3. Origin of Life
1. Concept of life
Once we accept Earth as the one and only habitable planet in the Solar System, what arguments have we to say that? In many lectures people asked me: Life is only as we know it, but could it be different kinds of life? So we must know what life word means before answer these questions.
If I am using a microscope and see a little black thing, first I need to know if it is alive or dead. And if, after hours of watching it, the black thing doesn’t move, the logical answer is that it is not alive. Why? Because life involves activity. And if a living being is a material being, and has activity inside its body, certainly he needs to spend energy. Where he could obtain that energy? And it obtains it from its environment. Therefore, a living being must be a material being, with activity and capable of obtain energy from its world. It must use the energy for growing up and for reproduce itself. After that, we can consider the rest of questions about life.
A physicist knows about the different types of matter. First, we have 92 elements from the periodic table, all of them stable ones. We can start with an element of only one particle, its nucleus, the hydrogen, and finished with the uranium, which has 92 positive particles, but a number of 235 particles inside its nucleus. And there cannot be half-charges, so we only have the elements obtained by one, two, three, four, five or 92 charges. Also, we know about elements and their properties, and we know, as example, that helium doesn’t reacts against nothing. So, helium is not suitable for life. Other elements, as gold or platinum, have similar properties, so they are also useless for life.