>>MORDECAI-MARK MAC LOW: My name is Mordecai-Mark Mac Low
and my position is Curator of Astrophysics.
So, Big Bang theory suggests that the universe was once hotter than the surface of the sun.
Well, if there's one thing we know about the surface of the sun, it's that it emits light.
What Big Bang theory is claiming is that the entire universe was once that bright.
If so, where is all that light?
Well, it turns out that it's right here, pervading the universe.
But because the universe was expanding, the light got stretched to longer and longer and
longer wavelengths.
And although it was emitted - rather coincidentally - as visible light, it got stretched from
visible, yellow light to infrared, to microwaves, radio waves.
And those radio waves pervading the universe can be detected with a microwave antenna.
Heck, they can be detected with a TV antenna.
An old-style, on-the-air TV - a few percent of the noise that you get when you tune to
an empty channel was from the early universe.
Those radio waves are what we call the Cosmic Microwave Background.
So, the background of microwaves that pervades the universe because they were emitted during
the early expansion of the universe and have been traveling and getting stretched out ever since.
The idea that there ought to be background radiation was actually first understood in
the 1940s with the idea that there must be a hot, dense beginning to the universe.
But sad to say, that prediction was more or less ignored for many years.
And it wasn't until the '60s that Peebles and Dicke at Princeton University said, "We
ought to try and check this prediction."
And set out to do so.
Well, by the '60s, technology had advanced, the Space Race had started.
People were building microwave antennae not to look for some crazy idea of some physicist
sitting in a lab somewhere, but to follow communications satellites.
And a couple of electrical engineers by the name of Penzias and Wilson got a hold of one
of these antennae that had been used to follow the Echo Communication Satellite...
...and thought to themselves, "We could do astronomy with this!"
And so, they started using it to try to detect emission from gas in the Milky Way galaxy.
Now, they were rather good engineers.
And so, the first thing they did was point their antenna at an empty patch of sky so
they would be able to measure its noise level.
And - darn it all - there's something wrong in the system.
They had too much noise.
That is, their antenna was detecting a signal, which they interpreted as noise, that was
more than they expected.
So, they started debugging their circuit and checking all the connections.
And at one point they even suspected pigeon poop in the antenna of emitting enough microwaves
to throw off their sensitive detectors.
So, they chased all the pigeons out and cleaned it off.
And they still had this noise when they pointed it at an empty patch of sky.
They finally convinced themselves that they had detected cosmic radiation.
So, they went to a conference and said, "Uh, guys, there seems to be some sort of cosmic
radiation pervading every direction we look."
And some physicist said, "That's interesting."
"You ought to go talk to Peebles and Dicke down the road at Princeton."
So, they did. And Dicke turns to his lab and says, "Boys, we've been scooped."
Because the very thing that they were looking for - the echo of the Big Bang, the baby picture
of the universe - had been discovered by these communications engineers 20 miles down the
road.
Peebles and Dicke and Penzias and Wilson published papers back to back.
A theoretical paper saying, "This is what we predict," and the observational paper saying,
"This is what we saw."
But only the observers got the Nobel Prize.
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