**Professor Pranab kumar Bhattacharya- MD(cal) FIC Path(Ind), Professor and Head Department of Pathology Calcutta school of Tropical Medicine, Incharge DCP and DLT of WBUHS; Ex professor and HOD Pathology RIO calcutta and WBUHS &Ex Professor of department of Pathology, Institute of Post Graduate Medical Education & Research,244 AJC Bose Road, Kolkata-20, West Bengal, India* Miss Upasana Bhattacharya- Student, Mahamayatala, Garia, kol-84, only daughter of Prof.PK Bhattacharya** Mr. Rupak Bhattacharya-Bsc(cal), Msc(JU), 7/51 Purbapalli, Sodepur, Dist 24 Parganas(north) Kol-110,West Bengal, India ***Mr.Ritwik Bhattacharya B.com(cal), Miss Rupsa Bhattacharya Student http://www.bautforum.com/showthread.php/100276-Detecting-alien-radio-TV-signals?p=1676453#post1676453 Mr Somayak Bhattacharya MBA of residence7/51 Purbapalli, Sodepur, Dist 24 parganas(north) ,Kolkata-110,WestBengal, India******** Mrs. Dalia Mukherjee BA(hons) Cal, Swamiji Road, South Habra, 24 Parganas(north) West Bengal, India**** Miss Aindrila Mukherjee-Student , Mr Debasis Mukherjee BSc(cal) of Residence Swamiji Road, South Habra, 24 Parganas(north), West Bengal, Indi
* Large planetary family to absorb debris
* Iron core to generate magnetosphere
* Planet massive enough to retain its atmosphere
* Collision with planetoids to create voids in tectonic plates and large moon. [Please see LINK
* Large moon to stabilize rotation because without large moon the rotational axis of the planet will be unstable
* Plate tectonic activity
* Water[ocean] by cometary’s seeding
* Recent nearby nova to clear out interstellar dust
* Time between large impactors for life
* Main sequence star
* Adequate age for life to evolve
* Orbit within ' the habitable zone'
* Avoid close orbit and being tidally locked to star
* Not within a dense star cluster
* Sudden, occasional environmental/ecological changes to encourage evolution
1. If larger: advanced life functions would proceed too quickly.
2. If smaller: advanced life functions would proceed too slowly
N = R* x fp x ne x fl x fi x fc x L Where, N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable., R* =The rate of formation of stars suitable for the development of intelligent life. ,fp = The fraction of those stars with planetary systems. ne = The number of planets, per solar system, with an environment suitable for life. fl = The fraction of suitable planets on which life actually appears.fi = The fraction of life bearing planets on which intelligent life emerges. fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space. L = The length of time such civilizations release detectable signals into space. Drake himself estimates the final number of communicating civilisations in the galaxy to be about 10,000. As per Drake, we may calculate, for example- 0.333333333 7,300,613.497 planets may be containing any kind of life, intelligent or not. 0.333333333 973415.1329 "Jurassic" worlds or any other whose most intelligent species is sub-sentient. 0.333333333 12.16768916 planets whose most intelligent species is within (but not over) 5000 years of current Western World technological development i.e. ~ 12 worlds with 'planets whose most intelligent species is within [where life evolved without artificial intervention] . So planets with 'advanced technical civilizations are quite rare, if we consider civilizations not more than 5000 years old and If the average age of a civilization is a million years, that increases the number of intelligent species civilizations to 2400, In 2001, For the first time, the researchers estimated how many planets might lie in the "habitable zone" around stars, where water is liquid and photosynthesis possible. The results suggest that an inhabited Earth-like planet could be as little as a few hundred light years away. So it is obvious that within the limits of our existing technology, any practical search for distant intelligent life must necessarily be a search for some manifestation of a distant technology, The National Research Council of US has emphasized the relevance and importance of searching for evidence of the electromagnetic signature of distant civilizations.
