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Bedford Level experiment

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The Bedford Level Experiment is a series of observations carried out along a six-mile (9.7 km) length of the Old Bedford River on the Bedford Level, Norfolk, England, during the nineteenth and early twentieth centuries. It was an attempt to determine the shape of the Earth. The results seemed to indicate that the Earth was flat.

Contents

 [hide] 

• 1 Method
• 2 Earth's curvature
• 3 History
• 4 Refraction
• 5 Other experiments
• 6 See also
• 7 Notes
• 8 References

Method[edit]

At the point chosen for all the experiments the river is a slow-flowing drainage canal running in an uninterrupted straight line for a six-mile (9.7 km) stretch to the north-east of the village of Welney. The most famous of the observations, and the one that was taught in schools until photographs of the Earth from space became available,^[1][2] involved a set of three poles fixed at equal height above water level along this length. As the surface of the water was assumed to be level, the discovery that the middle pole, when viewed carefully through a theodolite, was almost three feet (0.91 m) higher than the poles at each end was finally accepted as a new proof that the surface of the earth was indeed curved.^[3]

Earth's curvature[edit]

Below is the method that Samuel Birley Rowbotham used for calculating the rate at which the spherical earth curves.

"If the earth is a globe, and is 25,000 English statute miles in circumference, the surface of all standing water must have a certain degree of convexity--every part must be an arc of a circle. From the summit of any such arc there will exist a curvature or declination of 8 inches in the first statute mile. In the second mile the fall will be 32 inches; in the third mile, 72 inches, or 6 feet, as shown in the following diagram:

Earth's rate of curvature

"Let the distance from T to figure 1 represent 1 mile, and the fall from 1 to A, 8 inches; then the fall from 2 to B will be 32 inches, and from 3 to C, 72 inches. In every mile after the first, the curvature downwards from the point T increases as the square of the distance multiplied by 8 inches. The rule, however, requires to be modified after the first thousand miles.

"The following table will show at a glance the amount of curvature, in round numbers, in different distances up to 100 miles. To find the curvature in any number of miles not given in the table, simply square the number, multiply that by 8, and divide by 12. The quotient is the curvation required.

Statute Miles Away	Math	= Drop
1	1 x 1 x 8 =	8 Inches
2	2 x 2 x 8 =	32 Inches
3	3 x 3 x 8 / 12 =	6 Feet
4	4 x 4 x 8 / 12 =	10 Feet
5	5 x 5 x 8 / 12 =	16 Feet
6	6 x 6 x 8 / 12 =	24 Feet
7	7 x 7 x 8 / 12 =	32 Feet
8	8 x 8 x 8 / 12 =	42 Feet
9	9 x 9 x 8 / 12 =	54 Feet
10	10 x 10 x 8 / 12 =	66 Feet

"To find the curvature in any number of miles not given in the table, simply square the number, multiply that by 8, and divide by 12. The quotient is the curvation required."^[4]

Rowbotham's use of the formula

The diagram on the right shows the rhetorical use he often made of these numbers to demonstrate in this case that Great Orme Head would be 872' below the horizon as seen from the Isle of Man. Note that the sloping lines are drawn from sea level not from the hills or the observer.^[5]

History[edit]

Diagram of Rowbotham's experiment on the Bedford Level, taken from his book "Earth not a globe"

The first investigation was carried out by Samuel Birley Rowbotham (1816–1884), in the summer of 1838. He waded into the river and used a telescope held eight inches (20 cm) above the water to watch a boat with a five-foot (1.5 m) mast row slowly away from him.^[a] He reported that the vessel remained constantly in his view for the full six miles (9.7 km) to Welney bridge, whereas, had the water surface been curved with the accepted circumference of a spherical earth, the top of the mast should have been some 11 feet (3.4 m) below his line of sight. He published this discovery under the title Zetetic Astronomy using the pseudonym Parallax in 1849 and subsequently expanded it into a book published in 1865.^[7]

