[Tom Haws]

A quick search of the site for the terms "sundial" and "dial" reveals little "dial"ogue on the subject. But this site's model of the sun cannot operate all sundials correctly. I'm including the following images:

1. A working sundial located in Singapore

2. An animation of a generic equatorial sundial with a flat dial.

3. The FES Sun animation.

4. The FES seasons illustration

To make a sundial work the way it works, the Sun must be apparently traversing a constant speed arc across the sky. For a given point on earth, there are various ways this could work, including a) the sun orbiting the earth, b) the earth rotating on its axis, and c) the sun passing overhead at variable speed. But for all points on earth, this cannot work by method c.

The FES Sun animation does not make the sun apparently traverse a constant speed arc across the sky. And of course undulations necessary for the moon phases complicate the problem.

Sundials come in many designs, and sundials have been used for over 3000 years. Consider this sundial with a curved dial located in Singapore, almost at the equator. Also consider the generic equatorial sundial animation. Both required the Sun to traverse the apparent constant speed (tangential or angular) arc.

1. A working sundial located in Singapore


2. An animation of a generic equatorial sundial with a flat dial.


3. The FES Sun animation.


4. The FES seasons illustration

[Dr David Thork]

I'm sorry, if you can't see how the flat earth makes the concept of a clock even easier, I'm not going to be able to point that out to you. You even show an animated sun keeping time as it travels around a flat earth's face. The sun even goes the same direction as a clock ... clockwise! North and south hemisphere. On a round earth, people in the southern hemisphere's clocks should go backwards! FET 4 the win.

[Tom Haws]

Thanks for your answer, BT.

I'm sorry, if you can't see how the flat earth makes the concept of a clock even easier, I'm not going to be able to point that out to you. You even show an animated sun keeping time as it travels around a flat earth's face. The sun even goes the same direction as a clock ... clockwise! North and south hemisphere. On a round earth, people in the southern hemisphere's clocks should go backwards! FET 4 the win.

BT, I don't want to get into a boasting contest with you. But in this case, I better verify before proceeding. How good is your working knowledge of basic trigonometry? Can you answer the following math questions pretty easily?

1. If you are standing 100 meters from a straight road facing straight toward a car that is traveling past you on the road at 10 meters per second, how long will it take for you to turn as you follow the car from 80 degrees left of perpendicular to 70 degrees left of perpendicular?

2. If you are standing 100 meters from a straight road facing straight toward a car that is traveling past you on the road at 10 meters per second, how long will it take for you to turn as you follow the car from 20 degrees left of perpendicular to 10 degrees left of perpendicular?

We really need to make sure to have this discussion among people who can answer those two questions correctly. Real answers. Correct numbers.

[Dr David Thork]

As I mentioned in an earlier thread, I did a degree in Aerospace engineering. I did trigonometry at school when I was 13. I also know how to use a computer.
https://www.wolframalpha.com/

1. 1.9 seconds.

2. I'm not going to dignify this with an answer. Its the same maths.

We really need to make sure to have this discussion among people who can answer those two questions correctly. Real answers. Correct numbers.

I'm not here to prove anything to you. If you want to know where to find answers, I'll help. But I couldn't give two hoots what shape you think earth is.

[Tom Haws]

1. 1.9 seconds.

I got 29.2 seconds. Do I need to check my math?

[douglips]

I'm sorry, if you can't see how the flat earth makes the concept of a clock even easier, I'm not going to be able to point that out to you. You even show an animated sun keeping time as it travels around a flat earth's face. The sun even goes the same direction as a clock ... clockwise! North and south hemisphere. On a round earth, people in the southern hemisphere's clocks should go backwards! FET 4 the win.

The sun moves at a constant 15 degrees per hour, for all observers, at all points on Earth.

That is a very different notion from the notion of a clock.

Tom Bishop's answer to this is that if an object is far enough away, the change in its angular velocity goes to zero. I see zero evidence for this hypothesis, but at least it's internally consistent.

Do you not see the problem with the flat earth model here?

Unless Tom's special angular velocity idea is a real thing, in the flat earth model when the sun is directly overhead its apparent angular velocity will be much higher than when it is near sunset.

This contradicts the observation that the sun is always moving at 15 degrees per hour, always, for all observers.

[Dr David Thork]

1. 1.9 seconds.

I got 29.2 seconds. Do I need to check my math?

If a road was just 100 metres away from you, does it seem likely it would take 30 seconds to travel such a short distance? I could run the full 100 metres in less than that and be stood on the road before your car traveled just 10 degrees closer from the datum.

The sun moves at a constant 15 degrees per hour, for all observers, at all points on Earth.
That is a very different notion from the notion of a clock.

