Great Salt Lake Flat Earth Curvature Investigation
On April 27, 2024, the Beehive Skeptics Foundation partnered with local group Utah Flat Earth to perform a joint observational experiment across the Great Salt Lake. The objective was to test for physical obstruction caused by Earth's curvature across a 25.643-mile sight line between Antelope Island and the southern shoreline near Interstate 80.
Test Criteria
Because the Earth is a sphere, the surface of a large lake curves gently over long distances—behaving like a very low, invisible hill between two far-apart points. If the Earth were flat, a light held near the water level on one shore would shine straight across to an observer on the opposite shore without needing any elevation to see over the horizon.
Many proponents of flat Earth have performed tests with lasers at or near water level, and insist that this needs to be done on a cold day with no wind. A similar test was shared with us that was performed over the Great Salt Lake. But we had questions. Why does it need to be on a cold day with no wind? Why does it need to be close to water level? Why are the results inconsistent? These requirements are suspiciously close to the perfect conditions for a "superior mirage."
To test this accurately, we had to control for optical distortions:
- Understanding Superior Mirages: Over cold water like the Great Salt Lake, a layer of cold air often sits trapped right beneath a layer of warmer air. This temperature inversion acts like a lens, bending (refracting) light rays downward over the horizon curve. This optical effect—called a superior mirage—can project images or light beams from behind the curvature of the Earth, making distant objects appear floating or visible when they should be hidden.
- Mitigating Mirage Risk at 23 Feet: Superior mirages are strongest directly at water level where the temperature boundary is sharpest. By establishing our primary viewing location on a hill 23 feet above water level, we raised our sight line above the dense thermal inversion layer. This minimized atmospheric refraction, ensuring we were observing true geometric lines of sight rather than a bent light reflection.
- Finding the Horizon Cut-Off: The test covered a total distance of 25.643 miles. Walking down the mountain slope from an initially high point allowed us to make sure we could clearly see the light. Once we were able to train our eyes on the light, we could reduce our elevation until the sharp dot vanished behind the horizon at 205 feet. This measured value matched theoretical predictions within a 21% margin of error. Since our instruments weren't exact (they didn't need to be since according to the flat Earth model, we should have been able to see the light all the way down to the shoreline), this was well within our 30% field test tolerance.
Initial Scouting Test (03/09/2024)
Prior to our joint test with Utah Flat Earth, Beehive Skeptics conducted a preliminary trial on March 9, 2024, across a 25.89-mile baseline between Buffalo Point on Antelope Island and a hill near I-80. This scouting run helped verify GPS points, evaluate flashlight visibility, and refine our altimeter logging protocols ahead of the full April group experiment.
Watch "Beehive Skeptics Investigates Flat Earth!" on YouTube
Official Joint Test Video (04/27/2024)
In our official test we did prioritize working with the group over video recording. So the pre-test is better quality. Though both videos prove that since it is in the dark, this test is better performed in person, however in this video you can listen to the Utah Flat Earth group's reactions. Watch the full documentation of our joint field test with Utah Flat Earth:
Watch "Flat Earth Test - Official" on YouTube
Conclusion
Measured Height Before Visibility Lost: 205 Feet
Based on the Omni Earth Curvature Calculator, a 25.643-mile distance with a 23-foot viewing height predicts 260 feet of curvature. Using hiking altimeters with a planned 30% range variation, we measured visibility loss at 205 feet. This was within 21% of the theoretical calculation and well within expected field margins.
In this test, both parties (Beehive Skeptics and Utah Flat Earth) agreed there were no land masses between the two viewing points, and that the light was clearly dipping behind an obstruction. Beehive Skeptics knows and understands this obstruction to be the curvature of the Earth over the body of water, making this test a visual demonstration of the Earth's curvature.
When extraordinary claims are put to the test using empirical controls and repeatable methodology, the physical curvature of the Earth is clearly measurable across large bodies of water.
We commend the members of Utah Flat Earth for engaging in open dialogue and participating in direct scientific field testing. They have requested a follow-up daytime test using mirrors and high-zoom cameras in order to get a clearer understanding of what is obscuring their view. However, contact has been slow and limited. We believe that science and truth are learned not just by knowledge, but through experimentation. So if you disagree with our methodology, or would like to perform an experiment yourself, please contact us! Science is also repeatable, so we would love another chance to collect repeatable data.
Interested in joining our next field investigation or testing an extraordinary claim? Check our upcoming events or apply for the Paranormal Challenge.