The moon's mass is 7.35 x 10^22 kg, about 1.2 percent of Earth's mass. Put another way, Earth weighs 81 times more than the moon. If the Earth were hollow, about 50 moons would fit inside. Australia's diameter is 600km wider than the moon's. The moon sits at 3400km in diameter, while Australia's diameter from east to west is almost 4000km. it would take about 91 days to walk the 6,786-mile (10,921 km) circumference of the moon.