In: Categories » Education and reference » The Universe » The Mass of the Earth and the Planet`s Magnetic Field
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The size of Earth is no less important for life than are its distance from the Sun, its rotational speed, or geographical features. Looking at the planets we see a great range of sizes: Mercury is less than a tenth the size of Earth while Jupiter is 318 times bigger. Is the size of Earth as compared with other planets "coincidental"? Or is it deliberate? When we examine the dimensions of Earth we can easily see that our planet was designed to be exactly as big as it is. American geologists Frank Press and Raymond Siever comment on Earth's "fitness": And Earth's size was just about right -not too small as to lose its atmosphere because its gravity was too small to prevent gasses from escaping into space, and not so large that its gravity would hold on to too much atmosphere, including harmful gases. In addition to its mass, the interior of Earth is also specially designed. Because of its core, Earth has a strong magnetic field whose role in the preservation of life is vital. According to Press and Siever: The earth's interior is a gigantic but delicately balanced heat engine fueled by radioactivity …Were it running more slowly, geological activity would have proceeded at a slower pace. Iron might not have melted and sunk to form the liquid core, and the magnetic field would never have developed… if there had been more radioactive fuel and a faster running engine, volcanic gas and dust would have blotted out the Sun, the atmosphere would have been oppressively dense, and the surface would have been racked by daily earthquakes and volcanic explosions. The magnetic field these geologists talk about is of great importance for life. This magnetic field originates from the structure of Earth's core. The core consists of heavy elements like iron and nickel that are capable of holding a magnetic charge. The inner core is solid while the outer one is liquid. The two layers of the core move around each other and this move- ment is what generates Earth's magnetic field. Extending far beyond the surface, this field protects Earth from the effects of detrimental radiation from outer space. The radiation of stars other than the sun cannot travel through this shield. The Van Allen Belt, whose magnetic lines extend ten thousand miles from Earth, protects the globe from this deadly energy. It is calculated that the plasma clouds trapped by the Van Allen Belt sometimes attain energy levels 100 billion times more powerful than that the atomic bomb released over Hiroshima. Cosmic rays may be equally detrimental. The earth's magnetic field however lets only 0.1% of that radiation through and that is absorbed by the atmosphere. The electrical energy needed to create and maintain such a magnetic field is nearly a billion amperes, as much as mankind has generated throughout history. If this protective shield did not exist, life would be destroyed by harmful radiation from time to time and might not have come into existence at all. But as Press and Siever point out, Earth's core is exactly designed to keep the planet safe.
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