This group includes the word 'life' in its title, and the word is included in virtually every philosophical/theological discussion everywhere in the world. Generally speaking, thumpers are apt to mean humanity when they refer to it, while those of a more scientific bent usually mean any carbon-based self-reproducing organism.

However we define it, we rely on our limited senses to do so. We envision 'life' as having three dimensions, to be something we can see, feel or in some other way be aware of. We wonder if there is 'life' on other planets or in the spaces between celestial bodies. We try to communicate with 'others' who match our criteria of living beings. But all this inquiry seems to overlook a basic question: what exactly do we mean by 'life'?

Isn't it possible that there is free-floating intelligence, unhampered by physicality, in the universe? How do we know we are not surrounded by life that we are unable to apprehend? Not to go all Rod Serling, but isn't it a possibility that the little speck of space detritus we inhabit is itself part of a larger life form? For that matter, couldn't we consider the entire universe a living entity?

Just throwing this out there (see what happens when a person gets old...peculiar thoughts arise). So, how do you define "life"?

Tags: definition, life

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Replies to This Discussion

I'm not sure how I would define "intelligent life". I would probably describe it as an entity that is self-aware, and capable of not only learning from it's mistakes, but able to imagine what could be. I don't have a college degree or anything, so I'm not as informed on the subject as a scientist or professor would be :)

As far as life existing on other planets in the past, now or in the future, I was basing my opinion on the law of averages. I may be wrong, but it's interesting to think about, isn't it?

BTW, has anyone come up with ideas to answer my questions from my previous post? I'm so curious!
Mais non, Monsieur Don! On a forum like this, there is no such concept as this "sin" of which you speak. The concept of sin belongs entirely to theists, and I say let them have it.
Whose cheek?
Ah yes...to dream, perchance to sleep...(with someone's tongue in someone else's cheek)...Way to knit up the raveled sleeves, eh?
Don't try to play the age card with me, son! When the demise of Eartha Kitt was announced, I was heard to exclaim, "But she was ONLY 81!"
Should I worry about you two? I leave you alone for a little while and see what happens? lol
No need to worry, Susan. Us old folks know what we're doing and whereof we speak. A little cyber slap and tickle never hurt anyone, as far as I know.
"It's life Jim! but not as we know it !" In a discourse with a fundie recently I suggested the possibility that life on earth came from extra terrestrial origins. I was immediately accused of believing in flying saucers and bug eyed monster aliens visiting earth. Obviously the theory of life being transported to earth by meteors comet debris or astroids had not been heard. I went on to explain the theory but they continued to believe I had life being started by space alien creatures from B grade movies.

In the end I gave up quoting the line from "Monty Pythons, The Meaning of Life"

"Let's hope there is intelligent life somewhere out there in the universe. Because there's bugger all here on Earth"
Your 'poetic thought' neatly sums up what I have come to understand as the nature of life and death: it's all just a form of cosmic recycling.
Sounds like a Hoagy Carmichael song.
I have been reading this thread with great interest. Please forgive the long post. This discussion really needs to fork. Life, Intelligence, Sentience and Sapience are separate issues. For the purpose of this thread I shall discuss Life only and leave the other facets for later.


Life is an ultimate consequence of the physical laws of the Universe and arises because of, not despite of the second law of Thermodynamics.
To recap, the second law states:

Entropy will increase over time (order will become disorder) in a closed system
expressed mathematically by Ludwig Boltzmann as S = k log w

I have underlined the closed system bit because this is the part that theists deliberately or otherwise miss out.

The Sun continually provides Earth with energy that churns matter on the surface of the Earth. As a counter-intuitive consequence of the second law, localised order is created by this process. Freeze thaw cycles, local accumulation of materials, physical phase changes and cyclical evaporation of solvents all give rise to local order for transient periods. Given enough energy and enough different kinds of atom, and enough time, then ordered structures arise spontaneously as anyone who has grown an alum crystal will attest. No Deity needed. This local order is created at the expense of universal disorder. Heat is shunted off elsewhere causing more energetic and therefore more chaotic movement in particles in the surroundings. In the process the energy is degraded from high quality to low quality. In other words, the "creation" of an ordered crystal, membrane or RNA molecule is done so at the expense of order of the universal system. This is because vast quantities of low grade packets of heat are emitted by the processes willy nilly. Since Energy cannot be created or destroyed (Thermodynamics, Law, being the first) the total amount of energy in the universe is gradually being converted from high grade short wavelength EM radiation to low grade long wavelength EM radiation, resulting in the second law.

