The Brihadaranyaka Upanishad, part of the Shukla Yajur Veda, is regarded as one of the oldest and most significant Upanishads, containing profound insights into the nature of reality, consciousness, and the universe.

The Upanishads primarily focus on exploring the nature of consciousness, the relationship between the individual self and the universal Self (Brahman), and the underlying unity of all existence, rather than providing detailed accounts of the physical universe.

The Brihadaranyaka Upanishad introduces the concept of Brahman as the ultimate reality, the source and essence of all existence, and the substratum of the entire universe.

The concept of Atman in Upanishadic cosmology refers to the individual soul or self, the innermost essence of a person, which is believed to be a part of or identical to the universal consciousness (Brahman).

According to the Upanishads, Atman and Brahman are not separate entities but are identical. The individual self (Atman) is seen as a manifestation or expression of the universal consciousness (Brahman).

The Brihadaranyaka Upanishad contains the renowned declaration, 'Aham Brahmasmi' (I am Brahman), which signifies the realization of the identity between the individual self (Atman) and the universal consciousness (Brahman).

The Upanishads generally regard the material world as a manifestation or expression of Brahman, the ultimate reality. It is seen as a projection or emanation from Brahman, rather than being separate or independent from it.

Meditation and self-inquiry are central practices in Upanishadic cosmology, aimed at attaining liberation (moksha) from the cycle of birth and rebirth (samsara) by realizing the true nature of reality and the identity of the individual self (Atman) with the universal consciousness (Brahman).

The Upanishads had a profound influence on the development of later Indian philosophical schools, particularly the Vedanta school. They laid the groundwork for the non-dualistic (Advaita) philosophy of Shankara and the qualified non-dualistic (Vishishtadvaita) philosophy of Ramanuja.

The Aitareya Upanishad introduces the concept of the cosmic egg (Hiranyagarbha) as the source of the universe, from which all creation emerged.

Prana, in Upanishadic cosmology, represents the vital life force or breath that animates all living beings and sustains the universe. It is considered to be a manifestation of Brahman, the ultimate reality.

The Upanishads often draw parallels between the individual self (microcosm) and the universal consciousness (macrocosm), suggesting that the inner world of the individual reflects the larger cosmic order.

The Katha Upanishad features the renowned parable of the chariot, where the chariot represents the body, the horses symbolize the senses, the reins represent the mind, and the charioteer represents the individual self.

The Upanishads primarily offer philosophical and spiritual insights into the nature of reality, including the origin and purpose of the universe. They explore the relationship between the individual self and the universal consciousness, rather than providing scientific explanations for the universe's creation.

Maya, in Upanishadic cosmology, refers to the illusion or veil that obscures the true nature of reality. It is the principle that creates the appearance of multiplicity and separateness, leading to the experience of the material world and the cycle of birth and rebirth.