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

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Today we're taking a deep dive into something truly mind

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bending, black holes, those regions of space time

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where gravity is so strong that nothing, not even light,

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can escape.

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Exactly.

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It's like a cosmic trap door where the pull is so intense,

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it warps the very fabric of reality.

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That's a great image.

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So how do these cosmic enigmas form?

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Where does a black hole even begin?

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Well, you might be surprised to learn

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that many black holes are born from the death

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throws of massive stars.

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OK, that makes that sort of.

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But what makes a star massive in this context?

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Is it just any old store that's bigger than our sun?

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Not exactly.

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We're talking about stars at least three

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times the mass of our sun.

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Wow.

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To give you some perspective, that's

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like comparing a grain of sand to a boulder.

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Oh, wow.

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These stars live fast and die hard,

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ending their lives in a spectacular cosmic display.

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So walk me through this stellar lifecycle.

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How does a massive star go from shining brightly

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to becoming a black hole?

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Let's imagine a massive star burning bright in its prime.

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This is its main sequence phase.

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It's fusing hydrogen into helium in its core,

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generating immense energy that pushes outwards,

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counteracting the inward pull of gravity.

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It's a cosmic balancing act.

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Like a cosmic tug of war.

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Exactly.

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Gravity pulling in, fusion pushing out.

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Right.

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But what happens when the star starts

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to run out of hydrogen fuel?

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That's when things get really interesting.

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As the hydrogen dwindles, the star

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starts fusing heavier elements like helium and carbon

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in a desperate attempt to keep the energy flowing.

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This causes the star to swell up into a red supergine hundreds

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of times larger than its original size.

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So it's like the star is puffing itself up.

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Exactly.

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Trying to stay alive.

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But this strategy has its limits.

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Eventually, the star's core becomes predominantly iron,

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and iron is a cosmic dead end.

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It can't be fused to release energy.

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So what happens then?

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Does the star just fizzle out?

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Not quite.

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Without the outward push of fusion energy,

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the core collapses under its own immense gravity.

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And this collapse triggers one of the most powerful explosions

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in the universe.

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Yeah.

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A supernova.

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Wow, that's got to be a sight to see.

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What happens during a supernova?

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Think of it as a star's grand finale.

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The outer layers of the star are blasted into space

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with incredible force, spewing out heavy elements that

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will eventually seed the formation of new stars

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and planets.

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So even in death, a star gives back to the universe.

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That's pretty amazing.

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But what happens to the core of the star after the supernova?

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Well, that's where things get really interesting.

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The fate of the core depends on its mass.

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If it's below a certain limit, it becomes a neutron star,

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an incredibly dense object made almost entirely of neutrons.

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OK.

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So a neutron star is super dense.

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Yes.

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But not quite a black hole.

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What's the tipping point?

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What pushes it over the edge into black hole territory?

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It's all about gravity.

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If the core's mass exceeds a certain limit,

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about three times the mass of our sun,

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which is called the Tolman-Oppenheimer-Volkoff

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limit, gravity becomes unstoppable.

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So this limit is like a cosmic weight

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limit for a dying star's core.

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You could say that.

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If the core is heavier than this limit,

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gravity wins the ultimate tug of war.

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The core collapses further, squeezing itself

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into an infinitely small point called a singularity.

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Hold on.

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Infinitely small.

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Doesn't that defy logic?

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It does seem counterintuitive, but that's

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the nature of a singularity.

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It's where our current understanding of physics

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breaks down.

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At this point, the density becomes infinite,

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and the gravitational pull becomes so strong

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that nothing, not even light, can escape.

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That's when a black hole is born.

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Whoa.

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So it's not just about size.

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It's about density and this extreme warping of spacetime.

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But what about the edge of a black hole,

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the point of no return?

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What's that called again?

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That's the event horizon.

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It's the boundary around the singularity

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beyond which escape is impossible.

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Once you cross the event horizon,

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there's no coming back.

