Earth's physical features—mass, structure, temperature and so on–are "just right for life". Such features alone are not enough to allow life to exist on Earth however. Another vital factor is the composition of the atmosphere.
Science fiction films sometimes mislead people. One example of this is the “suitable atmospheric conditions” that are frequently encountered in these films. Astronauts approaching a distant planet in their spacecraft look to see whether the atmosphere is breathable or not before landing. When the computer on their ship reports that the atmosphere is “suitable,” there is no need for any further protective measures …
These scenarios give people the impression that mankind could easily and randomly find suitable atmospheres. If we could explore the real universe, we would discover that this is not true at all: the possibility of another planet's having an atmosphere that we could breathe is minute. That is because the atmosphere of the Earth is specially designed to support life in a number of crucial ways. Even a short way beyond this atmosphere it is impossible to survive without protective clothing.
The atmosphere of Earth is composed of 77% nitrogen, 21% oxygen, and 1% carbon dioxide. Let's start with the most important gas: oxygen. Oxygen is vitally important to life because it enters into most of the chemical reactions that release the energy that the complex life forms like human beings require.
The interesting aspect of this is that the percentage of oxygen in the air we breathe is very precisely determined. In his book Nature's Destiny: How the Laws of Biology Reveal Purpose in the Universe the famous professor of microbiology Michael Denton writes:
Could your atmosphere contain more oxygen and still support life? No! Oxygen is a very reactive element. Even the current percentage of oxygen in the atmosphere, 21 percent, is close to the upper limit of safety for life at ambient temperatures. The probability of a forest fire being ignited increases by as much as 70 percent for every 1 percent increase in the percentage of oxygen in the atmosphere. (Michael Denton, Nature's Destiny:How The Laws of Biology Reveal Purpose in the Universe, The New York: The Free Press, 1998, p. 121)
The fact that the proportion of oxygen in the atmosphere remains at this precise value is the result of a marvelous "recycling" system: Animals constantly consume oxygen and produce carbon dioxide, which, for them, is not breathable. Plants do just the opposite: they take in carbon dioxide, which they need to live, and release oxygen instead. So, life goes on. Plants release millions of tons of oxygen into the atmosphere every day.
Without the cooperation and balance of these two different groups of living things, our planet would be uninhabitable. For example, if living things only took in carbon dioxide and released oxygen, the Earth's atmosphere would support combustion much more easily than it does and even a tiny spark could set off enormous fires.
Similarly, if both took in oxygen and released carbon dioxide, life would eventually die out when all the oxygen had been used up.
However, the balance of life has been so perfectly set up that the oxygen in the atmosphere is always at the ideal level for life. A balance so flawlessly designed and that remains so perfect at every moment shows once again the infinite knowledge and power of its Creator. That Lord of Universe, the Creator of the heavens and the earth, is the Almighty Allah.
Allah calls on to man to consider this truth in a verse from the Qur’an:
Do you not see that Allah has subjected to you everything in the heavens and earth and has showered His blessings upon you, both outwardly and inwardly? ... (Surah Luqman, 20)
