But experts in geophysics say the claims were wrong then and still are now in social media posts making the same flawed argument.
The claim is based on the absence of locks in the Suez Canal. Locks are devices enabling vessels to be raised and lowered between placid bodies of water above sea level.
“Surveyors, engineers, and architects never factor in the supposed curvature of the earth into their projects. The Suez Canal is 100 miles long with zero curvature. If earth was a ball, there should be a 6,669ft drop from one end of the canal to the other, but the canal has no locks because the terrain through which it passes is flat,” the text in the post reads.
The claim is not new. It was made in 1885 by William Carpenter in his book, One Hundred Proofs That The Earth Is Not A Globe. Proof No.40 says: “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.”
That and subsequent claims based on the Suez Canal have been debunked previously, such as this blog, which includes a graphic showing why flat-earthers get confused about the canal.
Text with the blog’s graphic explains: “The surface of the water is equipotential. It has roughly the same distance to the Earth’s center of gravity. It is not necessary to dig 1666 ft in the middle of the Suez Canal. The engineers only need to ensure the base of the canal is below sea level for sea water to flow.”
Ian Jackson, emeritus professor of geophysics at the Australian National University, told AAP FactCheck canals such as the Suez are constructed without locks to operate at sea level along their entirety.
“For both the Suez and Panama Canals, sea level is the same at each end. The absence of locks along the Suez Canal has nothing to do with the earth being flat, but instead reflects the fact that, unlike the Panama Canal, the Suez Canal was built through low-lying land, that is land near sea level,” he said in an email.
Prof Jackson said excavation for the Suez Canal was done at uniform depth below local sea level.
“This allowed the water filling the canal now to a uniform depth of 24 (metres) to assume its equilibrium level upon a rotating near spherical earth.”
Prof Jackson also referred to the US Army Corps of Engineers web page on the Panama Canal’s construction which explains the designs of waterways built with and without locks.
Organisations such as NASA and science reference website ThoughtCo also explain how the Suez Canal operates without the need for locks because the Mediterranean and Red Sea’s Gulf of Suez have approximately the same water level.
As the Maritime Manual website explains: “The canal is formed through the isthmus at sea level, which means there is no elevation or depression in the water levels of the canal following the water level of the sea. Hence, there is no need for locks in the canal.”
The claim an absence of locks on the Suez Canal proves the earth is flat is false. An expert told AAP FactCheck there are no locks because the canal is built at near sea level. Excavation for the canal was at a uniform depth below local sea level, negating the need for locks.
False – The claim is inaccurate.