Why are Sunrise and Sunset Out of Step?
Discussion
Why aren't the latest sunrise and the earliest sunset on the same day?
Why is the shortest day December 21st?
https://www.timeanddate.com/sun/uk/london
Why is the shortest day December 21st?
https://www.timeanddate.com/sun/uk/london
The Mad Monk said:
Maybe you should have asked this in the Science Forum (less likelihood of nonsense answers).The earth is not completely upright relative to the sun. It is tilted at an angle of 23.5 degrees to the vertical - probably as a result of a collision with a large planetary body early in its life. It could even be this collision that formed our moon.
Because it is tilted, in it's path around the sun, at one point in the year the northern hemisphere is pointed at the sun and exactly six months later it is pointed away from the sun. The former happens around 21 June - which gives us the longest hours of daylight in the northern hemsiphere and the latter gives us the shortest hours of daylight, which occurs around 21 December.
It is this tilt that gives us the graduated seasons.
And, of course, the longest and shortest days of the year are reversed in the southern hemisphere.
Mars has a similar tilt to earth - although it's not known why - so it experiences broadly similar seasons to earth - only they are twice as long because Mars' year is twice as long.
Eric Mc said:
Maybe you should have asked this in the Science Forum (less likelihood of nonsense answers).
The earth is not completely upright relative to the sun. It is tilted at an angle of 23.5 degrees to the vertical - probably as a result of a collision with a large planetary body early in its life. It could even be this collision that formed our moon.
Because it is tilted, in it's path around the sun, at one point in the year the northern hemisphere is pointed at the sun and exactly six months later it is pointed away from the sun. The former happens around 21 June - which gives us the longest hours of daylight in the northern hemsiphere and the latter gives us the shortest hours of daylight, which occurs around 21 December.
It is this tilt that gives us the graduated seasons.
And, of course, the longest and shortest days of the year are reversed in the southern hemisphere.
Mars has a similar tilt to earth - although it's not known why - so it experiences broadly similar seasons to earth - only they are twice as long because Mars' year is twice as long.
I didn't think of the Science Forum.The earth is not completely upright relative to the sun. It is tilted at an angle of 23.5 degrees to the vertical - probably as a result of a collision with a large planetary body early in its life. It could even be this collision that formed our moon.
Because it is tilted, in it's path around the sun, at one point in the year the northern hemisphere is pointed at the sun and exactly six months later it is pointed away from the sun. The former happens around 21 June - which gives us the longest hours of daylight in the northern hemsiphere and the latter gives us the shortest hours of daylight, which occurs around 21 December.
It is this tilt that gives us the graduated seasons.
And, of course, the longest and shortest days of the year are reversed in the southern hemisphere.
Mars has a similar tilt to earth - although it's not known why - so it experiences broadly similar seasons to earth - only they are twice as long because Mars' year is twice as long.
Thank you for your response.
The Mad Monk said:
Why aren't the latest sunrise and the earliest sunset on the same day?
Why is the shortest day December 21st?
https://www.timeanddate.com/sun/uk/london
Because it isn't exactly 24 hours from sun-as-overhead-as-it-gets one day and the next. So our clock noon is a bit offset from astronomical noon, so even when the days are getting longer sunset can get slighter closer to clock noon because clock noon is running late.Why is the shortest day December 21st?
https://www.timeanddate.com/sun/uk/london
Dr Jekyll said:
Because it isn't exactly 24 hours from sun-as-overhead-as-it-gets one day and the next. So our clock noon is a bit offset from astronomical noon, so even when the days are getting longer sunset can get slighter closer to clock noon because clock noon is running late.
Isn't that what Leap Years and extra seconds on occasional years are supposed to correct?Yes. The earth's movements don't fit precisely into the time intervals man has created - and vise versa. Therefore, corrections have to be inserted every so often in order to get things back on track. The most well known and obvious "correction" is the leap year system.
Other factors cause our artificially set time intervals to go out of sync with the real universe such as the gravitational interactions between the earth, sun and moon and the fact that as well as the earth being tilted, the tilt itself is actually wobbling like a spinning top that is slowing down. That is known as precession.
Other factors cause our artificially set time intervals to go out of sync with the real universe such as the gravitational interactions between the earth, sun and moon and the fact that as well as the earth being tilted, the tilt itself is actually wobbling like a spinning top that is slowing down. That is known as precession.
The Mad Monk said:
Dr Jekyll said:
Because it isn't exactly 24 hours from sun-as-overhead-as-it-gets one day and the next. So our clock noon is a bit offset from astronomical noon, so even when the days are getting longer sunset can get slighter closer to clock noon because clock noon is running late.
Isn't that what Leap Years and extra seconds on occasional years are supposed to correct?Puggit said:
Something to do with the fact the Earth' s spinning axis is not 90 degrees from the solar plane, but is 23.5 degrees out plus it wobbles around that axis and doesn't stay at 23.5 degrees.
Long time since I did astronomy at uni
Enough with any of this Puggit, when the hell is the snow coming!?Long time since I did astronomy at uni
p1stonhead said:
Enough with any of this Puggit, when the hell is the snow coming!?
There is a related answer here - December and early Jan are best times to get Arctic blasts because of the shorter amount of daylight. Daylight heats up the surface, night time is better for snow. Normally the cooler months are Feb/March, which have longer days. Thurs night into Friday is your answer though.
Gassing Station | Science! | Top of Page | What's New | My Stuff