Which mechanism most directly enabled ancient mariners to accurately estimate longitude?

💡 Explanation

When Harrison's chronometers became available, accurate timekeeping enabled longitude calculations by comparing local solar time with time at a reference meridian because each hour difference corresponds to 15 degrees of longitude. Therefore, chronometers were essential, rather than sundials, dead reckoning or magnetic variation which address latitude or heading.

• Which limitation increased navigational risk when using early marine chronometers aboard 18th-century sailing vessels?
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• Which optical consequence primarily arises during a solar eclipse viewed through early Islamic pinhole cameras ('camera obscura')?
• Which physical effect limited the Roman ballista's range when scaling up projectile size?
• Which structural weakness most affected 18th-century timber ship wall construction during sustained broadside cannon fire?
• Which soil consequence occurred initially when pre-Columbian chinampa agriculture was established in shallow lake environments?