Daylight continues to get longer after June 21

[wd40]

On June 21 the Sun ceases setting as far north as it is going to go and reverses southwards.

Is there any conceivable way that it could continue setting further north after June 21, even for a few days, and what would it imply?

Is it possible for the Sun to set several degrees further north without there necessarily being an increase in the length of daylight?

[Hornblower]

On June 21 the Sun ceases setting as far north as it is going to go and reverses southwards.

Is there any conceivable way that it could continue setting further north after June 21, even for a few days, and what would it imply?

No.

Is it possible for the Sun to set several degrees further north without there necessarily being an increase in the length of daylight?

No.

[potoole]

If the sun was to set further to the north (where you live) after june 21, the sun would stay up longer. For instance, at the arctic circle the sun doesn't set at all on, and around, June 21.

However, it sets where it sets, pretty much the same every year on June 21. I don't know if there is any variation; not during my lifetime, anyway.

I'm not an expert, though.
PO'T

[profloater]

my understanding is there is asymmetry so that june 21 is the longest day length but the evening gets longer while the morning gets later for about ten days, (or maybe the other way around, I forget).

[Hornblower]

my understanding is there is asymmetry so that june 21 is the longest day length but the evening gets longer while the morning gets later for about ten days, (or maybe the other way around, I forget).

That is correct, and is a consequence of the properties of tilted great circles on the celestial sphere. I understand it perfectly, but I have a beastly time explaining it verbally to anyone who is not already conversant in the necessary trigonometry. It is easy to illustrate visually by plotting the motions on a globe.

[potoole]

I'm pretty sure that, as each day progresses towards June 21, the sun rises earlier in the morning and sets later in the evening. Until on, or around June 21, when things start going the other way.

This is from my obsevations as an old farm kid. Well I was young once.

Patrick

[potoole]

One can keep track of times of sunrise, sunset in a newspaper. Look in the weather section the hours of sunrise and sunsets are given.

PO'T

[Hornblower]

One can keep track of times of sunrise, sunset in a newspaper. Look in the weather section the hours of sunrise and sunsets are given.

PO'T

If you do so, beware of rounding errors. I once saw a newspaper writer claim that there were dates other than the solstice date where the daylight period was longer. He was going by the published times in the weather report which were rounded to the nearest whole minute. Then when the sunrise time hit a rounding break and the sunset time did not, it made it appear that the daylight period had suddenly changed by one minute when the actual change was a few seconds in the opposite direction.

At my latitude, about 39 degrees north, the earliest sunrise is about a week before the solstice and the latest sunset is about a week after. During that two week interval around the solstice both are getting later simultaneously, but at different rates. That is where the rounding breaks can give you false readings.

[Hornblower]

If you do so, beware of rounding errors. I once saw a newspaper writer claim that there were dates other than the solstice date where the daylight period was longer. He was going by the published times in the weather report which were rounded to the nearest whole minute. Then when the sunrise time hit a rounding break and the sunset time did not, it made it appear that the daylight period had suddenly changed by one minute when the actual change was a few seconds in the opposite direction.

At my latitude, about 39 degrees north, the earliest sunrise is about a week before the solstice and the latest sunset is about a week after. During that two week interval around the solstice both are getting later simultaneously, but at different rates. That is where the rounding breaks can give you false readings.

I found just such a booby trap in a listing of published sunrise and sunset times for Washington. They are rounded to the nearest minute. This table made it appear that the daylight period decreased from 14:54 on June 17 to 14:53 on June 18, when the interval actually had increased by about 11 seconds. The sunrise time had leveled off about June 14 and was slowly getting later. From the 17th to the 18th it was getting later more slowly than the sunset time, but it nevertheless crossed a rounding point first, giving the false shortening as indicated by the rounded numbers. On the 21st, the solstice date, the sunset time crossed a rounding point and the published interval appeared to jump back to 14:54 when actually it had increased less than 2 seconds from the previous day and about 25 seconds from the 17th.

[Jens]

I can't say I understand this kind of thing all that well, but I think also it would depend slightly from year to year, so that it would get later and later each year until we get to a leap year, and then it is basically sent forward one day.

[Ivan Viehoff]

I'm pretty sure that, as each day progresses towards June 21, the sun rises earlier in the morning and sets later in the evening. Until on, or around June 21, when things start going the other way.

You are mistaken. Explained in full here, though it takes a while to get to the punchline. http://en.wikipedia.org/wiki/Equation_of_time

In brief summary, due to the eccentricity of the earth's orbit (about 1/3 of the reason) and the obliquity of the eccliptic (about 2/3 of the reason, and unfortunately the trickier point to grasp in my experience), actual time elapsed from one sun overhead to the next sun overhead is not precisely 24 hours, it is only 24 hours on average. A fixed 24 hour clock, with average sun overhead at noon is called "local mean time" (like Greenwich Mean Time -mean for average, in contrast to measuring the height of the sun every day). At certain times of the year, it is persistently a few seconds more than 24 hours, and these few seconds can accumulate over a few months so that the recorded time of sun overhead varies by up to about 16 mins later than a fixed noontime on such a 24 hour clock. In other parts of the year, the time is a few seconds shorter than 24 hours, and this accumulates to take you back the other way.

The consequence of this is that using such a mean time fixed 24 hour clock, as we do, the latest sunrise and earliest sunrises do not occur on the same day, and neither occurs on the summer solstice, as explained above.

If you followed the ancients and said that noon was the time of sun overhead each day, this would not happen.

[Hornblower]

I can't say I understand this kind of thing all that well, but I think also it would depend slightly from year to year, so that it would get later and later each year until we get to a leap year, and then it is basically sent forward one day.

