Researchers at the Fox Chase Cancer Center in Philadelphia examined the tanning habits of 400 college students aged 18 to 24, using the same framework that defines substance addictions. They found that 27 per cent showed signs of “tanorexia,” based on answers to questions like “Do you think you need to spend more and more time in the sun to maintain your perfect tan?” and “Does this (your belief that tanning can cause skin cancer) keep you from spending time in the sun or going to tanning beds?”

“I don’t know that the public at large really thinks that tanning could be addictive and if they thought that, then people might be less likely to tan and especially concerned about young people,” said Carolyn Heckman, author of the study and an associate member of the cancer centre.

Current smokers are more likely to be addicted to tanning than those who have never smoked, she found, and obese people are less likely to be tan-dependent than those of normal or below-average weight. The mean age at which participants said they first visited a tanning bed was just over 17 years old, and the mean number of visits over their lifetime was about 57, which means half went more frequently and half less.

“People value attractiveness and they’re willing to take health risks to be attractive, especially since the health risks may not show up for 20 or 30 years,” Heckman said. “They want to look good now.”

Almost half of young Canadian women aged 16 to 24 (49 per cent) and over a quarter of young men the same age (28 per cent) say they actively try to get a tan from the sun, according to a survey released by the Canadian Cancer Society in July. The agency is promoting the World Heath Organization’s stance that tanning beds should be banned for people under age 18, says Heather Chappell, senior manager of cancer control.

“The younger age group we know is the most difficult to reach,” she said. “We need to continue to try to ‘de-normalize’ a tan and (the idea) that a tan is healthy. It’s not necessarily a healthy thing because a tan indicates you have been out exposing yourself to UV.”

But tanning addiction may literally run more than skin deep, Heckman says. Researchers hypothesize that tanning may release endorphins in the brain, she says, potentially bringing on a feeling of well-being similar to the “runner’s high” people get after exercising.

“Tanning may feel relaxing or people might have seasonal affective disorder in the winter and they like to indoor tan to help their mood,” she said. “So those are possibilities of why people might want to tan besides appearance.”

LONDON – International cancer experts have moved tanning beds and other sources of ultraviolet radiation into the top cancer risk category, deeming them as deadly as arsenic and mustard gas.

For years, scientists have described tanning beds and ultraviolet radiation as “probable carcinogens.”

A new analysis of about 20 studies concludes the risk of skin cancer jumps by 75 percent when people start using tanning beds before age 30. Experts also found that all types of ultraviolet radiation caused worrying mutations in mice, proof the radiation is carcinogenic. Previously, only one type of ultraviolet radiation was thought to be lethal.

All of our hats are chosen with sun protection in mind, but not all hats are created equal.

Let’s start with 5 basic questions to narrow down your search:

1. What activity will you be doing? Will there be wind? Do you need good peripheral vision? Will it be hot?
2. Do you want maximum sun protection or is good sun protection just fine?
3. How wide of a brim is comfortable for you?
4. How important is fashion to you or is functionality all you need?
5. Is your hair short? Thinning? Bald or shaved? Do you dye your hair?

1.What activity do you plan to do? Is it gardening, sailing, hiking, travel or a round of golf? Whatever the activity, it creates conditions we need to be concerned about.

Will you be in the wind? With a wide brim hat, a chin strap is very important for keeping your sun hat in place. Remember the old sitcom The Flying Nun? A wide brim hat will pick up the wind like it has wings of its own. Additionally, a chin strap will help keep your hat in place when bending over or dropping your chin is part of your activity, like in gardening.

Peripheral vision is an important factor for both safety and playing various sports like tennis or volleyball. This will be a personal decision for you. Consider both the size of the brim and, if a neck drape is involved, how far does the drape wrap around the face. I am a beach volleyball player and for me a 3″ brim is the widest I can use and still see high flying balls as well as the other players.

Will you be doing an activity that generates body heat? You may want to wear a sun visor for total head aeration or choose a sun hat with mesh on the side of the crown or a hat that made of a fast drying fabric that allows evaporative cooling. One trick for cooling your head in a hot, dry climate is to wet the hat and then let the evaporation cool your head.

Maximum sun protection vs good sun protection?

What is a maximum sun protection hat? We feel a maximum protection hat has a UPF rating of 50 and a hat brim that is 4 inches wide or greater. But there’s more. The brim needs to be angled downward. This downward sloping brim allows you to be protected for more hours of the day.

