When it comes to space exploration, how far can we actually go? Is there a true limit, even with the sci-fi tech of the future, to humanity’s reach beyond Earth?
As the Kurzgesagt - In a Nutshell video above explains, humanity lives in a small area of the Milky Way - an average spiral galaxy that’s about 100,000 light-years across. Like many other spiral galaxies, it's full of stars, planets, gases, and dark energy, with a supermassive black hole in the centre. Though we might think of our galaxy as crowded, most of it is actually empty space.
Scaling up from there, the Milky Way and Andromeda galaxies, along with about 50 dwarf galaxies, belong to our 'local group', which spans roughly 10 million light-years. Our local group is just one out of hundreds of other groups that make up the Laniakea Supercluster, which, in turn, is just a tiny part of the observable Universe.
Now that we know where we stand spatially, let’s assume that humanity’s future rockets will meet a science fiction level of interstellar travel. With all of these advances, how far from Earth could we possibly get?
Sadly, not that far. In fact, humanity will only ever get to explore the local group.
But that’s okay, though, right? The local group is 10 million light-years in diameter. Surely that’s a considerable amount of Universe? Nope! According to the video, our local group is just 0.00000000001 percent of the observable Universe. That’s 100 billionth of a percent! In other words, humanity’s reach miniscule, which is a total bummer.
So what’s holding us back? In short: space itself. Space isn’t truly empty like it appears - it’s actually full of energy and different parts of the Universe have denser pockets than others. To understand this, we have to go all the way back to the Big Bang, which inflated the Universe from the size of a marble to an unimaginable size.
During this event, quantum fluctuations stretched out, making denser areas of the Universe. Since then, gravity has been pulling everything back together because that’s just what gravity likes to do. In smaller areas, like our local group, gravity formed galaxies and everything that comes along with them.
Over time, these groups grew apart, thanks to mysterious nature of dark energy, which researchers say is responsible for the expansion of the Universe, though they know almost nothing about it. This means that our local group isn’t bound to other groups by gravity, causing them to float away from us.
Since these galaxies are traveling at breakneck speeds away from us, even if we were to enter intergalactic space, we’d never move fast enough to reach them. In the future, this expansion will continue, and we'll eventually lose the ability to even see these other groups.
While these groups move away, the galaxies inside our group will come together to form 'Milkdromeda', a combination of our galaxy and Andromeda (if you couldn’t tell by that name). All of this means that, if there are still people around when Milkdromeda forms, they'll look out at the Universe and see nothing but darkness (sorry for the existential crisis).
Sounds pretty bleak, right? In a way, sure, but it’s important to remember that we haven’t even made it to Mars properly yet. There’s still a lot out there to explore before local groups separate enough for us to not see them. We’re talking billions of years - plenty of time!
Check out the video above to learn more.