You need to go back to Genesis 1:7 where God divided the firmament below from the firmament above. . . .

There was a THICK cloud covering over all the earth . . . . which protected the earth from UV raditation . . . .

Thick cloud covering . . .no sunlight shining down into the water vapor making rainbows . . . There were not rainbows until the firmament above was GONE . . . . or . . diminished.

Note that it is AFTER the flood that the longevity of man plummets.

BEFORE the flood, even after the "Fall" of man . . . humans lived hundreds and hundreds and hundreds of years . . .

(Which is why women have thousands and thousands of eggs in their ovaries. Women were designed to have kids for CENTURIES.)