Grant Ernhart works with the U.S. Biathlon Team, so he spends a lot of time among snow-capped mountains. From the Canadian Rockies, he lobbed a question to Skunk Bear, NPR's science YouTube channel.

"I'm standing next to some mountains that are millions of years old," Ernhart said, "and the Earth is itself 4.5 billion years old. How do I even wrap my mind around that length of time?"

It's a tough question. A human life is so short compared to the life of the planet. But we decided the perfect place to tackle this problem of perspective was out on a football field.

Morgan State University in Baltimore, Md., let us take over its stadium one fall afternoon before practice, and we used the gridiron as a giant timeline. The distance between the end zones – 100 yards – would represent Earth's 4.5 billion-year history. Every inch was 1.3 million years. As we slowly marched down the field, traveling through time, we marked out the places that corresponded to the era when different sorts of creatures arrived on the scene — first simple cells, then fungus, fish, dinosaurs, mammals and, eventually, Homo sapiens.

We got the idea for this football field metaphor from Oregon State University professor Eric Kirby. You can listen to him describe the long history of the Rockies while taking a beautiful 360-degree tour of its peaks.

Just how close to the end zone do humans appear? Follow the 100-yard journey in our video at the top of this post to find out.

Got your own science-y question for us? Use this form to send it our way. We'll be answering questions from NPR's Skunk Bear community every other Tuesday.

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