Setting: Emon, Markus, Yesinia, and Kaitlyn meet Haitham at his locker. He’s been upset since second period.
Emon: Why are you so frustrated with Ms. Phan in science class, Haitham?
Haitham: She keeps telling me, “Don’t forget your units!” “It’s wrong without units!” I lost points on my last lab report. She thinks I know what she means, but I don’t. I looked “unit” up in my dictionary and there are 17 different definitions! For one stupid word!
Markus: You carry that dictionary in your backpack? How heavy is that thing?
Haitham: Not the point.
Kaitlyn: Seventeen entries? That’s interesting. It’s a pretty simple word, I would say.
Haitham: (glaring) I would respectfully disagree.
Yesinia: Haitham, is one of the definitions “book chapter”? My science text has a unit on evolution, a units on microorganisms, a unit on—
Markus: (interrupting) Hey, and my cousin at UMass gets three or four units for each of her college courses.
Emon: And Ms. Schultz says our marching band performs like a single unit. I think she means the band is a group that marches in step like one person.
Haitham: Whoa! I know you’re trying to help, but all I need to know is what my science teacher means by unit.
Kaitlyn: Well, I think we’re on the right track—a unit probably means one of something, because "uni" means one. A unicycle is like a bicycle, but it just has one wheel.
Haitham: What? So Ms. Phan wants me to write one of something all over my papers? One of WHAT?
Kaitlyn: No, no. Think about it. A unit is more like a thing you use when you measure.
Haitham: Are you talking about measuring things in pounds or inches?
Kaitlyn: You got it now. A unit can be a weight or a distance or time. We measure lots of quantities. And to make sense to everyone, every measurement needs a unit. It doesn’t make sense to say the length of the field is 200. You have to say 200 feet, meters, or whatever unit you are using.
Haitham: Oh, that’s all? Okay, now I get it. I’ve been writing ratios on my paper like 60 per 1. The numbers needed units: 60 miles per 1 hour.
Markus: Right, if you don’t write the units, nobody knows what you’re talking about. (thinking) Say I told you that I drank two sodas at lunch.
Yesinia: Your teeth are gonna rot.
Markus: Not the point. What I’m saying is that you don’t know if I drank two liters, two 12-ounce cans, or two tiny cups! It really doesn’t mean anything unless you know the units.
Emon: The volume of a two-liter bottle is way more than two soda cans.
Markus: You’re right about that, Emon, but wrong about something else. What I think you mean is capacity. The capacity of a two-liter bottle is more than two soda cans because the bottle can hold more.
Haitham: That reminds me that Coach Frassetto said the other day that the length of the football field was 100 yards. And then he said the distance to the goalpost was 25 yards. I was wondering, why did he say length and then say distance when both are yards?
Kaitlyn: Good catch. The length often means the longest side of an object. The football field has a long side, the length, and a width, the short side. A distance is the measurement between two things or points.
Emon: We totally use length and distance for each other all the time. Probably doesn’t matter that much.
Markus: There are lots of ways these words get used, like the length of time to finish your report or going the distance for the team.
Kaitlyn: All right, here is a challenge. Another pair of units that are really similar is weight and mass. Most people think they are the same. Any of you guys know the difference?
Yesinia: Okay, I think I know this. Every night after eating a bowl of ice cream my dad weighs himself. He’s measuring how heavy he is, like last night he was 210 pounds. But our science book never says weight, it says mass. Mass is the quantity of material, or matter, like my dad and his bowl of spumoni.
Kaitlyn: That’s right. Weight also has to do with quantity of matter, but weight changes according to the strength of gravity. Mass doesn’t.
Markus: Nice. The gravity on the moon is about one- sixth of the earth. So if your father moves to the moon, he’d weigh 35 pounds.
Emon: That’s pretty funny. But this time, you’re the one who is only half right. Technically speaking, pound is a unit used for mass, not weight.
Haitham: For real? When I say that I weigh 103 pounds, I should really be saying my mass is 103 pounds?
Emon: That’s right. But it does sound kind of nerdy.
Markus: Then what is the right unit for weight?
Markus: You’re totally making that up.
Emon: No, Isaac Newton “discovered” gravity, and since weight units have to do with gravity, they are named after him.
Kaitlyn: People can just name units after themselves?
Emon: Well, it helps if you are a king or something. Last year in Ancient Civilization class, I read that the Egyptian pyramids were measured by a royal cubit that was equal to the forearm of an Egyptian pharaoh. So the pharaoh could just establish the standard measurement.
Yesinia: Hey, if a king can name a length unit after his arm, so can we. I hereby declare one “schnoz” to equal the length of Markus’ nose.