OPEN LIBRARY · FIRST COLLECTION
Knowledge Galaxy
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Choose a subject below. The first Physics lesson is available now; the other 15 collections are clearly marked Planned.
Read the first lesson →PHYSICS & ENERGY · AVAILABLE LESSON
Falling together
In a vacuum, two objects released from the same height fall in the same time, regardless of mass. Gravity gives both objects the same acceleration. Air resistance can change this result outside a vacuum.
For an object released from rest, the fall time is t = √(2h/g), where h is height in metres and g is gravitational acceleration in metres per second squared. From 5 metres with Earth gravity (9.81 m/s²), both a 1 kg mass and a 10 kg mass take about 1.01 seconds.
Try predicting what happens if the release height doubles. The fall time increases by a factor of √2, about 1.41, rather than doubling.
Physics & Energy: planned topic roadmap
The gravity reading lesson above is available. This wider ten-topic roadmap is planned, not a collection of completed lessons.
- Motion & Mechanics
- Electricity & Magnetism
- Heat & Thermodynamics
- Waves, Light & Sound
- Quantum Physics
- Nuclear & Particle Physics
- Atoms, Molecules & Chemical Reactions
- Organic, Inorganic & Physical Chemistry
- Analytical Chemistry & Spectroscopy
- Energy Conversion & Storage
This is a reading lesson. Interactive experiments, accounts, saved progress and the pod game are not part of this public page yet.
Collections taking shape
These subjects are part of the planned library. They do not have published lessons here yet. You can read the available gravity lesson without creating an account.
Math & Logic
Planned · No lessons published yet
Numbers, patterns, geometry, probability and reasoning.
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Topic roadmap only; these are not published lessons.
- Numbers & Numeracy
- Algebra
- Geometry & Topology
- Calculus & Analysis
- Probability & Statistics
- Discrete Mathematics
- Logic & Proof
- Optimization & Decisions
- Networks & Complex Systems
- Information Theory
Space & Time
Planned · No lessons published yet
Stars, planets, space exploration and the study of time.
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Topic roadmap only; these are not published lessons.
- Astronomy & Observation
- Cosmology & the Universe
- Relativity & Spacetime
- Stars & Galaxies
- Planets & Solar Systems
- Exoplanets & Astrobiology
- Orbital Mechanics & Satellites
- Spaceflight & Exploration
- Space Weather & Cosmic Hazards
- Timekeeping & Calendars
Earth & Climate
Planned · No lessons published yet
Our planet, weather, oceans, geology and climate.
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Topic roadmap only; these are not published lessons.
- Geology & Geophysics
- Geography & Maps
- Oceans & Coasts
- Weather & Atmosphere
- Water & Hydrology
- Climate & Climate Change
- Soil & Land
- Earth History & Paleontology
- Natural Resources & Environmental Pollution
- Natural Hazards & Resilience
Life & Ecology
Planned · No lessons published yet
Living systems, evolution, biodiversity and ecosystems.
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- Cells, Molecular Biology & Biochemistry
- Genetics & Genomics
- Evolution
- Microbes
- Plants & Fungi
- Animals & Behavior
- Anatomy & Physiology
- Development & Reproduction
- Ecosystems & Biodiversity
- Conservation & Ecological Restoration
Health & Mind
Planned · No lessons published yet
The body, the mind, wellbeing and public health.
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Topic roadmap only; these are not published lessons.
- Medicine & Prevention
- Public Health & Epidemiology
- Psychology & Cognition
- Neuroscience
- Mental Health & Wellbeing
- Nutrition
- Movement, Sleep & Recovery
- Sexual & Reproductive Health
- Disability, Rehabilitation & Assistive Technology
- Caregiving & Aging
Engineering & Making
Planned · No lessons published yet
Designing, building, repairing and understanding how things work.
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Topic roadmap only; these are not published lessons.
- Civil Engineering & Infrastructure
- Architecture & Urban Planning
- Mechanical Engineering
- Electrical & Electronic Engineering
- Materials, Metals, Polymers & Nanotechnology
- Chemical & Biological Engineering
- Manufacturing, Fabrication & Repair
- Robotics & Control
- Transportation & Aerospace
- Safety, Reliability & Sustainable Design
Computing & AI
Planned · No lessons published yet
Computers, programming, artificial intelligence and human–AI collaboration.
