Terry Pratchett’s Discworld novels captured my imagination from an early age, and one of the reasons for that was the idea of a flat world flying through space on the back of four elephants, on the back of a giant turtle, a concept that just seemed so odd and exciting.  But what inspired Pratchett to set his stories on a flat earth?  His first use of the idea can be found in Strata, a pre-Discworld book, which draws heavily on ideas from Ringworld by Larry Niven.  Another likely source of inspiration can be found Steven Hawking’s opening to A Brief History of Time:

“A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy.  He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy.  At the end of the lecture, a little old lady at the back of the room got up and said: ‘What you have told us is rubbish.  The world is really a flat plate supported on the back of a giant tortoise.’  The scientist gave a superior smile before replying, ‘What is the tortoise standing on?’ ‘You’re very clever, young man, very clever,’ said the old lady.  ‘But it’s turtles all the way down!’

Hawking’s introduction could not have been the source of inspiration, because it was published five years after The Colour of Magic, but it is likely that Pratchett was aware of the anecdote.

There is an historical misconception that belief in a flat Earth was commonplace in the middle ages.  In fact, just about every reasonably educated person has been aware of the spherical nature of the planet since the ancient Greeks figured it out.  However, facts aren’t often allowed to get in the way of silly but exciting ideas for the minority who search for some hidden truth and grasp at the wrong straws.

In 1885, William Carpenter published the entertainingly titled One Hundred Proofs that the Earth is not a Globe.  Amusingly, most of his ‘proofs’ can be explained away by Carpenter ignoring two simple facts: (1) the Earth is actually quite big, and (2) gravity.  The following selected quotes, along with some of my own discussion, were first published on our sister site Windows into History.

1. The aeronaut can see for himself that Earth is a Plane. The appearance presented to him, even at the highest elevation he has ever attained, is that of a concave surface — this being exactly what is to be expected of a surface that is truly level, since it is the nature of level surfaces to appear to rise to a level with the eye of the observer. This is ocular demonstration and proof that Earth is not a globe.

Carpenter’s misunderstanding, as I mentioned above, is that he never quite grasped that the Earth is actually rather big. A decade before Carpenter’s book, a balloon reached the height of 28,000 feet (8600 metres). Two of the three occupants died. Even that great altitude was probably not high enough to see the curvature of the Earth. Even pilots flying at 40,000 feet often report not being able to see any curvature.

2. Whenever experiments have been tried on the surface of standing water, this surface has always been found to be level. If the Earth were a globe, the surface of all standing water would be convex. This is an experimental proof that Earth is not a globe.

3. Surveyors’ operations in the construction of railroads, tunnels, or canals are conducted without the slightest “allowance” being made for “curvature,” although it is taught that this so-called allowance is absolutely necessary! This is a cutting proof that Earth is not a globe.

8. If the Earth were a globe, a small model globe would be the very best — because the truest — thing for the navigator to take to sea with him. But such a thing as that is not known: with such a toy as a guide, the mariner would wreck his ship, of a certainty! This is a proof that Earth is not a globe.

A navigational globe of sorts did exist, the celestial globe, although it was the stars that were mapped on the globe not the Earth.

9. As mariners take to sea with them charts constructed as though the sea were a level surface, however these charts may err as to the true form of this level surface taken as a whole, it is clear, as they find them answer their purpose tolerably well — and only tolerably well, for many ships are wrecked owing to the error of which we speak — that the surface of the sea is as it is taken to be, whether the captain of the ship “supposes” the Earth to be a globe or anything else. Thus, then, we draw, from the common system of “plane sailing” a practical proof that Earth is not a globe.

12. As we have seen that there is, really, no south point (or pole) but an infinity of points forming, together, a vast circumference — the boundary of the known world, with its battlements of icebergs which bid defiance to man’s onward course in a southerly direction — so there can be no east or west “points,” just as there is no “yesterday,” and no “to-morrow.” In fact, as there is one point that is fixed (the North), it is impossible for any other point to be fixed likewise. East and west are, therefore, merely directions at right angles with a north and south line: and as the south point of the compass shifts round to all parts of the circular boundary, (as it maybe carried round the central North), so the directions east and west, crossing this line, continued, form a circle, at any latitude. A westerly circumnavigation, therefore, is a going round with the North Star continually on the right hand, and an easterly circumnavigation is performed only when the reverse condition of things is maintained, the North Star being on the left hand as the journey is made. These facts, taken together, form a beautiful proof that the Earth is not a globe.

15. The idea that, instead of sailing horizontally round the Earth, ships are taken down one side of a globe, then underneath, and are brought up on the other side to get home again, is, except as a mere dream, impossible and absurd! And, since there are neither impossibilities nor absurdities in the simple matter of circumnavigation, it stands, without argument, a proof that the Earth is not a globe.

17. Human beings require a surface on which to live that, in its general character, shall be level; and since the Omniscient Creator must have been perfectly acquainted with the requirements of His creatures, it follows that, being an All-wise Creator, He has met them thoroughly. This is a theological proof that the Earth is not a globe.

