The outer world is the world directly observed by our human senses and using sensory apparatus such as telescopes, microscopes, voltmeters, magnetometers, seismographs, X-ray machines, thermometers, etc. It is the realm of phenomena studied by modern physical science and is known as the physical world.

The inner world of the mind consists of interacting mental structures and is covered in The Great Chain of Mental Being .

All FORMS interact via FORCES at the subconscious or physical level and via INFORMATION at the conscious level. The nature of the connection between the inner and outer worlds forms the crux of the famous mind-body problem.

Within and beyond our local mental being is the greater spiritual world and is covered in The Great Chain of Spiritual Being. This realm has mainly been explored by mystics, yogis and other human beings who either are gifted with senses beyond the ordinary physical senses or who have refined their inner being and senses to the point that they can interact with the spiritual realm. This realm has been the main concern of religions throughout history.

Both the outer physical world, the inner mental world and the greater spiritual world are parts of The Great Chain of Being.

FORM and SPACE
The most basic and greatest FORM is SPACE, the great void stretching out in all directions. Space is the great container, the great vessel that contains all the smaller vessels. Space is the background of physical reality, a manifold with three, or possibly more, geometric dimensions. Higher dimensional spaces may exist in the spiritual realms and/or at sub-quark lengths. Within our physical space exist physical FORMS, structures that interact with each other and with the underlying space, and without which space would be empty.

Locally space has three dimensions: length, width and height and is Euclidean or flat. At the microscopic level, at scales smaller than that of quarks (10^-15 meters), there may be more dimensions that are "wrapped up" according to String Theory. At intermediate scales, those of planets and stars, space-time is curved due to gravity (see General Relativity). In interstellar and intergalactic voids space is very close to flat, inertial reference frames exist and follow the laws of Special Relativity. At very large scales, beyond the sizes of galaxy clusters, space is curved and deviates from Euclidean or flat space. The space of our known physical unverse may be contained in a greater multiverse of other three dimensional spaces, and all these may be contained in spaces of higher dimensions.

ENERGY and TIME
The change of forms, the interactions of forms, the movement of forms, all activity of the forms, takes place via ENERGY. Without energy, no change would be possible. With energy, change, becoming and measurable TIME are possible. Without energy, time could pass, but no one could tell how fast, slow, etc. Without energy and measurable time, one would have a physically static world close to the abstract world of eternity. There would only be being and no becoming. So SPACE is the most primordial and greatest FORM containing the smaller FORMS. When ENERGY is present, one gets SPACE-TIME.

CONSTRUCTED STRUCTURES
The interacting structures within space are constructs that primarily occupy a localized area of space. But secondarily, the possible influence of a structure can spread out to all the rest of space, so the idea of localization and how one defines a particular structure is somewhat of a human mental characterization. Each structure is composed of smaller structures bound together by energy or force. The smaller structures are composed of still smaller structures that are bound together more tightly than the larger structures, naturally enough. This process finally terminates with a group of fundamental particles that make up the basic building blocks of all physical structures. Whether these fundamental particles are of composed of still smaller particles is currently unknown.

Thus to probe smaller and smaller scales, as is done using particle accelerators to smash particles together, requires slamming them together at higher and higher energies to break them apart. So the scales that can be currently probed are limited by the largest energies that the world's particle accelerators can generate, which is about 2 TeV (2 trillion electron volts) at present (circa 2000 ACE).

The Form and Energy Problem. The study of pure FORM alone is the purview of Mathematics. In the physical world both FORM and ENERGY exist and are coupled together. How this is done at a fundamental level is unknown. Einsteins famous equation, E=mc², states that the rest mass of a particle can be converted into energy and vice versa, but that energy is always associated with a particular form, usually photons. Photons of sufficient energy can be converted into particles and particles into photons. But there is no such thing as "pure energy" as is often stated, just as there is no such thing as a pure, bare, self-existing, unchanging particle. Pure energy, like bare particles, could not interact with anything else and so cannot be part of an interactive universe.

Energy can take two (or three forms):
   1. Binding energy (can be positive or negative)
   2. Kinetic energy or energy of motion
   3. Structural (this could perhaps be considered binding energy)

Is it possible to have FORMLESS beings as Buddhists discuss? Or does this merely mean formless in the way a gas or liquid is formless, i.e. without a rigid form although they do indeed have a FORM.

Forces are related to changes in ENERGY.
There are Four known Fundamental forces and a host of secondary forces derived from them.

