what does light years mean?
Depends how far away the star is. If it is close (the closest is Alpha Centauri), then it can take as little as 4 years. It can take hundreds of millions of years, for the far-distant stars. The light from the sun takes something like 8 minutes to get to the Earth. A light year is the distance that light travels in a year. (I don't know the actual number of km or miles.)
Don't they teach anything in school anymore? A light year is the distance that light travels in one year. The time it takes for the light from a star (or any object) to reach your eye depends on how far away the object is.
Stars are in different distances from us. Some of them are nearer and some of them are farther. The more distant the star is the longer it takes for it's light to be seen from the earth. Light year means the distance that light can travel in one year. So do not get confused. Light year has nothing to do with time; it is a unite of distance. Some stars are many light years away from us that it takes a lot of time for their light to reach us, and that's why new stars are being found even today. The amazing part is that sometimes astronomers find a star that they say it might have died now, because we are getting a light that was sent out billions of years ago! In fact our science of astronomy is about past! It means that we are observing the past life of a star and other objects. An example could be that if some people would look at the Earth from a very object distance in universe it is possible that they would see dinosaurs because the light from the Earth had traveled billions of years to reach them!
Distance(miles) light travels [in a vacuum]... per second:186,000 per minute: 11,160,000 per hour: 669,600,000 per day: 16,070,400,000 per year: 5,865,696,000,000or 5Trillion, 865Billion,696Million miles Now why you want to know that distance is beyond me since very very very few people can truly grasp the sheer immensity of those numbers and distances. I can talk about and throw around those numbers all day, but I can't truly put them into perspective. They're just too huge. I mean, what's the longest trip you've ever made...a thousand miles or maybe two thousand even? that is nothing compared to cosmic distances. Anyway, it takes time for light to travel anywhere, just like anything else. So, depending upon how far away a star is, it took that long for the light hitting your eyeballs to get here from the star. Alpha Proxima is 4.5 light years away. When you look at it, the photons hitting your eye left that star 4.5 years ago. Something to think about: You're not even seeing the star where it is. In those intervening 4.5 years, it moved and so has the earth. So, what you are REALLY seeing is a photon that was sent from its THEN position in a direction that ended up intersecting with the earth's NOW position. But, it's all perfectly okay in a relative way.
The time to see a star's light depends on how far away it is. A light year is the distance light travels in one earth year. Since light travels at 186,000 miles in a second and there are 31,536,000 seconds in a year, light travels 5,865,696,000,000 miles in one year. The closest star besides our sun is 4.4 light years away. That means the light you see from that star is 4.4 years old.