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So the event horizon is like the ultimate cosmic barrier,

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and the singularity is the heart of the black hole

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where everything gets crushed into oblivion.

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That's a great way to put it.

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This is all so mind-boggling.

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And we've only just begun to scratch the surface of black

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holes, haven't we?

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Right.

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I mean, we've been talking about these stellar-mass black

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holes, but aren't there supermassive ones out there,

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too?

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Absolutely.

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Supermassive black holes are millions or even billions

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of times more massive than our sun.

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They lurk at the centers of galaxies,

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including our own Milky Way.

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Their formation is still a bit of a mystery,

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but it's thought that they might grow over billions of years

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by swallowing up stars and gas or even

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merging with other black holes.

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So these supermassive black holes

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are like the ultimate cosmic heavyweights shaping

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the galaxies they inhabit.

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Exactly.

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Welcome back.

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So we've established that black holes are out there,

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warping space time and potentially

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swallowing anything that gets too close.

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Right.

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Here's the thing that blows my mind.

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How do we even know they're there?

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Right.

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They're called black holes for a reason.

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Yeah.

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That's a great question.

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It's a bit like a cosmic detective story,

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where we have to look for clues and piece together

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the evidence.

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Black holes don't emit light that we can see directly,

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but they exert a powerful gravitational influence

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on their surroundings.

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So we're playing cosmic detective,

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looking for their fingerprints on the fabric of the universe.

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Exactly.

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How do we do that?

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One way is by observing the motion of stars.

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OK.

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If we see stars orbiting a seemingly empty point in space

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at incredibly high speeds, it's a strong

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indication that there's a massive unseen object pulling

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on them a black hole.

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Ah.

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So it's like watching a dance, where one partner is invisible,

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but you can tell they're there by how

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the other partner is moving.

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That's a fantastic way to put it.

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And the faster those stars are warping around,

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the more massive the hidden black hole must be.

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That's how we figured out that there's a super massive black

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hole at the center of our own galaxy, the Milky Way.

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That's both amazing and slightly terrifying.

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Right.

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So their gravity is one clue.

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Right.

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Are there any other ways we can see the invisible?

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Yes.

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Another clue comes from the material

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that falls into a black hole.

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As gas and dust gets sucked in, they form a swirling disk

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around the black hole called an accretion disk.

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So it's like a cosmic whirlpool with everything

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spiraling down the drain.

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Exactly.

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And as this material gets closer to the black hole,

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it heats up to millions of degrees,

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emitting intense radiation, including x-rays.

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Hold on.

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You said nothing can escape a black hole.

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Right.

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How can we see radiation coming from them

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if light can't even escape?

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That's where it gets tricky.

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The radiation we detect isn't coming

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from inside the black hole.

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It's from the superheated material in the accretion disk,

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just outside the event horizon.

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So it's like seeing the glow from a fire,

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but never actually seeing the fire itself.

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Precisely.

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By observing these x-rays and other radiation,

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we can study the properties of the black hole,

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estimate its mass and spin, and even get glimpses

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of the chaotic environment around it.

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That's incredible.

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It's like we're piecing together a puzzle,

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using these indirect clues to understand

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these cosmic behemoths.

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Is there anything else we can learn

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from the radiation coming from these accretion disks?

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Yes.

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The radiation patterns can tell us about the black hole's spin.

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If the black hole is spinning rapidly,

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it can actually drag the fabric of spacetime around it,

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creating a sort of cosmic whirlpool

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that affects the radiation emitted by the accretion disk.

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So it's like the black hole is stirring the pot of spacetime,

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and we can see the ripples in the radiation.

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That's a great analogy.

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You know, for something that's invisible,

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we sure have learned a lot about black holes.

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Right.

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But even with all this detective work,

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I imagine there's still a lot we don't know.

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You're absolutely right.

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Black holes are still shrouded in mystery.

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For example, we still don't fully

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understand what happens to the information that

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falls into a black hole.

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Yeah, that's the information paradox we touched on earlier.

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It's like information goes in, but then what?