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- Programming & Software Engineering
- Algorithms & Data Structures
- Databases & Data Engineering
- Computer Hardware & Operating Systems
- Networks & Distributed Systems
- Cybersecurity & Privacy
- Human–Computer Interaction & Accessibility
- Machine Learning & Generative AI
- AI Evaluation, Interpretability & Safety
- AI Agents & Human–AI Collaboration
Data & Evidence
Planned · No lessons published yet
Measurement, research, uncertainty and evaluating evidence.
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- Measurement, Units & Uncertainty
- Data Collection & Sampling
- Statistical Analysis
- Data Visualization
- Experiments & Causal Inference
- Evidence & Source Evaluation
- Research Synthesis & Fact-Checking
- Reproducibility & Open Research
- Data Quality & Provenance
- Data Ethics & Governance
Languages & Communication
Planned · No lessons published yet
Languages, reading, writing, translation and accessible communication.
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- World Languages & Multilingualism
- Linguistics
- Reading & Literacy
- Writing & Rhetoric
- Literature & Poetry
- Storytelling
- Translation & Interpretation
- Sign Languages & Accessible Communication
- Speech & Public Speaking
- Journalism, Media Literacy & Intercultural Communication
History & Cultures
Planned · No lessons published yet
Human histories, cultural traditions, archives and shared memory.
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- World & Regional Histories
- Ancient Worlds & Archaeology
- Migration & Cultural Exchange
- Empires, Trade & Colonialism
- Revolutions & Modern History
- Indigenous Histories & Knowledge Traditions
- Religions & Spiritual Traditions
- Folklore & Mythology
- Heritage, Archives & Memory
- Histories of Science, Technology & Medicine
Society & Governance
Planned · No lessons published yet
Communities, institutions, economics, rights and civic life.
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- Anthropology & Sociology
- Population & Demography
- Politics, Institutions & Public Policy
- Law, Rights & Justice
- Economics, Markets & Public Finance
- Business, Entrepreneurship & Management
- Work, Careers & Labor
- Trade, Supply Chains & Development
- Families, Communities & Social Change
- International Relations, Peace & Security
Ethics & Cooperation
Planned · No lessons published yet
Ethical reasoning, responsibility, trust and working together.
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- Philosophical Traditions
- Knowledge, Reality & Meaning
- Moral Philosophy & Applied Ethics
- Mind, Agency & Consciousness
- Human Rights, Justice & Fairness
- Technology & AI Ethics
- Environmental & Animal Ethics
- Cooperation, Negotiation & Conflict Resolution
- Trust, Consent & Responsibility
- Future Generations & Global Challenges
Arts & Creativity
Planned · No lessons published yet
Visual art, music, storytelling, design and creative practice.
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- Drawing, Painting & Sculpture
- Graphic Design & Typography
- Music & Sound
- Dance & Movement
- Theatre & Performance
- Film & Animation
- Photography
- Crafts, Fashion & Textiles
- Games & Interactive Art
- Creative Practice & Criticism
Living & Survival
Planned · No lessons published yet
Everyday skills, practical problem-solving and preparedness.
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Topic roadmap only; these are not published lessons.
- Cooking & Food Skills
- Home Care & Repair
- Gardening, Agriculture & Food Systems
- Personal Finance & Consumer Skills
- Digital Life & Personal Organization
- Relationships, Parenting & Boundaries
- Travel, Navigation & Outdoor Skills
- Sports, Games & Recreation
- First Aid & Personal Safety
- Emergency Preparedness & Community Resilience
Learning & Discovery
Planned · No lessons published yet
Learning skills, scientific inquiry, libraries and discovery.
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Topic roadmap only; these are not published lessons.
- Learning & Study Skills
- Teaching & Educational Design
- Scientific Methods & Inquiry
- Research Questions & Hypotheses
- Search, Libraries & Information Literacy
- Critical & Systems Thinking
- Creativity & Problem-Solving
- Knowledge Organization & Concept Maps
- Collaborative Learning & Citizen Science
- Discovery, Innovation & Responsible Experimentation