We call the shift in the apparent direction of a star due to Earth’s orbital motion stellar parallax. The Greeks made dedicated efforts to observe stellar parallax, even enlisting the aid of Greek soldiers with the clearest vision, but to no avail. The brighter (and presumably nearer) stars just did not seem to shift as the Greeks observed them in the spring and then again in the fall (when Earth is on the opposite side of the Sun).
Parallax
The apparent shift in the direction of an object as a result of the motion of the observer is called parallax.
Source & attribution
Astronomy 2e — Ancient Astronomy
OpenStax contributors · OpenStax, Rice University
CC BY 4.0. Text excerpted; whitespace normalised and empty cross-references removed; learning prompts added. No illustrations reproduced.
Source edition: 2024-10-17T15:19:16Z
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