Explanation for seasonal declination

oriel36

The general view is represented this way where the Sun scribes a greatest arc on one Solstice, the smallest arc on the opposing Solstice and equal on the September/March Equinoxes -

https://www.gproxx.com/https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Solar_declination.svg/370px-Solar_declination.svg.png


In terms of planetary dynamics using the orbital/ecliptic plane as a baseline, the axial orientation of the Earth is entirely different on the March and September Equinoxes.

Copernicus originally got the behavior of the North and South Poles right when he described their relationship to the Sun and the circle of illumination as the planet orbits the Sun -

"The third is the motion in declination. For, the axis of the daily rotation is not parallel to the Grand Orb's axis, but is inclined [to it at an angle that intercepts] a portion of a circumference, in our time about 23 1/2°. Therefore, while the earth's center always remains in the plane of the ecliptic, that is, in the circumference of a circle of the Grand Orb, the earth's poles rotate, both of them describing small circles about centers [lying on a line that moves] parallel to the Grand Orb's axis. The period of this motion also is a year, but not quite, being nearly equal to the Grand Orb's [revolution]. "

http://copernicus.torun.pl/en/archives/astronomical/1/?view=transkrypcja&


As he was stuck with the framework of Ptolemy, he was forced to drop the idea by the time he wrote De Revolutionibus for specific reasons which would represent a rather large digression presently.

Observations from the surface confirm what Copernicus knew insofar as at the North and South Poles, there is a single day/night cycle with one sunrise per year on the equinox and one sunset on the opposite equinox where the Sun is either constantly in view or out of view for 6 months. As the polar points represent positions on the Earth's surface where rotational velocity is zero ( as opposed to a maximum at the Equator), it is safe to make a conclusion.

In the absence of daily rotation and all its effects, the entire surface of the planet , not just the North and South Poles, turn parallel to the orbital plane as a function of the Earth's orbital motion.

It is visually affirmed as the rotational orientation of the Earth using the orbital plane through the centre of the Earth as a baseline shows different orientations through an orbit -

https://www.youtube.com/watch?v=-OgLCH7jYp8&t=28s

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif

On the March Equinox, the orientation is Southwest to Northeast relative to the orbital plane.

If people want to believe that the circle of illumination pivots off the Equator then nothing worse but they can come to their senses and look at the Equator from space and how the relationship changes to the orbital plane each year. The celestial sphere modelers don't make the distinction between the September and March arcs in terms of axial orientation to the Sun or orbital plane hence their view that is beyond odd -

https://earthsky.org/?p=68679

Another project to tackle if Irish astronomy means anything.

ps200306

oriel36 wrote: »

In the absence of daily rotation and all its effects, the entire surface of the planet ... turn parallel to the orbital plane as a function of the Earth's orbital motion.

No it doesn't ... except from a privileged frame of reference which orbits with the Earth. As a fundamental physical explanation for seasonal declination this is pretty poor, since it requires a fictitious force to turn the Earth.

oriel36 wrote: »

It is visually affirmed as the rotational orientation of the Earth using the orbital plane through the centre of the Earth as a baseline shows different orientations through an orbit

It shows the different orientations. It doesn't explain them unless you also provide the non-trivial explanation of how fictitious forces arise in rotating coordinates.

oriel36 wrote: »

The celestial sphere modelers don't make the distinction between the September and March arcs in terms of axial orientation to the Sun or orbital plane hence their view that is beyond odd

The so-called "celestial sphere modelers" show how the Sun moves on the sky. Your preferred view shows how the sub-solar point changes. Neither explains the seasonal declination.

For that we need a non-rotating viewpoint which shows that the Earth's axial orientation is fixed in space (to a first approximation, at least). The explanation for that is moderately straightforward: it is the conservation of angular momentum in the absence of torque.

oriel36

I kept the explanation for the seasons separate from the other 'astronomy in antiquity' thread for the specific reason of explaining the seasons properly. I have no interest in RA/Dec modelers and their conclusions as they exist in a celestial sphere bubble where the Sun wanders through the background stars along with the planets.

On the Equinox, all areas on the surface do not have equal daylight and darkness as the South Pole station is already bathed in constant sunlight long before the single polar sunrise on the Equinox as a part of the single polar day/night cycle -

https://www.youtube.com/watch?v=okw6Mu3mxdM


The cause of the single polar day/night cycle is a function of the Earth's orbital motion where the entire surface of the Earth, not just the North and South Poles, turn parallel to the orbital plane and to the Sun. Not only does the Earth orbit the Sun but it orbits in a specific way.

Observers can enjoy the cause of the polar day/night cycle by analogy. If floor is the orbital plane of the Earth, their nose represents the North pole and their body represents the entire surface of the Earth, by walking/orbiting around a central object/Sun, they will come to understand the surface rotation aside from daily rotation.

