Plasmas and Rainbows!
Experiment with the fourth state of matter! Portions of this video contain moving and flickering lights.
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Steve: We took the pewter inside the cups. Froze it rock hard. Hard things ring better than soft things do. That's why your pillow doesn't ring when you smack your head against at night.
The bells also signal the end of what we're going to do with the nitrogen. But, it's not the end of our time here. It just means I can take a little bit of the extra, and I can put some in my lemonade, and I can take off the goggles and gloves, and then I can ask you, states of matter, how many?
Someone in the Audience: Three.
Steve: Actually, four main ones. You have solid...
Someone in the Audience: Liquid, gas, plasma.
Steve: Good. Solid, liquid, gas and plasma.
And, I don't want to say plasma is the weird one. It's actually the most common state of matter we see in the universe.
What a plasma is though, it's what you get if you take a gas and you heat it up. Right? So if I take a gas, I make it get hotter, the particles move faster. Eventually, I can get hot enough, that the particles move quickly enough, that when they smack into each other, electrons get knocked off.
And, so, that's what's happening inside a plasma. I have electrons that have been knocked off their atoms. Atoms that need electrons. And they can recombine. And, if they do, the electrons need to give up some energy. And that can come off in the form of light that we can see.
On earth you have plasma. The spark between the domes was a plasma. Lightning's a plasma. But the problem that plasmas have on earth is it's just too cold. It's too cold for them to stay as plasmas on their own for very long.
Not true in the bulk of the universe. The bulk of the universe we actually see with our eyes is in the form of a plasma. The sun is a plasma. All the stars out there are plasmas. There's a lot of plasma out there.
And it's not that hard to make a plasma. This kind of light bulb, fluorescent light bulb, when it runs there's a plasma on the inside. Neon signs they use for advertising are plasma. And we're gonna make some plasmas here.
What I have are four different samples of elements. I have nitrogen, helium, mercury and neon.
I'm going to change them to a plasma by heating them up using this thing. This is called a Tesla coil. And, when I turn it on, it gives off radio waves, which we don't see. But if I turn on my little radio here, we can detect.
Steve: Right? It's not most exciting channel ever. But it is there. Better than a few of them, too. And, we can make little baby lightning, as well.
So, what we're gonna do. We're gonna turn off the lights. And, with the lights off, we'll light up the plasmas. Tell me the colors. Okay? Lights are going out. Fluorescent bulb is going on. What color?
Someone in the Audience: White.
Stev: Pretty much white. The nitrogen?
People in Audience: Purple.
Stev: Pretty much purple. The helium?
People in Audience: Orange.
Steve: The mercury?
People in Audience: Blue.
Steve: And the ne... Whoop, can we turn off that flash, please? Red. Good. Lights back on, please.
Good. So, helium. The element helium was actually found on the sun before it was found on the earth. And it was found on the sun by studying light.
Look at lights above us. They're or more or less white. They're more or less white because they more or less have all the colors mixed together.
Have you ever seen a rainbow? Where the colors come from? Yeah, it's in the - it's in the light already.
Right? The reason why you don't see rainbows all the time is, if your eye actually gets hit by more than one color on the same spot, those colors get blended together for you. And, one way that your brain says "Okay, fine, I'm going to call that white" - every single color hits the same spot.
What happens with a rainbow, the light goes through the raindrop and then the light bends. And it turns out different colors bend by different amounts. So, when you look at it, the colors are spread out for you. And the red hits one part of your eye. The violet hits a different part. All the other colors are in between. And you can see the colors because they're not getting blended together in your eye anymore. Put them all together again, your brain's gonna call it white.
And there are other ways that your brain calls things white, also. How many of you have ever looked at a TV set or a computer screen? Three colors. They only show you three. Which three?
Someone in the Audience: Red. Cyan.
Someone else in Audience: Blue, red.
Yet another person in the Audience: Green.
And yet another person in the Audience: Yellow.
RGB. Red, green, blue. And, by adjusting how bright the red, green and blue are, your brain says "Oh, that's white." Or, "Oh, that's yellow. Oh, that's orange. That's whatever."
One of these fooled you. One of these four, everyone told me the same color. That color's not there. It's different colors blending together, and your brain is calling it something else.
Now, scientists don't call rainbows, rainbows, they call it the visible spectrum. And, it turns out, if you study a plasma's spectrum, you can actually tell which elements are in there because of how we're making the light.
What we're doing with this, we're reaching in with the radio waves, we're grabbing electrons, and then we're pulling them away from the nucleus.
Then we let them go.
When we let them go, they fall back in towards the nucleus. But, electrons in atoms don't fall like regular things fall. It's more like if you trip and fall down the stairs. And they just sort of go "whoomp, whoomp, whoomp" down these different levels.
Electrons in atoms have to be in certain levels, certain shells. And, when they fall, they have to go from one shell, to another shell, to another shell. And, again, it's kind of like tripping and falling down the stairs. And, if the shells are far apart, that's a lot of energy, you get purple. If the shells are close together, that's a little bit of energy, and you get red.
The thing, though, is the way the shells arranged, depends on how many protons are in the nucleus. And, if I change how many protons are in the nucleus, what have I also changed?
Someone in the Audience: The element.
Steve: The element!
Yeah. So it really depends - you can use like a fingerprint based on light to figure out what the element is because it's gonna be different for every element. Which is great, if you can see the rainbows.
That's what these things are for. These are called rainbow glasses or diffraction glasses. You put them on your face, look at the source of light, spreads it out for us so you can see the colors that make up that light.
You'll get a pair of these to keep... If you promise. Say "I promise not to look at the sun."
Audience, mostly: I promise not to look at the sun.
Steve: Say "Seriously, I promise not look at the sun."
