Astronomy Practice Exam 2025 – Complete Preparation Guide

During Galileo's time, the prevailing belief was that the heavens were perfect, immutable, and unchanging. This idea was deeply rooted in Aristotelian philosophy and the Ptolemaic model of the universe. However, several observations made during this period began to challenge that notion, leading to a significant shift in our understanding of the cosmos.

Galileo's discovery of moons orbiting Jupiter provided clear evidence that not all celestial bodies revolve around the Earth, as previously thought in the geocentric model. This was a crucial observation that suggested a more complex and dynamic universe, implying that there are other centers of motion in the cosmos.

Observations of sunspots also played a critical role. Sunspots are temporary phenomena on the solar surface that appear as spots darker than the surrounding areas. Their existence indicated that the Sun was not a perfect, unblemished sphere, as had traditionally been believed. This observation challenged the idea of the Sun's heavenly perfection.

Additionally, Tycho Brahe's meticulous measurements of stellar distances brought forth a wealth of data that contradicted the existing models of the cosmos. Although Tycho himself supported an Earth-centered system, his observations highlighted irregularities and supported a view of the universe that was more complex than previously accepted.

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