"There are three general types of Qi. Heaven Qi is made up of the forces which the heavenly bodies exert on the earth, such as sunshine, moonlight, and the moon’s effect on the tides. Earth Qi absorbs the Heaven Qi and is influenced by it. Human Qi is influenced by the other two. Generally speaking, Heaven Qi is the biggest and most powerful. This Heaven Qi contains within it the Earth Qi, and within the Heaven and Earth Qi lives man, with his own Qi.
You must understand that all natural things, including man, grow within, and are influenced by, the natural cycles of Heaven Qi and Earth Qi. Since you are part of this nature (Dao), you must understand Heaven Qi and Earth Qi.. Then you will be able to adjust yourself, when necessary, to fit more smoothly into the natural cycle, and you will learn how to protect yourself from the negative influences in nature." *
* Dr. Yang, Jwing-Ming, The Essence of Taiji Qigong