What is a Light Year?

Question: What are light years and what is the speed of light?

Answer: Contrary to what many people might think, a light year is a unit of distance and not time.

So what is a light year?

A light year is simply the distance light will travel in a year, it is of course traveling at the speed of light which is 186,282 miles per second or 670,616,629 mph.

To give you some idea of just how fast that is, if you were traveling at the speed of light you could move right around the Earth seven and a half times in one second, basically so fast that everything would be a complete blur.

It is believed to be impossible for anything to travel faster than the speed of light.

A light year is about 5.88 trillion miles, a distance so large it is almost impossible to comprehend. However is the context of the universe this distance is virtually nothing.

It is due to the sheer enormous size of space that measurements of distance we use here on earth such as kilometers and miles are impractical, and light years are used instead.

As an example, the closest star to planet Earth not counting the Sun is Alpha Centauri which is 4.4 light years from us and yes that’s the closest. This means that the light that reaches your eyes when you look at it in the night sky left the star 4.4 years ago so you are seeing as it looked then, your effectively looking back in time.

The nearest galaxy to our own Milyway is Andromeda which is about 2.5 million lights years from us so you see that as it was two and a half million years ago.

So if someone living in the Andromeda galaxy is looking at the Earth through a super powerful telescope they will see no sign of human life as we have only been around for approximately 200,000 years.

Giving these facts you would believe that even if we develop the ability to travel at light speed it would still take far too long to make visiting distant stars and galaxy’s possible, but there may be a loophole.

Physicists know that the closer you get to the speed of light, the more time slows down and it’s believed that once you reach light speed time actually stops. Therefore for the person or people moving at this speed you will appear to reach your destination (no matter how far away) instantly and they wouldn’t have aged at all despite perhaps millions of years going by.

The down side is if you left earth going at the speed of light, visited Andromeda for the day then traveled back, about five million years will have still gone by on Earth. Therefore the planet and the people living there would have changed dramatically since you left the “day” before.

So basically if humans ever develop the technology to travel that fast we could in theory travel anywhere in the universe, the challenge is creating that tech. The thing is the faster you get, the more power you need to continue accelerating.

One other interesting fact, if you were traveling at the speed of light you couldn’t then move your hand out in front of you as that hand would then be moving faster than light speed and thus be breaking the laws of physics. Therefore when you are moving that fast you would have no forward dimension.

Share on Google+Tweet about this on TwitterShare on Facebook