From Wikipedia:
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.
N = R* • fp • ne • fl • fi • fc • L
- R* = the average rate of star formation in our Milky Way galaxy.
- fp = the fraction of those stars that have planets.
- ne = the average number of planets that can potentially support life per star that has planets.
- fl = the fraction of planets that could support life that actually develop life at some point.
- fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations).
- fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
- L = the length of time for which such civilizations release detectable signals into space.
The Drake Equation is effectively a box of conjectures shaken periodically to produce a new estimate of the likelihood of finding exo-intelligent life. It’s like an utterly fanciful Bayesian attempt at predicting the unpredictable. Take one sample, Earth, and from it, and our observable views and knowledge of space, derive a probability that humanity will find intelligent life outside of our solar system.
There’s nothing really scientific about it even though it tries to use some basis to remain accurate. If an accurate conjecture is even a real thing… But that’s why it’s so alluring. ANYONE can play with Drake’s Equation and come up with a number that means something to them. And your number will be just as ‘right’ as anyone else’s!
With this in mind I now present a list of somewhat appropriate concepts that may or may not influence one or more of the Drake Equation parameters. In a generally descending order of importance:
- Liquid water.
- Goldilocks location.
- A heliosphere.
- Distance from the galactic center,
(outside most bursts of intense radiation – gamma rays, and avoidance of intense space weather which may affect agriculture). - A molten iron core planet producing a planet protecting magnetosphere.
- The existence of asteroid and comet belts (Kuiper Belt, Oort Cloud) which would both deliver supplemental elements as well as disrupt stagnant evolution.
- Volcanism, plate tectonics and the recycling of minerals and elements through volcanism, continental ridges
(CO2, sulfur, calcium, all need to be recycled). - Earth tilt. Seasons contributed to the stress need to spur life into intelligence.
- The Moon. A moon of sufficient size and limited distance to stabilize the tilt of Earth’s axis and to adsorb some portion of the asteroid/comet impacts.
- Continental configuration. Island states would not produce intelligent life. Milankovitch cycles, the northern hemisphere’s influence on heating and cooling cycles.
- Oceans filtered toxin free by biotic life over 3.5 billion years and the generation of oxygen by this life.
- The generation of ozone, or its equivalent, that shields DNA from constant mutation.
- Biotic life had an impact on the evolution of the Earth’s crust and hence an influence on higher life forms.
- Star death required to produce higher atomic weight elements necessary for life processes. Universally young stars could not have harbored life on their planets due to low molecular weight of elements.
- Although our solar system is in the process of emerging from the Local Bubble, the sun’s trajectory suggests that it will probably not encounter a large, dense cloud for at least several more million years. The consequences of such an encounter for the earth’s climate are unclear; however, one wonders whether it is a coincidence that Homo sapiens appeared while the sun was traversing a region of space virtually devoid of interstellar matter.
- Disease. Humanity, and higher forms of life in general, must have survived disease. Disease has killed more human life than all the wars, religions and genocides put together.
- Strong presence of nuclear reactive materials in Earth crust that may have contributed to the spawning of life.
- 3.5 billion years of hydrocarbon concentration perfectly delivered at just the right time to drive humanity over the population threshold that sparked the industrial revolution.
- The expedient use and transition from fossil fuels to non-environmental impacting technologies (to avoid calamitous climate change.)
- Miscellaneous items of lesser importance:
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- Metal: easy access to metals of many types must be available for advanced alien life (industry, electronics, astro-exploration).
- Guano: bird droppings strangely enough has made an enormous impact on the development of humanity.
- Rubber: The existence of a rubber tree and the textile extracted from it also had an immense impact on the development of humanity.
Random points supporting the theory that life is unique:
- Change. Change is probably one of the primary drivers of higher life forms. Many of the above points that would influence the evolution of life on a planet are change based. Without change, often drastic change (chemical, climate, temperature, radiative, water currents, minor planet tilt aberrations) life would get ‘stuck’ in static ecological configurations. Externally induced change spurs evolution.
