A lightyear is a non-fundamental unit of length or distance equivalent to 9,500,000,000,000,000 meters.It is a much more bigger unit of distance created by scientists

to represent the distance that light travels in one year.Lightyear is the perfect unit,used by astronomers,at least for now,to measure the distance of celestial bodies because they

are far away from us and the Sun.Symbolically,it is represented by "ly."

Eventhough lightyear is so big,it could still be compared to other length units.So,there exist a conversion factor in each case.One lightyear is 6.0 x 10 12 miles,9.5 x 10 12 kilometers,3.7246 x 10 17 inches,1.0346 x 10 16 yards,3.1038 x 10 16 feet,5.1731 x 10 15

fathoms,5.8785 x 10 12 statute mile,6.3240 x 10 04 Astronomical Units,5.1083 x 10 12 nautical miles,and 3.7246 x 10 20 thou.Like any other scientific unit,the lightyear could also be in

fractions as well as multiples.Fractions of lightyear include millilightyear(1.0 x 10 -3 ly),microlightyear(1.0 x 10 -6 ly),and nanolightyear(1.0 x 10 -9 ly),while the multiples are kilolightyear(1000 ly),megalightyear(1.0 x 10 06 ly),and gigalightyear(1.0 x 10 09 ly).

Multiples of lightyears are more useful than the fractions,because the latter is restricted to only nearby stars.Other variations of lightyear in use by astronomers include lightmonth,

lighthour,lightminute,and lightsecond.

The origin of lightyear is rooted in the science of astronomy,as distances to the stars were first measured in 1938.In one of the measurements,Alpa Centauri,the closest star to the Sun,

was found to be 42 trillion kilometers away.This is a huge figure indeed.What if more distant bodies were to be measured? And really,astronomers need to.Eventually,what became obvious was the necessity for a new unit,with the ability to cope with large units.Over time,lightyear

became the unit of choice.It was obtained by considering the motion of light in a vacuum because the better part of the "Universe' space" is vacuum. Therefore,lightyear was specified to be equal to the distance travelled by light at the speed of light in a year,about 300,000,000 meters/second.In one normal year,there are 365 days.In one day,there are 24 hours,

and in one hour ,there are 60 minutes.With 60 seconds in one minute,a lightyear will give 365 x 24 x 60 x 60 x 300,000,000 meters,which is 9.4608 x 10 15 meters.

The Universe is so vast.It is 28 million lightyears wide. Many bodies are lightyears away from the Sun.The Local Group is 10 million lightyears wide.This group contains our own galaxy,"The Milky Way," which is believed to harbour over 350 billion stars,and is 100,000 lightyears wide.If one should come closer to our solar system,the Earth is 1.5789 x 10 -5 lightyears(or 15.789 microlightyears) away from the Sun.Again,from the Sun,Pluto,the largest planet is 6.3158 x 10 -3 lightyears(or 6.3158 millilightyears away).Indeed,the unit,lightyear,

has helped astronomer and man,to overcome the problem associated with handling large numbers emanating from dealing with both terrestrial and extra-terrestrial bodies.

Interpreting lightyear in the proper sense is beneficial as there are misconceptions out there about whether it is a unit of length or time.Like it has been established in this overview already,the lightyear is a unit of length.The year in the unit should not make one to feel otherwise.However,for example,if a celestial body is 850 lightyears away from the Sun,as obtained by an observer on August 4, 2008,the correct interpretation to the observation

is that the star (or whatever it is) is 8.0750 x 10 18 meters away.Again,the observer saw the star the way it was 850 years ago,exactly 1258 AD.But this analysis does not make lightyear a unit of time.

The future of lightyear is very much in the hand of astromers and of course man.The reason is not far-fetched.Research in the field of astronomy is growing daily,as astronomers are glued to their telescopes to watch distant celestial objects,and to offer man more information about our Universe.Whenever the figures come to be so large again,scientists may come together again to look for another alternative.For now,the "parsec," another unit of length,

used in astrophysics(a branch of astronomy that studies the physical properties of stars and other bodies),is more relevant to technical publications than otherwise.In use for over 100 years now,1 parsec is about 3.2616 lightyears.

On a final note,lightyear is strictly a unit of length,and not a unit of time.It has the value

of 9.5 x 10 15 meters.Eventhough not a fundamental unit of length,lightyear has carved a place for itself as the appropriate unit of length for measuring distant stars and galaxies.

And in a way,continuous research in the field of astronomy is making the unit even more relevant to the need of science.

Source

http://stars5.netfirms.com/situe.htm