The Four-Realm Knowledge Tree

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• Sensing, behaviour and the social animal Attention, memory and bias are evolved limits on what any representation can do.
• Universal law Storing and moving information costs energy.
• The technological cycle Media and storage are technologies.

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• Energy flow and dissipation All useful work is drawn from energy flows and degrades to waste heat.
• Matter and its transformations Materials can be rearranged, never created.
• The rock cycle and plate tectonics Metals, minerals and fossil fuels come from the crust.
• The carbon cycle Burning fossil fuels moves carbon from rock to sky.
• The water cycle Industry and farming draw on rivers and aquifers.
• Metabolism: the living engine Food is captured sunlight; an economy distributes the products of photosynthesis.
• Food webs and ecosystems Farming relies on pollinators, soil life and natural pest control.

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• Energetic-material throughput Every good produced is energy and materials transformed.
• Sensing, behaviour and the social animal Effort, cooperation and fairness at work are evolved dispositions.
• The information meta-cycle Coordination runs on prices, plans and know-how, which are information.
• Physiology and health Work is limited by fatigue, health and sleep.

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• The information meta-cycle Money is a record, a ledger of claims, and so part of the information meta-cycle.
• The cultural-substrate cycle Money holds value only while people trust it.
• Sensing, behaviour and the social animal Reciprocity, trust and status display are the evolved ground money builds on.
• Production and exchange Money's claims are only good while goods keep being produced.
• Energetic-material throughput Prices omit unpriced draws on the biosphere, so the ledger can show growth while the base is depleted.

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• Universal law No machine can break physical law, and efficiency has hard limits.
• Matter and its transformations Every technology is made of materials with fixed properties.
• Energetic-material throughput Technology runs on energy and materials.
• The information meta-cycle Know-how must be recorded and taught, or it is lost.

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• Sensing, behaviour and the social animal Coalition, dominance and in-group loyalty are older than any constitution.
• The cultural-substrate cycle Laws hold only while the culture ratifies them.
• The information meta-cycle Accountability is information about what power has done.
• Energetic-material throughput States rest on food, energy and the means to defend them.

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• Sensing, behaviour and the social animal Culture is built from evolved capacities: imitation, bonding, the search for meaning.
• The demographic-formational cycle Culture lives only in people formed to carry it.
• The information meta-cycle Culture is transmitted, stored and validated through the information meta-cycle.

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• Reproduction and heredity Every person is born through biological reproduction.
• Physiology and health Formation depends on health, nutrition and sleep.
• Sensing, behaviour and the social animal Children are formed through attachment and imitation before instruction.
• The cultural-substrate cycle What a child is formed into is the culture that receives them.

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• Matter and its transformations Heredity is molecular: DNA's chemistry is what copies and mutates.
• Universal law Copying and repair cost energy and are bounded by thermodynamics.

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• Energy flow and dissipation Photosynthesis captures a fraction of the sun's flux; all food energy starts there.
• The carbon cycle Plants build themselves from carbon in the air.
• The water cycle Photosynthesis splits water, and plants transpire it.
• Nitrogen, phosphorus and sulphur cycles Growth is limited by nitrogen and phosphorus.

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• Metabolism: the living engine A body is metabolism kept in balance.
• Universal law Body temperature and energy budgets obey thermodynamics.
• Atmosphere, oceans and climate Heat, cold and the seasons set what bodies can tolerate.

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• Reproduction and heredity Selection acts on inherited variation.
• Atmosphere, oceans and climate Climate shifts have driven adaptation and mass extinction.

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• Metabolism: the living engine Food webs pass on energy first captured by plants.
• Nitrogen, phosphorus and sulphur cycles Decomposers return nutrients to soil and sea.
• The water cycle Water availability sets which ecosystems can exist.

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• Food webs and ecosystems Populations are limited by food, predators and disease.
• Atmosphere, oceans and climate Ranges move as the climate changes.

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• Evolution by selection Drives and social instincts are evolved adaptations.
• Physiology and health Emotion and stress are bodily states before they are feelings.

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• Cosmic structure and planetary systems Earth's orbit, size and interior heat were set when the solar system formed.
• Universal law Gravity and thermodynamics govern the planet's shape, heat and hold on its air.

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• Matter and its transformations Rocks are minerals: their formation and weathering are chemistry.
• Earth's physical givens Interior heat drives the plates.

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• Energy flow and dissipation Sunlight evaporates the water that falls as rain.
• Matter and its transformations Water's unusual chemistry sets how it stores heat and dissolves rock.

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• Energy flow and dissipation Climate is the balance of incoming sunlight and outgoing heat.
• Earth's physical givens Tilt and orbit set the seasons and pace the ice ages.
• The water cycle Water vapour and ice are the climate's largest feedbacks.

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• The rock cycle and plate tectonics Over millions of years, weathering and volcanoes set atmospheric carbon.
• Matter and its transformations Carbon's chemistry determines where it can be stored.

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• The rock cycle and plate tectonics Phosphorus comes only from weathered rock.
• Matter and its transformations Nitrogen's triple bond is why fixing it takes life or industry.

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• Universal law Chemistry is quantum mechanics and thermodynamics applied to atoms.

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• Universal law Gravity, fusion and radiation are universal law at work.
• Matter and its transformations The cycle's product is the periodic table.

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• Universal law Structure forms under gravitation and relativity.

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• Universal law The flow is governed by the first and second laws of thermodynamics.
• The stellar life cycle The sun is a star partway through its life cycle.