The Four Known Fundamental Forces in order of increasing relative strength:
   1. The gravitational force acts on mass-energy. Attractive only.
   2. The weak nuclear force acts on 6 flavor charges (Up, Down, Strange, Charm, Top, Bottom).
   3. The electromagnetic force acts on 2 electric charges (positive, negative). Attractive/Repulsive
   4. The color force (sometimes called the strong force) acts on 3 color charges (Red, Green, Blue).

An effective fifth force, Fermionic repulsion, exists as well. Particles can have spins that are either half multiples (spin 1/2) or whole multiples (spin 1) of the fundamental quantum spin state. Particles with spin 1/2, known as fermions , exhibit a quantum repulsion and hence cannot occupy the same space, or more exactly, the same quantum energy level. Because of fermionic repulsion, atoms, stars and planets can exist as stable bulk forms of matter. Particles of spin 1 are known as bosons and can be packed without limit into the same space. Bulk bosonic matter exhibits exotic properties such as superconductivity and superfluidity.

In curved space-time, all particles, independent of their composition, experience an acceleration more commonly known as the force of gravity. Hence the curvature of space-time determines how matter-energy can move and redistribute itself. In fact "curvature" in space-time means acceleration. The detailed nature of the interaction of space-time with matter-energy is described by Einstein's General Theory of Relativity . Einsteins theory predicts several gravitational effects, that have been confirmed, that were not part of Newton's earlier theory, such as the bending of the path of light in a gravitational field, the slowing down of clocks as gravity increases and the red shift (or energy loss) of light as it leaves a gravitational field. Light bending around massive objects is called gravitational lensing and is an active area of astrophysical research.

The force of gravity can be described in simpler terms using Newton's earlier theory of gravity, which was superseded by Einstein's, but is still useful and widely used. The strength of the force of gravity is linearly proportional to the total mass of the two interacting bodies (with masses m₁ and m₂) and falls off as the square of the distance (R) between the bodies, or F = Gm₁m₂/R². The force F is measured in Newtons, distance in meters and mass in kilograms. The strength coupling constant G has a currently measured value of: 6.67259x10^-11 m³kg^-1s^-2

Bulk Form:
The known physical universe.

Large black holes of millions to billions of solar masses are also known to exist in the centers of galaxies. Some of the matter orbiting around such giant black holes can be ejected in the form of powerful jets that can span thousands of light years and are seen emanating from the centers of active galaxies called Seyefert galaxies, BL Lac objects or quasars depending on how strong the jets are and their orientation with respect to us.

Observations of distant supernova show that the expansion of the universe is accelerating against the pull of gravity indicating a repulsive force at work that has been dubbed dark energy.

Fundamental particles are particles with no known substructure and are the building blocks of composite particles. There are two classes of fundamental particles known. The first class are structural particles and are all fermions. The second class transmits forces and are all bosons. The Standard Model is the collective theory of the fundamental particles and the three nongravitational forces by which they interact.

The 12 Fermion Structural Particles (and 12 antiparticles)
  These are divided into two classes (light leptons and heavy quarks) and three families (I, II and III). The quarks and leptons are smaller than 10^-19 meters in radius.

  Leptons
    I. Electron and Electron Neutrino
    II. Muon and Muon Neutrino
    III. Tau and Tau Neutrino
  
   Quarks
    I. Up and Down Quarks
    II. Strange and Charm Quarks
    III. Top and Bottom Quarks

The 4 (or 6) Boson Force Carrying Particles
  Photons - transmit the electromagnetic force
  Intermediate Vector Bosons - transmit the weak force
        W+ and W-
        Z0
  Gluons - transmits the color force
 
  Higgs boson - particle that provides mass but not confirmed
  Graviton - particle hypothesized to transmit gravity but not confirmed

Affects particles with electric charges. Electric charge comes in two types: positive and negative. Like charges repel each other and unlike charges attract. The attractive and repulsive force is of the same strength. Beyond the qunatum scale the electric force falls off in strength as the distance squared and is linearly proportional to the product of the interacting charges. The strength coupling constant K has a currently measured value of: 8.9876x10⁹ Nm²C^-2 where N is the force in Newtons, m is meters and C is Coulombs, a measure of electric charge. The charge on one electron is 1.60217733x10^-19 C. At the macroscopic level the behavior of the electromagnetic field is described by Maxwell's equations. At the microscopic, i.e. quantum scale applicable in atoms, the behavior is described by the theory of quantum electrodynamics.

