Grown-Up Guide · 120 Big Questions Kids Ask

How to use this guide

Let the child choose a question. Ask what they notice in the picture before you explain more. Listen for the reason behind an answer. You can come back to a page together.

Nothing needs to be written down. The conversation starters are invitations, not quizzes.

Download the printable guide (PDF)

The game that goes with the book

Big Question Islands has 8 islands and 120 short levels, one for each question, and every level points to its page in the book. The book shows how to open it.

CHAPTER 1

Everyday Science

Talk together

G01 · Everyday Science, Q001/Q004
Compare the floating ship and the floating ice. What is shared, and what needs a different explanation?

G02 · Everyday Science, Q005/Q006
Explain the difference between melting and dissolving using the pictures, without using the word disappear.

G03 · Everyday Science, Q010/Q011
Trace a sound on its way to a wall and back. Which part of the route creates the delay?

Sources for each question

Q001Why can a heavy ship float?

Density and Sinking and Floating — Teacher Background, American Chemical Society

Q002Why do things fall when we let go?

Newton’s Laws of Motion — 1. Force and Inertia, NASA Goddard Space Flight Center
What Is Microgravity? (Grades 5–8), NASA
Falling Object with Air Resistance, NASA Glenn Research Center

Q003Why does a sliding toy eventually stop?

College Physics 2e, 5.1 Friction, OpenStax, Rice University
Newton’s Laws of Motion — 1. Force and Inertia, NASA Goddard Space Flight Center

Q004Why does ice float on water?

Changing State—Freezing, American Chemical Society
Concepts of Biology, 2.2 Water, OpenStax, Rice University

Q005Why does an ice cube melt?

Changing State—Melting, American Chemical Society
Changing State—Freezing, American Chemical Society

Q006Where does sugar go when it dissolves?

Why Does Water Dissolve Sugar?, American Chemical Society

Q007Why are soap bubbles usually round?

The Shape of Bubbles, Exploratorium; Ron Hipschman
Soap, Exploratorium; Ron Hipschman
When Bubble Meets Bubble, Exploratorium; Ron Hipschman

Q008How does a rainbow appear in the sky?

College Physics 2e, 25.5 Dispersion: The Rainbow and Prisms, OpenStax, Rice University

Q009Why can we see ourselves in a mirror?

College Physics 2e, 25.2 The Law of Reflection, OpenStax, Rice University

Q010How does sound travel from one place to another?

College Physics 2e, 17.1 Sound, OpenStax, Rice University

Q011Why do we sometimes hear an echo?

Introduction to Behavioral Neuroscience, 7.1 Acoustic Cues and Signals, OpenStax, Rice University

Q012Why do magnets stick to some things but not others?

College Physics 2e, 22.2 Ferromagnets and Electromagnets, OpenStax, Rice University

Q013Why can a rubbed balloon make hair stand up?

The Great Electron Rip-off!, American Chemical Society

Q014Why do some metal objects rust?

Chemistry, 17.6 Corrosion, OpenStax, Rice University

Q015Why does popcorn pop?

The Secret Science of Popcorn, American Chemical Society

CHAPTER 2

Space and the Universe

Talk together

G04 · Space, Q016/Q026
Use the two diagrams to explain why an ordinary Moon phase is not the same as an eclipse.

G05 · Space, Q017/Q023
Compare the changes that make a day with those that make a year of seasons.

G06 · Space, Q029/Q030
Find one scientific question with an uncertain answer and one classification with written rules. How do they differ?

Sources for each question

Q016Why does the Moon seem to change shape?

Moon Phases, NASA Science
Eclipses and the Moon, NASA Science

Q017Why do day and night happen?

What Is Earth? (Grades 5–8), NASA
Chapter 2: Reference Systems, NASA, Basics of Space Flight

Q018Why does the Sun shine?

Sun Facts, NASA Science
(S-7) The Energy of the Sun, NASA Goddard Space Flight Center

Q019Why do stars look like tiny dots?

Astronomy, 18.3 Diameters of Stars, OpenStax, Rice University
Sun Facts, NASA Science
Astronomy 2e, 17.1 The Brightness of Stars, OpenStax, Rice University

Q020Why are the planets so different from one another?

