Physics says that until we can equate what infinity requires we must look at it as if it is its own number with its own set of laws.
The earth didn't just "happen" to be in the right place at the right time. About 4.5 billion to 5 billion years ago the earth was a lot hotter, had very little if any atmosphere and was spinning a lot faster. A normal day is presumed to be around 3-4 hours at this point. We know now through isotopic analysis that the moon was once part of the earth, its still widely thought that the planet had a collision with another planet called "Theia", the reason that is now being discouraged as common understanding in the science community is because, had the moon been created from a collision we would have found foreign isotopic entities on it. Around 4 billion years ago, due to pressures, heat and the speed at which the planet was revolving, a chunk or series of, literally broke up and where caught in the earths gravitational base. These eventually collided together to become the moon, immediately tidally locked to the planet (meaning you only ever see one face of a moon). This created the right circumstance and interaction between the sun moon and earth that caused it to slow. About 200 million years down the track we have atmosphere and our first forms of life.