The article first appeared in the Young Galileo Youth Journal
My uncle Zosiman
The phenomenon of the seasons
So why is it so hot in the summer? In the summer we notice that it is hotter during the day and there are also more daylight hours in the day. A common mistake is that most people assume that the ellipticity of the Earth's orbit around the Sun brings the Earth closer to the Sun and thus summer is created (closer equals warmer) and in winter the Earth is farther from the Sun and therefore colder. Although it is true that the Earth's orbit is elliptical, this is quite negligible and is not the reason for the existence of the seasons. The change in distance is relatively small, and the shortest distance is, if anything, in the height of winter.
The reason why we experience summer, autumn, winter and spring is the tilt of the earth on its axis.
The Earth is tilted about 23.5 degrees from the rotation axis (see a picture indicating the seasons in Israel according to the inclination of the Earth in relation to the Sun) so that points that are far from the equator receive more direct sunlight in one part of the year and much less in another part of the year.
In fact, Israel located north of the equator absorbs more direct sunlight because the tilt of the Earth brings Israel "closer" to the sun than other parts of the world that receive less direct sunlight at the same time. On the other hand, in winter Israel is inclined towards the "farthest" direction from the sun and therefore receives less direct sunlight. (see the attached picture)
So it turns out that in the summer season Israel receives heat from the sun and there are many more daylight hours. At the same time, in places located on the southern side of the globe such as Australia or South America, there is winter.
For most people, the sun is a constant, everyday and almost self-evident thing. However, many processes discovered by telescopes floating in space only in recent years reveal to us mysterious and hidden things about the sun. About that and more later.
The size of the sun.
The mass of the Sun contains more than 99% of the total mass of the entire solar system. That means the rest of the planets make up a very small part of the total mass of the solar system. The mass of KDWA alone has an even smaller proportion of the total of this percentage. (The mass of the Sun is 330 times the mass of Earth.)
The diameter of the sun is a little more than 100 times the diameter of the Earth, so you can place 100 earth globes in a straight line and they will be swallowed inside the sun itself.
The sun - millions of nuclear bombs per second.
Our sun was formed from a huge gas nebula that resided in the region billions of years ago. Gravity slowly gathered most of the mass of this nebula into a single point and finally shrunk it into a giant ball of gas. As the pressure increases, due to the strong gravitational force on the most central point in that primordial gas ball, a special situation is created which we call "nuclear fusion". The enormous pressure and great heat that acted on the hydrogen nuclei caused a chain of reactions that ended up forming nuclei of a more complex element - helium. During the chain of reactions, a lot of energy is released out into the mantle of the core.
At this point in time the sun was formed (just over 4.5 billion years ago). The sun contains about 92% hydrogen and another almost 8% helium, remnants of other gases, and a few metals. The sun uses the nuclear fusion process at 5 million tons of hydrogen per second. And all this in the last 4 billion years in a row.
This situation between the pressure of gravity contracting inward and against the expanding hot gases created a delicate balance that has been maintained to this day.
For those of the readers who have started to worry a little, you can be reassured that even at this rate, the sun will take another billion years until it consumes all of its "hydrogen fuel".
And what will happen then? Wait for the end.
The tiring journey from the core of the sun to Kdvah
The energy coming out of the sun's core passes in radiation through the extensive "radiation zone" but does not reach the surface directly, but passes from one particle to another in a long process for about 2 million years.
Only when the energy reaches close to the edge, to the relatively narrow "convection zone", does convection of the energy to the surface occur by the rise of hot material to the surface and the descent of cold material below the surface (see the attached picture)
The hot gas reaches a relatively thin layer called the photosphere ("the visible layer"), and from there in a straight line and at the speed of light to all the expanses of the solar system. When we see the sun, we actually only see that part that is exposed to us and radiates to us in a yellow-white color. For those who wondered why the sun actually looks this color, the following explanation is attached:
In Lag Boomer, the curious among us looked at the coals. Some were black, gray but some were very red and even yellowish. These are the hottest coals and the temperature in the depths of the fire could reach hundreds of degrees. The temperature of a body that radiates heat determines its color! This is how we know that the sun radiates at a temperature of about 6000 degrees Celsius because it appears yellowish-white to us.
The uppermost, but invisible layer is the "halo", (the "corona"). It is a very hot layer that can reach up to a million degrees Celsius but it is not visible because it is too thin a layer to be seen against the background of the strong sun. Only in cases of solar eclipse, when the moon hides exactly the entire sun, can the shape of the halo, which can be up to 10 times the diameter of the sun, be seen.
Deadly radiation.
The distance of Earth from the Sun is about 150 million km. According to this distance it is possible to calculate that light coming out of the sun arrives at the speed of light in about 8 minutes, which means we see the light that came out of the sun 8 minutes ago.
