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 you might be able to see through a wall 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 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 sensor. With that in mind, let’s consider each of the three basic ways of seeing and look at the potential of each.
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 the light reflected off 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, obviously; cell phones and Wi-Fi too.
- Infrared (700 nm – 1 mm): Used in thermal imaging. It’s also what your TV remote uses.
- Visible light (400 nm – 700 nm): All the colors of the rainbow.
- Ultraviolet (1 nm – 400 nm): This is what causes your skin to tan.
- X-rays (~ 1 pm): Getting super small now; a picometer is 10–12 meters.
- Gamma rays (10–12 meters): Why does everyone think of the Hulk here?
social experiment by Livio Acerbo #greengroundit #wired https://www.wired.com/story/how-the-mandalorian-might-see-through-walls