treinen, Carol [? Zoll, ?] Vahan [? Baladuni, ?] and Andrew Gordon.
FRANKIE BROWNEAGLE: If you're a fan of Brains On!, consider leaving a review in iTunes.
MOLLY BLOOM: It really helps other kids and parents find out about the show.
FRANKIE BROWNEAGLE: And you can keep up with us on Instagram and Twitter.
MOLLY BLOOM: We're @Brains_On.
FRANKIE BROWNEAGLE: And we're on Facebook, too.
MOLLY BLOOM: And remember to head to BrainsOn.org to vote for the debate you want Marc and Sanden to tackle.
FRANKIE BROWNEAGLE: Thanks for listening.
[THEME MUSIC PLAYING]
[THEME MUSIC]
MOLLY BLOOM: Even if you've never had a broken bone, you're probably familiar with what an X-ray looks like. How would you describe it, Frankie?
FRANKIE BROWNEAGLE: An image of your skeleton or the bones that some people say are hidden inside your skin.
MOLLY BLOOM: And that is the X-ray that most of us are familiar with. But that's not an actual X-ray. It's an image made by capturing X-rays.
FRANKIE BROWNEAGLE: So how are these X-rays made, and how do they let us see through our bodies?
MOLLY BLOOM: And what do X-rays have to do with DNA?
FRANKIE BROWNEAGLE: Or black holes?
MOLLY BLOOM: We'll find out right now. Keep listening. You're listening to Brains On! from NPR News and Southern California Public Radio. I'm Molly Bloom, and here with me today is Frankie Browneagle from Minneapolis. Hello, Frankie.
FRANKIE BROWNEAGLE: Hello.
MOLLY BLOOM: Have you ever had an X-ray image taken?
FRANKIE BROWNEAGLE: Yes, of my bones and how they look.
MOLLY BLOOM: I've had X-rays taken at the dentist, and I am always amazed at how that quick pulse produces such a cool image. Like, it's just my teeth and my bones and my earrings. And I'm not the only one amazed by this. Several of our listeners have written in with questions.
FRANKIE BROWNEAGLE: Like Otto.
OTTO: Hi, I'm Otto from Nottingham, England. My question is, how do X-rays see our bones?
MOLLY BLOOM: To understand how this works, we first have to understand what an X-ray is exactly, not that picture that we mentioned before, but the actual ray that makes the picture possible.
FRANKIE BROWNEAGLE: X-rays are like light.
MOLLY BLOOM: And simply put, light is energy.
FRANKIE BROWNEAGLE: The light we can see.
MOLLY BLOOM: And light that we can't see, like X-rays.
FRANKIE BROWNEAGLE: They're both part of what is known as the electromagnetic spectrum.
MOLLY BLOOM: This also means that X-rays, as well as visible light, are also known as electromagnetic radiation. All these words--
FRANKIE BROWNEAGLE: "Radiation," "light," and "energy."
MOLLY BLOOM: --are describing the same thing. The electromagnetic spectrum is a range of energy that goes from radio waves on one end--
FRANKIE BROWNEAGLE: That's the least energy.
MOLLY BLOOM: --to the high energy gamma rays at the other end.
FRANKIE BROWNEAGLE: So it goes from radio to microwave to infrared to visible light--
MOLLY BLOOM: Visible light is the only part that we can see with our eyes.
FRANKIE BROWNEAGLE: --to ultraviolet to X-rays and then gamma rays.
MOLLY BLOOM: Right.
FRANKIE BROWNEAGLE: It would be useful to have a way to remember that, like a mnemonic device or--
MOLLY BLOOM: Or a song, like from our pals, The Dino Birds.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"]
(SINGING) Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Yeah, here we go. Space between waves gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. It's the electromagnetic spectrum, the electromagnetic spectrum. These are the facts. We checked them. The electromagnetic spectrum.
Thanks, Dino Birds.
