When it eventually does catch up , Cruithne will make a series of annual close approaches to the Earth and gravitationally exchange orbital energy with Earth ; this will alter Cruithne 's orbit by a little over half a million kilometres so that its period of revolution around the Sun will then become slightly more than a year . When it eventually does catch up , Cruithne will make a series of annual close approaches to the Earth and gravitationally exchange orbital energy with Earth ; this will alter Cruithne 's orbit by a little over half a million kilometres ( whilst Earth 's orbit is altered by about 1.3 c ) so that its period of revolution around the Sun will then become slightly more than a year .