As observed on earth, a certain type of bacterium is known to double in number every 18 hours. Two cultures of these bacteria are prepared, each consisting initially of one bacterium. One culture is left on earth and the other placed on a rocket that travels at a speed of 0.968 c relative to the earth. At a time when the earthbound culture has grown to 64 bacteria, how many bacteria are in the culture on the rocket, according to an earth-based observer? (Round your answer to the nearest whole number)