Accelerating electric charges produce waves in the electromagnetic field that, being light itself, emanates away from the charges at the speed of light. This most fundamental speed is c = 3x10⁸ m s^-2, in a vacuum. Light or electromagnetic waves travel at a slower speed in media (such as glass, air or water).

Electrons, Muons and Tauons (structural particles)
Photons (force particle)

Bulk photon form (or all the EM radiation fields in the universe):
  The Cosmic Microwave Background
  Other Radiation Backgrounds: Gamma-ray, X-ray, Ultraviolet, Optical, IR, Radio

Gluons (force particles):
  Red, Green, Blue

Mesons
Particles composed of a bound Quark-Antiquark pair. They are unstable and short lived.

Baryons

Nucleon Quark triplets
  Protons: 2 up and 1 down quark (UUD)
  Neutrons: 1 up and 2 down quarks (UDD)

Nuclear binding energies are in the range of 1-9 MeV (million electron volts) or roughly 1 million times greater than the binding energy of electrons in atoms (see below).

Stable Nuclei
Bulk form:
  Neutron star outer layers, old supernova debris

Radioactive Nuclei
These are unstable nuclei that change form by undergoing a radioactive decay.
Radioactive decay can occur in the following ways:
  Alpha decay: emission of an alpha particle, i.e. a Helium nucleus (2 protons, 2 neutrons)
  Beta decay: emission of an electron and an electron antineutrino
  Positive Beta decay: emission of a positron and an electron neutrino
  Gamma decay: emission of a gamma ray photon
  Electron capture: a nucleus captures a surrounding electron and emits a neutrino
  Internal conversion: interaction of the nuclear multipolar electric field with electron cloud causes ejection of an electron

Bulk form:
  Young Supernova debris (relatively speaking, depends on the half-life of the radioactive nuclei)

Electrons are bound to their parent nuclei with binding energies that range from about 10 eV for outer shell electrons upto 120 keV (kilo electron volts) for the innermost electrons in the heaviest elements.

Neutral Atoms
In neutral atoms (no net electric charge) the number of negatively charged electrons is equal to the number of positively charged protons in the nucleus. There 104 types of Neutral Atoms currently known. These are the elements Hydrogen, Helium, ... up to element 104. Of these 93 are known to occur naturally, the rest (elements 94 and beyond) are all manmade. Elements 105 to 111 may exist depending on the plausibility of current claims of element synthesis. The Periodic Table displays the full set of elements and some of their properties.

Bulk form:
Collections of atoms exist in bulk form in three phases: solids, liquids and gases.
  Gases - Interstellar gas clouds, Cool Star Atmospheres, Gas Giant Atmospheres, Terrestial Planet Atmospheres
  Liquids - Planetary Oceans, Lakes, Rivers, Gas Giant Interior Layers,
  Terrestial Planet Interior Layers
  Solids - Terrestial Planets, Moons, Asteroids, Comets, Dust

Ions
These are electrically charged atoms with more (negatively charged) or less electrons (positively charged) than there are protons in the nucleus.

Bulk form:
  Plasmas - Stellar plasmas, stellar winds, HII Regions, planetary ionospheres and magnetospheres, compact object magnetospheres, other charged regions

When more matter is added to a white dwarf star, the electrons are pushed more closely together and respond, via the Heisenberg uncertainty principle, by moving faster, thus increasing the electron pressure to support the increased weight. This process can continue as more weight is added until the electron velocity reaches close to the speed of light at which point it can increase no further. Adding more mass thus does not increase the electron pressure and when eneough weight is added, the star will collapse, forming a neutron star. The mass limit where this occurs is about 1.4 solar masses with some small spread depending on the composition of the star, and is known as the Chandrasekhar limit. No white dwarf stars more massive than the Chandrasekhar limit can exist and none have been measured in any white dwarf binary star system.

Covalent bonds

Ionic bonds

Metallic bonds

Van der Waals bonds

Hydrogen bonds

Diatomic Molecules
The simplest type of molecule is composed of two atoms bound together. At most there could be 0.5*N*(N+1) where N is the total number of elements. For N=104, this comes to 5460 potential diatomic molecules. But the actual number is much less. Surprisingly enough, chemists don't seem to know the actual number of stable diatomic molecules existing! Seven of the elements will combine with themselves: H, N, F, O, At, I, C and B (Have No Fear of an Ice Cold Beer). The halogen astatine (At) is an unstable element with a half-life of 8.3 hours for the most stable isotope and is usually not included in the list. Molecular Oxygen (O₂) and molecular Nitrogen (N₂) compose 99% of the Earth's atmosphere.

