In this chapter, we will dwell on the planets and other bodies in the universe. The Sun, Moon and Earth are among the ones we are most familiar with. There are, however, other celestial bodies in the universe you are not able to see.
Think about cartoon films or movies about space! The space above the clouds is full of stars, planets and meteorites that you have seen in these films. Each one of these is called a celestial body. Billions of these celestial bodies come together to form the giant collection of star systems we call galaxies. All celestial objects are enormous. For instance, our planet Earth is really quite small in comparison with the other celestial bodies. Despite this, it is big enough to hold human beings, animals, mountains, oceans and everything else you can think of.
Now let us proceed to the giant collection of star systems, the galaxies where billions of stars exist together.
Galaxies are composed of billions of stars. (Stars are big celestial bodies such as the Sun. Neither the Earth nor the Moon is a star.) There are about three trillion stars in the biggest galaxy. In a galaxy of an average size, there are about 200 to 300 billion stars, while there are about 100 billion stars in a small galaxy
Now let's stop and think for a moment: What does the number one billion mean to you? For example, if you put two zeros next to the number one, it becomes 100. If you add one more zero to this number, it becomes 1,000. Add another zero and now you have the number 10,000 (ten thousand). Can you count up to 10,000? Maybe you can, but this will probably take a long time. Meanwhile, we still have not reached a billion. Then let us add two more zeros to 10,000. Now we have 1,000,000 (one million). We are still short of the number of stars in galaxies. However, if you put three more zeros next to 1,000,000, you reach the number 1,000,000,000 (one billion). Can you count up to 1,000,000,000? Let's answer this outright: Counting up to one billion would take a few decades, a decade being a period of ten years.
Now we have almost reached the number of stars in galaxies. If you put two more zeros next to the number 1,000,000,000, it becomes 100,000,000,000 (one hundred billion). This is the number of stars in the smallest galaxies.
Now do you have some idea of the size of the universe? If you spent all your life doing nothing but counting numbers, you would still fail to count all the stars in space. Allah, the Creator of the universe, has created this vast space that you are unable to imagine from nothing, and He encompasses every point of this immense universe every moment. Allah knows and sees every being in our giant universe, and everything that happens. The infinite power of our Lord is related in the Qur'an as follows:
... He knows what is in the heavens and what is on earth. Allah has power over all things. (Surah Al 'Imran: 29)
Now let's return to our topic and try to learn more about the galaxies.
In galaxies of average or large size, there exists a galactic centre. Around the galactic centre are arms rotating at immense speed. These arms are made up of stars, gas and dust clouds.
With their arms and centres, galaxies are the biggest celestial bodies in space. These giant celestial bodies also form clusters of celestial bodies. There are thousands of galaxies in some galactic clusters. Moreover, these galactic clusters form other clusters of celestial bodies. This regular clustering goes on and on, getting bigger and bigger.
Now let's go over what we have seen so far:
- Galaxies are composed of billions, even trillions of stars.
- The big and average galaxies have galactic centres.
- The galaxy has arms made up of stars, gas and dust clouds. These arms spin around the galactic centre at great speed.
- The galaxies come together to form galactic clusters. Sometimes, there may be thousands of galaxies inside a galactic cluster. The galactic clusters also come together in clusters of clusters.
Keep in mind that a galaxy composed of 100 billion stars is a small galaxy, not to mention that every star is at least as big as the Sun. In addition, there are both large and small planets such as our Earth that spin around many of these stars.
Now, consider the following: Could billions of stars gather together by chance in an orderly manner? Could the stars spontaneously establish an order in which they can move without colliding with other celestial bodies (for instance our Earth and other planets)?
These are all unlikely. This means that the stars' spinning and moving at great speed without colliding with other celestial bodies since the first day of their existence is a sign of the existence of a Creator, a Planner and an Organiser, Allah, the Ruler of the universe. Allah has created countless paths for the planets, stars and comets in space. All these celestial bodies follow their own paths without colliding with one another.
Now let's continue our journey with our galaxy.
The Milky Way
The Milky Way is the name of the galaxy in which our Earth is located. The Milky Way galaxy is enormous. As is the case with all big galaxies, the Milky Way also has a galactic centre. You will probably remember what a galactic centre is since we discussed it in the previous section. The stars inside these centres are older stars; they are red or yellow in colour. The stars in the arms of the galaxies are mostly young and hot stars of blue colour. These aside, gas and dust clouds exist in these arms.
The Milky Way has the shape of a spiral; in fact, the shape of the galaxy is identical to a "pinwheel". That is, it has arms at the centre extending towards the outer parts. There are four arms. One of these is the "Hunter Arm". The group of planets called the "Solar System" is located in this arm, and our Earth is one of the planets within this group.
