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Have you ever looked up in the night sky and just,

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I don't know if it felt that like almost a sense of vertigo,

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like you're staring into this massive cosmic ocean

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and we're just, you know, these tiny little creatures

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just starting to dip our toes in.

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Yeah, it's humbling, isn't it?

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You realize just how much is out there that we,

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we don't know that we're just starting to grasp.

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Exactly.

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And that's what we're diving into today,

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a mystery that's, well, kind of shaking the foundations

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of what we thought we knew about the universe.

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It's all about dark matter.

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Welcome to Cosmos in a Pod, the Space and Astronomy series.

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Please like, comment, share, and subscribe.

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So picture this, it's 1933

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and we've got this astronomer, Fritz Zwicky.

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He's looking at this giant cluster of galaxies

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called the Coma Cluster.

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Yeah, Zwicky, he was a real pioneer.

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I mean, this is way before we had the kind of telescopes

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and computing power we have today.

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Right, so he's basically doing this cosmic accounting,

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trying to figure out how much stuff is in this cluster

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and how fast everything's moving.

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And that's where things get weird.

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What'd he find?

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Well, the galaxies, they were moving way too fast.

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Like based on the amount of matter he could see,

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the stars, the whole cluster should have just flown apart.

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Like imagine a car going 200 miles per hour on a racetrack,

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but somehow staying perfectly on the track.

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It didn't make sense.

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So what was holding it all together?

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Like some kind of cosmic speed limit.

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Well, Zwicky, he proposed this radical idea.

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He said there must be this invisible matter out there,

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this stuff that we can't see but that has gravity.

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He called it dark matter.

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Dark matter.

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So basically he's saying that most of the universe

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is made up of something we can't even see.

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Yeah, and that, my friend, was the beginning

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of one of the biggest head scratchers in modern cosmology.

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It's crazy that, I mean, this is almost a century ago,

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and we're still trying to figure out

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what this dark matter stuff actually is.

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Absolutely.

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And it wasn't just Zwicky.

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Decades later in the 1970s, we have Vera Rubin.

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She was studying how galaxies rotate.

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Yeah, yeah, I remember reading about her work.

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It's like how stars orbit within a galaxy, right?

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Exactly.

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So think about it like a merry-go-round.

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You'd expect the horses on the outer edge

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to be moving slower than the ones near the center, right?

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Like same principle with planets orbiting the sun.

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The farther out you go, the slower the orbital speed.

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Right, makes sense.

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But what Rubin observed was that stars

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on the outer edges of galaxies

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were moving just as fast as the stars closer to the center.

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These flat rotation curves, they were a major puzzle.

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So it's like everyone on the merry-go-round,

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no matter how far from the center,

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is somehow moving at the same speed.

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That doesn't sound right.

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It doesn't.

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And that's where the dark matter idea

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really starts to gain momentum.

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It's like this invisible glue, this extra gravity

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that's holding those outer stars in place.

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It's like the galaxy is embedded

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in this giant halo of dark matter.

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That's it.

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That's the prevailing theory,

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known as the Lambda Cold Dark Matter Model,

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or CDM for short.

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And it's not just about galaxies.

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It also helps explain things like gravitational lensing.

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Wait, remind me of gravitational lensing.

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That's how light bends around massive objects, right?

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Exactly.

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Imagine a bowling ball on a trampoline,

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and you roll a marble past it.

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The marble's path will curve slightly

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because the bowling ball creates a dip in the trampoline.

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Same thing happens in space.

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Massive objects like galaxies, they warp spacetime,

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and that causes light to bend around them.

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Okay, I'm starting to see how it all connects.

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So if we observe this bending, this lensing,

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then that tells us there's gotta be something

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really massive there, even if we can't see it.

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Right.

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And the amount of lensing we observe

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lines up pretty well with what we'd expect

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if there's a lot of dark matter out there.

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So it seems like a pretty solid case for dark matter, right?

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Yeah, it does.

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But you said earlier that it's still a mystery.

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So what's the catch?

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The catch is, despite all this indirect evidence,

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all these signs pointing to dark matter,

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we've never actually directly detected it.

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I mean, we've built these incredibly sensitive detectors

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buried deep underground,

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hoping to catch these dark matter particles,

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but so far, nothing.

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So we have all these clues,

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but the culprit remains elusive.

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Exactly.

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And that's what has led some scientists to wonder

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if maybe, just maybe, there's something else going on.