How does this work? At high noon, when the sun’s rays are directly overhead, even a 3″ brim hat may provide maximum sun protection for your head. But when the sun is either ascending or descending the sun’s rays can sneak right under your hat and strike your face or neck. At daybreak or sunset, when the suns ray’s are virtually horizontal, a wide brim hat may provide no protection at all.

Adventure sun hatIf you plan to be spending time outdoors when the sun is close to either horizon, you may want to think about our more unique designs such as the Kalahari hat, Adventure Hat or Chic Sheik that drop a vertical protective block of fabric between you and the sun.

Good sun protection can be had with a brim less than 4 inches wide or a brim that is more horizon from the head.

How wide of a brim are you comfortable with?

We all have different feelings about this one. Some people can handle a wide brim with no problem while others find it very distracting. Bottom line is that the wider the brim of the hat the more surface area there is to block the sun. But, of almost equal importance, is the angle of the brim. A wide brim hat that comes straight out from the head is good but when the sun is not straight overhead the rays can come under the brim and strike the face and neck. A brim that is angled downward goes a long way in giving you more hours of protection. As a basic rule of thumb, for maximum sun protection choose a downward angled 4″ brim sun hat … and, if you are comfortable, choosing a brim wider than 4″ is even better. If you are not sure how wide a brim you would like you may want to consider a 3 1/2 brim.

Now, how important is fashion to you?

As you can see, some of the sun protection inventors have come up with novel hat designs to protect you from the sun but, alas they would not be called high fashion … except possibly on another planet. Most of these unique hats were designed to solve special sun protection needs such as full face protection, additional neck protection or increased ventilation.

Some of our wide brim hats are the height of fashion creating a dramatic flare or ultra feminine silhouette. As we all know, fashion is in the eyes of the beholder so look for a hat that accentuates your attributes.

5. Next, let’s take a look at your hair.

Do you have thinning hair, or are you balding or shave your head? If yes, mesh panels on the crown of the hat may provide extra air flow to keep your head cooler but it will also let UV radiation sneak through and reach your scalp. With maximum sun protection in mind, it is better to leave the mesh panels for those with thick tresses. For those of you who do have thick hair, choosing a hat with mesh panels will help your head stay cooler in the heat.

Do you have short hair? If yes, we need to be extra concerned about your neck. A sun visor or a brim less than 4″ leaves your neck open to sun damage. Typically a full brim hat will be your best choice.

Hair can get dry, cracked and brittle from too much sun. Dyed hair is especially susceptible to problems under UV radiation so, to protect your hair, I would suggest staying away from visor hats that leave your hair open to the sun light.

Just a few parting suggestions for picking the perfect hat for you:

Hat size: A hat that is too big is better than one that is too small. A tight hat may give you a headache and then you won’t want to wear it. Many of our hats are adjustable, but in all cases, please be sure to measure your head to ensure a perfect fit. For those of you with lots of little grey cells we have hats for big heads. And, for those of you with smaller heads, please know that you may request stick-on sizing tape to help you fit your hat.

Cotz sunscreenReflective rays: Even the widest brim hat will not be able to stop rays reflecting up from the ground, a near by car or any other reflective surface so wearing sunscreen is important for maximum sun protection. Rule of thumb: Sun protective fabric is always better than sunscreen in protecting you from the harmful rays of the sun but alas not always practical. On areas where you can’t cover up with fabric use sunscreen. Maximum sun protection is achieved by a combination of sun protective clothing and sunscreen.

“Lutein has been widely recognized for its eye health benefits for several years. But, our data is the first of its kind to suggest that lutein may have the potential to act as a preventative agent against UVB-induced skin cancer,” said Salvador Gonzalez, M.D., Ph.D., leader of the Harvard research team. “In addition, these data suggest that lutein protects the skin against damage caused by exposure to UVB light, further validating our position that lutein is a critical component to overall skin health.”

Lutein (LOO-teen) is a yellow pigment (the yellow is covered up by chlorophyll in green leaves) found predominantly in vegetables. It is also present in the eyes and skin of the human body. In women, lutein is found in the breasts and cervix. As an antioxidant, lutein protects the eyes from the damaging effects of aging. Lutein also acts as a light filter, protecting against the sun’s harmful rays.

UVA and UVB rays are two types of harmful rays found in sunlight. UVA rays contribute to wrinkling the skin, as well as to the development of skin cancer. UVB rays are the ones that are the primary cause of sunburn and skin cancer.

