Around-the-World Sailing Races?
« on: May 14, 2020, 07:27:13 PM »
I have a question for the FE community. I've searched through the forums, and while I've seen posts about circumnavigating the Antarctic continent, I've not found this topic.  If I've missed it - I apologize.  I'm a pretty serious offshore sailor.  Over 2018-19 I put 6,000 nautical miles on my sailboat.  Since 1968, about every 4 years there are around-the-world sailboat races.  Almost all leave from England.  Some are non-stop; some have a few stops at the obvious places.  The typical course is to leave England, head south to the Cape of Good Hope at the southern tip of Africa, next to Australia, then around Cape Horn at the southern tip of South America, then back to England.  There's a great documentary movie, entitled "Maiden", about the first all-female crew to accomplish this grueling feat in 1989.  Using the FE model that I typically see, the distances involved in this would be hugely greater than if the Earth is really spherical.  Given that racing sailboats only go about 15 mph on average, I would think that the participants would easily notice such a massive increase in the distances they have to travel.  How does this reality mesh with the FE model?

I also have a question about the spherical trigonometry mathematics needed to make nautical sextants work (and they do) for ocean navigation, but I'll save that for now. 

Thanks

*

Online Roundy

  • Abdicator of the Zetetic Council
  • *
  • Posts: 2199
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #1 on: May 14, 2020, 07:52:07 PM »
I disagree that it would be so easy for the sailors to notice that they're traveling a greater distance than expected; there are so many x-factors involved with sailing. I suspect they rely primarily on navigation equipment to determine what kind of distances they've covered and just trust what they're told just like everyone else; for all we know innumerable sailors involved in this race were surprised that they covered as little distance as their equipment tells them, but because RE is so ingrained, they just don't question it.
Electro-Theologist, Poet, Philosopher, Musician, Etymologist, Egyptologist, Astro-Theologist, Geocentrist, Flat Earther, and Collector of Rare Books.

Re: Around-the-World Sailing Races?
« Reply #2 on: May 14, 2020, 08:13:32 PM »
I disagree that it would be so easy for the sailors to notice that they're traveling a greater distance than expected; there are so many x-factors involved with sailing. I suspect they rely primarily on navigation equipment to determine what kind of distances they've covered and just trust what they're told just like everyone else; for all we know innumerable sailors involved in this race were surprised that they covered as little distance as their equipment tells them, but because RE is so ingrained, they just don't question it.

Can you suggest a few x-factors that aggregated would account for double or triple the length required (the outside lines of longitude on the Azimuthal FE model are easily twice the circumference of the inner ones where the UK is that the race starts)?   I find it very hard to believe it would be "so easy" to be mistaken about going two to three times more than expected.  That would require having to go two to three times the average speed since they can literally just count the days the trip takes, right?  And this would mean that lots of sailors - who are so experienced at sailing that they can travel for thousands and thousands of miles - cannot tell the difference between about 15mph and 30 or 45mph.  It's trivial to tell the difference between those two speeds in a car, but then again there are things to look at on the ground.  Even so, the surface of the ocean is not placid, so you can gauge it, if you've spent years on sailing boats . Plus, a great deal of the trip must be within sight of land, based on the description (certainly not all of it).

Additionally, if even a single person, out of the many who have done this since 1973 does not use sophisticated navigation equipment relying on the conspiracy, then that disproves the FE model in one fell swoop. Seems like kind of a high bar?  Isn't the zetetic model all about seeing for yourself?  It appears that literally anyone can do this. The website reads "Anyone, even if they have never stepped on a boat before, can join the adventure."
https://www.clipperroundtheworld.com/about/about-the-race





« Last Edit: May 14, 2020, 08:15:03 PM by existoid »

Offline ChrisTP

  • *
  • Posts: 926
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #3 on: May 14, 2020, 08:14:59 PM »
I disagree that it would be so easy for the sailors to notice that they're traveling a greater distance than expected; there are so many x-factors involved with sailing. I suspect they rely primarily on navigation equipment to determine what kind of distances they've covered and just trust what they're told just like everyone else; for all we know innumerable sailors involved in this race were surprised that they covered as little distance as their equipment tells them, but because RE is so ingrained, they just don't question it.
Can you not tell you're going faster when you're walking on a travelator? You know how much faster you'd need to be going to go round the flat Antarctica? It's not just a small difference.