Pick a fixed external point using the nose as representing the North Pole and walk around the central object/Sun while keeping your nose constantly fixed to the external point meaning you have to walk forwards, sideways, backward and then forwards again to complete the circuit. At one time or other your side, front and back will face the central/Sun so in planetary terms this is why they have a single day/night cycle at the North and South Poles and the seasons where this surface rotation combines with daily rotation.

ps200306

oriel36 wrote: »

Pick a fixed external point using the nose as representing the North Pole and walk around the central object/Sun while keeping your nose constantly fixed to the external point meaning you have to walk forwards, sideways, backward and then forwards again to complete the circuit. At one time or other your side, front and back will face the central/Sun so in planetary terms this is why they have a single day/night cycle at the North and South Poles and the seasons where this surface rotation combines with daily rotation.

Unless you're able to lean over at an angle of 23 degrees while walking in a circle without turning your body, the Sun in your model will be at a constant declination. This is hardly an explanation for seasonal declination.

A picture of the Earth in space with a fixed axial orientation is easier to understand. What is definitely not easier is those DSCOVR/EPIC pictures in which the Earth appears to have nodded by 47 degrees without explanation.

oriel36

ps200306 wrote: »

Unless you're able to lean over at an angle of 23 degrees while walking in a circle without turning your body, the Sun in your model will be at a constant declination. This is hardly an explanation for seasonal declination.

A picture of the Earth in space with a fixed axial orientation is easier to understand. What is definitely not easier is those DSCOVR/EPIC pictures in which the Earth appears to have nodded by 47 degrees without explanation.

I really, really don't have an interest in RA/Dec modeling and its pivoting circle of illumination off the Equator to suit a celestial sphere Universe and a wandering Sun. All that demonstrates is a recent emergence of a new group who attach themselves to RA/Dec software and see the solar system in terms of that subculture. It is less astronomy than a simulation exercise by manipulating imaging to suit a conclusion.

This thread is intended for those who can account for the polar day/night cycle first as another project made possible by actual space imaging.

https://www.youtube.com/watch?v=-OgLCH7jYp8&t=28s

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif

How the polar points turn across the fully illuminated face of the Earth from Solstice to Equinox uses the analogy where the body represents the Earth and the floor represents the orbital plane. hence the North Pole and South Poles are viewed from the orbital plane where the circle of illumination always remains vertical.

Presently, the North Pole has turned closer to the circle of illumination so the circumference where the Sun is out of sight has shrunk from its maximum circumference (Arctic circle) on the December Solstice. It will continue to shrink until the March Equinox when the Sun will come into view for the first time in 6 months and the only time this year as an event.

I had hoped to restrict objections to the other thread but unfortunately this thread has become another target for the people who imagine an Earth with a zero degree inclination as it suits their late 17th century English clockwork modeling. These people are more entrenched in the English past than the most dour Ulster unionist and can safely be bypassed as most people on this island do today.

ps200306

oriel36 wrote: »

This thread is intended for those who can account for the polar day/night cycle first as another project made possible by actual space imaging.

That perspective provides no explanation at all for how the Earth has managed to "nod" by 47 degrees. The co-orbiting frame is extremely confusing compared to a simple view of the Earth's fixed orientation in space.

oriel36

ps200306 wrote: »

That perspective provides no explanation at all for how the Earth has managed to "nod" by 47 degrees. The co-orbiting frame is extremely confusing compared to a simple view of the Earth's fixed orientation in space.

The Earth doesn't tilt or nod, it has two surface rotations in isolation and in combination creating the polar day/night cycle and in combination creating the seasons when the surface rotation as a function of orbital motion combines with daily rotation.

Viewed from the orbital plane, the challenge is to discover the cause where the North or South Poles are mid-way to the circle of illumination on the Solstice so 3 months later exist on the circle of illumination representing either polar sunrise or polar sunset depending on the moths involved (representing the orbital position of the Earth around the Sun).


I discovered that I can't praise you for your objections but I do understand where you are coming from within a celestial sphere viewpoint. The view from the orbital plane is also the view from the central Sun which doesn't move.

Copernicus originally get it right but again, didn't have the observations we have today and never extended the motions of the North Poles to the entire surface of the planet -

"The third is the motion in declination. For, the axis of the daily rotation is not parallel to the Grand Orb's axis, but is inclined [to it at an angle that intercepts] a portion of a circumference, in our time about 23 1/2°. Therefore, while the earth's center always remains in the plane of the ecliptic, that is, in the circumference of a circle of the Grand Orb, the earth's poles rotate, both of them describing small circles about centers [lying on a line that moves] parallel to the Grand Orb's axis. The period of this motion also is a year, but not quite, being nearly equal to the Grand Orb's [revolution]. " Copernicus

It is a matter of revisiting this perspective with contemporary imaging and especially as the two surface rotations can now be seen both in isolation and in combination -

https://www.youtube.com/watch?v=612gSZsplpE&t=15s

About 50 seconds in when the time lapse speeds up, the daily rotation of Uranus runs South to Northwards while the polar points turn at a rate of 4 1/2 degrees per Earth year parallel to the orbital plane .