Astronomy 2e, 14.3 Formation of the Solar System, OpenStax, Rice University
Astronomy, 11.2 The Giant Planets, OpenStax, Rice University
Solar System Temperatures, NASA Science

Q021Why does Saturn have rings?

Saturn Facts, NASA Science
StarChild: Saturn’s Cassini Division, NASA Goddard Space Flight Center
Saturn’s Rings: Young and Ephemeral, Three NASA Ames Studies Say, NASA Ames
Saturn’s rings age I: Reconsideration of exposure age, arXiv (research paper)

Q022Why do people see patterns in the stars?

The Constellations, International Astronomical Union (archive hosted by ESO)
What Are Constellations?, NASA Space Place

Q023Why do we have different seasons?

What Causes the Seasons?, NASA Space Place
Climate and Earth’s Energy Budget, NASA Earth Observatory
Fact sheet 16 — World climates, Met Office, National Meteorological Library and Archive
Our seasons, Met Office
Orbits and Kepler’s Laws, NASA Science

Q024Why do astronauts float inside a space station?

Q025How can a rocket move through space?

Chapter 3: Gravity & Mechanics, NASA, Basics of Space Flight
Solid Rocket Engine, NASA Glenn Research Center
Newton’s Laws of Motion — 1. Force and Inertia, NASA Goddard Space Flight Center

Q026Why do eclipses happen only sometimes?

Eclipses and the Moon, NASA Science
Eclipse Viewing Safety, NASA Science

Q027What makes a black hole different from other objects in space?

Black Holes, NASA Science

Q028How can looking into space show us the past?

What Is a Light-Year?, NASA Space Place
Astronomy, 6.1 Telescopes, OpenStax, Rice University

Q029Could living things exist somewhere beyond Earth?

The Search for Life: Are We Alone?, NASA Science
Can We Find Life?, NASA Science

Q030Why is Pluto called a dwarf planet?

Astronomy FAQs — Definition of a Planet, International Astronomical Union
IAU 2006 General Assembly: Result of the IAU Resolution votes, International Astronomical Union

CHAPTER 3

Earth, Weather and Oceans

Talk together

G07 · Earth, Q031/Q032
Follow water through two routes and explain why a cloud is more than invisible water vapor.

G08 · Earth, Q037/Q038
Compare the evidence for an earthquake with the explanation of an eruption. Which processes are connected?

G09 · Earth, Q036/Q045
Explain why one rainy day does not tell you whether a place usually has a desert climate.

Sources for each question

Q031How does water travel around our planet?

The Water Cycle, U.S. Geological Survey, Water Science School
Hydrologic Cycle, U.S. Geological Survey
Clouds, Met Office

Q032How can a cloud stay in the sky?

Terminal Velocity and the Collision/Coalescence Process, Plymouth State University, Meteorology
How Does a Cloud Rain?, University of Alaska Fairbanks, Geophysical Institute; Sue Ann Bowling
Clouds, Met Office
Rain, Met Office

Q033What makes the wind blow?

What are the different types of wind?, Met Office
Prevailing Winds, National Weather Service / NOAA
Introduction and Overview Topics, NOAA NSSL; Elizabeth Smith, Ph.D.

Q034Why do we see lightning before we hear thunder?

Understanding Lightning: Thunder, National Weather Service/NOAA
Lightning and Cars, National Weather Service
Lightning Safety, NOAA JetStream

Q035Why do snowflakes have such intricate shapes?

A Snowflake Primer, Kenneth G. Libbrecht, California Institute of Technology
Snow Crystal FAQs, Kenneth G. Libbrecht, California Institute of Technology

Q036How is climate different from today’s weather?

What’s the difference between climate and weather?, NOAA Climate.gov
United States Climate: Plot Description, NOAA Physical Sciences Laboratory
Understanding Climate Normals, NOAA

Q037Why does the ground shake during an earthquake?

The Science of Earthquakes, U.S. Geological Survey
Can you predict earthquakes?, U.S. Geological Survey

Q038Why do volcanoes erupt?

Volcanic Ash: Eruption Styles, U.S. Geological Survey
Volcano Watch — All in a Day’s Work: Determining magma storage depths at Kīlauea, U.S. Geological Survey, Hawaiian Volcano Observatory
Geology of Hawai’i Volcanoes National Park, U.S. Geological Survey
U.S. Geological Survey Circular 1249, U.S. Geological Survey

Q039How can mountains grow and wear away?

