How Were Daily and Annual Cycles Explained Before Copernicus?

  • Thread starter Thread starter Front Office
  • Start date Start date
  • Tags Tags
    Cycles
AI Thread Summary
Before Copernicus, the daily and annual cycles were explained through various geocentric models, where the Earth was often viewed as stationary but sometimes thought to rotate daily. Most people did not accept the idea of Earth's rotation, fearing it would lead to chaotic winds due to the atmosphere not moving with the Earth. Annual cycles were attributed to complex movements of celestial spheres, with some theorists suggesting that the Sun was a hole in a rotating crystal sphere. A few early thinkers, like Heraclides Ponticus, proposed that the Earth rotated on its axis while remaining at the center of the universe. Overall, the understanding of celestial mechanics was diverse and often speculative, lacking the clarity provided by later heliocentric models.
Front Office
Messages
16
Reaction score
0
In the time before Copernicus introduced the idea that the planets including the Earth orbit the Sun, how were the daily and annual cycles reconciled?

I have always assumed that in the Copernican view the Earth orbits the Sun once each year. But not till today did I wonder about the 24-hour daily cycle: In pre-Copernican time, the Earth must have been seen as rotating once each day. That is, the Earth might have been seen as the center of the universe, but it must have been seen as rotating every day even if it was considered otherwise stationary in space.

If the Sun was regarded as circling the Earth ONCE EACH DAY, then how were the annual cycles explained? Just wondering if anyone has any insight into this.
 
Last edited by a moderator:
Physics news on Phys.org


Various people thought various things. But most DID deny
that the Earth rotated. They thought that the atmosphere
would not go round with the solid earth, and so there would
be perpetual high winds. Of course, the existence of the Coriolis
effect shows there is a bit of truth in that.

Annual changes had then to be accounted for by various ad hoc
theories such as that of the celestial spheres doing complicated
dances

One has to remember that people knew nothing of distant bodies'
natures. One thory was that the sun was a hole in a rotating crystal
sphere, through which the external fires showed - really not a thing at
all, but more like a moving window.
 


Front Office said:
In the time before Copernicus introduced the idea that the planets including the Earth orbit the Sun, how were the daily and annual cycles reconciled?

I have always assumed that in the Copernican view the Earth orbits the Sun once each year. But not till today did I wonder about the 24-hour daily cycle: In pre-Copernican time, the Earth must have been seen as rotating once each day. That is, the Earth might have been seen as the center of the universe, but it must have been seen as rotating every day even if it was considered otherwise stationary in space.

If the Sun was regarded as circling the Earth ONCE EACH DAY, then how were the annual cycles explained? Just wondering if anyone has any insight into this.

Middling is right that various models were proposed. FWIW here is a paragraph from Wkpd that illustrates the diversity of opinion:
http://en.wikipedia.org/wiki/Geocentric_model#Geocentrism_and_rival_systems
==quote==
Not all Greeks agreed with the geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire.[19] Hicetas and Ecphantus, two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe.[20] Such a system still qualifies as geocentric. It was revived in the Middle Ages by Jean Buridan. Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but this is no longer accepted.[21] Martianus Capella definitely put Mercury and Venus in orbit around the Sun.[22] Aristarchus of Samos was the most radical. He wrote a work, which has not survived, on heliocentrism, saying that the Sun was at the center of the universe, while the Earth and other planets revolved around it.[23] His theory was not popular, and he had one named follower, Seleucus of Seleucia.[24]
==endquote==

You might be interested by what Wkpd says about Aristarchus (born 310 BC). He had a fullyworked heliocentric system with the sun stationary and the sphere of fixed stars stationary. He had the known planets in the correct order of distance from the sun. And of course the Earth rotated.
http://en.wikipedia.org/wiki/Aristarchus_of_Samos#Heliocentrism
This quotes a book by Archimedes, which has survived and which describes Aristarchus' system.

I think the answer is that most people did NOT think of the Earth as rotating daily, but curiously enough some people did have that idea going back to before the 3rd century BC.

Your other question about how they handled the season variation in the course of the sun is discussed some in that "heliocentrism" article. For example Anaximander imagined a large ring or wheel rotating in the east-west plane around the Earth which could SHIFT northwards in summer and southwards in winter. Like a hula-hoop which a person makes rise and fall while spinning. The article shows a picture of his system with its two wheels, one for sun and one for moon, with the sun wheel in both the summer and winter configurations.
 
Last edited:
I think it's easist first to watch a short vidio clip I find these videos very relaxing to watch .. I got to thinking is this being done in the most efficient way? The sand has to be suspended in the water to move it to the outlet ... The faster the water , the more turbulance and the sand stays suspended, so it seems to me the rule of thumb is the hose be aimed towards the outlet at all times .. Many times the workers hit the sand directly which will greatly reduce the water...
Back
Top