You can't talk about radars without talking about radio. No, it has nothing to do with the Top 40 Taylor Swift songs of this year or Cecil Baldwin's dreamy voice.

[Swoon]

No, when we talk about radio, we mean radio waves. That part of the electromagnetic spectrum with waves longer than a human is tall. In fact, some wavelengths are as long as a building is tall. We're talking about the tallest building in a town with a law stating you can't build anything larger than ten stories.

That's a pretty big wave.

Making Waves

Alternating currents are created from direct current (thanks to some complex equations from Maxwell), which we can use to create moving waves of energy using different materials. But what materials to use? After searching through a long list of materials like

• rocks
• different metals
• chocolate
• burlap

we figured out that crystals are great at creating reliable waves for a radar. Especially since they have precise frequency phase centers—the place where electromagnetic waves spread spherically outward. Since they're so exact, we get more information, which means that the technology tells us more.

Once the crystal-laden oscillator creates a wave of alternating current, it's sent to an antenna—or a series of antennas—that then turns that alternating current into an electromagnetic wave. How the wave is created from the antenna involves

• trigonometric tricks.
• differential equations. 
• basic facts about metals (like that they have a zero potential energy).

All that put together means that you can relate Faraday's and Ampere's law to get the wave equation. Of course, it's a little more complicated since we also need to ensure the target object is far enough away from the radar antenna.

When we say that it needs to be far away, we mean that it needs to a number of wavelengths away, which depends on—you guessed it—the length of the wave. It's all very fuzzy and relative, though, since the length of the wave can change based on its frequency. It also depends on the diameter of your antenna, but generally, if you shrink a radar, what's far enough away is going to shrink with it.

As the electromagnetic wave leaves the radar (in spherical ripples), the radar system sends out waves from many phase centers at different frequencies. All those different waves run at different frequencies, but they actually come together to form a predictable pattern.

Finding Objects in the Sea of Waves

Once you change the medium they're moving through, one or more of the frequencies will change, which means that you've found something. For example, a particular frequency wave may reflect off a cloud while another frequency will reflect off of grass. The frequency differences—known as coloring—helps us piece together the image of a particular scene.

We also need to think about the waveform type—or the shape of the wave as it moves through a medium. Sine waves are great, but they aren't the best waveform when it comes to differentiating between metal and plastic objects. If we change

• the antenna shape 
• the direction of the wave's movements 
• the waveform itself

we can figure out whether a moving object of is metal or plastic.

Covering all Angles

One more thing is going to make the image a whole lot clearer. If we separate the transmitting and receiving antennas, we're going to get way more viewing angles. Think of it like sitting in a theater. If you're on the left side balcony, you'll see most of the stage, but it won't be too clear and the curtain might get in the way in the middle of an actor's monologue. If you figured out a way to sit on the left balcony, the right balcony, and a couple of seats in the orchestra at the same time, you would have a much clearer image than one seat can possibly give.

(Also you'd be The Flash.)

Despite the fact that watching a show from four different seats is physically impossible for those of us not doused with electrified chemicals, the idea's still the same for radars. Because we have more angles to see things, we're going to have a much clearer image. Actually, this is a great metaphor because we'll be able to see things that you can't usually see with a human eye.

(We smell a physics-based DC comic book hero in the making.)

Other Radars

Okay, but all this relies on antennas always working perfectly, which is sometimes…less than true. To know which frequency phase centers to use to detect an object, we need the transmitting antennas working perfectly, but they can't always do that. Luckily, you don't actually need transmitting antennas at all. (Helpful, right?) Multiple radar receivers can actually fake a phase difference as a way to measure and guess accuracy and resolution of the radar image. These passive radar systems (as they're called on the streets), don't work as well as normal radars, but they take much less energy.

Sometimes saving energy is more important than having the perfect image.

There's another way to get around having imperfect antennas, and it involves airplanes. (Our favorite kind of MacGyvering.) Antennas have a fixed size, but if you move them while carefully timing the phase centers (and use some trigonometric identities), you can make its efficiency better by putting it on something moving like—wait for it—an airplane. This type of radar is called Synthetic Aperture Radar (SAR). The aperture is the way we measure how well an antenna can catch radio waves. We're basically faking the aperture using movement, but it works.

Not too shabby, radar. Not too shabby.