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by Dr Henry RichterMy past few articles on “Facing Reality About Life on Other Planets” have dealt with the necessary conditions for the existence of life on a planet—any planet. With the almost fanatical drive of the scientific community to find and prove the existence of life elsewhere in the universe, it is important to ponder the requirements for habitability. We’ve looked at the location in a galaxy, the location in a stellar system, the type of star required, and the physical characteristics of an exoplanet such as mass, rotation rate, atmosphere, magnetic field, water, a partial rocky surface and so on. This final article will consider the composition of planet: what materials and chemical building blocks must be present to sustain life.CarbonWe talked about life being based on carbon chemistry. A readily accessible and usable supply of carbon must be available in the planet’s chemical composition. Carbon itself, with its four bonds, is a remarkable element having a flexible bonding capability, giving it hundreds of thousands of possible molecular structures. The only other close element is silicon which can form a few somewhat complex molecules, but only a few compounds—nowhere near as many as carbon. Star Trek fantasies aside, astrobiologists generally admit that silicon-based life is just not possible. Carbon is known to be the basis of the acids, bases, enzymes, proteins, alcohols, esters, ethers, amino acids, and much more. A large number and variety of these are involved in building and maintaining living cells. So a ready supply of carbon is necessary. Where can it come from?The earth has usable carbon available in the atmosphere in the form of carbon dioxide gas, in carbonate rocks, as carbon dioxide dissolved in the oceans and lakes, and secondarily in plant tissues and juices (converted from atmospheric carbon dioxide). Both plants and animals are involved in the earth’s carbon cycle. Plants convert carbon dioxide gas into a wide variety of carbon compounds. These plants are consumed by animals, used as fuel, and the metabolic product being carbon dioxide. It’s a remarkable process!Other ElementsMany other elements are required for life in addition to carbon. These probably can’t be ranked in order of importance since all are essential. The next that comes to mind is calcium. This is used in bones and structural frameworks, and is an important signaling molecule. Calcium is also important in eggshells and seashells. Nitrogen is another essential element. Nitrogen compounds are needed for plant growth, and are in proteins. Phosphorus plays an important role in cell structure, cell activity, and the genetic code molecules, DNA and RNA. A variety of other elements, even some rare earths, are involved in life’s structures and processes. All you have to do is look at the label of a bottle of mineral supplements in a health food store to find selenium, magnesium, copper, and several others. We even see non-minerals such as iodine and bromine. Could we exist if any of these were absent from the earth, or weren’t readily accessible? I don’t know, but it raises the question whether complex life could exist elsewhere if any of these—or some combination of these elements—were missing. That brings us to the consideration of probability: what is the chance that all the required factors would exist simultaneously on an alien world?Probability: Running the NumbersLet’s look at the big picture now – the really big picture: the universe. It is estimated that there 100 billion galaxies (1011), each with 100 billion stars. That results in 1022 stars. Say that only one in 10,000 is a dwarf main sequence G2 star which, as we saw, is the most stable star for a habitable zone. That leaves 1018 possible host stars. That’s a quintillion—still a lot of stars! Let’s say that only one of 10,000 of these stars has a planet in the habitable zone; that now gives us 1014 candidate planets (a hundred trillion). Let’s further grant a generous 10% chance that any of the required features would “happen” to be present in any one planet (I think a 1% chance would even be high). All of these features have to be present simultaneously for there to be any chance of complex life existing. The factors below are listed in the documentary The Privileged Planet, mentioned earlier.Located within the galaxy habitable zone 10%A stable star with constant energy output 10%A planet formed within the habitable zone around the star 10%A planet in a stable orbit maintaining a steady distance from the star 10%Protected by gas giant planets in the solar system 10%A rotation speed of about 24 hours 10%A planet with a suitable atmosphere: oxygen-rich, depth, circulation 10%A planet with the appropriate mass 10%A planet with abundant water 10%A reasonable ratio of water to land mass 10%A crust capable of plate tectonics 10%A magnetic field within the proper strength range 10%A moon of the proper size, distance, and orbit around the planet 10%A readily available source of abundant carbon compounds 10%Trace elements of the right type and quantity 10%One could go on and on, adding more factors, but these are a few of the most essential features to consider. So let’s multiply that out: 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 × 0.1 = 10-15. This probability times 1014 candidate planets leaves 10-1 planets, less than one! If I had used a 1% probability instead of 10% (more reasonable), that would have reduced the overall probability to 10-30, yielding 10-16 habitable planets out of the hundred trillion candidate planets. This implies that even one habitable planet in the whole universe has less than one quadrillionth a chance of being found! With a probability this small, changing the order of magnitude of our estimates for the number of stars is not going to make much difference.Beyond just the requirements for habitability, could we expect undirected