[douglips]

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.

You get that it's not going at right angles to the horizon, right?

The sun is not moving straight up from the horizon. It moves at an angle depending on your latitude and the time of year.

As a pilot you understand headwind and crosswind components. The sun is moving at 15 degrees per hour (wind speed). The speed that the sun crosses the horizon at is the headwind component, and the angle from runway heading is your latitude + some correction for the season if not on an equinox.

On the equinox, the angle the sun is making is just your latitude. You take the cosine of the angle, multiply by the wind speed, and that is your headwind component. At the equator, it crosses the horizon at 15 degrees per hour. At 45 degrees latitude, it's crossing at about 2/3 that rate. At 60 degrees latitude, it's crossing at half that rate.

[Dr David Thork]

The wind doesn't effect the sun. This is a stupid analogy.

You are willfully ignoring the fact that the sun is not travelling a uniform 15 degrees per hour through the sky as we observe it. And that is evidenced by looking at 6 degree intervals and seeing they are not the same time frame apart.

Ergo we observe the sun climbing into the sky, gathering pace (crossing more degrees per hour) and then slowing down again at sunset. Its right there. Check the numbers with any weather station you like, any place in the world you like, on any day you like. The sun is not 'moving at 15 degrees per hour, always,  for all observers.'.

[Tom Haws]

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

BT, I don't really like to do this. I do not doubt that you are a mature person with great talents. And I am grateful that you are willing to participate. It's better than dead silence, I suppose. But there is a serious problem with your contributions to this conversation. You are saying a lot of embarrassing things. Before continuing to contribute in discussions with uncommonly clear thinkers like JocelynSachs, douglips, and CuriousSquirrel, please take honest self-inventory of your ability to understand what they are saying and to talk on their level.

• Please be honest about your ability to do math
• Please be honest about your ability to do physics
• Please be honest about your willingess and ability make and record rigorous observations

It's not a good sign that you do not grasp the importance of the difference between the sun appearing to orbit the earth and the sun being asserted to glide above the earth. And it's not a good sign that you are not able to graciously admit your math mistake. If you had admitted it and conceded the point, we would be more inclined to listen to you. A bit of humility would go a long way.

[Tom Haws]

The wind doesn't effect the sun. This is a stupid analogy.

It is not objectively a stupid analogy. And since you know it's an analogy, you know it's immaterial that "the wind doesn't affect the sun". The fact that you don't like what douglips is saying doesn't make him wrong. His analogy was a gracious attempt to help you understand the problem. If in fact you understand the problem very well and need no help, simply demonstrate your understanding a little better.

You are willfully ignoring the fact that the sun is not travelling a uniform 15 degrees per hour through the sky as we observe it.

We are not ignoring the fact that we have no idea what the sun is really doing. We are asserting that the sun appears to orbit the earth at 15 degrees per hour as observed since the beginning of recorded observations. This is not in dispute. Your next-door neighbors can corroborate it. This is not a NASA trick. Take the time to make your own sundial and record your observations.

And that is evidenced by looking at 6 degree intervals and seeing they are not the same time frame apart.

Sorry. This is not likely to be true. But I need a bit more clarity about your exact assertion. If you want, I will be happy to make any observations about this you suggest. I am self-employed and available at all hours of the day and night to record sun/moon/star angles at my house. Just give me precise instructions so I can repeat your observations.

[Curious Squirrel]

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.

(Snipped for brevity)

Ah, they had both agreed upon that point, so I thought it safe to assume without running the numbers myself, thanks Tom. A difference that significant is STILL definitely large enough everyone should be long aware of it though.

[devils advocate]

On a round earth, people in the southern hemisphere's clocks should go backwards! FET 4 the win.

I can't tell if you are serious here or this is an example of that great British wit?

[Dr David Thork]

We are not ignoring the fact that we have no idea what the sun is really doing. We are asserting that the sun appears to orbit the earth at 15 degrees per hour as observed since the beginning of recorded observations. This is not in dispute. Your next-door neighbors can corroborate it. This is not a NASA trick. Take the time to make your own sundial and record your observations.

Why is this so hard for you? Why do you keep asking about my maths and physics when you struggle with plain English?

The sun does not cross the sky uniformly at 15 degrees per hour.

Let that sink in. Now fully understand that before you try to wrap your head around the incredibly difficult proof of that assertation.

The sun's speed changes through out the day from the perspective of the individual observer. Wait for it. Wait for it. You can verify this by looking at sunrise and sunset times and the times it takes the sun each day to travel through 6 degrees.
http://www.ukweathercams.co.uk/sunrise_sunset_times.php

so in the case of London today ...

Sunset:   15:52:34
Dusk - civil twilight ends   16:32:42
Nautical twilight ends   17:15:52
Astronomical twilight ends   17:56:40



Please note, the sun doesn't do each 6 degrees in the same time period. It isn't linear. Ergo, the sun isn't doing 15 degrees per minute. In fact it took almost 1 hour and 43 minutes for the sun to do 15 degrees over London at sunset today. It took, two hours, 4 minutes and 6 seconds to pass 18 degrees. 

