# Insanely Large Numbers

I was reading A Walk through the Heavens on Saturday and after reading for a while, I started doing some calculations.

First, light travels through a vacuum at 186,282.397 miles per second. That works out to 670,616,629.2 miles per hour, which is 16,094,799,100.8 miles per day, which is 5,878,625,371,567.2 miles per year. That’s 5.8 trillion miles in a year. That’s really fast.

Now, the book went on to say that besides our sun, the nearest star to us is Alpha Centauri at a distance of 4.37 light-years. That works out to 25,689,592,873,748.7 miles from Earth. So, our “nearest” star is roughly 25 trillion miles away from us.

Feeling small? No? OK, try this. Our solar system is located in one arm of our galaxy. The center of our galaxy, according to the book, is about 30,000 light-years away from us. That means that we are about 176,358,761,147,010,000 miles away from the center of the Milky Way. That’s 176 quadrillion miles away.

Still comprehending the numbers? The latest issue of Astronomy Magazine has an article about a collision of 4 galaxies that has been spotted that is 5 billion light-years away. That works out to 29,393,126,857,835,000,000,000 miles away. That’s 29 sextillion miles away.

On Sunday I was watching a program about a manned mission to Mars, and it got me thinking about these huge distances again and how long it would take to traverse them in a spacecraft. From what I can tell, the fastest manned spacecraft so far has moved at around 27,000 miles per hour. I found an article from 2006 about a prototype that was purported to travel at 36,000 mph. But let’s use the 27,000 mph figure. At that speed, assuming it stays constant, the craft could travel 236,682,000 miles in a year. At that speed, to go just one light-year would take 24,837 years. To get to the places I mentioned earlier would take

• Alpha Centauri: 108,540 years
• Milky Way center: 745,129,588 years
• Galaxy collision: 124,188,264,666,666 years

And some humans think we are alone in this vast, great expanse of space.

Note: The numbers I used for the speed of light and the distance to Alpha Centauri are different from what is in the book. I found more accurate values for these on WikiPedia, so I used those. It only changes the calculations by a few billion miles… Also, please note that I’m no mathematician, and some of these calculations may not be completely accurate. I did the best I could.