Link to purport by A C Bhaktivedanta Swami Srila Prabhupada

Transcript of Bhakti-Shastri class on this verse by Chaitanya

So how is Brahma’s abode destroyed? Krishna will describe that how even Brahma’s abode is temporary.

Bg 8.17

sahasra-yuga-paryantam
ahar yad brahmaṇo viduḥ
rātriṁ yuga-sahasrāntāṁ
te ’ho-rātra-vido janāḥ

Word for word: 

sahasra — one thousand; yuga — millenniums; paryantam — including; ahaḥ — day; yat — that which; brahmaṇaḥ — of Brahmā; viduḥ — they know; rātrim — night; yuga — millenniums; sahasra–antām — similarly, ending after one thousand; te — they; ahaḥ–rātra — day and night; vidaḥ — who understand; janāḥ — people.

Translation: 

By human calculation, a thousand ages taken together form the duration of Brahmā’s one day. And such also is the duration of his night.

sahasra-yuga-paryantam, There are sahasra-yugas, so Brahma Ji lives for thousand years, so the word yuga can be used for various terms, yuga is basically a large unit of time, ourselves we uses word like Kali-yuga, so it is one yuga, it is a unit of time Kaliyuga has different time duration and then Dwapar yuga has different time duration, so yuga basically refers to unit of time how much unit of time that will vary so here the word Yuga has used not for Kaliyuga, Dwapar Yuga, Treta Yuga, it is used for denoting the overall lifetime of Brahma Ji 

sahasra-yuga-paryantam
ahar yad brahmaṇo viduḥ

So for thousands Divya Yugas i.e. cycles of four yugas that is the day of Brahma, and after that there is the night of Brahma, so the day and night of Brahma are sahasra-yuga-paryantam and rātriṁ yuga-sahasrāntāṁ and after that Ratri is also yuga-sahasrāntāṁ, thousands yugas. te ’ho-rātra-vido janāḥ, this is also ratri. vido janāḥ. So the wise people understands this. So the point is there is a cycle of Brahma Ji’s life also that is there is a day which is very-very long and night also very-very long but ultimately it is temporary, and that is the point Srila Prabhupada makes over here: 

These “hundred years” by earth calculations total to 311 trillion and 40 billion earth years. By these calculations the life of Brahmā seems fantastic and interminable, but from the viewpoint of eternity it is as brief as a lightning flash. In the Causal Ocean there are innumerable Brahmās rising and disappearing like bubbles in the Atlantic Ocean. Brahmā and his creation are all part of the material universe, and therefore they are in constant flux.

So it is very difficult to conceive that someone who lives for trillion of years is like duration of bubbles in oceans. Srila Prabhupada compared that with bubbles in atlantics, bubble lasts for few moments some waves comes or something comes the bubbles bursts so actually once we conceive eternity, once we understand what is eternity it is going to last forever and ever and ever, then in comparison to the eternity, everything appears insignificant so that is why for us on relative perspective Brahma’s life may seems as phenomenal, but from eternity is as good as a (Srila Prabhupada has used two metaphor) bubble or lightning flash both temporary.

End of transcription.