shadron
Philosopher
- Joined
- Sep 2, 2005
- Messages
- 5,918
I was having a conversation with amb about Fermi's Paradox, and it occurred to me that it would be useful to be able to point to a list of requirements that are prerequisites for intelligent life evolving. I am attracted by the arguments for assuming that evolution of intelligent life is inevitable, but that necessarily sets bounds on the initial conditions, does it not? If so, then what are they?
Being an engineer and all fussy about requirements, I'd like to hear what sorts of cosmological, geological, chemical, biological and other conditions can be postulated for various steps in the process and for the final result. Indeed, is evolution necessarily inevitable as I've sort-of assumed it to be? I am aiming for a minimal list of independent requirements.
I can start off with a bunch of items that have occurred to me. Any additions, real numbers for values, arguments, etc are on-track for this thread.
- sufficient time in peace and quiet:
- two billion years or so of relative stability.
- a galaxy that is relatively quiet - not undergoing collision with another galaxy or other reason for undergoing star bursting, at least within a radius of, say, 10K light years.
- a similar radius within which a supernova event has not occurred (what radius?).
- being out of the "gun sight" of Wolfe-Rayet star's jet, or other aimed source of energy (gamma ray burster) to a somewhat higher radius.
- a star of the right mass to have been stable in the main sequence for the required time (hereinafter the "sun").
- a stable, near circular orbit around the sun, or, perhaps, around a planet that has such an orbit, such as Ganymede (yup, I'm a RAH worshipper).
- the elimination of planet busting debris (big enough to have stopped all life on he planet by melting it's entire surface).
- reducing remaining debris to sufficient rarity to make global catastrophe a muli-10 to 100 million year occurrence.
- enough planetary mass to have a long-lifetime central self-heating planetary core (see other requirements below about radioactive elements).
- enough turbulence to challenge life and occasionally to wipe the slate partially clean:
- occasional total and subtotal life threatening happenings, such as a large meteor collision, snowball earth, large volcanic events, some atmospheric disturbances.
- physical requirements:
- a moon large enough to raise respectable tides (requirement? Could be supplied, if needed, by the primary, I suppose).
- not so much time that the planet has become rotationally locked to the sun; a fast enough rotation to keep surface temperature within some limits.
- a physically large enough planet to have a core kept molten by radioactivity (since part of that requirement is for enough "insulation"). Also, large enough to promote tectonics to a degree sufficient to raise dry continents (I can sense my POV is interfering some with possibilities that I have no way of scoping here).
- temperature from internal and external sources and atmospheric pressure such as to keep water, to some large extent, in the liquid phase on the surface.
- chemical requirements:
- late enough in cosmological evolution to have a dust cloud with sufficient "dirt" (non-H, He atoms) to create solid planets of sufficient size.
- enough light elements (carbon, oxygen, nitrogen and other elements) to promote interesting organic chemistry. In particular, enough oxygen for surface oceans.
- enough heavy radioactive isotopes to fuel an interior furnace (see time requirement above) and a magnetic core.
- a planetary melting event sufficient to concentrate iron and the radioactive elements into the core, promoting a magnetic field around the planet and heat to drive tectonics and general chemistry. Secondarily, remove a large amount of the iron, inevitably a common substance, from the ability to soak up oxygen.
- biological requirements: (Is there anything here not covered above? Or is biology in some form inevitable given the above?)
- a sufficiently diverse planet (environmentally, resources) which promotes evolution.
- evolution of a monocellular entity, sufficiently prolific, whch can capture solar energy and use it to overcome the general chemically reducing conditions and charge tha gaseous atmosphere with a respectable fraction of elemental oxygen (inevitable?).
- intelligence requirements (likewise, anything additional here?)
Being an engineer and all fussy about requirements, I'd like to hear what sorts of cosmological, geological, chemical, biological and other conditions can be postulated for various steps in the process and for the final result. Indeed, is evolution necessarily inevitable as I've sort-of assumed it to be? I am aiming for a minimal list of independent requirements.
I can start off with a bunch of items that have occurred to me. Any additions, real numbers for values, arguments, etc are on-track for this thread.
- sufficient time in peace and quiet:
- two billion years or so of relative stability.
- a galaxy that is relatively quiet - not undergoing collision with another galaxy or other reason for undergoing star bursting, at least within a radius of, say, 10K light years.
- a similar radius within which a supernova event has not occurred (what radius?).
- being out of the "gun sight" of Wolfe-Rayet star's jet, or other aimed source of energy (gamma ray burster) to a somewhat higher radius.
- a star of the right mass to have been stable in the main sequence for the required time (hereinafter the "sun").
- a stable, near circular orbit around the sun, or, perhaps, around a planet that has such an orbit, such as Ganymede (yup, I'm a RAH worshipper).
- the elimination of planet busting debris (big enough to have stopped all life on he planet by melting it's entire surface).
- reducing remaining debris to sufficient rarity to make global catastrophe a muli-10 to 100 million year occurrence.
- enough planetary mass to have a long-lifetime central self-heating planetary core (see other requirements below about radioactive elements).
- enough turbulence to challenge life and occasionally to wipe the slate partially clean:
- occasional total and subtotal life threatening happenings, such as a large meteor collision, snowball earth, large volcanic events, some atmospheric disturbances.
- physical requirements:
- a moon large enough to raise respectable tides (requirement? Could be supplied, if needed, by the primary, I suppose).
- not so much time that the planet has become rotationally locked to the sun; a fast enough rotation to keep surface temperature within some limits.
- a physically large enough planet to have a core kept molten by radioactivity (since part of that requirement is for enough "insulation"). Also, large enough to promote tectonics to a degree sufficient to raise dry continents (I can sense my POV is interfering some with possibilities that I have no way of scoping here).
- temperature from internal and external sources and atmospheric pressure such as to keep water, to some large extent, in the liquid phase on the surface.
- chemical requirements:
- late enough in cosmological evolution to have a dust cloud with sufficient "dirt" (non-H, He atoms) to create solid planets of sufficient size.
- enough light elements (carbon, oxygen, nitrogen and other elements) to promote interesting organic chemistry. In particular, enough oxygen for surface oceans.
- enough heavy radioactive isotopes to fuel an interior furnace (see time requirement above) and a magnetic core.
- a planetary melting event sufficient to concentrate iron and the radioactive elements into the core, promoting a magnetic field around the planet and heat to drive tectonics and general chemistry. Secondarily, remove a large amount of the iron, inevitably a common substance, from the ability to soak up oxygen.
- biological requirements: (Is there anything here not covered above? Or is biology in some form inevitable given the above?)
- a sufficiently diverse planet (environmentally, resources) which promotes evolution.
- evolution of a monocellular entity, sufficiently prolific, whch can capture solar energy and use it to overcome the general chemically reducing conditions and charge tha gaseous atmosphere with a respectable fraction of elemental oxygen (inevitable?).
- intelligence requirements (likewise, anything additional here?)
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