The view through Wallace's level as reproduced in his autobiography

Rowbotham repeated his experiments several times over the years but his claims received little attention until, in 1870, a supporter by the name of John Hampden offered a wager that he could show, by repeating Rowbotham's experiment, that the earth was flat. The noted naturalist and qualified surveyor Alfred Russel Wallace accepted the wager. Wallace, by virtue of his surveyor's training and knowledge of physics, avoided the errors of the preceding experiments and won the bet.^[8][9] The crucial step was to set a sight line 13 feet (4 m) above the water, and thereby avoid the effects of atmospheric refraction.^[10] Despite Hampden initially refusing to accept the demonstration, Wallace was awarded the bet by the referee, editor of The Field sports magazine. Hampden subsequently published a pamphlet alleging that Wallace had cheated and sued for his money. Several protracted court cases ensued, with the result that Hampden was imprisoned for threatening to kill Wallace^[11] and for libel.^[12][13] The same court ruled that the wager had been invalid because Hampden retracted the bet and required that Wallace return the money to Hampden. Wallace, who had been unaware of Rowbotham's earlier experiments, was criticized by his peers for "his 'injudicious' involvement in a bet to 'decide' the most fundamental and established of scientific facts".^[10]

View through the sight published by "Parallax" (1870)

In 1901, Henry Yule Oldham, a geography reader at King's College, Cambridge, claimed to have conducted the definitive experiment described in "Method", above.^[3][14]

Picture of the Bedford Level "carried out in misty and very unsatisfactory weather on May 11th 1904 before Lady Blount and several scientific gentlemen".

The planists, however, were not yet defeated: On 11 May 1904 Lady Elizabeth Anne Blount, who would go on to be influential in the formation of the Flat Earth Society, hired a commercial photographer to use a telephoto lens camera to take a picture from Welney of a large white sheet she had placed, touching the surface of the river, at Rowbotham's original position six miles (9.7 km) away. The photographer, Edgar Clifton from Dallmeyer's studio, mounted his camera two feet above the water at Welney and was surprised to be able to obtain a picture of the target, which should have been invisible to him given the low mounting point of the camera. Lady Blount published the pictures far and wide.^[15]

These controversies became a regular feature in the English Mechanic magazine in 1904–5, which published Blount's photo and reported two experiments in 1905 that showed the opposite results. One of these, by Clement Stratton on the Ashby Canal, showed a dip on a sight-line only 4 feet 9 inches (1.45 m) above the surface.^[16]

Refraction[edit]

Refraction of light can produce the results noted by Rowbotham and Blount. Because the density of air in the Earth's atmosphere decreases with height above the Earth's surface, all light rays travelling nearly horizontally bend downward (assuming a curve or change in air temperature along the line of sight). This phenomenon is routinely allowed for in levelling and celestial navigation.^[17]

If the measurement is close enough to the surface, light rays can curve downward at a rate equal to the mean curvature of the Earth's surface. In this case, the two effects of assumed curvature and refraction could cancel each other out and the Earth will appear flat in optical experiments.^[18]

This would have been aided, on each occasion, by a temperature inversion in the atmosphere with temperature increasing with altitude above the canal, similar to the phenomenon of the superior image mirage. Temperature inversions like this are common. An increase in air temperature or lapse rate of 0.11 degrees Celsius per metre of altitude would create an illusion of a flat canal, and all optical measurements made near ground level would be consistent with a completely flat surface. If the lapse rate were higher than this (temperature increasing with height at a greater rate), all optical observations would be consistent with a concave surface, a "bowl-shaped earth". Under average conditions, optical measurements are consistent with a spherical Earth approximately 15% less curved than its true diameter.^[19] Repetition of the atmospheric conditions required for each of the many observations is not unlikely, and warm days over still water can produce favourable conditions.^[20]

Other experiments[edit]

On 25 July 1896, Ulysses Grant Morrow, a newspaper editor, conducted a similar experiment on the Old Illinois Drainage Canal, Summit, Illinois. Unlike Rowbotham, he was seeking to demonstrate that the surface of the earth was curved: when he too found that his target marker, 18 inches (46 cm) above water level and five miles (8.0 km) distant, was clearly visible he concluded that the Earth's surface was concavely curved, in line with the expectations of his sponsors, the Koreshan Unity society. The findings were dismissed by critics as the result of atmospheric refraction.^[21][22]

See also[edit]

• History of geodesy

Notes[edit]

1. Jump up ^ The report in Zetetic Astronomy mentions a flag three feet (0.91 m) above the water.^[6]

References[edit]

