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  • Is there a border we will never cross?

  • Are there places we will never reach, no matter how hard we try?

  • Turns out there are.

  • Even with science fiction technology, we are trapped in our pocket of the Universe.

  • How can that be? And, how far can we go?

  • We live in a quiet arm of the Milky Way; A spiral galaxy of average size,

  • about 100,000 light years across

  • consisting of billions of stars, gas clouds, dark matter, black holes, neutron stars,

  • and planets, with a supermassive black hole in the galactic centre.

  • >From afar, our galaxy seems dense, but in reality, it consists, mostly, of empty space.

  • With our current technology, sending a human to the closest star, would take thousands of years.

  • So, our galaxy is pretty big.

  • The Milky Way is not alone, though.

  • Along with the Andromeda galaxy, and more than fifty dwarf galaxies,

  • it's a part of "The Local Group";

  • a region of space about ten million light years in diameter.

  • It is one of the hundreds of galaxy groups in the "Laniakea Supercluster",

  • which, itself is only one of millions of superclusters,

  • that make up the observable universe.

  • Now, let's assume, for a moment, that we have a glorious future;

  • humanity becomes a type three civilisation,

  • does not get wiped out by aliens,

  • and develops interstellar travel based on our current understanding of physics.

  • In this best case scenario, how far could we possibly go?

  • Well; the local group.

  • It's the biggest structure that humanity will ever be a part of.

  • While it's certainly huge, the local group accounts for only 0.00000000001 % of

  • the observable universe.

  • Let this number sink in for a moment.

  • We are limited to a hundred billionth of a percent of the observable universe.

  • The simple fact that there is actually a limit for us, and that there is

  • so much universe that we will never be able to touch, is kind of frightening.

  • Why can't we go further?

  • Well, it all has to do with the nature of nothing.

  • Nothing, or empty space, isn't empty but has energy intrinsic to itself;

  • so-called "quantum fluctuations".

  • On the smaller scale, there is constant action, particles and antiparticles

  • appearing and annihilating themselves.

  • You can imagine this quantum vacuum as a bubbling part:

  • with denser, and less dense regions.

  • Now, let's go back 13.8 billion years when the fabric of space

  • consisted of nothing at all.

  • Right after the big bang, in an event known as cosmic inflation, the observable universe

  • expanded from the size of a marble to trillions of kilometres, in fractions of a second.

  • This sudden stretching of the universe was so fast and extreme,

  • that all those quantum fluctuations were stretched as well,

  • and subatomic distances became galactic distances,

  • with dense and less dense regions.

  • After inflation, gravity began to pull everything back together.

  • At the largest scale, the expansion was too quick and powerful

  • to overcome but in smaller scales, gravity emerged victorious.

  • So, over time, the denser regions, or pockets, of the universe,

  • grew into groups of galaxies, like the one we live in today.

  • Only stuff inside our pocketThe Local Groupis bound to us gravitationally.

  • But wait, what is the problem then?

  • Why can't we travel from our pocket, to the next one?

  • Here, dark energy makes everything complicated.

  • About six billion years ago, dark energy took over.

  • It's basically an invisible force or effect, that causes,

  • and speeds up the expansion of the universe.

  • We don't know why, or what dark energy is, but we can observe its effect clearly.

  • In the early universe, there were larger, cold spots around the local group,

  • that grew into clusters with thousands of galaxies.

  • We are surrounded by a lot of stuff, but none of those structures and galaxies

  • outside of the local group are gravitationally bound to us.

  • So the more the universe expands, the larger the distance between

  • us and other gravitational pockets becomes.

  • Over time, dark energy will push the rest of the universe away from us,

  • causing all the other clusters, galaxies, and groups to eventually become unreachable.

  • The next galaxy group is already millions of light years away,

  • but all of them are moving away from us, at speeds we can't, ever, hope to match.

  • We could leave the local group, and then fly through intergalactic space,

  • into the darkness, but we would never arrive anywhere.

  • While we will become more and more stranded, the local group will become more tightly bound,

  • and merge together to form one giant elliptical galaxy, with the unoriginal name "Milkdromeda"

  • in a few billion years.

  • But it becomes even more depressing:

  • at some point, the galaxies outside the local group, will be so far away,

  • that they will be too faint to detect, and the few photons that do make it to us,

  • will be shifted to such long wavelengths, that they will be undetectable.

  • Once this happens, no information outside of the local group will be able to reach us.

  • The universe will recede from view.

  • It will appear to be dark and empty in all directions, forever.

  • A being born in the far future in Milkdromeda,

  • will think there is nothing but its own galaxy in the entire universe.

  • When they look far into empty space, they will only see more emptiness and darkness;

  • they won't be able to see the cosmic background radiation,

  • and they won't be able to learn about the Big Bang.

  • They will have no way of knowing what we know today;

  • the nature of the expanding universe, where it began, and how it will end.

  • They will think the universe is static and eternal.

  • Milkdromeda will be an island in the darkness, slowly getting darker and darker.

  • But still, with its trillions of stars, the local group is certainly

  • large enough for humanity.

  • After all, we still haven't figured out how to leave our solar system,

  • and we have billions of years to explore our galaxy.

  • We have the incredible luck to exist at the perfect moment in time to see,

  • not only our future but also our most distant past.

  • As isolated and remote as the local group is, we can perceive the entire universe,

  • grand and spectacular as it is right now.

  • This video was sponsored by SquareSpace.com/nutshell

  • Do you feel isolated in a humongous universe?

  • Why not set up a website or blog and share your thoughts with other

  • humanoids around you?

  • Squarespace lets you do that with easy-to-understand tools

  • very quickly and without any knowledge of web design.

  • You can also use the code "NUTSHELL" to save 10 % and support Kurzgesagt

  • in making more videoes about our place in the universe.

  • Thanks so much for the help with the video to Ethan Siegel.

  • Follow his astronomy blog here.

  • You can support us directly at Patreon or get Kurzgesagt merch here.

  • It really helps.

  • It is awesome that you watched this far, so we have made a playlist for you about more universe stuff.

  • Subtitles made by Sebastian Winkelmann

  • Subtitles by the Amara.org community

Is there a border we will never cross?

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How Far Can We Go? Limits of Humanity.

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    mommy posted on 2016/05/23
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