Help me out: how can a "light year" be a unit of distance?

Misfoot wrote:

Fellas... is it PETS-MART or PET-SMART?

Good one. I always thought Pet-smart.

Do or do not. There is no try.

Well actually wrote:

Actually light is not a sentient being and cannot "try" to do anything.

flat space - don't involve BH into the discussion please.

troof be told wrote:

The other interesting thing is that a year itself is defined defined based on distance, the distance covered by the Earth going all the way around the sun. In other words, a light year is how far light goes in the same time goes it takes the Earth to go around the sun.

Wrong. A year is determined by the time it takes for the Earth to move around the sun, the distance is irrelevant. Your second sentence corrects the error you have made when you say "a light year is how far light goes in the same time" time in this instance being a year.

Stefan Hahking wrote:

the Earth to move around the sun, the distance is irrelevant.

I think you want to re-read what you just wrote there.

You need a better understanding of the English language and how to comprehend a sentence. By cutting that sentence in half it might make no sense but I think you should re-read the whole thing and then break it down. The subject is a year and how it is measured. I have proposed that a year is the TIME that it takes for the Earth to go around the sun, but the distance is irrelevant. If (and assume that we would exist in this case for arguments sake) the Earth's orbit were twice as large but it was moving around the sun twice as fast, the time that was a year would be the same but the distance that the Earth traveled would be twice as much. In this situation a light year is the same because the time of a year has not changed, however the distance the Earth travels in a year is completely different. Understand why distance is irrelevant?

Does it make a difference that light doesn't go in a straight line?

Time is a figment of your imagination. See brian clock thread.

What if our frames of reference are different - e.g., you witness/measure the light year on earth while I witness/measure it on Proxima Centauri (approx 4.3 light years away from earth)? Will we both measure different distances since time will pass differently for the two of us?

theory of confusativity wrote:

What if our frames of reference are different - e.g., you witness/measure the light year on earth while I witness/measure it on Proxima Centauri (approx 4.3 light years away from earth)? Will we both measure different distances since time will pass differently for the two of us?

Time is just a construct of the human mind. Time doesn't just stretch out in front of us- all times happen simultaneously. There is nothing in physics stating that time shouldn't be able to move backward as well as forward although humans only experience it moving forward.

what if the speed of light is found not to be the absolute speed limit for the universe? Will the light year need to be replaced as the standard unit of measurement for distance?

Actually, time is a measurement of change. There is no so-called time-line that one can travel on. Everything is in the moment, constantly changing. I can't be bothered to find references. Additionally, what states that time can't move backwards is the universal speed limit. If an object were able to travel faster than light, it would hypothetically go back in time, but it can't because light is the limit. Relativity and such.

Why would time pass differently?

theory of confusativity wrote:

What if our frames of reference are different - e.g., you witness/measure the light year on earth while I witness/measure it on Proxima Centauri (approx 4.3 light years away from earth)? Will we both measure different distances since time will pass differently for the two of us?