Giving all this a break as there is a lot of information involved in all aspects of astronomy which require a good shake-up anyway.

ps200306

oriel36 wrote: »

The Earth doesn't tilt or nod, it has two surface rotations in isolation and in combination creating the polar day/night cycle and in combination creating the seasons when the surface rotation as a function of orbital motion combines with daily rotation.

If I am simply misunderstanding the prosaic language, I apologise, but the Earth doesn't have a surface rotation as a function of orbital motion except when viewed from a co-orbiting frame. Worryingly, you seem to be showing the same lack of comprehension as on other threads. You say:

oriel36 wrote:

In the absence of daily rotation and all its effects, the entire surface of the planet , not just the North and South Poles, turn parallel to the orbital plane as a function of the Earth's orbital motion.

They do not.

oriel36 wrote:

It is visually affirmed as the rotational orientation of the Earth using the orbital plane through the centre of the Earth as a baseline shows different orientations through an orbit

You then go on to show the view from DSCOVR/EPIC. You do realise that it is at the L1 point, co-orbiting with the Earth? In that frame of reference the Earth's poles will certainly describe a circle around an axis perpendicular to the orbital plane but, to use a favourite term of yours, it is illusory. I cannot believe you then quote Copernicus in support:

oriel36 wrote:

Copernicus originally get it right but again, didn't have the observations we have today and never extended the motions of the North Poles to the entire surface of the planet -

"The third is the motion in declination. For, the axis of the daily rotation is not parallel to the Grand Orb's axis, but is inclined [to it at an angle that intercepts] a portion of a circumference, in our time about 23 1/2°. Therefore, while the earth's center always remains in the plane of the ecliptic, that is, in the circumference of a circle of the Grand Orb, the earth's poles rotate, both of them describing small circles about centers [lying on a line that moves] parallel to the Grand Orb's axis. The period of this motion also is a year, but not quite, being nearly equal to the Grand Orb's [revolution]. " Copernicus

In spite of the heliocentric novelty, Copernicus had a properly medieval belief in the system of celestial spheres that had come down from Anaximander in the 6th c. BC. They appear in the very title of De revolutionibus Orbium Coelestium. It was natural for him to believe in an Earth embedded in his so called "Grand Orb" which would then naturally rotate in its annual cycle as it was carried around the Sun. In order to get seasonal declination he needed it to rotate with respect to the Grand Orb's axis. This is his so-called "motion in declination". Of course, in reality there is no such motion. Ignoring gyroscopic precession, the Earth's axis points a fixed direction in space in conformity with conservation of angular momentum.

I do sincerely hope that you are not confused on this point. If you have any doubts, try explaining what force causes this "motion in declination".

oriel36

It is not possible to deal with RA/Dec modelers as they have the same discipline as brexiteer politicians and should be avoided as they are too damaged to be of any use. Their objections would count but least people forget, they are a new bunch who manipulate imaging to suit their clockwork solar system and celestial sphere framework run off the rotational characteristics of the Earth -

https://apod.nasa.gov/apod/ap170319.html

You may as well conclude the Earth is flat in that image because it would be less offensive than the contortions needed to suit the RA/Dec conviction that never had a place in heliocentric astronomy. It is therefore a very 21st century unwelcome development and very much from a source of misguided people encountering celestial sphere software.


I have to continue with the process of explaining the single polar day/night cycle as a function of the Earth's orbital motion insofar as the North/South Poles have no net daily rotational velocity therefore when those Poles exit the circle of illumination on one Equinox turning parallel to the orbital plane, the Sun comes into view for the first time in 6 months. As the Poles continue to cross the fully illuminated face determined by the vertical circle of illumination perpendicular to the orbital plane, the circle where the Sun remains constantly in view expands until the Summer Solstice and reaches its maximum circumference defined by the Arctic and Antarctic circles.


What is happening presently is the area where the Sun is completely out of view at the North Pole is beginning to shrink after the December Solstice while simultaneously the area where the Sun is completely in view begins to shrink also at the South Pole. It is why, as a global perspective, the events from equinox to equinox are not symmetrical with the North and South Poles at the centre of those events. From the March Equinox to the June Solstice, the area where the Sun is completely in view or out of sight switches so the circumference where the Sun is constantly in view expands with the North Pole at its centre while the circumference where the Sun is out of sight expands at the South Pole.

Space age people use space age observations -


https://www.youtube.com/watch?v=-OgLCH7jYp8&t=28s

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif


The pivoting circle of illumination proponents should start their own thread otherwise it is graffiti for reasonable people.

ps200306

oriel36 wrote: »

It is not possible to deal with RA/Dec modelers as they have the same discipline as brexiteer politicians and should be avoided as they are too damaged to be of any use. Their objections would count but least people forget, they are a new bunch who manipulate imaging to suit their clockwork solar system and celestial sphere framework run off the rotational characteristics of the Earth -

https://apod.nasa.gov/apod/ap170319.html

You may as well conclude the Earth is flat in that image because it would be less offensive than the contortions needed to suit the RA/Dec conviction that never had a place in heliocentric astronomy. It is therefore a very 21st century unwelcome development and very much from a source of misguided people encountering celestial sphere software.