Yes, the whole pattern comes about 6 hours later in each successive calendar year, and then is bumped back a day with each leap year. My exercise was an idealized one in which the solstice is at noon on June 21 every time.

[John Mendenhall]

Sky & Telescope publishes a wonderful 11 x 17 chart in their Dec issue called the Stargazer's Almanac which shows the interesting goodies in the sky day by day for the coming year, and sunrise/sunset, and on and on. Fits on the refrigerator door just fine, and even the astronomy know-nots among your friends and family will be caught looking at it.

[wd40]

http://zen-haven.dk/summer-solstice-...m-here-on-out/

If the angle of the Earth's tilt was to increase to 25 degrees or decrease to 22 degrees, would it effect the solstice falling out on June 21 i.e. would it occur on a different date?

[Nowhere Man]

No. The dates of the solstices and equinoxes are purely functions of the Earth's orbit. The tilt of the planet's axis makes them more obvious.

But if the Earth's axis was at exactly 90 degrees to the plane of the orbit, there would be no solstices or equinoxes, just one year-long equinox.

Fred

[wd40]

So the only thing that could make the solstice occur on a day other than June 21 each year would be an increase or decrease in the Earth's 67,000mph speed round the Sun?

[Jens]

So the only thing that could make the solstice occur on a day other than June 21 each year would be an increase or decrease in the Earth's 67,000mph speed round the Sun?

I think it's both more complicated and less complicated than you think. What exactly do you mean by "June 21"? Do you mean simply the date on the calendar, or do you mean the date when the earth is in a certain place in its orbit? In a sense, I could give you a very strange answer, is that there is a much easier way to make it fall on a day other than June 21. Just take out one day out of the calendar in January and add a day in September. Then it will fall on June 22.

[wd40]

I mean the date when the Earth is in a certain place in its orbit.

eg if the report here
http://www.dailymail.co.uk/sciencete...elerating.html
had been a real astronomical effect, would there be any plausible change in the Earth's orbit/angle/speed/perihelion that could account for it?

[Van Rijn]

So the only thing that could make the solstice occur on a day other than June 21 each year would be an increase or decrease in the Earth's 67,000mph speed round the Sun?

The solstice can occur slightly before or after June 21st because there isn't an exact yearly fit between the Gregorian calendar and the Earth's orbit (that's why there are leap years). Also, what is the 21st in one time zone can be the 20th or 22nd in another.

Here's a calculator. Try different years or time zones:

http://www.timeanddate.com/calendar/seasons.html

Now, if you're asking what could cause a dramatic difference right now, you would need to dramatically affect the Earth's orbit or day length. If you're talking long term, the day length will change, so in a billion years, say, our current calendar system wouldn't make much sense.

[Jens]

I mean the date when the Earth is in a certain place in its orbit.

In that case, even speeding up the earth's orbit would do nothing to change it, because see, if you are basing your calculation on the tropical year, it is always true by definition. A year is the period between one solstice and the next, so if the earth's orbital speed increases, it merely means that June 21 will come more quickly.

I now read the article you are referring to. I don't think there is anything that could account for that. The earth's speed cannot be increased like that without causing a lot of other effects that would be notice. I think you need to understand that when the sun rises over Greenland, it does so very, very slowly, rising in a spiral, so the effect is a bit different from what it would be at lower latitudes.

[grapes]

Worse, the solstice does not come at the same point in the earth's orbit--the precession of the equinoxes. We make it work though, by defining the year not as the time it takes to go around the sun, but the time from one equinox to the next. On average.

EDT: or, like what Jens said

[Githyanki]

If the daylight increases after June 21, you're in South America!

[NEOWatcher]

If the daylight increases after June 21, you're in South America!

Hemisphere

[PlutonianEmpire]

I think the only way to get daylight to increase after the 21'st of June is if there is an extremely close close encounter with a giant planet that approaches and passes us at a particular angle and/or speed.

[wd40]

If this report http://www.stuartwilde.com/2012/07/b...e-shift-docco/ that the Arctic Sun is setting at a different position than it used to is shown to be correct, is there any plausible explanation apart from an axis shift?

And if it's not correct, then why do the Eskimos report it: hoax, error, mass hysteria, lowering of Arctic ice/shifting of landmarks due to melting, atmospheric effect, the Sun itself having moved?

[Hornblower]

I would say atmospheric effects and shifting ice. A tilt change would have been seen by astronomers everywhere.

In my first impression, the presentation had two strikes against it when Nibiru appeared in the headlines. This looks like a popular media sensation seeker without proper scientific vetting.

[Van Rijn]

If this report [] that the Arctic Sun is setting at a different position than it used to is shown to be correct, is there any plausible explanation apart from an axis shift?

An axis shift isn't a plausible explanation. Leaving aside the question of what could cause it, it would be obvious worldwide.

Refraction somewhat affects where the midnight sun can be seen, so that would be a likely mechanism.

From:

http://www.answers.com/topic/midnight-sun

Latitude +66°34′ defines the Arctic Circle, which is the southernmost latitude in the Northern Hemisphere where the midnight sun can be observed near the summer solstice. However, atmospheric refraction raises objects on the horizon by about 34′, and the midnight sun can therefore be seen for a few days from locations 80 km (50 mi) south of the Arctic Circle. Observers at latitudes above the Arctic Circle see the midnight sun higher above the northern horizon, or correspondingly, see the midnight sun before the summer solstice.

[sirius0]

Hemisphere

South America is accurate enough. The daylight increases in Australia after the 22 June!