When the Sky Became Blue: How the Torah Anticipated Earth’s Atmospheric Science

The Sages explain that the celestial bodies — the sun, moon, and stars, were created on the first day, but only became visible from Earth on the fourth day, when the atmosphere was refined. As Ramban (Nachmanides) explains regarding the verse “Let them be for lights in the sky to give light upon the earth - He added that their light should reach the earth.”

Modern science agrees that Earth’s atmosphere was initially so dense and opaque that sunlight could not penetrate it efficiently. The primordial world was dim, almost dark. Only after the atmosphere stabilized — when “the heavens” as we know them were formed, did sunlight finally reach Earth’s surface, allowing the sun, moon, and stars to become visible from below.

Why Is the Sky Blue?

If air and water are both colorless, why do the sky and sea appear blue?

Sunlight is white light, containing all the colors of the spectrum simultaneously. As it passes through Earth’s atmosphere, the rays are scattered — and the Creator decreed that the dominant color that would “spread” across the sky would be blue (tekhelet).
Without sunlight, both the sky and water would be completely black — exactly as the Torah describes: “Darkness was upon the face of the deep… above the waters.” (Bereishit 1:2)

The sea mirrors the color of the sky: when clouds turn gray, the sea turns gray as well. The “Black Sea,” for example, appears dark not because its water is black, but because the mist and fog above it block light, making it look black.

During storms, light cannot pass freely through the atmosphere, obscuring our view of the celestial bodies. Thus, the visibility of the sun, moon, and stars depends entirely on the condition of the sky.

On the second day, when the “firmament” (atmosphere) was formed and vast waters were separated from the surface, it was likely still thick and moist, preventing light from fully reaching Earth. On the fourth day, the atmosphere cleared, and for the first time, humanity could see the sun, moon, and stars shining through the heavens.

An Ancient Scientific Truth

It is astonishing how the Torah connects the formation of the heavens with the ability to see the celestial lights. Ibn Ezra highlights the phrase “And God set them in the firmament of the heavens” and notes that this act — “setting”, parallels the rainbow: “Do not be surprised by the word ‘He set’, for it is like *‘I have set My rainbow in the cloud.’” (Bereishit 1:17)

Common sense would suggest that if the sun, moon, and stars exist in space, their light would automatically be visible from Earth. However the Torah teaches otherwise: the refinement of the atmosphere was required, to make their light visible.

This is a scientific concept about atmospheric transparency written over 3,300 years ago.

Why Doesn’t the Torah Describe the Creation of the Stars in Detail?

Some mistakenly believe that the sun, moon, and stars were created on the fourth day. However, all classic commentators clarify: “They were created on the first day, and on the fourth day God commanded them to be suspended in the firmament.”

On the fourth day, Earth’s skies were perfected — the atmosphere was stabilized, allowing consistent transmission of light to the surface. Only then could humanity see the “lights” that separate day from night and serve as markers for “signs, seasons, days, and years.”

This is supported by the verse: “God made the two great lights… the lesser light to rule the night, and the stars.” (Bereishit 1:16)

Notice that the stars are mentioned only briefly, almost as an aside, despite their vast number. Elsewhere, the Torah emphasizes their immensity: “Look now toward the heavens and count the stars, if you are able to count them.” (Bereishit 15:5) King David also marvels: “He counts the number of the stars; He calls them all by name.” (Tehillim 147:4)

The Sages (Berakhot 32b) were the first in history to describe hundreds of billions of stars and galaxies, long before the invention of the telescope — when the human eye could see no more than about 6,000 stars. Why, then, does the Torah not elaborate on the creation of such an awe-inspiring multitude?

The answer lies in the term “lights”. The moon reflects sunlight and illuminates the night; it is therefore called “the lesser light.” Without it, the nights would be completely dark. Beyond serving as a calendar for months and festivals, the moon acts as a divine lamp in the sky. The stars, shining even less brightly, are thus included under the moon’s “rule of the night.”

The Torah therefore is not describing the creation of the celestial bodies on the fourth day, but rather the arrival of their light to Earth — the moment when the refined atmosphere finally made them visible. 

“To give light upon the earth.” (Bereishit 1:15) The Torah focuses on what occurred on Earth — the transformation that allowed humanity to behold the splendor of the heavens.

• Plant life was created before animals — consistent with modern understanding that vegetation produces the oxygen necessary for life.

• Until the fourth day, light existed but was dim and scattered; only after the atmosphere cleared could sunlight reach Earth directly.

• The sun, moon, and stars were created on the first day; on the fourth, their light was revealed through the perfected atmosphere.

• This reveals the Torah’s ancient awareness of the science of atmospheric light transmission — a concept confirmed by modern astronomy and physics over three millennia later.