🔍 Key Concepts

• lunar day vs. solar day – what each one measures • how long it takes the Moon to return to the same position in the sky relative to an observer • the connection between the lunar day and the timing of tides (high tide times from one day to the next)

💭 Think About

• Think about how much later the Moon rises (or high tide occurs) on one day compared to the previous day. Is it exactly 24 hours later or slightly different? • Compare the Earth’s rotation relative to the Sun (solar day) with its rotation relative to the Moon (lunar day). Which one requires the Earth to turn a little more? • Recall that the Moon is moving in its orbit while the Earth is rotating. How does this motion affect the time between two successive moon‑over‑meridian passages?

✅ Before You Answer

• Estimate how many minutes difference there are between two successive high tides on consecutive days at the same port. • Decide whether that time difference makes the lunar day longer, shorter, or equal to 24 hours (a solar day). • Confirm that the definition of a lunar day is the interval between two successive transits of the Moon over the local meridian, not the Sun.