Parashant: A Boundary Between Geologic Provinces, National Park Service
Geology and Physical Processes — Mountains, National Park Service
Alaska Range and Mount McKinley: Geology and Orogeny, National Park Service
Our Dynamic Desert: Weathering and Erosion in Desert Environments, U.S. Geological Survey

Q040Why do rivers often bend instead of running straight?

Fluvial Features—Meandering Stream, National Park Service
NPS Geodiversity Atlas—Arkansas Post National Memorial, Arkansas, National Park Service

Q041Why is the ocean salty?

Why is the Ocean Salty?, USGS
Teek and Tom Educator’s Guide — Lesson 4, NOAA Ocean Today
Why is the ocean salty, but rivers flowing into it are not?, NOAA National Ocean Service

Q042Why does the sea rise and fall with the tides?

Tides, NASA Science
Are tides higher when the moon is directly overhead?, NOAA National Ocean Service

Q043How do waves move across the ocean?

What causes ocean waves?, NOAA Ocean Exploration
Lecture 2: Concepts from Linear Theory, Woods Hole Oceanographic Institution, GFD; Harvey Segur, notes by Alireza Mashayekhi and Michael Bates
Drifters, NOAA Ocean Exploration

Q044Why is the pressure so great deep in the ocean?

College Physics 2e — 11.3 Pressure, OpenStax / Rice University
College Physics 2e — 11.4 Variation of Pressure with Depth in a Fluid, OpenStax / Rice University
How does pressure change with ocean depth?, NOAA National Ocean Service
Pressure Testing of New Alvin Personnel Sphere Successful, Woods Hole Oceanographic Institution
How does pressure impact animals in the ocean?, NOAA Ocean Exploration

Q045Why do some places become deserts?

Types of Deserts, USGS
Antarctica, British Antarctic Survey

CHAPTER 4

Animals and Nature

Talk together

G10 · Nature, Q046/Q048
Follow the job of a leaf and the job of a flower. How do both support the plant differently?

G11 · Nature, Q050/Q051
Remove a decomposer from the pictured system. Name a possible consequence and something you would need to investigate.

G12 · Nature, Q053/Q054
Compare where a fish and a whale get oxygen. Explain why sharing an ocean does not make them the same kind of animal.

Sources for each question

Q046How do plants make their own food?

Biology 2e — 8.1 Overview of Photosynthesis, OpenStax / Rice University
The Science of Plants — 9.2 Seed Physiology, University of Minnesota Libraries
PRATT — Plant processes, North Carolina State University, Home Horticulture / DELTA

Q047How does a seed grow into a plant?

The Science of Plants — 9.2 Seed Physiology, University of Minnesota Libraries
Biology 2e — 32.2 Pollination and Fertilization, OpenStax / Rice University
Biology 2e — 8.1 Overview of Photosynthesis, OpenStax / Rice University

Q048Why do so many flowers attract bees?

Biology 2e — 32.2 Pollination and Fertilization, OpenStax / Rice University

Q049Why do some leaves change color in fall?

In Pictures: Autumn colour at Kew, Royal Botanic Gardens Kew
Development of fall foliage color in sugar maple, US Forest Service / Van den Berg et al.
Evergreen Perennials: The Greening of Winter, Penn State Extension
Leaf & Needle Drop, Clemson University Cooperative Extension, HGIC 2353

Q050Why are fungi important even when we barely notice them?

The wonderful world of fungi, Royal Botanic Gardens Kew

Q051What happens when one part of a food web changes?

Biology 2e — 46.1 Ecology of Ecosystems, OpenStax / Rice University
Biology 2e — 46.2 Energy Flow through Ecosystems, OpenStax / Rice University
Grasshopper Sparrow Overview, Cornell Lab of Ornithology
Food Habits of the Red Fox in Nebraska, Nebraska Academy of Sciences; University of Nebraska–Lincoln repository; Douglas G. Powell and Ronald M. Case

Q052How do birds stay in the air?

Bernoulli and Newton, NASA Glenn Research Center
Bird Academy’s A-to-Z Glossary of Bird Terms, Cornell Lab of Ornithology
Species Profile: Swainson’s Hawk, Smithsonian National Zoo
Habitat of Flight, Smithsonian Gardens

Q053How do fish breathe underwater?

