If light travels at 186,000 miles per hour and a star is 75,000 light years away how long would it take for the light from the star to reach us. And how long would it take for a flight to it. Also could you provide formula to your solution.

I'll give you some hints to your problem, but I won't solve your exact problem. I hope that's okay. By the way, light travels at 186,000 miles per SECOND, not per hour.

First of all, a light-year is the distance light travels in one year. The star Alpha Centauri is about 4 light-years away, so light from Alpha Centauri takes 4 years to get to the Earth.

Now, if we wanted to travel to Alpha Centauri, we would have to know how fast our spaceship is travelling. The fastest rockets move at about 20,000 mph. Suppose we launch one at 20,000 miles per hour toward Alpha Centauri. How long would it take to get there?

Well, distance travelled equals speed times time, so the time it takes to travel a distance is that distance divided by the speed, or

4 light-years / (20,000 miles / hour)

Now this isn't terribly illuminating. We need to convert units so that we can do the division. There are 6 trillion miles in a light-year (approximately), so the distance we need to go is 6 trillion miles / light-year times 4 light-years, or 24 trillion miles. So, this trip would take 1.2 billion hours. There are 24 hours a day and 365.25 days per year, so this time in years is 137 thousand years.

That's a long time! Now you can start to see while it is virtually impossible to visit other stars - even the closest star would take hundreds of thousands of years to reach!

Thanks for writing, Kurtis Williams

how_long_would_it_take_us_to_travel_to_alpha_centauri.txt · Last modified: 2009/02/02 13:16 by czars · [Old revisions]