Humans have five senses: sight, sound, smell, touch, and taste. That's not true; our senses are both more refined and more blended than that, but those categories help describe the bounds of our understanding. The universe is huge and we're small, meaning that there are many things we can't sense/understand. Just off the top of our head, we can think of

• the other 8+ dimensions the universe needs to exist.
• the non-light part of the electromagnetic spectrum.
• miracles.

Lots of those things we haven't quite figured out yet (how do blankets work?), but some things we've got down. Or at least parts.

We've been able to overcome our missing senses by

• living vicariously through comic book characters.
• inventing technologies to "see" for us.

Between the two options, we'll call the second slightly more realistic. Sometimes we need to see without actually being able to…see. Radar's one of those non-comic book solutions to seeing the electromagnetic spectrum that we can't actually sense. The electromagnetic spectrum is a spectrum filled with energy that moves at different heights and speeds. It deserves its own learning guide and it does (thank goodness). Visible light is part of it, but only a sliver.

Literally. Visible light makes up a tiny part of the spectrum because the wavelength (or size) of the waves is microscopic. Human eyes take in the visible light. We can see because that light scatters after hitting objects. Our brains take that scattering and process how it scatters to form images. Colors are just the way our brains organize the wavelength sizes when they separate.

Mind. Blown.

There's a limit to what humans can see. We only see things scattered from visible light—explaining the mystery of why it's called visible light—but there's still the other 99% of the electromagnetic spectrum that's completely invisible. One of the types of energy is called radio frequency, which we can use to hear music stations over frequency modulated "FM" or amplitude modulated "AM" radio. Then there's microwave frequency, which we harness to heat Hot Pockets as we try to convince Mama Shmoop halfway across the country that we're eating healthy.

No? Just us?

These energies are running around our universe and we don't really see them—but we use them. How? Guess and check experimentation, really. But one of the first times humans really used radio waves and microwaves was when the military developed a technology called RAdio Detecting And Ranging—aptly shortened to RADAR.

Don't think Radars are just for the soldiers, though.

Radar has made

• cell phones
• weather predictions
• computers
• radio astronomy
• things we haven't even invented yet (probably)

possible. And it all started with James Clerk Maxwell, who organized a system of equations that explained the behavior of electromagnetic waves:

• how they're created. 
• how they travel. 
• how they're destroyed. 
• how they can be used to create larger or smaller packets of energy.

For the rest of the electromagnetic spectrum, there's always comic books.

The electromagnetic spectrum is all around us. Whether you like it or not, you're bathing in its energy right now. We just happen to be able to use one of the types of waves to find and locate objects without visible light. Using radar is like having x-ray goggles, except…radars actually exist.

Can you imagine a world where airplanes had to stop midair because the pilot can't see through a storm? How about if we couldn't predict when a hurricane would form or where it moves? When you get right down to it, we wouldn't be where we are today without using the electromagnetic spectrum. The applications of radars are everywhere and literally save lives.

Not bad for a microscopic wave.