See: The True History of the Sphinx of Ancient Egypt – The True History of the Sphinx of Ancient Egypt

The unit of measurement “the meter” was known by the Egyptians of the Fourth Dynasty. The appearance of two Egyptian units of measurement, at par, within the measures of the main sarcophagi of Gizeh, demonstrates that they knew the meter, since the relationship between these two units of measurement always gives the value of both units of measurement in meters. See: (DOC) The “Mathematical Meter” of the 4 th Dynasty

‘By the fifth century BCE, the Greeks had firmly established that the earth was a sphere. Although they knew it was a sphere, they didn’t know how big the sphere was.

The philosopher Plato (400 BCE) declared the earth’s circumference to be 64,412 kilometers (40,000 miles). Some 150 years later, the mathematician Archimedes estimated it to be 48,309 kilometers (30,000 miles). It’s not known exactly how Plato or Archimedes arrived at their calculations, but Plato’s measurement was off by sixty percent and Archimedes’ by twenty percent. At least they were making progress.

Observations and calculations by two later Greeks, Eratosthenes and Posidonius, finally resulted in accurate estimates of the size of the earth.

In the third century BCE, Eratosthenes, a Greek librarian in Alexandria, Egypt, determined the earth’s circumference to be 40,250 to 45,900 kilometers (25,000 to 28,500 miles) by comparing the Sun’s relative position at two different locations on the earth’s surface. Because of differences in translations or interpretations of his records, and his own methodological errors, the exact figures are in dispute. Today, the earth’s circumference is usually accepted to be 40,096 kilometers (24,901 miles). If you take the lowest estimate attributed to Eratosthenes, his error was less than one percent—a phenomenal calculation.’ See: Determining the earth’s size