Planet Earth is perfect. Everything about our world - its size, its distance from the Sun, its spin and tilt, its moon - is perfectly suited to our existence, and our planet's natural forces perfectly nurture life. A global weather system circulates and distributes fresh water to all corners of the globe, marine currents deliver nutrients to even the deepest reaches of the ocean, sunlight warms and energizes everything it touches, and powerful volcanoes create and fertilize the land. As a result, there is literally no part of our planet where life can?t be found.