Very different? A clock is geared 2:1. The hour hand is geared to do two revolutions per day. This is to make the minute hand a thing people can wrap their heads around. 24 doesn't go into 60 very neatly, and a minute is an arbitrary unit of time based solely on picking a number that you can divide in your head easily. A 24 hour clock would be very easy to make, but you'd have to know that when the little hand is pointing at the 17, that is 42.5 minutes past the hour.

Tom Bishop's answer to this is that if an object is far enough away, the change in its angular velocity goes to zero. I see zero evidence for this hypothesis, but at least it's internally consistent.

Do you not see the problem with the flat earth model here?

Unless Tom's special angular velocity idea is a real thing, in the flat earth model when the sun is directly overhead its apparent angular velocity will be much higher than when it is near sunset.

This contradicts the observation that the sun is always moving at 15 degrees per hour, always, for all observers.

Well a sundial also contradicts that the sun moves 15 degrees per hour for all observers. 

Are those hour lines all 15 degrees? I guess Tom knows what he is talking about and you don't even know how a sun dial works.

[JocelynSachs]

I get 29.2 seconds as well.

If you're 100 metres from the road and you're facing 80 degrees from perpendicular in order to look straight at a car, that car is:

100 * Tan(80) = 567.12 metres down the road.

If you turn to watch it, then when you're facing 70 degrees from the perpendicular, the car is:

100 * Tan(70) = 274.75 metres down the road.

Since the car is travelling at 10m/s, it will have taken (576.12-274.75)/10 = approx 29.2 seconds to travel that distance.

For the second question, it's Tan(20) and Tan(10). I get approx 1.88 seconds.

Are those hour lines all 15 degrees?

Yes, they are. The spacing of the numerals around the outer edge is irregular because the centre of the rays isn't at the centre of the outer circle, so they are more bunched up where they cross the nearside edge than when they reach the far edge. But the rays themselves are at 15 degree intervals. A quick google image search will show you examples of sundials where the fin is central to the outer circle, and on those you can see the numerals are evenly spaced.

(Edit to substitute 'approx' for tilde, as the font here doesn't seem to display tilde properly and shows it as minus)

[Dr David Thork]

Sorry, I answered question two instead of one.

Why the hell does this matter anyway?

Yes, they are. The spacing of the numerals around the outer edge is irregular because the centre of the rays isn't at the centre of the outer circle, so they are more bunched up where they cross the nearside edge than when they reach the far edge. But the rays themselves are at 15 degree intervals. A quick google image search will show you examples of sundials where the fin is central to the outer circle, and on those you can see the numerals are evenly spaced.

(Edit to substitute 'approx' for tilde, as the font here doesn't seem to display tilde properly and shows it as minus)

No. A google search will show you ornamental sundials, not functioning ones. The sun does not move 15 degrees from east to west from where ever you view it. You are looking at a sundial. It is showing where the shadow falls. That shadow is not uniformly 15 degrees because the sun doesn't travel uniformly 15 degrees per hour from east to west. It is amazing that you don't even believe your eyes when entrenched in your round earth beliefs.

This is why you can find time lapse images of the sun that do this ...



How's your sundial going to deal with that with uniform lines? Sundials need calibrating for where they are located. It isn't a once size fits all solution. They need to contend with seasons, longitude and latitude (how close you are to a meridian, how far North you might be, etc.)

The sun demonstrably does not travel 15 degrees across the sky per hour as viewed by all observers. That is an irrefutable fact regardless of the shape of the earth. So lets not start from a junk premise that you think will help you prove earth is a ball.

[Curious Squirrel]

Sorry, I answered question two instead of one.

Why the hell does this matter anyway?

Because if the sun is moving at a steady linear velocity above a flat Earth, it cannot be moving at a steady angular velocity. The numbers involved in the moving car show this. It takes 15 times as long to go from 80° to 70° as it does from 20° to 10°. But we know the sun moves at the same angular velocity for all observers every day. This is an impossibility if it has a steady linear velocity, as the example with the car shows.

[Dr David Thork]

Sorry, I answered question two instead of one.

Why the hell does this matter anyway?

Because if the sun is moving at a steady linear velocity above a flat Earth, it cannot be moving at a steady angular velocity. The numbers involved in the moving car show this. It takes 15 times as long to go from 80° to 70° as it does from 20° to 10°. But we know the sun moves at the same angular velocity for all observers every day. This is an impossibility if it has a steady linear velocity, as the example with the car shows.

I just proved the sun doesn't do that.

[Curious Squirrel]

Sorry, I answered question two instead of one.

Why the hell does this matter anyway?