Strangely , the second law [of thermodynamics] has another consequence and can be expressed as;
"every thing in the universe tends to find a stable state in relation to its environment".
It is this principle that creates ions of sodium and yet allows from the same species of atom the production of a very reactive metal never found free in nature through the use of vast inputs of energy in the form of electricity. At less energetic levels, stability can be achieved in a number of ways.
Self assembly of crystals can be observed under the microscope or even at the shore of a pond in the cold. Self assembly of organic molecules is also something that occurs in vitro. Tubulin, a protein that accounts for much of the mass of nerve cells in all animals also self assembles into functioning microtubules and the process can be manipulated according to temperature and pH. In this respect, the self assembly of tubulin is no more amazing than the formation of ice crystals given the correct conditions and indeed self assembling tubulin molecules obey the same physical laws as water molecules obey when freezing to form ice. Again no divine hand is needed to make this work. Phospholipids, a class of phosphate containing fat molecules also form in the lab provided the building blocks and energy in the form of ultra violet light and electric discharge are available. RNA also, DNA also. All these exotic molecules self assemble because they are more stable that way. Lumped all together these can form microscopic spheres called micelles which isolate the chemistry of their interior from the rest of the world. RNA molecules attract amino acids, amino acids in close proximity to each other, for example on a membrane surface, can bond and become dipeptides. Iterate the process and polypeptides are formed. All of this can be done in vitro. While not alive, such structures are on the path of the evolution of sterile matter into Biomass. Remove the energy supply and the system favours other stable forms. Dust to dust etc.

Some self assembling molecules even self replicate. RNA and DNA are examples of these but are by no means the only ones. Aluminium silicates form delicate and intricate crystals that can “seed” the formation of geometrically identical ones. Again the most stable forms are favoured, or to use Darwin's own words “ those which are best fitted for their places in nature, will leave [the] most progeny.”
Incidentally, silicate crystals form ideal nucleation sites for the adsorption of RNA molecules. Variations in silicate micro topography will yield variations in any RNA sequences produced and can serve as a template to form more. RNA can act as a catalytic agent in some reactions and it is thought that the first enzymes were RNA molecules. Apply the Darwinian principles of survival of the most fitted to reproduce and there comes a mechanism to spread and multiply RNA molecules.
Nothing discussed so far is alive in any sense of the word, any more than four tyres and an exhaust system are an automobile. However, RNA, amino acids, phospholipids and water are all ingredients for a successful outcome of biogenesis. Current scientific thinking is that Life may have arisen independently on Earth as many as four times and we are the descendants of the best fitted. Some suggest that Earth could have been seeded via a comet. Although possible and feasable, all conditions necessary for biogenesis on Earth can be accounted for without resort to invoke an extraterrestrial influence.

Earlier in this thread Alex Donovan wrote
“This is a much more complex question than theists are generally aware of.
Where exactly does life begin? “ and then asked some more questions about computers and AI's that I will attempt to answer here.

Where does this leave us in arriving at a working definition of “what is life ?”

The kids in our schools in the UK (at least in my own classes) and I believe the US also are taught “ the seven signs of life” which are ;

Movement the ability to locomote or to change position (while expending energy to do so)
Respiration the ability to release energy from food
Sensitivity the ability to respond to stimuli
Growth an irreversible increase in biomass
Reproduction the ability to create new individuals of the same type (this includes sexual reproduction but critically it also includes asexual reproduction as seen in many plants and parthenogenesis as seen in greenfly)
Excretion the removal from the organism of metabolic by products and poisons
Nutrition the process by which raw materials for growth and repair are derived.

We teach them that a living thing must display all seven signs in order to be considered alive.
Failure on one point fails the test.
Let's use this definition as a starting point. You and I are alive, (unless you are reading this after my demise). Oak trees, whales, Gorillas and Methodists are also alive, except those that have died.
The Sun, has never been alive, nor will it ever be. Nor is the Earth the planet alive. The Universe as a whole is not alive. This is because they each fail one or more of the tests.

Bacteria, Archea, parasitic organisms such as malaria and tape worms all display all seven signs of life. They are therefore unarguably alive by the scientific definition. Prokaryotes include the bacteria, blue green algae and Archea. They all reproduce using DNA (and in some cases RNA) as a genome store and fulfil all seven signs, so they too are alive. Viruses and prions, although probably biological in origin, sub contract out their main reproductive and locomotory functions to their hosts. Viruses and prions do not do respiration, excretion, or direct nutrition. They don't do sensitivity in the sense of having specialised organs, however they are attracted to specific marker proteins in host cell membranes by Van der Waals forces, so with generous positives to sensitivity and reproduction this makes 2 out of seven. Viruses and Prions are definably not alive. At best they can be considered “meta life”.