evolution to bring about a second form of complex life anything like the beauty and complexity of life we find here on Spacecraft Earth? Could life even start by chance, before evolution’s natural selection comes into play? I maintain that it could not have happened once by accidental means here, much less than a second time elsewhere!So, to wrap up, the outlook is bad for avid hunters of populated planets. There aren’t likely to be any other habitable planets in the universe. The only reasonable conclusion, given the evidence we have considered, is that our earth was specially and wonderfully made to be inhabited.Dr Henry Richter, a contributing science writer to Creation-Evolution Headlines, was a key player at NASA/JPL in the early days of the American space program. With a PhD in Chemistry, Physics and Electrical Engineering from Caltech), Dr Richter brings a perspective about science with the wisdom of years of personal involvement. His book America’s Leap Into Space: My Time at JPL and the First Explorer Satellites (2015), chronicles the beginnings of the space program based on his own records and careful research into rare NASA documents, providing unequaled glimpses into events and personnel in the early days of rocketry that only an insider can give. His next book, Spacecraft Earth: A Guide for Passengers, is due out later in 2017. For more about Dr Richter, see his Author Profile.(Visited 448 times, 1 visits today)FacebookTwitterPinterestSave分享0
Share Facebook Twitter Google + LinkedIn Pinterest Zach Profit, Van Wert Co.Since last Monday we’ve had 7.5 inches of rain. Every day since then we have gotten a pretty good shot of rain and there is a 50% chance tomorrow and an 80% chance on Wednesday. We got hammered pretty good and then there was an EF0 tornado that went through about a quarter mile east of our farm. It almost wiped out a new house that I bought.I bought the house at 3 on Friday and signed the paperwork and at 6:55 that night a tornado went through the north side of the lot. It threw a branch at one side of the house but it didn’t really hurt much. There were a bunch of limbs down but it messed up some corn. The corn was flat. There was green snap but since we’d had all that rain, the wind just pushed most of the plants over.The corn has goosenecked and stood back up and it is looking better. Our neighbors took it a little harder than we did. Their corn was maybe shoulder high and after that it was maybe two feet tall. We had 5 or 6 acres of damage and maybe total there were 55 or 60 acres that got wind damage. I think there will be corn there but it may be kind of a bugger to combine this fall.An EF0 tornado cause damage in a small area, including the newly purchased Profit home with the red buildings.The National Weather Service was at my new house all day Saturday. Just two or three miles away it was barely windy enough to move the leaves. We didn’t have a tornado warning or severe storm warning or anything. It looked like it tap danced in our field. It moved northwest and most tornados move to the northeast. The whole low-pressure system we had last week was counter clockwise rotation. It was wild. We were lucky.In the wetter areas the beans are a little yellow. I think they will bounce back pretty quickly. Last week we were one more big rain away from having a mess and we never got that next big rain. The ditch banks never came out but they were full to the brim. If we’d have caught one more big rain the ditches would’ve been out and we’d still be getting rid of the water. Most of the surface water is gone and most of the outlets are running about half full.Wheat around here is standing good. There could be some disease pressure. We are wet right now, too wet to get a combine out there. If we don’t get more rain they could maybe get out there late this week.For the rest of this week’s reports, click here.
Days after patwaris struck work for three days in Madhya Pradesh, tehsildars across the State have gone on mass leave for the same duration starting Thursday demanding pending promotions, better wages and sufficient computers in offices. Tehsildars, under the banner of the Madhya Pradesh Revenue Officers Union, sat on dharnas in 52 districts of the State on Wednesday and Thursday. “To call it a strike won’t be appropriate. We have gone on mass leave for three days. We’ll meet the Chief Minister, and if he doesn’t accept our demands, will go on strike,” said Jitendra Tiwari, executive president of the union. The government must clear pending promotions it had withheld for a while now, he said. “Moreover, salaries of tehsildars and naib tehsildars are too less and need to be increased according to Grade A norms,” he added. Both patwaris and tehsildars had a major role to play in flood estimation, extending relief to farmers and distributing aid. Preliminary estimates pegged damage at more than ₹16,000 crore. And recently, Chief Minister Kamal Nath called on Prime Minister Narendra Modi requesting an immediate aid of ₹9,000 crore and a resurvey by a Central team. ‘Major role’“We have a major role in flood damage estimation and that’s why we pushed this agitation back. The estimation process is almost complete,” clarified Mr. Tiwari. The government was ensuring no work was affected due to the mass leave, Manish Rastogi, Principal Secretary, Revenue Department, told The Hindu.“Even when the patwaris went on strike, the relief work wasn’t affected as most of it had been completed before it,” he said. “Obviously, the overall progress was affected, but relief was still given to farmers.” Patwari thawPatwaris called off their strike last Sunday after meeting Revenue Minister Govind Singh Rajput. Earlier, Higher Education Minister Jitu Patwari had called patwaris corrupt, which had led to the agitation demanding a public apology from him. This had spooked both farmers and the government alike, triggering fears that the strike may hobble the relief process.