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Like maybe our understanding of gravity itself

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needs some tweaking.

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Whoa.

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Okay, so are you saying there might be

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an alternative explanation for all this?

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Like something besides dark matter?

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There might be.

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And that's where things get even more interesting.

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All right, I'm hooked.

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Lay it on me.

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Well, hold on tight, because next time,

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we're diving into the realm of modified Newtonian dynamics,

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or MOND, a theory that dares to rewrite

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the rules of gravity itself.

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It's gonna be a wild ride.

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MOND, okay, now I'm really intrigued.

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I can't wait to hear more about that.

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Stay tuned.

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All right, so where were we?

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We were teetering on the edge of like a cosmic cliffhanger.

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We've got all this evidence pointing to dark matter,

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but we've never actually seen the stuff.

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Right, it's like we're trying to solve a crime,

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but the main suspect is a ghost.

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A cosmic ghost.

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And now you're saying there might be another suspect.

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There might be.

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And this one's a real game changer.

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It's called MOND, or modified Newtonian dynamics.

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And it's basically saying that,

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well, maybe Newton got gravity slightly wrong.

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Wait, Newton?

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Like Sir Isaac Newton?

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The Apple guy.

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The one and only.

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His laws of gravity, they've worked perfectly fine

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here on Earth, and even for predicting the motions

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of planets in our solar system.

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But when you get to these really, really vast distances,

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like the outskirts of galaxies,

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MOND is saying that maybe gravity doesn't behave

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quite the way we thought it did.

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So instead of invoking this invisible dark matter,

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MOND is saying that gravity itself

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changes its tune at these massive scales.

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Exactly, it's like imagine gravity has this secret setting

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that kicks in when things get really, really spread out.

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And the crazy thing is, it actually explains

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those flat galaxy rotation curves we talked about.

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Remember, the stars on the outer edges

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moving way faster than they should.

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MOND can account for that.

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So hold on, if MOND explains those observations,

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does that mean like, case closed, no need for dark matter?

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Ugh, I wish it were that simple.

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MOND, while it's a very elegant theory,

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it has its own set of issues.

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Okay, here comes the but, what kind of issues?

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Well, for starters, it has trouble explaining

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the behavior of galaxy clusters.

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Those massive groups of hundreds or even thousands

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of galaxies all bound together by gravity.

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Yeah, you mentioned those earlier.

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So MOND can't explain how those clusters stay together.

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Not really, according to MOND, those clusters,

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they should be flying apart.

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The modified gravity it proposes just isn't strong enough

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at those scales to keep everything bound together.

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Okay, so are you saying that even if MOND works

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for individual galaxies, it kind of falls apart

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when we look at larger structures?

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That's one way to look at it.

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And that might be where dark matter

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comes back into the picture.

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It could be that we need both.

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MOND to explain the behavior of individual galaxies

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and dark matter to explain those larger structures

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like galaxy clusters.

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Like are you saying, like a hybrid theory,

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MOND and dark matter working together?

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It's a possibility.

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Some physicists are exploring those kinds of models,

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trying to bridge the gap between these two seemingly

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contradictory ideas.

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It's pretty wild stuff.

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Okay, my head is spinning.

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So we've got dark matter, MOND,

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and now maybe some kind of cosmic team up between the two.

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Is that what you're saying?

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It's one of the possibilities, yeah.

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And that's what makes this whole debate so exciting.

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It's like we're constantly pushing the boundaries

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of what we know, trying to fit these pieces

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of the cosmic puzzle together.

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And speaking of pushing boundaries,

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you mentioned some other even more exotic ideas earlier,

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something about black holes and neutrinos.

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Yes, if we're going down the rabbit hole,

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we might as well explore all the tunnels, right?

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Yes.

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There are some truly mind bending ideas out there

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about what might be causing these cosmic discrepancies.

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Okay, I'm game.

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Hit me with it.

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What other wild ideas are cosmologists exploring?

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Well, one that's gained some traction

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is the idea of primordial black holes.

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These are black holes that theoretically would have formed

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in the very, very early universe,

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like fractions of a second after the Big Bang.

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Primordial black holes.

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That sounds like something out of like a sci-fi movie.

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How could something so old and potentially so small

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have such a big impact on the universe today?

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That's the mind blowing part.

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See, these primordial black holes,

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they could have a huge range of masses.

