If teachers wish to instruct their students about DST then here is the first real explanation for the timekeeping adjustment that anyone can appreciate.

Before DST is applied and the hour hand moves forward one hour, there is a natural symmetry between the length of time from sunrise to noon and noon to sunset. If there are 6 hours from sunrise to noon, then there are 6 hours from noon to sunset.

Take Washington DC, for example-

https://www.timeanddate.com/sun/usa/washington-dc

The 24 hour day and clocks are anchored to the sunrise/noon/sunset cycle as the planet turns once every 24 hours. Normally, clocks are referenced to the noon Sun as this is where the symmetry between the length of time from sunrise to noon and noon to sunset exists.

To better understand DST, go to the timeanddate website and down to the date for tomorrow after DST is applied. With the cursor, pick up the Sun and move it back one hour towards sunrise and almost immediately the reader will understand why we have 'longer evenings' and shorter mornings even outside the natural lengthening of daylight during the summer months.

DST, like Timezones, are later developments made possible by the 24 hour system and the Lat/Long system. It is time for people to set aside the contrived notions based on the daily change in the position of the stars which attempted to set aside the anchor in the central/stationary Sun for the relationship between the natural noon cycle and the 24 hour cycle fixed to noon.

On Saturday, March 12, 2022 at 1:25:43 AM UTC-7, kellehe...@gmail.com wrote:

> DST, like Timezones, are later developments made possible by the 24 hour system
> and the Lat/Long system. It is time for people to set aside the contrived notions
> based on the daily change in the position of the stars which attempted to set
> aside the anchor in the central/stationary Sun for the relationship between the
> natural noon cycle and the 24 hour cycle fixed to noon.

You _are_ partly right.

Neither Daylight Saving Time (or Summer Time) nor Standard Time, which replaces
local time with standard time zones differing by one hour, have anything to do with
"Sidereal Time" or stellar circumpolar motion, and these matters, even if they are
of interest to astronomers for pointing their telescopes, may therefore be entirely
ignored in explaining them.

No, Daylight Saving Time and Standard Time are entirely defined in relation to natural
noon and the solar day.

John Savard

The attempt to displace and the 24 hour system allied to the Lat/Long system with RA/Dec must now be seen to have failed really badly. It is possible to retain RA/Dec in the same category as Timezones and the DST adjustment as useful additions to the main timekeeping systems where natural noon and clock noon keep roughly in step.

The wider population currently dwell on DST as a jetlag issue, however, those engaged in solar system research and especially cause and effect between the motions of the Earth and experiences on the surface should realise it is a doorway into more challenging issues both technically and historically..

On Sunday, March 13, 2022 at 1:14:16 AM UTC-7, kellehe...@gmail.com wrote:
> The attempt to displace and the 24 hour system allied to the
> Lat/Long system with RA/Dec must now be seen to have failed
> really badly. It is possible to retain RA/Dec in the same category
> as Timezones and the DST adjustment as useful additions to
> the main timekeeping systems where natural noon and clock
> noon keep roughly in step.

Natural noon and clock noon indeed keep "roughly in step". Why is that?

Well, the difference between the two is the Equation of Time.

Which I explain here

http://www.quadibloc.com/science/eot.htm

remember?

From the viewpoint of the man in the street, whether it is day-time or
night is important. The direction in which the Big Dipper is pointing
is not. So in _that_ sense you can indeed say that sidereal time or
stellar circumpolar motion is just something added on to the ordinary
timekeeping system that tells us when to go to work or take our meals.

But you go further than that. You say the natural noon cycle is _genuinely_
fundamental. Professional astronomers *know* that isn't true.

They know that the Earth really is a big ball of rock, and so its rotational
motion is uniform except when some force speeds it up or slows it down,
as seasonal variations in prevailing winds do very slightly. So slightly that
until atomic clocks came along, stellar circumpolar motion, as measured
by transit circles, was directly useful in calibrating the most accurate
pendulum clocks.

The sun's apparent motion in our sky is a _compound_ motion, the result
of _both_ the Earth's very nearly uniform physical rotation - which we
see directly in stellar circumpolar motion, with the period of 23 hours,
56 minutes, and 4 seconds - and the Earth's real orbital motion around the
Sun.