FRANKIE BROWNEAGLE: So these different kinds of light or radiation have different energy levels.
MOLLY BLOOM: And that helps explain why X-rays can help us see inside of things that we can't see with our naked eye.
FRANKIE BROWNEAGLE: To really understand, we're going to have to zoom in, way, way in, to an atom.
MOLLY BLOOM: Atoms make up everything. They're what our bodies are made of.
FRANKIE BROWNEAGLE: The air.
MOLLY BLOOM: This desk.
FRANKIE BROWNEAGLE: The trees outside.
MOLLY BLOOM: The water in this glass.
FRANKIE BROWNEAGLE: You get it. Everything is made of atoms.
MOLLY BLOOM: Atoms are very, very tiny, a million times smaller than the width of a human hair-- teensy tiny.
FRANKIE BROWNEAGLE: And atoms are made up of even smaller subatomic particles, like protons, neutrons, and electrons.
MOLLY BLOOM: And it's the electrons that are the star of this show.
ELECTRON: Why, naturally.
FRANKIE BROWNEAGLE: Hello. Who's there?
ELECTRON: Oh, it's just me, an electron. I can give you an insider's look at how X-rays are made.
MOLLY BLOOM: Oh. Let's hear it.
ELECTRON: OK, this is a bumpy ride. I hope you got your seat belt on. Let's start with the X-ray machine at your doctor's office. Inside that metal box is a filament, like the stuff that's in a light bulb. The filament heats up and gives up electrons, like me. Then us electrons are accelerated by a high-voltage electricity.
When we're moving pretty fast, we smash into a piece of metal, like copper or tungsten. Pow! When that happens, we knock electrons off of the piece of metal's atoms. When this happens, energy is released in the form of an X-ray.
MOLLY BLOOM: Wow. Thanks, electron.
ELECTRON: Anytime.
MOLLY BLOOM: OK, once the electrons have done their part to release the X-ray energy from the copper or tungsten metal, the X-ray machine focuses that energy into a beam that sends it out into the world.
FRANKIE BROWNEAGLE: This high energy shoots right through soft tissue, like your skin and organs.
MOLLY BLOOM: But it's absorbed by the heavier atoms, like the calcium that makes your bones or my earrings, which are made out of metal. Once it passes through you, it strikes a film that makes a picture.
FRANKIE BROWNEAGLE: That X-ray picture that you see is actually showing you the parts of the body where the X-rays couldn't pass because they were absorbed. That's why it shows your bones.
MOLLY BLOOM: So the image is sort of an absence of X-rays, kind of like how a shadow is an absence of visible light.
FRANKIE BROWNEAGLE: Think of that picture of your bones like a shadow but with X-rays instead of visible light.
MOLLY BLOOM: But when you get an X-ray at the dentist, you wear a lead apron to protect the rest of your body from the X-rays.
FRANKIE BROWNEAGLE: This got Elijah wondering.
ELIJAH: Hi, my name is Elijah. I'm from Evanston, Illinois. My question is, why is radiation in X-rays bad for you?
MOLLY BLOOM: Remember, X-rays are part of the electromagnetic spectrum.
FRANKIE BROWNEAGLE: Let's hear it again, but this time, faster.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"] radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Yeah, here we go. Space between wave gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
THE DINO BIRDS MEMBER 1: We did it.
THE DINO BIRDS MEMBER 2: Wow.
THE DINO BIRDS MEMBER 1: We did it.
THE DINO BIRDS MEMBER 2: That's not bad. Proud of us.
THE DINO BIRDS MEMBER 1: [GIGGLES]
MOLLY BLOOM: All right, now that we have the seven parts of the spectrum in mind, let's narrow the focus a bit. Radio, microwave, infrared, visible, and ultraviolet.
FRANKIE BROWNEAGLE: Those are all considered non-ionizing.
MOLLY BLOOM: That means it doesn't have enough energy to pop off electrons from atoms like X-rays and gamma rays do.