A very small part of the radiation washes over the Earth because it is a very small point in the huge solar system, some the other planets and the rest reaches the ends of the solar system and is absorbed even by distant stars.
This energy comes out of the sun in the form of radiation that is partly light and partly heat and partly even deadly radiation.
Fortunately, the atmosphere of the Earth blocks most of the deadly radiation. A layer like the ozone layer participates in this action and recently it is being talked about how important it is to preserve it so that it does not continue to be damaged due to human activity.
A large part of the light and heat passes through the atmosphere and makes sure to warm us during the day and thanks to the dispersion of the heat in the atmosphere - even at night.
In addition, electrons and protons are emitted from the sun, which are very small and fast particles that reach the Earth within 3 days from the moment they leave the sun. We call this phenomenon the "solar wind" and these particles are quite dangerous for anything we send into space. Fortunately for us, the magnetic field of KDWA deflects and suppresses most of the particles so that life in KDWA is saved thanks to it. The particles that do reach the Earth do so only through the poles and in the process create the wonderful phenomenon called the "Northern Lights" or "Aurora" (see attached photo)
The uniform yellow color of the Sun can be deceiving because in better images we manage to see many nuclei. (see attached photo)
Each such nucleus is the size of the Middle East and these are essentially bubbles of material emerging from below using the convection method we mentioned earlier (like a boiling kettle). Each nucleus has its own color according to its heat level. As we already understood, hot nuclei are bright nuclei and in contrast relatively cold nuclei are dark.
This is how we get the "sunspots" phenomenon. It will be discovered that sunspots come in pairs and their appearance has a pattern that repeats itself every 11 years (see the attached graph describing the sunspot cycle from the beginning of the last century). In 2001, for example, there was a year in which a maximum number of sunspots were counted for the same cycle. Since then there has been a decrease that will reach a minimum in 2007, after which it will begin to rise again towards 2011.
The reason for the appearance of sunspots is related to the fact that the rotation speed of the hot gases in the sun is higher in the equatorial region than their rotation speed in the parts closer to the poles. These distortions grow and create a magnetic stress on the sun that erupts in the form of these sunspots.
In more severe cases, these distortions erupt more violently in a phenomenon called "solar storm" (probably in the picture). It is a powerful eruption, with the power of millions of hydrogen bombs that sends huge amounts of gas into space, along with particles.
These eruptions are so strong that they affect the Earth's magnetic field and it was observed that in the past they interfered with the operation of satellites and radio transmissions. This will get worse and worse and you can even harm our way of life as there are more satellites in space and our lives depend on them more.
The sun is the source of life on earth.
The energy of the sun that reaches the earth, heats the atmosphere and the earth and enables reasonable temperatures for the existence of life on our planet. Plants use sunlight to carry out photosynthesis. The solar collectors on the roofs of the houses use the sun's energy to create electricity that heats the solar boilers to provide us with hot water for bathing. The human body uses sunlight to produce vitamin D which helps maintain high levels of calcium and iron in our bodies, therefore it is important to spend a little time in the sun to maintain health, but it is also important to avoid spending too much time in the sun without proper protection (very simple: a wide-brimmed hat, long-sleeved clothes and sunscreen Sunscreen every few hours on exposed areas). In addition, solar energy provides electricity for satellites in space, including those that bring us the beautiful images that accompany this article.
The future of the sun
The sun is actually a star. Almost all the points we see in the night sky are stars and are the suns of the planets of their system if there are any. We watch space and see stars being born, maturing and even aging and ending their lives with a big explosion or a faint hum.
Our sun will also find its death one day. In billions of years the hydrogen fuel will be consumed and the pressure of the spreading hot gases will decrease as a result. The gravity of the great mass of the sun will overcome the diminishing pressure, but this phenomenon will very quickly cause another and stronger pressure than before. Such pressure can even fuse helium into heavier elements like carbon and oxygen. Thus, nuclear fusion will continue to create new and even more energy. The extra energy created in such a process will break out and cause the volume of the sun to increase even more. The sun will turn into a "red giant" - a huge sun whose color is bright red. The nearest planets to the sun, Mercury and Venus, will be swallowed up in the new giant. The summer in the Middle East at such a time will be unbearable and life will no longer be able to survive. The temperature in KDA will rise by hundreds of degrees and the volume of the sun will reach almost to the orbit of KDA. We hope that humanity by that time will have long since left the cradle and found other, younger stars to live in.
After the sun has finished containing all the possible fuel it has, the envelope of gases surrounding the core will escape into space and the relatively small core will remain and will continue to shine with a bright but relatively weak light, a phenomenon called a "white dwarf".
Billions of years later the mantle of gases that will escape into space will gather again under the pressure of gravity and form a new sun again.
Dodi Zusiman is an engineer dealing with space and satellites. and a committee member in the Israel Space Association
The article was first published in Galileo Young magazine, a science newspaper for youth.
