Going the Distance

I did it! Yes, ladies and gentlemen, I did it! Perera gave us an equation in class and I solved it, right there while in my seat. Sure, I felt the pressure. I even felt like giving up, but no, Thomas is not a quitter. He tries until he can try no more. And guess what... that's right, he went the distance.

I know what you are thinking: "Ok Thomas, you can prove that astronomical distance varies with the two thirds power of time, so what?" Well my curious friend, this solution means nothing. It means nothing unless we know how far we are from stars and other systems. So, the class spent the day putting distance into perspective. In the following list, there are approximations for distance.

Earth's Diameter = 13,000 km

Distance Traveled by My Mom's Minivan 

(Happy Mom's Day!) = 150,000 km

Sun's Diameter = 1.4 million km

Distance from Earth to Sun = 1 Atomic Unit (AU) = 150 million km

1 Light Year = 9.5 trillion km

1 Parsec (pc) = 206,265 AU = 3.3 light years

Distance traveled by the light 

from the first time I flipped a switch = 160 trillion km

Distance to next galaxy = 700 kpc

Diameter of local group of galaxies = 1 Mpc = 1 million parsecs

Diameter of Virgo cluster = 17 Mpc

Diameter of Virgo supercluster = 50 Mpc

That means even light, moving at the universal speed limit, would take 165 million years to cross the supercluster which we call home. Beyond Virgo, there are ten thousand upon ten thousand (perhaps millions upon millions (or even billions upon billions (or... you get the story))) more superclusters spanning the universe.

Now you say, "Thomas, how do we know these distances?" It turns out that scientists have tape measures specifically designed for the task... No, really... One cosmologist gets into his spaceship and travels at the speed of light in one direction, and the cooler cosmologist gets into his bright red flying saucer littered with lightning decals and flies at the speed of light in the other direction (Boy you're gullible!). 

In reality, where I chose to live 2/3 of the time, it is not necessary to go the distance. Scientists develop methods where no traveling is necessary, except by the photons we receive. By observing the luminosity of cepheids, type 1a supernovae, or entire galaxies, we can determine the distance of these far off structures. It also helps to know a little trig if you are interested in determining diameters of large bodies.

So, the next time you are trying to "Go the Distance", remember there's likely a small particle which will travel through snow, heat, and galactic thunderstorms (Star Trek anyone?) for you, but no matter what, you'll be stuck doing the math.