พระอาจารย์อธิบายว่าแรงโน้มถ่วงที่นิวตันค้นพบก็อาศัยการชี้นำของฝ่ายกุศล และเปรียบแรงโน้มถ่วงว่าเป็นส่วนหนึ่งของหลักอายตนะ คือแรงดึงดูดที่แต่ละภพภูมิ ตั้งแต่โลก นรก สวรรค์ พรหม จนถึงพระนิพพาน ล้วนมีในแบบของตนเองPra Ajarn explains that even Newton's discovery of gravity relied on guidance from the wholesome, and likens gravity to a form of the sense-base (āyatana) principle — an attracting force that every realm, from earth to hell, heaven, the brahma world, and even nibbana, has in its own way.
A student asked: what is gravity? What category of matter or energy wave does it belong to? Is it related to the sense bases (āyatana)? And do other universes, heaven, and hell have gravity too?
Pra Ajarn explained that gravity is the force that draws things to stay fixed to the earth's surface, keeping them from floating off into space. In science, Sir Isaac Newton discovered gravity while lying under an apple tree when a fruit fell on his head. Pra Ajarn pointed out that such a discovery relies on guiding him as an inner voice of understanding — because across countless generations of people before him, no one else had ever thought of it; only Newton managed to grasp it.
As for its scientific classification, he suggested asking a scientist directly. But regarding its relation to the sense bases, he cited the teaching of a revered elder teacher: the eye is a sense base that draws in sights, the ear draws in sounds, the tongue draws in tastes, the body draws in touch, and the mind draws in mental objects. The sense base of nibbana likewise draws in nibbana for those who have attained the path and fruit. So earth's gravity is likely part of this same principle of sense bases — the earth has a sense base that draws objects down to itself.
Other universes, hell, and heaven operate on this same principle. Hell draws those heavy with demerit; heaven draws those rich in merit; the brahma realms draw those with especially pure minds; and the sense base of nibbana draws those who have exhausted all defilements. They're simply not called "gravity," since that term requires a value provable by scientific means.