I have to continue with the process of explaining the single polar day/night cycle as a function of the Earth's orbital motion insofar as the North/South Poles have no net daily rotational velocity therefore when those Poles exit the circle of illumination on one Equinox turning parallel to the orbital plane, the Sun comes into view for the first time in 6 months. As the Poles continue to cross the fully illuminated face determined by the vertical circle of illumination perpendicular to the orbital plane, the circle where the Sun remains constantly in view expands until the Summer Solstice and reaches its maximum circumference defined by the Arctic and Antarctic circles.

What is happening presently is the area where the Sun is completely out of view at the North Pole is beginning to shrink after the December Solstice while simultaneously the area where the Sun is completely in view begins to shrink also at the South Pole. It is why, as a global perspective, the events from equinox to equinox are not symmetrical with the North and South Poles at the centre of those events. From the March Equinox to the June Solstice, the area where the Sun is completely in view or out of sight switches so the circumference where the Sun is constantly in view expands with the North Pole at its centre while the circumference where the Sun is out of sight expands at the South Pole.

Space age people use space age observations -

https://www.youtube.com/watch?v=-OgLCH7jYp8&t=28s

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif

The pivoting circle of illumination proponents should start their own thread otherwise it is graffiti for reasonable people.

This is hilarious. You object to one commenter posting a geosynchronous view of the Earth with a rotating circle of illumination. Then you yourself post a co-orbiting view from the L1 point in which the Earth's axial direction itself rotates with the seasons. The difference is the first commenter knew what he was looking at, with all its limitations of perspective. Whereas you seem to actually believe that the Earth's pole physically rotates with the seasons, according to Copernicus' "motion of declination".

The Earth's axis does not change direction in space! If you could stop ranting about RA/Dec modellers being the spawn of Satan for a moment, you would realise that nobody is even talking about spherical coordinates for once. In a frame that is stationary with respect to the Sun, the Earth's poles point in a constant direction.

oriel36

ps200306 wrote: »

This is hilarious. You object to one commenter posting a geosynchronous view of the Earth with a rotating circle of illumination.

It is simply not worth dealing with RA/Dec modelers ,after all, they show a pivoting circle of illumination off the rotational equator across the seasons on an Earth with a zero degree inclination and not a rotating circle of illumination in defiance of every orbital principle known and can be known -

https://apod.nasa.gov/apod/ap170319.html


If the thread was left alone, the actual explanation could be expanded including the appearance and disappearance of Arctic sea ice with the North Pole at its centre where the expansion of an area where the Sun is constantly out of sight expands from the September Equinox to the December Solstice and declines after that with a temperature lag mirroring the creation and disappearance of sea ice.

It is neither good nor pleasant to experience exasperation but then again I am not contending with RA/Dec modelers but trying to bypass them and their brexiteer like behaviour.

The missing component is gentlemen or women.

ps200306

As was pointed out to you -- that "pivoting circle of illumination off the rotational equator" is the photographic record from a satellite in geosynchronous orbit. It is an actual time lapse movie, not a simulation. If it is "in defiance of every orbital principle known and can be known" then the orbital principles you think you know are wrong. I thought my own spatial relations were bad, but you seem to have literally no concept that different frames of reference exist, let alone be able to put yourself in them.

You also continue to talk about two surface rotations of the Earth, one being the Copernican "motion in declination". This does not exist. It is nowhere to be seen in the picture below. You need to adjust your set.



You talk about exasperation yet you are the one who refuses to believe the evidence of his own eyes.

oriel36

ps200306 wrote: »

As was pointed out to you -- that "pivoting circle of illumination off the rotational equator" is the photographic record from a satellite in geosynchronous orbit. It is an actual time lapse movie, not a simulation.

An Earth with a zero degree axial inclination !!!!.

https://apod.nasa.gov/apod/ap170319.html


An 'explanation' that begins -

"Explanation: When does the line between day and night become vertical?"

When does it indeed !!!!.


I thought it was a rogue kid sitting in cubicle at NASA but it is starting to surface everywhere including Wikipedia -

https://en.wikipedia.org/wiki/Season

They even recently include an animation showing how the North/South Poles move relative to the orbital plane as Copernicus described but moving in the opposite direction to its actual motion !.

I have been dealing with this material for almost 20 years and the tendency of the careless is to half describe the dynamics of the season thereby making things worse. It shows the lack of style and class with a dozen different views thrown together without the slightest attention to physical considerations.

I know all too well how people have picked up in many of my insights and even find it quaint when they are thrown back at me in half-baked form and that is really unpleasant. From experience, people do appreciate how the surface rotation causes the Polar day/night cycle and all its effects when daily rotation and all its effects are subtracted while the RA/Dec modelers have gone completely in the opposite direction below a level of flat Earth doctrines.

Zubeneschamali

oriel36 wrote: »

An Earth with a zero degree axial inclination !!!!.

Have you ever seen a world map on a wall with North at the top?

Do you have a compulsion to tilt the map by 23.5 degrees as you pass?

Bruthal

oriel36 wrote: »

When does it indeed !!!!.