I'm sure someone will come back to this and say there's some kind of extremely fast current that's dragging the boats round x times faster or something, well you'd only have to either stop or go the other way to find out if that's true.
Tom is wrong most of the time. Hardly big news, don't you think?

*

Offline JSS

  • *
  • Posts: 697
  • Math is math!
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #4 on: May 14, 2020, 08:18:05 PM »
I disagree that it would be so easy for the sailors to notice that they're traveling a greater distance than expected; there are so many x-factors involved with sailing. I suspect they rely primarily on navigation equipment to determine what kind of distances they've covered and just trust what they're told just like everyone else; for all we know innumerable sailors involved in this race were surprised that they covered as little distance as their equipment tells them, but because RE is so ingrained, they just don't question it.

I think if the GPS system was lying to sailors, the discrepancy between GPS and sextants and other navigation aids would be very quickly unmasked. 

The earliest popular sailboat races I could find in a quick search was in 1968, ten years before GPS launches and so I have to imagine they would also have noticed when suddenly the distances changed.

There are just too many ways of measuring your position for any one to be messed with, especially in this day and age.

Even a drunk sailor would notice if a trip was many times longer than it should have been.

*

Offline stack

  • *
  • Posts: 1456
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #5 on: May 14, 2020, 09:05:23 PM »
...for all we know innumerable sailors involved in this race were surprised that they covered as little distance as their equipment tells them, but because RE is so ingrained, they just don't question it.

A "for all we know" statement is merely a made up supposition. Take the Volvo Around the World races. If you've watched any of the footage, those guys and gals know exactly how fast they are going, where they are, where they are vectoring to, when they will get there given the variables, and where their competition is 24/7. Mishaps do occur, mostly due to the crazy routes they sometimes take chasing wind and storms (They can get up to 35 MPH, which is insane) where shoals and reefs aren't charted very well due to the remoteness of their route choice. But they still know right where they are on the planet.
Not much is known about the celestial bodies and their distances.

*

Offline RonJ

  • *
  • Posts: 1129
  • ACTA NON VERBA
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #6 on: May 14, 2020, 10:23:44 PM »
I've been out sailing off shore on a sail boat too.  However I was a professional merchant marine officer for the last 20 years of my career.  In those 20 years at least 10 of them were spent living & working an ocean going ships transiting the oceans of the world.  If you make a trip say from Shanghai, China to Long Beach, CA countless times you know within a small margin of error what the variables are.  Distances are very well known.  When you leave port you start the ship's engine.  The ship has a propeller with a known pitch.  That means for every turn of the propeller the ship travels a known distance.  There's a counter on the propeller shaft and at noon every day the shaft count is recorded.  You can use those figures to easily calculate a distance.  Of course there's some margin for error but if you are making the same trip over & over again you know what to expect.  If the distances traveled in a day don't match the known speeds it will quickly become apparent that something is wrong.  You can get within a mile or two with a sextant and closer than that with GPS so any good merchant marine navigator will know when things aren't correct.  I can say, in the Zetetic fashion, that the earth is proven to be spherical and can't be flat from countless ocean trips of over 5000 miles.  You are wasting your time to think anything else. 
For FE no explanation is possible, for RE no explanation is necessary.

Re: Around-the-World Sailing Races?
« Reply #7 on: May 15, 2020, 01:15:13 AM »
I've been out sailing off shore on a sail boat too.  However I was a professional merchant marine officer for the last 20 years of my career.  In those 20 years at least 10 of them were spent living & working an ocean going ships transiting the oceans of the world.  If you make a trip say from Shanghai, China to Long Beach, CA countless times you know within a small margin of error what the variables are.  Distances are very well known.  When you leave port you start the ship's engine.  The ship has a propeller with a known pitch.  That means for every turn of the propeller the ship travels a known distance.  There's a counter on the propeller shaft and at noon every day the shaft count is recorded.  You can use those figures to easily calculate a distance.  Of course there's some margin for error but if you are making the same trip over & over again you know what to expect.  If the distances traveled in a day don't match the known speeds it will quickly become apparent that something is wrong.  You can get within a mile or two with a sextant and closer than that with GPS so any good merchant marine navigator will know when things aren't correct.  I can say, in the Zetetic fashion, that the earth is proven to be spherical and can't be flat from countless ocean trips of over 5000 miles.  You are wasting your time to think anything else.

