Just how big is Earth? Let’s make some reasonable assumptions to get a rough estimate. Suppose that you could walk all the way around the world, approximately 25,000 miles, and that there are no oceans, mountains, etc. blocking your way.

A moderate walking speed is three miles per hour. If you walk eight hours a day, seven days a week, that’s 3 × 8 × 7 = 168 miles a week. Times 52 weeks per year is 8,736 miles a week. 25,000 / 8,736 is 2.8 years. (If you take off weekends, it’s about 4 years. If you skip sleeping and walk 24 hours a day, it’s just under one year.)

Our planet seems so huge. But only about three years to walk all the way around it? It’s not nearly as big as we think… in fact, it’s pretty small. That’s why it’s pretty easy for seven billion people to pollute it or damage it.

Just three years around at walking speed.