Jul 06 / Universe / 5 min read
(Refer to part 1)
Starting from where I left off last time; In this blog we will dive deeper into the Universe. Even Though we humans can imagine almost anything we want. It is very difficult for us to even think of the distances that are a part of normal discussion about the Constituent spatial scales of the observable universe. Something else which I would like to clear in this blog too is that the ‘Delving Deeper’ series describes only the size and scale of the Universe.
The Milky Way Galaxy is a spectacle of its own but as we zoom out even further it gets even more interesting. Our milky way is not alone as it is the part of the ‘Local Group’ which is shared by 54 other galaxies. Some of the most famous of them being the Andromeda Galaxy, Triangulum galaxy and our Milky Way galaxy. The Local Group has a total diameter of roughly 3 megaparsecs which is about 10 million light years, and a total mass of the order of 2×1012 solar masses where 1 Solar Mass equals (4×1042 kg). The Milky Way and the Andromeda Galaxy form two collections of galactic systems which are at a distance of about 3 million light years from each other. An interesting fact about them is that they are moving toward one another with a velocity of 123 km/s which means about 4.5 billion years in the future the two galaxies would collide. People like calling it the formation of Milk-Dromeda. These kinds of galactic events would take billions and billions of years to happen thus we may not be around to watch them. Unless we upload our brains into computers or become a type 4 civilisation(New Blogs coming soon).
Just like our Galaxy, even our local group is a part of a bigger group called the Laniakea Supercluster. It is made up of about 100,000 to 150,000 Galaxies. With all these Galaxies the Laniakea Supercluster is about 520 million light years in length. Now it may seem that it just gets larger as I explain but there is a limit to what we can Observe. Thus we come to an “end” of our Observable Universe. The Diameter of the Observable Universe is about 8.8×1026 m metres and has a volume of about 3.566×1080 m^3 , weight of about 1.5×1053 kg.There may be 2 trillion galaxies in the observable universe, although that number has recently been estimated at only several hundred billion based on new data from New Horizons mission.
Why there is a edge to the Universe: The most famous theory about the origin of the Universe is the Big Bang Theory. It is a very successful model which tells us about the existence of the Observable Universe and it’s expansion.By definition the expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. The interesting fact about the expansion of the universe is that the objects on the fabric of space don't move whereas the metric of the fabric itself changes. Due to the universe's accelerating expansion, all objects which are currently observable, outside our local supercluster( Laniakea) , will eventually appear to freeze in time, while emitting progressively redder and fainter light. This holds as, redshift as defined by the Big Bang theory and general relativity is caused due to the expansion of space. Which implies that the further a galaxy is from us the more red shifted it will appear due to stretching of the Electromagnetic wave. One American astronomer Hubble first observed that the redshift of galaxies was directly proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster.