[Tom Bishop]

What?

I've long since moved past sidereal day reference frame.

I don't know what you are trying to convey. Please restate your criticism.

I don't think that the equinox could only start at Solar Noon. It was an example. Any other value offset from Solar Noon would have the same issue since Solar Noon is always a certain number of hours away from it. An offset changes the place of Solar Noon. The 24 Hour Solar Day and the Solar Year must be in sync.

Correction: The equinox does have to start at Solar Noon at some point on earth, but not necessarily your point on earth.

[Bobby Shafto]

They are in sync. Just not by a whole number. Every 356.24 solar days per 1 solar year. That "extra time" of 0.24 solar day is the ~6 hours that is the sync.

What's the problem?

My read of your id of "the problem" is the ~6 hours as if that means solar day and solar year are not in sync. But there's no reason for synchronization to be exactly 365 solar days to 1 solar year.

Equinox to same equinox takes more time than 365 solar days. The same aspect of the earth doesn't face the sun from vernal equinox to next vernal equinox. 

[Tom Bishop]

They are in sync. Just not by a whole number. Every 356.24 solar days per 1 solar year. That "extra time" of 0.24 solar day is the ~6 hours that is the sync.

What's the problem?

An hour in Mean Solar Time is the same as an hour in a stop watch. These aren't hours of different lengths from what we know.

See this Google Dictionary Definition

mean so·lar time
nounAstronomy
noun: mean solar time

    time as calculated by the motion of the mean sun. The time shown by an ordinary clock corresponds to mean solar time.

And https://www.britannica.com/science/solar-time#ref144523

Mean solar time, kept by most clocks and watches, is the solar time that would be measured by observation if the Sun traveled at a uniform apparent speed throughout the year rather than, as it actually does, at a slightly varying apparent speed that depends on the seasons.

Refer to my Equation of Time post for more on the meaning of "mean".

[Bobby Shafto]

Refer to my Equation of Time post for more on the meaning of "mean".

Red herring, Tom. Or, if not intentionally a distraction, then misunderstanding of these concepts. That's a different variance aspect (and minor compared to the 0.24 solar day shift in equinox) that you can ignore while searching for understanding the why of that 0.24 day or ~6 hr "extra time." You're off on tangents with that and precession influences.

Do you honestly want to understand? Or are you vested in debating because you are sure you've found a flaw? I'm trying to avoid debate. You act like you're trying to educate me so that I can come to your conclusion that what you're educating me about is flawed.

If you don't know why what you're referring me to is a red herring, then don't lecture me as if we're debating. I chose to engage to help you understand and resolve the conundrum you think you've identified. If you're committed to that and can't fathom that you're conflating concepts, I'm wasting my time.

[Tom Bishop]

It's not a red herring. The Solar Time hour is identical to the time in our clocks and watches, and a Solar Day is 24 Solar Time hours. It relates to the sun over one day:

https://www.britannica.com/science/solar-time#ref144523

Solar time, time measured by Earth’s rotation relative to the Sun. Apparent solar time is that measured by direct observation of the Sun or by a sundial.

A Tropical Year is 365.24 Solar Days, which is 24 Solar Hours x 365.24. Per the earlier discussion and the Recap post, this does not match up to put Solar Noon into the spot it should be at for Solar Noon.

[Bobby Shafto]

It's not a red herring. The Solar Time hour is identical to the time in our clocks and watches, and a Solar Day is 24 Solar Time hours. It relates to the sun over one day:

When "mean solar time" and "equation of time" have zero to do with understanding the "extra" 0.24 hours that you say are confounding, invoking them is a red herring. 

Those concepts matter insofar as why 0.24 hours isn't exact or why the exact value differs from year to year.

Forget that because it's not germane to comprehending the presence of the "extra time." You're either tying yourself in knots trying conflate concepts, or you're doing it intentionally to preserve a conclusion you've become invested in. I can't tell which. I want to believe you're making a sincere effort.

[douglips]

What?

I've long since moved past sidereal day reference frame.

I don't know what you are trying to convey. Please restate your criticism.

I don't think that the equinox could only start at Solar Noon. It was an example. Any other value offset from Solar Noon would have the same issue since Solar Noon is always a certain number of hours away from it. An offset changes the place of Solar Noon. The 24 Hour Solar Day and the Solar Year must be in sync.

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

Consider the number of radians in a circle. It’s 2*pi. I can assert that the number of times the radius goes into the circumference must be an integer, but I would be wrong.

You cannot just assert that solar day and solar year are related without any justification. The only justification I see from you implies that you think solar noon is a certain time (it’s not) or that you think the sun is “pointing” somewhere. Neither of these things are features of RET - they are either fundamental misunderstandings or straw men you have constructed.

[Tom Bishop]

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. You are correct. I corrected that post on how I worded that.

Start the 24 hour clock on the September Equinox point where it is 12PM Solar Noon at the point of the Equinox and it will end on ~6PM after one Solar Year. Why would it not stop at 12PM if you are in the same position on the earth's orbit around the sun, as per the diagrams?

[Bobby Shafto]

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. Correct. But start the clock on the September Equinox point where it is 12PM Solar Noon and it will end on ~6PM after one year. Why doesn't it stop at 12PM if you are in the same position on the earth's orbit around the sun?

Because at that same location (not a point, but a meridian) at the 365th solar noon, the equinox is still ~6 hours away. The earth isn't going to stop its rotating to wait. The earth keeps turning as that meridian where the solar year began (almost) a year ago sees its local solar noon pass without the solar year ending. A little under 90° of longitude to the west, the equinox occurs and it's at that meridian's solar noon that the solar year is complete.

A little less than 90° of latitude equates a little less than a quarter of a rotation, a little less than a quarter of a day (0.24), or a little less than 6 hours.

I posted this a few hours ago.

It might help Tom to distinguish it that way.

Looking up times for the next two autumnal equinoxes, 2018 occurs 01:53 UTC on Sep 23. A year later, in 2019, it occurs 07:41 UTC.

Estimating using 15° of longitude per (solar) hour, that means that in 2018, solar noon at the time of autumnal equinox will be somewhere near 150°E meridian. But in 2019, solar noon at the time of autumnal equinox will be somewhere near the 70°E meridian. 

The 365th solar noon will have passed those on the 150° meridian because the earth hasn't reached the autumnal equinox yet. It will take another 5 hrs and 48 mins to get there. Meanwhile, the earth will keep rotating with respect to the sun and the solar noon line will keep moving west for that amount of time until...equinox.

(My meridians might be off. I'm sure there's a calculator that can figure what longitude the sun is at given UTC, but I don't have a link handy. The point ought to be made, though.)

[Stagiri]

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. You are correct. I corrected that post on how I worded that.

Start the 24 hour clock on the September Equinox point where it is 12PM Solar Noon at the point of the Equinox and it will end on ~6PM after one Solar Year. Why would it not stop at 12PM if you are in the same position on the earth's orbit around the sun, as per the diagrams?

Because Earth's orbit around the Sun takes 365.24 days.

There's no need for the equinox to be always at 12 am at some (single) place.

[Tom Bishop]

Bobby, can you provide a source on the equinox not being a point, "but a meridian"? Everything I have seen says that it is a point.

http://stars.astro.illinois.edu/celsph.html

Twice a year, the Sun crosses the equator, on or about March 20 at a point called the Vernal Equinox, and on September 23 at the Autumnal Equinox (the terms derived from a northern hemisphere perspective).

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. You are correct. I corrected that post on how I worded that.

Start the 24 hour clock on the September Equinox point where it is 12PM Solar Noon at the point of the Equinox and it will end on ~6PM after one Solar Year. Why would it not stop at 12PM if you are in the same position on the earth's orbit around the sun, as per the diagrams?

Because Earth's orbit around the Sun takes 365.24 days.

There's no need for the equinox to be always at 12 am at some (single) place.

How then, does that reconcile with the 24 Hour Solar Day?

Solar Noon is always somewhere on earth. It will be somewhere on the point of the Equinox.  The Solar Day is based on the sun rotation around the earth - 24 hours per rotation.

How do you explain the incompatibility between Solar Day and the Number of Solar Days in a Solar Year? Where does the extra time come from?

[Stagiri]

(...)

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. You are correct. I corrected that post on how I worded that.

Start the 24 hour clock on the September Equinox point where it is 12PM Solar Noon at the point of the Equinox and it will end on ~6PM after one Solar Year. Why would it not stop at 12PM if you are in the same position on the earth's orbit around the sun, as per the diagrams?

Because Earth's orbit around the Sun takes 365.24 days.

There's no need for the equinox to be always at 12 am at some (single) place.

How then, does that reconcile with the 24 Hour Solar Day?

Solar Noon is always somewhere on earth. It will be somewhere on the point of the Equinox.  The Solar Day is based on the sun rotation around the earth - 24 hours per rotation.

How do you explain the incompatibility between Solar Day and the Number of Solar Days in a Solar Year? Where does the extra time come from?

Why would I need to explain it? It simply is. There's no need for days to fit exactly into one year. It's just a number we've measured of units we've decided to use.

[Stagiri]

The world record in 400m sprint is 43,03 s. Why isn't it an integer?

[Curious Squirrel]

There's no incompatibility, there's no "extra time" appearing from nowhere. Stop taking teaching tools as gospel, and think it through. You've been given all the information you need to sort this out. Multiple times and ways even.

I'm bowing out of this one I think. It's clear he doesn't wish to understand, is continuing to pretend he doesn't understand for some reason, or he never will because he somehow can't grasp basic concepts of motion. Best of luck to those who continue to try, and to you as well Tom.

[Tom Bishop]

At the point of September Equinox the sun is illuminating half of the earth.

Solar Time is 24 Hours. One Solar Day is 24 Hours.

After 365.24 Solar Days the earth has returned to the starting point on the earth's orbit around the sun, yet illuminated differently. 24 Hour Solar Clock is misaligned. Solar Noon is no longer at 12PM in Solar Time.

Can't be explained by the 20 minute Sidreal Year difference.

Big Problem.

[douglips]

Bobby, can you provide a source on the equinox not being a point, "but a meridian"? Everything I have seen says that it is a point.

He didn't say the equinox was a meridian. He said that one meridian has its solar noon about six hours before the equinox, and some other meridian has its solar noon right at the time the Earth passes the equinox point.

[douglips]

IT IS ALWAYS SOLAR NOON SOMEWHERE. This has nothing to do with sidereal anything.

It is always Solar Noon somewhere. You are correct. I corrected that post on how I worded that.

Start the 24 hour clock on the September Equinox point where it is 12PM Solar Noon at the point of the Equinox and it will end on ~6PM after one Solar Year. Why would it not stop at 12PM if you are in the same position on the earth's orbit around the sun, as per the diagrams?

Thanks for the correction.

As to your question, imagine you have a music box in your car with a ballerina on top that is spinning at a constant rate. You then drive around the block at a constant speed. Which way the ballerina is facing when you pass your house is not necessarily the same each time, unless you plan your speed very carefully.

If you got close to your house and then stopped when the ballerina was facing a certain way, you might be just short or just past your house.

The ballerina in your car doesn't know how fast you are driving and just keeps spinning.

[Bobby Shafto]

Bobby, can you provide a source on the equinox not being a point, "but a meridian"? Everything I have seen says that it is a point.

I understand how my word choice might be confusing. I just didn't want you to think that solar noon happens on a point the way equinox does.

Equinox is a point on the equator, and it's solar noon for all points along that meridian that intersects with the equator at that point. It might have been unnecessary for me to make that parenthetical but I was trying to keep clear how solar noon and equinox are related.

The difficulty I'm having is conveying to you that solar noon and equinox are the same point over the earth from equinox to equinox, 1 solar year apart. The equinox moves westward toward a new meridian where it's solar noon when the sun crosses the ecliptic (equator). It's solar noon for all of the points along that meridian but the sun is only directly overhead on the point on the equator.

[Bobby Shafto]

Correction: The equinox does have to start at Solar Noon at some point on earth, but not necessarily your point on earth.

Good edit. Does this mean you understand now where the extra time comes from?

[Bobby Shafto]

How can you post this:

Correction: The equinox does have to start at Solar Noon at some point on earth, but not necessarily your point on earth.

And then later ask this?

How then, does that reconcile with the 24 Hour Solar Day?

Solar Noon is always somewhere on earth. It will be somewhere on the point of the Equinox.  The Solar Day is based on the sun rotation around the earth - 24 hours per rotation.

How do you explain the incompatibility between Solar Day and the Number of Solar Days in a Solar Year? Where does the extra time come from?

The answer is in your correction.