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Some might be tiny, but others could be super massive.

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And if they formed in those extreme conditions

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of the early universe,

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there could be tons of them out there,

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lurking in the shadows.

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And their combined gravity could be influencing

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the movements of galaxies

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and those galaxy clusters we talked about.

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So it's like a cosmic treasure hunt,

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searching for these ancient relics

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that could hold the key to understanding dark matter.

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But wait, if they're black holes,

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how could we ever even find them?

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It's a challenge, no doubt.

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But astronomers are looking for subtle clues,

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like gravitational lensing events.

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Remember that bending of light we talked about?

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Right, so we wouldn't actually be seeing

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in the black holes themselves,

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but rather how their gravity is distorting the light

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from other stars.

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Exactly.

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It's like trying to spot a tiny pebble in a pond

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by the ripples it makes.

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And these observations can give us clues

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about the mass and distribution

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of these hypothetical primordial black holes.

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Wow, that is so cool.

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It's amazing how scientists are using these indirect methods

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to like piece together this puzzle.

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It's like they're detectives of the cosmos.

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That's a great way to put it.

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But primordial black holes,

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they're not the only exotic candidate on the list.

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Okay, lay it on me.

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What else is out there in this cosmic zoo of ideas?

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Another candidate that has captured

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the imagination of physicists is the sterile neutrino.

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Sterile neutrino, okay.

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Now that sounds even more mysterious

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than a primordial black hole.

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What even is that?

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Well, you see, regular neutrinos,

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they're already these ghostly particles

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barely interacting with matter.

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But sterile neutrinos, they're, well,

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they're hypothetical particles

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that interact even less with regular matter.

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They're like the ultimate cosmic ninjas.

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So they're like just slipping through the fabric

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of reality unnoticed.

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Pretty much.

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And some physicists think that these stealthy particles,

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they could actually be a form of dark matter.

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But how could something that interacts so weakly

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with everything else have such a big

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gravitational effect on the universe?

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That's the million dollar question.

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It all boils down to their abundance.

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Even though individual sterile neutrinos

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would rarely interact with anything,

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if there are enough of them out there,

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their combined gravity could be enough

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to influence the formation and evolution

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of galaxies and galaxy clusters.

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So it's like the butterfly effect on a cosmic scale,

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a tiny, almost undetectable particle

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multiplied by trillions upon trillions

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shaping the very structure of the universe.

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Exactly.

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And just like with primordial black holes,

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scientists are looking for ways

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to detect these sterile neutrinos,

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like their potential influence

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on the cosmic microwave background radiation.

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The afterglow of the Big Bang, right?

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So we're talking about looking for these faint whispers

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from the dawn of time to solve this modern day mystery.

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Precisely.

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And it all highlights just how interconnected everything is,

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how these events from billions of years ago

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are still shaping the universe we see today.

315
00:11:22,600 --> 00:11:23,560
So let me get this straight.

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We've got dark matter, M-O-N-D, primordial black holes,

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sterile neutrinos.

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It's like the cosmic buffet of possibilities.

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Yeah.

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But with so many options on the table,

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how do we even begin to narrow down the search?

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Well, that's where the real fun begins.

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Because in our next installment,

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we're going to dive into the cutting edge research

325
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and the incredible new technologies that

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are helping us refine our theories

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and potentially unlock the secrets

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of dark matter and gravity.

329
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All right.

330
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So we've gone deep down the rabbit hole, dark matter,

331
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M-O-N-D, primordial black holes, sterile neutrinos.

332
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It's like the universe is throwing

333
00:12:00,640 --> 00:12:02,240
this massive cosmic party, and we're just

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trying to figure out the guest list.

335
00:12:03,320 --> 00:12:05,040
And the guest list is pretty wild.

336
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But the good news is we've got some pretty amazing tools

337
00:12:07,800 --> 00:12:09,040
to help us sort it all out.

338
00:12:09,040 --> 00:12:09,540
OK, yeah.

339
00:12:09,540 --> 00:12:13,080
You were about to tell us about the cutting edge of cosmology.

340
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What kind of high-tech gadgets are we talking about?

341
00:12:15,600 --> 00:12:17,960
Well, first up, we've got to talk about the James Webb

342
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Space Telescope.

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I mean, this thing is a game changer.

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It's like having a time machine, allowing us to peek back

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billions of years to see the very first galaxies forming.

