The sun appears red today because of how sunlight interacts with our atmosphere, especially when the sun is low on the horizon.
Understanding Why the Sun Appears Red
When the sun is low in the sky, such as at sunrise or sunset, sunlight travels a longer path through the Earth's atmosphere. This longer journey causes a phenomenon known as scattering.
How Atmospheric Scattering Works
- Shorter Wavelengths: Sunlight is made up of different colors, each with a specific wavelength. Blue and violet light have shorter wavelengths.
- Scattering Effect: When sunlight enters the atmosphere, these shorter wavelengths (blue and violet) are scattered away by air molecules and other particles.
- Longer Wavelengths: This scattering leaves the longer wavelengths, such as red and orange light, to pass through more directly to our eyes.
As described in the reference, "When the Sun is low in the sky, sunlight has to travel farther through the atmosphere, the blue light is scattered away, and the sky and Sun appear red." This process explains why we see a reddish hue when the sun is at a low angle.
Factors Influencing the Redness of the Sun:
- Angle: The lower the sun is in the sky, the more atmosphere the light has to travel through, making the red effect more pronounced.
- Particles: The presence of more particles, such as dust or pollution, in the air can intensify the scattering effect and result in a deeper red color.
Summary
The primary reason the sun looks red is due to the increased scattering of shorter wavelengths of light (blue) by the atmosphere as the sunlight passes through at a low angle. This leaves the longer wavelengths (red) to reach our eyes, thus making the sun appear reddish.