FRANKIE BROWNEAGLE: So the thing that makes X-rays possible is also the thing that makes them potentially dangerous.
MOLLY BLOOM: Physicist Mohammad Hamidian explains.
MOHAMMAD HAMIDIAN: A huge dose of X-rays, these can lead to things like burns, and they can lead to even cancer because when you pop electrons off, for example, you're changing the DNA in your body, and so those can cause mutations. But if you do it in very small doses, the chances of that are very little.
MOLLY BLOOM: And this ionizing radiation is actually used as a treatment for cancer. Using higher doses than they would to take an X-ray image, doctors use very targeted radiation to damage the cancer cells enough so they die.
FRANKIE BROWNEAGLE: X-rays are commonly used in medical settings, but they're also used to help us see incredible tiny things and very massive ones.
MOLLY BLOOM: We'll get to that in just a bit, but first, I have another use for your laser-sharp focus. It's time for the Mystery Sound.
[DISCORDANT FUTURISTIC SOUNDSCAPE]
WHISPERING VOICE: Mystery Sound.
MOLLY BLOOM: Here it is.
[MYSTERY SOUND PLAYING]
Any guesses?
FRANKIE BROWNEAGLE: Maybe the sound of a dishwasher being shooken around.
MOLLY BLOOM: That's an excellent guess. We'll be back with the answer later in the show.
[MUSIC PLAYING]
Producers Marc Sanchez and Sanden Totten are going to debate again. But we need your help picking the match-up they're going to tackle.
FRANKIE BROWNEAGLE: There are only a few days left to vote. Head to BrainsOn.org and vote for your favorite.
MOLLY BLOOM: There are 10 to choose from, and at the moment that we're taping this episode, the top two are fire versus lasers.
FRANKIE BROWNEAGLE: And left brain versus right brain.
MOLLY BLOOM: But that could change. It is close. So head to BrainsOn.org and vote.
FRANKIE BROWNEAGLE: And while you're there, you can sign up for our newsletter or listen to our past episodes.
MOLLY BLOOM: You can also email us anytime with your questions, mystery sounds, drawings, and high-fives. The email address is BrainsOn@M-- as in Minnesota-- PR.org.
FRANKIE BROWNEAGLE: Now it's time for the Brains' Honor Roll. These are the kids who fill the show with their energy and ideas.
[MUSIC PLAYING]
MOLLY BLOOM: [LISTING HONOR ROLL]
(SINGING) Brains' Honor Roll.
FRANKIE BROWNEAGLE: You're listening to [NUU'ETAA] That's "Brains On" in Nuu'etaa. I'm Frankie Browneagle.
MOLLY BLOOM: And I'm Molly Bloom. You and your uncle translated "Brains On" into Nuu'etaa, and where did you say that was spoken?
FRANKIE BROWNEAGLE: It was from Mandan in North Dakota, in the Fort Berthold Indian Reservation.
MOLLY BLOOM: Do you speak that language?
FRANKIE BROWNEAGLE: I'm learning it, actually. I'm trying to become what my uncle says the people who make the language survive.
MOLLY BLOOM: Well, that is very, very cool. And I know we have listeners all over the world, so if you would like to record yourself saying "Brains On" in a language besides English, we would love to hear it. Send your recordings to BrainsOn@M-- as in Minnesota-- PR.org.
FRANKIE BROWNEAGLE: Now let's get back to X-rays.
MOLLY BLOOM: We know how X-rays help us see our bones, but they're used for a lot more than just that. OK, Dino Birds, one more time with the electromagnetic spectrum, please.
FRANKIE BROWNEAGLE: Yeah, and this time, extra fast.
[THE DINO BIRDS, "THE ELECTROMAGNETIC SPECTRUM SONG"] Radio, microwave, infrared, visible, ultraviolet, X-rays, gamma. Yeah, here we go. Space between waves gets shorter and shorter. Electromagnetic spectrum, that's the order. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
[THE DINO BIRDS SIGH]
Impressive.
