THE LIMITS OF HUMANITY

The Large Magellanic Cloud  , a galaxy which belongs to the Local Group 

With our current technology sending a human to the closest star will take thousands of years. Even assuming that humanity will become a type 3 civilization ( an example of type 3 civilization is the galactic empire in the Star Wars series ) there will always exist a boundary beyond which  we could never go further: the Local Group. The Local Group is the group of galaxies to which our galaxy belongs; it includes about 70 galaxies , most of which are small in size, which is 0.00000000001% 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.

But  why can't we go further?

The empty space isn't empty at all , it has a certain energy indeed from 0 we can pull out infinite numbers ( -1,+1,-2,+2,-3,+3...) , the same thing happens on a microscopic scale : out of nowhere appear continually particles and antiparticles which divide and immediately after they come back together producing energy . This phenomenon is called  "quantum fluctuation" . It is believed that immediately after the Big Bang a huge negative pressure has caused an extremely rapid expansion called  "cosmic inflation" . So these quantum fluctuations were stretched and microscopic distances became huge distances.

In small scales gravity won this inflation and began to pull everything back together while in larger scales the gravity was overcome by inflation. Six billion years ago a new force took over : the dark energy that  speeded up the expansion of the universe . Expansion of the universe doesn't mean that   new space is created out of nowhere but it  means that the space between two objects not gravitationally bounded is stretching . This implies that the further an object is the faster it moves away , every mega parsec ( 3.26 million of light years ) the speed increases by 74 km/s . As I said before this model is valid only on relatively large scales , between object not gravitationally bounded , such as group of galaxies . Almost all the galaxies are moving away from us except some that are approaching us including Andromeda which will merge with the Milky Way in 5 billion of years .

An artistic representation of the collision of the two galaxies , seen from the Earth 

The nearest group of galaxies to our local group " Maffei I" is 10 million light years distant from us 

( so it moves away with a speed of 226km/s ) . As   time goes by no information outside the local group will be able to reach us, the universe will recede from us . In fact photons lengthen with space, increasing the wavelength, so they will be shifted to such long wavelengths that they will be undetectable. Milkdromeda (super original name) will be an island in the darkness slowly getting darker and darker. In the end we can consider ourselves lucky, we exist in the perfect moment: we can see not only our future but also our most distant past. If you think about it, the inhabitants of Milkdromeda won't be able to discover things we know, they will think that the whole universe is a bubble immersed in the infinite space. In any case the local group with its trillion stars is certainly large enough for humanity. After all, we haven't figured out how to leave our Solar System and we have billions of years to explore our galaxy .

GIORDANO C.