Daylight
Matters

Daylight matters, and perhaps more than you think. Natural and self-evident, the light that comes from the sun is often taken for granted. Yet on its journey to us, it has an impact on pretty much everything it encounters. From the infinitely large to the infinitely small, daylight does much more than letting us see and keeping us warm. Scroll down the page to follow the journey of daylight and learn about its effects at different stages of the trip.

Sun

Daylight originates in the Sun’s interior, where nuclear fusion combines four hydrogen nuclei to form one helium nucleus and two protons. The released energy moves through the Sun taking tens of thousands of years before eventually leaving the outer surface of the Sun as solar radiation. The Sun’s rays make a journey of more than 150 million kilometres before reaching the Earth’s surface. Detection of the Sun’s energy is essential for almost all life on Earth.

Experts

Atmosphere

The Sun is the primary energy source that drives the Earth’s climate system. While some of the radiation emitted from the Sun is reflected back into space, a large portion is absorbed by the Earth’s atmosphere and surface. Our atmosphere protects us from harmful cosmic rays during solar storms. Part of the longwave radiation re-emitted from the Earth is absorbed by radiatively active gases in the atmosphere – a phenomenon called the “greenhouse effect”.

Sky

The sky plays a critical role in sustaining life on Earth, providing a medium for the transfer of heat and energy. The availability of daylight in the sky is affected by various factors such as latitude, altitude, time of day, time of year, atmospheric conditions (e.g. air pollution) and weather conditions. In our imagination and everyday perception, the sky is the “home” of the sun, and its changing colours play a large part in shaping our aesthetic and emotional experience of daylight.

Forests

Daylight is a key factor in regulating the growth and health of trees and plants. The amount and quality of light that penetrates the forest canopy influences photosynthesis, which is essential to produce food for the ecosystem and for the regulation of the chemical composition of the atmosphere. Additionally, daylight in a forest steers the daily and seasonal rhythms of plants, animals, whole communities of species and, through this, ecosystem processes as well.

Plants

Daylight is vital for plants as it plays a significant role in their growth, development, and survival. Daylight is both a source of energy and information. Through the process of photosynthesis, plants convert solar into chemical energy, which is essential for their metabolic functions. The variations of the photoperiod and the direction of light inform plants on how to control growth and organ shape, and when to reproduce.

Water

The visible and ultraviolet (UV) components of daylight influence the physical, chemical, and biological processes that occur in the oceans, lakes and rivers systems of the Earth. The presence of daylight affects the temperature and dissolved oxygen levels in water. These, in turn, influence the distribution and behaviour of aquatic organisms. Daylight also drives photosynthesis in algae, which form the basis of most aquatic food chains.

Animals

The presence and intensity of daylight across the day and seasons has a marked impact upon a range of biological processes, including circadian rhythms, hormone production, and metabolic activity. Daylight also helps to provide the visual cues that animals use to navigate, locate food, and avoid predators. In many species, the seasonal changes in daylength are used to time courtship, reproduction and migratory behaviours.

Microbes

Daylight can influence microbial activity by altering cellular processes and gene expression. Some microorganisms require daylight for photosynthesis, which provides the energy they need to produce organic matter and oxygen. Both the visible and non-visible parts of the spectrum are capable of inactivating many of the bacterial and viral pathogens that pose a threat to public health. And daylight can inactivate them through ordinary window glass.

Cells

Daylight can influence the expression of genes, protein synthesis, and other cellular processes. The presence of daylight can stimulate photosynthesis in plant cells and UVB light is needed for the production of vitamin D in animal and human skin cells. The light/dark cycle also plays a critical role in regulating the circadian rhythms of cells, optimising metabolic activity to the varied demands of the 24-hour day.

Humans

Humans are day active and have evolved a visual system that works well under bright natural light. Apart from the visual aspects, the day-night cycle plays a critical role in regulating our circadian system, sleep patterns, hormone production, and other physiological processes. Exposure to daylight enhances cognitive function, productivity and mood, and has been linked to lower rates of mental health conditions. The UV radiation in sunlight is the body’s main source of vitamin D.

Society

Daylight’s impact on society is modulated by factors like geography and climate. Daylight is essential for safety, as it provides us with visual cues. It also affects social and economic activities, such as agriculture and tourism. Daylight shapes culture in that it may facilitate outdoor activities, sometimes enhancing cohesion in communities. The use of artificial light has driven the 24/7 society. Yet, working against the natural light/dark cycle is associated with multiple serious health conditions.

Technology

Daylight influences the performance and efficiency of various devices and systems. Some are specifically designed to exploit it, such as solar collectors. Others are not arranged to take account of it but are influenced by it. Daylight is essential for optical devices, such as cameras and telescopes, which rely on the quality and intensity of natural light for imaging and observation.

Buildings

The use of daylight in buildings enhances the aesthetic and dynamics of space, providing a connection to the outside and promoting the health and well-being of occupants. Daylight design also helps reduce the need for artificial lighting and affects the energy performance of buildings. A well-designed building integrating daylight strategies creates comfortable, inviting and uplifting spaces while also promoting the sustainability of the building.

Cities

Daylight affects various aspects of urban life, including safety, and social as well as economic activities. Cities around the world continue to grow and become ever denser, making access to natural light increasingly difficult for people and nature. This can have real consequences for the health and well-being of city dwellers. The presence of natural light can also enhance social interactions and community engagement, contributing to a vibrant and connected urban environment.