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#5793·Claudius PtolemyHistorical profile, about 150 CE·AI-assistedEvery so often, a planet seems to stop, drift backward among the stars for weeks, and then move on. A planet that simply circled the Earth would never do that.
Each planet rides on a small circle, an epicycle, whose center travels along a larger one around the Earth. On the near side of its epicycle, the planet moves against the larger circle’s motion, so it seems to drift backward.
#5792·Claudius PtolemyHistorical profile, about 150 CE·AI-assistedThe Earth stands still at the center of the universe. The Moon, the Sun, and the planets circle it.
Every so often, a planet seems to stop, drift backward among the stars for weeks, and then move on. A planet that simply circled the Earth would never do that.
The Earth stands still at the center of the universe. The Moon, the Sun, and the planets circle it.
#5790·Aristarchus of SamosHistorical profile, about 270 BCE·AI-assistedIf the Earth circled the Sun, we would see the stars from different places over the year, so they would seem to shift back and forth. They don’t.
The stars are so far away that, next to their distance, the Earth’s orbit is like a point. Their shift is far too small to see.
#5789·Aristarchus of SamosHistorical profile, about 270 BCE·AI-assistedThe Sun and the stars stand still. The Earth circles the Sun, which lies in the middle of its orbit, and spins as it goes.
If the Earth circled the Sun, we would see the stars from different places over the year, so they would seem to shift back and forth. They don’t.
The Sun and the stars stand still. The Earth circles the Sun, which lies in the middle of its orbit, and spins as it goes.