posted by RRRGroup at
Monday, April 06, 2015
Rich,The arxiv paper can be found here: http://arxiv.org/pdf/1503.07804v1.pdf It is an extrapolation of Kleiber’s law [body size is proportional to body mass] with a dash of the Drake equation... and some whopping assumptions. The paper concludes: "Unless we are alone in the Universe, our planet is likely to be one which produces observers at a higher rate than most other inhabited planets. This may be accomplished by having a relatively large population, and low individual life expectancy. The magnitude of this observational bias increases exponentially with the variance of population sizes across different civilizations. ...Any variable which correlates with population size will also be subject to observational bias. By adopting a simple model where the mean population density is insensitive to planet size, we find that an inhabited planet selected at random can be expected to have a radius of r<1.2 earth radii Even if we are the only intelligent species in the Universe, this does not imply that the Earth is a representative sample among planets which host life. Larger biospheres will host a wider range of species and a greater number of individual life-forms. For these reasons it seems highly likely that larger biospheres possess a greater probability of producing an intelligent species. This reinforces our conclusion that most life-bearing planets are smaller than the Earth. ... As a result, we should expect humans to be physically smaller than most other advanced species. By marginalizing over a feasible range of standard deviations, we conclude that most species are expected to exceed 300kg in body mass. The median body mass is similar to that of a polar bear.The problem here is the assumption that all of those smaller planets which must exist *must* have larger biospheres and *must* lead to the conclusion that the majority of all intelligent species are larger than human kind. I'd say that is seriously unproven speculation. While the paper accounts for the size of the planet and of the species [lower planetary mass might lead to a physically larger species], it fails to account for the size of the species "useable habitat". One of the nasty habits of biospheres is that larger predators get rid of smaller competitors. Larger predators kill smaller ones. The only reason the precursors of humans survived the large predators to rule this planet is we kept out of their way until nature [or humans] eliminated them.Habitat can have strong effects on a species. One could say that, based upon this paper, that one should assume that the only actual intelligent species on this planet are the elephants and the whales. Yet neither has developed tools or written language which seem to be one of the hallmarks of an intelligent and potentially "interstellar" or "space-faring" species.Read the paper if you want the specifics of the author's speculations. Your mileage may vary.
By gishzida, at Monday, April 06, 2015
Thank you GZ:Interesting.Your "One of the nasty habits of biospheres is that larger predators get rid of smaller competitors.Larger predators kill smaller ones." allows for speculation about whether or not the so-called "greys" of UFO lore deal with a diversity that could be hostile, or are UFOs piloted by a culture or species that is uniform across their planet (or system)?RR
By RRRGroup, at Monday, April 06, 2015
I highly recommend the book "What does a Martian look like" by Jack Cohen and Ian StewartWith this book influencing me, I find it very hard to accept the "grey" form
By Stephen Jackson, at Monday, April 06, 2015
In 1752, Voltaire wrote about giant aliens visiting Earth.http://en.wikipedia.org/wiki/Microm%C3%A9gas
By Terry the Censor, at Monday, April 06, 2015
Rich,You said: "Larger predators kill smaller ones...."Only if the smaller ones can be caught. ;-)If the smaller creature is clever enough they can learn to hunt the predator. We fit that smaller niche compared to the Ursine and Feline predators of our world. We've never been direct competitors to the Cetaceans. Now for a bit of a scary thought: Humans are approximately "bear sized" or "big cat" sized when compared to our little friends "the Greys". For all we know the Greys are trying to write a cook book on the preparation of humans as food [See Rod Serling's adaptation of a Damon Knight short story "To Serve Man"].One other thing to not actually evaluated in the arxiv paper is how, while planetary size might make for larger aliens, a trade off might exist which would logically require a much lower population density since they have to "graze" a larger environmental range to get a larger body mass.Want to read actual science on the subject? Read Kenneth Heuer's "Men of Other Planets" originally published in 1951. It is a "popular" but scientific take on the effects of planetary environments on the evolution of life forms. "Habitable Planets For Man" by Stephen H. Dole Free, legal PDF: http://www.rand.org/pubs/commercial_books/CB179-1.html This book was a RAND publication written for the Air Force back in the early 60's... It outlines the planetary parameters