Fascinating.   I do have a question about the shaft count.  Wouldn't that only measure speed in water (and air) that are completely still?  In other words, air can push the ship a little, and water currents can also push the ship a little, right?  Wouldn't this affect the measurement, or is it too insignificant?


*

Offline RonJ

  • *
  • Posts: 1129
  • ACTA NON VERBA
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #8 on: May 15, 2020, 02:45:09 AM »
You are correct.  We also had a separate gauge that accurately measured speed thru water, but everything is relative to that water.  There are some significant currents out there that can easily add 3 or 4 knots to our speed depending on our heading at the time.  The current off the Japanese coast is one example.  Heavy seas taken head on will also result in more turns per mile.  Seas taken astern will do the opposite.  You have to be familiar with the average turns per mile under calm sea conditions.  Sea conditions has a bigger effect than winds.  Every ship was different.  You had to be familiar with a particular ship, the route, and the effects of the winds & waves on that particular ship.  All that takes lots of trips to get used to what is normal.  The whole idea of the shaft count in the first place was to get an idea of whether the hull was starting to get fouled.  A freshly painted hull would go further with every turn than a heavily fouled one.  Having said all that the GPS is the best indicator as it gives everything relative to the earth itself.  Our GPS data stream drove the electronic map display and you could always see the ship's position relative to land.  You could also overlay that GPS data to the radars to display the relative positions of the ship to nearby land and all the other ships either by radar return echoes or the AIS.  All the deck officers have to be trained on using a sextant for navigation as well.  We were required by law to carry one on board at all times in case of an emergency.  We sometimes carried Merchant Marine Academy cadets on board for training purposes and they often were taking sextant sights to get up to speed using the sextant although these days it would seldom be needed.  In the middle of the Pacific Ocean I could get out my iPhone and use the GPS app and obtain a GPS position that matched exactly to the main GPS receivers on the ship's console.  Using all the fancy navigational equipment would allow us to accurately predict when we would arrive at the sea buoy of our destination port.  This meant that we accurately knew distances & speeds.  Nothing we used would properly work if the earth were flat.
For FE no explanation is possible, for RE no explanation is necessary.

Re: Around-the-World Sailing Races? - Part 2
« Reply #9 on: May 15, 2020, 06:39:44 PM »
AS an experienced sailor, and knowing my beloved sailboat, Serenity, very well, I can tell without looking at the knotmeter a one knot difference in speed through the water.  And as others who have replied to my original post, looking at the common FE models would require distances that are at least 2 times farther than on a RE, and likely closer to three times farther to circumnavigate.  Please believe me that even ignoring GPS data, anyone with enough sailing experience to be doing a round-the-world race would be aware of the massively increased distance involved.  And monohull sailboats have a "hull speed" past which they cannot reasonably go faster.  This is based on the well-known physics of water itself and wave generation.  The oversimplified explanation is that as you push a displacement boat hull faster and faster it starts sinking deeper into the water, which greatly increases the drag until you reach a limit = the hull speed.  You just cannot make up that degree of distance increase.

My second question/puzzle for FE's is that I have the honor of being old enough to have been trained as a celestial navigator - using a sextant and an accurate watch to determine position at sea.  I was lucky enough that when I was in graduate school at Washington University in St. Louis I was able to take a whole semester long course in Celestial taught by a retired Navy officer navigator.  Since it was a semester long course we got heavily into the basic math involved.  In practice there are books of tables and now calculators/computers that do the math for you, but if you want as a FE believer to assume those books and computers are somehow "doctored" by NASA, my instructor made us do the math ourselves.  My final project was to write a computer program that calculated the "great circle route" between two points on the globe.  When Lindbergh wanted to calculate the great circle course (the shortest distance) for his historic flight from New York to Paris he had to stretch a string taut on a large globe at the New York City library before the flight and take careful notes as to where he should be at each stage of his flight. 