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Right.

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As it just disappear.

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That's the big question.

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It seems to violate one of the fundamental laws of physics,

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the idea that information cannot be destroyed.

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So physicists are scratching their heads over this.

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Yeah.

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Are there any potential solutions on the table?

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There are some fascinating theories out there.

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Some scientists believe that information

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might be encoded in subtle correlations

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within the black hole's event horizon,

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or even radiated back out in a scrambled form

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through a process called Hawking radiation.

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Hawking radiation.

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Yes.

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Tell me more about that.

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It's a theoretical prediction by Stephen Hawking

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that black holes aren't completely black after all.

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Oh.

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Due to quantum effects near the event horizon,

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they actually emit a faint radiation.

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So even black holes can leak a little bit.

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Exactly.

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And this Hawking radiation could carry away information

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about what fell into the black hole, potentially solving

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the information paradox.

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It seems like the more we learn about black holes,

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the more mind blowing they become.

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Are there any other cutting edge areas of research

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that you're particularly excited about?

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Definitely.

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One of the most exciting developments in recent years

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is the ability to detect gravitational wave ripples

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in the fabric of spacetime that are

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produced by cataclysmic events.

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Oh.

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Like black hole collisions.

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Wait, we can actually detect these ripples in spacetime?

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How is that even possible?

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It's an incredible feat of engineering

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and scientific ingenuity.

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Wow.

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We have these incredibly sensitive observatories

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like LEGO and Virgo that use lasers

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to measure tiny changes in the distance between mirrors.

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When a gravitational wave passes by,

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it stretches and squeezes spacetime,

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and these observatories can pick up those minute changes.

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It's like we've built giant ears that can listen

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to the symphony of the cosmos.

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That's a beautiful way to put it.

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And by studying these gravitational waves,

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we can learn about the masses and spins of the black holes

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involved in the collisions.

293
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Oh, cool.

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Providing us with an entirely new way

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to probe these enigmatic objects.

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So it's like listening to the echoes of these cosmic clashes,

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revealing secrets about the black holes that created them.

298
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Exactly.

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And this is just the beginning.

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As we develop more sensitive instruments

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and build new observatories, we'll

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be able to detect even fainter gravitational waves,

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opening up a new era of black hole astronomy.

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Wow, it seems like we're on the cusp of some truly

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groundbreaking discoveries.

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But before we get ahead of ourselves,

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I think we need to take another quick break.

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We'll be back soon to wrap up our deep dive

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into the mysteries of black holes.

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Welcome back to our final segment on black holes.

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For a long time, these objects were

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seen as purely destructive.

313
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Right.

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Like cosmic vacuum cleaners just gobbling up

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anything in their path.

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But as we've been exploring, the reality

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is far more nuanced and fascinating.

318
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Indeed.

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Black holes are not simply about destruction.

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They play a surprisingly constructive role

321
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in the universe as well.

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OK, so spill the cosmic tea.

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How do these seemingly destructive forces actually

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contribute to the growth and evolution of the universe?

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One key aspect is their influence on star formation.

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Remember those supermassive black holes

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at the centers of galaxies?

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Well, they can actually act as regulators,

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preventing galaxies from becoming too hot

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and forming stars too rapidly.

331
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Wait, I thought black holes were all about sucking things in.

332
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Right.

333
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Not pushing them away.

334
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How does that work?

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It's a delicate balance of energy.

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As material falls into a black hole,

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it gets superheated and releases immense amounts of energy.

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This energy can heat up surrounding gas clouds

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and push them away, preventing them from collapsing

340
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and forming new stars.

341
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So it's like a cosmic thermostat.

342
00:11:54,880 --> 00:11:55,800
Exactly.

343
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Keeping things from getting too hot and chaotic

344
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in the stellar nursery.

345
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That's a great analogy.

346
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And it's this kind of feedback loop

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that helps galaxies evolve over billions of years,

348
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shaping the grand structures we see in the universe today.

349
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That's incredible.