18. The best possessions of man are his senses; and, when he uses them all, he will not be deceived in his survey of nature. It is only when some one faculty or other is neglected or abused that he is deluded. Every man in full command of his senses knows that a level surface is a flat or horizontal one; but astronomers tell us that the true level is the curved surface of a globe! They know that man requires a level surface on which to live, so they give him one in name which is not one in fact! Since this is the best that astronomers, with their theoretical science, can do for their fellow creatures — deceive them — it is clear that things are not as they say they are; and, in short, it is a proof that Earth is not a globe.

20. The common sense of man tells him — if nothing else told him — that there is an “up” and a “down” in nature, even as regards the heavens and the earth; but the theory of modern astronomers necessitates the conclusion that there is not: therefore, the theory of the astronomers is opposed to common sense — yes, and to inspiration — and this is a common sense proof that the Earth is not a globe.

21. Man’s experience tells him that he is not constructed like the flies that can live and move upon the ceiling of a room with as much safety as on the floor: and since the modern theory of a planetary earth necessitates a crowd of theories to keep company with it, and one of them is that men are really bound to the earth by a force which fastens them to it  “like needles round a spherical loadstone,” a theory perfectly outrageous and opposed to all human experience, it follows that, unless we can trample upon common sense and ignore the teachings of experience, we have an evident proof that the Earth is not a globe.

23. If astronomical works be searched through and through, there will not be found a single instance of a bold, unhesitating, or manly statement respecting a proof of the Earth’s “rotundity.”

25. The surveyor’s plans in relation to the laying of the first Atlantic Telegraph cable, show that in 1665 miles — from Valentia, Ireland, to St. John’s, Newfoundland — the surface of the Atlantic Ocean is a level surface — not the astronomers’ “level,” either! The authoritative drawings, published at the time, are a standing evidence of the fact, and form a practical proof that Earth is not a globe.

The Transatlantic telegraph cable was completed in 1858, and functioned for a not-so-grand total of three weeks.  I am not quite sure how the Earth’s curvature would make any difference to laying a cable, or how one draughtsman’s failure to make any mention of it would prove the Earth is flat…

28. Astronomers are in the habit of considering two points on the Earth’s surface, without, it seems, any limit as to the distance that lies between them, as being on a level, and the intervening section, even though it be an ocean, as a vast “hill” — of water! The Atlantic ocean, in taking this view of the matter, would form a “hill of water” more than a hundred miles high! The idea is simply monstrous, and could only be entertained by scientists whose whole business is made up of materials of the same description: and it certainly requires no argument to deduce, from such ”science” as this, a satisfactory proof that the Earth is not a globe.

29. If the Earth were a globe, it would, unquestionably, have the same general characteristics — no matter its size — as a small globe that may be stood upon the table. As the small globe has top, bottom, and sides, so must also the large one — no matter how large it be. But, as the Earth, which is “supposed” to be a large globe, has no sides or bottom as the small globe has, the conclusion is irresistible that it is a proof that Earth is not a globe.

33. If the Earth were a globe, people — except those on the top — would, certainly, have to be ” fastened” to its surface by some means or other, whether by the “attraction” of astronomers or by some other undiscovered and undiscoverable process! But, as we know that we simply walk on its surface without any other aid than that which is necessary for locomotion on a plane, it follows that we have, herein, a conclusive proof that Earth is not a globe.

34. If the Earth were a globe, there certainly would be — if we could imagine the thing to be peopled all round — “antipodes:” “people who,” says the dictionary, “living exactly on the opposite side of the globe to ourselves, have their feet opposite to ours:” — people who are hanging heads downwards whilst we are standing heads up! But, since the theory allows us to travel to those parts of the Earth where the people are said to be heads downwards, and still to fancy ourselves to be heads upwards and our friends whom we have left behind us to be heads downwards, it follows that the whole thing is a myth — a dream — a delusion — and a snare; and, instead of there being any evidence at all in this direction to substantiate the popular theory, it is a plain proof that the Earth is not a globe.

35. If we examine a true picture of the distant horizon, or the thing itself, we shall find that it coincides exactly with a perfectly straight and level line. Now, since there could be nothing of the kind on a globe, and we find it to be the case all over the Earth, it is a proof that the Earth is not a globe.

This falls into the category of not understanding, or ignoring, that the Earth is very, very big, common to so many of the 100 ‘proofs’.  The horizon is not flat, but is such a gentle curve that it appears to be so to the naked eye.  Photographs showing large expanses of flat surface on the planet (e.g. lakes) can be mapped against a straight line and the horizon will curve very slightly above the line.

40. The Suez Canal, which joins the Red Sea with the Mediterranean, is about one hundred miles long; it forms a straight and level surface of water from one end to the other; and no “allowance” for any supposed “curvature” was made in its construction. It is a clear proof that the Earth is not a globe.

