Here Comes the Story: The Day We Walked to Neptune

Let's make the solar system fit in your neighborhood and actually understand just how mind-bogglingly empty space really is. What You'll Need:

• Sun: A basketball (about 9.5 inches across)
• Mercury: A peppercorn (tiny!)
• Venus: A large blueberry
• Earth: Another large blueberry (same size as Venus)
• Mars: A grape (smaller than Earth)
• Jupiter: A small cantaloupe (WAY bigger than everything else)
• Saturn: An orange (second biggest, but still smaller than Jupiter)
• Uranus: A plum
• Neptune: Another plum (same size as Uranus)

Also grab:

• Sticky notes or chalk to mark distances
• A measuring tape or a pedometer/phone to track distance
• A notebook to record your observations
• A friend or family member to help (trust me, you'll want company for the walk to Neptune)

And this is what happened..

"Mom says space is big," Maya announced at breakfast. "But how big is big?"

I looked up from my cereal. Maya was seven and asked approximately four million questions per day. This one, though, had an answer we could actually show her.

"Get your shoes," I said. "We're going on a field trip."

The Mission Begins

Twenty minutes later, we stood in the driveway with the weirdest collection of stuff our kitchen had ever produced: a basketball, various fruits, and a single peppercorn.

"We're making the solar system," I announced. "And we're going to walk it."

Dad raised an eyebrow. "The whole thing?"

"The whole thing."

I set the basketball down at the end of our driveway. Our Sun. The center of everything.

"If that basketball is the Sun," I explained, "then Mercury is fifty feet away and the size of a peppercorn."

Maya's eyes went wide. "That's tiny!"

"Exactly. Space is mostly empty. Ready to walk?"

The Inner Planets: That Wasn't So Bad

We counted out fifty feet down the sidewalk and placed the peppercorn.

"Mercury," I announced. "Hot enough to melt metal during the day, cold enough to freeze air at night."

Forty-three more feet. Venus—a blueberry.

Thirty-seven more feet. Earth—another blueberry. Maya held it like it was precious.

"This is us? Every person, every ocean, everything?"

"Everything."

Sixty-seven more feet. Mars—a grape at 197 feet total.

We could still see our basketball Sun from here. We'd walked maybe two minutes.

"Four planets," Dad said. "That wasn't so bad."

"Wait for it," I told him.

The Void

"Now we walk through the asteroid belt," I said. "Which is mostly nothing. Empty space for millions of miles."

We walked. And walked. And walked.

Maya counted her steps. Dad checked his email. I watched our neighborhood drift by.

Four blocks from home. 677 feet. I could barely see our driveway anymore.

I pulled out the cantaloupe.

"Whoa," Maya whispered.

Jupiter. Massive compared to everything we'd seen. Big enough to swallow all the other planets.

"And we're not even halfway to Neptune yet."

Dad groaned.

The Long Walk

Saturn was another two and a half blocks. We passed the coffee shop, the bus stop, three dog walkers.

Maya was tired. "How much farther?"

Nearly a quarter mile from home now. I placed the orange down and turned around. I couldn't see our basketball Sun anymore. Just houses and trees and distance.

"It feels lonely out here," Maya said quietly.

"Yeah. And we've got two more planets to go."

The Edge of Everything

Uranus took us almost half a mile. We were in a completely different neighborhood.

"I've never walked this far before," Maya said.

"Most people haven't. Not just to place a plum on the sidewalk."

Three-quarters of a mile to Neptune. Twenty minutes of walking. My feet hurt. Maya had complained seventeen times.

"Here," I said finally. "Neptune."

I placed the final plum on random grass near a house I'd never seen before, almost a mile from our Sun.

We stood there, breathing hard.

"That's it?" Maya asked.

"That's the eight planets. Pluto is another quarter-mile. The edge of the solar system? About a thousand miles away. We'd have to hike to Denver."

Maya sat down on the grass. "Space is stupid big."

The Walk Home

We turned around. Maya was quiet most of the way back.

At Jupiter: "So when astronauts go to the Moon..."

"They barely leave the driveway," I finished. "The Moon would be four inches from Earth. We haven't even left the front yard."

At Earth, Maya picked up her blueberry. "This is us. And Neptune is all the way back there."

"And we sent a probe there. Voyager 2. Took twelve years, traveling at 40,000 miles per hour. And it's still going."

We reached our basketball Sun in the driveway.

Maya picked it up. "It's so far away from everything. But its gravity still reaches Neptune?"

"That's how strong the Sun is. It holds everything in orbit even from a mile away in our model."

"Gravity is weird," Maya declared.

"Gravity is awesome," I corrected.

That Night

After dinner, we went outside in the dark. Dad pointed at the sky.

"That bright dot. That's Jupiter."

Maya stared. "We walked there today. Four blocks."

"And light from the Sun bounces off it and travels back to Earth—half a billion miles—so you can see it right now."

She was quiet for a long moment.

"Space is big and empty and lonely," she said finally. "But we're out there anyway. We sent robots to Neptune. We're trying."

She paused.

"And if space is that big, and we're just a tiny blueberry... maybe there are other blueberries out there. With other people looking up, wondering the same things."

"Maybe there are," Dad said.

"Do you think they've walked to their Neptune?"

"I hope so," I said. "I really hope so."

The Next Morning

Maya came down with her notebook.

"I'm making a list of all the places I want to visit. Mars first. Then Europa—Jupiter's moon with the ocean under ice. Then Neptune, because we walked there yesterday."

Mom smiled. "That's ambitious."

"Well," Maya said, "if we can walk to Neptune in twenty minutes, maybe someday we can fly there too. It'll just take longer."

I caught Dad's eye. He was grinning.

"Yesterday morning, space was just big and far away," he said. "Now she wants to visit Neptune."

"That's what happens when you walk the solar system," I said. "It stops being abstract. It becomes real. Still big. Still far. But possible."

I looked at Maya, scribbling mission plans in her notebook.

"Think she'll really go someday?"

"Yeah," I said. "I think she might."

So here's your challenge: Grab a basketball, some fruit, and someone willing to walk. Build your own solar system. Walk to Neptune.

It'll change how you see the night sky forever.