An artist's illustration of NASA's Voyager 1 spacecraft, the farthest human-built object from Earth, which launched in 1977 and is headed for interstellar space.

At this very moment NASA's Voyager 1 and 2, two spacecraft that left Earth in the 1970s, are exiting the solar system.

The two spacecraft are passing through the magnetic bubbles at its edge approximately 9 billion miles from Earth. Now, 9 billion miles is clearly far, far away, but it's also a pretty difficult distance to imagine. How about we put that into (somewhat) more practical terms.

Measured in cross-country flights, the distance to the edge of the solar system is great indeed. LAX and JFK airports are 2,475 miles (3,983 km) apart, so the Voyager probes have experienced the equivalent of three million to four million red-eyes.

One could also measure the distance they've gone in units of the Earth-moon separation. Our satellite orbits at an average distance of 238,857 miles (384,403 km). Line up 37,679 of those Earth-moon distances one after another, and you'll arrive at the edge of the solar system. [Video: Solar System's Border Lets Galactic Rays Through]

The Sun is close to 93 million miles (150 million km) away from us. The edge of the solar system — and those intrepid Voyagers — are almost 97 times farther afield.

This story was provided by Life's Little Mysteries, a sister site of SPACE.com. Follow Natalie Wolchover on Twitter @nattyover, then join Life's Little Mysteries on Facebook.