Good sunscreens block both UVA and UVB rays and are critical to skin health. But, you can do even more to protect your skin and eyes when you’re outside.

Safety tips to keep top of mind:

Wear UV-blocking sunglasses. Over time, exposure to ultraviolet light can cause cataracts and increase your risk of macular degeneration, a disease that causes irreversible blindness.

If you’re a parent, protect your children’s skin. Research indicates that one or more severe, blistering sunburns in childhood or adolescence can double the risk of skin cancer later in life.

Check the expiration date on your sunscreen. Sunscreen without an expiration date has a shelf life of no more than three years.

Eat a healthy diet comprised of green leafy vegetables. Consumption of 6 milligrams of lutein per day (approximately one-third cup of cooked spinach) has been linked to a reduced risk of cataracts and age-related macular degeneration. Vitamins and dietary supplements formulated with purified lutein provide another option for adding this nutrient to a daily diet.

It’s important to note that when lutein is consumed in foods or vitamins, it deposits in various tissues in the body — the eyes, the skin, fat tissue and so on. Therefore, it may also be beneficial to apply lutein directly to the surface of your skin. Several skin care products containing lutein are now available.

The sun gives out ultraviolet (UV) radiation that is made up of three types of rays: UVA, UVB and UVC. UVC rays from the sun can’t get through the ozone layer but UVA and UVB rays can, and these rays have been linked to skin damage.

Short-term skin damage

Sun tan

A tan is actually a sign that your skin has been damaged and is trying to protect itself. UV radiation stimulates your skin to produce more pigment (colour), which protects against damage. Your tan will fade, but the damage to your skin remains.

Sunburn

Short-term overexposure to the sun can cause your skin to burn, usually making it red, hot and painful. You can soothe your burnt skin with calamine lotion or aftersun lotions. If your sunburn is severe, you may need medical treatment.

Heat exhaustion and heat stroke

This is when your body becomes overheated after overexposure to the sun or by getting sunburn. You may have symptoms including vomiting, headaches and fever. If you think you have heat stroke, get to a cool place as soon as possible and drink plenty of water. If your temperature is higher than 39ºC (you can measure your temperature using an oral thermometer), your skin has become dry and flushed or you feel very unwell, you should see a doctor immediately.

Long-term skin damage

Ageing and infection

Ageing of your skin is a result of the UVA rays penetrating it, causing wrinkles and sagging. UV rays can also cause damage to the eyes. It has been suggested that too much sun exposure may damage your immune system, increasing your risk of infection.
Skin cancer

Although the exact cause of skin cancer isn’t known, some things make it more likely. Your risk of skin cancer increases if you’re exposed to UV rays because of spending a lot of time in the sun.

Preventing sun damage

To protect your skin, you should stay out of the sun between 11am and 3pm, when the sun’s UV rays are strongest. Look for shady areas such as under trees, and use umbrellas or canopies.

Watch the UV index

The UV index describes the strength of the sun’s UV radiation. It’s usually shown as a number in a triangle on a weather map. The numbers range from one to 11+ and the higher the number, the stronger the UV radiation. If the UV index is higher than three you will need protection when you go outside.

In many countries, the UV index is reported alongside the weather forecast in newspapers, on TV and on the radio.
You can protect your skin by wearing long-sleeved tops and trousers. Choose materials that have a close weave as these block out the most UV rays. Wet clothing stretches and lets more UV radiation through to your skin.

Wearing a wide-brimmed hat can halve the amount of UV radiation reaching your face.

Sunglasses help to protect your eyes and eyelids. Wraparound sunglasses will also protect the skin around your eyes. You should choose a pair of sunglasses that has the following labels:

* 100 percent UV protection
* UV 400 – this means it protects from both UVA and UVB rays

If you’re buying a pair of sunglasses in Europe, check that they also carry the European Standard CE mark and the British Standard (BE EN 1836:1997).

Wear sunscreen

Always use “broad spectrum” sunscreen. This means that it protects your skin against UVA and UVB rays. Make sure it has a sun protection factor (SPF) of 15 or higher. The SPF tells you how good the sunscreen is at filtering out the UVB rays. There isn’t a measure of protection against UVA rays. Sunscreen can’t give you complete protection since some UV rays will always get through, but you will get more than 90 percent protection from UVB rays with SPF 15.

