Long ago, people believed that the eye emitted invisible rays that struck the world outside, causing it to become visible to the beholder. That’s not the..
Long ago, people believed that the eye emitted invisible rays that struck the world outside, causing it to become visible to the beholder. That’s not the case, of course, but that doesn’t mean it wouldn’t be a perfectly good way to see. In fact, it’s the basic idea behind lidar, a form of digital imaging that’s proven very useful in everything from archaeology to autonomous cars.
Lidar is a sort-of acronym that may or may not be capitalized when you see it, and it usually stands for “light detection and ranging,” though sometimes people like to fit “imaging” between the first two words. That it sounds similar to sonar and radar is no coincidence; they all operate on the same principle: echolocation. Hey, if bats can do it, why can’t we?
The basic idea is simple: you shoot something out into the world, then track how long it takes to come back. Bats use sound waves — a little click or squeak that bounces off the environment and returns to their ears sooner or later depending on how far away a tree or bug is. Little imagination is needed to turn that into sonar, which just sends a bigger click into the surrounding water and listens for echoes. If you know exactly how fast sound travels in water, and you know exactly how long it took to hit something and come back, then you know exactly how far away whatever it hit is.
From there, it’s not much of a jump to radar, which does much the same thing with radio waves. The radar dishes we’ve all seen at airports and on big boats spin around, firing out a beam of radio waves. When those waves hit something solid — especially something metallic, like a plane — they bounce back and the dish detects them.
