Could we create dark matter? - Rolf Landua
-
0:07 - 0:1185% of the matter in our universe
is a mystery. -
0:11 - 0:15We don't know what it's made of,
which is why we call it dark matter. -
0:15 - 0:19But we know it's out there because we
can observe its gravitational attraction -
0:19 - 0:22on galaxies and other celestial objects.
-
0:22 - 0:25We've yet to directly observe dark matter,
-
0:25 - 0:28but scientists theorize that we may
actually be able to create it -
0:28 - 0:32in the most powerful particle collider
in the world. -
0:32 - 0:37That's the 27 kilometer-long
Large Hadron Collider, or LHC, -
0:37 - 0:39in Geneva, Switzerland.
-
0:39 - 0:40So how would that work?
-
0:40 - 0:44In the LHC, two proton beams
move in opposite directions -
0:44 - 0:47and are accelerated
to near the speed of light. -
0:47 - 0:52At four collision points, the beams cross
and protons smash into each other. -
0:52 - 0:57Protons are made of much smaller
components called quarks and gluons -
0:57 - 1:01In most ordinary collisions, the two
protons pass through each other -
1:01 - 1:04without any significant outcome.
-
1:04 - 1:06However, in about
one in a million collisions, -
1:06 - 1:09two components hit each other
so violently, -
1:09 - 1:12that most of the collision energy
is set free -
1:12 - 1:14producing thousands of new particles.
-
1:14 - 1:17It's only in these collisions that very
massive particles, -
1:17 - 1:21like the theorized dark matter,
can be produced. -
1:21 - 1:24The collision points
are surrounded by detectors -
1:24 - 1:27containing about 100 million sensors.
-
1:27 - 1:29Like huge three-dimensional cameras,
-
1:29 - 1:32they gather information
on those new particles, -
1:32 - 1:33including their trajectory,
-
1:33 - 1:34electrical charge,
-
1:34 - 1:36and energy.
-
1:36 - 1:40Once processed, the computers can depict
a collision as an image. -
1:40 - 1:43Each line is the path
of a different particle, -
1:43 - 1:46and different types of particles
are color-coded. -
1:46 - 1:49Data from the detectors
allows scientists to determine -
1:49 - 1:51what each of these particles is,
-
1:51 - 1:54things like photons and electrons.
-
1:54 - 1:58Now, the detectors take snapshots of about
a billion of these collisions per second -
1:58 - 2:02to find signs of extremely rare
massive particles. -
2:02 - 2:04To add to the difficulty,
-
2:04 - 2:07the particles we're looking for
may be unstable -
2:07 - 2:12and decay into more familiar particles
before reaching the sensors. -
2:12 - 2:14Take, for example, the Higgs boson,
-
2:14 - 2:18a long-theorized particle that wasn't
observed until 2012. -
2:18 - 2:25The odds of a given collision producing
a Higgs boson are about one in 10 billion, -
2:25 - 2:28and it only lasts for
a tiny fraction of a second -
2:28 - 2:30before decaying.
-
2:30 - 2:34But scientists developed theoretical
models to tell them what to look for. -
2:34 - 2:38For the Higgs, they thought it would
sometimes decay into two photons. -
2:38 - 2:42So they first examined only
the high-energy events -
2:42 - 2:44that included two photons.
-
2:44 - 2:45But there's a problem here.
-
2:45 - 2:48There are innumerable
particle interactions -
2:48 - 2:50that can produce two random photons.
-
2:50 - 2:54So how do you separate out the Higgs
from everything else? -
2:54 - 2:56The answer is mass.
-
2:56 - 3:01The information gathered by the detectors
allows the scientists to go a step back -
3:01 - 3:06and determine the mass of whatever it was
that produced two photons. -
3:06 - 3:08They put that mass value into a graph
-
3:08 - 3:12and then repeat the process
for all events with two photons. -
3:12 - 3:16The vast majority of these events
are just random photon observations, -
3:16 - 3:20what scientists call background events.
-
3:20 - 3:24But when a Higgs boson is produced
and decays into two photons, -
3:24 - 3:27the mass always comes out to be the same.
-
3:27 - 3:30Therefore, the tell-tale sign
of the Higgs boson -
3:30 - 3:34would be a little bump sitting on top
of the background. -
3:34 - 3:37It takes billions of observations
before a bump like this can appear, -
3:37 - 3:40and it's only considered
a meaningful result -
3:40 - 3:44if that bump becomes significantly
higher than the background. -
3:44 - 3:46In the case of the Higgs boson,
-
3:46 - 3:50the scientists at the LHC announced their
groundbreaking result -
3:50 - 3:53when there was only
a one in 3 million chance -
3:53 - 3:57this bump could have
appeared by a statistical fluke. -
3:57 - 3:59So back to the dark matter.
-
3:59 - 4:02If the LHC's proton beams have enough
energy to produce it, -
4:02 - 4:07that's probably an even rarer occurrence
than the Higgs boson. -
4:07 - 4:11So it takes quadrillions of collisions
combined with theoretical models -
4:11 - 4:13to even start to look.
-
4:13 - 4:16That's what the LHC is currently doing.
-
4:16 - 4:18By generating a mountain of data,
-
4:18 - 4:21we're hoping to find more tiny bumps
in graphs -
4:21 - 4:26that will provide evidence for
yet unknown particles, like dark matter. -
4:26 - 4:28Or maybe what we'll
find won't be dark matter, -
4:28 - 4:29but something else
-
4:29 - 4:34that would reshape our understanding
of how the universe works entirely. -
4:34 - 4:36That's part of the fun at this point.
-
4:36 - 4:38We have no idea what we're
going to find.
- Title:
- Could we create dark matter? - Rolf Landua
- Description:
-
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View full lesson: https://ed.ted.com/lessons/could-we-create-dark-matter-rolf-landua
Eighty-five percent of the matter in our universe is dark matter. We don’t know what dark matter is made of, and we’ve yet to directly observe it, but scientists theorize that we may actually be able to create it in the Large Hadron Collider, the most powerful particle collider in the world. So how would that work? CERN scientist Rolf Landua explains how to discover a new particle.
Lesson by Rolf Landua, animation by Lazy Chief.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:49
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