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Many of us follow the idea of "seeing is believing"
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But we all know that there are a lot of times
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where this isn't exactly true.
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One of the most mysterious of which
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could be key to understanding the universe around us
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Dark matter is defined as particles that don't
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absorb, reflect, or emit light
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They don't really interact with normal matter,
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and they can't be detected using electromagnetic radiation.
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Essentially, with current technology as it is,
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we have no way of really finding dark matter in space
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But if we can't detect dark matter...
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how do we know it's there?
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00:36.8
To make it easier to visualize, let's look at
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00:38.7
two bottles with coins in them
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00:40.5
One of these bottles is full of water,
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00:41.9
while the other has just air.
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You really can't tell the difference between
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00:46.4
the bottles just by looking at them. What you
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can see however is that the water makes the coins
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move differently than air
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00:53.1
Let's abstract this thinking into how dark matter was discovered.
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The first person to discover and coin the term
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"dark matter" was an astronomer named Fritz Zwicky.
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In the 1930s, he was observing the Coma galaxy cluster,
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and he used a method called the "virial theorem"
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to infer the gravitational mass of the cluster.
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His results led him to argue that there was simply not enough
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01:11.7
combined mass of visual matter in the cluster
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01:13.3
to hold it together gravitationally
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Zwicky didn't have enough evidence to prove the existence
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01:19.7
of dark matter, but more evidence of this mysterious substance
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has popped up over the years. Let's look at one more example.
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01:25.7
When you look at the image of a galaxy, you can see
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01:28.4
that there are more stars concentrated near the center
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of the galaxy rather than the edges.
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01:33.1
This leads astronomers to the logical conclusion that the
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gravity must be stronger near the center and weaker
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01:37.4
near the edges of the galaxy.
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01:39.1
This means that the stars near the edges of the
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galaxy have to orbit slower than the ones near the center.
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01:44.4
Otherwise, they'd break the force of gravity and
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move off into space
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01:49.3
While observing the Andromeda galaxy, astronomer Vera Rubin
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was testing out the new spectrometer of a colleague, Kent Ford Jr.
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The wavelengths measured using the spectrometer
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allowed them to calculate the speed of the stars in the galaxy.
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What they found, however, was very unexpected.
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All of the stars in the galaxy were orbiting at the same speed!
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But there simply wasn't enough visible mass in the galaxy
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to create gravity strong enough to keep those stars in orbit.
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Unless there was something else, in between the stars - Dark matter.
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But what is dark matter exactly?
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Because of its properties, we currently have no
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way to find out exactly what dark matter consists of.
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02:27.6
There have been many candidates - WIMPs, axions, bosons,
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02:30.3
and neutrinos being just a few, but with many of
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02:33.5
these particles being theoretical or some of the most elusive known to
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man, hopes have been constantly raised and dashed with no results.
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Rise of new technology brings rise of new information,
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02:43.1
and along with it comes ways of finding out how the universe
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around us came to be. Dark matter may have
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existed even before the Big Bang, which gives us insight
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not only into the Big Bang and how matter came into the
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arrangements that it's in today, but also about times
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even before the big bang and the known universe.
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And with that, I'll leave you to think about
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what else lurks in the dark.
