Radio and TV transmissions are being emit- ted into space, so Star Trek episodes are streaming out into the universe. The near- est star is 2 × 1017 m meters away.
If civilized life exists on a planet near this star, how long will they have to wait for the next episode?
Answer in units of years.
perhaps you mean 2 * 10^17 meters
speed of electromagnetic wave in space = about 3 * 10^8 m/s
so
2 * 10^17 meters = 3 * 10^8 meters/second * t seconds
so
so t = (2/3) * 10 ^9 seconds = 6.667 * 10^8 seconds
6667 * 10^5 s * 1 hr /3600 s = 1.852 * 10^5 hours = 185.2*10^3 hr
* 1 day / 24 hr = 7.72 * 10^3 days = 7720 days
7720 days * 1 year/365 days= 21.2 years