What is light?

Light is the essence of life. Without the sun's light, we would have no plants, no food, and therefore no existence. Everything on our planet depends on the sun rising every day and producing its energy-filled rays. In addition to being a fundamental part of our existence, light also plays a crucial role in our perception of the world. But have you ever wondered what light truly is?

In short, light is a component of electromagnetic radiation that is visible to us humans. It can be described as tiny units of energy known as photons, which originate from a source of energy such as the sun. As light is a form of electromagnetic radiation, it propagates as waves, with the size of the waves determining the colour that we perceive the light as. The visible spectrum of light ranges from shorter wavelengths like violet and blue light to longer wavelengths like orange and red light. Similar to how radio is designed to receive a range of FM signals and play different radio channels, our eyes are developed to receive light waves and decode their colours. You may also be familiar with other forms of electromagnetic radiation such as radio waves, X-rays, and infrared light – these wavelengths are simply not visible to the human eye.

If we delve deep into the realm of quantum physics, we find that light is produced when electrons in atoms and molecules release energy. When electrons gain energy, they jump to higher energy levels, and when they release energy, they fall back to their original state. This energy conversion occurs through the emission of photons, which are small particles of light energy.

Why is light so important?

The significance of light for humans extends far beyond what we can perceive with the naked eye. It impacts our world, and our biology, and influences our circadian rhythm, which directly affects our immune system, digestion, sleep, brain capacity, and mental well-being. Light, or more precisely, the daily rhythm of light and darkness, is, therefore, crucial for our health and overall well-being.

• Sight and vision: The most obvious significance of light is that it enables us humans to perceive the world around us. When light is emitted from energy sources, it enters our eyes and interacts with light-sensitive cells in the retina, also known as photoreceptors. These photoreceptors, divided into rods and cones, convert light energy into electrical signals that are then sent to our brain, where they are processed and enable us to interpret the images we see through colours and shapes.
• Circadian Rhythm: Light plays a crucial role in regulating our biological rhythms, including our sleep-wake cycle. We all possess an internal biological clock known as the circadian rhythm, which helps regulate all the physiological processes in our body every single day. When exposed to natural light during the day and darkness at night, this internal clock synchronizes, ensuring that we are awake and functioning optimally during the day and asleep at night, which is vital for both our mental and physical well-being.
• Vitamin D: Sunlight contains ultraviolet radiation, which is crucial for our production of vitamin D. This essential vitamin helps our body absorb calcium, maintain healthy bones and teeth, secure the immune system, and regulate cell renewal.
• Mood and well-being: Light has a significant impact on our mood and overall well-being. Sunlight, in particular, stimulates the production of serotonin, a neurotransmitter associated with happiness and a positive mindset. Reduced exposure to natural light, such as during the winter months or in areas with limited sunlight, can lead to conditions with depressive symptoms and even depression, as it is the lack of light that is the cause of seasonal affective disorder. Mood and well-being are closely tied to our circadian rhythm as well, as light during the day and darkness at night help keep our biological system healthy and synchronized.
• Photosynthesis: You probably already know this, but light is also crucial for photosynthesis, which is the process in which plants use the energy from sunlight to grow and produce oxygen. Plants absorb light energy, which is used to convert carbon dioxide and water into glucose (sugar), and as a byproduct, plants also release oxygen. This process forms the foundation of the food chain, as it provides oxygen and nourishment to humans, animals, and other living organisms.

In summary, our entire lives depend on light. First and foremost, it is crucial for sustaining our planet and everything that exists on it. Light is also essential for our vision and our perception of the world around us. It helps regulate our biological rhythms, including our sleep-wake cycle and has a direct impact on our health, mood, and overall well-being. Additionally, light facilitates our production of vitamin D and is the core of photosynthesis, which is vital for our Earth. In other words, light is a natural source of energy and one of the core elements of the universe. Its influence extends far beyond illumination and affects our fundamental health and the entire ecosystem in which we live.