# How to Calculate Time Required for 11 Light Years @ 0.9c

In summary, the conversation discusses the time it would take for a spacecraft traveling at 0.9c to reach a planet that is 11 light years away. The formula for time = distance / speed is mentioned and the importance of using the correct frame of reference is emphasized.

You are in a spacecraft that is traveling at 0.9c (according to the passenger), and you want to get to a planet that is 11 light years away. How long will it take to get to the planet ?

This may seem like a simple problem but it's been bugging me. I answered this question by using the simple time = distance / speed since the person is in the same frame of reference as the space craft, is this correct?

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Hi doc.madani! You are in a spacecraft that is traveling at 0.9c (according to the passenger), and you want to get to a planet that is 11 light years away. How long will it take to get to the planet ?

The question isn't clear …

according to the passenger, the speed of the spacecraft is zero. I'll guess it means, if the speed and distance as measured by a stationary observer are 09.c and 11 l-y, then how long on the passenger's clock does it take?

I was just quoting the exact question that I was given In a test :s however since the passenger is in the same frame of reference (inertial frame if reference) to the spacecraft you can simply use the time = distance over speed formula ?

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Yes, but if he got the 11 light-years from a standard Galactic Maritime Federation astro-chart (sorry, I don't have a link ), that'll be the distance in a stationary frame, and you need the distance in his frame. Ok for arguments sake let's say it was 11 light years in his frame of reference :) your starting to scare me that there's more to the question than I anticipated :s lol that's ok

If it was 11 light years in his frame of reference, then yes, he can divide by the speed to get the time on his clock. 