In the previous śloka, Bhagavān explained the extraordinary duration of Brahmā's day and night. His daytime lasts one thousand caturyugas, and his night lasts another thousand. Now Arjuna learns what happens to creation during these cosmic days and nights.

Bhagavān explains that the universe repeatedly moves between two conditions: vyakta [manifest] and avyakta [unmanifest]. The key teaching is that creation does not simply disappear into nothingness during dissolution. It returns to an unmanifest condition and becomes manifest again when the next cycle begins.

1. Our own waking and sleeping provide an example

Consider what happens when we wake up in the morning. The moment we become aware of our surroundings, our everyday world becomes active. We recognize our room, remember our responsibilities, think about the day's activities, and begin interacting with other people.

Our experiences involve deśa [space], kāla [time], and a world of different people and objects. We also experience a variety of thoughts and emotions. There may be happiness, disappointment, excitement, anxiety, or concern about the future. All these belong to our waking world.

Now consider what happens when we enter deep sleep. We are no longer aware of our room, our responsibilities, or the people around us. Our experience of time and space is no longer present in the ordinary waking sense. Our daily interactions stop, and our waking pleasures and worries are no longer experienced.

But this does not mean that the world has been destroyed. When we wake up, the familiar world of people, places, responsibilities, and experiences becomes available to us again.

During deep sleep, our individual world of waking experience has temporarily resolved into a dormant condition. This is called laya [resolution].

2. Brahmā's sleep brings a cosmic resolution

Bhagavān now extends this familiar example to the entire universe.

When an individual enters deep sleep, the person's experienced world becomes unmanifest to that individual. Other people who remain awake continue interacting with the world. But when Brahmā's cosmic night begins, the process occurs on a universal scale.

The manifest creation, with its countless beings, objects, forms, and activities, resolves into an unmanifest condition. This cosmic resolution is called pralaya [the dissolution of the manifest universe].

The distinction is important:

• Laya refers here to the resolution of an individual's experienced world during deep sleep.

• Pralaya refers here to the cosmic resolution associated with Brahmā's night.

In both cases, the teaching emphasizes resolution rather than absolute destruction.

3. The universe becomes unmanifest, not nonexistent

What does unmanifest mean?

Consider a pot of water heated until it evaporates. The water that was clearly visible in the vessel is no longer present in the same visible liquid form. But it has not become absolute nothingness. It has changed into water vapour, which may no longer be directly visible.

The physical example helps us understand the distinction between something being manifest and unmanifest.

Bhagavān applies this principle to creation. During Brahmā's night, the visible universe resolves into an unmanifest causal condition. The forms that were previously available for experience are no longer manifest, but the potential for their reappearance remains.

This unmanifest condition is called avyakta [unmanifest], prakṛti [primordial nature], or māyā [the causal power associated with manifestation].

These terms refer here to the causal condition into which the universe resolves and from which it subsequently emerges.

4. When Brahmā's day begins, creation manifests again

When Brahmā's night ends and a new day begins, the universe becomes manifest once more.

The unmanifest condition gives rise to visible forms, living beings, objects, and the entire field of interaction. Space, time, activity, and the world of plurality become available again. This is called sṛṣṭi [manifestation or creation].

The process can therefore be described as a recurring sequence:

Manifestation → Resolution into the unmanifest → Manifestation again.

The universe alternates between these two conditions, just as our own waking and deep-sleep experiences alternate.

This cyclic process is also described as expansion and contraction, or evolution and involution.

The essential point is that creation is not a single event followed by permanent disappearance. It undergoes repeated cycles of manifestation and resolution.

5. Why is this teaching important?

Bhagavān is continuing the discussion that began in 8.15, where He compared finite goals with the limitless reality.

Even Brahmā, the creator associated with the highest cosmic world, belongs to a universe that periodically becomes manifest and unmanifest. Therefore, no world within creation can be considered permanently secure merely because it lasts for an immense period.

This also helps us recognize why Bhagavān is fundamentally different from the created universe. Brahmā and the manifested worlds belong to the changing cosmic order. The limitless reality upon which creation depends is not confined to any particular cycle.

Thus, 8.18 teaches that the universe repeatedly emerges from an unmanifest condition when Brahmā's day begins and resolves into that same condition when his night arrives. Just as our personal world of experience becomes unavailable during deep sleep and reappears upon waking, the entire cosmic manifestation undergoes a corresponding process on a universal scale. Creation is cyclic, and even the vast universe remains within the order of change.