Federal Defence Union
Posted - 2008.09.12 23:39:00 - [3
What is an Astronomical Unit?
Or a Light Year ?
1 AU = 149,600,000 km = 92,960,000 miles
or 490,800,000,000 feet = 8.317 light minutes
63,024 AU's = 1 ly (light-year) Whats a ly
Definition: An Astronomical Unit is the mean distance between the Earth and the Sun. It is a derived constant and used to indicate distances within a solar system. The Earth orbits at a distance of 1 AU from the Sun.
Technical Definition: AU is short for Astronomical Unit and defined as: the radius of a Keplerian circular orbit of a point-mass having an orbital period of 2*(pi)/k days (k is the Gaussian gravitational constant). Since an AU is based on radius of a circular orbit, one AU is actually slightly less than the average distance between the Earth and the Sun (approximately 150 million km or 93 million miles).
Historical Background: Tycho Brahe estimated the distance between the Sun and the Earth at 8 million kilometers (5 million miles). Later, Johannes Kepler estimated the AU was at 24 million kilometers (15 million miles). In 1672, Giovanni Cassini made a much better estimate by using Mars. By observing Mars from Paris and having a colleague, Jean Richer, also observe Mars at the same time in French Guiana in South America, Cassini determined the parallax of Mars. From that Cassini was able to calculate the distance from Earth to Mars, and then the distance from Earth to the Sun. Cassini calculated the AU to be at 140 million kilometers (87 million miles), which is lower, but very close to the modern day number.
A light year, abbreviated ly, is the distance light travels in one year: roughly 9.46 × 1012 kilometers (or about 5.88 × 1012 miles). More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely far away from any gravitational or magnetic fields, in one Julian year (365.25 days of 86400 seconds each). Since the speed of light in a vacuum is 299,792,458 m/s, one light year is equal to 9,460,730,472,580,800 m, or about 9.46 pentameters.
So if 1 Light Year = 63,024 AU and an AU is 92,960,000 miles.
That makes a Light Year 5,878,883,360,000 Miles
Thats 5 Trillion 878 Billion 883 Million 360 Thousand Miles
GOT IT NOW !!! Or did I just Fry Your Brain :)