The sun is the main source of energy on Earth. Without it, the existence of life would be impossible. And although everything literally revolves around the Sun, we very rarely think about how our star works.

Structure of the Sun

To understand how the Sun works, you first need to understand its structure.

• Core.
• Radiant transfer zone.
• convective zone.
• Atmosphere: photosphere, chromosphere, corona, solar wind.

The diameter of the solar core is 150-175,000 km, about 20-25% of the solar radius. The core temperature reaches 14 million degrees Kelvin. Inside, thermonuclear reactions constantly occur with the formation of helium. It is in the nucleus as a result of this reaction that energy is released, as well as heat. The rest of the Sun is heated by this energy, it passes through all the layers to the photosphere.

The radiative transfer zone is located above the nucleus. Energy is transferred by emitting photons and absorbing them.

Above the radiative transfer zone is the convective zone. Here, the transfer of energy is carried out not by reemission, but by the transfer of matter. With high speed, the colder matter of the photosphere penetrates into the convective zone, and the radiation from the radiative transfer zone rises to the surface - this is convection.

The photosphere is the visible surface of the Sun. Most of the visible radiation comes from this layer. Radiation from deeper layers no longer penetrates into the photosphere. The average layer temperature reaches 5778 K.

The chromosphere surrounds the photosphere, it has a reddish hue. From the surface of the chromosphere constantly occur emissions - spicules.

The last outer shell of our star is the corona, which consists of energetic eruptions and prominences that form the solar wind, which spreads to the farthest corners of the solar system. The average temperature of the corona is 1-2 million K, but there are areas with 20 million K.

The solar wind is a stream of ionized particles propagating to the edges of the heliosphere at a speed of about 400 km/s. Many phenomena on Earth are associated with the solar wind, such as the aurora and magnetic storms.

solar radiation

The solar plasma has a high electrical conductivity, which contributes to the appearance of electric currents and magnetic fields.

The sun is the strongest emitter of electromagnetic waves in the world, which gives us:

• ultra-violet rays;
• visible light - 44% solar energy(mainly yellow-green spectrum);
• infrared rays - 48%;
• x-ray radiation;
• radiation radiation.

Only 8% of the energy is spent on ultraviolet, X-ray and radiation radiation. Visible light lies between the infrared and ultraviolet rays.

Also the sun is powerful source non-thermal radio waves. In addition to all kinds of electromagnetic rays, a constant stream of particles is emitted: electrons, protons, neutrinos, and so on.

All types of radiation exert their influence on the Earth. This is the impact we are experiencing.

Exposure to UV rays

Ultraviolet rays affect the Earth and all living beings. Thanks to them, the ozone layer exists, since UV rays destroy oxygen, which is modified into ozone. The Earth's magnetic field, in turn, forms the ozone layer, which, paradoxically, weakens the power of UV exposure.

for living organisms and environment Ultraviolet influences in many ways:

• promotes the production of vitamin D;
• has antiseptic properties;
• causes sunburn;
• enhances the work of hematopoietic organs;
• increases blood clotting;
• the alkaline reserve increases;
• disinfects surfaces of objects and liquids;
• stimulates metabolic processes.

It is ultraviolet radiation that contributes to the self-purification of the atmosphere, eliminates smog, smoke and dust particles.

Depending on latitude, the strength of exposure to UV radiation varies greatly.

Exposure to IR rays: why and how the sun warms

All heat on Earth is infrared rays, which appear due to the thermonuclear fusion of hydrogen to form helium. This reaction is accompanied by a huge release of radiant energy. About 1000 watts per square meter reaches the ground. It is for this reason that IR radiation is often called thermal radiation.

Surprisingly, the Earth acts as an infrared emitter. The planet, as well as the clouds, absorb infrared rays and then re-radiate this energy back into the atmosphere. Substances such as water vapor, water droplets, methane, carbon dioxide, nitrogen, some fluorine and sulfur compounds emit infrared rays in all directions. It is thanks to this that the greenhouse effect takes place, which maintains the surface of the Earth in a constantly heated state.

Infrared rays not only heat the surfaces of objects and living beings, but also have other effects:

• disinfect;
• improve metabolism;
• stimulate blood circulation;
• relieve pain;
• normalize the water-salt balance;
• strengthen immunity.

Why is the sun weak in winter?

Since the Earth revolves around the Sun with some axial tilt, in different time year, the poles deviate. In the first half of the year, the North Pole is turned towards the Sun, in the second - the South. Accordingly, the angle of exposure to solar energy changes, as well as power.

If you look at the Sun, when it is partially obscured by clouds and hidden behind these clumps of atmospheric water, you can see a familiar sight: beams of light breaking through the clouds and falling to the ground. Sometimes they seem to be parallel, sometimes they seem to diverge. Can sometimes see the shape of the Sun through clouds. Why is this happening? Our reader this week asks:

Can you explain to me why on a cloudy day you can see the rays of the sun breaking through the clouds? It seems to me that since the Sun is much larger than the Earth, and since its photons reach us along roughly parallel paths, we should see the entire sky evenly lit, rather than seeing a small ball of light.

