>>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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