“Behind the Curve” is a documentary showing behind the scenes on what is happening in the flat-Earth community in the United States just before a flat-Earth conference. In a section, the film shows us how a flat-Earther did an experiment involving a ring laser gyroscope, which proved the very thing he tried to disprove: Earth’s rotation; and that he was unwilling to accept the result.
A ring laser gyroscope (RLG) is an instrument for measuring the change in orientation and rotational velocity. It is sensitive enough to measure Earth’s rotation easily.
Flat-Earthers claim that there is no instrument able to measure Earth’s rotation. Such claim arose from their ignorance. Ring laser gyroscopes —which are installed in some airplanes and ships— can easily detect and measure Earth’s rotation.
Many adherents of flat Earth have spent a lot of effort and money to perform various observations and experiments. They would buy expensive equipment, travel to the other side of the world, painstakingly designed the experiments in minute details, and performed large-scale experiments; all to prove the notion that Earth is flat. However, many of these experiments and observations have actually confirmed the Earth is a sphere beyond any doubt.
In most cases, they would not accept such conclusions, and instead, they misinterpret, refuse to accept, lie, and withhold information. Such behaviors are the results of confirmation bias. However, their results speak louder than their biased conclusions, and these are perfectly valid proofs that Earth is a sphere.
These are some of those observations and experiments, where flat-Earthers have painstakingly and extravagantly performed them, only to come up with the wrong conclusions and spectacularly demonstrating their confirmation biases to the entire world.