var earth = [[], []];
earth[0].push(3);
earth[0].push(5);
earth[0].push(7);
earth[0].push(9);
earth[1].push(13);
earth[1].push(15);
earth[1].push(17);
earth[1].push(19);
earth[1].push(21);
console.log(earth[0].length);
console.log(earth[1].length);
console.log(earth[1][0]);