Our Solar System is located a little more than one half of the way out from the centre of this spiral-shaped galaxy. The Sun (and our solar system) is revolving around the centre of the galaxy, and makes a complete revolution every 220 million years or so.
The giant Milky Way has maintained this form and movement for billions of years. Although the stars in it revolve at great speed, they preserve their own paths.
However, it is not possible for stars to form such patterns on their own. It is also impossible for them to reach agreement; that is to line up in the most appropriate way and to move in an organised manner. Nor is it possible for the laws that govern these stars to have formed by themselves. Think about the stones in your garden! Could these stones take a decision and say, "Let some of us form the centre and the rest take up positions on the arms, and then perpetually spin in the garden"? Would you believe someone who says he had heard the stones talking to each other in this way? No doubt, you would not. By the same token, saying that the Milky Way came into existence by coincidence and the stars started to move of their own accord would be as funny as the example of stones in the garden. Keep in mind that celestial bodies are non-living, unconscious beings just like the stones in the garden.
No power other than Allah is capable of creating billions of giant stars in an orderly universe. Allah created them and the laws to which they are subject. They all testify to His power and control over the entire universe. For that reason, each piece of information we learn about the universe reminds us of Allah's existence and His creation of it. This way, Allah also shows us His infinite wisdom and knowledge.
Now, let us proceed to the stars.
Stars and planets come into existence through the compression of the masses of gases and dust in space called "nebulae". For this reason, nebulae, the sources of celestial bodies, have a major role in the universe. Nebulae do not have any light of their own as is in the case of stars. Therefore, it is hard to see them. They become visible only when their inner gas gives off light or if they reflect the light coming from stars. We can also see them when they pass by a source of light.
Stars give off heat, light and energy. Apart from tiny stars, there are also very large stars. Surprisingly the Sun is not a major star as we believe to be; There are many stars much bigger than it.
Well, did you know that stars also have life spans? Stars are not living beings, but just like them, they are born, lead a life and die.
Well, did you know that stars also have life spans? Stars are not living beings, but just like them, they are born, lead a life and die.
Now, let's take a tour in our Solar System and see how it looks!
The Solar System
In our Solar System, there are nine major planets with 61 satellites and countless asteroids, all revolving around a single star called the "Sun". The Sun is located at the heart of the Solar System.
These nine planets, which are a part of our Solar System, revolve around themselves as well as the Sun in an orderly pattern. Let us review the names of the planets starting from the one closest to the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. As you can see, our Earth is the third planet from the Sun.
Every planet within the Solar System has different features. The temperatures on some of these planets are high enough to cause lead to melt. Others, on the other hand, are totally covered with ice. Some of the planets are entirely composed of gases. Moreover, some planets are as tiny as the Moon.
There is a very harmonious relationship between the satellites and their primaries. (In astronomy, a primary is something that another body revolves about. Earth's primary is the Sun; the Moon's primary is Earth.) Planets attract their satellites. However, satellites balance this attraction. Without such a balance, satellites would become stuck to the planets or break loose into space.
For instance, if the Moon rotated slower, it would plunge into Earth at an immense speed. This would mean the end of Earth. If it rotated faster, it would gradually move away from Earth and would no longer be our satellite.
Now let's look at the Sun, the heart of our Solar System.
The Sun is the greatest celestial body in the Solar System. It consists of very hot, glowing gases. Every second, explosions occur all over its surface, for the Sun itself is an enormous nuclear bomb. These surface explosions are equivalent to the energy given off by millions of atom bombs. They shoot off flares 40-50 times larger than our Earth.
The Sun looks like a ball of fire and gives off enormous heat and light from its surface. If the Sun did not exist, it would always be night for us, and our whole world would be covered with ice. Most importantly, there would be no life on Earth.
Space (you will also remember the films about the space) is a very dark, huge, empty place. Our Earth is a celestial body in this dark expanse, and no other celestial body is near enough to illuminate and heat our Earth.
The light from the Sun is very bright. You have probably tried looking at the Sun on a clear day. After looking for a few seconds, your eyes were dazzled, weren't they? Because its light is very bright, looking straight at the Sun is very dangerous for our eyes. As well as that, being exposed to sunlight for a long time in summer is dangerous. Severe sun-burns may occur on our skin, and they only heal up after medical treatment. Especially in summer, the heat radiating from the Sun is very high. However, the Sun is millions of kilometers away from Earth, and only one part in two-thousand of the heat it radiates reaches Earth.
If the temperature of Earth is so high despite the distance between Earth and the Sun, can you imagine how hot the Sun is?
