◉ Our greatest concern about our planet today is surely global warming, and the main cause is said to be carbon dioxide emissions by mankind. However, while environmental protection issues are extremely important, the question of global warming is not quite as simple as that. There is no doubt that CO2 is a substance that contributes to global warming, but exactly how the concentration of CO2 in the atmosphere affects the climate and the weather is still not very well understood. By all rights, an increase in the CO2 concentration should cause a flourishing of plants that grow by assimilating CO2 , which in turn should cause an increase in the output of oxygen. Conversely, a rise in the concentration of oxygen increases the risk of wildfires, which reduce the vegetation. This example of how the ecosystem helps keep the substances in the atmosphere in balance is also an illustration of James Lovelock’s Gaia hypothesis. But through urbanization and deforestation in addition to the increase in CO2 output, mankind is wreaking havoc with our planet’s balance system.
◉ However, in recent years a theory has appeared of another cause of global warming that is hard to blame on the doings of mankind. That is the activity of the sun. Rises and falls in the number of sunspots have previously been linked with all sorts of phenomena from grain prices in the UK and monsoon damages in India to the vagaries of fashion, but none of these cases seem to have any definite factual basis. The sun’s activity actually exerts a much clearer and more direct influence on the Earth. When the number of black spots go up on the surface of the sun, so do the number of white spots, or hotspots, and the total energy is said to increase by 0.1%. The light from the sun heats up the Earth correspondingly. The 20th century was a time of particularly high white spot activity, and according to some calculations, it caused the Earth’s temperature to rise by as much as 0.25°C. At least in the 20th century, this was more than the effect caused by increased CO2 emissions. This means that even if we somehow succeed in curbing our CO2 emissions, a tiny quirk of the sun may still cause a dramatic rise in the Earth’s temperature. At any rate, the sun is approximately 40% brighter now than when the Earth was formed. That, however, is no excuse for modern civilizations. As St. George is reputed to have said, “even if the Earth were to go under tomorrow, I would still sow my apple seeds today.”
◉ Life has evolved on Earth while the planet has maintained a very delicate balance. It is believed that if the Earth’s orbit in the solar system had been just 1% smaller or 5% larger, it would have been unable to sustain life. Furthermore, if the planet had been slightly larger, it would have had more volcanoes and become like Venus. If it had been slightly smaller, the lower gravity would have caused the planet to lose its atmosphere, and it would have been like Mars. In addition, even if all these conditions were met, unless there was a satellite (i.e. a moon) of a suitable size, the axis of rotation of rotation would be unstable and the planet would be unfit for life, some theories claim.
◉ But above all, the Earth is full of water. Together with the size of the Earth and its position in the solar system, water is the major reason that life could sprout on the planet’s surface. To us, the inhabitants of Earth, water seems like the most common and ordinary of substances, but actually it is one of the strangest substances of all.
To begin with, water is the only chemical compound in the global environment that appears in all three states: solid, liquid and gas. For other hydrogen compounds with similar chemical formulas to water, the boiling point rises with increasing molecular weight – water is the only exception. If water were to behave like the other compounds, it would boil at -90°C, and the Earth would be a vapor planet like Venus. Not only that, but water’s highest density is at 4°C. This is also very different from the normal case, where density in liquids increase with lower temperature, and the solid state has an even higher density. Once again, if water were to behave like other substances, lakes, seas and oceans would be completely frozen and the existence of life would be threatened. Moreover, since the positive and negative charges of the water molecule are separated from the center, water makes an excellent solvent. For this reason, large quantities of salt have dissolved into the oceans, which were originally fresh water. This is of course also why water is indispensible for life itself, and why around 70% of the human body consists of water.
◉ When looked at objectively, our watery Earth is a rather strange planet. Even stranger is the fact that the components of the oceans have hardly changed at all over at least the past 700 million years. That is why the amount of salt in human blood is still extremely close to that of the oceans, even though it has been over 300 million years since our distant ancestors evolved from sea creatures to land creatures. And as with the carbon dioxide in the atmosphere, the activities of living things play a great role in maintaining the material balance of the seas.