Re-apply sunscreen every two hours or more often if you go swimming, or sweat a lot. Water reflects the sun’s rays so you need to apply sunscreen before swimming.

Cloud doesn’t stop the sun’s UV rays getting through so you should protect yourself even if it’s cloudy. Haze (from thin clouds or mist) can even increase your UV radiation exposure because the rays are scattered.

Check moles

You should check your moles regularly for changes that may indicate skin cancer. Most changes are harmless, but you should see your GP if you notice:

* growth of an existing mole – especially over 7mm (a quarter of an inch) in diameter
* a mole with an uneven or ragged edge
* a mole of varying shades of colour
* a mole with an inflamed or red edge
* a mole that bleeds, oozes or crusts
* a mole that feels different, painful or itches

Don’t use sunbeds

Sunbeds mimic the effect of the sun and give out artificial UVA and UVB radiation. Exposure to artificial UV radiation can also damage your skin. Sunbeds have been linked to an increased risk of skin cancer as well as eye conditions.

An artificial tan from a sunbed doesn’t protect your skin against sunburn on holiday; it’s similar to using a sunscreen with SPF 2 to 3.

There are no regulations relating to the use of sunbeds, but the World Health Organization (WHO) recommends that you shouldn’t use sunbeds if you:

* are under 18
* have sunburn, burn easily or had frequent sunburn as a child
* have a lot of moles
* tend to freckle
* have pre-cancerous or cancerous skin lesions
* are wearing cosmetic products (these may make you more sensitive to UV radiation)
* are taking medication (you should seek medical advice to check whether your medication will make you particularly sensitive to UV radiation)

Winter sun

You can’t feel UV rays. The warmth you feel on your skin is actually caused by the sun’s infrared radiation. So just because you can’t feel the hot rays of the sun, it doesn’t mean you won’t get sunburnt.

The amount of UV radiation is generally lower during the winter but snow reflects most of the sun’s rays, so you can still get sunburnt. If you’re high up in the mountains, there is less atmosphere to block out the UV rays, so make sure you use sunscreen.
Protecting children from the sun

Young skin is sensitive and very easily damaged by the sun. Getting sunburnt as a child is known to increase the risk of developing skin cancer as an adult.

Keep your baby in complete shade. Pop-up shelters are a good way to protect children from the sun on the beach or in the garden. Canopies and parasols for prams and buggies protect children when you’re out and about.

Dress your child in loose-fitting clothes that cover up their arms and legs. A hat with a brim at the front and a cloth flap that covers the neck provides good sun protection. Sunglasses will help to protect your child’s eyes.

Use water-resistant sunscreen with SPF 20 or higher on all exposed areas of your child’s skin and apply generously every couple of hours. If you take your child swimming, re-apply the sunscreen after towel drying.

Fake tans

Fake tanning lotions are a popular alternative to sunbathing and sun beds. The tanning lotion reacts with your skin and produces a brown pigment. Fake tan needs to be re-applied regularly if you want to maintain the tan, because your outer skin cells are shed naturally as your skin grows.

Some fake tanning lotions contain sun protection but the SPF is usually very low, so you should also wear sunscreen with an SPF of 15 or higher when you’re out in the sun.

Although fake tanning lotions aren’t known to be dangerous, they can sometimes trigger an allergic reaction. Always test the lotion on a small area of your skin first to see if you have a reaction.

MOLES AND FRECKLES

Moles occur where melanocytes clump together. They are usually oval or round pigmented spots, with a smooth border and regular colour. They may be hard or raised and clump together.

Freckles are flat and usually occur on sun exposed areas. Moles and freckles are very common in fair skinned people; 20 – 40 are the average number of moles for an adult. Most appear around puberty, in later life many may disappear.

ON THE BRIGHT SIDE

Exposure to sunlight allows our bodies to produce vitamin D. For most white skinned people, 10-15 minutes exposure of face, forearms and hands to our Northern Ireland sunlight is enough to maintain vitamin D levels. (The closer to the equator fair skinned people go, the shorter the exposure time required). However people with dark or heavily pigmented skins, living in northern latitudes may benefit from more moderate sun exposure to ensure maintenance of adequate vitamin D levels. Prolonged exposure to UV radiation is bad for all skin types.

