The Moon’s gravity creates tidal bulges on Earth. As Earth rotates, these bulges move. This causes high and low tides. The Sun also contributes but less strongly. Without the Moon, tides would be much weaker. Marine ecosystems depend on this rhythm.
This matters because tides influence life. Coastal species evolved with them. Human navigation relied on tides for centuries.
It also affects Earth’s rotation. Tidal friction slows Earth down. Time itself is impacted.
Without the Moon, Earth’s tides would be about one-third as strong.
[NOAA, noaa.gov]