15. “If the Earth were truly a sphere 25,000 miles in circumference, airplane pilots would have to constantly correct their altitudes downwards so as to not fly straight off into “outer space;” a pilot wishing to simply maintain their altitude at a typical cruising speed of 500 mph, would have to constantly dip their nose downwards and descend 2,777 feet (over half a mile) every minute! Otherwise, without compensation, in one hour’s time the pilot would find themselves 31.5 miles higher than expected.”

Ok, another one related to the error in points 7 and 12 – not understanding what flat or level means in relation to the gravity of a sphere.

“Level flight” is flight that keeps the plane at the same height relative to the mass of the earth. A plane won’t fly in a geometrically straight line, rising higher and higher in relation to the earth’s surface.

If it did, it would be rising higher in the atmosphere, and this would involve using energy (fuel) to rise higher, which means to overcome gravity. But a level flight line in relation to the earth is a circle, not a straight line. 

Frankly, an author who can put forward such an obviously fallacious argument all claim to credibility.

14. “The Lieutenant-Colonel Portlock experiment used oxy-hydrogen Drummond’s lights and heliostats to reflect the sun’s rays across stations set up across 108 miles of St. George’s Channel. If the Earth were actually a ball 25,000 miles in circumference, Portlock’s light should have remained hidden under a mile and a half of curvature.” 

The source is the same, the alleged “Doctor” Rowbotham of very dubious qualifications and medical understanding.  See Garwood, Christine (2010). Flat Earth: The History of an Infamous Idea Pan Macmillan.

And again, the numbers are wrong. 

It’s quite possible to see that mountain in Ireland from the Welsh Preselli Hills. The height needed is 1,437 feet, and the highest peak in Preseli is 1,759 feet. No problem.

http://the-uncredibles.tumblr.com/post/130629473404/200-pensb-14-lt-col-portlock

As Daimonie puts it,  “Another way of saying Dubay don't understand what the horizon is. See approximately all previous points” .

12. “ The Manchester Ship Canal Company published in the Earth Review stated, “It is customary in Railway and Canal constructions for all levels to be referred to a datum which is nominally horizontal and is so shown on all sections. It is not the practice in laying out Public Works to make allowances for the curvature of the earth”

Yes, it’s the same argument from Point 7 again!  

It was wrong then, so it’s wrong here to. 

And it is based on a quote that can’t be found anywhere but other flat earth publications. 

The quote says it’s not the practice to take account of the negligible difference of 8 inches over a mile, and that’s probably true, because it doesn’t matter when building a canal. When building an accelerator, it does matter, so engineers do take it into account. 

11 “A  surveyor and engineer of thirty years published in the Birmingham Weekly Mercury stated, “I am thoroughly acquainted with the theory and practice of civil engineering. However bigoted some of our professors may be in the theory of surveying according to the prescribed rules, yet it is well known amongst us that such theoretical measurements are INCAPABLE OF ANY PRACTICAL ILLUSTRATION. All our locomotives are designed to run on what may be regarded as TRUE LEVELS or FLATS. There are, of course, partial inclines or gradients here and there, but they are always accurately defined and must be carefully traversed. But anything approaching to eight inches in the mile, increasing as the square of the distance, COULD NOT BE WORKED BY ANY ENGINE THAT WAS EVER YET CONSTRUCTED. Taking one station with another all over England and Scotland, it may be stated that all the platforms are ON THE SAME RELATIVE LEVEL. The distance between Eastern and Western coasts of England may be set down as 300 miles. If the prescribed curvature was indeed as represented, the central stations at Rugby or Warwick ought to be close upon three miles higher than a chord drawn from the two extremities. If such was the case there is not a driver or stoker within the Kingdom that would be found to take charge of the train. We can only laugh at those of your readers who seriously give us credit for such venturesome exploits, as running trains round spherical curves. Horizontal curves on levels are dangerous enough, vertical curves would be a thousand times worse, and with our rolling stock constructed as at present physically impossible.””

This  is just a repetition of  the false claim in point 7, using a weirdly ill-informed historical quote from an evidently incompetent engineer. 

Incompetent, that is, if he thinks a locomotive couldn’t manage an incline of 8 inches in a mile.  He also makes a childish howler by assuming that he can multiply  up the difference between the east and west coats of Britain and add the product to one end. Why does that make the slightest sense?

