Question

The speed of light is about $2\times {10}^5$ miles per second. The star Alpha Centauri is approximately $2.5\times {10}^{13}$ miles from Earth. How many seconds does it take light to travel between Alpha Centauri and Earth?

Answer 1

Speed of light $=2\times {10}^5$ miles per second
Distance of the star Alpha Centauri from Earth $=2.5\times {10}^{13}$ miles
Time taken to travel between Alpha Centauri and Earth $=\frac{Distance}{Speed}$$=\frac{2.5\times {10}^{13}}{2\times {10}^5}$$=1.25\times {10}^8$ sec