From what i understand, one argument for a flat universe is the fact that the sum of the angles of a cosmic triangle is more or less equal to 180 degrees. What i don’t understand is how we calculate the angles. Most of what I’ve read online state that since we can measure the 3 sides of the cosmic triangle, we can use trigonometry to calculate the angles. But doesn’t the fact that we are using trigonometry to calculate the angles already presume the universe is flat rather than proofs it?
In: Planetary Science
>But doesn’t the fact that we are using trigonometry to calculate the angles already presume the universe is flat rather than proofs it?
No, the math works to calculate the angles regardless of the curvature of the underlying surface. What changes is the **sum of the angles** in a triangle. On a flat surface, the angles sum to 180 degrees. On a surface that is sphere-like, the angles sum to _more_ than 180 degrees. And on a surface that curves the other direction, the sum is _less_ than 180 degrees.
So we can calculate the angles based on the side lengths, and then when we add the angles, that sum tells us something about the curvature.
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