Because if the sun is moving at a steady linear velocity above a flat Earth, it cannot be moving at a steady angular velocity. The numbers involved in the moving car show this. It takes 15 times as long to go from 80° to 70° as it does from 20° to 10°. But we know the sun moves at the same angular velocity for all observers every day. This is an impossibility if it has a steady linear velocity, as the example with the car shows.

I just proved the sun doesn't do that.

You posted an image with no context (looks like location either far North or far South, taking a picture of the sun on the same day/time once a month for a year based on similar ones I've seen for the moon) and claim it proves the sun doesn't move a constant 15 degrees. If that's a timelapse of the sun over a day then we have a massive problem.

[JocelynSachs]

No. A google search will show you ornamental sundials, not functioning ones. The sun does not move 15 degrees from east to west from where ever you view it. You are looking at a sundial. It is showing where the shadow falls. That shadow is not uniformly 15 degrees because the sun doesn't travel uniformly 15 degrees per hour from east to west. It is amazing that you don't even believe your eyes when entrenched in your round earth beliefs.

You asked if the lines on the sundial you posted were spaced at 15 degrees. They are. If you picked the wrong image to illustrate your point, that's hardly my fault.

You're correct that sundials must be calibrated for latitude and longitude (the angle of the entire assembly in ones like this:



The latitude calibration is the same as for an equatorial telescope mount: the assembly is tilted such that the shadow-casting rod is in line with the polar axis. On the type of sundial shown above, where the shadow is cast upon a circular arc centred on the rod, the hours are marked at regular 15 degree intervals. The same way my motorised telescope's RA axis is very precisely geared to turn it at a constant 15 degrees per hour to track stars (works on the sun, too).

I've no idea what that other composite picture is you posted, but it's not a time-lapse.

[Roger G]

Sorry, I answered question two instead of one.

Why the hell does this matter anyway?

Yes, they are. The spacing of the numerals around the outer edge is irregular because the centre of the rays isn't at the centre of the outer circle, so they are more bunched up where they cross the nearside edge than when they reach the far edge. But the rays themselves are at 15 degree intervals. A quick google image search will show you examples of sundials where the fin is central to the outer circle, and on those you can see the numerals are evenly spaced.

(Edit to substitute 'approx' for tilde, as the font here doesn't seem to display tilde properly and shows it as minus)

No. A google search will show you ornamental sundials, not functioning ones. The sun does not move 15 degrees from east to west from where ever you view it. You are looking at a sundial. It is showing where the shadow falls. That shadow is not uniformly 15 degrees because the sun doesn't travel uniformly 15 degrees per hour from east to west. It is amazing that you don't even believe your eyes when entrenched in your round earth beliefs.

This is why you can find time lapse images of the sun that do this ...



How's your sundial going to deal with that with uniform lines? Sundials need calibrating for where they are located. It isn't a once size fits all solution. They need to contend with seasons, longitude and latitude (how close you are to a meridian, how far North you might be, etc.)

The sun demonstrably does not travel 15 degrees across the sky per hour as viewed by all observers. That is an irrefutable fact regardless of the shape of the earth. So lets not start from a junk premise that you think will help you prove earth is a ball.

I'm afraid the posting of the picture is not directly relevant to the discussion here. I found the details of what the photo actually is :

Sunrise Analemma (with a little extra)
Image Credit & Copyright: Tunç Tezel (TWAN)
Explanation: An analemma is that figure-8 curve that you get when you mark the position of the Sun at the same time each day throughout planet Earth's year. In this case, a composite of 17 individual images taken at 0231 UT on dates between April 2 and September 16 follows half the analemma curve. The scene looks east toward the rising sun and the Caspian sea from the boardwalk in the port city of Baku, Azerbaijan. With the sun nearest the horizon, those dates almost span the period between the 2012 equinoxes on March 20 and September 22. The northern summer Solstice on June 20 corresponds to the top of the figure 8 at the left, when the Sun stood at its northernmost declination. Of course, this year the exposure made on June 6 contained a little something extra. Slightly enhanced, the little black spot on the bright solar disk near the top of the frame is planet Venus, caught in a rare transit during this well-planned sunrise analemma project.

Roger

[Dr David Thork]

Yes, so the sun taken every single day.

Now tell me. Is it going to cast the same shadow from all those positions? And if it is moving, how does it maintain a constant 15 degrees per hour no matter where you view it from?

Being as the very time of sunrise changes every day, how is that constant no matter where you are?
The declination also changes.

Lets consider twilight times. I'll do this in baby steps because you are all acting like babies.

• Dawn is when the sun comes up.
• Civil dawn is 6 degrees earlier.
• Nautical dawn is 12 degrees before dawn.
• Astronomical dawn is 18 degrees before dawn.