When the line in question lines up from pole to pole, acting like a line of longitude, presumably they mean.

ps200306

oriel36 wrote: »

From experience, people do appreciate how the surface rotation causes the Polar day/night cycle...

There's no such rotation. What force would produce it? The Earth's axis points a fixed direction in space.

oriel36

ps200306 wrote: »

There's no such rotation. What force would produce it? The Earth's axis points a fixed direction in space.

By definition, if the Earth's North and South Polar surface points remain fixed to an external reference point in space, they must change to the internal central Sun and parallel to the orbital plane.

If people don't do the analogy using all sides of their body to substitute for the entire surface of the Earth, they are unlikely to understand why each part of the body/ Earth faces the central object/Sun at one time or other across an orbital circuit.

Do the analogy as previously described or don't bother me -

Observers can enjoy the cause of the polar day/night cycle by analogy. If floor is the orbital plane of the Earth, their nose represents the North pole and their body represents the entire surface of the Earth, by walking/orbiting around a central object/Sun, they will come to understand the surface rotation aside from daily rotation.

Pick a fixed external point using your nose as representing the North Pole and walk around the central object/Sun while keeping your nose constantly fixed to the external point meaning you have to walk forwards, sideways, backward and then forwards again to complete the circuit. At one time or other your side, front and back will face the central/Sun so in planetary terms this is why they have a single day/night cycle at the North and South Poles and the seasons where this surface rotation combines with daily rotation.

Goodness forbid someone understood the two rotations in isolation and in combination through time lapse of Uranus (about 50 seconds in) -

https://www.youtube.com/watch?v=612gSZsplpE&t=17s

Bruthal

oriel36 wrote: »

Pick a fixed external point using your nose as representing the North Pole and walk around the central object/Sun while keeping your nose constantly fixed to the external point meaning you have to walk forwards, sideways, backward and then forwards again to complete the circuit. At one time or other your side, front and back will face the central/Sun so in planetary terms this is why they have a single day/night cycle at the North and South Poles and the seasons where this surface rotation combines with daily rotation.

Goodness forbid someone understood the two rotations in isolation and in combination through time lapse of Uranus (about 50 seconds in) -

https://www.youtube.com/watch?v=612gSZsplpE&t=17s

This central object/external point/sun, presumably at belly button level(your CG), will not be visible from the top of your analogy head at any time in your orbit, unless you stand at a fixed 23 degree angle (or some angle) throughout your orbit around this "external point", at which it will then see the central point for half your orbit.

oriel36

Bruthal wrote: »

This central object/external point/sun, presumably at belly button level(your CG), will not be visible from the top of your analogy head at any time in your orbit, unless you stand at a fixed 23 degree angle (or some angle) throughout your orbit around this "external point", at which it will then see the central point for half your orbit.

Not so. There are two surface rotations involved so the analogy refers only to the specific way the Earth orbits the Sun using the North and South polar surface points where net daily rotational velocity is zero as opposed to a maximum rotational velocity at the Equator. To all intents and purposes, the daily rotational attributes are subtracted entirely so the North and South poles represent all points on the surface if daily rotation was absent.

The central object/Sun, the floor/orbital plane, the body/Earth refers the orbital motion of the Earth to the polar day/night cycle where a sunrise happens on one equinox, the Sun stays constantly in view until the opposite equinox where the Sun turns out of view for 6 months. This actually happens -

https://www.usap.gov/videoclipsandmaps/spwebcam.cfm


In isolating the polar day/night cycle at the North and South Poles by rotational cause parallel to the orbital plane, the daily rotational inputs can be grafted in to explain the seasons and what happens at the polar regions with the North and South Poles at the centre and especially the expanding and contracting circumferences which are determined by the relationship of the Poles to the circle of illumination and to the orbital plane. I find it much easier to describe the axial inclination as a constant 66 1/2 degrees relative to the orbital plane as the Poles scribe their annual circles to the Sun.

Nobody is being asked to perceive two rotations in combination as that I believe is impossible, however, the next best thing is to account for the polar day/night cycle where the polar surface points act as beacons for the specific way the Earth orbits the Sun. In such circumstances it becomes easier to consider how the surface responds to both orbital motion and daily rotation.

As there is a surface rotation due to the specific way the Earth orbits the Sun then that rotation is unequal as it responds to the variable speed of the planet. It is this component which creates the observed inequality in the length of the natural noon cycle from one cycle to the next but this facet can wait. Presently there was no specific focus on the way the planet orbits the Sun but certain facts have emerged that requires attention and particularly with human habitation at the South Pole.

Bruthal

oriel36 wrote: »

Not so.

Explain then how the top of your head would see a point you are walking around so, if you are walking upright?

There are two surface rotations involved so the analogy refers only to the specific way the Earth orbits the Sun using the North and South polar surface points where net daily rotational velocity is zero as opposed to a maximum rotational velocity at the Equator. To all intents and purposes, the daily rotational attributes are subtracted entirely so the North and South poles represent all points on the surface if daily rotation was absent.

