Lighting

Light helps us see.

People use light for many things. It can help us work. It can also make things look pretty.

Long ago, people used campfires to see. They also used oil lamps. Some people even used fireflies! Today, we use many kinds of lamps. We can use the sun through windows. This saves energy.

Light can be bright or soft. It helps us stay safe at night.

Lighting is the use of light to help us see or to make things look pretty.

We can use natural light from the sun through windows. This is called daylighting. It helps save energy in buildings.

Long ago, people used campfires and torches. They also used oil lamps made from rocks or shells. These lamps used animal or plant fats for fuel. Later, people used whale oil for light. In the 1840s, a man named Abraham Gesner made kerosene. Kerosene was cheaper and brighter than whale oil.

Eventually, electric lighting became very common. It changed how people lived at night.

There are different ways to use light indoors. Task lighting is bright light for a specific job, like reading.

Accent lighting is used to highlight pretty things, like a plant. General lighting fills a whole room with light. Some lights shine down from the ceiling. This is called downlighting. Other lights shine up to make a soft glow. This is called uplighting.

Outdoors, we use street lights and big floodlights to keep areas safe.

Lighting is the way we use light for practical tasks or to make things look beautiful.

We can use artificial sources like lamps or natural light from the sun. Using windows and skylights to bring in sunlight is called daylighting. This is a smart way to save energy in buildings. Good lighting can help people do their work better. It can also make a room look better or change how people feel.

There are different ways to direct light in a room. Task lighting is bright and focused for a specific job like reading.

Accent lighting is used to highlight pretty things like plants or art. General lighting, also called ambient light, fills up the whole space. Most lights in homes use downlighting, which shines from the ceiling downward. Some people use uplighting to bounce light off the ceiling for a soft glow.

Backlighting can be used to add depth to a scene by shining light behind an object.

Humans have used light in many ways throughout history. Long ago, people used campfires and torches to see in the dark. As far back as 400,000 years ago, Peking Man used fire in caves. Early people made oil lamps from shells, stones, or horns. They filled these with grease from plants or animals. About 15,000 years ago, people in the Lascaux caves in France used stone lamps.

People even used fireflies as a source of light.

Finding cheaper ways to make light changed the world. For a long time, people used whale oil for lamps. However, the price of whale oil went up a lot in the 1850s. In the 1840s, a Canadian geologist named Abraham Gesner refined kerosene. Kerosene was much cheaper and provided a brighter light. By 1860, Americans spent more on kerosene than on whale oil.

Later, electric lighting arrived in the 1880s with arc lights and bulbs. This made many nighttime activities possible and helped keep streets safer.

Today, we use many different tools to manage light. Light fixtures can be simple or they can be works of art. Some fixtures use LEDs, which are much more efficient than older bulbs.

We also use light to guide us outdoors. Street lights help people drive and walk safely at night. Large floodlights can light up big sports fields. A study in Germany in 2021 found that most public light comes from private windows. Other light comes from street lamps, shops, and signs.

Lighting is the deliberate use of light to achieve practical or aesthetic effects. It involves both artificial sources, like lamps, and natural illumination, such as daylight. In many buildings, daylighting is used as a primary light source. This is done by using windows, skylights, or light shelves to capture sunlight. Daylighting is a vital method for saving energy in modern architecture. Artificial lighting remains a major component of total energy consumption in buildings. Proper lighting can improve how people perform tasks or how an area looks. It can even have positive psychological effects on the people inside a space.

History shows how humans have mastered light over thousands of years. The discovery of fire provided the first artificial light through campfires and torches. As early as 400,000 years ago, Peking Man kindled fire in caves. Prehistoric people later created primitive oil lamps from rocks, shells, or horns. These lamps used animal or vegetable fats as fuel with a fiber wick. Researchers found hundreds of these stone lamps in France's Lascaux caves. These artifacts date back approximately 15,000 years.

Technological shifts greatly changed the cost and availability of light. For a long time, whale oil was a common fuel for lamps. However, whale oil prices more than doubled between 1848 and 1856. This shortage helped lead to the rise of kerosene. In the 1840s, a Canadian geologist named Abraham Gesner refined kerosene. This provided a much brighter light at a lower cost. By 1860, Americans spent more on kerosene than on whale oil. The discovery of crude oil in 1859 eventually ended the whale oil era.

Modern lighting is categorized by its intended use and distribution. Task lighting is highly concentrated for specific activities like reading or surgery. For example, reading poor reproductions may require 1500 lux of light. Accent lighting is decorative and highlights objects like plants or art. General lighting, or ambient light, fills an entire area for basic visibility. Outdoors, general lighting for parking lots may be as low as 10-20 lux. This is because pedestrians and motorists are already accustomed to the dark.

Light fixtures serve as holders and direct light to avoid glare. A key measurement for these fixtures is luminous efficacy. This is the amount of usable light produced per unit of energy. It is often measured in lumens per watt. The transparency of a fixture affects this efficiency. Shading a light may decrease efficacy but increases visual comfort. Color temperature also plays a major role in how light looks. An incandescent bulb has a temperature of 2800 to 3000 kelvins. In contrast, daylight is much higher at around 6400 kelvins.

Different methods exist to move light through a space. Downlighting is the most common method used in homes and offices. It uses fixtures in the ceiling to cast light downward. While easy to design, it can cause glare and use much energy. LED lighting has improved this efficiency by approximately 90% compared to halogen. Uplighting is a different method that bounces light off a ceiling. This creates a uniform, shadow-free effect and minimizes glare on screens. However, this method is considered somewhat uneconomical because it relies on surface reflectance.

Indoor lighting includes many specific styles like recessed or track lighting. Recessed lights, also called pot lights, sit flush within the ceiling. Track lighting was invented by Lightolier and allows fixtures to be aimed easily. Sconces are fixtures mounted on walls that shine light up or down. For outdoor environments, lighting serves functional, advertising, and decorative roles. A 2021 study in Germany looked at light in public areas. It found that 48% of light came from private windows. Street lights and commercial shop windows made up the remaining portions.