eli5. New Year and Earth revolution

347 views

Earth celebrates several new years— according to the communities and cultures. Chinese have their own new year, westerns have their own, and so have the south asian like Nepal. I’m from Nepal, and there January 1 is not the equivalent date when we celebrate our New Year. And, that might be the case for other places too(Not sure about that tho).

So, which new year is the exact day when the Earth completed one revolution around the Sun?

In: 0

There’s no designated starting place for one orbit so there’s no official date, either. Every day marks the end of one orbit, the one that started a year ago.

Basically all of them. When a year starts is absolutely arbitrary — you choose a day and call that the day the year starts, and then you count 365 days from that.

It’s a bit more complex than that — you have to account for leap-time, etc, but basically there’s no “correct” first day of the year.

> So, which new year is the exact day when the Earth completed one revolution around the Sun?

…They all are. They just start and end at different times along the cycle. It is a big loop, there is no objectively correct start and end point.

There’s no fixed starting point for an orbit. Each of those new years celebrates 1 revolution since the last one of that type of new years. There’s 1 revolution between Chinese new years, 1 revolution between Nepalese new years, 1 revolution between Western new years, and so on.

To put this in more concrete terms: from March 1 to March 1 is one year, from April 19 to April 19 is 1 year, from December 12 to December 12 is one year, and so on.

The other comments have already explained that you can start a revolution around the Sun on any day.

I went ahead and looked up the Nepalese calendar, which I have no prior knowledge of, and a brief glance tells me that it’s a lunisolar calendar…based on the phases of the Moon. The Moon has nothing at all to do with the Earth’s year, so generally speaking, lunisolar calendars are not a very good way of keeping track of Earth’s orbit around the Sun. There are leap years and intercalary periods to make up for this, so over long periods it isn’t an inaccurate calendar, but from one average New Year’s Day to the next, your calendar doesn’t sound like it’s a full trip around the Sun. The Gregorian calendar technically isn’t either, but it gets as close as the Earth’s rotation allows.

>So, which new year is the exact day when the Earth completed one revolution around the Sun?

There is no such objective date, because there’s no objective start or end point for what constitutes one revolution around the Sun.

*Technically* speaking, though; lunar calendars are not accurate with respect to timing the passage of a single year, entirely because they’re based on the phases of the moon. Granted, the moon actually does (by coincidence) line up relatively closely with the time it takes for the Earth to make a revolution around the Sun, but it’s going to be off, and the error builds up over time.

The Western Gregorian calendar also isn’t exact (as it tries to align travel time around the Sun to a specific number of days), but it’s much closer, and it already has a system in place called Leap Years to account for the errors.

The “New Year” is arbitrary. A year is completed when the Earth completes one revolution. That one revolution could start and complete at ANY one point.