The Relationship Between the Physical Body and the Four Great Elements

Time, this illusory phenomenon, is truly wondrous. If a person could fly to the heavenly realm, stay for a few minutes, and then return, hundreds of years might have passed in the human world, spanning several human lifetimes. Yet, this person would remain as young as before, showing no signs of aging. Why is this so? Whether one ages or not lies with the physical body. The physical body is composed of the Four Great Elements (earth, water, fire, wind). Birth, cessation, and transformation occur; thus, the physical body continuously matures, develops, and changes. The Four Great Elements constitute the vital energy and blood necessary to sustain the physical body. If the vital energy and blood are active and circulating, the physical body receives ample nourishment, making it less prone to maturation and aging, and the person appears youthful. Practices like Qigong and various other methods can activate and circulate the vital energy and blood, nourishing the physical body. Therefore, those who practice well generally appear young. Time reveals the birth, cessation, and transformation of the Four Great Elements. The longer the time, the more apparent these changes become, and the more the physical body matures and ages. In summary, youth and aging depend on the developmental changes of the organization of the Four Great Elements. 

Why do the material bodies (rūpa-kāya) of heavenly beings (devas) not age? Because the composition of the Four Great Elements in the devas' material bodies differs from that in human material bodies. The Four Great Elements in humans are coarse and heavy, while those in devas are subtle and refined. Devas can fly, whereas humans cannot. When humans ascend to the heavens, influenced by the heavenly realm's environment and absorbing its particles of the Four Great Elements, the Four Great Elements of their material bodies also change, causing their physical bodies to become closer to those of the devas. When devas come to the human world and absorb the particles of the Four Great Elements from the human realm, their material bodies shift towards those of humans; the Four Great Elements also change, becoming similar to humans. For example, when devas from the Second Dhyāna Heaven, the Ābhāsvara (Radiant) Heaven, come to the human world and consume the earth's essence, the Four Great Elements of their material bodies immediately change. They can no longer fly freely and cannot return to the heavens. 

When the vital energy is full, one does not think of food. Vital energy is the material energy composed of the Four Great Elements. After sitting in meditation and cultivating concentration (samādhi) until the vital energy is sufficient, one does not feel hungry and can eat little or no food, while the body feels light and comfortable. This is because the Four Great Elements of vital energy differ from those of food. The Four Great Elements of vital energy are refined and subtle; sufficient vital energy can make the physical body float and rise. The Four Great Elements of food are coarse and heavy, causing the physical body to become heavy. Therefore, eating less and cultivating more concentration makes the body healthier. Even if food is highly nutritious, it is still a coarse, material form (rūpa-dharma), not the best nourishment; it is inferior to the nourishment provided by vital energy.