The sun will be visible for half the orbit due to the fixed 23 degree of the axis (pointing in same direction in space throughout the orbit) and its relative angle to the sun while orbiting the sun.

Either you are trying to make the simple complex, or are having a laugh.

Now we know there are complexities about the elliptical orbit, earth speed slowing depending on distance, and earliest sunset not matching the latest sunrise, and on and on.

But the fact remains, polar summer is due to the fixed tilted axis pointing in toward the sun. 6 months later, same axial alignment in space, the opposite pole points in toward the sun. 3 months each side of that, both poles are equal distant from the sun.

Are you saying that does not happen?

oriel36

Bruthal wrote: »

But the fact remains, polar summer is due to the fixed tilted axis pointing in toward the sun. 6 months later, same axial alignment in space, the opposite pole points in toward the sun. 3 months each side of that, both poles are equal distant from the sun. Are you saying that does not happen?

So here we have modelers who insist the planet has a zero degree axial inclination and the circle of illumination pivots like a demented sea-saw off the Earth's rotational equator -

https://apod.nasa.gov/apod/ap170319.html

How do you find that description ?.

If somebody came here with a flat Earth doctrine I would ignore them and that 'explanation' above is by many, many magnitudes worse yet it was done by NASA and has recently exploded into circulation.

It spares me a lot of effort as I go on to describe the great Polar day/night cycle with one sunrise and sunset annually on the equinoxes and where the Sun is either entirely in view or out of sight for 6 months. Added to this is an expanding or contracting circumference where the Sun is constantly in view or out of sight as the Poles turn parallel to the orbital plane at a fixed distance to the orbital plane.

Maybe you and the other guys can argue whether the Earth has a zero degree inclination or is tilted but it is far beneath what I need for a discussion on the links between the motions of the planet and Earth sciences.

Bruthal

oriel36 wrote: »

So here we have modelers who insist the planet has a zero degree axial inclination and the circle of illumination pivots like a demented sea-saw off the Earth's rotational equator -

https://apod.nasa.gov/apod/ap170319.html

How do you find that description ?.

The video is spot on for a geo satellite which must orbit above the equator. What you see is exactly what is expected.

The camera is looking perpendicular (side on) to the earths axis. Simple really.

If you fix a camera on the axis of a wheel, with the camera pointing at the wheel, the wheel will appear still even at 100kph.
Does that mean its some modelers claiming that the road is moving around the wheel?

Bruthal

oriel36 wrote: »

Maybe you and the other guys can argue whether the Earth has a zero degree inclination or is tilted but it is far beneath what I need for a discussion on the links between the motions of the planet and Earth sciences.

OK, try drop to our level temporarily, are the polar seasons, 24 hours daylight/darkness due to the axis tilt.

Yes or no.

oriel36

Bruthal wrote: »

The video is spot on for a geo satellite which must orbit above the equator. What you see is exactly what is expected.

The camera is looking perpendicular (side on) to the earths axis. Simple really.

Thank you for responding as the question is whether the Earth has a zero degree inclination and the circle of illumination pivots off the Equator. It includes the 'explanation' -

"Explanation: When does the line between day and night become vertical? Tomorrow. Tomorrow is an equinox on planet Earth, a time of year when day and night are most nearly equal." NASA

https://apod.nasa.gov/apod/ap170319.html

At the North Pole on the Equinox, polar dawn had begun about 6 weeks earlier in February so no, day and night are not equal on the Equinox as it was constant daylight at the Pole a number of weeks before Polar sunrise . The issue is isolating the Polar day/night cycle by cause and such traits as extended dawn and twilight preceding and following the single Polar sunrise and sunset each equinox.

Thanks again for responding with clarity, dealing with RA/Dec modelers is like Brexiteer politics - a lot of contrived fuss that is unproductive and goes nowhere.

God forbid I discussed the issue further such as why the Sun appears to track in opposite directions at either Poles -

https://www.youtube.com/watch?v=okw6Mu3mxdM

https://www.youtube.com/watch?v=xOCCSegL8ic


The celestial sphere bubble RA/Dec which modelers have created for themselves is remarkably crude like the views brexiteers have of world politics and a lazy forum in tow. I simply wouldn't waste time as the pivoting circle of illumination is an assault on the eyes of any reasonable person.

Bruthal

Was that a yes or no?

Bruthal

oriel36 wrote: »

I simply wouldn't waste time as the pivoting circle of illumination is an assault on the eyes of any reasonable person.

Yet is simple for any rational person when they consider the view from a geo orbit.

oriel36

Bruthal wrote: »

OK, try drop to our level temporarily, are the polar seasons, 24 hours daylight/darkness due to the axis tilt.

Yes or no.

The Polar day/night cycle is separate in cause to the 24 hour day/night cycle hence no seasons, just a single cycle at the North and South Poles where the Sun is constantly in view for 6 months or out of sight at either Pole with a single extended dawn and twilight before and after the Equinox and a single sunrise and sunset on the Equinoxes with each orbit of the Sun.