MOLLY BLOOM: Impressive indeed. And just like there's a spectrum of radiation, there's also a spectrum of different energies within each of those categories. There are higher energy X-rays and lower energy X-rays.
FRANKIE BROWNEAGLE: There are some very cool machines making more powerful X-rays than the ones in your doctor's office.
MOLLY BLOOM: Like the ones at the SLAC National Accelerator Laboratory, where Alan Fry is the director of Laser Science and Technology.
ALAN FRY: Rather than just slamming electrons into a piece of metal, you can set up magnets that cause the electrons to wiggle. And when electrons wiggle, they give off energy. And again, some of that energy is in the form of electromagnetic radiation. Scientists do this in a very directed way to produce very precisely defined beams of X-rays.
FRANKIE BROWNEAGLE: One machine they use is called a synchrotron.
ALAN FRY: The electrons go around in a circular ring, and there are magnets that cause the electrons to bend. Each time they bend, they give off X-rays, and depending on how much energy the electrons have, we can change the energy of the X-rays.
FRANKIE BROWNEAGLE: Using X-rays like this allows you to get a look at something that would otherwise be impossible to see.
ALAN FRY: A good example of this is the proteins that are involved in photosynthesis. Photosynthesis is the process where plants absorb energy from the sun, and they use it to break apart water molecules, which releases oxygen, and it also releases energy. And that's how plants harvest energy from the sun.
FRANKIE BROWNEAGLE: But this process happens incredibly fast.
ALAN FRY: The photosynthesis process is actually relatively slow. It takes place in a time frame that's about 1 millionth of a second. Chemical reactions-- for example, breaking the bond of a molecule-- those processes take place in a time frame that's called a femtosecond.
MOLLY BLOOM: Put another way, 1 femtosecond is to 1 minute, as 1 minute is to the age of the entire universe.
FRANKIE BROWNEAGLE: Whoa.
ALAN FRY: Our X-rays can produce little pulses of photons that only last for a few femtoseconds. It's a little bit like we've got a flash photograph cameras.
CHILDREN: Brains On!
MOLLY BLOOM: Even though the technology has improved drastically, the idea of using X-rays to understand the molecular structure of our bodies and the world around us is over 100 years old. Georgina Ferry is a science journalist. She wrote a biography of Dorothy Hodgkin, one of the pioneers of this field.
GEORGINA FERRY: If you think about engineering and you think of your body as a machine, when you make an automobile or an airplane, you have to know how all the parts fit together in order to understand how they work. And our bodies are full of molecules, all with special jobs to do, and they do those special jobs by fitting together in very particular ways.
And what X-ray crystallography allows you to do is to find out what the shapes of all those molecules are so that you can start to understand how they fit together. And in the case of the molecules in our bodies, for instance, you can start to maybe design new drugs because they'll fit into a particular space on one of these molecules that we have inside us.
FRANKIE BROWNEAGLE: The technique of X-ray crystallography was discovered in 1912.
MOLLY BLOOM: The basic idea is that you take something very small--
FRANKIE BROWNEAGLE: Like a part of a cell.
MOLLY BLOOM: --and make a crystal out of it.
FRANKIE BROWNEAGLE: Then you shine an X-ray on the crystal.
GEORGINA FERRY: If you fire a beam of X-rays into a crystal that you've made in that way, it scatters the X-ray. And if you then catch those scattered X-rays on a film, you get a pattern of spots. And the pattern of spots can tell you where all the atoms are in the molecule, and so you can calculate what the inside of that molecule looks like.
MOLLY BLOOM: Before computers, this process took a long time.
GEORGINA FERRY: What you had to do was calculate how intense those spots were. And the only way to do that in the early days was to have a kind of reference, set of spots of different brightnesses, and you'd hold your set of reference spots up against the picture and say, is that a darker one or a lighter one? And you'd make a note of that.