Biology 2e — 39.1 Systems of Gas Exchange, OpenStax / Rice University
How do fish breathe?, Washington State University, Ask Dr. Universe
The Silver King: The prehistoric fish that can breathe air, Smithsonian Ocean
Dynamic elastocapillary coalescence of fish gill lamellae, Research article; PubMed Central, NIH/NLM
Evaluating the Air Respiratory Capacity of Awaous (Chonophorus) tajasica (Gobiiformes: Oxudercidae): A Morpho-Functional Study, Trevisan et al.; Journal of Experimental Zoology Part A, Wiley; copia PMC

Q054Why is a whale a mammal instead of a fish?

Whales and Dolphins, Smithsonian Ocean

Q055How does camouflage help an animal survive?

Species variation game: peppered moth lucky landing, Natural History Museum, London
Can you spot the hidden animals that use cunning camouflage?, Natural History Museum, London
Predators hide against similarly coloured species to camouflage on the move, Matchette et al.; Proceedings of the Royal Society B; repository University of Cambridge
Dichromats detect colour-camouflaged objects that are not detected by trichromats, M. J. Morgan, A. Adam, J. D. Mollon; Proceedings of the Royal Society of London B 248 (1992), 291–295; copia University of Cambridge

Q056Why do some animals migrate?

Monarch Migration in the Southeast, US Fish and Wildlife Service
Continental Nomads: Monarch Butterflies, National Park Service
Monarch Butterfly Habitat Needs, USDA Forest Service

Q057How can some animals get through winter by hibernating?

Arctic Ground Squirrel, National Park Service, Denali
Biological clocks: Where arctic ground squirrels meet ’social jet lag’, University of Alaska Anchorage
Cardiac Rhythms and Variation in Hibernating Arctic Ground Squirrels, Physiological and Biochemical Zoology 96(3), University of Chicago Press; ricercatori University of Alaska Fairbanks
Freeze avoidance in a mammal: body temperatures below 0 degrees C in an Arctic hibernator, Science (Barnes, 1989)
Arctic ground squirrels are supercooled, University of Alaska Fairbanks

Q058How does a caterpillar become a butterfly?

Metamorphosis: The Life Stages of a Monarch Butterfly on Milkweed in North East, Maryland (FS-1144), University of Maryland Extension
About Butterflies, Smithsonian Gardens
Science Says So: How Do Caterpillars Get Their Wings?, Marine Biological Laboratory
Monarch Butterflies Make the Most of the Smithsonian’s Gardens, Smithsonian Institution

Q059How can an ant colony work together?

The Collective Wisdom of Ants, Deborah M. Gordon / Scientific American; Stanford University author-hosted copy
ENY203/IG080: Ants, University of Florida IFAS Extension

Q060Why does having many different living things matter?

What Is Biodiversity?, American Museum of Natural History
High diversity stabilizes the thermal resilience of pollinator communities in intensively managed grasslands, Kühsel & Blüthgen / Nature Communications 6, 7989 (2015)
Biology 2e — 46.1 Ecology of Ecosystems, OpenStax / Rice University

CHAPTER 5

The Human Body and Brain

Talk together

G13 · Body, Q062/Q069
Follow nutrients from a meal toward the body’s transport system. Where do the two diagrams connect?

G14 · Body, Q063/Q067
Choose one body diagram and explain which arrows show matter moving and which show information moving.

G15 · Body, Q073/Q074
Recall a time when new information changed your interpretation. Share only what each person feels comfortable discussing.

Sources for each question

Q061Why do we have a skeleton inside our bodies?

What Is Bone?, NIAMS / NIH

Q062What happens to food after we swallow it?

Your Digestive System & How it Works, NIDDK / NIH

Q063Why do we need to breathe?

How the Lungs Work — The Respiratory System, NHLBI / NIH
Biology 2e — 39.1 Systems of Gas Exchange, OpenStax / Rice University
Anatomy and Physiology 2e — 22.4 Gas Exchange, OpenStax / Rice University
Anatomy and Physiology — Respiratory, University of Hawai‘i OER

Q064How do muscles move our bodies?

