Bhavacakra

The bhavachakra or wheel of life is a visual teaching aid and meditation tool symbolically representing saṃsāra. It is found on the walls of Tibetan Buddhist temples and monasteries in the Indo-Tibetan region, to help both Buddhists understand the core Buddhist teachings. The image consists of four concentric circles, held by Yama, the lord of Death, with an image of the Buddha pointing to the moon metaphorically representing the possibility for liberation from the suffering of reincarnation.

Etymology

Bhavachakra, "wheel of life," consists of the words bhava and chakra.
bhava means "being, worldly existence, becoming, birth, being, production, origin".
In Buddhism, bhava denotes the continuity of becoming in one of the realms of existence, in the samsaric context of rebirth, life and the maturation arising therefrom. It is the tenth of the Twelve Nidanas, in its Pratītyasamutpāda doctrine.
The word Chakra derives from the Sanskrit word meaning "wheel," as well as "circle" and "cycle".

The term chakra is also used to denote yantras, variously known as ', ', etc.
Chakras are also part of the subtle body as taught by Tibetan Buddhism.

Legend has it that the historical Buddha himself created the first depiction of the bhavachakra, and the story of how he gave the illustration to King Rudrāyaṇa appears in the anthology of Buddhist narratives called the Divyāvadāna. Sahasodgata-avadāna, in the opening paragraphs of the work, describes the Buddha's instructions for creating the bhavachakra.

Explanation of the diagram

The bhavachakra is painted on the outside walls of nearly every Tibetan Buddhist temple in Tibet and India, to instruct non-monastic audience about the Buddhist teachings.

Elements of the ''bhavachakra''

The bhavachakra consists of the following elements:

The pig, rooster and snake in the hub of the wheel represent the three poisons of ignorance, attachment and aversion.
The second layer represents karma, with one half showing a person reaping the results of negative actions whilst the other half shows a person reaping the results of positive actions.
The third layer represents samsara and its Six Paths.
The fourth layer represents the twelve links of dependent origination.
The fierce figure holding the wheel represents impermanence. It is also Yama, the god of death.
The moon above the wheel represents liberation from samsara or cyclic existence.
The Buddha pointing to the white circle indicates that liberation is possible.

Symbolically, the three inner circles, moving from the center outward, show that the three poisons of ignorance, attachment, and aversion give rise to positive and negative actions; these actions and their results are called karma. Karma in turn gives rise to the six realms, which represent the different types of suffering within samsara.
The fourth and outer layer of the wheel symbolizes the twelve links of dependent origination; these links indicate how the sources of suffering that the three poisons and karma produce live within cyclic existence.
The fierce being holding the wheel represents impermanence; this symbolizes that the entire process of samsara or cyclic existence is impermanent, transient, constantly changing. The moon above the wheel indicates liberation. The Buddha is pointing to the moon, indicating that liberation from samsara is possible.

Hub: the three poisons

In the hub of the wheel are three animals: a pig, a snake, and a bird. They represent the three poisons of ignorance, aversion, and attachment, respectively. The pig stands for ignorance; this comparison is based on the Indian concept of a pig being the most foolish of animals, since it sleeps in the dirtiest places and eats whatever comes to its mouth. The snake represents aversion or anger; this is because it will be aroused and strike at the slightest touch. The bird represents attachment. The particular bird used in this diagram represents an Indian bird that is very attached to its partner. These three animals represent the three poisons, which are the core of the bhavachakra. From these three poisons, the whole cycle of existence evolves.
In many drawings of the wheel, the snake and bird are shown as coming out of the mouth of the pig, indicating that aversion and attachment arise from ignorance. The snake and bird are also shown grasping the tail of the pig, indicating that they in turn promote greater ignorance.
Under the influence of the three poisons, beings create karma, as shown in the next layer of the circle.

Second layer: karma

The second layer of the wheel shows two-half circles:

One half-circle shows contented people moving upwards to higher states, possibly to the higher realms.
The other half-circle shows people in a miserable state being led downwards to lower states, possibly to the lower realms.

These images represent karma, the law of cause and effect. The light half-circle indicates people experiencing the results of positive actions. The dark half-circle indicates people experiencing the results of negative actions.
Ringu Tulku states:
Propelled by their karma, beings take rebirth in the six realms of samsara, as shown in the next layer of the circle.

