What is Life?

My intention in this paper is to discuss and understand what life is, how it is, what are its basic elements, its essence. How can we know whether a process or thing is alive, or is merely a physical normal process? What differentiates a common physical system, a physical system that they say alive? We can recognize and list these characteristics? Whereas a living being as a system of study, it is of particular in relation to a physical non-living? A machine can often behave in ways similar to a living being, and yet it is known that a machine is not alive. There are real assembly lines in which their own machines or robots are used to build other robots. If you build a machine capable of reproducing itself, we could say that it became alive? If not, it would not be alive? What exactly distinguishes a living being? Of biology, it is a huge variety of living beings in the earth. We humans, mammals in general, birds, reptiles, fish, plants, the worms, bacteria, the plankton, fungi, the lichens, etc.. All are living. The largest to smallest, the simplest to the most complex, all exhibit characteristics that make them are classified as living beings. What are the characteristics of life that are shared by us, by worms, and even by plants by bacteria? Life is based on some kind of physical process and / or mathematical subject knowledge and study of the man? Or life is a metaphysical essence, and out any range of physical and mathematical laws, and beyond the reach of human understanding? The man will one day create artificial life? There may be other ways of life using other elements, different elements used by life on Earth? There may be life without water, oxygen? Could there be life in much higher temperatures (400 degrees, 1500 degrees), or much lower (-200 degrees), if the forms of life were based on different elements? What characteristics of life prevents it from there if it were not based on carbon, water and oxygen? Will could not have different ways of life, using different elements, living in different ways, of which we are familiar?

For these questions can be answered categorically, we need greater understanding of what life is. Until today no one ever proved that life could only be using the chemical elements known on Earth, the physico-chemical conditions known on Earth. I would not, a priori, to defend the existence of different forms of life. I am just saying that the universe is immense, with several planets and stars with the most diverse elements, with the most varied physico-chemical conditions of temperature, pressure, pH, etc.. Extremists. Even on Earth, many scientists are surprised by the discovery of bacteria that live at high depths, without light, feeding chemically of volcanoes in the depths of the ocean, others living in environments of high salinity, even in other environments with high pH, and others who live in extremely high temperatures, almost to the boiling point of water. How can we be sure that life can not exist under different conditions of the Earth? We may one day have that certainty? It is in search of answers that employ this day. I ask you, friend reader, to contribute with your comments and ideas about the pursuit of understanding, which in my opinion, is the most important problem throughout the history of mankind.

My definition of life is:

A dynamic process that manipulates matter, energy and information, to keep itself in time and space.

One of the implications of this definition is that to really understand what is life, one must have an accurate understanding of what is matter, energy, information, time and space. A difficult task, which however should be very rewarding.