Scientists provide approximate values for this. However, we cannot have any idea of this temperature by trying to compare it with the temperature of anything we are familiar with in this world. Consider that on the surface of the Sun, the temperature is 6,000°C (11,000°F). Inside, it rises as high as 12,000,000°C (21,600,000°F). There is nothing as hot on Earth with which you could compare this temperature! Your hands can hardly touch water around 50°C (120°F). Even on hot summer days, the temperature remains at about 40–50°C (105-120°F). This example shows that Allah tuned the distance between Earth and the Sun most delicately. If the Sun were a little closer to us, everything on the world would be withered and dried by the heat and turn into ashes. However, if it were a little more distant, everything would freeze. Of course, life would not be possible in either case.
Polar regions, where heat from the Sun is received less, are always covered with ice. The equator, on the other hand, the region where many more solar rays are received, is always hot. Allah has created these regions as examples for us. Other regions are more suitable to support life for human beings. This shows the mercy Allah pours down on us. That is because, if Allah had not tuned the distance between the Sun and Earth so delicately, life on Earth would be much harder for us. There might even be no life at all.
As we have explained earlier, Allah created the Sun and the Moon exactly the way it has to be for human life to exist on our planet. In the Qur'an, Allah informs us that the Sun and the Moon move by the command of Allah:
Allah is He Who raised up the heavens without any support—you can see that—and then established Himself firmly on the Throne. He made the sun and moon subservient, each running for a specified term. He directs the whole affair. He makes the Signs clear so that hopefully you will be certain about the meeting with your Lord. (Surat ar-Ra'd: 2)
The Gravitational Attraction of the Sun
Countless celestial bodies move in an orderly manner without colliding with one another because Allah placed them in finely-adjusted orbits. An orbit is the path a planet or comet follows as it revolves around the Sun. No planet stops following its orbit to fly off into the depths of outer space. That is because planets remain under the gravitational attraction of the Sun. As you read these lines, our Earth is moving at the enormous speed of 108,000 kilometres (70,000 miles) per hour in its orbit around the Sun. An analogy may help you to grasp the enormity of this speed: the maximum speed a car can travel is around 200 kilometres (125 miles) per hour. This means the speed of Earth's rotation around the Sun is 540 times the speed of a car. Another example is the following: a bullet moves at a speed of 1,800 kilometres (1,100 miles) per hour. The speed of Earth's rotation around the Sun is 60 times the speed of a bullet.
On the other hand, if the Sun started to exert an even greater gravitational force, then our Earth would plunge into the Sun and melt. In this case, we would also vanish. Furthermore, the gravitational pull of the Sun also prevents the planets in their respective orbits from colliding with each other. However, have you ever thought how the Sun attracts these planets?
The answer is obvious. It is our Creator Allah, Exalted in Power, Who creates and continually preserves these balances.
Besides, not only the Sun has a gravitational pull. The planets within the Solar System also have their own gravitational forces. For instance, the gravitational force of Earth attracts the Moon towards it. Because of this gravitation, the Moon is almost suspended at a certain distance. In this way, Earth does not collide with the Moon. Without doubt, the infinite might of Allah prevents the Moon from falling onto Earth.
There is another gravitational pull similar to that of the sun, which is specially designed for mankind to live. That is the gravitational pull of the earth that gives us our weight. The gravitational force, which we experience as weight, holds us on Earth and provides us with the ability to walk and run with ease without floating off into space.
Assume that there is a ball in your hand. What happens when you withdraw your hand? The ball drops, doesn't it? That is because gravity attracts it to the ground. However, if you left this ball far out in remote outer space, the ball would not fall down since there is less gravitation there. Therefore, the existence of the higher force of gravity on Earth is essential for us.
There is another very important detail about gravitation: Gravitation should be neither more nor less than its current force. If it were less, you would be walking up in the air and not be able to touch the floor with your feet. You would not be able to move as you wish; you would constantly drift from one place to another, bounce when you take a step and hit the ceiling. Similarly, if the gravitational force of Earth were greater, you would not be able to walk because you would be drawn down towards the ground. You would only be able to crawl along the ground, if that.
Yet, none of these happen to us; Allah has created exactly the right strength of gravitation for us.
You can attain a better understanding of this by help of an example: The Moon, like Earth, also has a gravitational force. However, this gravitational pull is less than the one on Earth. Therefore, it is not possible for you to survive on the Moon. On television, you have probably seen how astronauts walk on the Moon. Could we spend our entire life this way? Definitely not.
Now let us continue our journey by visiting the planets within the gravitational pull of the sun.
We mentioned earlier that planets are the celestial bodies that rotate around the stars. In this section, we are going to examine the planets in the solar system our Earth is located in. If we assume the Solar System to be a circle, the Sun is right at the centre of it.
