How to Test a Flat-Earth Claim

A claim becomes useful when it can be tested. The goal is not to win a shouting match but to turn a vague assertion into a prediction that can succeed or fail. 
 Step 1: State the Claim Clearly 
 “The horizon always rises to eye level” is testable. “They are hiding the truth” is not, unless it comes with specific evidence. 
 Step 2: Identify the Prediction 
 Ask what should happen before looking. If a model can explain every possible result afterward, it is not doing scientific work. 
 Step 3: Control the Variables 
 For visual claims, record distance, height, lens, date/time, weather, temperature gradient and location. For astronomy claims, record latitude, direction, time and date. 
 Step 4: Compare Models 
 The question is not “Can I invent a story?” The question is which model predicts the observation more simply, consistently and quantitatively. 
 Step 5: Keep the Result 
 Good experiments should be logged, even when they do not support your expectation. Reality is allowed to be inconvenient. 
 Claim Lab Worksheet 
 Use this worksheet before debating a claim: 
 
 Exact claim: Write one sentence without sarcasm. 
 Flat prediction: What should we observe if the claim is true? 
 Globe prediction: What should we observe if Earth is spherical? 
 Measurement plan: What tools, locations, times, heights, and distances are needed? 
 Failure condition: What result would make you less confident? 
 Repeatability: Can someone in another location check it too? 
 
 Example: “We Should Feel Earth Spin” 
 Flat-style claim: if Earth rotates, people should feel a violent motion. Prediction to test: Earth’s rotation should produce a large outward acceleration. Measurement: calculate centrifugal acceleration and compare it with gravity. Result: at the equator the effect is real but tiny, reducing apparent weight by roughly a third of one percent.