How long is "1 Year" exactly

[ack]

Oldie but goodie

 

[astrotoy]

A quiz based on 3 seconds of the video.

What was the last day (date) of February, 2019?

https://www.google.com/search?q=Feb...QIHR1NDQ0Q9QEwAHoECA4QKg#imgrc=js7EZyrS3p6_5M:

But then, what will be the last day (date) of February, 2020?

https://www.google.com/search?q=Feb...QIHbo7Az8Q9QEwAHoECA0QJA#imgrc=MVNAYT2IdTg4gM:

Then what was the last day of February, 1900?

https://www.google.com/search?q=Feb...00Q9QEwBHoECA8QJA#imgrc=LEpdWM04rCARCM:&vet=1

What is going on? The answer is hidden in the next question.

What is the day (date) after October 4th, in the year 1582 if you lived in a Catholic country?

https://www.google.com/search?clien...QIHQtsBWkQ4dUDCAY&uact=5#imgrc=urSx2ijn_N3eVM:

Hint: see 2:55 in the video above.

More tomorrow, including why Henry the Eighth's first wife having a daughter and not a son made the answer to the last question different in England.

Larry, your astronomer friend

 

[ack]

OK we know that centuries are not leap years. But if the definition of 1-year varies and is relative, how was that "leap year" thing calculated, and moreover, why did it stick

 

[ack]

And since we now know that, over time, there are many North Stars, here's another interesting article

The Egyptian pyramids may align with an ancient north star. NASA scientists found that star undergoes never-before-seen eclipses.

https://www.businessinsider.com/nas...ZYTXo4rT1zSFGT_-IRgXyhi46ZcgEH-oaMeC738Mv8LAo

 

[astrotoy]

OK we know that centuries are not leap years. But if the definition of 1-year varies and is relative, how was that "leap year" thing calculated, and moreover, why did it stick

Close, but not quite. 2000 was a leap year, but 2100, 220, and 2300 will not, 2400 will be. We use the tropical year based on the vernal equinox. That is because the calendar was religious and the vernal equinox is used to calculate Easter. The problem was when we switched to the Julian Calendar (named after Julius Caesar) the leap year was instituted every four years. But the tropical year is 365.2422 days long, not 365.25 days. So there were too many leap years ( 3 too many in 400 years). That caused the vernal equinox and the calculation of Easter (Christ was born just a few years after Julius Caesar was killed) to slowly slip earlier and earlier over the centuries. Finally, in 1582, Pope Gregory instituted a big change, correcting for the 10 days of slippage all at one time (October 4 to October 15, 1582) and eliminating 3 leap years (the century years that do not evenly divide by 400) every 400 years. However, this was only done in the Catholic countries which the Pope controlled.

Henry the Eighth, for example was king of England at the time, and when his first wife Catherine of Aragon (BTW who was his older brother's widow - Henry became king because his older brother had died) gave birth to Mary (later known as Bloody Mary) and no further sons, Henry appealed to the Pope for a divorce (actually an annulment) (remember he was born and raised a Catholic), and broke from the Catholic church when the Pope refused - marrying Anne Boleyn who gave birth to Elizabeth I, and later to a legitimate son Edward (who did become king) by Jane Seymour. So when Pope Gregory changed the calendar, Elizabeth I who was now queen of England, didn't go along with the change and England didn't make the switch until the 1700's. So there were two parallel calendars running during this time, with England (and other Protestant countries) running 10 days (and eventually 11 days earlier than Catholic Europe). The US (colonies at the time) followed the English calendar.

Another calendar related puzzle. We all know that an octogon has eight sides, and the decimal system is based on the number 10. So why is October not the eighth month and December not the tenth month?

Larry