for humans to live on other "earth-like" planets without 'equipment'. Now given that our "little Grey Friends" seem to be "mostly at home" visiting us, the parameters in Dole's book tells us what their world [if it exists] might be like... though one of the parameters might be at an extreme as I seem to recall reading somewhere the claim that they had some problems with breathing our air. Dole's info allows us to narrow the planetary environment [and star type] they come from... and "marvel" that the Grey's environmental parameters are so close to ours... which is to say either there are a lot of earth-like worlds out there, or "our type" of oxygen breathing, bipedal creature is common... or both... We won't actually know until we have a way to remotely discover and "explore" exoplanets where the radius is <1.2 Earth radii.I am not particularly of the belief that "the Greys" [or any other alien visitors] actually exist as described, but if they do, it seems they they are not our friends. Why? Given the repeatedly bizarre encounters with whatever the intelligence is, it seems their behavior is designed to confuse and deny their existence. I'd say that is really unfriendly for alleged "space brothers" or an "advance species". If they were actually advanced and "friendly" they would never visit and risk destroying our "native culture" [Roddenberry's idea of the Prime Directive]. Instead they keep popping up. Maybe maybe they are smaller scavengers that like to hunt "larger prey"... maybe they do want to "serve man".regards,
By gishzida, at Tuesday, April 07, 2015
Interesting post Rich. Hi gishzida. You have a blog or something like that?
By Don Maor, at Wednesday, April 08, 2015
@Don:No, I don't have a blog. I'd only get myself in trouble if I did... The last time that happened I upset some friends and potential friends... So now I keep a low profile and pipe in when I see something I have some knowledge... Scientific speculation on planets and "life forms" happens to be one of those things I have an interest. Otherwise I leave Ufology to those who claim to have all of the answers.
By gishzida, at Thursday, April 09, 2015
Hi, gishzida.I would say that the paper by Simpson is purely statistical, wih no basis on physical , biological, or biomechanical constraints, except for the Kleiber's law.Therefore, the result by Simpson is rubbish.Regarding Kleibers law, it is not exactly what you described here. Kleiber's law is the dependence of the metabolic rate Q (W) on body mass M (kg), which seems to scale as Q--M^0.75. Interestingly, nobody knows well why this is so.
By Don Maor, at Thursday, April 09, 2015
Don, My bad for over-simplifying Kleiber's Law which, by the way, some folks still seem to be arguing about its validity and what allometric formulas are valid. As a 'rule of thumb' works very well. It is one of a number of scaling laws which effect the properties, capabilities, and appearance of any given species.For example we don't see bug the size of house because as the surface area of the creature grows so does the overall weight and so does the required strength of the materials needed to support the creature. At some point the weight of the body exceeds the strength of the materials needed to support it. On the other hand as you scale down a creature it not only makes the surface area smaller... but so does the surface area of the brain... meaning less neurons to make neural connections... We don't know what the limit is for brain size to allow for intelligence but I doubt a "cat or dog" sized creature could ever develop human level intelligence... much less a star drive. The arxiv paper was making the rather rash assumption that a creature could be more "massive" if the gravity were lower... hence the home planet is smaller but failed to account for the size of the planet as "grazing" surface area. I suspect the author had succumbed to the need to "publish or perish".If one were to find a Mars sized planet with the same water / land ratio [Not likely for various reasons] it would have less than 1/3 the land area of earth... meaning the biosphere and possible population would be commiserately smaller than that of Earth. Not to feed the "true believers" of ETH, but one of the things that might be implied by Kleiber's Law when taking into account planetary mass, is that LGMs might come from slightly more massive planets than the Earth while the "tall Nordics" might come from a place with slightly lower gravity.Thanks for the clarification.regards!
gishzida said:"The arxiv paper was making the rather rash assumption that a creature could be more "massive" if the gravity were lower... hence the home planet is smaller but failed to account for the size of the planet as "grazing" surface area. I suspect the author had succumbed to the need to "publish or perish"."I am not really sure of that. There is a paragraph in which the autor explicitly stated that he did NOT consider gravity with respect to body size.I am now even considering the possibility that even the purely statistical argumentation is flawed.Regards,
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