Anatomy and Physiology 2e — 11.1 Interactions of Skeletal Muscles, Their Fascicle Arrangement, and Their Lever Systems, OpenStax / Rice University
Anatomy and Physiology 2e — 10.3 Muscle Fiber Contraction and Relaxation, OpenStax / Rice University
Anatomy and Physiology 2e — 10.4 Nervous System Control of Muscle Tension, OpenStax / Rice University
Anatomy and Physiology 2e — 10.8 Smooth Muscle, OpenStax / Rice University
What Makes You Move?, RockEDU / The Rockefeller University

Q065Why do we sweat when we get hot?

Anatomy and Physiology 2e — 5.3 Functions of the Integumentary System, OpenStax / Rice University
It’s the Heat AND Humidity, NOAA National Weather Service, Fort Worth

Q066How do our eyes turn light into what we see?

How the Eyes Work, National Eye Institute / NIH
Psychology 2e — 5.3 Vision, OpenStax / Rice University
College Physics 2e — 26.1 Physics of the Eye, OpenStax / Rice University

Q067How do our ears turn vibrations into hearing?

How Do We Hear?, NIDCD / NIH
Hearing Aids, NIDCD / NIH
College Physics 2e — 17.6 Hearing, OpenStax / Rice University

Q068Why do children lose their baby teeth?

Open Wide and Trek Inside! — Full Teacher’s Guide, NIDCR / NIH; BSCS and Videodiscovery
Eruption Charts, American Dental Association / MouthHealthy
Analytical electron microscopy and ultracytochemistry of a mechanism of dentine resorption mediated by odontoclasts in physiological root resorption of human deciduous teeth, Nobuo Motegi / Japanese Association for Oral Biology

Q069Why does the heart keep beating?

How the Heart Works — How the Heart Beats, NHLBI / NIH
How the Heart Works — How Blood Flows through the Heart, NHLBI / NIH
Anatomy and Physiology 2e — 18.1 An Overview of Blood, OpenStax / Rice University

Q070How does skin repair a small cut?

Health Lesson: Learning About Skin, NIAMS / NIH
How wounds heal, MedlinePlus / US National Library of Medicine
Assessment of microcirculation dynamics during cutaneous wound healing phases in vivo using optical microangiography, Journal of Biomedical Optics; primary study hosted by PMC / NLM

Q071How does the body defend itself against germs?

What Is the Immune System?, NIGMS / NIH
Anatomy and Physiology 2e — 5.3 Functions of the Integumentary System, OpenStax / Rice University
Microbiome, NIEHS / NIH

Q072Why do we need sleep?

How Sleep Works — Why Is Sleep Important?, NHLBI / NIH
How Sleep Works — Sleep Phases and Stages, NHLBI / NIH
How Sleep Works — Your Sleep/Wake Cycle, NHLBI / NIH
Understanding Sleep, NINDS / NIH
Psychology 2e — 4.3 Stages of Sleep, OpenStax / Rice University
From high- to low-density EEG for automatic classification of dream experiences during stage 2 of NREM, Moctezuma, Molinas & Abe / SLEEP Advances, Oxford University Press

Q073How does practice help us remember something?

Psychology 2e — 8.4 Ways to Enhance Memory, OpenStax / Rice University
Retrieval practice facilitates learning by strengthening processing in both the anterior and posterior hippocampus, Brain and Behavior; primary study hosted by PMC / NLM
Distinct kinetics of synaptic structural plasticity, memory formation, and memory decay in massed and spaced learning, PNAS; primary study hosted by PMC / NLM
How Sleep Works — Why Is Sleep Important?, NHLBI / NIH
Psychology 2e — 8.2 Parts of the Brain Involved with Memory, OpenStax / Rice University
Psychology 2e — 8.3 Problems with Memory, OpenStax / Rice University

Q074Why can feelings change so quickly?

Psychology 2e — 10.4 Emotion, OpenStax / Rice University

Q075Why do family members sometimes look alike?

What is a gene?, MedlinePlus Genetics / NLM
Polygenic Trait, NHGRI / NIH
Is height determined by genetics?, MedlinePlus Genetics / NLM

CHAPTER 6

Technology and Inventions

Talk together

G16 · Technology, Q076/Q078
Compare two devices powered by a circuit. How do their useful outputs differ?

G17 · Technology, Q081/Q082
Follow a message through a network and compare that journey with a program following its instructions.

G18 · Technology, Q084/Q090
Compare a useful technology with one of its limitations. What would you check before making a big claim about it?

Sources for each question

Q076How does a light bulb turn electricity into light?

