12. Summary and Discussion

Animal and plant life to some extent is replica of the life inside earth itself. Earth lives and so do we. Inside earth’s crust there are elements like iron, copper, silicon, sodium, magnesium, uranium, etc., etc. in the form of stable and not so stable compounds. We mine them, process them and use them, in various technologies, including nuclear energy for peaceful, and sometimes not so peaceful purposes. There are circulating molten solid currents, due to high pressures and temperatures, inside earth’s crust, which give rise to the magnetism inside and outside earth. We are quite familiar with the N–S poles of the giant magnet, in the core of the earth. It provided the source of navigation and discovery of unknown places on the surface of earth, for centuries, to some clever people. The N–S magnetic axis of the earth is not along the geographic N–S poles of the earth. The N–S magnetic axis of the earth is not fixed in time either. It reorients itself on daily, monthly and yearly basis. Why it does so? One scientific reason we know of is that the earth is bombarded by heavy mass of charged particles, on regular basis, from Sun. The mother nature’s magnetic field on the surface of earth which is of the order of only milli to micro Tesla, protects our body from harmful effects of the radiation, we receive on earth on daily basis from the surrounding universe. The radiation e.g., the solar radiation, provides us life on earth, as well, on daily basis. The magnetic field on the surface of earth, changes in a systematic manner, with distance. One can see magnetic field gradient present on the earth and it varies slowly, and is stronger in one direction than the other. Our body is exposed to it all the time. Is it shear coincidence that we use magnetic field gradients of the order mT/meter, close to present on earth, to produce MRI pictures in human body? May be. May be not. Some researchers have used earth’s field as the source of magnetic field to perform MRI experiments. This curiosity has produced some interesting results. That is how the development of the MRI technology we use today was stated half a century ago and is still evolving. This applies to every science-based technology we use.