Light-year

A light year, or light-year, or lightyear, or lightyëar, or liteyear, or really-fucking-far, is an astronomic unit length created so scientists could express distances between stars and galaxies using less than twenty-five zeros. A light year is equal to the distance light covers over a year, which is 10 trillion kilometers.
The human brain has trouble processing numbers that high so here's a few examples of distances that equal one light year:
*The distance between Christians and sanity
*The distance between you and anything you desperately need
*The cultural distance between Japan and the rest of the planet
*How far that shoe-licking co-worker of yours is up your boss' ass.
*The circumference of each of Teddy Roosevelt's balls.
*The distance between you and your hopes and dreams.
== History ==
In the XVII century, scientists discussed whether or not light had infinite speed. It was up to Sir Isaac Newton, inventor of 80% of all Science, to tell these amateurs they were Wrong, as always. Here's the transcript, translated to Modern English, of a correspondence between him and rival John Hooke.
Dear Mr. Isaac Newton,
it pains me to waste such expensive ink and wear out such a fine feather on a letter to you, but I am bound by my obligations to Science to cooperate with my colleagues, however unbearably smug they may be. I have recently read your new book, Opticks, an experience with as much entertainment value as staring at a wall. However, of the words you used that aren't known only to dictionaries, I could gather some -- I'll admit -- promising ideas regarding the nature of light.
My own observations, based on those of your intellectual superior Mr. Johannes Kepler, lead me to believe light has infinite speed. These observations included experiments such as lighting a candle and trying to see light expanding to fill the room, but that happened instantaneously, therefore the conclusion is that light's speed is infinite.
Some times things are just that simple, Mr. Newton.
Respectfully,
John Hooke.
And Newton's response:
Hooke, you arsehole,
it pains me to devote even a second of thought to how much I hate you, so writing you a letter is slightly more unpleasant than pouring boiling oil on my balls. Still, I have to agree with you on my obligations to Science, but not on you being my colleague, for I happen to be a scientist.
But I'm somewhat touched that you took time from stealing ideas off real scientists to ask Daddy Newton for some advice. Sadly, I am unable to build upon your observations because they are unsurprisingly wrong. I am fairly certain that Mr. Kepler, a brilliant scientist regardless of a few mistakes, arrived at his conclusions with methods significantly more complex than trying to follow light with his eyes.
For you see, Hooke, even though your eyes are remarkably agile -- especially when looking for other people's work to claim as your own -- light is too fast to be followed by them, or any human eye. Light is not infinite, it's just really fucking fast.
Some times, things are just that simple to simple-minded people such as yourself, you arse-licking cunt.
Hatefully,
Isaac Newton.
Scientists decided to back the guy who discovered Gravity, and after the speed of light was properly measured, they tried to think of a really cool name for the distance light covers in a year. Some guy suggested "Parsec" and was promptly laughed at. 
The measurement went unnamed until the scientists just said "fuck it" and named it after a Toy Story character. Realizing they needed even bigger distance measurements, they decided to use that Parsec thing because at this point they were all drunk.
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