The math required for Celestial is called "spherical trigonometry", and you need a higher level scientific calculator or computer.  The simplest example I can give is that on a flat plane an equilateral triangle (all three sides are on the same exact length) has three angles of 60 degrees each.  However on a sphere an equilateral triangle is quite different, with three angles of 90 degrees each, not 60.  Imagine traveling on a sphere.  You start at the north pole and travel due south to the equator.  Once you reach the equator you turn due east or west (doesn't matter which), that's a 90 degree turn, and then travel the exact same distance as you did from the pole to the equator.  At that point you turn north again (another 90 degree turn) and travel back to the pole.  Once back at the pole again you will discover the angle between your departing and returning path is also 90 degrees.  Spherical trig has no trouble with calculating all sorts of triangles on the surface of a sphere.  Regular flat trig that we all learned in school won't work.  Likewise if we really are on a flat earth, then the math behind sextants wouldn't work, not even close.  But it works fine.  Not as good, and certainly not as easy as GPS, but gets you within about a mile of where you want to be, and for most purposes that's good enough.  And it's been used since the invention of a reliable chronometer (accurate clock at sea) in the 1760s.  Long before space flight, NASA or any other alleged conspirators.  Or do you think all those tens of thousands of crusty old sea captains were all part of a massive conspiracy to hide the flat earth secret for 260 years?  And not one of them ever fessed up about the "secret" he/she was keeping?

A FE answer please?

Re: Around-the-World Sailing Races? - Part 2
« Reply #10 on: May 15, 2020, 08:09:58 PM »
AS an experienced sailor, and knowing my beloved sailboat, Serenity, very well, I can tell without looking at the knotmeter a one knot difference in speed through the water.  And as others who have replied to my original post, looking at the common FE models would require distances that are at least 2 times farther than on a RE, and likely closer to three times farther to circumnavigate.  Please believe me that even ignoring GPS data, anyone with enough sailing experience to be doing a round-the-world race would be aware of the massively increased distance involved.  And monohull sailboats have a "hull speed" past which they cannot reasonably go faster.  This is based on the well-known physics of water itself and wave generation.  The oversimplified explanation is that as you push a displacement boat hull faster and faster it starts sinking deeper into the water, which greatly increases the drag until you reach a limit = the hull speed.  You just cannot make up that degree of distance increase.


I've never heard of hull speed, but it is interesting.  So basically, if you go TOO fast for a particular vessel (whatever its hull speed is), it will take on water and just sink?


*

Offline RonJ

  • *
  • Posts: 1129
  • ACTA NON VERBA
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #11 on: May 15, 2020, 11:55:03 PM »
Ships also have a hull speed.  Strangely enough the longer the ship is, the higher the hull speed will likely be.  I've been on some 1000 foot ships that could go 35 knots, but the fuel consumption was also very high.  Basically the hull speed is a function of the hull design and when you start exceeding the hull speed the horsepower (and fuel consumption) starts to increase exponentially.  Fast ships have a very long & narrow bow, but when you do that you can carry less cargo but at a faster speed.  Docks also charge a fee based upon the length of the vessel.  So shorter & wider vessels can carry more cargo with less expensive berthing fees, but you won't get to your next port quite as fast. We would always follow a great circle route that was a nice curve on a flat map, or in our case the electronic map.  Sometimes the nice shortest route was followed exactly but if there was a typhoon right in the middle of that path there might be some diversions.  Is there any doubt about why?  On our trip from Shanghi, China back to California when we reached the most Northern part of the great circle route, usually just South of the Aleutian Islands, we would have a 'top of the world' party for our crew of about 23.  If you have 100's of millions of dollars worth of cargo aboard there's little doubt about taking the shortest, fastest route, and that's always the great circle one on the globe earth.  If there was another faster route you can be sure that over the last 100 plus years some sailor would have figured it out and would have taken great advantage of that knowledge.  If you don't believe that just look up the works of Nathaniel Bowditch.  Every American flagged ship still has to carry 'the bowditch' aboard, by law.       
« Last Edit: May 15, 2020, 11:58:36 PM by RonJ »
For FE no explanation is possible, for RE no explanation is necessary.