Examples of common heterogenous diatomic molecules are Sodium Chloride or table salt (NaCl), Carbon Monoxide (CO), Nitrous Oxide (NO), etc.

Triatomic Molecules
Water (H₂O), Carbon Dioxide (CO₂), Ozone (O₃), Silicon Dioxide (SiO₂), etc.

Simple Molecules with four or more atoms
Ammonia (NH₃), Methane (CH₄), etc.

Carbon based molecules can form complex Hydrocarbon chains, Polymers, Molecular rings, Buckyballs, etc.
Carbon molecules also form the basis for the molecules of organic life: Sugars, Fatty acids, etc.

Water comes in all three basic phases on the surface of the Earth: solid, liquid and gas.

Important physical chemical properties of water involve:
  1. Acids, bases and salts in solution.
  2. Solubility, the ability of compounds to dissolve in a liquid.

Water is a polar molecule and so materials composed of polar molecules will readily dissolve in water. However, nonpolar molecules (such as lipids) will not. These different solubility properties are essential to the formation of and operation of life. Insoluble cellular structures (such as the cell membrane), are composed of a nonpolar layer of molecules that surround and contain solutions of soluable organic molecules. Cells, and hence all cellular life, are essentially complex "bags of water".

Four major classes of organic molecules are built from molecular monomer units that are strung together to form polymers. These 4 classes are:

I. DNA - composed of nucleotide monomer units. The nucleotides are composed of an amino acid, a sugar base (Deoxyribose) and a phosphate group.
II. RNA - composed of nucleotide monomer units. The nucleotides are composed of an amino acid, a sugar base (Ribose) and a phosphate group.
III. Proteins - the monomer unit is an amino acid of which 20 different types are possible.
IV. Polysaccharides - the monomer units are sugars

V. The fifth major class of organic molecule are the lipids. The lipids are composed of fatty acid subunits although the lipids are not polymers.

There are 7 main groups of viruses classified by their nucleic acid structures ( The Baltimore Method):
I. double stranded DNA
II. single stranded DNA
III. double stranded RNA
IV. positive sense (same polarity as mRNA) spiral single stranded RNA
V. negative sense spiral single stranded RNA
VI. RNA reverse transcribing
VII. DNA reverse transcribing

More than 4,000 virus species divided into 71 families or groups have been identified as of 1995.

All Cellular Life is divided into three Domains: Archaea, Bacteria and Eucarya
Each Domain is further divided into the 7 categories of Kingdom, Phylum, Class, Order, Family, Genus, and Species. This 7 step classification scheme can be supplemented by sub or super categories at each stage.

Green plant cells have special structures called chloroplasts that allow them to absorb photons from the Sun and creates the chemical energy ( photosynthesis) to drive cellular metabolism. The solar derived chemical energy drives most of the biosphere on Earth. A second set of cells uses chemical energy ( chemosynthesis) to drive metabolic processes. Chemosynthetic life evolved first and much of it lives in exotic environments such as hydrothermal vents.

Most life forms on Earth contain only a single cell. The simpler cells do not contain a nucleus and are called prokaryotic cells. All Prokaryotic life is single-celled and is classified into the two Domains: Archaea and Bacteria

Domain Bacteria

Domain Archaea
Simliar in outward appearance to bacteria but chemically and genetically very different. Three kingdoms have been identified so far: Euryarchaeota, Crenarchaeota and Korarchaeota
The archea contain the Extremophiles, life capable of living in extreme environments that include very hot water (thermophiles), highly acidic water, high salt conditions (halophiles), high sulfur conditions in deep sea vents, petroleum and even solid rock. Other types include that methanogens that produce methane and are posioned by oxygen. Archea that live at more moderate temperatures have been found on the deep sea floor, ocean surface, soil and guts of animals.

Domain Eucarya

What a piece of work is a man! how noble in reason! how infinite in faculty! in form and moving how express and admirable! in action how like an angel! in apprehension how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust?
William Shakespeare, "Hamlet", Act II, scene 2

Elemental Composition
A typical human weighing 100 kilograms is composed of about 3x10²⁷ atoms divided into 14 different elements.