Third layer: the six realms of samsara

The third layer of the wheel is divided into six sections that represent the six realms of samsara, or cyclic existence, the process of cycling through one rebirth after another. These six realms are divided into three higher realms and three lower realms. The wheel can also be represented as having five realms, combining the God realm and the Demi-god realm into a single realm.
The three higher realms are shown in the top half of the circle:

God realm : Also known as six heavens in desire worlds. The gods & goddesses lead long and enjoyable lives full of pleasure and abundance, but they spend their lives pursuing meaningless distractions and never think to practice the dharma. When death comes to them, they are completely unprepared; without realizing it, they have completely exhausted their good karma and they suffer through being reborn in the lower realms.
Demi-god realm : the demi-gods have pleasure and abundance almost as much as the gods, but they spend their time fighting among themselves or making war on the gods. When they make war on the gods, they always lose, since the gods are much more powerful. The demi-gods suffer from constant fighting and jealousy, and from being killed and wounded in their wars with each other and with the gods.
Human realm : humans suffer from hunger, thirst, heat, cold, separation from friends, being attacked by enemies, not getting what they want, and getting what they do not want. They also suffer from the general sufferings of birth, old age, sickness and death. Yet the human realm is considered to be the most suitable realm for practicing the dharma, because humans are not completely distracted by pleasure or by pain and suffering. There are four human realms in existence, including Jambudvīpa, Pūrvavideha, Uttarakuru and Aparagodānīya.

The three lower realms are shown in the bottom half of the circle:

Animal realm : wild animals suffer from being attacked and eaten by other animals; they generally lead lives of constant fear. Domestic animals suffer from being exploited by humans; for example, they are slaughtered for food, overworked, and so on.
Hungry ghost realm : hungry ghosts suffer from extreme hunger and thirst. They wander constantly in search of food and drink, only to be miserably frustrated any time they come close to actually getting what they want. For example, they see a stream of pure, clear water in the distance, but by the time they get there the stream has dried up. Hungry ghosts have huge bellies and long, thin necks. On the rare occasions that they do manage to find something to eat or drink, the food or water burns their neck as it goes down to their belly, causing them intense agony.
Hell realm : hell beings endure unimaginable suffering for eons of time. In Buddhist cosmology there are eighteen different types of hells, each inflicting a different kind of torment. In the hot hells, beings suffer from unbearable heat and continual torments of various kinds. In the cold hells, beings suffer from unbearable cold and other torments.

Among the six realms, the human realm is considered to offer the best opportunity to practice the dharma. In some representations of the wheel, there is a buddha or bodhisattva depicted within each realm, trying to help sentient beings find their way to nirvana.

Outer rim: the twelve links

The outer rim of the wheel is divided into twelve sections that represent the Twelve Nidānas. As previously stated, the three inner layers of the wheel show that the three poisons lead to karma, which leads to the suffering of the six realms. The twelve links of the outer rim show how this happens—by presenting the process of cause and effect in detail.
These twelve links can be understood to operate on an outer or inner level.

On the outer level, the twelve links can be seen to operate over several lifetimes; in this case, these links show how our past lives influence our current lifetime, and how our actions in this lifetime influence our future lifetimes.
On the inner level, the twelve links can be understood to operate in every moment of existence in an interdependent manner. On this level, the twelve links can be applied to show the effects of one particular action.

By contemplating on the twelve links, one gains greater insight into the workings of karma; this insight enables us to begin to unravel our habitual way of thinking and reacting.
The twelve causal links, paired with their corresponding symbols, are:

Avidyā lack of knowledge'a blind person, often walking, or a person peering out
Saṃskāra constructive volitional activity'a potter shaping a vessel or vessels
Vijñāna consciousness'a man or a monkey grasping a fruit
Nāmarūpa name and form ''two men afloat in a boat
Ṣaḍāyatana six senses a dwelling with six windows
Sparśa contact 'lovers consorting, kissing, or entwined
Vedanā feeling'an arrow to the eye
Tṛṣṇa craving or thirst'a drinker receiving drink
Upādāna grasping or attachment'a man or a monkey picking fruit
Bhava coming to be'a couple engaged in intercourse, a standing, leaping, or reflective person
Jāti being born'woman giving birth
Jarāmaraṇa old age and death'corpse being carried''