00:00Does the universe ring like a crystal glass? Maybe.
00:04But it doesn't mean that it literally rings and we just don't hear it.
00:07It just vibrates.
00:11Many of you know that the universe started with the Big Bang around 13.8 billion years ago.
00:17I wasn't around then, but we can assume.
00:19The whole enchilada was born from a super-concentrated, hot, and dense tiny dot that contained everything.
00:26When it couldn't bear its pressure anymore, it made a huge blast and spewed around all the time, space, matter, and antimatter like a pokeball.
00:36After being born, the universe moved at a breakneck speed.
00:40Imagine standing in the middle of nowhere, you blink, and suddenly you're surrounded by the universe.
00:45That's what it would feel like.
00:47It started growing and growing, and eventually, its speed got slowed down a bit by gravity.
00:52Gravity started pulling all the matter together, slowly helping new things like stars and galaxies to form.
01:01Okay, makes sense so far.
01:03The Big Bang gave the universe a big push accelerating it.
01:06Logically, everything should eventually slow down and start moving at a constant speed, or even stop, right?
01:13Well, nope.
01:14In the late 90s, astronomers discovered something weird.
01:17They looked at some supernova around us, and for some reason, these supernovas were super far away, much farther than they were supposed to be.
01:26In other words, the expansion of the universe is not only continuing after all these years, but it's even accelerating.
01:33After years of study, they discovered the concept of dark energy, a mysterious force that makes up about 68% of the universe's total energy.
01:42This energy pushes it to expand even faster over time.
01:47And now, scientists have proposed a new discovery.
01:50Perhaps the universe's movements are a bit, well, wobbly.
01:57It seems like the universe's expansion hasn't been smooth and stable over the years.
02:02Instead, it has undergone periods of speeding up and slowing down multiple times.
02:07Astronomers counted about seven cycles of this acceleration and deceleration over the history of our universe.
02:15This can be compared to the oscillation of a crystal glass.
02:19When you strike a crystal glass, it vibrates, oscillating at its natural frequency.
02:24It goes through fluctuations in which the frequency rises and falls.
02:28Over time, it calms down and fades away.
02:31Well, something like this is happening to our universe.
02:34You can imagine its speed also fluctuating like that, rising and falling, first super rapidly and then more calmly.
02:43As if it's not just different waves traveling through it, but our entire world is like one huge ringing wave.
02:51The discovery was actually made by accident.
02:54Astronomers were working on dark matter modeling.
02:57They plotted a new graph called the Hubble diagram,
03:00which shows how big the universe got over the years, measured in supernovas.
03:05Supernovas are like some lighthouses of our world, helping us mark things on a map.
03:10That's when they found these oscillations.
03:13But we still need to check all the data to make sure that this discovery is indeed true.
03:18Dark energy and dark matter play this weird game with the universe,
03:22where one is constantly trying to pull everything together,
03:25while the other one wants everything to expand.
03:28So far, dark energy vastly outweighs dark matter,
03:32whose weight makes up only 27% of the universe.
03:35Now, both of them are invisible to us.
03:38And not just invisible to our eyes, like infrared.
03:41It's that we literally can't detect them in any way.
03:44We can only assume that they exist based on how they influence gravity,
03:48changing entire galaxies and all the large-scale structures of the universe.
03:52We basically made them up, because it was the only way to explain how our world works.
03:58Dark energy is uniformly distributed across space and time.
04:02And we're still not sure what exactly it is.
04:05Some theories say that it could be a property of space itself,
04:09quantum fluctuations, or even a new type of field or particle.
04:13But all we have for now is an invisible energy that pushes the universe to move very fast.
04:19If one day we learn more about it, this will help us predict the entire fate of our world.
04:25Depending on how exactly dark energy works,
04:28the universe may continue expanding and growing indefinitely.
04:32Or maybe one day, it will experience the big rip,
04:35where all matter will be completely torn apart.
