She's doing a planets project, writing a report and building a model of the Earth. She's in third grade now, supposed to do it all on her own, no parental assistance allowed, but as she works so diligently, forming an orange-sized Earth out of modeling clay, painting the inside of a cardboard banker's box black, dabbing in white dots for stars, then hanging her model Earth inside the box with fishing line so that it appears to levitate in space, I ask her whether she's considered adding the Moon.
She has. But how big would it need to be? We look it up. The Moon is a little less than one-fourth the size of the Earth. Measuring, we determine that her orange-sized Earth has a four inch diameter. If she makes her Moon to scale, it would have about a one inch diameter. Sticking with the fruit analogy, her Moon would be a strawberry next to her orange Earth.
Where should she hang her Moon? Can we fit it in my box, she wants to know, or should I have started with a bigger box? If Earth was the size of an orange, a strawberry Moon would be about 10 feet away. That's another six of these banker's boxes, side-by-side, or maybe you could fit them both in a really big refrigerator box.
She looks crestfallen.
Thinking fast, I ask her if she wanted to do the whole solar system, how big would her Sun be? With an Earth the size of an orange, her Sun would have a diameter of about 36 feet. That's a large hot air balloon!, she says, interested again. How far away would we have to hang my Sun? We look that up and figure that if an orange-sized Earth and its strawberry-sized Moon were 10 feet apart, the Earth and its hot air balloon-sized Sun would be 333 feet apart, or a little more than a football field away. That would have to be a huge box, she says, one that holds a 747 or something.
And what about Pluto? Pluto is about two-thirds the size of our strawberry Moon, so if we made a Pluto it would be the size of a large olive. And we'd have to hang it 2.5 miles away from our orange-sized Earth to keep everything in scale. She's laughing now, these distances are just so ridiculous.
And if you think our solar system is big, consider this: If you wanted to add the nearest star -- Proxima Centauri -- to your model, you'd have to hang it over 17,000 miles away from your orange-sized Earth. Her eyes are glazing over, so I stop.
Maybe someday I'll tell her that our Sun is just one of millions of stars in our galaxy, our galaxy just one of a hundred billion galaxies in the universe. Maybe I'll try to explain it to her by comparing the universe to a beach and our Sun to a grain of sand, except that there are many more suns than grains of sand and each grain would be separated by thousands of miles. And maybe I'll ask her to consider what that makes us, a speck on a speck in a speck of dust drifting through a cold black void of nothing.
Or as I watch her intently finishing her project, dabbing black paint over the remaining bare spots, her universe compressed into a cardboard banker's box, for now, I think maybe I won't.