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What is the oldest
photo of the universe?

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The oldest pictures
we have today

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are of our universe's
teen years,

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except for one photo,
one baby picture

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of the universe, the cosmic
microwave background.

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Today, the universe is more
than 13.7 billion years old.

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But the cosmic
microwave background

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is a map of the universe when
it was just 378,000 years old.

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The image is similar to a
temperature map of the United

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States.

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But instead of showing a
wide range of temperatures,

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the cosmic microwave
background shows

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tiny almost unperceivable
temperature differences

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in the newborn universe.

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Scientists Arno Penzias and
Robert Wilson unexpectedly

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discovered the cosmic microwave
background in the 1960s

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while using a large
microwave detector

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to study the Milky Way.

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They were surprised to find
a static or fuzz coming

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from all directions
of the sky and that

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all of the static radiated
with the same temperature, 2.73

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Kelvin above absolute zero.

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The signal was so unexpected
that the two scientists

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initially thought
the noise was coming

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from the antenna or some
other earthly source.

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But one by one,
they methodically

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ruled out all other
possibilities,

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even cleaning out
pigeon droppings

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from inside the
antenna to make sure

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that wasn't interfering, and
found that the signal was real.

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It was coming from the cosmos.

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You may have even seen some
of the static yourself.

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About 2% of the fuzz on
an old television set

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comes from the cosmic
microwave background.

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In the 1980s, a NASA
satellite called

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COBE mapped the cosmic
microwave background

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and revealed that
it was not exactly

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the same temperature
in every direction.

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COBE uncovered islands of
relative warmth and cold.

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But the temperature
differences COBE observed

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were incredibly small.

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The temperature variations
from place to place

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were less than one
ten-thousandth of a degree.

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If you wanted to change the
temperature in your living room

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by that amount, you would need
to run your heater for less

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than a hundredth of a second.

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Later, NASA's WMAP and the
European Space Agency's Planck

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spacecraft gave us an even
better, more detailed map

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of the cosmic
microwave background.

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Amazingly, these little
temperature fluctuations

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grew into all the structures in
the universe, galaxies, stars,

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and planets.

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Over time, the
slightly hotter areas

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pulled in more
and more material,

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and the slightly colder areas
grew colder and emptier.

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Today, hot, dense
stars in galaxies

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are surrounded by cold,
mostly empty space.

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Maps of the cosmic
microwave background

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tell us about the early
history of the universe

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when it was hotter and denser.

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