Most people do not even think about the amazing fact of the existence of sunlight.

On a typical sunny day, the entire sky is lit up. The Sun's rays hit the Earth almost parallel, because the Sun is very far away and it is very large compared to the Earth. The atmosphere is transparent enough for all sunlight to reach the Earth's surface or be scattered in all directions. The last effect is responsible for the fact that on a cloudy day something can be seen on the street - the atmosphere perfectly scatters sunlight and fills the surrounding space with it.

That is why on a bright sunny day your shadow will be darker than the rest of the surface on which it falls, but still remain highlighted. In your shadow, you can see the earth in the same way as if the Sun were hidden behind the clouds, and then everything else becomes as dim as your shadow, but still illuminated by diffused light.

With this in mind, let us return to the phenomenon of solar rays. Why is it sometimes possible to see rays of light when the sun hides behind clouds? And why do they sometimes look like parallel columns and sometimes diverging?

The first thing to understand is that the scattering of sunlight, when it collides with particles of the atmosphere and is redirected in all directions, always works - the Sun hides behind clouds or not. Therefore, during the day there is always a basic level of illumination. That's why it's "day," and that's why to find darkness during the day, you have to go deeper into the cave.

But what are rays? They come from gaps or thin patches of clouds (or trees or other opaque objects) that do not block sunlight. This direct light appears brighter than its surroundings, but is only noticeable if it contrasts against a dark, shadowy background! If this light is everywhere, there will be nothing remarkable in it, our eyes will adjust to it. But if a bright beam of light is brighter than its surroundings, your eyes notice this and tell you the difference.

What about the shape of the rays? You might think that clouds work like lenses or prisms, deflecting or refracting rays and causing them to diverge. But it's not; Clouds absorb and re-emit light equally in all directions, which is why they are opaque. The ray effect only occurs where the clouds do not absorb most of the light. When taking measurements, it turns out that these rays are actually parallel, which corresponds to a large distance from the Sun. If you observe rays that are not directed towards you or away from you, but perpendicular to your line of sight, you will find exactly this.

The reason why it seems to us that the rays "converge" towards the Sun is the same reason why it seems to us that the rails or the roadbed converge at one point. These are parallel lines, one part of which is closer to you than the other. The sun is very far away, and the point from which the beam comes is farther from you than the point of contact with the Earth! It's not always obvious, but that's why the beams take on the shape of beams, which is very noticeable when you can see how close you are to the end of the beam.

Therefore, we owe the presence of the ray to the perspective of the shadows surrounding it and the ability of our eyes to distinguish between the brightness of direct light and the relative darkness surrounding it. And the reason the rays seem to converge is because of perspective, and because the landing point of these actually parallel rays of light is closer to us than their starting point at the bottom of the clouds. That's the science behind sunbeams, and that's why they look the way they do!

Photos from open sources

Scientists have been talking about the benefits of sunlight and sunbathing for a long time. More recent studies by a group of scientists led by Richard Weller (Edinburgh) found that when a person is in the sun, blood pressure decreases, the formation of blood clots decreases, and therefore the sun not only improves health, but also prolongs life, and can prevent the occurrence of serious diseases such as stroke and a heart attack.
The influence of sunlight on all living things is difficult to overestimate. And the fact is that the sun emits a whole spectrum of waves, from color to invisible. Invisible rays include ultraviolet and infrared rays. We cannot see them, but we feel them in the form of heat. Invisible rays have a great influence on a living organism.

UV is that part of the sun's radiation that gives the skin a nice brown tint and helps the body produce vitamin D, which is necessary for bones. This vitamin is also involved in the regulation of cell division and even to some extent prevents the development of colon and stomach cancer. Under the action of sunlight, the so-called “hormones of pleasure”, endorphins, are produced.

The human body is able to defend itself against harmful compounds produced under the influence of sunlight. DNA damage is quickly restored thanks to a special system that controls its integrity. And if, nevertheless, a change has occurred in the cell, it is recognized by the immune system as foreign and destroyed. Unfortunately, sometimes the body cannot cope with these damages, especially since UV suppresses the activity of the immune system. That is why, having arrived from warm countries, a person often catches a cold.

At the same time, suppression of the immune system is the main mechanism for treating diseases such as atopic dermatitis and some other skin diseases using ultraviolet radiation.

UV is divided into three spectra depending on the wavelength. Each spectrum has its own characteristics of impact on the human body.

