Radiation: Energy from a Distance Quiz

Answer: Electromagnetic radiation

Okay, if you hear the word 'radiation' and immediately picture glowing green barrels or someone walking stiffly around in a lead suit, you just might have watched too much television (my people!).

The truth is actually much less dramatic. Radiation is energy traveling through space, and we're being bombarded by it all the time. It's not intrinsically good or bad, it just is. The kind of radiation, the amount you receive, and the duration of that reception all play a role in how much our bodies care for the experience.

Light itself is radiation, which means everything you see is produced by it. Radio waves? Radiation. Microwaves warming up your leftover pizza? Also radiation.

These are all parts of the same family known as electromagnetic radiation, which is simply energy traveling through space as oscillating electric and magnetic fields.

Eww. How about an analogy?

Imagine electromagnetic radiation as a tiny, invisible bundle of energy that moves outward like a ripple in a pond. However, instead of moving through water, it moves through empty space or the air or sometimes even your body. This energy is made up of electricity and magnetism. They work together like best buddies, constantly pushing each other along to keep the wave moving forward. It's not a perfect analogy by any means, but it's something to build off of if you're new to the concept.

Anyway, those invisible bundles of energy? They're called photons, and you're being absolutely bombarded with them right now. (Don't panic!)

The electromagnetic radiation family is quite large. On the low energy end of the spectrum, you have radio waves with wavelengths that can stretch for miles, allowing you to pick up music, sports talk, and the latest conspiracy theories, all from the comfort of your car. A little more energy, a little higher up on the spectrum, we get to microwaves and infrared waves. Keep strolling up the spectrum, and you reach visible light, that narrow little slice our eyes evolved to notice.

Past violet, things get very spicy: ultraviolet, X-rays, and gamma rays. Same basic phenomenon, just with shorter wavelengths and more energetic photons. These are the parts of the electromagnetic spectrum that can be a danger in high doses.

If you think of the spectrum as a piano keyboard, we can only see a small cluster of keys in the middle of it. And those 'higher-frequency' keys to the right of what we can see? Best to leave those to the professional keyboardists.

So, the light bouncing off your hand right now? Totally harmless electromagnetic radiation. In fact, your hand is also sneakily emitting infrared radiation (Eek!) because it's warm. Everything above absolute zero does this. So, relax. Radiation or no radiation, we're not ready to film your superhero original story just yet. The next question helps explain a big reason why not.

Answer: The ozone layer

For us, nothing produces more energy and radiation on a consistent basis than that big bright ball in the sky.

The ozone layer lives a sedentary life mostly in the stratosphere, about 10 to 30 miles (roughly 16 to 48 kilometers) above the ground. It has one vitally important job, at least from our perspective. It absorbs a big bulk of the Sun's ultraviolet radiation before it gets the chance to fry the living daylights out of everything on the surface. Without it, it's easy to picture a world where gingers would be catching fire, and immolation is not the goal of science.

Ozone itself is just a molecule made of three oxygen atoms stuck together. Oxygen prefers to hang out in monogamous pairs (O₂), which is what we breathe (and what makes immolation so much easier). Sometimes, O₂ likes to get a little freaky and invite company over. Enter ozone or O₃. When UV light hits ozone, it absorbs the energy and splits apart. The pieces then recombine with other oxygen molecules to form new ozone. It sounds weird, but ozone is always doing this nutty trick. Just soaking up UV waves, breaking apart, and then reforming with new partners. Whatever keeps your marriage fresh, I guess.

Despite protecting us from all kinds of badness, our bodies don't exactly love it. Ground level ozone is particularly nasty for people with asthma or other medical conditions.

If you're wondering, most of the nastier short wavelength Electromagnetic radiation (EMR) such as gamma rays and X-rays is absorbed much higher up by nitrogen and plain old monogamous oxygen molecules in the thermosphere and ionosphere.

Answer: X-rays

You know what X-rays are. You've probably gotten them.

But do you know what X-rays ARE?

Well, let me tell you. They are a high-energy form of electromagnetic radiation (them again) with wavelengths shorter than visible light. That's the kind that can be dangerous with prolonged, intense exposure. Because they carry more energy, X-rays can pass right through soft tissues like skin and muscle. Your bones are another story. They're denser and absorb x-rays much more easily.

The result is a shadowy image where bones show up bright and clear (well, mostly), while everything squishier looks much darker.

The discovery of X-rays happened in 1895 when German physicist Wilhelm Conrad Roentgen was playing with electrical currents in vacuum tubes, as one does. He noticed a mysterious kind of radiation that could pass through materials and fog photographic plates. When he tested it by taking an x-ray of his wife's hand (for 15 minutes), the resulting picture clearly showed her bones and her wedding ring.

A couple of centuries earlier they would have both been burned at the stake. As for Mrs. Roentgen, well... she wasn't particularly thrilled either, reportedly saying "I have seen my death". I'm guessing she was a glass-half-empty kind of person.