FRANKIE BROWNEAGLE: Early computers of 1950s made it easier to calculate, but the process was still long.
MOLLY BLOOM: It took Dorothy Hodgkin three years to figure out the structure of penicillin, seven years for vitamin B12, and 35 years for insulin, which she finally cracked in 1969.
FRANKIE BROWNEAGLE: Today, powerful computers make the process much faster.
GEORGINA FERRY: But what tends to take a long time now is things like getting the crystal in the first place. We have a lot of very interesting but complicated protein molecules that sit on the surfaces of our cells and act like little gateways, and because they like to live in a membrane, it's very difficult to get them out. There are still many molecules that we don't know the structures of, and lots of people all around the world are still working very hard to discover the structures of those molecules.
FRANKIE BROWNEAGLE: One of the people using X-rays to study molecules is Hao Wu.
MOLLY BLOOM: In her Harvard lab, she uses X-ray crystallography to study the immune system.
HAO WU: So when I first saw these crystals, I was like, oh my god, how can I touch this? I feel like it's so fragile that I'm going to break it because they're just so beautiful I didn't want to destroy them.
FRANKIE BROWNEAGLE: The crystals she works with are incredibly tiny. You can't see them with the naked eye.
HAO WU: It does take some dexterity, actually, to handle your crystals. But it's really amazing once you're able to look at the diffraction pattern out of those crystals and thinking that those pattern tells you exactly the molecular arrangement of your protein.
MOLLY BLOOM: So X-ray crystallography is used to help us understand the mysteries at the smallest atomic level.
FRANKIE BROWNEAGLE: But X-rays are also used to help us understand mysteries on a very different scale, the mysteries of the universe. I talked with Dr. Belinda Wilkes.
MOLLY BLOOM: She is the director of NASA's Chandra X-ray Observatory.
FRANKIE BROWNEAGLE: What is X-ray astronomy?
BELINDA WILKES: X-ray astronomy is the study of X-ray emission from celestial sources. It's nothing to do with medical X-rays, although one of the principles is very important, and that is medical X-rays are used because the X-rays penetrate your body, and X-rays coming from sources out in the universe are actually very useful for seeing all the way into the center of those sources.
In terms of the X-rays from the celestial sources, like stars and black holes, we can see right into the core of those sources with the X-rays because the X-rays come all the way out. And the other material around, sort of similar to the skin in your arm but is dust and gas, and that does not stop the X-rays. They still come out.
So we can see X-rays from things that are buried in huge amounts of material. We cannot see the visible light from those sources, but we can see the X-rays. So it's very helpful for us to look in the X-rays and find things that we couldn't see otherwise. That's one thing.
Another thing is that the sources that give us X-rays are actually the hottest and most violent places in the universe. That's how the X-rays are produced. So for example, when a star dies and goes supernova, the first thing we see is X-ray emission.
FRANKIE BROWNEAGLE: If black holes don't emit light, how can you see the X-rays then?
HAO WU: Yes, actually, that's a very good question. We don't see the Black holes themselves. What we see is a lot of material around the black holes that is trying to fall in because a black hole is very big and massive. It's small in size, but it's big in terms of the amount of mass, so it has a very strong gravitational force. The gravitational force is what keeps us on the Earth. If we jump up, we come back down.
Well, for a black hole, that force is much, much stronger, so it pulls in everything around it. So all the gas and the material and some of the stars and the galaxy in which it sits get pulled down into the black hole. And because they're all trying to go in there at the same time, the material gets very hot, and that gives us X-rays. So we can see quite close to the black hole, but at some point, we cannot see beyond what's called the event horizon of the black hole, which is the definition of how big it is.
FRANKIE BROWNEAGLE: How far can X-rays reach?
HAO WU: We can see X-rays coming from the most distant things in the universe, so right to the edge of the universe. Some of them actually get to us. They are emitted by material around a very big black hole, what we call a supermassive black hole. Right close to the beginning of the universe, when we look at things that are further away, we're actually looking back in time as well. And that light can reach us so that we can learn about the first black holes that were ever born in the universe through looking at them in X-ray light.