1. Jump up ^ Association for Science Education (1942). School Science Review (London: John Murray) 24: 120. ISSN 0036-6811.  Missing or empty |title= (help)
2. Jump up ^ Richards-Jones, P (1968). "Astronomy at O level". Physics Education 3 (1): 35–39. Bibcode:1968PhyEd...3...35R. doi:10.1088/0031-9120/3/1/310. ISSN 0031-9120. 
3. ^ Jump up to: ^{a b} Correspondent (25 September 1901). "The British Association". The Times (London) (36569): 12. Mr Yule Oldham on his re-measurement of the curvature of the Earth along the Bedford Level. 
4. Jump up ^ Zetetic Astronomy, by 'Parallax' (pseud. Samuel Birley Rowbotham), [1881], at sacred-texts.com
5. Jump up ^ Rowbotham, Samuel (1867). Earth not a Globe. p. 14. Retrieved Jul 15, 2015. 
6. Jump up ^ Rowbotham, Samuel (1863). Zetetic Astronomy. p. 11. 
7. Jump up ^ Rowbotham, Samuel Birley (writing as "Parallax") (1881). Earth Not a Globe. London: Simpkin, Marshall. ISBN 0-7661-4945-5. 
8. Jump up ^ "The Rotundity of the Earth". Nature 1 (23): 581. 7 April 1870. Bibcode:1870Natur...1..581.. doi:10.1038/001581a0. 
9. Jump up ^ "The Form of the Earth: A Shock of Opinions" (PDF). The New York Times. 10 August 1871. Retrieved 2 November 2007. 
10. ^ Jump up to: ^{a b} Garwood, Christine (2007). Flat Earth. Macmillan. pp. 104–125. ISBN 0-312-38208-1. 
11. Jump up ^ Wallace, Alfred Russel (1908). My Life. pp. 368–9. 
12. Jump up ^ Hampden, John (1870). The Bedford Canal Swindle Detected & Exposed. London: A. Bull. 
13. Jump up ^ Correspondent (8 March 1875). "Spring Assizes". The Times (London). p. 11. 
14. Jump up ^ Oldham, H. Yule (1901). "The experimental demonstration of the curvature of the Earth's surface". Annual Report (London: British Association for the Advancement of Science): 725–6. 
15. Jump up ^ Michell, John (1984). Eccentric Lives and Peculiar Notions. London: Thames and Hudson. ISBN 0-500-01331-4. 
16. Jump up ^ Clement Stratton (20 January 1905). English Mechanic.  Missing or empty |title= (help)
17. Jump up ^ Umland, Henning. "A short guide to Celestial Navigation". Retrieved 14 November 2010. 
18. Jump up ^ Umland, pp. 2–5
19. Jump up ^ Lynch, David K; Livingston, William (2001). Color and Light in Nature. New York: Cambridge University Press. ISBN 0-521-77504-3. 
20. Jump up ^ Naylor, John (2002). "Mirages". Out of the Blue A 24-Hour Skywatcher's Guide. Cambridge, England: Cambridge University Press. ISBN 0-521-80925-8. 
21. Jump up ^ Simanek, Donald E. (2003). "Turning the Universe Inside-Out". Lock Haven University of Pennsylvania. Archived from the original on 21 November 2007. Retrieved 2 November 2007. 
22. Jump up ^ Teed, Cyrus; Morrow, Ulysses Grant (1905). The Earth a Concave Sphere. Estero, FL: Guiding Star. p. 160. ISBN 0-87991-026-7. 

Retrieved from "https://en.wikipedia.org/w/index.php?title=Bedford_Level_experiment&oldid=696085574"

Categories:

• History of geography
• History of Earth science
• Earth sciences

[주님과]

목사님 맞나요~??
자질이 안보이십니다..!!!!

[crystal sea]

정죄받아 마땅합니다.
거짓과 짝짝꿍 잘도 노시네요~! 목.사.님....

[여호수아]

님. 그리고 크리스탈님.
목사님과 장로님이 서로 싸우면 교회는 풍지박산이 되던데..
심심풀이 땅콩같은 이야기로
서로 감정상하지 마시길..

[주님과]

이정도로 상처 이야기를 ㅎㅎㅎㅎㅎ진정한 상처를 받은적 없으시군요 ㅎㅎㅎㅎ
이또한, 목사님께 향한 하나님의 축복이지요.
다만("아닌것을")극구 감싸고 두둔하시기에 성도들이 안타갑게 생각이됐어요..

[여호수아]

녜. 좋은 말로 받아 주셔서 감사합니다.^^

[crystal sea]

경찰관 아저씨가 참관인으로 오시면 더 좋고요~!^^

한 번 모여서 실험 한 번 해 보시자니까요?

