It’s strange not seeing Ellie all summer. For two and a half months we don’t even email or talk on the phone. But I’m used to it. Her family has a vacation home in Colorado, and they also travel a lot—like, all over the world.

Sometimes I wonder if Ellie has an extra best friend in Aspen, like a spare tire. And sometimes I think that by the time we make it to June every year, we might just really need our long summer away from each other. With zero communication.

But today it’s the first day of school, and I see her in the hall outside the art room. Then she turns her head, and we snap together like magnets for a quick hug.

I jump right in, because with Ellie, it’s important to be the one who starts talking first.

“I’ve got to tell you something! At the end of August? I flew to Boston by myself to visit my grandfather, and he bought this really old building, and I—”

She grabs my arm. “That reminds me!”

And just like that, I know that my turn to talk is over.

“Because, in Aspen? Inside this Old West general store, there’s a jewelry shop, and they make things out of real gold nuggets—that’s all they do! Look at this bracelet. Isn’t it fantastic? My mom would die if she knew I wore it today, but I had to show you! And these sneakers? You’ll never guess where I got them—in Paris! My grandmother took me and my sister to all her favorite shops there, and it was wonderful! Such gorgeous things—you have to come for a sleepover! And on the way back to Colorado, we stayed in London for six days, and we went to this amazing store called Harrods, and I got the cutest…”

Ellie goes on for three more minutes, and her descriptions are funny and smart and charming and captivating—in other words, classic Ellie. But by the time she stops, I realize that I don’t want to tell her about my fantastic dusty boxes of buttons, from this gorgeous crumbling building where all the floors were covered with the cutest bird droppings.

And this is when I remember the Ellie Effect. Every summer I forget about this phenomenon, which always makes me ask myself the same question: If Ellie Emerson is my best friend, then how come she gets me so upset?

I’ve been trying to figure this out since second grade, and there does not appear to be a scientific explanation.

So each new school year, I get to study the Ellie Effect all over again.

One time Mom said, There’s an old saying: “Opposites attract.” I think that might be what’s going on with you and Ellie. In a lot of ways, this theory makes sense to me.

I don’t care much about clothes; Ellie cares a lot.

I love math and science; Ellie doesn’t.

I like to hike and camp and mess around outside; Ellie is perfectly happy to stay inside and talk…or go shopping. And honestly? Sometimes Ellie can be so much fun to be with that she can make me happy to hang out at the mall all day, too. Once in a while.

And those sneakers she got in Paris? I have to admit that they’re really cute.

The one way that we seem most alike? We’re both pretty—except I don’t try to be, and Ellie does.

If I ever said that out loud—that I thought I was pretty? Everyone would think I was totally conceited. But I’m not. I’m just trying to be scientific about something science can’t even define. There have to be a million different ideas about what makes someone good-looking. All I know for sure is this: Ellie is positive that she’s pretty, and she keeps on telling me that I am, too.

But I hate the idea that if she didn’t think I was pretty, then Ellie wouldn’t like me as much. It’s one theory I don’t want to prove.

The warning bell rings, and as we walk into homeroom, I remind myself for the hundredth time that even though Ellie Emerson is my best friend, Ellie’s opinions do not rule the world.

It only feels that way.