Astronomy Cast- Radar

So Radar is one of those technologies that changed

everything

but it also changed astronomy and ground-imaging -- tracking asteroids with

great accuracy, allowing spacecraft to peer through Venus’ thick clouds and

reveal secrets through the Earth’s shifting sands. So radar’s reflected light, flashlight shining on wall is reflected light, and in the other case, you’re looking at a light source. So looking at a radio source with radio astronomy and looking at a star or a galaxy with an optical telescope is looking at a light source as well.

In the late 1800s, in the 1880s and 1890s, we

started to realize that light was more than what we could see with our eyes,

and scientists started realizing, “Hey, I can create radio sources, and then

detect those radio sources. Hey, I can create a constant sound in radio and

then reflect that off of something else and by looking for how the reflected

light comes back, how long it takes to come back, I can realize there’s

something out there.” So just as we were figuring out how to do radio

broadcasts, hand in hand, we were realizing that when radio reflects off of

things, well, that reflection means something there, and that’s kind of cool.

There’s a rather

frustrating story related to Pearl Harbor. America, Great Britain, New

Zealand, Russia – nations all around the world -- were struggling to figure

out how to use radar to detect incoming ships, to detect incoming aircraft, to

basically figure out, “Holy ‘expletive!’ We’re about to get killed!” and be

able to get out aircraft, be able to get people into shelters ahead of time to

help save lives, and we hadn’t gotten to the stage yet of everyone in the

military fully understanding the power of radar to detect things, and when

you don’t have fully trained leaders, bad decisions get made. So at Pearl

Harbor out in Hawaii, there were a couple of privates who decided to get in

a couple extra hours of training on radar, and these were radar stations that

were actually supposed to be shut off, and basically their truck hadn’t come

to take them off to get a meal, so they turned on the equipment and started

practicing, and while they were sitting there practicing, they realized that

there was a larger flock of airplanes than they’d ever seen heading towards

the Hawaiian Islands, and they called this in, but unfortunately, as the

information made its way up the food train, the direction the aircraft were

coming in from got lost and it got misinterpreted as being an expected fleet

of bombers coming in vs. the reality was a huge swarm of Japanese fighter

aircraft.

Exactly, so people start playing with different wavelengths,

different colors, realizing that you could see different things like

precipitation just by changing the frequency of the radar beam. It was a

fairly short leap to realize, Oh, wait! If we use sufficiently long

wavelengths, we can start to reflect light off of, well, planets, and accurately

measure how far away is Mercury, how far away is Venus simply by

sending off a pulse of radar and waiting the minutes and minutes and

minutes and minutes for that light to reflect its way back to Earth.. It allows boats and aircraft to see at night and through thick fog,