Re: Around-the-World Sailing Races?
« Reply #12 on: May 16, 2020, 12:05:22 AM »
The slightly longer but still simplified explanation of hull speed is that the curved bottom of a sailboat can be viewed as an upside down airplane wing. On airplanes the curve points up, on sailboats down. As the boat moves through the water it creates “lift” downwards. The faster it goes the greater the down force, the deeper the boat sinks, and up goes the drag. There’s wave making issues too which limit the speed. And we’re only talking about the boat sinking down by a few inches but that’s enough to increase the drag to limit the speed. The standard formula is that the hull speed of most sailboats in knots is 1.34 times the square root of the waterline length.  My 34 foot (Overall) non-racing sailboat has a waterline length of about 25 feet, so her hull speed is 1.34 x sq rt(25) = 6.7 knots. Under perfect conditions I can get her up to about 7 knots but that’s it. (1 knot = 1.15 mph). High end racing yacht designers can use tricks to increase the hull speed past that formula - but not by much. Powerboats generally avoid the problem by skimming (planing) on the surface of the water, like continuously skipping a flat stone. And if the hull is really long and skinny (a ratio of length to beam generally greater than 20:1) other physics kicks in. Note: a real naval architect would be howling about my oversimplification. It ain’t simple.

Re: Around-the-World Sailing Races?
« Reply #13 on: May 16, 2020, 12:23:59 AM »
One other brief comment about sailboats and hull speed. Sailors are warned that if they ever need to be towed by a powerful powerboat - to make absolutely sure the skipper of the powerboat understands the hull speed of the towed boat. Trying to exceed that speed puts tremendous loads on the tow rope and whatever it is attached to, and yes, there have been occasional reports of sailboats being swamped and lost because someone tried to greatly exceed the boat’s hull speed during a tow. They weren’t paying attention as their tow sunk behind them.

Offline somerled

  • *
  • Posts: 319
    • View Profile
Re: Around-the-World Sailing Races? - Part 2
« Reply #14 on: May 17, 2020, 05:59:25 PM »
AS an experienced sailor, and knowing my beloved sailboat, Serenity, very well, I can tell without looking at the knotmeter a one knot difference in speed through the water.  And as others who have replied to my original post, looking at the common FE models would require distances that are at least 2 times farther than on a RE, and likely closer to three times farther to circumnavigate.  Please believe me that even ignoring GPS data, anyone with enough sailing experience to be doing a round-the-world race would be aware of the massively increased distance involved.  And monohull sailboats have a "hull speed" past which they cannot reasonably go faster.  This is based on the well-known physics of water itself and wave generation.  The oversimplified explanation is that as you push a displacement boat hull faster and faster it starts sinking deeper into the water, which greatly increases the drag until you reach a limit = the hull speed.  You just cannot make up that degree of distance increase.

My second question/puzzle for FE's is that I have the honor of being old enough to have been trained as a celestial navigator - using a sextant and an accurate watch to determine position at sea.  I was lucky enough that when I was in graduate school at Washington University in St. Louis I was able to take a whole semester long course in Celestial taught by a retired Navy officer navigator.  Since it was a semester long course we got heavily into the basic math involved.  In practice there are books of tables and now calculators/computers that do the math for you, but if you want as a FE believer to assume those books and computers are somehow "doctored" by NASA, my instructor made us do the math ourselves.  My final project was to write a computer program that calculated the "great circle route" between two points on the globe.  When Lindbergh wanted to calculate the great circle course (the shortest distance) for his historic flight from New York to Paris he had to stretch a string taut on a large globe at the New York City library before the flight and take careful notes as to where he should be at each stage of his flight. 

The math required for Celestial is called "spherical trigonometry", and you need a higher level scientific calculator or computer.  The simplest example I can give is that on a flat plane an equilateral triangle (all three sides are on the same exact length) has three angles of 60 degrees each.  However on a sphere an equilateral triangle is quite different, with three angles of 90 degrees each, not 60.  Imagine traveling on a sphere.  You start at the north pole and travel due south to the equator.  Once you reach the equator you turn due east or west (doesn't matter which), that's a 90 degree turn, and then travel the exact same distance as you did from the pole to the equator.  At that point you turn north again (another 90 degree turn) and travel back to the pole.  Once back at the pole again you will discover the angle between your departing and returning path is also 90 degrees.  Spherical trig has no trouble with calculating all sorts of triangles on the surface of a sphere.  Regular flat trig that we all learned in school won't work.  Likewise if we really are on a flat earth, then the math behind sextants wouldn't work, not even close.  But it works fine.  Not as good, and certainly not as easy as GPS, but gets you within about a mile of where you want to be, and for most purposes that's good enough.  And it's been used since the invention of a reliable chronometer (accurate clock at sea) in the 1760s.  Long before space flight, NASA or any other alleged conspirators.  Or do you think all those tens of thousands of crusty old sea captains were all part of a massive conspiracy to hide the flat earth secret for 260 years?  And not one of them ever fessed up about the "secret" he/she was keeping?