Add the two together, and you get the complicated apparent motion of the
Sun in our sky that gives us our daily natural noon cycle.

Those things are solid facts; they're natural consequences of living in a
Sun-centered Solar System where the Earth's orbit is an ellipse, as found by
Kepler. Newton refined and perfected the work of Copernicus, Galileo, and
Kepler, finding the physical causes of the phenomena they observed, and
removing the Sun-centred nature of our Solar System from all doubt.

Failed really badly? The only thing that's failed really badly is your attempt
to argue otherwise, that somehow Newton made a mistake, and other
people made a mistake by following his wrong perspective. That notion isn't
just wrong; it's laughable. It's laughable now, and it always will be.

It's true that not very many people can follow the mathematics used by
Adams and Le Verrier to predict the position of Neptune from discrepancies
in the motion of Uranus. That's hardly a pressing concern in everyday life.
But this was perhaps the crowning vindication of Newton's explanation of
the planets' motions in terms of the inverse-square law of gravity combined
with the ordinary physical principles of the momentum of moving bodies.

And not very many people need to calculate a table of the Equation of Time
from first principles either. Once it's been done, someone using a sundial to
tell time can just use such a table.

But just because things are removed from ordinary daily life doesn't make them
untrue. Scientists need to peer behind surface appearances to see what is
really true, to gain the fuller understanding of Nature that permits its manipulation
by technology.

Of course, there _are_ those who feel, with a considerable amount of
justification, that we've done rather too much in the way of manipulating Nature
with our technology - so they might well favor them restricting themselves to an
"interpretive" approach, instead of going for prediction with the use of advanced
mathematics like calculus. But that's not because the approach they've been
taking _doesn't work_; no, indeed.

Instead, the problem is that it works *all too well*, giving us the power to
destroy our civilization and much of life on Earth with the atomic bomb and
its larger successor the hydrogen bomb.

John Savard

On Sunday, March 13, 2022 at 12:14:16 AM UTC-8, kellehe...@gmail.com wrote:

> The attempt to displace and the 24 hour system allied to the Lat/Long system with RA/Dec must now be seen to have failed really badly.

But Gerald, no one has attempted to do any such thing! Why would you make such a silly claim? Each exists for very good reasons and is invaluable for specific tasks. The average man on the street never needs to know that sidereal time even exists because it has no value for him, wheres sidereal time has a lot of value for astronomers and other scientists. It is a valuable tool that is irreplacable...

On Sunday, March 13, 2022 at 3:26:39 PM UTC, palsing wrote:
> On Sunday, March 13, 2022 at 12:14:16 AM UTC-8, kellehe...@gmail.com wrote:
>
> > The attempt to displace and the 24 hour system allied to the Lat/Long system with RA/Dec must now be seen to have failed really badly.
> But Gerald, no one has attempted to do any such thing! Why would you make such a silly claim? Each exists for very good reasons and is invaluable for specific tasks. The average man on the street never needs to know that sidereal time even exists because it has no value for him, wheres sidereal time has a lot of value for astronomers and other scientists. It is a valuable tool that is irreplacable...

You just had DST explained to you for the first time and I even made allowances for RA/Dec in the same category as Time zones and Daylight Savings Time. It is delightful for those who don't have a cringing need to retain the errors inherited from careless people a number of centuries ago.

https://www.timeanddate.com/sun/usa/san-diego

Move the Sun backwards towards sunrise today by one hour and come to appreciate, along with all people capable of experiencing satisfaction, how 'longer evenings' occur by creating an asymmetry between natural noon and 24 hour clock noon. So, timekeeping works off the sunrise/noon/sunset cycle with a symmetry between the length of time from sunrise to noon and from noon to sunset as it naturally occurs and 24 hour clock noon is anchored to natural noon.

I like you Paul but I like sharing information for the sake of future generations even more. I suggest you do the same and perhaps consider that I may actually wish to promote both astronomy as a magnification exercise and genuine solar system research.