# Question between friends! - How long to travel 1 light year?

Question between friends! -- How long to travel 1 light year?

## Homework Statement

Me and a few friends were trying to work out how long it would take a human to travel one light year. We were using the these variables.

Distance = 9.4605284 × 1015 m

Fastest speed for manned space travel = 39,846 kph or 11068.3 m/s

## Homework Equations

I was using the equation of speed = distance/time, rearranged to solve for time. T = D/S

## The Attempt at a Solution

My attempt brought me back the answer of 27084 years.

I was doing this.

9.46 x 1015 =854716299241 seconds or 27084 years
11068 m/s

If there is any other variables I have left out, could you please write back. Me and my friends have used different speeds, different units and our heads are now fried!!!

Thank you

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PhanthomJay
Homework Helper
Gold Member

Gold Member
Did your friends get the same answer?If you are rounding the numbers,then you would get different answers.Your conversion of seconds to years is wrong!

Your absolutely correct for the seconds to years conversion! Last time i'll ever use Google as a calculator!

New answer is 27102.876054065195 or 27103 years.

vela
Staff Emeritus
Homework Helper
Actually, Google's answer is fine. The length of the year is approximately 365.24 days.

In any case, since you rounded off the distance to only three sig figs in the beginning, your final answer is only good to two or three sig figs as well. So answers like 27084 years or 27103 years are not really correct because the last two digits aren't significant.

Andrew Mason
Homework Helper
Your absolutely correct for the seconds to years conversion! Last time i'll ever use Google as a calculator!

New answer is 27102.876054065195 or 27103 years.
There are 365.25*24*3600 = 3.15576 x 107 seconds in a year.

The speed of light is 2.99792458x108 m/sec

So there are 2.99792458x108 x 3.15576 x 107 = 9.4607 x 1015 metres or 9.4607 x 1012 km in a light year.

If the spaceship can travel 11.068 km/sec. then in 3.15576 x 107 seconds it can travel 3.8659 x 108 km.

So it would take: 9.4607 x 1012 /3.8659 x 108 = 2.4472 x 104 = 24,472 years to make the journey.

AM