04:38Okay, here's to hoping we're not all around for that.
04:42Meanwhile, dark matter, also invisible and yet to be proved,
04:46works the opposite way.
04:47It's not energy that accelerates things.
04:50Instead, it's more like a glue that tries to hold everything together.
04:54It's a type of matter we can't detect because it doesn't emit, absorb, or reflect light.
05:00We don't even know what particles make up this thing.
05:02We still can't catch them.
05:04At first, we thought it might be made up of regular heavy particles,
05:08like the one that makes up our world.
05:10But after years of research, they haven't found even a single one.
05:14So now they think, maybe it's actually made up of ultralight particles,
05:18millions of times lighter than anything we know.
05:21And because of that, we can't even notice them properly.
05:25So now, astronomers try to detect not the particles themselves,
05:29but waves that they could leave as they move through space.
05:32But we believe that it exists,
05:34because if it didn't, our galaxies wouldn't hold together.
05:38Dark matter helps them form, grow, and rotate.
05:42So, about 85% of our world is made of something unknown.
05:46All of this is incredibly mysterious and needs a lot of research.
05:51But that's what we know now.
05:53Maybe in the future, we'll discover something
05:55that will completely change our perception of the universe.
05:59That's what happened to Albert Einstein.
06:01In the early 20th century,
06:03most scientists, including Einstein,
06:04believed that the universe doesn't actually move.
06:08They thought it was static,
06:09neither expanding nor contracting.
06:11That's because, to us, it feels like it doesn't really move.
06:15Back then, scientists didn't have powerful computers or telescopes
06:19that could detect all the little changes
06:21in the positions of stars and supernovas.
06:24When Einstein developed his famous
06:26General Theory of Relativity in 1915,
06:29his equations actually suggested
06:31that the universe should either be expanding or contracting.
06:35This didn't really make sense to him.
06:37To fix this calculation flaw,
06:39he decided to introduce a new term,
06:42the cosmological constant.
06:44It was like a repulsive force
06:45that counteracted the attractive force of gravity.
06:49Essentially, it meant that,
06:50while gravity tries to push everything together,
06:53some force or energy helps to balance this out
06:56by pushing everything apart.
06:58Sounds familiar?
06:58Then, in the 1920s, astronomers Edwin Hubble and Georges Lemaître
07:04found out that the universe isn't static.
07:07It actually expands.
07:08They noticed a slight reddish tint from the distant galaxies.
07:12And this tiny hint meant that other galaxies were moving away from us.
07:16After that, Einstein scratched out the cosmological constant.
07:21Interesting how he was later ashamed of this assumption,
07:24calling it his greatest blunder.
07:25He didn't even know that he was 100 years ahead of his time,
07:29accidentally discovering dark energy.
07:32Now, the cosmological constant is back again,
07:35just in a new form.
07:37Something similar happened with dark matter.
07:40Scientists have already started noticing
07:42that something doesn't add up back in the early 20th century.
07:46They saw that galaxy clusters didn't have enough visible mass
07:49to hold them together,
07:51which means there must be some unseen mass
07:54that helps to make up for it.
07:56And that's when it got its name, the dark matter.
07:59This stayed unresolved and unproven for many years.
08:02And then, it was finally discovered by Vera Rubin
08:05when she was observing galaxies and their movement.
08:08She realized that outward parts of galaxies
08:11move almost as fast as their central parts.
08:14This doesn't really make sense.
08:16The outer part should be a bit slower.
08:18This became the first official proof of dark matter
08:21which boosted its research.
08:23There are still many things left to be discovered.
08:26But maybe one day,
08:28we'll understand what is this invisible part of our universe
08:31that makes it ring.
08:33That's it for today.
08:34So hey, if you pacified your curiosity,
08:36then give the video a like and share it with your friends.
08:39Or if you want more,
08:40just click on these videos and stay on the bright side.
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