OPERA SINGER: (SINGING) Brains On! [CLEARS THROAT]
MOLLY BLOOM: OK, let's hear that mystery sound one more time.
[MYSTERY SOUND PLAYING]
Any new guesses?
FRANKIE BROWNEAGLE: Maybe it's in space being thrown around.
MOLLY BLOOM: That's good because it is related to X-rays in some way. Any other thoughts?
FRANKIE BROWNEAGLE: Maybe it could be the galaxy X-rays that make special sounds when they pass by.
MOLLY BLOOM: That is an excellent guess. Here's the answer.
CARLOS CAMARA: That was the sound of peeling Scotch tape.
FRANKIE BROWNEAGLE: What?
MOLLY BLOOM: I know, right? So you were wrong, but does it sound familiar to you now that you know what it was?
FRANKIE BROWNEAGLE: Yes.
MOLLY BLOOM: So here to tell us how Scotch tape relates to X-rays is Producer Marc Sanchez.
FRANKIE BROWNEAGLE: Hi, Marc.
MARC SANCHEZ: Hi there.
MOLLY BLOOM: So what does Scotch tape have to do with X-rays?
MARC SANCHEZ: Well, it starts with this guy.
CARLOS CAMARA: Hello, my name is Carlos Camara. I am the chief scientist at Tribogenics, a company that I cofounded about six years ago to develop X-rays from triboluminescence.
MOLLY BLOOM: What is triboluminescence?
FRANKIE BROWNEAGLE: Yeah.
MARC SANCHEZ: Well, triboluminescence is the emission of light from friction or rubbing two materials together. Back in 2008, Carlos was studying triboluminescence with a bunch of materials that are known to give off visible light. That's the light we can see. So for his experiment, in order to see the light, it had to be extremely dark.
Picture this, Carlos is down in the basement of his lab at UCLA. It's pitch black. He basically has to feel his way around with his hands. One of the other materials that he was working with was called mica, which is a flat, flaky mineral. The layers of mica are often stacked on top of each other, like the pages of a book.
CARLOS CAMARA: There have been reports from Russian scientists claiming that crushing mica in a vacuum would not only make visible light but would also make X-rays. We became very interested on this because the difference between visible light and X-rays is a factor of about 10,000.
MARC SANCHEZ: That's a 10,000-volt difference in energy when you crush mica in a vacuum. And before you ask, he's talking about a vacuum chamber.
MOLLY BLOOM: Not the kind of vacuum you use to clean a carpet.
MARC SANCHEZ: Right.
FRANKIE BROWNEAGLE: That's what I was thinking.
MARC SANCHEZ: See? Well, a vacuum chamber is a space that is completely void of matter. So this mica exists all by itself.
CARLOS CAMARA: So I had a roll of Scotch tape amongst all the other materials and tools that I had in front of me, and I'm feeling around with my hands because it's completely dark. And as I peel the roll of Scotch tape, I see that it makes more light than anything else that I'm trying.
MARC SANCHEZ: So Carlos and his team of researchers did what any curious scientist does.
CARLOS CAMARA: We naturally decided to take the roll of Scotch tape, put it in a vacuum chamber. And sure enough, it made more X-rays than anything else we had tried.
MARC SANCHEZ: Remember how exciting atoms can make them release electrons and X-rays? The same thing is happening here with Scotch tape. Carlos and the other researchers were actually able to use a few pieces of tape to take a crude X-ray picture of a finger. Once they did this, pieces of a puzzle started to fall into place.
CARLOS CAMARA: In particular, we discovered that not simply unsticking a roll of tape would make X-rays, but if you had the right materials, you can have simply two rollers rotating against each other, making X-rays. So at that point, it became clear to us that there was a possibility of actual useful applications of this very simple effect.
