Limits of Humanity — Beyond the Galaxies…
Did you ever have a question in your mind about how the Universe is put together? Isn’t it crazy that the Universe consists of several components, and our Earth is just a tiny drop in the vast ocean of the Universe? Let’s explore!
We live on the planet Earth, which along with the other planets and the Sun, make up the solar system, and many other such systems form a galaxy. Now we all know that there is not just one galaxy; instead, there are billions of them. The galaxies which are close to each other form galaxy clusters, the Local Group, which consists of the Milky Way, being one of them. Many such groups are together known as superclusters and all such superclusters collectively make up what we call the observable Universe.
Now that we know about the fascinating things out there, how great would it be if we could reach and explore them all? But can we really do so, or is there a limit up to which we can go?
Even though the Universe is limitless, the parts we can reach are bounded, and there is a limit to how far we can go. Our Universe is expanding, cooling, and gravitating from an initially hot, dense state known as the Big Bang. About 6 billion years ago, due to an unbelievably large expansion of the Universe (cosmic inflation), a new form of energy came into existence: dark energy, which caused the Universe’s expansion to accelerate.
We can think of dark energy as a force that pushes every two things away from each other, thereby causing the Universe to expand at a very fast rate. But still, this force is not strong enough to negate the gravitational force between the galaxies of our Local Group — consisting of our Milky Way, Andromeda, and Triangulum Galaxies, apart from several other smaller dwarf galaxies. As time passes, all the galaxies in our local group will merge, forming the Milkdromeda, a giant elliptical galaxy. This is expected to occur in about 4 billion years and will witness the most picturesque night sky ever.
None of the structures or galaxies outside of our local group are gravitationally bound to us. So the more the Universe expands, the greater the distance between us and other structures becomes, and over time the dark energy will push the rest of the Universe away from us, making these unreachable for us. Things that pass the cosmological horizon get entirely out of our reach. We are only able to observe their distant past due to the light emitted by them billions of years ago. At some point, the galaxies outside the Local Group will be so far away that they will be too faint to detect. Once this happens, no information from outside of the local group will be able to reach us; the Universe will appear to be dark and empty forever.
Even if we travel at light’s speed, 94% of the Universe is still out of our reach, and out of the remaining 6% also, the human civilization is most likely to be able to explore only the Local Group, the group of galaxies containing the Milky Way. For this to be possible, humans need to be a type III civilization. But what are these different types of civilizations that we are talking about? Let’s find out.
Kardashev, a Russian-Soviet astronomer, developed a scale to measure the level of technological advancement of civilization and classified them into three types. A type-I or planetary civilization is one that can access and utilize all the energy available on its planet. A type-II or stellar civilization can develop a way to consume all the energy of a star. Finally, a type-III or galactic civilization is able to capture all the energy emitted by its galaxy.
We, humans, are currently not even a type-I civilization, and it will take humanity at least another four centuries to reach there, probably by covering the whole planet with solar panels. Now that sounds crazy, right?
So it is safe to assume that even if we develop futuristic technologies like nuclear fusion technology, antimatter storage capabilities, or even the ability to harness dark matter, there are still parts of the Universe that will be forever inaccessible to us. But still, we are lucky enough to exist in a time where we can not only explore the possibilities of the future but also learn about our most distant past. The creatures born in the far future in the Milkdromeda will think that there is only their galaxy in the whole Universe; all they would see is more emptiness and darkness. They will never be able to learn about the Big Bang and won’t know what we know today.
By,
Amrisha Vardiya
Shivam Agrawal
Credits: The datum for this blog is taken from Ethan Siegel’s script for the YouTube channel ‘Kurzgesagt — In a Nutshell’.
