THE UNIVERSE AND THE LIFE OF SUN

Science is a metnod of knowlwdge. Depending on the available events we have to form a theory to explain the same . Accordingly, Newton's law of gravitation came. Latter as a further improvement Einsteins theory of relativity came. At the time of Newton time is different from space which consists of three dimensions. But according to Einsteins time cannot be seperated from space. Time is the fourth dimension.
Several theories were put forward regarding the creation of the Universe. The BIG BANG theory is the most popular theory among the scientists on the creation of the universe.
The Sun is only a tiny speck in this boundless and ever expanding universe. It is created in the galaxy ,known as Milkyway. The Galaxy Milkyway contains about 100,000 million stars. It is shaped like a disc with a bulge in the middle. The stars on this disc lie on arms that curve out from the central bulge. It is a spiral galaxy.The whole galaxy rotates. The diameter of our galaxy, milkyway is about 100,000 light-years.( A light-year is the distance travelled by light in one year, at the speed of 300,000 kilometers per second). The Sun is about 25000 light years from the centre of Milkyway. The Sun revolves around the center of galaxy in about 225 million years.
There are many galaxies in the universe. Some are spiral in shape (just like ours), some are round or oval in shape and are called as ellipticals and others are irregular galaxies. The nearest galaxies to our own galaxy are called Magellanic clouds. They are irregular Galaxies. Andromeda Galaxy is one of the few galaxies we can see with naked eye, even though it lies over 2,000,000 light years away. It is a spiral galaxy just like our galaxy but is bigger.
Astronomers think that the Universe was formed about 15000 million years ago resulting from BIG BANG. At present it is an expanding universe. Nobody knows what will happen to the universe in the far distant future. It may contract again or may continue expanding.
The Sun is formed about 5000 million years ago. It will start dying after the entire Hydrogen in it is converted as Helium. Four Hydrogen atoms combine together to form one Helium atom, resulting in light and heat etc. This process is likely to continue for another 5000 million years more. Then it swells up into a red giant 20 to 30 times larger. It slowly shrinks puffing off rings of gas and finally becomes a dense white dwarf.
Sun is an average star. A middle weight star, which has mass more than Sun, at the end of its life collapses to form tiny neutron star. A heavy weight star which may be about 10 times the mass of Sun explodes as a supernova and collapses into a black whole, a region of enormous gravity.