| I've been a sci-fi fan since before Star Trek's | | | | successive generations of self-replicators into the |
| Captain Kirk split his first infinitive ("To boldly go ..") | | | | finite history of the earth, no matter how short |
| - but I have to doubt if we'll ever encounter any | | | | each one may be. Hence, if traced backwards, |
| of his intelligent alien friends or even any | | | | every evolutionary sequence must lead to a very |
| unintelligent alien microbes. | | | | first member - a self-replicating molecular entity |
| Some will assert that UFOs are a fact - but this | | | | that arose spontaneously (without the aid of |
| only seems to mean that objects have been | | | | natural selection, since there were no generations |
| seen flying that were not identified - hence, by | | | | prior to its existence) some 3000+ million years |
| definition, they are 'unidentified flying objects' - but | | | | ago. Indeed, every evolutionary sequence would |
| that does not make them alien spacecraft - just | | | | lead back to the very same first self-replicating |
| unexplained observations. Unfortunately, UFO data | | | | molecular entity, the common ancestor to all |
| is not very convincing of an alien connection - and | | | | subsequent life forms - unless more than one |
| if aliens are amongst us, they are keeping a very | | | | self-replicator arose independently. |
| low profile. | | | | So, for life to exist on any planet, anywhere in |
| One hears statements such as: "Given the billions | | | | the universe, a self-replicating molecular entity |
| of stars in the universe it is beyond reasonable | | | | would have to arise spontaneously, for Darwin-like |
| doubt that some sort of life exists in outer | | | | evolution to then follow. There is no "mechanism" |
| space"...and..."There's no question but that we live | | | | involved, that we may envisage having once |
| in an inhabited universe, that has life all over it" | | | | operated on the earth, and being equally likely to |
| Unfortunately, the above type of statements tell | | | | operate on any earth-like planet elsewhere in the |
| us nothing - and until such time as genuinely solid | | | | universe - since the occurrence of a fist |
| evidence arises regarding UFOs, aliens, close | | | | self-replicator is an entirely random event. |
| encounters and/or alien abductions, we can really | | | | My own estimates indicate that, even if we |
| only weigh up the likelihood of extra terrestrial life | | | | assume every single star in the universe has an |
| based on the data that is available to us. | | | | earth-like planet in orbit, and even if the first |
| It's certainly possible to make a plausible-sounding | | | | self-replicator was far simpler than the simplest |
| case for extra terrestrial life. For a start, we | | | | known cells, the probability of its spontaneous |
| know that life exists on earth and we infer that it | | | | origin on any earth-like planet is mind-bogglingly |
| once did not exist. So at some point in the 4 billion | | | | small. |
| year history of the earth, life arose. If it arose via | | | | Given our lack of knowledge about a potential |
| a natural mechanism, then we may infer that the | | | | first self-replicator, my assumptions about it for |
| same mechanism might occur on any earth-like | | | | the purpose of my calculation are, of necessity, |
| planet anywhere in the universe. Thus, alien life | | | | arbitrary - but I suggest that no reasonably |
| may seem plausible, even probable. | | | | realistic alternatives would justify the Drake-like |
| The 'Drake Equation' (Frank Drake 1961) goes | | | | assumption that life is highly likely to exist on any |
| beyond this - it seeks to makes an estimate of | | | | earth-like planet. |
| actual number of potential planets in the universe | | | | Indeed, there may well be millions of planets |
| with life. The calculation is based on various | | | | throughout the universe possessing the essentials |
| assumptions, the key one surely being that life is | | | | for life (water & even organic molecules) and |
| highly likely to exist on any given earth-like planet | | | | yet which are totally dead - because the |
| - and the equation then implies that that there | | | | self-replicating molecular entity, essential for |
| could be millions of planets throughout the | | | | subsequent evolution, did not spontaneously arise |
| universe with life - many life forms would be | | | | on any of them. The number of planets |
| intelligent - and many would be more | | | | supporting life may well be just one - this one. |
| technologically advanced than ourselves. | | | | However, on the plus side (!) - all those millions of |
| However, a problem with the key Drake | | | | planets will be unoccupied, unpolluted Edens, ideal |
| assumption arises as a direct consequence of | | | | for 'seeding' and for our future colonisation, |
| Darwin's Theory of Evolution. This theory asserts | | | | allowing us to spread throughout the universe |
| that the earth's organic complexity was produced | | | | unopposed by aliens. Future interplanetary wars |
| gradually, over a period of several billion years, by | | | | envisaged in alien movies such as "War of the |
| the action of natural selection, causing gradual | | | | Worlds", may well be between those who remain |
| changes over many successive generations of | | | | on the earth and the descendants of those |
| self-replicating organisms. | | | | who've made their home on other planets, |
| However, consider this - the number of | | | | subsequently seeking their independence from the |
| generations along any sequence of evolution must | | | | 'home world' - not a bad story line for a sci-fi film! |
| be finite - one cannot fit an infinite number of | | | | (C) Copyright 2009 Andy Chains (andychains. |