Still, science was pretty impressed by the feat, and Roentgen received the very first Nobel Prize in Physics in 1901.

Answer: Ionizing radiation

Your boring basic run-of the mill carbon atom has 6 protons, 6 neutrons, and 6 electrons. But what if we play doctor? Remove a proton, and it's not carbon anymore, so we'll just leave them alone, because boron is lame. Add or remove a neutron we have an isotope. Same atom, slightly different properties, some of which can make uranium more willing to go boom.

Add or remove an electron? Well, that's an ion. Since we're adding or taking away a charged particle (electrons have a negative charge) from a neutral atom, the protons and electrons don't balance, and the atom is charged.

Ionizing radiation may sound like something available only in a supervillain catalog... and yeah, that's kind of what it is.

It has enough energy to knock electrons off atoms or molecules. When that happens, the atom becomes an ion. This act of atomic vandalism can cause harm to human cells by disrupting chemical bonds. Hence the whole supervillain thing.

Examples of ionizing radiation are many. X-rays, gamma rays, and some types of ultraviolet radiation are all electromagnetic radiation that will happily steal an atom's lunch money. Other forms of high-energy radiation, such as alpha and beta particles, do the same. These carry enough punch to interact strongly with matter.

Inside living tissue, that can mean breaking DNA strands or altering molecules that cells rely on to function. Not cool. In high doses over prolonged periods, it can do a lot of damage.

However, in controlled amounts, ionizing radiation can be incredibly useful. Medical imaging, cancer radiation therapy, and sterilization of medical equipment all rely on the same basic principle.

Meanwhile, most of the radiation we encounter every day is non-ionizing. Radio waves, microwaves, infrared, and visible light simply do not have enough energy per photon to yank your electrons. They can still transfer energy, often as heat, but they do not typically rearrange atomic structures the way ionizing radiation can.

So the Wi-Fi signal bouncing around your living room is energetic, sure, but it is not out there ripping electrons loose like a hooligan.

Answer: Infrared radiation

Infrared radiation sits just beyond the red end of the visible spectrum, the relaxed low-energy part of the spectrum. Our eyes cannot see it, but our skin can definitely feel it. When sunlight warms your face or when you hold your hands near a campfire, that heat is mostly infrared radiation transferring energy to your skin. The wavelengths are longer than visible light, which means the photons carry less energy, but there are plenty of them moving around doing their happy little warming work.

And like any radiation too much for too long is bad. Touching a hot pan on the stove is called conduction, and you learn quickly not to do that. Putting your hand a centimeter away from a hot pan? Well, that's radiant heat searing your hand. (Stop that.)

Anything with a temperature above absolute zero gives off infrared radiation. That includes your coffee mug, your house cat, the pavement, and even you sitting there reading this on the device of your choice. Humans constantly emit infrared energy as body heat.

That's how thermal cameras work. Instead of seeing visible light, they detect infrared radiation and translate it into images where warm objects glow brightly. You've probably seen military footage shot in darkness. Predator-vision.

TV remotes use infrared signals to talk to your television. Weather satellites use infrared imaging to monitor cloud temperatures and storm systems. Astronomers adore infrared telescopes because infrared light can pass through clouds of cosmic dust that block visible light. You can totally see things that are behind other things. How cool is that? Let's pour a glass for infrared radiation!

Answer: Radioactive decay

You've heard of radioactive decay, although you may not know you have. When people say this ancient wooden sculpture of a rubber chicken is 16,000 years old, scientists are using the properties of radioactive decay to get that estimate. It's also indirectly responsible for the demise (or not) of Schrödinger's cat.

It happens when an unstable atomic nucleus finally decides it has had quite enough of its current arrangement, thank you, and spits out particles or energy to reach a more stable state. During this process the atom can actually change into a completely different element. For example, uranium atoms can decay through a long chain of steps that eventually lead (the verb) to lead (the noun).

The particles or energy released during radioactive decay can take several forms. Alpha decay sends out a chunk made of two protons and two neutrons, which (spoiler) is really just a helium nucleus. Beta decay involves the transformation of a neutron into a proton (or vice versa) with the emission of an electron or positron, the antimatter evil twin of the electron. (You can tell a positron from an electron, because the former has a black mustache.)

The timing of this decay is unpredictable for any individual atom, but large groups of atoms follow very precise statistical rules. That is where the idea of 'half-life' and probability comes from.

Schrödinger's famous thought experiment from 1935 used radioactive decay as the random trigger in a very complicated setup involving a sealed box, a detector, a vial of poison, and an unfortunate cat (maybe). If a particular atom decayed, the detector would release the poison. According to quantum mechanics, until someone actually looks inside the box the system could exist in a superposition where the cat is both alive and dead. The point was not to kill imaginary cats but to highlight the odd implications of quantum theory when applied to everyday objects.