By contrast, the red dwarf (M-class) stars will be around for billions of years, much more than enough time for life to form. Furthermore, they do not emit as much ionizing radiation as even our own sun (G-Class), another factor favoring a life-friendly environment. Unfortunately, the cooler the star, the narrower its life zone. I personally interpret this fact to mean that a red star’s HZ will be less likely to contain a planet of any sort, let alone one with other preconditions necessary for life to have a chance on it. Even if the red sun’s HZ does have a planet with the appropriate gravity, atmospheric and other characteristics, odds are fairly high that the planet will suffer from “rotation lock” (one face always facing the star). This means one side will be in eternal day or close to it (thus rendering it too hot) and one side will be in eternal night (rendering it too cold). However, there is still at least some chance other mitigating factors will come to play on such a planet (the hot spot over the planet may create atmospheric convection that creates winds, thus spreading heat more evenly over the planet). Obviously, a rotationally-locked planet’s twilight zone could offer a happy medium in which life, and even intelligence can flourish in theory. However, as I will discuss later, such a planet will have a much more difficult time developing a sustainable high technology civilization, and even a high-end pre-industrial civilization. G (yellow), K (orange), and low-level white stars as places favorable for advanced civilization to arise. If we include all G and K stars, plus about 1/3 of all F stars, these stars are about 22% of all stars in the galaxy ( Wikipedia). If M-class (red) stars - 78% of all stars - permit HZ planets without a rotation lock, then perhaps another 10 % of all stars (the hotter M-class ones) can be added to (though I admit this number is rather arbitrary). So we can say that as many as 33% of all stars could support a technical civilization, given other necessary planetary conditions listed above. Such stars that are the appropriate age - If you are content with finding significant life in any form, you will likely find it around planets between two and five billion years old. This is certainly long enough for life to form an Oxygen atmosphere (strong evidence of life), though not necessarily sentient life. Hopefully, by 2016-2020 the Terrestrial Planet Finder (TPF) project will finally give the answers we all want--where there are rocky crust planets orbiting around G to K class stars within 200-300 light years of Earth. The TPF mission will survey number of Earth-sized planets in habitable zone orbits in the galaxy
It is possible that the variety which life on Earth utilizes may predominate on many planets; it might be the most suitable type for living creatures and will be selected by evolution on a biochemical level. Even if this is true (and I don't think we can be sure yet) there are two mirror-image forms of DNA which are possible; we never encounter the mirror image L-DNA in nature as far as I know(as opposed to zDNA, which is completely different in form) but it could occur on other worlds. Alien life might not have DNA like earthlings Prof Hawking warned: "Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance."
Secondly, the development of eukaryotes was arguably the greatest leap in evolution since the origin of the first self-replicating cell; certainly not within the gradualism camp since it resulted from a series of rare cell-fusions of prokaryotic cells. Once again, we might ask of what relevance to the timing of the origin of life was this serendipitous event? It is wrong to place the origin of the prokaryotic cell at 3.5 Gigayears ago. Although we have evidence of the existence of prokaryotes at that time we also have evidence that their phylogeny, on Earth, runs much deeper from 3.8 bya (Mojzsis, et al., 1996; Pflug, 1978; Rosing, 1999, Rosing and Frei, 2004) to 4.2 bya (Nemchin et al. 2008; O'Neil et al. 2008). Prokaryotic life appeared on Earth shortly after life became possible on this planet (Joseph and Schild 2010). It we accept the Sharov's (2010) contentions, they may well have existed 10 billion years ago.
In Our view all life-forms we might find in the outer solar system will share the genetic codes may be familiar to us. Any experimentation with alternative genetic systems in primordial cells would have been snuffed out by the development of the RNA world (Gilbert, 1986), which in turn was snuffed out (with the possible exception of some RNA viruses) by the DNA world. The important question remaining is whether both Prokaryotes and Eukaryotes are represented among these life-forms.