Now, if the sun was moving constantly at 15 degrees per hour through the sky, you'd expect the 3 times between those 4 points in the sky to all be the exact same time between them.

But they aren't
http://www.ukweathercams.co.uk/sunrise_sunset_times.php

We aren't moving on until you all accept that the statement

the sun is always moving at 15 degrees per hour, always, for all observers.

is completely erroneous and can be shown to be so multiple ways.

[inquisitive]

Yes, so the sun taken every single day.

Now tell me. Is it going to cast the same shadow from all those positions? And if it is moving, how does it maintain a constant 15 degrees per hour no matter where you view it from?

Being as the very time of sunrise changes every day, how is that constant no matter where you are?
The declination also changes.

Lets consider twilight times. I'll do this in baby steps because you are all acting like babies.

• Dawn is when the sun comes up.
• Civil dawn is 6 degrees earlier.
• Nautical dawn is 12 degrees before dawn.
• Astronomical dawn is 18 degrees before dawn.

Now, if the sun was moving constantly at 15 degrees per hour through the sky, you'd expect the 3 times between those 4 points in the sky to all be the exact same time between them.

But they aren't
http://www.ukweathercams.co.uk/sunrise_sunset_times.php

We aren't moving on until you all accept that the statement

the sun is always moving at 15 degrees per hour, always, for all observers.

is completely erroneous and can be shown to be so multiple ways.

Meanwhile, we know the shape of the earth, WGS84, and the path of the sun.

[Curious Squirrel]

Yes, so the sun taken every single day.

Now tell me. Is it going to cast the same shadow from all those positions? And if it is moving, how does it maintain a constant 15 degrees per hour no matter where you view it from?

Being as the very time of sunrise changes every day, how is that constant no matter where you are?
The declination also changes.

Lets consider twilight times. I'll do this in baby steps because you are all acting like babies.

• Dawn is when the sun comes up.
• Civil dawn is 6 degrees earlier.
• Nautical dawn is 12 degrees before dawn.
• Astronomical dawn is 18 degrees before dawn.

Now, if the sun was moving constantly at 15 degrees per hour through the sky, you'd expect the 3 times between those 4 points in the sky to all be the exact same time between them.

But they aren't
http://www.ukweathercams.co.uk/sunrise_sunset_times.php

We aren't moving on until you all accept that the statement

the sun is always moving at 15 degrees per hour, always, for all observers.

is completely erroneous and can be shown to be so multiple ways.

It's only erroneous if you are assuming they are speaking about it in relation to the plane of the horizon, and not the plane of the sun. Hence the tilt of the sundial shown in Jocelyn's picture.

[douglips]

You can build a sundial and it will show 15 degrees per hour:


I'm amazed at this conversation.

Every day the sun moves on a slightly different path through the sky. If you live somewhere where there is winter and summer, the sun is in the sky for more hours during the summer. This is why sunrise and sunset times vary, but if you trace the path of the sun through the sky, it is moving 15 degrees per hour.
You can't look at pictures taken several days apart and make an assumption about how fast the sun moves.

Look at that sundial - you calibrate it for your latitude and it shows the sun moving equal distances per hour.
Look at it.

[Tom Haws]

The sun demonstrably does not travel 15 degrees across the sky per hour as viewed by all observers. That is an irrefutable fact regardless of the shape of the earth. So lets not start from a junk premise that you think will help you prove earth is a ball.

No, BT. A 15 degree per hour apparent sun travel is observable reality at all points on earth on all days and times. And a globe-shaped sundial pointed at the north celestial pole works everywhere at all times. See http://www.polaris.iastate.edu/NorthStar/Unit6/unit6_sub2.htm



If you have something that works better, please share.

[Tom Haws]

It takes 15 times as long to go from 80° to 70° as it does from 20° to 10°. But we know the sun moves at the same angular velocity for all observers every day. This is an impossibility if it has a steady linear velocity, as the example with the car shows.

Actually, I think JocelynSachs dropped a decimal point. I get 29.2 seconds and 18.7 seconds, with the 80 to 70 degree traversal taking 156% as long as the 20 to 10 degree traversal.

The 85 to 75 degree traversal takes 77 seconds. The 5 left to 5 right traversal takes 8.7 seconds. The first is 9 times as long as the second. If Tom Bishop can wave away the lowest 10 or 15 degrees, it helps a lot.

But the case for the Sun animation is even worse, because at equinox, as animated, the sunset sun from my house in Mesa, Arizona is traveling mostly past, not away from me.

album upload

It's at equinox


Arizona sunset 1


Arizona sunset 2