Really. You can actually see it if you tune a TV to a channel where no station is broadcasting...what you'll see a TV signal that was sent 13.7 billion years ago.
As we discussed in yesterday's post, heat is just atoms in motion, and the heat of the Big Bang smashed atoms together with such force that after the first flash, the lights went out, and the cosmic dark ages started.
But about 380,000 years later the Universe finally cooled enough for the initial flash of energy created during the Big Bang to be released. Just 400 million years later stars started to form.
Like an immense refrigerator, as the gas in Universe continued to expand the temperature continued to fall to what it is today, just above absolute zero at 3ºK (-454ºF). Energy at that temperature is emitted as microwaves, and we detect the cosmic microwave background radiation as 'snow' on TV.
The image below is a high resolution map of the cosmic microwave background radiation of the Universe created by the Wilkinson Microwave Anistropy Probe (WMAP). The data from this spacecraft confirmed the age of the Universe.