HOW SKIN PROTECTS ITSELF

The sun’s UV radiation on our skin causes it to try to protect itself by producing melanin. This production of melanin in response to trauma from UV radiation appears as a ‘tan’. The skin also defends itself through thickening of the outer epidermis – keratin layer. Now we can understand the origins of the word ‘tan’ – thickened and darkened skin – leather like. A ’suntan’ indicates sun damage.

ADVERSE EFFECTS OF UV RADIATION ON THE SKIN

Short term: skin exposed to UV radiation can develop freckles and rashes. Short-term excessive exposure to UV radiation causes sunburn – reddening, pain and in severe cases blistering and even second degree burns.
Take care not to burn. Sun increases your risk of skin cancer.

Exessive sun exposure resulting in sunburn – three weeks on. (left)

Long term: over time UV radiation exposure, whether or not associated with sunburn, accelerates skin ageing making it look dry, wrinkled, loose and dull and causing pigment changes commonly known as ‘age spots’. It can also cause changes in the skin cells, which may lead to skin cancer.

Excessive sun exposure is the main cause of most types of skin cancer.

These two photographs are of two 71 year old women. They look very similar, except that one has spent a great deal of her life exposed to the sun, whereas the other has covered up.

SKIN MOST AT RISK

Some skins are more at risk from the effects of UV radiation than others. Check yours out:

MOST RISK

•     Fair skin that never tans – always burns.
•     Fair skin that burns before tanning.
•     Skin that always tans and rarely burns
•     Dark and heavily pigmented skin which would only burn in exceptional circumstances.

LEAST RISK

Those with pale skin, fair or red hair need to take special care.

However, not all physicians agree with the assertion that there is an optimal level of sun exposure, with some arguing that it is better to minimize sun exposure at all times and to obtain vitamin D from other sources.

Serum levels of 25(OH) D3 are below the recommended levels for a large portion of the general adult population and in most minorities, indicating that Vitamin D deficiency is a common problem in the United States.
Contents

Benefits

According to the U.S. National Institutes of Health Office of Dietary Supplements, most people in the United States can meet their vitamin D needs through exposure to sunlight, even though a large portion have serum 25(OH)D3 levels below recommendations. Ultraviolet (UV) B radiation with a wavelength of 290-315 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. Season, geographic latitude, time of day, cloud cover, smog, skin melanin content, and sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis. The UV energy above 42 degrees north latitude (a line approximately between the northern border of California and Boston) is insufficient for cutaneous vitamin D synthesis from November through February; in far northern latitudes, this reduced intensity lasts for up to 6 months. In the United States, latitudes below 34 degrees north (a line between Los Angeles and Columbia, South Carolina) allow for cutaneous production of vitamin D throughout the year.

Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60%. UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. Sunscreens with a sun protection factor of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly. Skin likely synthesizes some vitamin D even when it is protected by sunscreen as typically applied.

The factors that affect UV radiation exposure and research to date on the amount of sun exposure needed to maintain adequate vitamin D levels make it difficult to provide general guidelines. It has been suggested by some vitamin D researchers, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2%-6% UVB radiation is also effective. Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement.

Risks

Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight and UV radiation from tanning beds. According to the National Toxicology Program Report on Carcinogens from the Department of Health and Human Services, broad-spectrum UV radiation is a carcinogen thought to contribute to most of the estimated 1.5 million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States Lifetime cumulative UV damage to skin is also largely responsible for some age-associated dryness and other cosmetic changes.

It is not known whether a desirable level of regular sun exposure exists that imposes no (or minimal) risk of skin cancer over time. The American Academy of Dermatology advises that photoprotective measures be taken, including the use of sunscreen, whenever one is exposed to the sun.

Is there a safe level of sun exposure?

According to a recent study submitted by the University of Ottawa to the Department of Health and Human Services in Washington, D.C., there is not enough information to determine a safe level of sun exposure at this time.

There is no consensus on which component of Ultraviolet Radiation (UVA or UVB or UVC) actually is carcinogenic, and the composition of Ultraviolet Radiation changes throughout the day: At high noon, Ultraviolet Radiation reaching ground level is 95% UVA and 5% UVB, while before 10am and after 2pm this percentage changes over time to 99% UVA and 1% UVB. This is caused by the the reflection of UVB rays back into space due to sun angle as the earth slowly rotates on its axis. The rate of change is faster the farther the position moves away from the equator (ie more north or south) 99% UVA / 1% UVB sunlight is known as “bronzing” rays, as it provides the deepest colour tanning.