A FE answer please?
Regarding your second question , am assuming use of a compass, on FE head due south from the N pole - reach the equator , turn 90 east travel along the equator , which is a circle ,  following your compass heading of due east for same distance ,turn 90 N travelling same distance again using compass . Wouldn't you end back up at the N pole or am I missing something ?

Re: Around-the-World Sailing Races?
« Reply #15 on: May 17, 2020, 10:44:28 PM »
Yes, indeed you would end up back at the pole on a FE with your proposed trip, BUT the flaw in that is that you have not made an equilateral triangle on your flat earth since the equator part of the trip is a curved line, a radius around the North Pole.  The math would then fail.  On a globe my route from pole to equator and back to the pole is a perfectly fine 90-90-90 equilateral spherical triangle.  Yours is a pie wedge. 

And so far, no one has answered why celestial navigation, based on spherical trigonometry, works if the earth is truly flat.  Plus the matching issue as to why sea captains don’t believe in a flat earth. 

Offline somerled

  • *
  • Posts: 319
    • View Profile
Re: Around-the-World Sailing Races?
« Reply #16 on: May 18, 2020, 01:27:47 PM »
Yes, indeed you would end up back at the pole on a FE with your proposed trip, BUT the flaw in that is that you have not made an equilateral triangle on your flat earth since the equator part of the trip is a curved line, a radius around the North Pole.  The math would then fail.  On a globe my route from pole to equator and back to the pole is a perfectly fine 90-90-90 equilateral spherical triangle.  Yours is a pie wedge. 

And so far, no one has answered why celestial navigation, based on spherical trigonometry, works if the earth is truly flat.  Plus the matching issue as to why sea captains don’t believe in a flat earth.

They are the same journey with the same result . The math doesn't fail . In FE the angle between outward and return leg at the pole is 90 degrees . The angle at the equator is 90 E and when you reach the required distance you turn 90N . The difference is that you believe you are journeying over a curved surface and so are applying spherical trig.

This also answers your celestial navigation - latitudes are circular lines around the point on earth beneath the N pole.

totallackey

Re: Around-the-World Sailing Races?
« Reply #17 on: May 18, 2020, 01:43:39 PM »
Yes, indeed you would end up back at the pole on a FE with your proposed trip, BUT the flaw in that is that you have not made an equilateral triangle on your flat earth since the equator part of the trip is a curved line, a radius around the North Pole.  The math would then fail.  On a globe my route from pole to equator and back to the pole is a perfectly fine 90-90-90 equilateral spherical triangle.  Yours is a pie wedge. 

And so far, no one has answered why celestial navigation, based on spherical trigonometry, works if the earth is truly flat.  Plus the matching issue as to why sea captains don’t believe in a flat earth.
Everything above our heads appears as if it is in a cylinder.

That is how objects would appear above an x/y coordinate system.

You don't need spherical trigonometry to negotiate an ocean trip.

That's just nonsense.

