Today, we’ll explore a question that has intrigued all of us at some point during childhood: “Why does the ocean appear blue?” Many of us have been told the answer that the ocean reflects the color of the sky. But is that really true? Let’s dive into the history first and then explore the scientific explanation. Let’s begin!

Historical Perspective

In ancient times, Homer, the famed Greek poet and author of The Iliad and The Odyssey, described the ocean as “wine-dark” in his works. He used this term to describe the sea no less than seventeen times. But why? After all, we now know the ocean is blue, don’t we? So what prompted Homer to describe it this way?

Homer’s reasoning behind the term “wine-dark” can be understood in the context of how colors were perceived in his time. For instance, when we think of the color of a leaf, specific shades like deep green, light green, or pale yellow come to mind. Similarly, when thinking about skin or hair color, we associate them with distinct hues. Homer’s description was influenced by this kind of perception. He likely drew a parallel between the fluidity of wine and the appearance of the ocean.

But how “dark”? In his poetry, Homer used the word oînops, which combines oînos (meaning wine) and óps (meaning face). This translates to “wine-faced” or “wine-like.” In some places, Homer referred to wine as melás, meaning dark. However, he never explicitly described the ocean as “wine-dark.” He mentioned the ocean in different contexts and compared it to wine, but the idea that he directly called the ocean “wine-dark” is a result of misinterpretation and exaggerated imagination by some people.

The Beginning of Scientific Explanations

In the 18th century, scientists began investigating the colour of the ocean. Michel Eugène Chevreul , a French chemist, proposed in 1831 that the blue color of the ocean is due to the absorption of light. This marked the first scientific attempt to explain the ocean’s colour.

Later, an Indian physicist, Sir Chandrasekhara Venkata Raman (C.V. Raman), who was born in Tiruchirappalli, offered the first thorough explanation of why the ocean appears blue. During his first trip to London in 1921, he was struck by the vivid blue waters of the Mediterranean Sea. This inspired him to investigate the phenomenon, leading to a groundbreaking discovery that changed our understanding of light and color in nature.

Scientific Explanation:

The primary reason the ocean appears blue is that seawater absorbs sunlight. Sunlight is a mixture of different colors, each with varying wavelengths. When sunlight hits the water, the water absorbs colors like red, orange, yellow, and green more effectively, while blue light is absorbed less. This remaining blue light is reflected from the surface, making the ocean appear blue to our eyes.

In deep oceans, blue light can penetrate up to about 200 meters before being absorbed, which is why deep waters often appear dark or even black. On the other hand, small quantities of water, like a glass of water, appear colorless because the amount of water is insufficient to absorb significant light.

In summary: “The blue color of the ocean is due to the reflection and greater penetration of blue wavelengths compared to other colors.”

Depth and Color Impact:

The depth of the water plays a significant role in its color. In shallow waters with algae or seagrass, the ocean may appear greenish. However, in deeper waters, the blue color becomes more prominent due to the lack of other reflective elements and the absorption dynamics.

Effect of Sun Angle on Ocean Color

The angle of the sun significantly influences the perceived color of the ocean. On sunny days, when sunlight directly hits the water, the ocean appears deep and vibrant blue. On cloudy days, with less light penetration, the water may appear grayish or greenish.

Impact of Marine Life and Particles

The presence of phytoplankton can give the ocean a greenish hue. These are microscopic algae containing chlorophyll, which thrive through sunlight. They form a crucial part of the food chain for small aquatic organisms like diatoms, flagellates, and green algae, influencing the water’s color through their abundance and light absorption properties.

Now, Let’s Learn About the Groundbreaking Discovery of “Raman Effect” by the Great Physicist Sir C. V. Raman

In 1930, Sir C. V. Raman was awarded the Nobel Prize for his revolutionary discovery, the Raman Effect. The inspiration for this discovery came in 1921 during his journey back to India from London over the Mediterranean Sea. The striking blue color of the sea intrigued him—why was the ocean blue? This question became the focal point of his research. Raman decided to dedicate his experiments to uncovering the reasons behind this phenomenon.

Before diving into the Raman Effect, let’s revisit a key concept: VIBGYOR, the spectrum of colors—Violet, Indigo, Blue, Green, Yellow, Orange, and Red. These colors are part of sunlight, and when sunlight passes through a glass prism, the spectrum becomes visible as distinct bands of these seven colors.

Before Raman’s discovery, the prevailing theory (let’s call it T1) was that when sunlight passed through molecules, the wavelength of the scattered light remained the same as the original light.

But after the discovery of the Raman Effect, this theory was completely overturned. Raman found that when sunlight passes through molecules, the molecules either transfer their energy to the light ray or absorb energy from it. As a result, the wavelength of the scattered light differs from the original wavelength. This phenomenon is known as inelastic scattering, which we will call T2.

Which Theory Is Correct?

If T1 were correct, the color of water would always appear blue, irrespective of depth or container. For example, water in a glass or a shallow river would appear the same blue as the ocean. However, that is not the case. This discrepancy proves that T2, or the Raman Effect, is correct.

It was this groundbreaking research that earned Raman the Nobel Prize in 1930. The discovery is now considered one of the greatest scientific achievements of the 20th century.

That’s all for today! On behalf of Sci-fi Note, we wish you all the best. Stay healthy, stay happy, care for the environment, and always nurture your love for science. Thank you!