Dry Weight Elemental Composition by percent

Carbon	50	Sulfur	0.8
Oxygen	20	Sodium	0.4
Hydrogen	10	Chlorine	0.4
Nitrogen	8.5	Magnesium	0.1
Calcium	4.0	Iron	0.01
Phosphorus	2.5	Manganese	0.001
Potassium	1.0	Iodine	0.00005

Typical Chemical Composition by percent

Water	61.6
Protein	17.0
Fat	13.8
Minerals	6.1
Carbohydrates	1.5

Genetic Properties
The carrier of genetic properties is the DNA molecule contained in the nucleus of nearly every cell in the body (some cells, such as red blood cells, have no nucleus). The DNA in a human cell nucleus, otherwise known as the Human Genome, is divided in 46 pieces arranged in 23 paired chromosomes. The total length of the DNA in a nucleus is about 1 meter and contains 3.3 billion base pairs (34 Angstrom length for every 10 base pairs). The DNA is currently believed to code for about 20,000 - 25,000 genes, the segments of DNA that code for specific proteins. Each gene contains a few hundred to a few thousand base pairs with an average of around 4000 base pairs, so most of the DNA in a nucleus (about 97%) does not code for proteins. The nonprotein coding DNA has sometimes been called "junk" DNA, however this portion of the DNA may code for RNA molecules that are important in control of cellular operation.

Cellular Composition
There are about 60 trillion (6x10¹³) cells in the human body. These are divided into about 214 different types of cells that fall into 20 different classes.

Tissue Composition
The cells of the body are organized into four tissue types:
Epithelium - Lines, covers, protects, absorbs and secretes.
Connective tissue - As the name suggests, connective tissue holds everything together. Blood is considered a connective tissue.
Muscle tissue - Muscle cells contain contractile filaments that move past each other and change the size of the cell.
Nervous tissue - cells forming the brain, spinal cord and peripheral nervous system.

Organ Composition

Organ Systems
The organs of the human body are arranged into 12 organ systems:
1. circulatory system
2. digestive system
3. endocrine system
4. immune system
5. integumentary system
6. lymphatic system
7. muscular system
8. nervous system
9. reproductive system
10. respiratory system
11. skeletal system
12. urinary system

The Brain and Nervous System
The nervous system is the organ system most closely associated with the conscious properties of human beings, although other systems may participate as well (e.g. endocrine system). The Brain/nervous system contains about 100 billion cells (neurons and glia or just neurons? check this) (10¹¹) composing about 0.167% of the body's total cells. Each neuron, on average, is connected to about 10,000 others for a total of 1 quadrillion (10¹⁵) connecting links. The brain is the most critical part and communicates with the body via the peripheral nervous system.

Conscious System
The conscious properties of the human operate through the chakra system. The chakra's are a set of 7 major conscious structures that cannot by seen by physical instruments but can be readily seen by a trained meditator with their inner eye. They produce and regulate the conscious phenomena of instinctual reactions, sexual urges, bodily commands, emotions, thoughts, dreams, psychic experiences and spiritual experiences. The chakral system is intimately connected to the brain/nervous system and this is part of the mind/body problem that is perhaps the most difficult and profound problem facing science today.

Self System
The Self is the most fundamental part of a human being and the part considered most "yourself". It contains the observing "I", the deepest sense of self, the will and the attention. How these parts are connected to the chakra system and the rest of the body as well as the greater spiritual world is at present unknown.

II. Collective Properties of the Human Species

"It is necessary to understand that war is common, strife is customary, and all things happen because of strife and necessity."
Heraclitus (quoted in Origen, Against Celsus )

About 6 billion human beings existed on Planet Earth in the year 2000 ACE, divided into roughly 170 nations covering all the continents and islands of the world except for Antarctica, which is held in common by all. Humans have explored the entire surface of the Earth including the polar regions, climbed the highest mountains and gone down into the deepest ocean depths. The atmosphere has been explored and regularly transversed with airplanes and other vehicles and humans have gone into low Earth orbit in spacecraft. Twelve men have walked on the surface of the Moon. Robotic spacecraft have landed on the Moon, Mars, Venus, Jupiter, Titan and one asteroid. Space probes have been sent to all planets in the Solar System except Pluto, as well as to several comets and asteroids.

Homo Sapiens evolved from our immediate predecessor Homo Erectus in a slow transition that happened about 1 million years ago. Thus Homo Sapiens have existed for roughly 50,000 generations assuming a mean generational length of 20 years. During this time, three ice ages have occurred that probably made a great impact on our evolution and the development of culture.

For most of our history, humans have lived in semi-nomadic Hunter-gatherer societies, in which food was obtained by hunting wild animals and gathering wild plants.