346
00:12:28,320 --> 00:12:32,080
Yeah, those images it's sending back are just mind-blowing.

347
00:12:32,080 --> 00:12:35,120
But how does looking that far back

348
00:12:35,120 --> 00:12:37,360
help us understand dark matter?

349
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Because by studying those early galaxies,

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we can see how the universe evolved,

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how those structures, those galaxies and clusters

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first came together.

353
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And that gives us clues about the role

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dark matter might have played in all of that.

355
00:12:50,400 --> 00:12:53,000
So it's like we're looking for the fingerprints of dark matter

356
00:12:53,000 --> 00:12:55,600
in the earliest chapters of the universe's story.

357
00:12:55,600 --> 00:12:56,240
Exactly.

358
00:12:56,240 --> 00:12:58,120
And get this, the James Webb is already

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giving us some surprises.

360
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Some of those early galaxies, they

361
00:13:00,920 --> 00:13:03,080
seem to be a lot more massive and a lot more mature

362
00:13:03,080 --> 00:13:06,040
than we would have expected based on our current models.

363
00:13:06,040 --> 00:13:08,160
So are those observations, are they

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00:13:08,160 --> 00:13:10,440
contradicting the dark matter idea?

365
00:13:10,440 --> 00:13:14,000
Or maybe we just need to tweak our understanding

366
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of how galaxies form?

367
00:13:15,200 --> 00:13:16,880
That's the big question.

368
00:13:16,880 --> 00:13:18,680
These early galaxies, they seem to be

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forming stars way faster than the CDM model predicts,

370
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the one that relies heavily on dark matter.

371
00:13:26,240 --> 00:13:30,040
So maybe MOND, maybe with its modified gravity,

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maybe can explain those early stages of galaxy formation

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better.

374
00:13:33,720 --> 00:13:34,660
It's a possibility.

375
00:13:34,660 --> 00:13:37,560
The James Webb, it's really shaking things up,

376
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making us re-examine our assumptions.

377
00:13:39,400 --> 00:13:43,080
Wow, it's like the universe is constantly challenging us,

378
00:13:43,080 --> 00:13:45,000
daring us to come up with better explanations.

379
00:13:45,000 --> 00:13:46,240
Exactly.

380
00:13:46,240 --> 00:13:49,640
But the James Webb, it's not the only exciting new tool we have.

381
00:13:49,640 --> 00:13:53,240
We've also got the Vera Rubin Observatory coming online soon.

382
00:13:53,240 --> 00:13:55,560
This thing is going to be a dark matter hunting machine.

383
00:13:55,560 --> 00:13:57,080
The Vera Rubin Observatory.

384
00:13:57,080 --> 00:13:58,240
OK, tell me more about that.

385
00:13:58,240 --> 00:13:59,760
Imagine a camera, right?

386
00:13:59,760 --> 00:14:01,560
But a camera so powerful that it can

387
00:14:01,560 --> 00:14:05,520
capture images of billions of galaxies in incredible detail.

388
00:14:05,520 --> 00:14:07,640
That's basically what the Vera Rubin Observatory is.

389
00:14:07,640 --> 00:14:08,880
Billions, wow.

390
00:14:08,880 --> 00:14:10,880
So it's like a cosmic census.

391
00:14:10,880 --> 00:14:12,120
That's a great way to put it.

392
00:14:12,120 --> 00:14:14,200
It's going to scan the entire southern sky,

393
00:14:14,200 --> 00:14:17,000
creating this massive map of the universe, something

394
00:14:17,000 --> 00:14:18,720
we've never had before.

395
00:14:18,720 --> 00:14:21,160
OK, but how does mapping galaxies

396
00:14:21,160 --> 00:14:23,000
help us with dark matter?

397
00:14:23,000 --> 00:14:25,960
Well, remember gravitational lensing, the Vera Rubin

398
00:14:25,960 --> 00:14:27,160
Observatory.

399
00:14:27,160 --> 00:14:28,760
It's going to be so sensitive that it

400
00:14:28,760 --> 00:14:31,440
can detect these tiny distortions

401
00:14:31,440 --> 00:14:34,760
in the shapes of galaxies caused by, you guessed it,

402
00:14:34,760 --> 00:14:36,320
the gravity of dark matter.

403
00:14:36,320 --> 00:14:38,360
So it's like using the universe itself

404
00:14:38,360 --> 00:14:41,520
as a giant magnifying glass to see the invisible.

