The sun and its benefits

Get to know how the sun plays a key role in life and the planet Earth


The sunrise in the mountains of Iwa-kubo, Japan
Sunrise in the mountains of Iwa-kubo, Japan - Photo by @sebastien.picard

June 21 is a day of celebration all around the globe: the solstice holiday. The UN has labelled this day “The International Day of the Celebration of the Solstice”, a day when the worth of the sun for life on Earth is made evident. Come along with us to further your understanding of the sun’s importance to plants, animals or human beings. See how planet Earth is affected by this celestial body and discover some fun facts about it too!

The importance of the sun for living beings

With a surface temperature of 5,500 ºC (more than 15.5 million degrees at its core), the sun is at the optimal distance from the Earth (150 million kilometers) for just the right light and heat to allow for the existence of plants and animals. Without the sun, there is no life on Earth.

Plants and photosynthesis

Owing to the energy from sunlight, photosynthetic organisms (mainly plants, algae and some bacteria) can carry out photosynthesis, a process which converts absorbed inorganic matter (water and carbon dioxide) into oxygen and organic matter (glucose and starches) that are used as nutrition for growth.

Without the sun, these organisms, could not go through photosynthesis and thereby lead to eliminating the production of oxygen on Earth, which most living creatures depend on to breathe.

A close-up photo of a metallic green insect resting upon a purple flower
Close-up on a metallic green insect on a purple flower - Photo by @Santi gavarres

The influence of the sun on animals

For all animals (including human beings), sunlight is a source of heat which allows them to regulate their body temperature

For wild animals, the sun acts as a cycle regulator, such as mating or migration, which allows for the continuation of the species.

This central star, for which the solar system is named, also benefits animals indirectly through plants. One way animals eventually benefit from the sun through plants, as previously mentioned, is that plants cannot make oxygen without the sun, which is vitally important to animals for being able to breathe. Another way animals end up depending on the sun is that animals eat these plants to get the necessary nutrients for their survival. The herbivores consume them directly whereas the carnivores get them indirectly through the consumption of the herbivores.

The benefits for human beings

The sun is essential for the human organism. One of the most well-known health benefits is the production of vitamin D. The ultraviolet radiation of the sun, once it reaches the skin, helps the organism transform the provitamin D ingested through food into vitamin D. This nutrient is important for healthy bones because it plays a role in the absorption of phosphorus and calcium, which are paramount for its remineralization.

Vitamin D also increases physiological well-being for its role in regulating serotonin: a hormone also known as the “happiness hormone” which is connected with well-being and mood lifting in people.

Fresh air and the sun, a key combination for happiness

For human beings, moreover, the sun accelerates the improvement of some dermatological illnesses for its anti-inflammatory effects, strengthening the immune system through its role in increasing white blood cells and reducing cardovasculatory issues since it promotes proper blood flow and lowers blood pressure.

Two people soaking up the last rays of the sun along a hiking trail in Offersøya, Norway
Hikers soaking up the day’s last sun rays - Photo by @Berzina

Keep in mind that, in excess, especially during peak hours, the sun can also be harmful. In case of prolonged exposure to the sun, it is highly advisable to use sunblock, cover your skin up with clothes, wear a hat and sunglasses, and drink regularly.

The sun’s transcendence over the planet Earth

With a diameter of 1.4 million kilometers and making up 99.86% of the whole mass of the solar system, this dominating star heats up the Earth and prevents it from entering a frozen state, which would otherwise render the chance of life next to null.

Furthermore, the sun plays a key role in the development of some meteorological phenomena such as the wind, keeping the planet Earth in orbit due to its gravitational pull, and lighting up the night (the sun is the only body in the whole solar system which gives off its own light, the white light reflected from the moon is a reflection from the sun’s light).

Yet, the sun is not eternal as it is believed that the great star is about 4.6 billion years old and it has about 5 billion years of life left in a state similar to today’s. After this period of time, it will have burned up all the hydrogen at its core, at which point helium will then become the main source of burning power. This will lead to its enlargement (it will become a red giant) and as a consequence, it will absorb several planets. Once all the helium has been used up, the sun will end up expelling most of its mass in the shape of a planetary nebula (a bright ring of gas and interstellar dust) and all that will remain will be a small core called white dwarf, about the size of Earth, and it will go on cooling down until it dies off forever.

The starry sky in Japan with the moon creating an effect on the camera lens.
The starry sky in Japan with the moon - Photo by @sebastien.picard

Why is the International Solstice Day celebrated on June 21st?

The Earth's trip around the sun is in an elliptical orbit and is slightly tilted (average angle at 23.5º). There are two days of the year in which this inclination causes that while one of the poles is in its closest position to the sun, the other is at its furthest point. This astronomical phenomena called solstice occurs around June 21st and December 21st. When the northern hemisphere enters the summer solstice (June 21st), the southern hemisphere experiences the winter solstice, making for the day with the longest period of light in the northern hemisphere and the shortest amount of daylight in the southern hemisphere.

Historically, the solstices have long been cause for celebration. To this day, the June solstice stands out over the one in December with festivities galore all over the world. For instance, in most parts of Europe, Saint John’s Eve is celebrated every June 23th which welcomes the northern hemisphere’s summer solstice, in spite of not falling exactly on the shortest night of the year, which actually takes place around June 21st. Also, a magical night of fire called “Fallas del Pirineo” takes place in the Pyrenees. When night falls, the local people run down from the mountain tops with lit torches towards their towns and cities, igniting a bonfire around which they then dance traditional dances to celebrate the shortest night of the year.