What does a light year measure?

It is a unit of distance where the distance between the objects is extremely large, like between the stars and the planets. Normal units of distance will be cumbersome to measure these distances and hence these distances are measured in terms of the distance traveled by light going by the speed of 3x 10^8 meters per second. So when we say a particular star X is 9 light yrs away from another star Y, we mean it will take light 9 years to reach X from Y. In miles, one light year comes to around 6 trillion miles thereby making the distance between X and Y equal to 54 trillion miles.

More Info: en.wikipedia.org

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61 Comments

George Oliver Prince

Good explanation, of course, any Star Trek fan should have gotten this one

Rachel Connelly

This is an excellent explanation. Good work!

Gery Tillmanns

Id like to think I learned that in school but I tend to believe it was Star Trek.

sftcw

William Lyons, No. No and No. light year is a measure of distance.

William Laughlin

Vonda Summers, You don't have to be a fan of Star Trek to know what a light year is; just a student of a little bit of science.

Chris Brown

Do you know how to work out how far one light-year is? You multiply the speed of light (186,282mph (299,792.2422km/h) - per second by the number of seconds in one year. My maternal grandfather, who was born in London in 1862 and came to NZ as a teenager, later developed an interest in astronomy, later becoming one of this country's important pioneer scientists, along with people like Lord Sir Ernest Rutherford, hence my own interest, even though he died nearly 21 years before I was born.

Chris Brown

Did you know that the nearest star is close to one of the "pointers" to the Southern Cross? This is close to the second closest and innermost of the pointers, which is Alpha Centaurus, Said star is Proxima Centaurus which lies at an approximate distance of 4.2 light-years so that when we look at the night sky, we are looking into the past. Also, if we were able to travel close to the speed of light, time, relatively, would appear to slow down and if we were to travel faster time would appear to go backwards as in the rhyme, "There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on the previous night. - - A. H. Reginald Buller in Punch (19 December 1923): 591.

Jon Ilagan

Thanks! now I know how far is one lightyear

Chrissie

jack patti go, Pardon?

Chrissie

dlh, I learned it from Sheldon in The Big Bang Theory!

Chrissie

Ed Taber, "All hail, James Clerk Maxwell!"

ronwellings

Spc Kook Dude, No judgement, play the game any way you wish. I'm seriously curious. Why do you look up the correct answer before replying? What satisfaction/reward does the give you? Everyone is different. Why is looking up the answer first best for you?

Spc Kook Dude

One of my mates told me about this and then I found out it was true on Google.

Ashok Kumar

Nicely defined, but would have been better if only SI units were used and also if number of days in a year (365 or 365.25 or 366) were mentioned.

Spencer

Very well-written.

James Kaighin

“Star trekking, across the universe. . .”

Matt Wells

Missed a step in your math. And it is as much a measure of time (space travel is time travel) as space travel.

Luciele M Wilding

Bob Arbour, I believe you have missed a very important number in your calculations. Light travels at 186,000 mps. there are 60 in a minute, 60 minutes in a hour - the bit you missed out was hours in a day, 24, then multiply by 365. Giving a grand total of 5,865,696,000,000 BW