But in any case, it’s the same foolish inability to understand that moving along,  around the curve of the globe is moving on the level, not climbing. Up and down on the surface of the earth means moving further from the centre of the earth, or closer to it, respectively.

Moreover, this alleged engineer repeats the bizarre mistake of point 10: he confuses a real “hump” in the ground, where the railway would rise up further from the earth’s centre and then fall back towards it, with following the curved surface of the earth while remaining at the same distance from the centre.

And to repeat, when it matters, engineers do take the curvature into account – see the referenced docs in point 7, about Japan’s Proton Accelerator Complex, and a number of other examples. 

There, as in other big scientific projects like CERN large Hadron Collider,  the lines really, really had to be straight, so the engineers did what this video pretends they “never” do -  they took the earth’s curvature into account. 

And guess what; it worked! If the earth had been flat, their calculations would have been wrong, and a hugely expensive installation would have been useless.

10)  The London and Northwestern Railway forms a straight line 180 miles long between London and Liverpool. The railroad’s highest point, midway at Birmingham station, is only 240 feet above sea-level. If the world were actually a globe, however, curving 8 inches per mile squared, the 180 mile stretch of rail would form an arc with the center point at Birmingham raising over a mile, a full 5,400 feet above London and Liverpool.”

 Are you serious, Mr Dubay? Do you really think that the curve of the earth between two cities means that the land midway between them is somehow "higher" than either city?

Do you not understand basic geometry?   Apart from any hills or valleys, both cities are about the same distance above mean sea level, or above the centre of the Earth’s globe. 

So is the mid point between them! 

At any one point “higher” or “lower” means further from the centre of the earth, or closer to it (ignoring tiny negligible variations owing to spin or tidal effects). This should be enough to show that this is absurdity. 

8.  “The Suez Canal connecting the Mediterranean with the Red Sea is 100 miles long without any locks making the water an uninterrupted continuation of the two seas. When constructed, the Earth’s supposed curvature was not taken into account, it was dug along a horizontal datum line 26 feet below sea-level, passing through several lakes from one sea to the other, with the datum line and water’s surface running perfectly parallel over the 100 miles.”

 So what? Of course this is exactly what we would expect from a (roughly) spherical Earth. For the whole length, the balance of gravitational and centrifugal forces are the same, so it is level to for all practical purposes.

“It's literally the instruction 'dig this deep'. Can you make an incision, 1 cm deep, in an apple?

You can? Well, therefore that apple is flat. Well done, that person.”

Thank you, Daimonie

For yet more information debunking Dubay read this, too.

 3) “The natural physics of water is to find and maintain its level. If Earth were a giant sphere tilted, wobbling and hurdling through infinite space then truly flat, consistently level surfaces would not exist here. But since Earth is in fact an extended flat plane, this fundamental physical property of fluids finding and remaining level is consistent with experience and common sense.”

Dubay claims that truly flat surfaces wouldn’t exist on a sphere. Not for the last time, Mr Dubay shows that he doesn’t understand why numbers and quantities matter when seeking the truth.

 Do the mathematics. Work out how large the curvature would be on a sea or large lake , given an Earth with a diameter of 7,900 miles.

Of course, we have been seeing the curvature for as long as we have been going to sea.

In the days of sail, sailors often noticed that they could see other ships further off if they climbed to the tops of their masts. This was an important factor in times of war or piracy.

One thing that Dubay doesn’t understand is that the difference between water being level, and its supposedly being flat. A level ocean, on the Earth’s surface, means that the surface is the same distance from the earth’s centre of gravity. It has run “downwards” (that is, inwards) as far as it can go!

And the Earth is not “wobbling and hurdling” – its slightly elliptical path around the sun is quite steady and not at all ‘wobbly’ – there is nothing to make it wobble, despite Dubay believes. Again, he simply doesn’t understand the ideas that he is criticising.

For those who understand geometry, the surface of the water is perpendicular to the centre of the earth at every point.

·         (Note: Not all water is actually flat. 

• Very small drops are slightly curved because of surface tension. On a small scale, surface tension is stronger than gravity. So we get this shape 
• The wind causes waves which roughen the surface very slightly.
•   Oceans aren’t completely level because of tides.