​​Why is the sky blue but sunsets orange or red?​

Have you ever looked up at the sky and wondered why it’s blue during the day, but glows orange or red during a sunset? It’s one of those everyday wonders we often take for granted. The answer lies in how sunlight interacts with Earth’s atmosphere. As this light travels through the air, it gets scattered by tiny particles and molecules. But not all colours scatter equally; some are scattered more, and others pass through depending on the time of day and the angle of the sun.
Here are a few reasons why this beautiful yet thoughtful phenomenon takes place

The light from the sun may look white to our eyes, but it’s actually a combination of many different colours, and each of these colours has it’s own wavelength. These include red, orange, yellow, green, blue, indigo, and violet, just like in a rainbow. When sunlight enters Earth’s atmosphere, it moves across gas molecules, dust, and water vapour, which start to scatter the different colours in all directions.

Not all colors in sunlight are treated the same by the atmosphere. Blue light has a shorter wavelength, due to which it’s scattered more easily by the tiny molecules in the air. This scattering, known as Rayleigh scattering, is why we see a blue sky during the day. The blue light bounces around and fills the sky from every direction, while the other colours pass through more directly.

When the sun is high overhead, sunlight travels a shorter distance through the atmosphere, so we mainly see the scattered blue light. But during sunrise or sunset, the sun is low on the horizon, and its light has to travel a much longer path through the atmosphere. As a result, most of the shorter-wavelength blue and violet light gets scattered away before it reaches our eyes.

Since blue and violet light are scattered out over longer distances, the colours left behind, which are reds, oranges, and pinks, are the ones that reach us when the sun is near the horizon. These longer wavelengths don’t scatter as easily, so they pass through more of the atmosphere. That’s why sunsets often look rich and fiery in colour, even though the sun itself hasn’t changed.

Things like air pollution, dust, smoke, or even volcanic ash can enhance the scattering effects during a sunset. These larger particles scatter light differently, often making sunsets appear even redder or more vibrant. Clean air usually creates softer pastel sunsets, while hazier air leads to deeper reds and purples. So, while physics explains the basics, nature adds its own artistry to the sky’s palette.