On average over a day, 98.7% of the ultraviolet radiation that reaches the Earth’s surface is UVA. UVC is almost completely absorbed by the ozone layer and does not penetrate the atmosphere in any appreciable quantities. As a result, only the combination (UVA, UVB, and UVC) known as “Ultraviolet Radiation” is listed as a carcinogen, the components are only “likely to become” known carcinogens. Solar radiation, also known as “sunlight” is also listed as a carcinogen because it contains Ultraviolet Radiation. This means also that the UV Index is a measure of total Ultraviolet Radiation, and not just Vitamin D-producing UVB.

Sunlight is therefore the only listed carcinogen that is known to have health benefits, in the form of helping the human body to make Vitamin D. This makes sunlight unique on the list of known carcinogens.

Homo sapiens evolved near the equator, and human skin color is a visible indication of direct sun exposure due to the pigmentation level. With new evidence of Vitamin D receptors in all body tissues, experts advise having a balance between Vitamin D from sun exposure and Vitamin D from supplements. The only way to quantify adequate levels of Vitamin D is with a serum 25(OH) D3 test.

In colder countries, many people prefer sunnier days and often avoid the shade. In hotter countries the converse is true; during the midday hours many people prefer to stay inside to remain cool. If they do go outside, they seek shade which may be provided by trees, parasols, and so on.

Sunshine is often blocked from entering buildings through the use of walls, window blinds, awnings, shutters or curtains.

Sunbathing

Sunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. People often sunbathe in comfortable places where there is ample sunlight. Some common places for sunbathing include beaches, open air swimming pools, parks, gardens, and sidewalk cafés. Sunbathers typically wear limited amounts of clothing or some simply go nude. An alternative some use to sunbathing is to use a sunbed that generates ultraviolet light and can be used indoors regardless of outdoor weather conditions and amount of sun light.

For many people with pale or brownish skin, one purpose for sunbathing is to darken one’s skin color (get a sun tan) as this is considered in some cultures to be beautiful, associated with outdoor activity, vacations/holidays, and health. Some people prefer nude sunbathing so that an “all-over” or “even” tan can be obtained.

Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes and it is actually an automatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the sun or from artificial sunlamps. Thus, the tan gradually disappears with time, when one is no longer exposed to these sources.

When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. The World Meteorological Organization uses the term “sunshine duration” to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter.

Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. Sunlight takes about 8.3 minutes to reach the Earth.

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultraviolet light. Bright sunlight provides illuminance of approximately 100,000 lux or lumens per square meter at the Earth’s surface.

Sunlight is a key factor in photosynthesis, a process crucially important for life on Earth.

Life on Earth

The existence of nearly all life on Earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight, combined with minerals and air, to produce simple sugars—a process known as photosynthesis. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.

Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either directly or by consuming other heterotrophs. The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This process is known as respiration.

In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. They used animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow.

During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Animals which had previously only provided humans with meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans.

The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e.g. alternative fuels, Malthusian catastrophe, new urbanism, peak oil).

The Sun’s color is white, although from the surface of the Earth it may appear yellow because of atmospheric scattering. Its stellar classification, based on spectral class, is G2V, and is informally designated a yellow star, because the majority of its radiation is in the yellow-green portion of the visible spectrum. In this spectral class label, G2 indicates its surface temperature of approximately 5,780 K (5,510 °C.), and V (Roman five) indicates that the Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. Astronomers once regarded the Sun as a small and relatively insignificant star, it is now presumed to be brighter than 85% of the stars in the Milky Way galaxy, most of which are red dwarfs. Estimates for its magnitude are 4.8. The Sun’s hot corona continuously expands in space creating the solar wind, a hypersonic stream of charged particles that extends to the heliopause at roughly 100 AU. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.

The Sun is currently traveling through the Local Interstellar Cloud in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way galaxy. Of the 50 nearest stellar systems within 17 light-years from Earth, the Sun ranks 4th in mass. The Sun orbits the center of the Milky Way at a distance of approximately 24,000–26,000 light years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225–250 million years.

The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though this varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight supports almost all life on Earth via photosynthesis, and drives Earth’s climate and weather. The enormous impact of the Sun on the Earth has been recognized since pre-historic times, and the Sun has been regarded by some cultures as a deity. An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun’s physical composition and source of energy. This understanding is still developing; there are a number of present-day anomalies in the Sun’s behavior that remain unexplained.