Written by: Anukrama Poudyal - 22031, Grade XII
Posted on: 26 November, 2021
Our planet is one of nine planets that circle a star we call the sun. Our solar system is a collection of stars and planets. The sun is part of a galaxy (it really resides on the edge of the galaxy—out in the suburbs), many of which are likely to develop their own solar systems. In all, our galaxy has around 1011 stars.
This galaxy is known as the Milky Way. The Milky Way is one of countless galaxies in the universe. It's a member of the 'local group,' a cluster of galaxies bound together by gravity. The local group contains 18 galaxies. Other clusters of galaxies have been discovered, some of which include as many as 800 galaxies weakly bound together by gravity.
The number of galaxies visible from Earth is believed to be 3109. Many of these galaxies are larger than our own Milky Way. When multiplied together, this equals 1020 stars in the cosmos (if our galaxy is, as it appears to be, of a typical size). It is believed that the universe contains more stars than there is sand on a beach.The entire collection is referred to as the observable universe by astronomers. Two problems restrict what we can observe. To begin with, the light from a galaxy becomes fainter as it gets further away, necessitating the use of a big telescope to view it. It is estimated that the universe is around 15 billion years old, which means that any galaxy more than 15 billion light years distant will be invisible to us since the light has not yet reached us! Without a doubt, the true cosmos is much larger than what we can see right now. It's just lately become clear how much bigger it is. If our current theories are right, the observable world is a speck in an incomprehensibly larger universe.
Cosmology is a unique field of study in physics. Cosmologists research the numerous possibilities for how the universe came to be, how it evolved, and how it will end (including the possibility that it will not!). There is almost no other topic that deals with such vast issues. The fact that this issue has become part of mainstream physics is a remarkable testament to science's ambition. Cosmologists are now convinced that they have a "standard model" of how the universe originated, thanks to contributions from astronomy and particle physics ideas.
The big bang is the name given to this concept.Consider a period of time that occurred fifteen billion years ago. The volume of all stuff in the cosmos is substantially less than it is now—even smaller than the volume of the earth. There are no galaxies, at least not in the way we think of them from our everyday lives. The universe will continue to grow in the future, although at a slower rate than it did previously due to the tremendous inflation. As the cosmos expands, it cools. As the rest of the universe's gravity pulls it back, each particle loses energy. What was the cause of the Big Bang? We have no idea. As the temperatures and pressures that prevailed shortly after the big bang, our notions of how matter should behave don't function.
