Neil deGrasse Tyson Explains Why We Have Leap Days
StarTalk・2 minutes read
Earth's rotation and orbit around the sun define a day and a year, with leap days added every four years to account for the extra hours, a practice introduced by Ancient Rome's Julian calendar and reformed by Pope Gregory XIII in the 16th century. The Gregorian calendar adjustment removed 10 days in October 1582 to correct the calendar drift, ensuring precision with the help of Jesuit astronomers and highlighting the rarity of birthdays on leap days.
Insights
- Earth's rotation on its axis determines a day, while its orbit around the sun defines a year, with the need for a leap day every four years to account for the extra hours.
- The Gregorian calendar, introduced by Pope Gregory XIII, addressed calendar drift by removing 10 days in October 1582 and established the rules for adding leap days every four years, except in certain cases, to realign astronomical events like the vernal equinox and Easter.
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365 days and 6 hours
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Summary
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"Leap Days: Aligning Earth's Orbit and Time"
- Earth rotates on its axis, defining a day, while it orbits the sun, constituting a year.
- A year comprises 365 days and 6 hours, necessitating a leap day every four years.
- Ancient Rome's Julian calendar introduced leap days to rectify the extra hours.
- Pope Gregory XIII, in the late 16th century, reformed the calendar to realign the vernal equinox and Easter.
- The Gregorian calendar adjusted by removing 10 days in October 1582 to correct the calendar drift.
- Leap days are added every four years, except every 100 years, and then every 400 years.
- The Jesuits, skilled astronomers, rectified the calendar without telescopes, ensuring precision.
- Birthdays on leap days are rare, emphasizing the importance of celebrating one's orbital time around the sun.
