The Earth has undergone seven color transformations throughout its long history. Did you know that? While many people envision the Earth as an azure planet, the truth reveals a lengthy process of color changes, including red, black, white, purple, green, azure, and now a gray-blue hue.

Approximately 4.6 billion years ago, the Earth came into existence through a cataclysmic collision and fusion event. During this tumultuous period, the entire surface was almost entirely covered in lava, giving the newborn Earth a dark red color, symbolizing endless possibilities.

In the years that followed, the surface magma gradually cooled and solidified, forming early basaltic landmasses, rendering the Earth black during this era. Four billion years ago, due to processes like steam cooling and impacts from foreign comets, a significant amount of water accumulated on Earth, with over 90% of the surface now submerged. Earth resembled a colossal "water balloon," and shortly after, it transformed into a green planet. This transition was primarily attributed to the high iron content in the water.

At that time, oxygen levels on Earth were minuscule, causing most of the iron elements to react with hydroxide, sulfur, chlorine, and other elements, forming a substance known as "oxygen-free rust." This substance tinted the pristine oceans green, giving rise to Earth's identity as a "green planet."

Several years ago, the "Purple Earth" hypothesis emerged, suggesting that early life on Earth didn't rely on chlorophyll but rather on retinaldehyde. In other words, ancient microorganisms absorbed sunlight and converted it into energy using retinaldehyde, a molecule found in photosynthetic microorganisms like the bacterium Bacillus salinarius.

These microbes absorbed violet light and reflected red and blue-violet light, creating a majestic purple appearance across the entire planet.

While conclusive evidence for the "Purple Earth" hypothesis remains elusive, recent research recognizes the purple planet as a prime candidate for the existence of life. Additionally, Earth experienced a period of whiteness approximately 2.4 billion years ago.

During the Huron Ice Age, Earth entered the most severe and prolonged ice age in geological history, enveloping the entire planet in ice and transforming it into a snow-white sphere that endured for 300 million years.

The primary factors behind this white period are attributed to the Earth's volcanoes remaining dormant for 250 million years, plunging the world into an ice age. Alternatively, cyanobacterial blooms are believed to have led to a rapid reduction in greenhouse gases such as carbon dioxide, dramatically cooling the Earth.

The azure color that the Earth displays today is predominantly due to its abundant seawater. Covering 71% of the planet, seawater absorbs longer wavelengths of sunlight, including red, orange, and yellow light.

It reflects shorter wavelengths of violet light, allowing blue light to scatter and refract fully within the seawater. The presence of salt ions in seawater further enhances the scattering effect, resulting in the beautiful azure color that defines our planet as a blue one.

Satellite imagery has revealed that Earth has transitioned from azure blue to a somewhat grayish-blue hue, reflecting pollution and excessive environmental degradation caused by human activities.

Before humanity's presence, no form of life had inflicted such extensive harm upon the Earth. If we fail to prioritize environmental protection, our planet may continue to change its color, and Earth might no longer be a hospitable home for humanity.