Why did the researchers doubt their own eyes? Why were the most vocal critics of the finding those who found it? Because the Universe and everything in it must abide by laws; laws that were elucidated by asking deep, probing questions to discover how the Universe works. They are powerfully explanatory. You had better make damn sure you know what you are talking about before you propose changing them because without them, it would be hopeless to discover anything about ourselves or our place in the Cosmos.
Life too must adhere to the laws of this Universe --chemical and physical-- and it’s those laws that place real limits on what’s possible and what’s impossible. For example; we know that life must be bounded; made of cells. How can we know this? Everything --the stars, planets, you-- are all made of the same chemical stuff. Life itself is the emerging property of complex chemistry. That chemistry must exist in sufficient concentrations to allow for reactions fast enough to interact and integrate with other reactions and to changing external conditions. Unbounded chemicals diffuse, lowering their local concentrations, which slows their rates of reactions until eventually they go so slow that they essentially stop. Life everywhere must be packed inside of cells.
We can also say something about what those cells will look like; for example, their size is not limitless. There can be no single celled organisms the size of cities. Giant blob-like creatures are not permitted in this Universe. Why? Life everywhere is an open system. Closed systems run in one direction only; towards equilibrium (2nd law of thermodynamics). Once there, chemical reactions stop. Living systems are constantly in a state of disequilibrium, powered by a constant inflow of new material and energy (negative entropy). This requires a boundary that is capable of being selectively permeable and has enough rate of exchange to keep the internal chemistry at disequilibrium. Since surface area increases at a slower rate than the volume, cells larger than a critical size would effectively be “closed”. The cellular material would be used up faster than it could be replaced and the system would eventually stop running. This fact explains why elephants and fruit flies are made of cells that are the same size. Large organisms are not made of large cells. Cell size is limited by law.
Given that life is chemistry of encoded genetic information, storing, replicating and passing on error-prone protein building instructions generation after generation encased in a selectively permeable membrane of relatively small size, and given that life's chemistry requires a liquid medium of water to run, we can begin to strategize where to look. Follow the water used to mean looking only in the Goldilocks zone of planetary systems --not to far from a Sun, not too close, just right for liquid water to be present. But now we know that liquid water can exist almost anywhere in a solar system. For example, the distant moons Europa and Enceladus, under the tidal forces of their large host planets (Jupiter and Saturn respectively), can generate enough geothermal energy to have liquid water at remote distances from the Sun.
Once we locate the water, what kind of life can we expect to find there? Worms? Jellyfish? Algae? People? Ironically, the start of life is the easiest to predict. The first cells were likely simple. Very similar to our bacteria. But from here, any resemblance to life on this planet is pure speculation. There is simply no way to predict beyond that first instance of life what will follow. Even the history of life on this planet is not repeatable. If you rolled back the clock to the first cell, and let Natural Selection play out all over again anew, none of the organisms you recognize now would reappear; including us. Natural Selection is not goal oriented. It does not direct the future course of change. It only acts on random variations that appear in a population. But those alien life forms would be running virtually identical chemistry.
The variations on life’s theme are near infinite, but they are just variations. On this planet alone there may have been as many as a billion different variations on that theme. A typical galaxy contains 100 billion suns, and there are over 100 billion galaxies. The number of other worlds is unknown, but our count keeps growing. It seems likely that planetary systems form frequently, very frequently. The actual number of worlds is far greater than any normal human comprehension. As we begin to reach out and explore new worlds, isn’t it possible that we could fly right past a planet with life and not even know it? Not likely.
A drive from coast to coast would surround you with different people, houses, communities, cities, etc. but you would have no trouble recognizing the public park, or the city square, or sports complex. The same holds true for trek through the cells of Earthly life and Alien life. Individual molecules may look different, but you would have no trouble recognizing the genetic storage facility or the molecular machines performing the biological activity. You would instantly recognize activities such as building the machine parts, genetic code replication, cell division and communication. The organism may look weird, but it’s inner workings would be very familiar. Don't expect a planet populated with sentient dinosaurs, or talking cockroaches. Those assemblages of cells are not likely to ever happen again, but do expect to be able to read their DNA.
-End of part 4
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