whatnis mean by light year
A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km. More p recisely, one light-year is equal to 9,500,000,000,000 kilometers. Why would you want such a big unit of distance? Well, on Earth, a kilometer may be just fine. It is a few hundred kilometers from New York City to Washington, DC; it is a few thousand kilometers from California to Maine. In the universe, the kilometer is just too small to be useful. For example, the distance to the next nearest big galaxy, the Andromeda Galaxy, is 21 quintillion km. That's 21,000,000,000,000,000,000 km. This is a number so large that it becomes hard to write and hard to interpret. So astronomers use other units of distance. In our solar system, we tend to describe distances in terms of the Astronomical Unit (AU). The AU is defined as the average distance between the Earth and the Sun. It is approximately 150 million km (93 million miles). Mercury can be said to be about 1/3 of an AU from the Sun and Pluto averages about 40 AU from the Sun. The AU, however, is not big enough of a unit when we start talking about distances to objects outside our solar system. For distances to other parts of the Milky Way Galaxy (or even further), astronomers use units of the light-year or the parsec . The light-year we have already defined. The parsec is equal to 3.3 light-years. Using the light-year, we can say that : * The Crab supernova remnant is about 4,000 light-years away. * The Milky Way Galaxy is about 150,000 light-years across. * The Andromeda Galaxy is 2.3 million light-years away.
in a second light can go 3*10^8 meter in that speed light can travel which distance in a year (generally according to 365 days) is called a light year. it's used to measure very long distance like distance of stars from earth. it's the second big measurement unit of distance. 'Fermi' comes at first.
LIGHT-YEAR serves the same purpose of a scale or footrule that you use to measure length of objects or distances. It is the cosmic 'scale' like foot. How tall somebody is we express in feet. Mt.Everets is said to be 29,021 feet vertically above the mean sea level at its peak. In the same way we say that the distance to the nearest star is 4.3488 LY. Since 1 LY is defined as the distance light travels in 1 year it can be computed as 365.25 X 24 X 3600 X 300,000 km.
One Light-year is the distance that light travels in one year. Considering that 1 year has 365 days + 6 hours, 1 day has 24 x 3600 = 86400 s and that speed of light is 300.000km/s, you derive that 1 light year = 9.500.000.000.000 km (9,5 trillion km). In other words, If you had to go to a place distant 500 Light-year from Earth (a nearby place in terms of universe!) and you could travel at the speed of light, your travel would take 500 years.
When you hear someone say light year they are describing the distance light travels within a year. For instance, Sirius, the brightest star in the night sky, is found within the constellation Canis Major. It is approximately 8 light years away.