The History of the Light Bulb, US Department of Energy
NIST Researchers Boost Intensity of Nanowire LEDs, NIST
LED Basics, US Department of Energy
LED Lighting May Now Shine Brighter, US Department of Energy
DOE Explains...Batteries, US Department of Energy
GPIO Pins — ECE353: Introduction to Microprocessor Systems, University of Wisconsin–Madison, Electrical and Computer Engineering
College Physics 2e — 20.1 Current, OpenStax / Rice University

Q077How can a battery power a toy?

DOE Explains...Batteries, US Department of Energy

Q078How does an electric motor make something spin?

College Physics 2e — 22.8 Torque on a Current Loop: Motors and Meters, OpenStax / Rice University
Brushed DC Motor Theory, Northwestern University, Mechatronics

Q079Why does pedaling a bicycle turn its back wheel?

Science of Cycling: History of Drives & Gears, Exploratorium
College Physics 2e — 7.5 Nonconservative Forces, OpenStax / Rice University

Q080How can an airplane stay in the air?

Bernoulli and Newton, NASA Glenn Research Center
Airplane Cruise — Balanced Forces, NASA Glenn Research Center
Forces in a Climb, NASA Glenn Research Center
Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25C, Federal Aviation Administration

Q081What happens when we send a message over the internet?

A Brief History of the Internet, Internet Society; Leiner, Cerf, Clark, Kahn et al.
RFC 5321: Simple Mail Transfer Protocol, Internet Engineering Task Force
What Is Wi-Fi?, Cisco
If you can’t connect to Wi-Fi on your iPhone or iPad, Apple Support

Q082How does a computer follow instructions?

Programming Languages: What’s the big picture?, Computer Science Education Research Group, University of Canterbury

Q083How does a touchscreen know where we touch?

Capacitive Touch Technology Opens the Door to a new Generation of Automotive User Interfaces, Microchip / Atmel

Q084Why can an AI give a confident answer that is wrong?

Artificial Intelligence Risk Management Framework: Generative Artificial Intelligence Profile, NIST
Emperor penguin, Australian Antarctic Program

Q085How can a phone work out where it is?

Trilateration, GPS.gov
The Global Positioning System: Global Positioning Tutorial, NOAA National Ocean Service
GPS Accuracy, GPS.gov
How Location Accuracy improves location, Google, Android Help
iPhone 17 — Technical Specifications, Apple

Q086How can a bridge hold so much weight?

Build a Bridge, PBS NOVA
Bridge Basics: Truss Bridge Forces, PBS / WGBH

Q087How does a refrigerator keep food cold?

University Physics Volume 2, 4.3 Refrigerators and Heat Pumps, OpenStax, Rice University
Refrigeration, Australian Government, energy.gov.au

Q088How does clean water reach a faucet?

How Water Treatment Works, US Centers for Disease Control and Prevention
Drinking Water Distribution System Tools and Resources, US Environmental Protection Agency
DC Water Builds First Water Tower Since 1945, DC Water
About Choosing Home Water Filters, Centers for Disease Control and Prevention
New or Repaired Water Mains, American Water Works Association and Economic and Engineering Services (hosted by US EPA)

Q089What happens to a plastic bottle put out for recycling?

How Do I Recycle Common Recyclables, US Environmental Protection Agency
PET Is the Most Widely Recycled Plastic in the World, NAPCOR (PET industry association)
Products Made from Recycled PET, NAPCOR (PET industry association)

Q090How do solar panels turn sunlight into electricity?

Solar Photovoltaic Cell Basics, US Department of Energy
How Does Solar Work?, U.S. Department of Energy
Solar Integration: Solar Energy and Storage Basics, U.S. Department of Energy

CHAPTER 7

Dinosaurs and Deep Time

Talk together

G19 · Deep Time, Q091/Q092
Explain the difference between preserving a fossil and finding evidence for its age.

G20 · Deep Time, Q096/Q104
Compare the time bar and the mammal examples. What evidence shows that some mammals lived alongside dinosaurs?

G21 · Deep Time, Q100/Q101
Separate what is observed, what is inferred, and what is still unknown in one reconstruction.

Sources for each question

Q091How can a living thing become a fossil?

How are dinosaur fossils formed?, Natural History Museum, London

Q092How do scientists work out how old a fossil is?

