I have, through general observation, theorized what I believe to be a logical explanation for the appearance of life on Earth. Although to me, this theory seems to provide a logical and rational explanation for the question of how life appeared on Earth, I have very little knowledge of Physics, and must assume that due to the shear simplicity of the model, this has not only been postulated before, but is indeed incorrect and contains a myriad of fallacious assumptions about physics, astronomy, cosmology etc. That being said, the sole purpose of this post is to learn what, specifically, is problematic, incorrect or impossible about what, to me is a very obvious explanation to the question being asked. So, as simply as possible, this is what I have concluded. Several components are required to allow for the possibility of life. First, an energy source, in our case the sun. Second, an environment with the required chemical composition to allow for a "primordial soup" scenario, given an energy source is provided. With what little knowledge of the Nebular Theory I do have, it is my understanding that the creation of the planets (in our solar system for the purposes of this discussion) was the result of a myriad of events, ultimately resulting in the collision of particles from the solar nebula which formed the planets in our solar system. Assuming that this theory is correct, it would then be logical to assume that (at least at one point in time), all of the planets in our solar system have very similar compositions, as they were formed from the same material. That being said, one could also conclude that because we know life is possible on Earth, it is also possible on the other planets of our solar system. So now the question of why Earth, and only Earth. Obviously there are an endless number of differences and variations between earth and the other planets of our solar system (size, atmosphere, gravitational pull, climate etc.) that could account (solely of jointly) for the lack of "life facilitating" conditions on the other planets in our solar system, however in my mind, only one difference ultimately serves as the determining factor. That difference, is distance from the sun. Essentially what I'm saying, is that the Earth is exactly the necessary distance from the sun to facilitate life. Obviously this would presuppose a few things. First, that this "life zone" or the portion of space which is located exactly the right distance from the sun to facilitate life, is equal to or greater than the dimensions of the Earth (otherwise, portions of the Earth would fall outside of this zone and be incapable of sustaining life). Next, this zone must not be greater than the current distance from Mars to Venus, otherwise life would co-exist on one or both of those planets (currently), as well as on Earth. Assuming that life on Earth has existed for approximately 3-4 billion years, and the sun is approximately 4 billion years old, this theory also presupposes that the growth of the sun thus far has not been sufficient enough to "push" the Earth out of the life zone. Because of the similarities between Earth and Mars, logic would seem to point to the boundaries of this zone falling close to the space Mars occupies. Eventually, as the sun continues to age and enlarge, Earth will near the inner-most boundary, and Mars will near the outer. As this process continues, the environment of Mars will begin to resemble Earth, and the conditions necessary for a "primordial soup" would exist. If the sun had an infinite life-span, and continued to expand, every planet in our solar system would produce life during the time which they occupied this zone. This is an extreme over-simplification of my observations, as well as pretty much every theory, construct and idea I've described within it. This is in large part due to my own ignorance on the topics, and in small part due to my desire to stop typing ASAP. What I'm interested in learning most here is the following: What's the most glaring problem with this theory? Has this theory been considered or examined in any form before? Would the other planets in our solar system, if placed in the exact location of the Earth, have Earth-like features, environments, atmospheres, chemical compositions etc? Again, I apologize in advance for the juvenile and ignorant nature of this post... Feel free to voice your disgust and contempt for me after reading this.