Universe is totally is of matter and energy. The study of the origin of the universe is known as Cosmogony and that of its structure and evolution, cosmology. The age of the universe depends on which theory of cosmology accepts. According to the Big Bang theory, the universe is between 10 and 20 billion years old. Most recent calculations place its age at 13.7 billion years. The steady-state theory holds that the universe has been in existence for all time.
After the Big Bang, the universe started to extend to its present form. According to general science physics matter cannot exceed the speed of light. But in Big Bang theory it is stated that two galaxies have been separated by 93 billion light years in 13 billion years. However, the separation is a natural consequence of general relativity by which it is understood that space can grow with no intrinsic limit on its rate; thus, two galaxies can separate more quickly than the speed of light if the space between them grows.
The Great universe is made of many millions of galaxies. Galaxies are groups of billions of stars that are held together by the force of gravity.
1. The Milky Way :- The word galaxy means milk in Greek language. Before the use of astronomical telescopes the galaxies looked like a milky or cloudy area in the sky and called so. The diameter of Milky Way is 1 lac light years.
2. The Large Megallinic Cloud :- The brightest of all galaxies and visible only in southern hemisphere. It is about 1.7 lacs light years away from our earth and lts diameter is 39,000 light years.
3. Abell 2029 :- The largest galaxy of the Universe with the diameter of 5.6 million light years which is 80 times greater than our own Milky Way Galaxy. It is about 1070 million light years away from our earth.
4. The Sagittarius Dwarf :- It was discovered in 1994 and the nearest of all galaxies. It is about 70000 light years away from our earth.
5. Andromeda Galaxy :- The most distant in the universe that can be seen with naked eye. This is 2,309,000 light years from earth. It has about 300 billion stars and diameter of 180,000 light years. The light we see now from Andromeda left there just after the first humans appeared on our earth.
6.Abell 135 IR 1916 :- The most distant galaxy of our universe. It is amazingly 13.2 billion light years from the earth. In 2004 astronomers at the European Southern Observatory announced the discovery of this galaxy.
THE SOLAR SYSTEM
The solar system is made up of the Sun, the 8 planets and their 172 known moon’s, asteroids and comets travel around the Sun, the centre of our solar system. Most of the bodies in the solar system travel around the Sun along nearly circular paths and all the planets travel about the Sun in the same direction and the opposite of a clock when viewed from above. Solar system formation began billions of years ago, when gases and dust began to come together to form the Sun, planets and other bodies of the solar system.
MATTER AND ENERGY IN THE UNIVERSE
The matter in the universe is subject to various forces, but the greatest force on the cosmological scale is gravitation. This force pulls matter together to form stars. Gravitation also acts to group billions of stars into galaxies and to group galaxies into clusters and super clusters. The main source of energy in the universe is the conversion of the matter of the stars into energy through thermonuclear reactions.
The size and shape of the universe. The solar system was through to be the entire universe, with the Earth at its centre and the distant stars located just beyond the farthest planet. This belief was held until the 16th century when Copernicus advanced the idea that the sun, rather than the earth is at the centre of the system and that the stars are at very great distances compared to the planets. During the first part of the 20th century, astronomers discovered that the sun is only one of billions of stars in the Milky Way Galaxy and is located far from the galactic center. Estimates of size of the universe have been refined as methods of measuring galactic and extra galactic distances have improved. Close stellar distances were at first found by measuring a star’s trigonometric parallax. The fact that the universe as a whole appears to be expanding is indicated by red shifts in the spectral lines of distant galaxies. Hubble’s law makes it possible to estimate their distances from the earth. At present the universe is believed to be at least 10 billion light-years in diameter.
Facts about Universe
The universe is so vast in relation to the matter it contains that it can be compared in the following way: A building 20 miles long, 20 miles wide and 20 miles high that contains 1 grain of sand.
The three most common elements in the universe are
As late as 1820, the universe was throught to be 6000 years old. It is now thought to be between 15 and 20 billion years old.
Scientists believe that hydrogen comprises approximately 90 to 99 percent of all matter in the universe.
A bucket filled with earth would weigh about five times more than the same bucket filled with the substance of the sun. However, the force of gravity is so much greater on the sun that a man weighing 150 pounds on our planet would weigh 2 tons on the sun. A space vehicle must move at a rate of 7 miles per second to escape the earth’s Gravitational pull. This is equivalent to going from New York to Philadelphia in about twenty seconds.