Volcanoes and Fossils, US National Park Service
Radiometric Age Dating, US National Park Service
Geologic Principles—Superposition and Original Horizontality, US National Park Service

Q093Why can rock layers tell a story about the past?

Geologic Principles—Superposition and Original Horizontality, US National Park Service
Geology — Capitol Reef National Park, US National Park Service
Missing Time at Grand Canyon National Park, US National Park Service; Karlstrom, Crossey, Mathis and Bowman

Q094What makes an animal a dinosaur?

The Dinosaurs on Display, American Museum of Natural History
What are dinosaurs?, Natural History Museum, London

Q095How do we know that birds are living dinosaurs?

Get to Know a Dino: Velociraptor, American Museum of Natural History
What are dinosaurs?, Natural History Museum, London
The Dinosaurs on Display, American Museum of Natural History

Q096Did all dinosaurs live at the same time?

Coelophysis, Natural History Museum, London
Stegosaurus, Natural History Museum, London
Tyrannosaurus, Natural History Museum, London

Q097How could some dinosaurs grow so enormous?

Why were dinosaurs so big? The secrets of titanosaurs’ super size, Natural History Museum, London
Beyond Jurassic World: What we really know about dinosaurs and how, Natural History Museum; Paul Barrett and Lisa Hendry

Q098How can fossil teeth reveal what an animal ate?

Beyond Jurassic World: What we really know about dinosaurs and how, Natural History Museum; Paul Barrett and Lisa Hendry

Q099What can dinosaur footprints tell us?

Footprints to Fossils, US National Park Service, Zion
Another Kind of Bigfoot, US National Park Service, Zion
Beyond Jurassic World: What we really know about dinosaurs and how, Natural History Museum; Paul Barrett and Lisa Hendry
Dinosaur footprints: how do they form and what can they tell us?, Natural History Museum, London; Emily Osterloff

Q100Can fossils tell us what colors dinosaurs were?

Sinosauropteryx, Natural History Museum, London
How do we know what colour dinosaur feathers were?, University of Bristol
Blue colour tones in fossilised prehistoric feathers, University of Bristol

Q101Can we know what dinosaurs sounded like?

Scientists Use Digital Paleontology to Produce Voice of Parasaurolophus Dinosaur, Sandia National Laboratories / New Mexico Museum of Natural History and Science
What did Diplodocus sound like?, Natural History Museum, London

Q102Why are similar fossils found on continents far apart?

A searchable database of the Earth Experience Museum fossil collection, Earth Experience Museum
Historical Geology, 22.2: Continental drift, OpenGeology / LibreTexts; Callan Bentley et al.

Q103Why did the non-bird dinosaurs disappear?

What killed the dinosaurs?, Natural History Museum, London
How an asteroid ended the age of the dinosaurs, Natural History Museum, London; intervista a Paul Barrett

Q104Were mammals already around when dinosaurs ruled the land?

The World in Which They Lived, American Museum of Natural History
The Triassic Period: the rise of the dinosaurs, Natural History Museum, London
What killed the dinosaurs?, Natural History Museum, London
Large Mesozoic mammals fed on young dinosaurs, Nature (Hu et al., 2005)

Q105How can living things change over many generations?

Natural Selection, UC Museum of Paleontology, University of California Berkeley
Biology 2e, 19.1 Population Evolution, OpenStax, Rice University

CHAPTER 8

People, History and Our World

Talk together

G22 · People, Q110/Q114
Compare a rule and a tradition. How might people discuss changing each one?

G23 · People, Q111/Q117
Imagine making a museum label for an object. Include what you know, how you know it, and what you do not know.

G24 · People, Q119/Q120
Compare two accounts of a harmless event. Identify an outside source that could help check a specific claim.

Sources for each question

Q106Why are there so many different languages?

Introduction to Anthropology, 6.3 Language, Community, and Culture, OpenStax, Rice University
Penn Linguists Investigate Language Borrowing in the Field and the Lab, University of Pennsylvania
Education in a multilingual world: UNESCO education position paper, UNESCO
Promoting Literacy in Multilingual Settings, UNESCO Bangkok; Kimmo Kosonen, Catherine Young, Susan Malone

Q107Why did people invent writing?

