Their inspiration is a phenomenon that astronomers have noticed with Jupiter. Every now and again, the gas giant captures a nearby object, which hangs around for a few years and then wanders off into space.
A good example is the comet Oterma which went into orbit about Jupiter in1936 before heading off into the Solar System two years later.
Could a similar thing happen to Earth, ask Baoyin and co. Having studied the orbits of the 6000 known near Earth objects (NEO), they say the short answer is no. None of them will come close enough for Earth to capture.