In the summer of 1961 the upper stage of the rocket carrying the Transit 4A satellite blew up about two hours after launch. It was the first known human-made object to unintentionally explode in space, and it created hundreds of fragments of useless space junk. Some of these pieces were pulled into the atmosphere where they burned up but around 200 of them are still up and orbiting today.
At the time, people were not all that concerned about a few bits of metal floating around in the vastness of space. But like the ocean and other frontiers, space isn’t endless as it first appears.