In the 19th century, early radars were not exactly what we know today. These were more like... well, they were just a bunch of flashing lights in a room.
Imagine being a sailor on a ship, trying to navigate through stormy seas. You'd have a bunch of guys waving their arms and shouting "LEFT! RIGHT! LEFT! RIGHT!"
It wasn't until World War I that the first actual radar systems were developed. These used a big antenna to send out radio waves, and a screen to display where they bounced off stuff.
Here's a picture of what it looked like:
See how early radar systems paved the way for space exploration