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In ancient times people wondered where does the Sun go at night. This question was answered in different ways. Some explained it in legends. The Greeks believed the sun was a chariot driven by the Sun God Phoebus Apollo and he rested in his palace in the western horizon. In ancient Egypt the God Ra was the Sun and traveled on a barge daily through the heavens and upon reaching the western horizon began a nightly journey through the underworld battling evil. Other people simply stated what they observed. The Sun rose in the east and set in the west.
Astronomers starting with the Ancient Greeks started to form serious theories about the sun and why it seemed to rise in the east and travel across the Earth’s skies. The biggest discovery is that celestial bodies orbit each other. The famed astronomer Ptolemy made the geocentric model. This model based the Earth as the center of the universe with every other celestial body orbiting around it. This seemed at the time to be the right explanation. However it did not account for the strange movement of heavenly bodies. Further observations led to the Copernicus model we now know this model explain where the Sun goes each night.
According to the Copernicus heliocentric model the Earth orbits the sun. This has an interesting effect in that at any given time only one half of the Earth is exposed to sunlight. The side that is shadowed is where the planet experiences night. With the Earth’s rotation of 24 hours each side of the Earth gets 12 hours of daylight and 12 hours of darkness. This means that the Sun really doesn’t go anywhere. We are the ones that actually move away from the Sun each night.
So why is this so important? Why is it any different from being on a planet where only one side is always day and the other is always night? The reason is climate regulation. The reason that life is able to thrive on our planet is because of the relatively moderate temperatures. If the Earth was too hot or too cold the conditions would not be conducive to life. One side would be a frozen wasteland to outdo even Antarctica and the Sun side would be a blistering desert.
However recent discoveries have pointed to the possibility of a habitable zone for planets that don’t rotate. This zone would be on the border between these hot and cold regions. Still most of it is still speculation until we can actually find life on other planets.
We’ve also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.