How did Galileo transition from qualitative observation to a semi-quantitative assessment of lunar features?

Answer

By analyzing the length of the shadows cast by lunar peaks.

By analyzing the length of the shadows cast by lunar peaks, Galileo inferred the relative scale of the features, moving towards a semi-quantitative assessment of heights comparable to terrestrial mountains.

How did Galileo transition from qualitative observation to a semi-quantitative assessment of lunar features?
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