Allowance was not made because there is no need when building a canal.  However, in construction of very long bridges and tunnels it does have to be taken into account.

42. It is certain that the theory of the Earth’s rotundity and that of its mobility must stand or fall together. A proof, then, of its immobility is virtually a proof of its non-rotundity. Now, that the Earth does not move, either on an axis, or in an orbit round the Sun or anything else, is easily proven. If the Earth went through space at the rate of eleven-hundred miles in a minute of time, as astronomers teach us, in a particular direction, there would unquestionably be a difference in the result of firing off a projectile in that direction and in a direction the opposite of that one. But as, in fact, there is not the slightest difference in any such case, it is clear that any alleged motion of the Earth is disproved, and that, therefore, we have a proof that the Earth is not a globe.

45. The Astronomer Royal, of England, George B, Airy, in his celebrated work on Astronomy, the “Ipswich Lectures,” says: “Jupiter is a large planet that turns on his axis, and why do not we turn?” Of course, the common sense reply is: Because the Earth is not a planet! When, therefore, an astronomer royal puts words into our mouth wherewith we may overthrow the supposed planetary nature of the Earth, we have not far to go to pick up a proof that Earth is not a globe.

Carpenter should have been aware of the relatively recent empirical test for the rotation of the Earth, Leon Foucault’s pendulum at the top of the Paris Pantheon, in 1851, which showed a shift in the pendulum’s plane of oscillation in accordance with the latitude of Paris.

49. It is a well-known fact that clouds are continually seen moving in all manner of directions — yes, and frequently, in different directions at the same time — from west to east being as frequent a direction as any other. Now, if the Earth were a globe, revolving through space from west to east at the rate of nineteen miles in a second, the clouds appearing to us to move towards the east would have to move quicker than nineteen miles in a second to be thus seen; whilst those which appear to be moving in the opposite direction would have no necessity to be moving at all, since the motion of the Earth would be more than sufficient to cause the appearance. But it only takes a little common sense to show us that it is the clouds that move just as they appear to do, and that, therefore, the Earth is motionless. We have, then, a proof that the Earth is not a globe.

54. The aeronaut is able to start in his balloon and remain for hours in the air, at an elevation of several miles, and come down again in the same county or parish from which he ascended. Now, unless the Earth drag the balloon along with it in its nineteen-miles-a-second motion, it must be left far behind, in space: but, since balloons have never been known thus to be left, it is a proof that the Earth, does not move, and, therefore, a proof that the Earth is not a globe.

If this did not happen we would be living in a very odd kind of world where the atmosphere stayed perfectly still while the earth moved around below it.  Gravity.

55. The Newtonian theory of astronomy requires that the Moon “borrow” her light from the Sun. Now, since the Sun’s rays are hot and the Moon’s light sends with it no heat at all, it follows that the Sun and Moon are “two great lights,” as we somewhere read; that the Newtonian theory is a mistake; and that, therefore, we have a proof that the Earth is not a globe.

62. It is commonly asserted that “the Earth must be a globe because people have sailed round it.” Now, since this implies that we can sail round nothing unless it be a globe, and the fact is well known that we can sail round the Earth as a plane, the assertion is ridiculous, and we have another proof that Earth is not a globe.

63. It is a fact not so well known as it ought to be that when a ship, in sailing away from us, has reached the point at which her hull is lost to our unaided vision, a good telescope will restore to our view this portion of the vessel. Now, since telescopes are not made to enable people to see through a “hill of water,” it is clear that the hulls of ships are not behind a hill of water when they can be seen through a telescope though lost to our unaided vision. This is a proof that Earth is not a globe.

The horizon is about 3 miles away from you.  How much distance needs to be added to that before a ship would disappear (with a telescope or not) would depend on the height of the ship, but the positioning of a crow’s nest at the top of a mast is not for the fun of it.  The higher you are, the further around the curvature of the Earth you can see (about 9 miles from a crow’s nest).  If this ‘proof’ were correct, you could of course turn it on its head, and a powerful modern telescope could be used to see antipodean countries.

77. “Oh, but if the Earth is a plane, we could go to the edge and tumble over!” is a very common assertion. This is a conclusion that is formed too hastily, and facts overthrow it. The Earth certainly is, just what man by his observation finds it to be, and what Mr. Proctor himself says it ” seems” to be — flat ; and we cannot cross the icy barrier which surrounds it. This is a complete answer to the objection, and, of course, a proof that Earth is not a globe.

85. There are rivers which flow east, west, north, and south — that is, rivers are flowing in all directions over the Earth’s surface, and at the same time. Now, if the Earth were a globe, some of these rivers would be flowing up-hill and others down, taking it for a fact that there really is an “up” and a ”down” in nature, whatever form she assumes. But, since rivers do not flow up-hill, and the globular theory requires that they should, it is a proof that the Earth is not a globe.

The idea of a flat Earth might seem foolish, but it inspired my favourite ever series of fantasy fiction novels, so it’s one conspiracy theory I’m glad exists.   RP