I can't drop to your level as Polar 'seasons' doesn't correspond to experiences by inhabitants at the South Pole in terms of daylight and darkness. It only permits the orbital equivalent of the daily day/night cycle where your location exits the circle of illumination at sunrise on one equinox, crosses the illuminated face of the Earth and re-enters the circle of illumination at sunset on the opposite equinox with noon as a midpoint on the Solstice.

At the North Pole, sunrise is on the March Equinox, Polar noon is on the June Solstice and Polar sunset is on the September Equinox.

How the North Pole crosses from Polar noon on the June Solstice and passes re-enters the circle of illumination on the September Solstice doesn't involved a pivoting circle f illumination type not a tilted Earth type.

https://www.youtube.com/watch?v=-OgLCH7jYp8

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif

This is for people who can appreciate the Polar day/night cycle in isolation rather than attacking those who have other things going, after all, when daily rotation is added, things do become more interesting.

Thanks again for sparing me the wasted effort, that is the best I can do.

oriel36

Bruthal wrote: »

Yet is simple for any rational person when they consider the view from a geo orbit.

The seasons are a function of both daily rotation and its inclination along with the orbital surface rotation component which means a circle of illumination always perpendicular to the orbital plane.

http://www.nasa.gov/sites/default/files/thumbnails/image/pia00134.jpg

The moon's circle of illumination always runs parallel with the Earth so assigning the moon an annual pivoting circle of illumination to match the Earth is vomit inducing beyond words.

Even I have my limits dealing with celestial sphere enthusiasts and the emergence of a new breed willing to suit RA/Dec software like Stellarium. It represents the deterioration of astronomy and Earth sciences to a wasteland.

I cannot descend to your level as it has no bottom and ultimately a waste of the human mind and perceptions.

Bruthal

oriel36 wrote: »

circle of illumination always perpendicular to the orbital plane.

Well any sphere facing a star has that. Hardly some mystery only understandable for the elite mind.

http://www.nasa.gov/sites/default/files/thumbnails/image/pia00134.jpg

The moon's circle of illumination always runs parallel with the Earth so assigning the moon an annual pivoting circle of illumination to match the Earth is vomit inducing beyond words.

Its a still photo of a planet and moon. You expect to see something different in terms of lighting?

Even I have my limits dealing with celestial sphere enthusiasts and the emergence of a new breed willing to suit RA/Dec software like Stellarium. It represents the deterioration of astronomy and Earth sciences to a wasteland.

I cannot descend to your level as it has no bottom and ultimately a waste of the human mind and perceptions.

You are good at making the simple complex. A sort of AI.

oriel36

Bruthal wrote: »

Well any sphere facing a star has that. Hardly some mystery only understandable for the elite mind.

Yet you affirmed that this circle of illumination pivots off the equator as a means to 'explain' the seasons along with a zero degree axial inclination !

https://apod.nasa.gov/apod/ap170319.html

What you call simple is really crude beyond words, something not even a flat Earth proponent would descend yet you can't tell what is actual from what is fabricated to suit RA/Dec modeling.

I choose not to deal with such convictions for the same reason Galileo recognised it as something less than individual reasoning -

"I have heard such things put forth as I should blush to repeat--not so much to avoid discrediting their authors (whose names could always be withheld) as to refrain from detracting so greatly from the honor of the human race. In the long run my observations have convinced me that some men, reasoning preposterously, first establish some conclusion In their minds which, either because of its being their own or because of their having received it from some person who has their entire confidence, impresses them so deeply that one finds it impossible ever to get it out of their heads. Such arguments in support of their fixed idea as they hit upon themselves or hear set forth by others, no matter how simple and stupid these may be, gain their instant acceptance and applause. On the other hand whatever is brought forward against it, however ingenious and conclusive, they receive with disdain or with hot rage--if indeed it does not make them ill." Galileo

Galileo sought acceptance among academics, clergy and the politicians but it was never going to happen.

The same here as a demonstration for the cause of the Polar day/night cycle does not beg acceptance from any particular group or individual apart as it exists alone using experiences and observations whether they are Earth-bound or from space without the slight distortion and this is the way the Earth looks on the Solstices and Equinoxes with a vertical circle of illumination implied -

https://www.youtube.com/watch?v=-OgLCH7jYp8

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:EpicEarth-Globespin-tilt-23.4.gif


Thanks for signalling your views on the NASA explanation as anything else I describe will not make a difference.

Bruthal

oriel36 wrote: »

Yet you affirmed that this circle of illumination pivots off the equator as a means to 'explain' the seasons along with a zero degree axial inclination !

https://apod.nasa.gov/apod/ap170319.html

ps200306

I've given up trying to figure out what the hell he's trying to say. As far as I'm concerned it's elementary school science intentionally obfuscated to gain attention.

Bruthal

ps200306 wrote: »

I've given up trying to figure out what the hell he's trying to say. As far as I'm concerned it's elementary school science intentionally obfuscated to gain attention.

The absolute simple made unintelligible.

