The speed of light, the term "light year", and reference frames. Hi everyone. This is my first post, and I post out of desperation. A friend of mine and I were casually discussing Time Dilation, interstellar travel, etc. when we came to a point we fundamentally disagreed upon. Neither of us being a physicist it's a fundamental disagreement on what is accepted as truth in the physics community and nothing more. The term light year (I'm going to go ahead and get this out of the way so noone feels the need to state the plainly obvious in a response) is a measurement of distance. That's great. As I understand it, the distance that light would travel in one year of time. Having said this, here is the root of our disagreement. We were discussing Kepler 2B and the excitement generated by it. The planet exists roughly 352 light years away from Earth if I read correctly, so naturally I state that as exciting as the prospect is, ever getting there would be impractical. Travelling at the speed of light, it would still take 352 years to arrive there. His rebuttal is that it wouldn't take 352 years to arrive due to Time Dilation. Again I'm not a physicist, but I am familiar with the documented effects of Time Dilation. The question seemed to rightly come down to frames of reference. But from what frame of reference is the term "light year" taken? If you were riding on a light beam would it take you 352 years to arrive at Kepler 2B, or would that be what a relatively stationary observer on Earth would perceive? How much time would the traveler note had passed? I would assume that the term "light year" indicates a year of time passing in the reference frame of light (YES I KNOW IT'S A MEASURE OF DISTANCE PLEASE GOD), but as I think about it, I can see his point as well. The problem is that no matter how much we researched it, it's difficult to find a source that very solidly states "the distance of a light year is covered in X time from light's perspective and Y time from a relatively stationary frame". I have looked for an answer but I can find none. So can someone clearly state the matter? Also, understand that I'm trying to avoid theoretical proclivities that would render the argument moot on the grounds that from light's frame of reference the trip would be instantaneous, or would take an infinite amount of time, or undefined time. We really have no experience from which to draw what would seem to be errant conclusions, so if we really must, let's assume the speed of travel to be .99C. Thanks in advance for the answer.