“Life seems to be orderly and lawful behavior of matter, not based exclusively on its tendency to go over from order to disorder, but based partly on existing order that is kept up”,
said Erwin Schrödinger in his book What Is Life, published first in 1944.
What is life?
Before attending Biophysics class, the question is weird for me. Not because it’s actually weird, for I haven’t surfed much on the knowledge it hides behind, but because it’s not the kind of question we would normally ask (especially outside of academic environment). It wasn’t normal because the society has built the definition of life very absolute and indisputable. If we try to find the definition of life, biology class taught us that living organisms have basic characteristic: eats, grows, reproduces, moves, breathes. But is it that simple? Do they apply to any living organism, say outside of our planet earth? It now looks like that definition is too specific with respect to earth’s living organism. But who knows that we are, or we are not alone in the universe? To identify the extra-terrestrial life, we need a more general, powerful definition of life that applies to every living organism that possibly exists in this universe.
With the comprehension that I have gained from the past classes of Biophysics, and by citing Erwin Schrödinger again as follows,
“Every process, event, happening—call it what you will; in a word, everything that is going on in nature means an increase of the entropy of the part of the world where it is going on. Thus a living organism continually increases its entropy—and thus tends to approach the dangerous state of maximum entropy, which is death”
I have my own definition of a living organism: an open system which actively prevents its tendency to reach thermodynamical equilibrium by keeping its entropy low at the optimum state. Why it’s an open system? Because it transfers in and out mass and energy throughout its life. Why it tends to reach thermodynamical equilibrium? As stated in the second law of thermodynamics. Why at optimum state? Because it can’t reach its entropy so low that it goes to zero as stated in the third law of thermodynamics, and it can’t reach it’s entropy so high (or maximum) because it will degrade/decay which means death.
So basically we have this key property that defines living organism, the entropy. If we want to try to detect life, we might want to measure its entropy and its change with respect to its surrounding, does it change? Does it increase or decrease?
But until now, absolute entropy still can’t be quantified. However, there is, of course, a way of measurement that represents the change of entropy in a living organism and is now being developed in many places in the world. Few idea that I can propose to detect life in the universe is by using electromagnetic field living organisms produce while alive, and by using another media, say virus, to see its response on a stimulus (the injection of the virus to its body). However, the virus-injection method seems a bit unnerving since there’s a big chance that the sample might be destroyed during the identification process.
Living organisms are made of atoms and molecules. The forces between atoms and molecules are largely electrical, just like those in non-living natural or man-made materials. The main difference between living organisms and materials is that the electrical force in the living organisms can be actively controlled. . The electrical force inside living organisms atoms is referred to as bioelectrical signal and the behavior as bioelectrodynamics. Under certain conditions, such as cell growth and mitosis, living cells may also transmit ultra-weak high-frequency electromagnetic waves and cells in culture might transmit and receive signals carried by EM radiation. We can detect life activities by disrupting the natural EM field of the living organism with another EM radiation like X-ray and g-rays. These forces and EM fields are likely to modify cellular behaviors by affecting metabolism, paracrine or autocrine factor secretion and gene expression among others . To detect its response to EM field disruption, we need to build bioelectrodynamics imaging instrument that can visualize electromagnetic field pattern disrupted by another EM radiation.
 S.-A. Zhou, “Bioelectrodynamics in Living Organisms,” 2005.
 C. S, “Molecular and Mechanical Bases of Focal Lipid Accumulation in Arterial wall, Progr. Biophys. Molecular Biol. 83,” pp. 131-151, 2003.