This is just simple addition and subtraction. I'm not trying to bamboozle you with numbers here.

[Dr David Thork]

On a round earth, people in the southern hemisphere's clocks should go backwards! FET 4 the win.

I can't tell if you are serious here or this is an example of that great British wit?

The former. Southern hemisphere clocks are supposed to go the other way on a round earth.
Bolivia tried to swap their clocks around as they were sick of Northern-hemisphere hegemony.
http://www.bbc.co.uk/news/world-latin-america-28013157

How are you going to argue earth is round, when I know more about round earth theory than you?

[Curious Squirrel]

We are not ignoring the fact that we have no idea what the sun is really doing. We are asserting that the sun appears to orbit the earth at 15 degrees per hour as observed since the beginning of recorded observations. This is not in dispute. Your next-door neighbors can corroborate it. This is not a NASA trick. Take the time to make your own sundial and record your observations.

Why is this so hard for you? Why do you keep asking about my maths and physics when you struggle with plain English?

The sun does not cross the sky uniformly at 15 degrees per hour.

Let that sink in. Now fully understand that before you try to wrap your head around the incredibly difficult proof of that assertation.

The sun's speed changes through out the day from the perspective of the individual observer. Wait for it. Wait for it. You can verify this by looking at sunrise and sunset times and the times it takes the sun each day to travel through 6 degrees.
http://www.ukweathercams.co.uk/sunrise_sunset_times.php

so in the case of London today ...

Sunset:   15:52:34
Dusk - civil twilight ends   16:32:42
Nautical twilight ends   17:15:52
Astronomical twilight ends   17:56:40



Please note, the sun doesn't do each 6 degrees in the same time period. It isn't linear. Ergo, the sun isn't doing 15 degrees per minute. In fact it took almost 1 hour and 43 minutes for the sun to do 15 degrees over London at sunset today. It took, two hours, 4 minutes and 6 seconds to pass 18 degrees. 

This is just simple addition and subtraction. I'm not trying to bamboozle you with numbers here.

Once again, you're confusing the planes of motion being discussed. If you can't figure out the difference between the one you keep mentioning and the one where the sun is moving 15 degrees an hour, I'm not sure how to help you.

Look at your numbers again though. Even those show it progresses at a fairly standard rate along that axis of motion. ~40 minutes of each twilight period. This should not be the case for a flat Earth. Each section should take not insignificantly longer than the one before it when setting.

[Dr David Thork]

Once again, you're confusing the planes of motion being discussed. If you can't figure out the difference between the one you keep mentioning and the one where the sun is moving 15 degrees an hour, I'm not sure how to help you.

I'm not confusing anything. I was told by you lot

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

And then told

We are asserting that the sun appears to orbit the earth at 15 degrees per hour as observed since the beginning of recorded observations.

Now having shown above an OBSERVATION that, disproves that using one's eyes and the ability to time something, how have people been able to OBSERVE this since the beginning of recorded observations? You are using a theory - the sun travels at a uniform speed 360 degrees, divide that by 24 and 15 degrees per hour. These assumptions are based on a round earth. I'm showing you there is no such observation, it is round earth theory, and telling you with real world proofs that the sun's speed isn't uniform over the sky as we all observe every day.

Where is your real world proof that the sun's speed is uniform?

[Dr David Thork]

Look at your numbers again though. Even those show it progresses at a fairly standard rate along that axis of motion. ~40 minutes of each twilight period. This should not be the case for a flat Earth. Each section should take not insignificantly longer than the one before it when setting.

On a flat earth it would. We assume the sun to be relatively close and have a dramatic slant angle to contend with, stretching out the time it takes for the sun to travel through arc radians of the sky.

You are stuck with the Galilean bastardization that says the sun is so far away as to make that change negligible. To you the sun is always 93 million miles away. To us, it has to get some 40,000km away at its furthest and be just 3000 miles overhead at its shortest. We aren't the ones with an inconsistency here. We are observing what we expect for a flat earth. You are expecting 15 degrees per hour and you aren't getting it.

[Tom Haws]

• Sunrise is when the sun comes up.
• Civil dawn twilight is 6 degrees earlier.

A. Please provide a reference for this assertion.

B. Please clarify whether you mean that i) 6 degrees below the horizon is civil dawn twilight or that ii) 6 degrees  of rotation before dawn is civil dawn twilight.

If i), I point out that depending on the sun's apparent path for the day and location, the 6 degrees below the horizon may comprise many more degrees of the sun's path.

If ii), I dispute your assertion.

Anyway, once the sun rises, it traverses 15 degrees every hour, and the length of the day is directly proportional to the number of degrees between sunrise and sunset on that day at that location.

[Dr David Thork]

No, go and look up the definitions yourself. Understand what those things are. I pasted a big blue diagram above already. Its not hard.

[Tom Haws]

You are expecting 15 degrees per hour and you aren't getting it.

That's where you are wrong and thousands of years of sundials disagree with you. Give us a clear and repeatable experiment to run at our houses to falsify our assertion or yours.