Nomadic herding (domesticating animals) started more than 10,000 years ago.

Large scale agriculture (domesticating plants) started about 10,000 years ago.

Agriculture led to the existence of settled populations in cultivated lands. For the last 8,000 years or so cities and towns were being created and melded into nations of ever greater size. The collections of cities and towns suffered periodic attacks and conquests by tribes of nomadic herdsmen and hunter-gathers or by other nations.

Writing started about 5000 years ago with cuneiform writing in Mesopotamia and shortly thereafter with hieroglyphic writing in Egypt. Writing also developed later elsewhere independently. Thus begins recorded history in which we know the names of actual people, places, and specific events and the thoughts of individuals.

The first great nation state known (but not necessarily the first) was the Kingdom of Egypt that started around 3000 BCE in the Nile Valley when the Pharoah Narmer united lower and upper Egypt together into one state. Great Empires were created by conquests that assimililated many cities, towns and tribes together into nations and often later fell apart. The first truly multinational empire was the empire of Sargon the Great founded around 2250 BCE in Mesopotamia and surrounding regions. Some later empires were the Assyrian, Bablyonian, Persian, Greek, Carthaginian, Roman, Indian, Chinese, Aztec, and Incan. The last period of significant nomadic invasions were the Mongol conquests of Eurasia in the 13th-14th centuries. The invention of ocean traveling ships led to the rise of overseas colonial empires. Some of the first were by the Vikings around 1000 ACE and later the European Colonial Empires of the 16th to 20th centuries, that have now been disbanded. The world is now divided into a collection of over 170 nation-states.

Significant collapses of city/town based areas of civilization:
1. Mycenean/Minoan and Hittite civilizations in the Aegean and Asia Minor region around 1100 BC (giving rise to the Atlantis legend?).
2. The Mohenjo-Daro civilization of the Indus valley.
3. The West Roman Empire in the 400's.
4. Mayan civilization in Meosamerica in late 800's ACE.
5. Anasazi civilization (SW USA) in 1300's ACE?
6. The Mound builder civilization (SE USA) in 1400's ACE?
7. The Khmer civilization in SE Asia in ?

Examples of nomadic invasions and conquests.
1. Hyskos conquest of Egypt, circa 1500 BCE
2. Celtic invasions of Roman Republic Italy, circa 700 BCE.
3. Cimmerian invasion and liquidation of Phrygia around 700 BCE.
4. Invasion and conquest of Mycenean Greece by the Hellenes and subsequent attacks by the "Sea Peoples" on Egypt which successfully resisted and the Hittite Kingdom which collapsed. The Philistines are descendents of the Sea Peoples that founded at set of cities in Canaan in what is now the Gaza strip. 5. Aryan invasion and conquest of Northern India, circa 1000 BCE
6. Persian/Median conquest of Assyrian Empire in 612 BCE.
7 Numerous attacks on the Roman Empire culminating in the Gothic/Vandal attacks, followed by the Huns, leading to collapse of West Roman Empire circa 400-500 ACE
8. Arab invasion of Roman and Parthian empires in 600's.
9. Viking invasions of Medieval Europe 790-1100 ACE.
10. Turkish invasion and conquest of Islamic empire circa 1000-1200 ACE.
11. Aztec invasion and conquest of central Mexico late 1300's/1400's ACE.
12. Mongol invasions of Eurasia, circa 1200-1300 ACE.
13. Mongol and Thai invasion of the Khmer empire.

The city way of life or "civilization" has come to dominate the entire world. The invention of rapid transportation and communication have melded the peoples of the Earth into an interconnected global civilization for the first time in history. The effects on regional societies of the spread of science, technology and industrialization are still in progress and causing much stress. There are still many festering religous, cultural, ideological, national, tribal and ethnic rivalries to be resolved that will probably erupt in various 21st century conflicts. Whether the world will see the rise of a single (or small number) of global political entities in the 21st century remains to be seen.

Much of the rapid transportation and abundant electrical power now enjoyed by much of the world's peoples depends on the exploitation of fossil fuels - coal, petroleum, and natural gas that will be exhausted or severely depleted by the end of the 21st century so a looming energy crisis is a challenge to be met in the future. The expansion of the world population (6 billion+ and rising) is creating problems with environmental degradation, resource depletion and pollution on a scale unknown only a century ago and present great challenges for 21st century global society.

Possible Others:
Some Apes?
Elephants?
Bee Colonies?
Termite Colonies?