Mass because the bigger the mass the larger gravity (gravity on earth bigger than the moon and the sun's gravity is larger than the earths) and distance becuase the further you are away from the earth or moon or sun the lower the affect of gravity is... which is why astronauts are weightless in space.
Western Australia is the largest state in the world. Western Australia is the largest state in the world.
The largest country in the world today is, of course, China, which is one of only two countries with a population of more than a billion people. To give you an indication of scale, with 1.36 billion people, China today has four times as many people as the United States of America.