The light we see from the sun is just a fraction of the energy it sends our way. Beyond the violet end of the rainbow lies ultraviolet (UV) radiation, a type of electromagnetic energy with wavelengths too short for the human eye to detect. While we can't see it, it has a significant effect on our planet and our bodies.

Scientists classify UV radiation into three main types based on its wavelength: UVA, UVB, and UVC.

Not all UV radiation from the sun reaches the Earth's surface. Our atmosphere, particularly the ozone layer, acts as a protective shield. This layer of gas high up in the stratosphere is very effective at absorbing UV light.

UVC, the most harmful type, is completely absorbed by the ozone layer and oxygen in the atmosphere. Luckily for us, none of it reaches the ground. Most UVB radiation is also absorbed, but a small amount makes it through. UVA radiation, however, passes through the atmosphere almost entirely unfiltered. This means that when you're outside, you are mainly exposed to UVA with a smaller dose of UVB.

When UV radiation hits our skin, it causes changes in the skin cells. UVB is the main culprit behind sunburn. Its energy is absorbed by the top layers of the skin, causing redness, inflammation, and pain.

UVA rays penetrate more deeply. They don't typically cause sunburn, but they are responsible for skin aging, like wrinkles and leatheriness, because they damage collagen and elastin fibers. More importantly, both UVA and UVB rays can damage the DNA within our skin cells. This damage can disrupt normal cell function and is the starting point for developing skin cancer later in life.

The body has ways of dealing with this damage, but repeated exposure can overwhelm these repair systems. The effects of UV damage are cumulative, meaning they build up over your lifetime.

Our bodies have a built-in defense against UV radiation: melanin. This is the pigment that gives skin, hair, and eyes their color. When your skin is exposed to UV light, it produces more melanin in an attempt to protect itself. The result is a tan.

Melanin is excellent at absorbing UV radiation and dissipating it as harmless heat, preventing the energy from reaching and damaging the DNA in your skin cells. People with naturally darker skin have more melanin and are therefore better protected from UV damage. However, no amount of melanin provides complete protection. Everyone, regardless of skin tone, is susceptible to UV-induced skin damage.

Understanding these basics helps explain why sun protection is so important for long-term health.

Ready to check your understanding?

Now you know how the sun's invisible rays interact with our atmosphere and our skin. This knowledge is the first step in staying safe in the sun.