Audience, mostly: "Seriously, I promise not look at the sun."
Steve: Why don't you want to look at the sun?
It'll burn your eye.
Have you ever played with a magnifying glass and sunlight?
A couple of people in the Audience: No.
Steve: And you can burn stuff with it?
Well, you're eye works the same way. You have a lens in your eye, just like the magnifying glass. If you go staring at the sun, it's going to focus the light on the back of your eye. Keep it there for too long, you're gonna burn that part of your eye. And you don't feel it happening. You don't have nerves in your eye that sense pain. So, you can burn your eye and not even know it's going on.
Part of the problem these glasses, they don't protect you from anything. They just make the world pretty. So, don't put these on your face, go "Huh, huh. Sun. Huh, huh. Bright." Because you're going to fry your eye.
Okay. There are ways to cheat. If you must know what the sun's pattern looks like, they're ways to cheat.
The easiest way to cheat...
Take your glasses off...
Shine the sunlight through them. You can project the rainbow on the ground.
Another easy way to cheat, is if you have a cell phone with a camera, put this over the camera lens, point that at the sun, take a photo. Now, you might burn out the camera. I don't guarantee that you won't. But, if my only choices are "I have to use my eye," or "I have to use the camera," pick the camera. Because, if you toast the camera, it's annoying, but they make them. You can get another one. If you fry your eye, that's going to be stuck there forever.
Okay? Another easy way to cheat is at night. How do we see sunlight at night?
Someone in the Audience: The moon.
Steve: The moon! The moon right now is a little bit past full, so wait a bit after sunset, it'll come up in the sky.
Other things that are fun at night are street lights. They make different kinds. You can tell they're different because they give you different patterns. Car headlights are fun. But don't stand in the middle of the street in the middle of the night with these glasses on going "Huh! Car!" because, you're going to get run over.
Okay, so again, these do not protect you from anything. If your kid sister beats you up every day when you get home, she will beat you up if you're wearing these. She's just going to look better doing it. She's gonna have these little rainbow fists of fury as she comes at you.
But they won't protect you from her.
They won't protect you from a truck.
They won't protect you from the sun.
Okay? So, use your brains when you use these glasses.
If we could have some of the teachers, adults, chaperones, help us pass these things around, please.
An Odd Voice: A few minutes later...
Steve: First thing I would like you to do... Take your glasses... Pop 'em on your face... Look up.
Someone in the Audience: Beautiful!
Steve: So now... Now we can see the colors in the lights above us. And, what we're going to do, we're going to relight our plasmas in the dark.
If you are ready. Lights are going out. Fluorescent bulb is going on.
Steve: So... this one. Pretty decent full spectrum light. It is missing a little bit between, ahh... green and yellow. But it has a lot of the colors. If you have fluorescent lights at home, you may notice that it gives off different patterns. They do make different kinds of fluorescent lights. So, you can get different patterns with different fluorescent lights.
Someone in the Audience: Whoa.
Steve: Look for missing colors. Look in between red and orange, there's a little dark line, that color is gone. In between green and yellow is a thicker dark line. And the blues are gone. It's missing blue. Part of the reason why it doesn't look white when we mix it up. It's missing some of the colors.
Helium is different.
Steve: Helium basically just has four colors. Right? There's a red, there's kind of a yellowish orange, there's a bluish green, there's a purple. Not the same situation we had with nitrogen. Right? Nitrogen has most of the colors, missing a few. Helium only has a handful of colors. It's missing everything else.
Steve: Mercury is kind of the same deal that we had with helium in just they're a few colors. And, if I call them out, it's almost what I said for helium. There's a faint red. There's an orange, there's a green, there's a purple. But they're not the same. Right? The spacings are different. Which means the colors are different. The brightnesses are different. Those are two different patterns there.
And, again, way different than nitrogen.
And then, finally, neon.
Someone in the Audience: That's a good one.
Steve: Lots of red, orange, yellow. Little bit of green. But not every red, orange and yellow. You have gaps inside there as well.
So, this is how astronomers know what stars are made of. You don't need the star, you just need the light. And, by studying the patterns in the light, you can figure out which elements are in the star.
So, of the four... The nitrogen... The helium... The mercury... The neon...
Which one fooled us?
Someone in the Audience: Mercury.
Steve: Mercury! Very good! Mercury.
That blue light does not contain blue. It's made from purple, green, orange, red. Your brain mixes it up and says "Blue!" Which is super cute of you, brain. But there's no blue in that light.
Speaking of lights! Lights, please.
Steve: Now... one more super-quick thing.
What... is this?
Some people in the Audience: Pen? Pen. Pen?
Steve: My laser pointer.
Someone in the Audience: Oh.
Steve: With the lights out, and your glasses on, I'm going to shine the laser on the wall. You tell me the colors in the laser light.
Audience: General noise.
Audience: Louder general noise.
Steve: What colors?
Steve: Just green. Right? Lasers are pretty much just one color of light.
If I try to take a single color, break into a rainbow, I don't get a rainbow, because I only have the one color to play with.
It's like if I give you a green crayon. And I say "Here's a green crayon. Draw a rainbow." You're going to go, "Here's green," because that's all you have.
But, it's fairly useful that it is just one color.
So, unfortunately, that is about the time that we have. Before we head out, a couple of things. First, if you would like a copy of the Table of Elements, you may grab a copy of the Table of Elements.
If you want to see other things, we have a bunch of videos up on YouTube.
Some of the things you've seen, a lot of the stuff you haven't.
So, if you want to see "Liquid Nitrogen in a Microwave."
If you want to see "Freezing Liquid Nitrogen."
If you want to see "Giant Koosh Ball in Liquid Nitrogen,"
go to YouTube, search for Jefferson Lab, or grab one of these things.
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