Pluto is the planet on the outermost circle. Pluto is the smallest and farthest planet from the sun. Observation of this planet is hard, and even the Hubble telescope can only show some rough details of its surface. This planet is quite a cold place. The temperature is around -238°C (-396°F). In winter, when the temperature on Earth dips below -2 or -3°C (28 or 26°F), it becomes freezing. -238°C (-396°F) is a temperature 100 times colder than a temperature we on Earth can hardly resist in wintertime. This kind of cold would end our lives. From the outside, Pluto looks like a ball covered in ice.
Moving a little further towards the sun, in the middle of the circle, we meet Uranus. Uranus is the third largest planet in the Solar System. The temperature of its atmosphere is about -214°C (-353°F), which means this planet is cold enough to freeze us in only a second. Its atmosphere consists of poisonous gases that definitely would not support life.
If we continue our journey towards the sun, we next encounter Saturn. This, the second largest planet of the Solar System, is particularly notable for the system of rings around it. These rings are made up of gases, rocks and ice. The temperature on this planet is again unsuitable for human life: -178°C (-288°F).
When we come even closer to the sun, we encounter Jupiter, the largest planet of the Solar System. Jupiter is a planet 11 times bigger than Earth. Conditions on this planet are again not suitable for life, and it is a very cold place.
After Jupiter comes Mars. Mars is a dead planet that does not even compare to Earth. Mars has no life on it. There are reasons for this: First, the atmosphere of Mars is a poisonous mixture containing concentrated carbon dioxide. Second, there is no water on the planet. Third, the temperature on Mars is about -53°C (-63°F). Finally, there are very strong winds and sandstorms on Mars that last for months.
The blue planet that appears before us after Mars is our Earth. We will focus our attention on our planet Earth in the last chapter. Meanwhile, let's remind you of one point: Our Earth is the only planet that allows organisms to live.
Heading towards the sun, our search brings us to a planet called Venus. Venus is the brightest celestial body after the Sun and Moon. Therefore, people have known it since ancient times. Although all the planets as far out as Saturn have also been quite familiar to people throughout the ages, Venus is incomparably bright and clear in both the morning and evening skies. In contrast to the other planets, Venus is very hot. The temperature on the surface is 450°C (840°F), which is enough to cause even lead to melt. Another feature of Venus is its heavy atmosphere composed of a concentrated layer of carbon dioxide. Besides that, the atmosphere of Venus contains layers of acid several kilometres deep. No organism could survive in such a place for a second.
Speeding away from Venus, we reach Mercury, the planet closest to the sun. Its rotation has been so slowed down by its proximity to the Sun that the planet makes only three full turns in the time it takes to revolve twice around the sun. That is why one side of Mercury is extremely hot while the other is extremely cold. The difference between the day and night sides of Mercury is as much as 1,000°C (1,800°F). Of course such an environment cannot support life.
Our search so far reveals that except for Earth, none of the planets in the Solar System offers anything that might serve as a haven for life. Each of them is a lifeless and silent body. Our world, however, is a planet that provides everything necessary for life. With its green forests and blue oceans, it looks beautiful from space. The first astronauts on the Moon were astonished by the colourful and bright view they had of Earth.
Other Celestial Bodies
Some other celestial bodies in the Solar System are comets, asteroids and meteorites. These are the celestial bodies remaining from the nebula in which the Solar System originated four to six billion years ago.
- Comets are made up of condensed gases and dust. Sometimes, their orbits bring them closer to the sun. As the comet approaches the sun, its surface starts evaporating because of the heat. This evaporation causes a bright light. A huge ball of gas and dust appears around the nucleus. This ball of gas and dust is called a "coma". Also, there is a tail of gas and dust related to this coma.
- Meteors are rocky objects in space. Usually, they are observed in between the orbits of Mars and Jupiter. In some cases, the diameter of meteors may be as much as 1,000 kilometres (620 miles).
- Meteorites are solid bodies which fall to Earth from outer space. Pieces of rock, or mixtures of rock and iron detach themselves from meteors and comets. Sometimes when Earth passes through the dust cloud remaining from a comet, for example, the objects within this dust cloud burn in the atmosphere. They heat up when they enter Earth's atmosphere and leave a fine line of light in the sky. This is called a meteor. Sometimes, when they do not burn completely, meteors strike the Earth. These meteors that reach Earth are called aerolites or meteorites.
Consider one important point here: Meteors that reach the atmosphere occasionally fall on the Earth. When they fall, the destruction they cause varies according to their size. Our Earth is vulnerable to such a threat at every moment, but our Lord has created these celestial bodies in such a way that they are usually burned and destroyed in the atmosphere and thus are no danger to us. This shows Allah's mercy and compassion for us as well as the protection He provides us.
You must now have grasped that Allah has control over all celestial bodies, whether huge or small, and governs them all at every moment in a planned and orderly manner.