Why is the earth unique? Some body may say that we have water on the earth. But all know that there is water on the Jupiter. And just stop thinking about this question. You may never know that the reason why the earth is unique is because of the moon. But you may ask that other planets also have satellites. But in the solar system only the moon is an exception. Its volume and weight is 25 percent and one in eighty of the earth. And the moon is so close to the earth.
First if without of moon we may know little about the universe. And it provides us with the earliest timing management tool. And about 2300 years ago Aristarchos of Greek proved that the earth is a spherical object via the research of eclipses. He also calculated the size of the moon and its distance from the earth. Also we know other things about the universe via the moon.
And if there is no moon we will see nothing after sunset and there will be no mammals on the earth.
Without moon each day will become very short and the earth would spin very fast. Also without moon there would be no seasons and even complex life.
And the water in the sea would not be salty and there may be no life without the moon. Last if without moon there may be no mountains and there would be no stable land.