The Weight Of The World

Every morning, I drop my two oldest sons off at school.  Each day there is the same drama – they are slow to get ready and out the door, they complain of the cold, they gripe about the size of my truck and its narrow bench seat and how squished they are and having to hold their heavy book bags on their laps…

Once they settle in, though, the short ten-minute ride to school is occasionally the highlight of my day.  I listen as my boys make inappropriate jokes and comments.  I marvel at the sharp observations they make about the people and things they see and how the things I know as truth are filtered through their new eyes. 
Today I had the radio on in the background.  I’m not sure if it was NPR or some AM news show, but there was talking so… one or the other.  I was spacing out in my driving fog, when my oldest son asked me “Dad? How did they weigh the whole Earth?”

“What?”

”The guy on the radio just said how much the Earth weighs and I don’t know how they did it.”
At first I started thinking about the logistics of such an endeavor: Would you use some sort of hoist?  Where would you put the straps so as to minimize loss of life and property damage?  Would some giant simply pinch our little blue planet and set it down on a scale?

My head was spinning now… If the Earth was brought into a room where it had external weight, wouldn’t the oceans drain all over the floor?  Wouldn’t the people fall off?

Holy shit – wait a second: “weight” is a function of the amount of gravity the celestial object on which you are standing is creating.  Do you calculate the weight of the Earth by the estimated gravity of a hypothetical planet large enough to house beings capable of performing this exercise in measurement?  Because you can’t use the Earth’s own gravity, right?  You couldn’t put a scale on another planet the size of Earth and set the Earth on it.  And you can’t just measure a planet and base its weight on its own gravitational rate.  That would be like trying to put a ruler on someone’s forehead to calculate how intelligent they are.  Or using waist size as an estimate on a person’s capacity for empathy.
 
“They’re scientists,” I answered my son. “They have ways of doing these things.  They probably used a computer model.”

We pulled into the school parking lot.  My youngest son struggled to release his seatbelt and open my heavy truck door.  Then, with a quick “I love you guys. Have a great day!” they got out and stepped into the stream of children headed in for a day of learning a few new things.