Changing Day Length

[Airbrush]

Does anyone know what times of the year, during the equinoxes (Mar 20 & Sep 22/23) or during the solstices (Dec 21/22 & Jun 20/21), are day length changing more rapidly?  My guess would be the length of day is changing most rapidly during the equinoxes, is that correct?

Edited October 20, 2017 by Airbrush

[swansont]

It doesn't, because the ellipticity of the orbit is not "synched" with the equinoxes/solstices.

https://en.m.wikipedia.org/wiki/Equation_of_time

[Airbrush]

Very interesting, thank you.

[Airbrush]

I just did some calculations using a sunrise & sunset times calculator and confirms my suspicion that the day lengths change more rapidly during the equinoxes than the solstices, using my location Southern California.  I entered the equinox dates 3/20 & 3/22, a 2-day period, and the day lengths got longer by 4 minutes, but when I entered solstice dates 6/21 & 6/23, the day lengths did not change at all!

Then I tried equinox dates 9/22 & 9/24 and day lengths, during the 2-day period, got shorter by 5 minutes, but the solstice dates of 12/21 & 12/23, during the 2-day period, day length got longer by 1 minute only.  So, for my location in Socal, it seems to be generally true that day lengths change faster during equinoxes, and change slower during solstices.

http://www.calendar-updates.com/sun.asp?PostalCode=91406&Submit=Get+Sunrise+%2F+Sunset+Times

 

 

[Janus]

3 hours ago, Airbrush said:

I just did some calculations using a sunrise & sunset times calculator and confirms my suspicion that the day lengths change more rapidly during the equinoxes than the solstices, using my location Southern California.  I entered the equinox dates 3/20 & 3/22, a 2-day period, and the day lengths got longer by 4 minutes, but when I entered solstice dates 6/21 & 6/23, the day lengths did not change at all!

Then I tried equinox dates 9/22 & 9/24 and day lengths, during the 2-day period, got shorter by 5 minutes, but the solstice dates of 12/21 & 12/23, during the 2-day period, day length got longer by 1 minute only.  So, for my location in Socal, it seems to be generally true that day lengths change faster during equinoxes, and change slower during solstices.

http://www.calendar-updates.com/sun.asp?PostalCode=91406&Submit=Get+Sunrise+%2F+Sunset+Times

 

 

You weren't clear by what meant "day length".  From your last post, it appears that you meant the daylight period from sunrise and sunset, rather than the length of the Solar day (solar noon to Solar noon.) which varies in length by ~51 sec over the course of a year.

[John Cuthber]

Generally a function like "length of the day"  changes most slowly at maxima and minima.

In this case that means the solstices.

A hand-waving "it seems reasonable" argument indicates that the function changes most quickly when it's as far from the maxima and minima as possible. And for this function, that idea suggests that the equinoxes are where the  day length changes most quickly.

A slightly more sophisticated argument looking at sine waves + such confirms this.

[Airbrush]

17 hours ago, John Cuthber said:

Generally a function like "length of the day"  changes most slowly at maxima and minima.

Thank you, that is well-stated, and what I suspected.  Changes are slower at maxima and minima.

18 hours ago, Janus said:

You weren't clear by what meant "day length".  From your last post, it appears that you meant the daylight period from sunrise and sunset, rather than the length of the Solar day (solar noon to Solar noon.) which varies in length by ~51 sec over the course of a year.

Yes, I should have clarified length of daylight hours.

Edited October 22, 2017 by Airbrush