How Egyptian hieroglyphs were decoded, a timeline to decipherment, British Museum
Introduction to Anthropology, 6.3 Language, Community, and Culture, OpenStax, Rice University
How to write cuneiform, British Museum; Irving Finkel
American Sign Language, National Institutes of Health, NIDCD
Oral traditions and expressions including language as a vehicle of the intangible cultural heritage, UNESCO, Intangible Cultural Heritage
Introduction to Maya Hieroglyphs, Mesoweb (Kettunen and Helmke, 2020)

Q108Why do we need a symbol for zero?

A history of Zero, MacTutor History of Mathematics, University of St Andrews

Q109Why do people use money?

Money and Inflation: A Functional Relationship, Federal Reserve Bank of St Louis; Scott A. Wolla
Can’t We Just Print More Money? — Worksheet for Lesson Five: Narrative Writing, Bank of England

Q110Why do communities make rules?

If children participate in making the rules, they are less likely to break them!, UNICEF MENA

Q111How do archaeologists learn about people who lived long ago?

Tab.Vindol. 291. Birthday Invitation of Sulpicia Lepidina, Roman Inscriptions of Britain, scholarly edition
The Vindolanda tablets, British Museum
How are dinosaur fossils formed?, Natural History Museum, London
What to Know When Visiting an Archaeological Site, Society for American Archaeology

Q112How were the ancient Egyptian pyramids built?

Les papyrus de la mer Rouge I: Le journal de Merer, Annexe I, Institut français d’archéologie orientale; Pierre Tallet, trad. Colin Clement
The Lost City of the Pyramids (Heit el-Ghurab), Ancient Egypt Research Associates
The Great Pyramid Quarry, Ancient Egypt Research Associates
Stories from the Stones, Ancient Egypt Research Associates; Sabine Boos

Q113Why do cities grow in some places?

A timeline of Roman London: Londinium from start to end, London Museum
Brasilia, UNESCO World Heritage Centre

Q114Why do people celebrate in different ways?

Novruz, Nowrouz, Nooruz, Navruz, Nauroz, Nevruz, UNESCO Intangible Cultural Heritage
Traditions and Change: The Transformation of Día de los Muertos in the United States, Smithsonian American Art Museum
International Day of Nowruz, UNESCO

Q115Why isn’t it the same time everywhere on Earth?

Local Time FAQs, NIST

Q116Why can a flat map make places look different from a globe?

G.Projector 3 — List of Map Projections, NASA Goddard Institute for Space Studies
Mercator — ArcGIS Pro documentation, Esri
Mollweide — ArcGIS Pro documentation, Esri
This animated map shows the true size of each country, Nature Index

Q117How do museums decide what to show us?

Research, Smithsonian National Museum of the American Indian
History of the Collections, Smithsonian National Museum of the American Indian
Repatriation, Smithsonian National Museum of the American Indian

Q118Why do people carry ideas and foods from place to place?

The origins and adaptation of European potatoes reconstructed from historical genomes, International Potato Center; Gutaker et al., Nature Ecology & Evolution (2019)
Learning to love the potato, Europeana, mostra Edible plants from the Americas
Native Potato Varieties, International Potato Center (CIP)
The potato’s travel through ages and continents, Food and Agriculture Organization of the United Nations
The Great Inka Road: Engineering an Empire — Invasion: Impact, Smithsonian National Museum of the American Indian

Q119How can people tell different stories about the same event?

Psychology 2e, 8.3 Problems with Memory, OpenStax, Rice University
Untangling media messages and public policies, UC Museum of Paleontology, University of California Berkeley

Q120How can we decide whether an amazing claim is true?

Untangling media messages and public policies, UC Museum of Paleontology, University of California Berkeley
Understanding Science 101, UC Museum of Paleontology, University of California Berkeley
Biology 2e, 1.1 The Science of Biology, OpenStax, Rice University; Clark, Douglas and Choi
Introductory Statistics 2e, 1.4 Experimental Design and Ethics, OpenStax, Rice University; Barbara Illowsky and Susan Dean

About the sources

The answers in the book were written with the help of AI tools and checked against the published sources listed here: science agencies, museums, universities, and journals. They have not been reviewed by an independent scientist. Science keeps moving, so if a source has been updated since September 2026, the newer information wins.

Links were checked in September 2026; websites can move or change. Some sites block automatic checks, so a few links may need to be opened by hand.

Typefaces: Andika and Baloo 2, used under the SIL Open Font License.