How Large The Earth

Photo credit: Kevin M. Gill via Source / CC BY-SA

The earth is a planet, small world moves in orbit around a star and a half old, the sun within Earth's average of 149.6 million km (1 astronomical unit = 1 au). Earth's closest neighbor is the Moon around the Earth with a period of 27.3 days. The average distance between the Earth and the Moon (measured from the center of the Earth to the Moon center) is 384 400 km, a distance which is approximately equal to ten times the journey along the Earth's equator. The most distant planet is Neptune within an average of about 30 au from the Sun.

Compared with the scale of the Solar System, the distance between stars is enormous. The nearest star is just greater than 250,000 times the Sun-Earth distance. Therefore, a better way to feel the distance in the universe is to use the unit how long the light travel a certain distance. With the speed of light in the amount of 300,000 km per second, the light needs 1.3 seconds to reach the Moon, 8.3 minutes to reach the Sun, and 4.1 hours to reach Neptune. The closest star is Proxima Centauri which is 4.2 light years away.

The sun is a member of a large archipelago of stars, gas and dust, known as the Galactic. Our galaxy is called the Milky Way contains more than 100 billion stars, scattered in the disk-shaped system that has a diameter of about 100,000 light years. By convention rather egocentric, we refer to our own star system is a galaxy (with a capital G major). Far beyond our galaxy billions of other galaxies scattered (with a small g). Most spiral galaxies like our own, partially elliptical, and partly irregular, which does not have a specific shape. Since it is located far outside our galaxy, galaxies is sometimes referred to as extragalactic or outer galaxy. Beyond the closest galaxy called Andromeda which has a catalog number M31. Large galaxy is similar to our Galaxy, and the distance is about 2.2 million light years. 

In the universe, galaxies are distributed in the form of clumps. Some, like our own galaxy, is a member of the small group that contains some fruit or a few tens of galaxies member. The others clustered in a cluster (cluster) large containing hundreds, or even thousands of galaxies member. These clusters and joined again into larger structures called superclusters again, that includes the size of 100 million light-years or more and contain thousands or tens of thousands of galaxies. The Local Group of galaxies we are situated on the outskirts of the Virgo supercluster, whose center is located approximately 50 million light years.

The most luminous object (luminuous) which have so far been detected are quasars, which is an object that looked like a star, but emits strong light hundreds, or even thousands of times the light emitted normal galaxies. The most distant quasars, which until now detected is at a distance that may be farther than 13 billion light-years.

Observations - the first time conducted by Edwin Hubble basis- showed that all galaxies and clusters of galaxies beyond the Local Group are moving away from us, and also away from one another between each other, at speeds comparable to the distance - the more distant the galaxy, the faster it moves. This fact shows that the whole universe is expanding, and also means that the galaxies should be very close to each other in the past than now. The development of the universe began with a massive explosion incident of mass and heat the so-called Big Bang (big explosion). Sequentially galaxies formed from the material first and then drawn toward the outside by the development of the universe.

The universe was very, very large in scale space and time. Light that reaches our telescopes from galaxies and quasars most far been propagating through space the universe in a time much longer than the age of the Earth itself. If we look at distant objects is actually we look back in space-time how they looked when the universe was still a very small fraction of age now.

Law Hubble (Hubble's Law) says that speed away galaxies, v, is directly proportional to the distance from us, d. The formula is v = Hd. In this formula, H is the Hubble constant (Hubble constant). The Hubble constant is very important, because it provides the speed rate of the universe was expanding. These constants are also used in Hubble's Law to describe the galaxy's distance measurements based on the red shift. H accurately determine the price is actually very difficult because of the uncertainty in the extragalactic distance scale. Prices were taken ranging from 50 to 100 km / sec / Mpc (15 to 30 km per second per million light years).

Estimate the standard of the age of the universe is based on the price of the Hubble constant. Time Hubble (Hubble time), the age of the universe since the Big Bang is proportional to 1 / H, the amount stood at 10 to 20 billion years. Although there are still many problems and there are still many unanswered questions, it seems the development of the universe began about 13.7 billion years ago. In the meantime, the estimated radius of the universe is also highly dependent on the price of the Hubble constant. Hubble radius, ie the distance to the side of the universe that can still be observed, comparable to the speed of light divided by the Hubble constant, c / H, and also depends on the model of his universe. Estimates now generate the radius of the universe of between 12 billion to 16 billion light-years.