'The dimensions of the Cosmos are so large that using familiar units of distance, such as miles or meters, chosen for their utility on Earth, would make little sense. Instead, we measure distance with the speed of light. In one second a beam of light travels 186,000 miles, nearly 300,000 kilometers or seven times around the Earth. In eight minutes it will travel from the Sun to the Earth. We can say that the Sun is eight light-minutes away. In a year, it crosses nearly six-trillion miles of intervening space. That unit of length, the distance light goes in a year, is called a light-year. It measures not time but distances- enourmous distances'

   To contemplate traveling to Alpha Centauri, consider this:

   There are 31,536,000 seconds in a year, and a light-year is the distance light travels for one year at 186,000 miles per second. If one multiplies 31,536,000 by 186,000 you would arrive at 194,892,380,000 - the distance light travels in one year.

   As we know, Alpha Centauri is 4.3 light-years away; so, if one multiplies 194,892,380,000 by 4.3 you would arrive at 7,854,437,234,000 miles- the distance to Alpha Centauri. If one were to travel 7,854,437,234,000 miles at 200 miles per hour, it would take 39,272,186,120 hours to arrive there. Considering that there are 24 hours in a day, it would take you 1,636,341,088 days, traveling at 200 miles per hour to reach Alpha Centauri.

   Let's say you live to be seventy-four years old (longer than most humas live according to world-wide statistics). At seventy-four, you will have lived 27,010 days.