Here's a link to an article written by Glenn Kreisberg, an engineer specializing in the radio frequency (RF) spectrum, entitled "Did ancient humans have knowledge of the electromagnetic spectrum?"
In it, the author examines evidence that ancient civilizations may have possessed knowledge of the shape of electromagnetic waves which would seem to have been well beyond any capabilities that would be possible under the conventional understanding of mankind's ancient history.
Among the evidence he offers are the similarities of the lobe-shaped chambers of the very ancient megalithic temples on the islands of Malta to the lobe-shaped radiation patterns (or antenna patterns) that characterize the properties of antennas used for transmitting or receiving radio waves at various frequencies.
We have already examined evidence in previous posts that these extremely ancient megalithic structures of Malta exhibit very sophisticated acoustic properties, which Mr. Kreisberg also touches on in his article, positing that ancient structures may have had some kind of long-distance communications function.
Mr. Kreisberg's article also mentions the possibility that depictions of dragons (particularly those in China, in which the shape of the dragon most closely parallels the shape of waves in the electromagnetic spectrum) might indicate a symbolic depiction of "an unseen force." This is interesting in light of other evidence we have seen which appears to link dragons to powerful electromagnetic discharge and possibly to plasma energy.
Most interesting, perhaps, is the examination in his article of "Irish round towers," which -- citing the work of other authors -- Mr. Kreisberg argues may have been deliberately designed to resonate at certain long-wavelength frequencies, for unknown purposes. These vibrations may have been related to positive brainwave energy (see this discussion of meditation and measurable waves produced by the brain, particularly in monks who have spent many thousands of hours in meditation). Mr. Kreisberg also suggests that these towers may have had some kind of yet-unknown long-distance communication purpose.
Finally, note that there are other indications of very subtle and sophisticated ancient ability in the field of electromagnetic sensitivity. This previous post discusses measurements by some researchers suggesting that the stones at Avebury Henge are arranged based on very subtle magnetic polarity. How the ancients could have measured that polarity and why they arranged them in this manner is still unknown.
If true, the ancient understanding of aspects of the electromagnetic spectrum would be yet another powerful piece of evidence that ancient humanity was far more advanced at a far earlier date than conventional historians will admit (most will not even discuss the possibility).
Many thanks to Glenn Kreisberg and others whose research into this important subject certainly bears careful consideration.