The Earth orbits the Sun

Throughout these few rounds we will be discussing, in my understanding, the geocentric model vs. the heliocentric model (Pro arguing that the Earth revolves around the Sun, and Con arguing otherwise). I will request that the BoP be shared within this debate; simply disproving your opponent's points will not be enough to win this debate. Seeing as nothing was stated about rules, and that my opponent is asking for proof of the heliocentric model, I will jump straight into my arguments this first round. 1) Parallax This concept of parallax, or the apparent displacement of an object in relation to the background, may be one of the most prevalent pieces of evidence for a heliocentric theory. To summarize, parallax describes how we perceive closer objects moving in relation to objects farther away. I don't want to spend too long explaining this concept (though I will do so a bit), so I will post a link to a website if anyone reading this has any further interest in the topic [1]. Basically, when looking at a star in the sky, the concept of parallax would suggest that when the Earth is on one side of the Sun (assuming heliocentrism), a star in the distance would appear to move across the background as Earth continues its course around the Sun. In 1838, Friedrich Bessel performed an experiment and discovered that, when looking at a star in the distance (61 Cygni), there was in fact a shift in it's apparent position over the course of 6 months [2]. This alone should be proof of a heliocentric model. In a geocentric model, there would be no change, and the effects of parallax would not be witnessed. All stars would remain in the same position compared to the background regardless of the season and time of year. 2) Retrograde motion Another point on which to base my belief on a heliocentric model. This motion is seen in a similar fashion to the previous point. In this case, however, one must observe other planets in the solar system and the relative paths that are taken in the sky. Mars for example, would be seen traveling from right to left (over time) across the sky, but at some point will reverse direction, going left to right for a bit before returning to the previous motion. [3] With a heliocentric belief, all that needs to be in place is our current understanding of planets and their elliptic paths taken around the sun. This retrograde motion is then seen through the natural progression of the planets [4]. In a geocentric system, however, this retrograde motion would only be possible if the other planets (and Sun) revolved around epicycles; in other words, each planet would have a smaller orbit, and the center of that orbit would revolve around the earth [5]. While an argument could be made for this, there are many discrepancies when used to predict the position of certain planets. 3) Gravity When looking at the relative sizes of the Sun and the Earth, the Sun is massive. Weighing over 300,000 times the mass of Earth and being able to hold about 1,300,000 Earths within it, it is clear that the Sun takes up more mass and space in our solar system [6]. This being known, it makes sense that the earth would be revolving around the Sun and the other focus point of the elliptical orbit. In comparison, this would be similar to a 70 kg man (the standard mass of an adult [7]) in relation to a standard raindrop [8]. Common sense would say that the raindrop would revolve around the person, not the person revolving around the raindrop. I'll begin with these three arguments, and will proceed to introduce more should I need to. Looking forward to my opponent's statements. Sources: [1] - . http://simple.wikipedia.org... (yes, it's Wiki, but it's solely for a description of parallax) [2] - . http://cosmology.carnegiescience.edu... [3] - . http://www.lasalle.edu... [4] - . http://www.polaris.iastate.edu... [5] - . http://www2.astro.psu.edu... [6] - . http://coolcosmos.ipac.caltech.edu...- [7] - . http://hypertextbook.com... [8] - . http://www.bluebulbprojects.com...