When do low tides occur in relation to the moon and sun's positioning?

Low tides occur when the moon and sun are at right angles to each other, which is known as the first and third quarters of the lunar cycle. During these times, their gravitational forces counteract each other. The combined effect results in a lower tidal range, meaning that the high tides are not as high, and the low tides are not as low as they would be during periods of alignment.

This phenomenon is fundamentally explained by the gravitational interactions between the Earth, moon, and sun. When the moon and sun are aligned (as would be the case during new or full moons), their gravitational forces combine, leading to higher than normal high tides known as spring tides. Conversely, the right-angle positioning diminishes the overall gravitational pull on the Earth's water, contributing to the occurrence of low tides.

Understanding the dynamics of tidal patterns is essential in hydrographic surveying, as it affects the depth and navigability of coastal and riverine areas.