NASA’s Voyager 1 spacecraft is on track to set another historic record as its mission approaches the half-century mark. On Nov. 18 at 5:16 a.m. ET, the probe will reach a distance of one light-day from Earth, a journey of nearly five decades that places it farther from our planet than any human-made object in history.

It’s quite an accomplishment for a spacecraft built in the mid-1970s One light-day is the distance that l ight travels in a single day at the speed of light, which is approximately 186,282 miles per second. That translates to 25.9 billion kilometers or about 16.1 billion miles in a single day. At an average human walking speed of 3 mph, it would take a human 612,015 years to walk that distance.

Fortunately, Voyager 1 has been traveling a bit faster than that. It currently zips along the cosmos at a steady 37,763 mph, a speed it achieved in 1980 after a gravity-assisted Saturn flyby.…