But too much change would also be detrimental to the evolution of intelligent life. Change must be of just the right amount, just enough asteroid impacts, just enough volcanism, just enough galactic radiation, just enough coronal mass ejection, just enough planetary tilt, just enough continental drift and distribution. Just enough to provoke limited change but not too much to continuously be wiping the evolutionary slate clean. - Earth has been emitting life signs spectroscopically for 3.5 billion years. If alien intelligences had been looking, they would have found this planet by now.
https://anonymole.wordpress.com/2014/05/09/intelligent-alien-life-does-not-exist/ - FermiParadox-Chopra-GaiaFilter
Anonymole - apocryphal agitators 
Drake Equation: R * fP * nE * fL * fI * fC * L = N
Rate of how fast stars are formed.
Fraction of stars that have planets.
Number of of planets per star that actually develop life.
Fraction of those planets that develop civilizations.
Fraction of civilizations that could be detected.
Length of time those civilizations emit detectable signals.
Number of civilizations in the Galaxy that we can detect.
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https://www.livescience.com/64825-why-earth-has-an-atmosphere.html
QUOTE:
Earth’s atmosphere is enormous, so far reaching that it even affects the International Space Station’s route. But how did this giant gaseous envelope form?
That is, why does Earth have an atmosphere?
In short, our atmosphere is here because of gravity. When Earth formed, about 4.5 billion years ago, the molten planet barely had an atmosphere. But as the world cooled, its atmosphere formed, largely from gases spewed out of volcanoes, according to the Smithsonian Environmental Research Center (SERC). This ancient atmosphere was very different from today’s; it had hydrogen sulfide, methane and 10 to 200 times as much carbon dioxide as the modern atmosphere does, according to SERC. [Infographic: Earth’s Atmosphere Top to Bottom]
“We believe the Earth started out with an atmosphere a bit like [that of] Venus, with nitrogen, carbon dioxide, maybe methane,” said Jeremy Frey, a professor of physical chemistry at the University of Southampton in the United Kingdom. “Life then began somehow, almost certainly in the bottom of an ocean somewhere.”
After around 3 billion years, the photosynthetic system evolved, meaning that single-celled organisms used the sun’s energy to turn molecules of carbon dioxide and water into sugar and oxygen gas. This dramatically increased oxygen levels, Frey told Live Science. “And that is the biggest pollution event, you might say, that life has ever done to anything, because it slowly transformed the planet,” he said.
Nowadays, Earth’s atmosphere consists of approximately 80 percent nitrogen and 20 percent oxygen, Frey said. That atmosphere is also home to argon, carbon dioxide, water vapor and numerous other gases, according to the National Center for Atmospheric Research (NCAR).
It’s a good thing these gases are there. Our atmosphere protects the Earth from the harsh rays of the sun and reduces temperature extremes, acting like a duvet wrapped around the planet. Meanwhile, the greenhouse effect means that energy from the sun that reaches Earth gets waylaid in the atmosphere, absorbed and released by greenhouse gases, according to the NCAR. There are several different types of greenhouse gases; the major ones are carbon dioxide, water vapor, methane and nitrous oxide. Without the greenhouse effect, Earth’s temperature would be below freezing.
However, today, greenhouse gases are out of control. As humans release more carbon dioxide into the atmosphere, Earth’s greenhouse effect gets stronger, according to NCAR. In turn, the planet’s climate gets warmer.
Intriguingly, no other planet in the universe has an atmosphere like Earth’s. Mars and Venus have atmospheres, but they cannot support life (or, at least, not Earth-like life), because they don’t have enough oxygen. Indeed, Venus’ atmosphere is mainly carbon dioxide with clouds of sulfuric acid, the ‘air’ is so thick and hot that no human could breathe there. According to NASA, the thick carbon dioxide atmosphere of Venus traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system. Surface temperatures there are hot enough to melt lead.