• Spectrum C has a wavelength from 100 to 280 nm. This is the most active range, the rays easily penetrate the skin and cause a destructive effect on the cells of the body. Fortunately, such rays practically do not reach the Earth's surface, but are absorbed by the ozone layer of the atmosphere.
• Spectrum B (UVB) has a wavelength of 280-320 nm and makes up about 20% of all UV radiation that hits the Earth's surface. These rays give redness to the skin during sun exposure. They quickly cause the formation of active compounds in human skin, affecting DNA and causing a violation of its structure.
• Spectrum A, whose wavelength is 320-400 nm, accounts for almost 80% of the UV radiation that hits the human skin. Due to the longer wavelength, these rays have 1000 times less energy than UVB, so they almost do not cause sunburn. They are much less conducive to the production of biologically active substances that can affect DNA. However, these rays penetrate deeper than UVB, and the harmful substances they produce remain in the skin much longer.

Sunburn is primarily skin damage.

The damaging effect of the sun gradually accumulates in the body, and can manifest itself many years later in the form of skin cancer.

Parents, please note: if a child has a sunburn that causes blisters, especially if this happened more than once, the risk of developing melanoma in the future increases several times!

People are protected from the harmful effects of sunlight in different ways. Dark-skinned people have more strong protection, and people with red hair or blondes with blue eyes more susceptible to the damaging effects of sunlight.

UV can sometimes contribute to the development of itchy rashes. In solar urticaria, itchy, nettle-like rashes develop between 30 minutes and two hours after exposure. Polymorphic light rash - in 1-2 days. This disease is also manifested by itchy rashes at the site of radiation, but they are slower than solar urticaria, and look different. There are other diseases for which UV is a stimulus to develop. For example, lupus erythematosus, rosacea, pellagra (lack of vitamin B3), and others.

Many medications taken by mouth can cause skin rashes when exposed to sunlight. There are some herbs that, after contact with the skin in the sun, cause severe redness and blistering. First of all, these are plants from the umbrella family, among which the strongest is hogweed. In addition, celery, parsley, lime, parsnips and others can cause such dermatitis.

How to protect yourself from the harmful effects of the sun, and at the same time benefit and enjoy it?

The answer is simple: you need to use sunscreen. It is not necessary to take a cream with maximum protection (SPF 50+). The product, which has SPF 15, already provides 80% protection from the sun's rays. This means that part of the UVB will reach the skin and have its positive effect. For sun protection creams to be effective, it is recommended to apply them 20 minutes before sunbathing, and reapply as recommended, usually every 2 hours. But be careful, the use of these drugs does not mean that you can stay under the sun indefinitely. It was this mistake that at one time led to a sharp increase in the incidence of melanoma - due to the absence of obvious sunburn due to protective cream, some sunbathed for too long.

Scientists have found that in order for the body to produce the amount of vitamin D it needs, it is enough to “show the sun” face and hands for 10-15 minutes a day.

Specialists of the EMC Clinic for Dermatovenereology and Allergology-Immunology will gladly give detailed recommendations on sun protection for you and your entire family.

Many of us love to spend time in the sun, someone wants to soak up the warm rays, and someone is chasing good tan. But is it useful for the body and how does it affect human health? Learn about the benefits and harms of sunlight.

The benefits of sunlight

If you approach this issue wisely, then tanning will positively affect your health. Sunlight produces vitamin D, which is good for bones and teeth and promotes calcium absorption.

Ultraviolet has a beneficial effect on the human immune system. Experts have long proven that the sun slows down the growth of cancer cells. The body receives more oxygen during exposure to sunlight, which improves the functioning of the heart muscle and puts blood pressure in order.

Sun lovers are much less likely to get sick and cope better with stress. When exposed to sunlight, important processes in the body are activated, such as respiration, blood circulation, and metabolism.

Sun damage

If you spend a lot of time in direct sunlight, the risk of skin cancer increases. Do not forget that prolonged exposure to the sun contributes to premature aging of the skin. To avoid such problems, use various oils and creams that will protect the skin from drying out.

We must not forget about burns, the desire to tan quickly and strongly can bring you a lot of inconvenience and harm your health. Be aware of the risk of heatstroke, do not forget that in strong sunshine, your head should be covered.

What is the best time to sunbathe

If you come to rest in warmer climes and want to tan, remember the first 3-4 days you should refrain from long sunbathing. This will only harm you and your skin, and instead of a bronze tan, you can return home with burns.

If we talk about time, we must not forget that in the period from 12:00 to 16:00 the sun is most active and can harm your body. It is worth sunbathing before noon, preferably before 11 o'clock. The most favorable moment is the time from 16:00 to 19:00. During this period, the risk of getting burns is minimal. In addition, evening Sun rays will not affect your vision.

How to protect yourself from sun exposure

Before sunbathing, you should take care of protection. Be sure to purchase a hat with a visor or wide brim to avoid bumps and burns to your face.

Don't forget about sunscreen, which must be applied half an hour before going outside. During this time, the cream will be absorbed and a protective film will form. Apply the product every two hours.

Be mindful of your eyes, protect them with a large visor or sunglasses.

Be careful with your health, remember that in pursuit of a tan you can harm your skin. Enjoy the sun wisely. We wish you good luck and do not forget to press the buttons and

28.07.2015 09:30

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