The definition of life that we teach out seventh graders needs to be expanded to be fit for extraterrestrial and abiological situations under discussion here.
Respiration, nutrition and excretion are really facets of the same physical processes bound to the second law.
Respiration is essentially a process by which energy is harvested from the environment.
Nutrition is a process whereby raw materials are gathered from the environment. Since E=mc2 then we can argue that since energy and mass are related by the square of the speed of light and are effectively convertible then nutrition also becomes a process by which energy is harvested from the environment. So respiration and nutrition become equivalent.
Excretion removes metabolic by-products from the organism. As well as matter, metabolism also releases heat. This increases universal disorder and is a fundamental rule that life has to obey. This rule is obeyed equally by the Spiny Ant Eater, Yersina Pestis and Homo Sapiens. (An average human living to an average seventy five years would fill three Ronald Reagan class aircraft carriers with their own faeces. In addition Since each human runs at about 0.3 KW then ( 67500 hours in 75 years x 0.3 KW while alive = 20250 Kilowatt hours of heat in a lifetime. This is about seventy three billion joules per human life) they would also emit enough infra red radiation sufficient to melt about two hundred and twenty tonnes of ice at 0 degrees Celsius if popped off in one go. Life is an inherently messy process. So life is a process during which high grade energy is degraded to low grade energy. Living things are in effect chaos engines, increasing their own local order at the expense of making the universe as a whole a more disordered system.
These arguments allow many possibilities for life that any xeno-biologist would have to consider. Imagine an ecosystem of creatures based not on Carbon but on gallium arsenide, deriving their energy through the photovoltaic effect of photons in the x-ray part of the spectrum emitted from their neighbouring white dwarf. In another, gas giant world, giant baloonoids contract their quasi swim bladders and decrease in density enough to sink to the strata of compressed oxygen to fill their pseudostomachs with the liquid and then rise twenty thousand fathoms to breath in their food of gaseous hydrocarbons. In deep space a weary traveller finds an asteroid on which to spawn, lining up it's larval young so that their thermocouple bodies can generate electricity from the temperature three hundred Kelvin difference between the solar glare and the shadow of the parent's dying body. Stretching the definitions to their limit, then provided that it could self replicate, direct it's own movement and respond to changes in its environment in some way , then an entity that was able to convert heat into random radio waves, a low end chaos engine would also have to be considered to be alive. This means that biology is probably an evolutionary step in itself, with the ultimate chaos engines owning a heritage of artificial intelligence and nanofabrication conceived by a technologically advanced biological species (perhaps ourselves?) or by natural processes our race has yet to discover in this vast Cosmos. As long as an entity can satisfy the definition then its ultimate origins are irrelevant. Maybe we will see the creation of an artificial intelligence in our lifetimes. Provided that its machinery acted as a chaos engine, that it could independently and without intervention; harvest matter and energy from the environment, degrade that energy to create local order in it's structures, and replicate itself, and respond to its environment and satisfy all the criterea a sea slug fulfils then I'd call it alive.

As for life on other planets? This has been addressed already by several noted scientists and has been expressed as the Drake equation: see: http://www.daviddarling.info/encyclopedia/D/DrakeEq.html

N = R* × fp × ne × fl × fi × fc × L
where
N Present number of extraterrestrial races capable of interstellar communication
R* Mean rate of star formation, averaged over the lifetime of the Galaxy
fp Fraction of stars that have planets
ne Average number of planets in a planetary system suitable for life
fl Fraction of suitable planets on which life actually develops
fi Fraction of life-bearing planets on which intelligent life develops
fc Fraction of intelligence-bearing planets on which the capacity for interstellar communication develops
L Average lifetime of a technological civilization

For just plain unintelligent life the expression becomes

Possibility of life anywhere in the universe = R* × fp × ne × fl

There are at least 200 billion (2 x 1011) stars in the milky way (http://en.wikipedia.org/wiki/Milky_Way)
There are probably more than 100 billion (1011) galaxies in the observable universe.
(http://en.wikipedia.org/wiki/Galaxy)

The fact that we are here debating this means that none of the expressions in the Drake equation can be zero. To believe / preach that intelligent life, let alone life has only developed here on Earth and has never before and will never hereafter develop elsewhere in the universe is the ultimate human conceit. It is a Zeitgeist that imprisons our intellect and oppresses innovation. Personally I revel in the fact that I was not made by the hand of God, but rather a series of happy accidents through understandable and reproducible phenomenae. It means that I am a good person because I choose to be and not because I fear an eternal punishment or seek an eternal reward. I am Star stuff, the Universe made flesh.

Our Sun outputs a Total Solar Irradiance of about 1.3 kilowatts per metre square per second on the Earth's surface. Other suns outputs will differ in amount and relative quantities of the possible wavelengths of electromagnetic radiation available to churn up matter to the point where living chaos engines can evolve from the stellar dust. If we consider that Biomass as a very high energy state of matter then the likelihood of life elsewhere becomes based more on scientific fact than whimsy.

I agree with Hawking, Intelligent life elsewhere, especially if they are like our own species (ie majority theistic) we probably don't want to meet them.


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