Juno, one of NASA’s spacecrafts, just passed Earth today on its way to its destination of Jupiter. Wait, if it launched from Earth, then how can it be passing the planet? The answer to this quandary relies on physics and a little ingenuity on NASA’s part.

NASA launched the Juno in August 2011 to study the giant gas planet in unprecedented detail. Astronomers plan for the space probe to make it to Jupiter on July 4, 2016.

The thing was, NASA used the Atlas 5 rocket to launch Juno, a rocket NASA officials knew would not be powerful enough to send the spaceprobe all the way to Jupiter.  So it sent Juno on what is called a looping trajectory, or “gravity assist.” The rocket sent Juno just beyond the orbit of Mars and as the probe returned toward Earth, Earth’s gravity will cause Juno to accelerate. Once Juno completes the flyby, it will reach speeds of about 87,000 mph.

“One of Juno’s activities during the Earth flyby will be to make a movie of the Earth-moon system that will be the first to show Earth spinning on its axis from a distance,” said principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio, Texas, in a statement.

The $1.1 billion Juno mission to Jupiter will to probe deep inside Jupiter using nine instruments. The object is to find glimpses of the planet’s structure, origin, atmosphere and magnetic field. The probe’s engineers must have had a bit of a romantic streak for naming it after the Roman wife of the god Jupiter who used special powers to learn the secrets Jupiter.

Those living near Cape Town, South Africa may have been able to catch a quick glimpse of the space probe as it traveled across the sky, though not with the naked eye. Using a telescope or maybe even a pair of binoculars would most likely enable anyone to see it.

“Juno will be really smoking as it passes Earth at a speed of about 25 miles per second relative to the sun. But it will need every bit of this speed to get to Jupiter for its July 4, 2016 capture into polar orbit about Jupiter,” said research scientist Bill Kurth of the University of Iowa, who is the lead investigator for two of Juno’s instruments. “The first half of its journey has been simply to set up this gravity assist with Earth.”