350
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It's like these black holes are playing a cosmic symphony,

351
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orchestrating the birth and death of stars

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across vast expanses of space.

353
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Exactly.

354
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And let's not forget about the heavy elements

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that black holes help to spread throughout the universe.

356
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Oh.

357
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Remember those jets of material we talked about earlier?

358
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Well, those jets can carry elements

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forged in the intense environment

360
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around the black hole.

361
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Interesting.

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Out into the galaxy, enriching the interstellar medium.

363
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So those elements, the building blocks of planets and life,

364
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are essentially the ashes of stars

365
00:12:41,280 --> 00:12:43,000
that were consumed by black holes.

366
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In a way, yes.

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It's a beautiful cycle of cosmic death and rebirth,

368
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where the destruction caused by black holes

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ultimately contributes to the creation of new stars,

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planets, and even the possibility of life itself.

371
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That's pretty poetic when you think about it.

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From cosmic monsters to cosmic gardeners,

373
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black holes really are multifaceted objects.

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They truly are.

375
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And the more we learn about them,

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the more we realize how much we still don't know.

377
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There are so many fundamental questions that remain unanswered.

378
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Like what?

379
00:13:12,320 --> 00:13:13,800
What are some of the biggest mysteries

380
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that are still out there?

381
00:13:15,040 --> 00:13:16,640
Well, for one, we still don't fully

382
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understand what happens inside a black hole at the singularity.

383
00:13:19,560 --> 00:13:21,720
Our current laws of physics break down there,

384
00:13:21,720 --> 00:13:23,680
and we need a new theory of quantum gravity

385
00:13:23,680 --> 00:13:25,640
to truly grasp what's going on.

386
00:13:25,640 --> 00:13:27,640
So it's like peering into the abyss,

387
00:13:27,640 --> 00:13:29,640
and our current understanding just

388
00:13:29,640 --> 00:13:31,080
doesn't quite reach that far.

389
00:13:31,080 --> 00:13:31,720
Exactly.

390
00:13:31,720 --> 00:13:33,480
And then there's the information paradox,

391
00:13:33,480 --> 00:13:34,600
which we discussed earlier.

392
00:13:34,600 --> 00:13:37,760
Does information truly get lost when it falls into a black hole?

393
00:13:37,760 --> 00:13:38,440
Right.

394
00:13:38,440 --> 00:13:40,520
Or is it preserved in some way?

395
00:13:40,520 --> 00:13:42,880
Solving this paradox could revolutionize

396
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our understanding of the very nature of reality.

397
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It seems like black holes are not only cosmic enigmas,

398
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but also gateways to some of the deepest

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00:13:50,800 --> 00:13:52,640
questions in physics and philosophy.

400
00:13:52,640 --> 00:13:53,600
I couldn't agree more.

401
00:13:53,600 --> 00:13:55,680
They challenge our understanding of the universe

402
00:13:55,680 --> 00:13:58,480
and push us to explore new frontiers of knowledge.

403
00:13:58,480 --> 00:14:00,360
As we wrap up this deep dive, I'm

404
00:14:00,360 --> 00:14:03,200
left with a sense of awe and a renewed appreciation

405
00:14:03,200 --> 00:14:05,600
for the vastness and mystery of the cosmos.

406
00:14:05,600 --> 00:14:08,240
It's been a pleasure exploring these mind-boggling objects

407
00:14:08,240 --> 00:14:08,760
with you.

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00:14:08,760 --> 00:14:10,960
And a huge thank you to you, our listeners,

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for joining us on this cosmic adventure.

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00:14:13,200 --> 00:14:15,600
We hope you found it as fascinating as we did.

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00:14:15,600 --> 00:14:18,200
Don't forget to follow and subscribe to Cosmos in a Pod,

412
00:14:18,200 --> 00:14:20,360
and check out our YouTube channel for more deep dives

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00:14:20,360 --> 00:14:22,280
into the mysteries of the universe.

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Until next time, keep looking up and stay curious.