Universe: how big can it possibly be?
People struggle to realize how big the universe. The reason
is that everything here on Earth, and even the Earth itself, is very small while
associated to the enormous measure of the universe.
Hence let's think about it a dissimilar way, by
using something we see and interrelate with every day like light.
However we imagine light to be instant, photons
of light actually take time to travel from one side of the room to the other.
For instance, a photon of light leaving the Sun has travelled about 10 million
kilometers comparable to travelling around the Earth 250 times.
Light that leaves our second nearest star,
Proxima Centauri, takes just over four years to reach Earth and consequently we
can define it as four light years away.
Therefore, if we look at Proxima Centauri, we
would not be seeing the star as it is right now, but how it 'was' 4 years ago!
We see everything in the universe as they were
in the past, whether they're on the other side of the galaxy or on the other
side of the room.
To take this thought advance, the nearest large
galaxy for us is Andromeda which is so big and close that you can see it in the
night sky with your bare eyes.
Certainly we are seeing is 1,000's of billions
of stars in a conformation equally to our Milky Way. Though, entirely those
stars are about 2.5 million light years away, which means we are seeing
Andromeda as it was 2.5 million years ago.
The whole universe is overwhelmed with galaxies
just alike the Milky Way and Andromeda, as well as using our utmost powerful
telescopes we can see light from galaxies that have taken more than 13 billion
years to reach us!
Meanwhile a photon of light left one of these
galaxies, life flashed into reality and progressed. Dinosaurs ruled the Earth.
Humans seemed, advanced tools, art, science and technology, made the Hubble
Space Telescope, placed it into orbit and lastly stopped that lowly photon on
its 13 billion year excursion!
The universe is about 13.8 billion years old, hence
any light we see has to have been travelling for 13.8 billion years or less and
we call this the 'observable universe'.
However, the detachment to the edge of the
observable universe is about 46 billion light years since the universe is escalating
every time.
Whereas that Photon has been travelling over
space, the universe has extended. We have moved away from the point where the
light was released, and it has moved away from us as well.
Yet, the light might have only travelled for
13.8 billion years, the detachment from us to the point it came from is, at
present, 46 billion light years!
Accordingly how big is our Universe? Fine
we don't actually know, and then it is gigantic. So gigantic that even light
hasn't had time to cross it in almost 14 billion years! Plus it is still
becoming bigger all of the time.