Re: Around-the-World Sailing Races?
« Reply #18 on: May 18, 2020, 03:43:19 PM »
Okay, I gave the illustration of an equilateral triangle on a sphere with three 90 degree angles to contrast to the standard flat equilateral triangle of three 60 degree angles just to illustrate the difference and to make sure readers knew what I was talking about.  Never-the-less spherical trig is indeed different than flat trig, and celestial navigation is based on spherical trig.  It uses spherical trig to calculate the angles relative to where a celestial body is directly over the surface of the earth at the time you are taking the sight.  (In other words the place you would be if the celestial body you are using was straight up over your head.) If that were the case all the time then celestial would be absurdly easy. Since the celestial object (sun, moon stars, planets) is almost never directly over your head, you use a sextant to measure the angle that object appears above the horizon.  Celestial then uses that angle with spherical trig to determine your "line of position".  (It's a movie myth that a single sextant sight gives you an "X marks the spot" position.  Except for the famous "noon sight" you get a short line that you are somewhere on that line.  There are other ways to then upscale that to a more precise position.).  And in reality nobody does the math themselves.  You use either books of detailed tables or later computer/calculators to do that math.  BUT the reality is that the system is indeed based on spherical trig, not flat trig.  The respondent's statement that you don't need spherical trig to navigate, that it's "nonsense" is simply not true for celestial navigation.  it is true for navigating on a chart, within sight of land, to work out your bearing to a lighthouse for example.  Flat trig works fine for that, because the distances involved are so short that the "needed correction" for being on the surface of a sphere is trivial.  It's the same reason you can use a flat paper chart to navigate along the coast.  Technically that flat chart is slightly "wrong" since you cannot accurately depict a sphere on a flat paper, but again for the distances involved the "error" is trivial.  But out on the open ocean, trying to determine your position is an entirely different matter.  Prior to GPS, you needed celestial navigation to do that. And without the spherical trig behind celestial, it would fail. And it doesn't fail - it works.  It's worked for hundreds of years.  If the earth was flat, then the math for celestial would be standard flat trig, but it's not.  There would be no need to calculate spherical triangles to determine your position since you are on a alleged flat surface.  This is a simple non-disputable fact.

I feel I speak with some degree of real-world expertise about celestial navigation.  Anybody out there who has used celestial who disagrees with me?

totallackey

Re: Around-the-World Sailing Races?
« Reply #19 on: May 18, 2020, 04:02:05 PM »
Okay, I gave the illustration of an equilateral triangle on a sphere with three 90 degree angles to contrast to the standard flat equilateral triangle of three 60 degree angles just to illustrate the difference and to make sure readers knew what I was talking about.  Never-the-less spherical trig is indeed different than flat trig, and celestial navigation is based on spherical trig. It uses spherical trig to calculate the angles relative to where a celestial body is directly over the surface of the earth at the time you are taking the sight.  (In other words the place you would be if the celestial body you are using was straight up over your head.) If that were the case all the time then celestial would be absurdly easy. Since the celestial object (sun, moon stars, planets) is almost never directly over your head, you use a sextant to measure the angle that object appears above the horizon.  Celestial then uses that angle with spherical trig to determine your "line of position".  (It's a movie myth that a single sextant sight gives you an "X marks the spot" position.  Except for the famous "noon sight" you get a short line that you are somewhere on that line.  There are other ways to then upscale that to a more precise position.).  And in reality nobody does the math themselves.  You use either books of detailed tables or later computer/calculators to do that math.  BUT the reality is that the system is indeed based on spherical trig, not flat trig.  The respondent's statement that you don't need spherical trig to navigate, that it's "nonsense" is simply not true for celestial navigation.  it is true for navigating on a chart, within sight of land, to work out your bearing to a lighthouse for example.  Flat trig works fine for that, because the distances involved are so short that the "needed correction" for being on the surface of a sphere is trivial.  It's the same reason you can use a flat paper chart to navigate along the coast.  Technically that flat chart is slightly "wrong" since you cannot accurately depict a sphere on a flat paper, but again for the distances involved the "error" is trivial.  But out on the open ocean, trying to determine your position is an entirely different matter.  Prior to GPS, you needed celestial navigation to do that. And without the spherical trig behind celestial, it would fail. And it doesn't fail - it works.  It's worked for hundreds of years.  If the earth was flat, then the math for celestial would be standard flat trig, but it's not.  There would be no need to calculate spherical triangles to determine your position since you are on a alleged flat surface.  This is a simple non-disputable fact.

I feel I speak with some degree of real-world expertise about celestial navigation.  Anybody out there who has used celestial who disagrees with me?
Since all things above our heads on an x/y plane would appear as if they were moving in a cylindrical motion, that accounts for your supposed spherical trig...but like I wrote earlier, it isn't even necessary.

Just a bunch of hogwash.
« Last Edit: May 18, 2020, 04:11:31 PM by totallackey »