What Would Happen If The Moon Disappeared?
The moon helps to stabilize Earth's axial tilt, which wobbles between 22 to 25 degrees. Without it, that wobble would become way more pronounced, and could increase its range to between 0 degrees (the Earth sitting "straight up") and 85 degrees (the Earth rotating on its side, like Uranus). This high variance in axial tilt affects any planet that doesn't have a large enough moon to stabilize it. Mars is one example, and its climate has undergone drastic changes with the shifts in its axial tilt.
from SciShow Space
Key Facts In This Video
Without the moon, tides on Earth would only be about 40% as large as they are now. (0:40)
The moon stabilizes Earth's axial tilt to between 22.1 and 24.5 degrees relative to the sun. (1:25)
Many scientists believe that before the moon existed, Earth rotated 3 to 4 times faster than it does today. (3:08)