The cat thing was meant as a jab at the Copenhagen interpretation of quantum mechanics. Not to be outdone, particle physics just got weirder, suggesting the possibility of multiple universes and whatever else they've been up to lately.

Answer: Radium

Marie Curie and Pierre Curie stumbled upon radium from a mineral called pitchblende, once used for coloring glass and ceramics, and now used to make nuclear fuel. This discovery came during their investigation of strange radiation coming from uranium ores.

With the help of an electrometer designed by Pierre Curie, Marie Curie noticed that pitchblende was far more radioactive than uranium alone could explain, which meant something else in the rock was doing the radiating. Well, after months of painstaking chemical separation, which we'll just skip past because we can, the Curies identified a new element. They named it radium, from the Latin word 'radius', meaning ray. A fine name.

Radium quickly became famous for its strong radioactivity and the cool glow-in-the-dark blue color it produced in radioluminescent materials, like zinc sulfide. During the early 20th century when soft drinks contained cocaine and heroin was marketed as a cough-suppressant for kids, we had a brief and unhealthy obsession with the stuff (probably because everyone was too hopped up on coke and smack to care).

It appeared in glow-in-the-dark watch dials (cool!), health tonics (yum!), cosmetics (whoa!), and lots of other products that are usually NOT associated with intense and dangerous ionizing radiation.

Well, lots of very bad things happened, particularly to the workers who dealt with radium-based paint. If you're not familiar with the story of the 'Radium Girls', I suggest you put that on your list of things to Google. Long story short, lessons were learned the hard way.

Answer: PET scans

PET is short for 'positron emission tomography'. Positron is the cool part. That's the antimatter version of an electron.

PET scans utilize some of the coolest science tricks in modern medicine. A patient is given a tiny amount of a radioactive tracer, often a glucose-like molecule tagged with a positron-emitting isotope such as fluorine-18.

So, anyway, as the tracer moves through your body, cells with high glucose metabolism absorb more of the tracer. For example, cancer cells tend to be metabolic monsters, sucking up more of the tracer and making them easier to spot when the magic happens.

And that magic is radioactive decay, which we learned about earlier. When the radioactive atoms decay, they emit positrons. That antimatter particle doesn't have to travel far at all before it bumps into an electron, and when the two meet they annihilate each other. BOOM!

Okay, it's not a dramatic science-fiction type earth-destroying explosion, but it IS a neat little conversion of matter into energy. The result is a pair of gamma rays zipping off at the speed of light in opposite directions.

PET scanners detect those gamma rays and use their paths to reconstruct detailed images showing where the tracer accumulated inside the body. And if that isn't the coolest toy in the hospital, I don't know what is.

I told you it was cool. This is a great icebreaker at parties.

Answer: Alpha radiation

Alpha radiation is made up of alpha particles, but you don't need me to tell you that. These particles are essentially helium nuclei flying through space. Each one of these guys contains two protons and two neutrons. No electrons. In other words, it is the same core you would find inside a helium atom, just without the civilizing cloud of electrons that keeps everyone happy.

Alpha particles are commonly emitted by heavier, unstable elements such as uranium, radium, and polonium as their nuclei rearrange themselves into more stable forms.

Despite being energetic, alpha particles are actually pretty easy to stop. A sheet of paper, a layer of clothing, or even the outer dead layer of your skin generally block them without problem.

That sounds reassuring, and it absolutely is... as long as the radioactive material stays outside your body. If alpha-emitting substances are inhaled or swallowed, those particles can dump their energy directly into nearby cells, which is a very unkind thing to do to your internal organs.

Alpha radiation played a major role in the early days of nuclear physics (and radium watch dials). Ernest Rutherford famously used alpha particles in his gold foil experiment in 1909.

What Rutherford did was fire a stream of alpha particles at a thin sheet of gold and notice how some bounced back. In the end, he determined that atoms must have a tiny, dense nucleus at the center. Before that, many scientists pictured atoms more like fuzzy blobs of positive charge with electrons sprinkled throughout. This was really the beginning of our understanding of the structure of an atom. Way to go, Ernie!

Answer: Geiger counter

The Geiger counter is the gadget you see in movies whenever radiation comes up. It's that weird handheld device that clicks faster and faster as radiation levels increase, a sound that is indelibly linked in our minds to nuclear labs, disaster movies, and the occasional Cold War documentary.

Inside the device is something called a Geiger- Müller tube filled with gas. When ionizing radiation passes through the tube, it knocks electrons off atoms in the gas, creating a brief electrical pulse. The instrument detects those pulses and translates them into those clicks you know and love.

Those clicks aren't for dramatic effect. Each one represents a wee interaction between radiation and the detector. By counting how often those pulses occur, the device can estimate the intensity of radiation in your environment. Geiger counters are commonly used to detect beta and gamma radiation. Alpha particles require a special thin window built into the casing. You know how easily they deflect off surfaces if you've been paying attention.