The Cosmic Microwave Background

The cosmoic wave background was initially blamed on pigeon poop in the detector. Scientists were looking for cosmic sources that could interfere with tele communications. They noticed pigeons were roosting in their system, so they gave it a thorough cleaning to remove anything the pigeons may have left within the detector. And it didn't work. In the end, after contacting a research group p at princeton and a talking to folks like peebles, they realized that what they were seeing matched theoretical predictions of a cold, long wave length background of light. The universe got cool enough for electrons and atomic nuclei to bond together, making our universe trans parent for the first time.