“The fact that Earth has an atmosphere is extremely unusual in respect of the planets in the solar system, in that it’s very different from any of the other planets,” Frey said. For example, the pressure of Venus is about 90 atmospheres, the equivalent to diving 3,000 feet (914 meters) beneath the ocean on Earth. “The original Russian spaceships that went there [to Venus] just recorded for a few seconds and then got crushed,” Frey said. “Nobody ever really understood how hot it was.”
So, Earth’s atmosphere is life — and without it, life as we know it wouldn’t exist. “Earth needed the right atmosphere [for life] to get started,” Frey said. “It has created that atmosphere, and it has created circumstances to live in that atmosphere. The atmosphere is a totally integral part of the biological system.”
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Click to access ChopraLineweaver2016.pdf
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Currently, the simplest definition of life is based on 7 requirements. Life:
1 Is composed of cells,
2 Responds to stimuli,
3 Reproduces,
4 Has a metabolism and respires,
5 Passes traits on to offspring,
6 Grows and changes,
7 Maintains homeostasis.
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NASA Sounding Rocket Successfully Launches into Alaskan Night
Credits: NASA/Jamie Adkins
An experiment to measure nitric oxide in the polar sky was successfully launched on a NASA sounding rocket at 8:45 a.m. EST, Jan. 27, 2017, from the Poker Flat Research Range in Alaska.
The Polar Night Nitric Oxide experiment or PolarNOx was launched on a Black Brant IX sounding rocket to an altitude of nearly 176 miles. Preliminary information shows that good data was collected.
Phil Eberspeaker, Chief of the NASA Sounding Rocket Program Office, said, “The sounding rocket, science and range team worked through previous payload and ground system issues to launch this payload, not to mention the extremely cold weather (as low as -50 degrees). The team did a great job to conduct a successful launch.”
Scott Bailey, the principal investigator for PolarNOx from Virginia Tech in Blacksburg, said, “The rocket team did a great job of pointing us at the star and our spectrograph saw it clearly throughout the flight. We got plenty of data to work through.”
Bailey said, “The aurora creates nitric oxide, but in the polar night there is no significant process for destroying the nitric oxide. We believe it builds up to large concentrations. The purpose of our rocket is to measure the abundance and altitude of peak abundance for the nitric oxide.”
“Nitric oxide under appropriate conditions can be transported to the stratosphere where it will catalytically destroy ozone,” Bailey said. Those changes in ozone can lead to changes in stratospheric temperature and wind and may even impact the circulation at Earth’s surface.
PolarNox was the first of five rockets scheduled for launch between January and March from the Poker Flat Research Range operated by the University of Alaska, Fairbanks.
PolarNOX will be followed with the launch of two additional missions that will study the interaction of the solar wind, the magnetosphere, Earth’s upper atmosphere and the structure of the resulting aurora. The magnetosphere is the region of Earth’s magnetic field where solar energy is stored and processed. The release of this energy drives aurora.
The launch window for both missions, which include 2 sounding rockets each, is Feb. 13 through March 3.
The Polar Night Nitric Oxide or PolarNOx experiment from Virginia Tech is launched aboard a NASA Black Brant IX sounding rocket at 8:45 a.m. EST, Jan. 27, from the Poker Flat Research Range in Alaska. PolarNOx is measuring nitric oxide in the polar night sky. Nitric oxide in the polar night sky is created by auroras. Under appropriate conditions it can be transported to the stratosphere where it may destroy ozone resulting in possible changes in stratospheric temperature and wind and may even impact the circulation at Earth’s surface.
Credits: NASA/Jamie Adkins
The five launches from Alaska are supported through NASA’s Sounding Rocket Program at the agency’s Wallops Flight Facility at Wallops Island, Virginia, which is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. NASA’s Heliophysics Division manages the sounding-rocket program for the agency.
Keith Koehler
Wallops Flight Facility, Virginia
Last Updated: Jan. 27, 2017
Editor: Patrick Black
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http://theconversation.com/why-havent-we-encountered-aliens-yet-the-answer-could-be-climate-change-27741
Intense climate change may limit the time windows that life can develop within.
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