00:00Look up at the sky tonight, and you'll see a vibrant, packed cosmos.
00:05We are living in a golden age of the universe, surrounded by billions of glowing galaxies and active star systems
00:14that feel like the last forever.
00:17But every single point of light you see is operating on a strict death sentence.
00:23If we fast forward the cosmic clock one trillion years into the future, we reach the darkest chapter of our
00:31universe.
00:32The absolute laws of physics dictate a systematic, irreversible dismantling of the cosmos.
00:40The bright sky we see today is a temporary state.
00:44This map shows the trajectory of our galaxy and our closest neighbor.
00:49Roughly 4.5 billion years from now, the Milky Way and the Andromeda galaxy will collide, merging together to form
00:58a massive elliptical structure known as Milkdromeda.
01:02While that merger is happening locally, something else is driving the rest of the universe apart.
01:09Dark energy is forcing the empty space between all other galaxy clusters to accelerate at an accelerating rate.
01:17Fast forward one trillion years, and that expansion will push every other galaxy past a cosmic boundary.
01:26Because the space between them is expanding faster than the speed of light, the lines representing the light from those
01:33distant galaxies stretch out, completely failing to reach Milkdromeda.
01:37Any future astronomers living in our solar system will be physically blinded to the rest of the cosmos.
01:44When they look through their telescopes, they will see an infinite pitch black void, and they will deduce that their
01:51single, isolated galaxy is the entire universe.
01:55If we look inside the borders of Milkdromeda, the stars themselves tell a story of decay.
02:02Massive bright blue giants and sun-like stars burn through their nuclear fuel rapidly, meaning they will have died out
02:09long before this era.
02:11The only survivors left in this dark era are red dwarfs.
02:15These tiny, faint stars operate on a highly efficient set of internal physics.
02:22This animated diagram shows the interior of a red dwarf.
02:27Notice the continuous circular loops moving between the core and the outer edge.
02:32This process is called stellar convection, and it means the star constantly churns fresh hydrogen fuel into its core, rather
02:42than letting it sit unused on the surface.
02:45Because they recycle every drop of their fuel, a single red dwarf can burn steadily for up to 10 trillion
02:53years,
02:54far outlasting the larger stars that extinguish near the beginning of the timeline.
02:59Any rocky planets locked in orbit around these dim red embers will serve as the absolute last sanctuaries for life,
03:09huddling closely for warmth around the universe's final burning fires.
03:14But even the most hyper-efficient star cannot outrun thermodynamics.
03:20Eventually, the red dwarfs must exhaust their fuel supply.
03:24To make new stars, the universe needs vast clouds of cold, free-floating hydrogen gas.
03:32But as each generation of stars dies, they permanently lock that matter away into unusable stellar corpses,
03:42such as white dwarfs, dense neutron stars, and black holes.
03:46This line graph shows the universe's total reserve of free hydrogen dropping steadily over time.
03:54When it finally plummets to absolute zero, the creation of new stars stops entirely.
04:03Astrophysicists call this the degenerate era.
04:06The final generation of red dwarfs lack the mass to explode in fiery supernovae.
04:13They will simply fade away in the dark, cooling into dense, dead spheres of helium and carbon known as black
04:21dwarfs.
04:22The universe will have officially gone bankrupt of its most vital resource.
04:27Once the last black dwarf cools, all starlight in the cosmos is irreversibly extinguished.
04:35What remains is a pitch-black graveyard.
04:39The new rulers of space are completely dark, dead stellar remnants,
04:45including cold white dwarfs and ultra-dense neutron stars,
04:49and spinning pulsars ticking away like lonely cosmic metronomes in the absolute silence.
04:57Occasionally, gravity pulls two of these dead remnants together.
05:01They spiral inward, releasing a sudden, violent flash of light
05:05before the void instantly swallows the space back into total darkness.
05:11The final inheritors of this dark reality are supermassive black holes,
05:16quietly lurking in the center of dead galaxies,
05:20and slowly consuming whatever stray rocks or dust drift into their paths.
05:25In this ultimate era, the universe is physically stripped of light, warmth, and information.
05:32It becomes an infinitely cold, quiet void, where the vibrant past is entirely erased.
05:39Now, pull yourself back to the present day, and just look out at the sky above us tonight.
05:45Our current existence is packed with specific, temporary luxuries.
05:50We have neighboring galaxies we can clearly see and study,
05:55with brightly burning stars to navigate by,
05:58and a sun that showers our planet in steady, life-giving warmth.
06:03Seeing exactly how the universe ends shifts our perspective on right now.
06:08It leaves us with a profound gratitude for the sheer luck of existing
06:13during this vibrant, fleeting window in cosmic history.
06:17If you want to keep exploring the deep mysteries of our universe,
06:21hit the subscribe button, and click the video on your screen right now
06:25to jump from the distant future to the present day, and discover the dead-
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