How the Mandalorian Might See Through Walls

In episode 3 of The Mandalorian, Mando wants to spy on some Imperial remnants. (No spoilers here—I’ll just say it’s important for him to plan his next move.) So he goes up on a nearby roof and aims his Amban rifle at the wall of a building. Then, making an adjustment on his digital aiming scope, he is able to peer through the wall to see what’s going on inside.

Of course, it’s just a show. But it got me thinking about different ways we might be able to see through walls in real life. If you look at the physics involved, it’s not entirely impossible. Maybe the technology here is fictitious, but there are a few approaches that a clever Mandalorian inventor could take.

Let’s start with fundamentals. There are three different ways to see, but they all have one thing in common: Light has to travel from the object to the eye of the beholder. That’s just how vision works. And that’s true whether the beholder is a person or some type of futuristic sensor. With that in mind, let’s consider each of the three basic ways of seeing and look at the potential of each.

Illumination

Imagine you’re in a dark cave—it’s totally black. Then you switch on a flashlight and see a bear. It is not happy to be awoken. As you race for the exit, think about what just happened: Light traveled outward from your flashlight, bounced off the bear, and traveled back to your retina. What you “saw” was a reflection of the bear.

This is seeing by illumination. You use it all the time. It’s how you see your coffee mug on the desk. It’s how you see a tree during the day or a highway exit at night. Without some external light source, be it a desk lamp, the sun, or your headlights, you can’t see any of these things.

So, how would this work if you wanted to see through a wall? First you would need to send light through the wall. Unless the wall is paper thin (and I mean thin paper), that’s not going to work. Even if some light did pass through, it would have to reflect off the person on the other side and pass through again for you to see anything.

That’s just not going to work for your typical wall; in the Mandalorian scene on the planet Tatooine, the wall looks like it’s made of thick adobe. Forget that. Of course there are materials that allow light to pass through—we call these windows. If the Imperial remnants are hiding behind a window, they deserve what’s coming to them.

But wait! We’re thinking in terms of visible light, which is only one kind of electromagnetic radiation. In general, electromagnetic waves are produced when an oscillating electric field creates an oscillating magnetic field, which creates an oscillating electric field. These waves travel at the speed of light (3 x 108 m/s) and can move through empty space—unlike other waves (such as sound) that need a medium to travel through.

What if Mando uses some other type of electromagnetic wave? There’s a lot to choose from; visible light makes up just a tiny part of the electromagnetic spectrum, with wavelengths in the 400-nm (violet) to 700-nm (red) range. Going more big picture, the spectrum includes all these other types of radiation, from long to short:

  • Radio (1 mm – 100 m): Used in radios, cell phones, and Wi-Fi.
  • Infrared (700 nm – 1 mm): Used in thermal imaging and TV remotes.
  • Visible light (400 nm – 700 nm): All the colors of the rainbow.
  • Ultraviolet (10 nm – 400 nm): This is what causes your skin to tan.
  • X-rays (10 pm to 10 nm): Super tiny; a picometer is a trillionth of a meter.
  • Gamma rays (< 10 pm): Why does everyone think of the Hulk here?

For something like a brick wall, you can get radio waves and x-rays to pass through. So, what if you illuminated the subjects with x-rays or radio waves? Could you see them? Well, sort of. Although both of these pass through walls, they also mostly pass through people. It would be like looking at glass people through a glass window. Everything is glass.

But notice I said “mostly.” You CAN get this to work with radio waves, though it’s not easy. There is some reflection off a body (as well as the wall), and a computer can analyze that noisy backwash to determine where a person is on the other side of a wall. It’s real stuff. The same thing can be done with x-rays—it’s the idea behind the Z Backscatter Vans that are used to peer inside cargo vehicles for bombs or contraband.

Could Mando use one of these technologies to see through the walls? Yes, it’s at least plausible. His sniper rifle could emit some type of radiation (radio or x-rays) and detect the reflected stuff to form an image.

Shadows

Sometimes you can see a thing by not seeing it. Suppose the bad guy’s in a room with a flimsy window shade, like in old film noir movies. If the room is dark, you can’t see anything. But if there is a bright lamp, and he walks between the lamp and the wall, you’d see his shadow moving. You could “see” the guy by looking at the hole in the light.

If you’ve ever had a medical x-ray, this is exactly what happens. There is an x-ray source on one side of your body with an x-ray detector on the other side.

Illustration: Rhett Allain

Could you use this to see through walls? Absolutely. Would it be useful? Not really. You’d need a source and a detector on opposite sides of the target. The Mandalorian would need to place an x-ray emitter (a radio source would probably work too) on the back of the building, then run around to the front to use his x-ray detecting sniper rifle to see the shadows.

Actually, that may sound silly, but this shadow method was recently used to explore the interior of the Great Pyramid in Egypt. Researchers placed muon detectors under the pyramid. A muon is a particle in cosmic radiation that continually bombards Earth. By looking at the muon signal strength in different directions, they could estimate of the amount of material it passed through. The resulting map revealed a large, previously unknown chamber.

Emission

There is one final way to see things. If you have a lightbulb in a room, you don’t need light to reflect off it in order to see it. The bulb produces its own light through emission, and that light travels directly to your eye. Your computer screen is doing this too. It creates its own light so you can read this sentence right here—even in a dark room.

Of course, that light wouldn’t go through a wall, but let’s again think outside the visible spectrum. It just so happens that objects around normal room temperature produce light in the infrared spectrum. Our human eyes can’t detect this light, but an infrared camera can. Trust me, these cameras are awesome (and way cheaper than they were just 10 years ago).

So, could the Mandalorian be using an infrared scope on his rifle to see through walls? Nope. Although you can see some crazy stuff in the infrared spectrum, you can’t see through walls. In fact, you can’t even see through windows. Check this out: It’s two pictures of my son on the other side of a glass door. The one on the left is an infrared image, and the one on the right is a visible-light image.

Illustration: Rhett Allain

Can an infrared sensor see through any kind of wall? Yes. Well, it’s not really a wall—but infrared light does go through some kinds of plastic. Here’s my son holding up a trash bag. Infrared on the left and visible light on the right:

Illustration: Rhett Allain

That’s pretty awesome. Too bad walls aren’t made of trash bags, though.

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