제가 식사도 제공할께요~!^^

[crystal sea]

밥 묵자고 하는 것으로 보입니까? ㅎㅎ

[여호수아]

아ㅡ 곡률이요?
지구의 곡률은 사실은 일정하지가 않습니다.
지구 자전의 영향으로 적도 부근이 약간 부풀어 오른 호랑박의 모양을 하고 있지요.
그래서 적도 부근의 곡률은 평균보다 약간 작고
극지방으로 갈 수록 곡률은 약간 증가합니다.
그런데 또 지구의 중력문제가 국지적으로도 일정치가 않습니다,
즉 땅밑에 무거운 물질이 많으면 곡률은 증가하고
땅밑에 가벼운 물질이 많으면 곡률은 낮아 지겠군요.
그래서 석유가 많이 묻혀있는 사막지대에 신기루가? ㅎㅎㅎ 뻥입니다.
여하튼 지구의 곡률은 이론적으로 존재하는 평균치일뿐
그것이 어디에서나 똑같이 적용되는 것은 아닙니다.^^

[지구나그네]

그러니까 해수면 위에서 실험하는거 아닙니까? 실험이 왜 해수면 위에서 하는지 모르는군요

[여호수아]

해수면의 곡률이 다르다는 이야기 입니다.ㅎㅎ
즉 지구 중심에서 해수면까지의 길이가 어디나 다 같은 것은
완전 구형체.
지구 중심에서 해수면의 직선거리가 다르면 타원체.
지구는 완전구형이 아니라 타원체 입니다.

[crystal sea]

그러니까 해수면에서 실험을 해 보자니까요?
제가 성능 좋은 망원경을 제공한다니까요?
그냥 몸만 오세요~!

강릉으로 날 잡을까요?

어때요?

[땅허얌]

아무나 글쓸수있는 위키피디아가 자료인가요?????? 웃어도 되죠????

[지구나그네]

참고문헌 22 권이 있으니 클릭하고 들어가 보시오. 쓸데없는 자존심만 세우지 말고
pdf 로 된것도 있으니 열람해 보시오

[땅허얌]

참고문헌 읽어 보셨나요??? ㅎㅎㅎㅎ 참고문헌읽어보세요 전혀 다른내용입다

[하나님의 은총]

이논문은 그냥 이론...계산일뿐이죠...그것을 행한실험이 참인지 거짓인지는 이논문으로는 알수없잖아요. 계산한식이맞고틀리고는 둘째문제구요. 수억장의 지구사진은 위조가가능한데...이정도글은...눈감고도하죠.ㅎㅎ중요한것은 실제실험결과를 어떻게확인할것이냐입니다...그리고 돛단배 상단부터보이는건인정하시죠?? 그것은 평평이론도 인정하는바이구요...그래서 평평하지만 돛단배꼭대기부터 보이는 이유가 빛의굴절때문이라고했다면서요...평면이론가들이ㅎㅎ 벌써 거기서 게임셋입니다. 그건빛의굴절로절대설명되지않기때문이죠...지구나그네님도 이상하십니다. 200가지를 저에게 다보라고하지마시고 빛의굴절이 무엇인지 한번만들여

[하나님의 은총]

다보세요. 쉽습니다. 찾아서 링크걸어드리겠습니다.

[하나님의 은총]

http://m.terms.naver.com/entry.nhn?docId=924250&cid=47338&categoryId=47338 바로나오네요ㅋㅋ

[하나님의 은총]

다섯번째말씀드리는것 같은데 빛의굴절이란 그림처럼 서로다른 매질을 통과할때 그경계에서 입사각과 투사각이 달라짐으로 생기는것입니다. 같은 매질 내에서는 굴절하지않아요. 그렇게되면 세상이어떻게되겠습니까?? 눈으로는 모든사물의 위치를 제대로찾지못하겠죠. 빛이 꺾어져들어오니... 배에서 온 빛은 공기(균질한 단일매질)를 통과하여 우리눈으로 들어옵니다. 그러므로 굴절하지않아요...물론 수증기 증발처럼 아지랑이가있을경우 굴절하겠지만 그때는 사방팔방으로 빛이굴절되어 번지기는해도 배를 관찰할때''''언제 어디서나 누가하더라도 항상 배꼭대기부터 보이는 매번같은 결과치를얻을수없어요. 그러므로 그들의주장은 말도안되는

[하나님의 은총]

것입니다. 언제나 배꼭대기부터보이는것은 평평설에서도 인정하는바이고(그러니까 그것의 이유가 굴절이때문이라는 설명을 만들어놓았겠죠??) 그것의 설명이 터무니없는 것이드러났으므로 지구는 둥글다는것입니다. 저도 지구님말씀따라몇개보았으므로 제발 링크보시고 굴절이 무엇인지 확인하시고...돛단배문제에있어서 만큼은 그것이 구형설을 뒷받침한다...라고 인정해주시기바랍니다ㅎㅎ