[Tom Haws]

No, go and look up the definitions yourself. Understand what those things are. I pasted a big blue diagram above already. Its not hard.

It's not hard, but you are still missing that the sun does not rise vertically. It often and in many places traverses the 6 twilight degrees on a slant that comprises more than 6 degrees of its own path. How do you presume to school us about something that seems to be so hard for you to grasp?

[devils advocate]

Hang on are we missing something obvious here.

I stand still facing a road that crosses my path left to right and is perfectly straight.
A car travels along it left to right at a uniform speed of 70mph.
I can see the car from 2 miles either side.

Surely the car will appear to move quicker when it is closer to me (directly in front if me it will whizz past)

Does this not show that an object moving at a uniform speed can appear to speed up and slow down?

[Dr David Thork]

You are expecting 15 degrees per hour and you aren't getting it.

That's where you are wrong and thousands of years of sundials disagree with you. Give us a clear and repeatable experiment to run at our houses to falsify our assertion or yours.

I already showed you, sundials are not 15 degrees per hour marker.
Look at this bad boy.

Are you going to tell me the 1 and 12 are the same distance apart as the 8 and 9? That is not 15 degree increments. That thing is accounting for slant angles.

Hang on are we missing something obvious here.

I stand still facing a road that crosses my path left to right and is perfectly straight.
A car travels along it left to right at a uniform speed of 70mph.
I can see the car from 2 miles either side.

Surely the car will appear to move quicker when it is closer to me (directly in front if me it will whizz past)

Does this not show that an object moving at a uniform speed can appear to speed up and slow down?

On a flat earth yes. The sun will shoot overhead faster, its closer as we observe. But you are a round earther, remember? The sun is always 93 million miles away. You can't claim a slant angle. to you the sun is 93 million miles away when its overhead, and 93 million miles away at sunset. Travelling in a perfect circle. At a uniform pace. 15 degrees per hour. Every hour.

Imagine your road is a perfect circle around you 100 metres away. Now, does the car speed up when you look at 80 degrees or 20 or 170? Nope, it keeps laping exactly the same pace.

I just gave you all enough rope to hang yourselves.

[devils advocate]

How are you going to argue earth is round, when I know more about round earth theory than you?

Haha I have never claimed to know anything dude that's why I love being here because it fills in the knowledge I declined during my mandatory education.

My stance has always been from a point of ignorance and whilst that is embarrassing I take the hit as it allows me to learn.

There are no stupid questions, only stupid answers (although why is a cucumber a penguins  IS a fuc***in stupid question but you get my point)

The trouble is that the RE geeks here provide better answers, often FE answers are nonexistent, rude or nonsense whilst FE provide continuous explanation. They don't just say- go read Hawkings etc

You are however providing hope BT that there is a FE prepared to explain using science (rather than biblical or magic perspective) so I thank you for that!

DA

[Dr David Thork]

How are you going to argue earth is round, when I know more about round earth theory than you?

Haha I have never claimed to know anything dude that's why I love being here because it fills in the knowledge I declined during my mandatory education.

My stance has always been from a point of ignorance and whilst that is embarrassing I take the hit as it allows me to learn.

There are no stupid questions, only stupid answers (although why is a cucumber a penguins  IS a fuc***in stupid question but you get my point)

The trouble is that the RE geeks here provide better answers, often FE answers are nonexistent, rude or nonsense whilst FE provide continuous explanation. They don't just say- go read Hawkings etc

You are however providing hope BT that there is a FE prepared to explain using science (rather than biblical or magic perspective) so I thank you for that!

DA

I'm happy to play dumb as round earthers refuse to provide any evidence. They'll ask me for links and images all day and calculations and references. They tend to be lazy sods and rarely want to put their own necks on the line. Once I've eeked a bit out, then I'll use their assumptions against them. I've been a member of the flat earth society for about 8 years I think, maybe 9 and have well over 40,000 posts on these forums. I've had every conversation, I know your next objection before you post it and know my response. And I know all kinds of little nuggets like southern hemisphere clocks going backwards. Got to know all your RET stuff in case you surprise me with it.

[JocelynSachs]

No, go and look up the definitions yourself. Understand what those things are. I pasted a big blue diagram above already. Its not hard.

Get two nice straight garden canes and a sunny day.

Push one garden cane into the soil such that it has no visible shadow (pointing at the sun)

Wait 1 hour.

Push the second cane into the soil such that it crosses the other one and has no visible shadow (pointing at the sun)

Measure the angle between the canes. It will be 15 degrees. If you prefer, wait two hours - it'll be 30 degrees. Or three hours - it'll be 45 degrees. It doesn't matter where you are on earth, and so long as the sun is visible and not covered with clouds at both ends of the experiment, it doesn't matter when you do it either.

The timings you are talking about, with the aid of your excellent diagram, are degrees measured vertically above the horizon, not the angle across the sky the sun appears to travel during a given time.

As for the sundial: you are quite correct that angled fins distort the path of the shadow. As I mentioned earlier: the other type of sundial, which is angled to align with the polar axis and thus present an undistorted shadow projection, has the hours spaced 15 degrees apart.