🔍 Key Concepts

• local apparent time (LAT) vs local mean time (LMT) and the roles of the apparent sun and mean sun • the definition and purpose of the equation of time in navigation • which quantities depend on longitude or time zones versus those that do not

💭 Think About

• Ask yourself: what specifically causes apparent solar time to differ from mean solar time during the year? Is it longitude, time zones, or something about the Sun’s motion? • Which of the choices is a known term used to express the difference between apparent solar time and mean solar time on the same meridian? • For each option, decide: does this quantity change with where you are east/west on Earth, or does it change with the date of the year at a fixed place?

✅ Before You Answer

• Identify which option refers to a quantity that varies with date but not with longitude on the same meridian. • Eliminate any choices that are clearly used to convert between places (longitudes or time zones) rather than between different kinds of solar time at one place. • Confirm that the correct quantity is typically found in the Nautical Almanac as a daily value used to convert between apparent and mean time.