-то is a modal particle, it accentuates the word вся, emphathizes the size of the whole planet Instrumental case is often used when we talk about size размером с дом - the size of a house, as big as a house, of the size of a house размером с воробья - the size of a sparrow, as big as a sparrow, of the size of a sparrow величиной с Луну - as big as the Moon, the size of the Moon