Bruthal

oriel36 wrote: »

Yet you affirmed that this circle of illumination pivots off the equator as a means to 'explain' the seasons along with a zero degree axial inclination !

https://apod.nasa.gov/apod/ap170319.html

Look at this helicopter. Flying but somehow its the world around it rotating, with the blade staying still

https://www.youtube.com/watch?v=Pu48f7s5Ru8

A bit harder to understand than a geo cam perhaps, especially with the cyclic seen in it. Or perhaps it is not cyclic, but the horizon tilting back and forth as well...

oriel36

All this becomes personal again so easy to continue without the 'pivoting circle of illumination/zero degree axial inclination' mob that emerged recently in response to RA/Dec software modeling. I have made my view known that it is many magnitudes worse than a flat Earth ideology as it manipulates imaging to suit a version of a wandering Sun across the Earth's equator on the Equinoxes.

http://community.dur.ac.uk/john.lucey/users/solar_year.gif

https://apod.nasa.gov/apod/ap170319.html

Ireland was once known for its learning and fairness but has adopted English intellectual pretense recently.


https://www.timeanddate.com/sun/norway/hammerfest

I worked in Hammerfest so as the North pole turns parallel to the orbital plane and therefore closer to the planet's circle of illumination, the circumference where the Sun is out of sight starts to shrink until it disappears at Polar sunrise on the March equinox. There are two surface rotations involved so Hammerfest will experience a rapid increase in daylight length as opposed to latitudes closer to Irish latitudes where daylight/darkness asymmetries are less severe.

It is always difficult to leave an Irish forum where the contributors have this allegiance to English clockwork modeling and now made worse by computer software. Considering our astronomical heritage stretching back to remote antiquity, there is no sign of gentleman behaviour or even individual reasoning abilities much less the perceptive/intuitive abilities all astronomers require.

Capt'n Midnight

Bruthal wrote: »

Look at this helicopter. Flying but somehow its the world around it rotating, with the blade staying still

https://www.youtube.com/watch?v=Pu48f7s5Ru8

A bit harder to understand than a geo cam perhaps, especially with the cyclic seen in it. Or perhaps it is not cyclic, but the horizon tilting back and forth as well...

AFAIK front and centre is the famous Jesus nut. Edit - no it's this one

When a helicopter is moving forward blades travel faster advancing than when they they are going back. Faster generally means more lift so they reduce the tilt angle of incidence to compensate as otherwise the helicopter would flip over.

Capt'n Midnight

ps200306 wrote: »

I've given up trying to figure out what the hell he's trying to say. As far as I'm concerned it's elementary school science intentionally obfuscated to gain attention.

No mention of the changes in eccentricity, axial tilt, and precession like in the Milankovitch cycles either.

Bruthal

Capt'n Midnight wrote: »

AFAIK front and centre is the famous Jesus nut. Edit - no it's this one

When a helicopter is moving forward blades travel faster advancing than when they they are going back. Faster generally means more lift so they reduce the tilt angle of incidence to compensate as otherwise the helicopter would flip over.

They usually use flapping for the compensation of dissemetrical lift when flying forward. Flap up, and it's in effect moving against the induced downward flow, thus reducing lift. Opposite on other side. The video also shows cyclic feathering. A hovering helicopter can have same effect with winds. The winds also move the induced flow air, thus causing a hovering helicopter to climb if wind increases.

Not much point in getting too detailed if the op couldn't see a fixed geo cam taking a pic each day at an edge on view of the day/night border as being perfectly correct as showing the seasonal lit area advance north and south.

Bruthal

Another interesting one on the helicopter in video. It looks like it's hovering on the spot. When they do this, the tail rotor counteracting the main rotor torque, also causes the helicopter to move sideways as a whole because of its sideways thrust, so some cyclic roll input is required to counteract it. So they hover on the spot with a slight off level attitude or tilt to counteract this sideways thrust.

Anyway, back to astronomy.

oriel36

https://www.timeanddate.com/sun/norway/hammerfest

In a few days, Hammerfest will see the Sun for the first time since November 23rd 2019 as the circumference where the Sun is completely out of sight begins to shrink towards the North polar latitude. At the North Pole the observation is most dramatic as there is just a single day/night cycle with one sunrise on the March Equinox and one sunset on the September Equinox.

At the North and South Poles, the daily rotational velocity reaches zero in comparison to the maximum 1037.5 mph rotational velocity at the Equator so , it follows that the polar day/night cycle and the rotation of the Poles (and by association the entire surface of the Earth) across the fully illuminated face of the Earth over a 6 month period comes from its orbital motion.

One of the loveliest features is that the Sun tracks from right to left at the South Pole and from left to right at the North polar latitudes -

https://www.youtube.com/watch?v=xOCCSegL8ic

https://www.youtube.com/watch?v=okw6Mu3mxdM


The Earth not only orbits the Sun but orbits in a specific way and this is the point of departure for isolating the single day/night cycle experienced by all locations on Earth when daily rotation and all its effects are subtracted. People who can't recognise this will also not recognise the single day/night cycle at the North and South Poles and the cause of that cycle.


Strip things bare by dynamical cause and then work in experiences and observations from the surface of the planet.