David Kordahl in The New Atlantis:
Some sixty years ago, Arno Penzias and Robert Wilson were scraping pigeon droppings from a large radio antenna at Bell Labs in New Jersey. They were radio engineers, and their project was straightforward. They wanted to see if they could eliminate the persistent background noise in radio signals, and they supposed that capturing the pigeons roosting in the horn and cleaning it might help. They realized that it didn’t.
Today, the radio noise they detected has been identified as the cosmic microwave background, a subject of intense scientific scrutiny. The pigeon traps have been displayed as relics by the Smithsonian’s National Air and Space Museum.