The three worlds are known as Bhuh, Bhuvah and Svah (Patala, Martya and Svarga)

Expressions researched:
"Patala, Martya and Svarga" |"These three worlds are known as Bhuh, Bhuvah and Svah"

SB Canto 3

The dissolution of the three worlds is effected by the incarnation of darkness, Rudra, represented by the fire of eternal time which blazes over the three worlds. These three worlds are known as Bhūḥ, Bhuvaḥ and Svaḥ (Pātāla, Martya and Svarga).

SB 3.11.28, Translation and Purport:

At the end of the day, under the insignificant portion of the mode of darkness, the powerful manifestation of the universe merges in the darkness of night. By the influence of eternal time, the innumerable living entities remain merged in that dissolution, and everything is silent.

This verse is an explanation of the night of Brahmā, which is the effect of the influence of time in touch with an insignificant portion of the modes of material nature in darkness. The dissolution of the three worlds is effected by the incarnation of darkness, Rudra, represented by the fire of eternal time which blazes over the three worlds. These three worlds are known as Bhūḥ, Bhuvaḥ and Svaḥ (Pātāla, Martya and Svarga). The innumerable living entities merge into that dissolution, which appears to be the dropping of the curtain of the scene of the Supreme Lord's energy, and so everything becomes silent.