QUESTION: I think I saw two different models for a Geocentric universe.  Then there's the heliocentric.

Isn't there a "fool proof" "absolute way" to determine which is correct via the different orbital VIEWS from earth ? ?



None of these models is correct.  The Universe really has to no center, and the Earth orbits around an insignificant star that lies from the center of its own galaxy...but you may be thinking of the Solar System, rather than the Universe.  

The original system had the Earth at the center, and the sun and planets all orbiting around Earth.  Once more accurate measurements were made, the Ptolemaic system assigned a series of ellipses inside ellipses to explain why the motion of the planets did not fit the earlier model.  But thne Galileo saw two things through his telescope that immediately let him know that the planets orbit the sun:

1.  He saw the moons of Jupiter and noted how the smaller moons orbited around that massive planet.

2.  He saw the phases of Venus, showing that it clearly orbited around the sun.  

Is that what you were looking for?

Paul Wagner

---------- FOLLOW-UP ----------

QUESTION: Thanks Paul,

These models;

and the Heliocentric, would sure have DRASTICALLY DIFFERENT views "from earth" over the period of 5 years, wouldn't they ? ?

Thus leading to an absolute reality of which is true.

Hence wouldn't that silence the Geocentrics forever ? ?



Actually, if you look at these models, they are pretty much the same--a modified Geocentric Solar System with everything but Earth orbiting around the Sun...and the whole Solar System orbiting around Earth.  One moves faster than the other and is on a larger scale, that's the main difference here.

Neither shows the more complicated Ptolemaic system, which involved a series of ellipses to explain why the planets apparent motion was so odd if they were supposed to be orbiting the Earth.  That's shown here:

Without understanding the physics involved there is no obvious visual difference between depicting the Solar System orbiting around Earth, and our current version, where all of the planets, including Earth, orbit around the Sun.  It's just a question of perspective. It's a bit like floating down a river, and describing the shore as moving past you.  But from shore, it looks as if the water is moving.  Who's right?

But once astronomers began to see the small perturbations in orbits caused by the mass of the Sun (and later, Jupiter) and they began to realize how big the Sun must be, then the idea that the Solar System might orbit around Earth became outdated.

Paul Wagner


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Paul Wagner


Astronomy and telescope making. Have made at least seven telescopes, both refractors and reflectors, and have spent 30 years looking at the nighttime sky.

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