A Flat Earth argument involving a WWII aircraft guidance system appeared to challenge the curvature of the Earth—until one question revealed that a key premise behind the argument was wrong.
I had David Weiss, “Flat Earth Dave” on my podcast. I don't believe the Earth is flat. Rather than simply saying Dave was wrong, I wanted to understand why he was wrong.
One of his arguments took a surprisingly long time to crack. Dave pointed to the German WWII Knickebein aircraft guidance system. His argument was simple:
Microwaves require line of sight.
Knickebein transmitted signals to bombers over distances where the curvature of a round Earth should have blocked that line of sight. Yet Knickebein worked.
Therefore, the Earth must be flat.
I spent time trying to explain how this could happen, while accepting Dave's premise that Knickebein used microwaves. Then I spoke with a ham radio operator. He became frustrated with me, and finally yelled:
“What frequency?!”
That was the question I should have asked first. I checked the frequency range for microwaves: Approximately 300 MHz to 300,000 MHz.
Then I checked Knickebein: 30–33 MHz. Knickebein wasn't operating at microwave frequencies.
That led me to look at what Knickebein actually was. When I looked at the antenna system, I discovered something:
The microwave dish in Dave's presentation wasn't a Knickebein antenna. Knickebein used a different antenna system—the “bent-leg” from which its name came.Now the frequency and the equipment pointed to the mistake:
Dave had identified Knickebein as a microwave system when it wasn't.
Suddenly, there was no microwave line-of-sight paradox to explain. I had spent time trying to disprove a conclusion, while accepting a false premise.
Most responses to flat-Earth claims start with:
“That's stupid. Everyone knows the Earth is round.”
That doesn't explain anything.
Dave's argument sounded convincing as several things appeared to confirm one another. He said Knickebein used microwaves, his slide showed a microwave dish, and he correctly pointed out the line-of-sight limitations associated with microwave communication.
The mistake was upstream.
I had been asking:
How could microwaves travel that far around a curved Earth?
I should have been asking:
Were they microwaves?
They weren't.
Before trying to disprove a conclusion, check the premises it's built upon.
About the Author
Daniel Stih (danielstih.com) is an aerospace engineer, software engineer, indoor environmental consultant, and author of 12 books. For more 30 years, he has investigated complex problems spanning engineering, technology, the built environment, and human decision-making. His work explores how evidence, assumptions, and systems shape the conclusions we draw—and whether we're solving the right problem. Learn more about his approach in Why I Think This Way.