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How Far Can We Go? Limits of Humanity.


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 pocket – The Local Group –
is 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

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