The universe as we know it today had a beginning, therefore it has an age. According to the current observational results (such as CMB), the universe was born 13.8 billion years ago. This is the event (t=0) we call the BIG BANG. The Big Bang is a point (not specific location) in the very early universe, where spacetime came into existence and it has been expanding ever since.
0 Comments
TITLE:"Newtonian cosmology and Friedmann's equation."
AUTHOR: A R Thatcher CITE: European Journal of Physics 3.4 (1982): 202. Cosmology is the study of the universe, from it's birth, very early times, evolution up until now and perhaps even its future and/or demise. The fundamental theory that allow us to study the universe is the Einstein's Theory of General Relativity (GR). GR not only give us a new perspective of gravity, but also allows one to study the dynamics of the universe. A. Friedmann in 1922, proposed a solution to Einstein's Field Equation (now called Friedamnn equation), that predicted an expanding universe and this was verified later by Vesto Slipher and E. Hubble. Where did we come from? How did the universe begin? Are we alone in the universe? These are the questions that human beings have asked ever since they first looked up at the heavens. Many ancient Greek philosophers viewed the universe as a divine, living being whose innermost essence was harmony. According to them, understanding the universe was key to revealing where we came from and our place in the universe.
From 1909 to 1913, Robert Andrews Millikan (1868-1953) performed a brilliant set of experiements in which he measured the elementary charge of the electron (e) and demonstrated the quatized nature of the electrical charge. The apparatus he used is shown in the figure 1 on the left. The apparatus contains two parallel metal plates with a hole in the upper plate through which the oil-droplets passes.
In this blog I am going to explain you why physics is considered to be one of the profound subject of the 21th century. What has physics done for humans and the importance of physicist in this world. It is perhaps the highest-impact, lowest-cost area of basic research. The field advances our fundamental understanding of the universe, and seeds the technologies of tomorrow. Solar cells, computers, wireless technologies, diagnostic imaging – they are all rooted in breakthroughs made by theoretical physicists.
When we look at a spiral galaxy like the one on the left, we see most of its light coming from the central region. Most of the mass is concentrated at the centre of the galaxy which keeps the stars in circular orbit in the galaxy. Because most of the mass of the galaxy is concentrated in the centre, then we would expect that stars further from the centre would move at a slower velocity than stars closer to the centre. For example, in the solar system, most of the mass of the solar system is concentrated in the Sun.The velocities of planets decreases outwards.
Have you ever wondered how astronomers know what stars are made up of just from planet earth? Stars like our own sun are million miles away from us, we don't have that advanced technology that we can go there and check what is the basic structure of stars, its mass and its temperature etc. So how astromers study them from earth? Well in this blog I'm going to explain you how just by using simple techinque they study them.
Matter-Antimatter Asymmetry :
Our universe is observed to consist of matter. Today there is no evidence of antimatter in the form of stars, galaxies, galaxy clusters or any form of cosmological antimatter. However, antimatter should have been plentiful when the temperature of the universe was high enough to create matter- antimatter pairs. In order to prevent complete annihilation of matter and antimatter, About four and one half billion years ago our protosun was slowly collapsing under the force of its gravity. As it did this, due to the immense compression caused by gravity it became extremely hot. Millions of degrees centigrade. The more compact it got, the hotter it got.
|
Archives
June 2015
Categories |