[SCOTCH TAPE BEING PEELED]
Our first product is an X-ray fluorescence analyzer. It's an instrument that can basically tell you what material you're looking at, and it tells you the composition.
MARC SANCHEZ: The device is this little boxy thing with a handle. It looks similar to a radar gun if you've ever seen one of those. And when you squeeze the trigger, it emits a burst of X-ray light.
CARLOS CAMARA: Every element has a unique X-ray energy fingerprint. And the way it works is that if you shoot X-rays at a material, you can excite the electrons of the material in the X-ray energy, and so the X-rays that glow back at you from the material uniquely identify what atoms are present.
MARC SANCHEZ: But what Carlos is really excited about is the possibilities for portable X-rays. His team is developing a portable X-ray device that is about the size of a soda can.
CARLOS CAMARA: In comparison, the most portable sources that would get the similar job done currently available are much, much larger and heavier, about the size of a small oven.
[SOUND EFFECT]
So imagine in disaster relief.
MARC SANCHEZ: So there's an earthquake or tsunami somewhere. Lots of people in need of medical attention.
CARLOS CAMARA: Imagine if you had a briefcase that could be just as good as an X-ray medical suite that you have in the hospital.
MARC SANCHEZ: It's not totally 100% as good as a hospital, but Carlos thinks that you could be on the ground with these suitcase X-ray machines, basically carrying the room of a hospital in one hand.
[MUSIC PLAYING]
And if you guys want to see triboluminescence in action, Carlos gave me a couple of really cool experiments you can try at your very own home. One is the Scotch tape method he used, and the other involves candy, specifically wintergreen candy, like LIFE SAVERS.
First off, you need to find a really dark space, maybe a closet, someplace where there's as little light as possible. Take either the tape or the wintergreen LIFE SAVERS into the space and let your eyes get used to the dark. This might take about four or five minutes, but be patient because it's worth it.
If you unspool the tape, you should see a faint blue glow coming from where the sticky part leaves the rest of the roll. And the LIFE SAVERS, they are going to glow green. You can either chew them with your mouth-- open, I guess-- or you can put them in a plastic sandwich bag and crush them with pliers. And there you have it, triboluminescence.
FRANKIE BROWNEAGLE: That's amazing.
MOLLY BLOOM: Thanks, Marc.
MARC SANCHEZ: You're welcome.
[THEME MUSIC]
FRANKIE BROWNEAGLE: X-rays are radiation.
MOLLY BLOOM: Or light.
FRANKIE BROWNEAGLE: Or energy.
MOLLY BLOOM: A part of the electromagnetic spectrum.
FRANKIE BROWNEAGLE: These high-energy rays can penetrate tissue and allow us to see our bones.
MOLLY BLOOM: And they can also help us understand the structures of the smallest proteins and molecules through X-ray crystallography.
FRANKIE BROWNEAGLE: And by picking up X-rays from space, we can learn a lot about the universe.
MOLLY BLOOM: That's it for this episode of Brains On!
FRANKIE BROWNEAGLE: Brains On! is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Many thanks to [INAUDIBLE], Vincent [? Monas, ?] Megan Treinen, Carol [? Zoll, ?] Vahan [? Baladuni, ?] and Andrew Gordon.
FRANKIE BROWNEAGLE: If you're a fan of Brains On!, consider leaving a review in iTunes.
MOLLY BLOOM: It really helps other kids and parents find out about the show.
FRANKIE BROWNEAGLE: And you can keep up with us on Instagram and Twitter.
MOLLY BLOOM: We're @Brains_On.
FRANKIE BROWNEAGLE: And we're on Facebook, too.
MOLLY BLOOM: And remember to head to BrainsOn.org to vote for the debate you want Marc and Sanden to tackle.
FRANKIE BROWNEAGLE: Thanks for listening.
[THEME MUSIC PLAYING]
Transcription services provided by 3Play Media.