405
00:14:41,520 --> 00:14:42,400
That's it.

406
00:14:42,400 --> 00:14:44,080
And by studying those distortions,

407
00:14:44,080 --> 00:14:45,840
those lensing effects, we can actually

408
00:14:45,840 --> 00:14:49,120
create a 3D map of where dark matter is

409
00:14:49,120 --> 00:14:50,800
concentrated in the universe.

410
00:14:50,800 --> 00:14:54,080
It's like we're tracing the skeleton of the cosmos,

411
00:14:54,080 --> 00:14:56,480
revealing the hidden structure that's

412
00:14:56,480 --> 00:14:57,680
holding everything together.

413
00:14:57,680 --> 00:15:00,360
And that's going to give us so much more data, so many more

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00:15:00,360 --> 00:15:01,720
pieces to this cosmic puzzle.

415
00:15:01,720 --> 00:15:05,760
It's amazing how scientists are finding these really clever ways

416
00:15:05,760 --> 00:15:07,840
to study something that we can't even see directly.

417
00:15:07,840 --> 00:15:10,080
Yeah, it's a testament to human ingenuity

418
00:15:10,080 --> 00:15:13,200
and our endless curiosity about the universe.

419
00:15:13,200 --> 00:15:15,080
So we've got all these incredible tools, all

420
00:15:15,080 --> 00:15:16,520
this new data pouring in.

421
00:15:16,520 --> 00:15:18,880
What do you think the future holds

422
00:15:18,880 --> 00:15:21,320
for our understanding of dark matter

423
00:15:21,320 --> 00:15:23,040
and the universe in general?

424
00:15:23,040 --> 00:15:25,520
Well, I think we're on the verge of some truly

425
00:15:25,520 --> 00:15:27,400
revolutionary discoveries.

426
00:15:27,400 --> 00:15:28,320
I mean, think about it.

427
00:15:28,320 --> 00:15:31,480
Just a century ago, we didn't even know dark matter existed.

428
00:15:31,480 --> 00:15:33,800
And now, we're building these incredible machines

429
00:15:33,800 --> 00:15:36,400
to map it out, to study its properties.

430
00:15:36,400 --> 00:15:38,600
It's an exciting time to be a cosmologist.

431
00:15:38,600 --> 00:15:40,000
It really is.

432
00:15:40,000 --> 00:15:41,680
Who knows what we'll find next?

433
00:15:41,680 --> 00:15:43,880
Maybe we'll finally get a definitive answer

434
00:15:43,880 --> 00:15:45,080
about dark matter.

435
00:15:45,080 --> 00:15:47,160
Or maybe we'll discover something even more

436
00:15:47,160 --> 00:15:50,040
mind-blowing that completely changes our understanding

437
00:15:50,040 --> 00:15:51,600
of everything.

438
00:15:51,600 --> 00:15:53,440
That's the beauty of science, isn't it?

439
00:15:53,440 --> 00:15:55,720
It's a never-ending journey of discovery.

440
00:15:55,720 --> 00:15:56,320
And who knows?

441
00:15:56,320 --> 00:15:57,720
Maybe some of our listeners out there,

442
00:15:57,720 --> 00:16:00,120
maybe they'll be the ones to make those groundbreaking

443
00:16:00,120 --> 00:16:01,040
discoveries.

444
00:16:01,040 --> 00:16:02,000
I love that.

445
00:16:02,000 --> 00:16:04,640
So to everyone listening, keep those minds curious.

446
00:16:04,640 --> 00:16:06,640
Keep asking those big questions.

447
00:16:06,640 --> 00:16:09,200
And never stop exploring the wonders of the universe.

448
00:16:09,200 --> 00:16:10,720
And if you enjoyed this deep dive

449
00:16:10,720 --> 00:16:12,200
into the mysteries of dark matter,

450
00:16:12,200 --> 00:16:15,320
make sure to follow and subscribe to Cosmos in a Pod

451
00:16:15,320 --> 00:16:16,480
and our YouTube channel.

452
00:16:16,480 --> 00:16:19,000
We've got a whole universe of incredible stories

453
00:16:19,000 --> 00:16:20,320
waiting to be told.

454
00:16:20,320 --> 00:16:22,640
Thanks for joining us on this cosmic adventure.

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00:16:22,640 --> 00:16:41,520
And as always, keep looking up.