• 3 weeks ago
The Space Documentary
Transcript
00:00What if I told you that nearly a third of the universe is completely invisible, a force
00:09so vast and powerful that it holds galaxies together but remains unseen, untouchable and
00:15undetectable by any instrument we possess.
00:18It's called the Dark Matter.
00:27It's everywhere, silently shaping the cosmos, and yet, we know almost nothing about it.
00:32What is the mysterious substance?
00:34Why does it matter so much?
00:36Today, we will journey into the depths of space and uncover the hidden force that makes
00:40up 27% of the universe, an unsolved cosmic riddle that could change everything we think
00:46we know about reality.
00:48Dark matter is one of the most profound mysteries in astrophysics.
00:52It makes up a significant portion of the universe, yet it's invisible and doesn't interact with
00:56light or normal matter.
00:58Everything we can see, stars, planets, gas clouds, only accounts for a tiny fraction
01:03of the universe.
01:04The rest, a combination of dark matter and dark energy, the latter responsible for the
01:09accelerated expansion of the universe.
01:12But today, our focus is on dark matter, the hidden substance that holds galaxies together
01:17and plays a crucial role in the formation of cosmic structures.
01:20How do we even know that it's there, if we cannot see it?
01:24And more importantly, what is it?
01:28The story of the dark matter begins in the early 20th century, when Swiss astrophysicist
01:33Fritz Zwicky first noticed something strange.
01:36While studying the Coma Cluster, a collection of galaxies, he calculated that the galaxies
01:41were moving far too quickly to be held together by the visible matter within them.
01:45According to Newton's law of gravity, these galaxies should have flown apart.
01:50Zwicky suggested that there must be some form of missing mass that we cannot see, something
01:55exerting enough gravitational force to hold the galaxies in place.
01:59He named this invisible mass dark matter.
02:02For decades, Zwicky's idea was met with skepticism.
02:06Until the 1970s, when the American astronomer Vera Rubin made a groundbreaking discovery.
02:12While studying the rotation curves of spiral galaxies, she found that stars at the outer
02:16edges of galaxies were moving much faster than expected.
02:20According to the laws of physics, the outermost stars should be moving more slowly than those
02:25near the center.
02:26Instead, Rubin discovered that these stars were moving at nearly the speed as those in
02:31the center, again suggesting the presence of unseen mass.
02:35These observations, Zwicky's missing mass and Rubin's fast-moving stars, laid the foundation
02:40of the dark matter hypothesis.
02:43But what exactly is dark matter and why is it so hard to detect?
02:48Despite decades of study, dark matter remains elusive.
02:51It doesn't emit or absorb light, making it completely invisible to even the most advanced
02:56stethoscopes.
02:57In fact, the only reason we know dark matter exists is because of the gravitational effects
03:02it has on the universe.
03:03One of the most compelling pieces of evidence for dark matter is the rotation of galaxies.
03:08As Vera Rubin discovered, galaxies spin far faster than their visible matter should allow.
03:13If we only account for the matter we can see, stars, gas, and dust, the gravitational pull
03:19would be far too weak to hold these galaxies together.
03:22They should tear themselves apart, but they don't.
03:25Something else, something invisible, is providing the extra mass needed to keep galaxies intact.
03:31This missing mass is what we call now dark matter.
03:35Another strong piece of evidence comes from something called gravitational lensing.
03:39According to Einstein's theory of general relativity, massive objects like galaxies
03:44can bend the fabric of space-time, causing light to curve as it passes by.
03:48When we observe distant galaxies, we often see their light being bent around other massive
03:53objects.
03:54But here's the catch.
03:55The amount of bending we observe can't be explained by visible matter only, there must
04:00be additional mass.
04:02Dark matter causing the extra gravitational pull that bends the light even more.
04:07Lastly, the Cosmic Microwave Background Radiation.
04:10The faint afterglow of the Big Bang also offers clues about dark matter.
04:15The slight variation in this radiation revealed the large-scale structure of the universe
04:19and suggests that dark matter played a key role in shaping it.
04:23These fluctuations tell us that dark matter was present in the early universe, guiding
04:28the formation of galaxies and galaxy clusters.
04:32For all that we know about dark matter's effect, we still have no idea what it actually is.
04:38Scientists have proposed several hypotheses, but so far, no one has detected dark matter
04:42directly.
04:43One leading theory is that dark matter consists of weakly interacting massive particles, or
04:48WIMPs.
04:49These particles would have mass and interact through gravity, but would otherwise barely
04:54interact with normal matter at all.
04:56If WIMPs exist, they would explain why dark matter is so hard to detect, because they
05:01almost never collide with the particles we are made of.
05:04Another possibility is that dark matter could be made of axions, hypothetical particles
05:09much lighter than WIMPs.
05:11Axions are predicted to be able to convert into photons, particles of light, in the presence
05:15of magnetic field, which gives us a possible way to detect them.
05:19So far, however, axions remain a theoretical concept.
05:22There is even a more radical idea.
05:25What if dark matter isn't made of particles at all?
05:28Some scientists have suggested that our understanding of gravity itself may be incomplete.
05:33This theory, called Modified Newtonian Dynamics, or MOND, proposes that at large cosmic scales,
05:39gravity behaves differently than we expect, which could explain the strange movement of
05:43galaxies without the need of dark matter.
05:45However, most scientists believe that dark matter is more likely to exist than that our
05:50understanding of gravity is fundamentally wrong.
05:53Despite these theories, all attempts to detect dark matter particles directly have failed
05:58so far.
05:59Experiments deep underground, in space, and at particle accelerators like CERN have been
06:04searching for dark matter for years, but the elusive substance continues to evade capture.
06:11So why is the dark matter so important?
06:13Without it, the universe as we know it wouldn't exist.
06:16Dark matter provides the gravitational scaffolding that allows galaxies to form and grow.
06:21Without its gravitational influence, stars would be scattered across space, unable to
06:26come together to form galaxies, planets, or life.
06:30Dark matter also played a crucial role in the early universe.
06:33After the Big Bang, the universe was filled with hot plasma.
06:37As this plasma cooled, dark matter began to clump together under the force of gravity,
06:42creating the seeds from which galaxies would eventually form.
06:45Without dark matter, the universe would look very different, possibly too chaotic for galaxies,
06:50stars, and planets to form at all.
06:53Understanding dark matter could also unlock new physics.
06:56If we can identify what dark matter is made of, it could open the door to a whole new
07:00understanding of the universe.
07:02It could reveal new particles, new forces, and possibly even new dimensions.
07:07Solving the mystery of dark matter is one of the biggest challenges in modern physics,
07:11and it could change the way we think about everything, from the smallest particles to
07:16the structure of the universe itself.
07:20Despite the challenges, scientists are far from giving up.
07:23New technologies and experiments are being developed to search for dark matter.
07:27Some are looking for WIMPs, while others are testing alternative theories like Xeons.
07:32The Large Hadron Collider at CERN also being used to try to create dark matter particles
07:37in high-energy collisions.
07:39There are even ambitious space-based experiments like the James Webb Telescope, which could
07:43help us observe the effects of dark matter in even greater detail.
07:47In the coming decades, scientists hope to detect dark matter directly and finally solve
07:51the cosmic puzzle.
07:52But until then, dark matter remains one of the greatest mysteries of the universe.
07:58It is all around us, yet beyond our reach.
08:01We know it's there, but we don't know what it is.
08:03The search for dark matter is one of the most exciting and challenging endeavors in science.
08:08A journey into the unknown that could redefine everything we know about the cosmos.