How Astronomers Know
Evidence Lab
Short investigations where you look at real data or a model and figure out what it means. Each investigation includes hints, immediate feedback and an explanation of what scientists can — and cannot — conclude from the evidence.
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Grades 3–5
6 investigationsMoon Pattern Detective
~12 minThe Moon looks different from night to night — can you figure out the pattern?
Aligned to 5-ESS1-2
Compare the Planets
~10 minHow do the planets in our solar system stack up in size?
Aligned to 5-ESS1-1
Crater Counter
~10 minTwo Moon regions look very different. How can crater counts tell us which one is older?
Aligned to 5-ESS1-2
Shadow Tracker
~12 minWhy does your shadow look tiny at noon and long in the afternoon?
Aligned to 5-ESS1-2
Day and Night Model
~10 minWhy does the Sun rise and set every day, even though it does not actually move around Earth?
Aligned to 5-ESS1-2
Why Do Stars Have Different Brightness?
~12 minSome stars look bright and some look dim. Is it because they are actually different, or because they are at different distances?
Aligned to 5-ESS1-1
Grades 6–8
6 investigationsMoon Phases from Sun–Earth–Moon Geometry
~20 minEach Moon phase corresponds to a specific arrangement of Sun, Earth and Moon. Can you match them?
Aligned to MS-ESS1-1
Scale of the Solar System
~18 minIf Earth were the size of a marble, how far away would Neptune be?
Aligned to MS-ESS1-3
Gravity Keeps Worlds in Orbit
~18 minMercury zips around the Sun at 47 km/s. Neptune crawls at 5.4 km/s. Why the huge difference?
Aligned to MS-ESS1-2
Finding an Exoplanet with a Transit Light Curve
~20 minHow can astronomers detect a planet around another star that they cannot see directly?
Aligned to MS-ESS1-2
Life Cycle of a Star
~20 minStars are born, live, and die. What decides how they end their lives?
Aligned to MS-ESS1-2
Reading a Star Spectrum
~20 minEvery star gives off a rainbow with specific dark lines. Why do those lines matter?
Aligned to MS-ESS1-2
Grades 9–12
6 investigationsStellar Lifetime from Mass
~30 minMassive stars burn brightly but briefly. Low-mass stars can last longer than the current age of the universe. What controls the difference?
Aligned to HS-ESS1-1
Evidence for the Big Bang
~35 minThe Big Bang model is not accepted because of one crucial experiment — it survives because independent lines of evidence all point the same way.
Aligned to HS-ESS1-2
Stellar Spectra and Chemical Composition
~30 minHow can astronomers know a star's composition without ever collecting a sample from it?
Aligned to HS-ESS1-3
Galaxy Redshift and an Expanding Universe
~30 minHubble's plot of distance vs. recession speed changed cosmology forever. What can you read off a modern version of it?
Aligned to HS-ESS1-2
Stellar Mass, Life Cycle and Element Formation
~30 minThe atoms in your body were made in stars — but not all in the same kind of star. Where does each element come from?
Aligned to HS-ESS1-3
Modeling an Orbit with Mathematics
~30 minKepler's third law says the square of a planet's orbital period equals the cube of its semi-major axis. Can you use it to predict a planet's year?
Aligned to HS-ESS1-4
Every investigation cites the original NASA source used to write it. Nothing you type in a CER response leaves this device.
For teachers & parents — Evidence Lab
A one-page guide with objectives, standards, materials, prompts and accommodations. Everything on this page can be printed.
Estimated time
10–30 minutes per investigation.
Learning objectives
- Interpret evidence rather than memorize facts.
- Distinguish what the evidence supports from what it does not support.
- Use multi-step reasoning that includes claim, evidence, and reasoning.
Standards addressed
- 5-ESS1-1 / 5-ESS1-2 (Grades 3–5)
- MS-ESS1-1 / MS-ESS1-2 / MS-ESS1-3 (Grades 6–8)
- HS-ESS1-1 / HS-ESS1-2 / HS-ESS1-3 / HS-ESS1-4 (Grades 9–12)
Materials
- Optional: printer for the completion summary.
- Scratch paper for calculations.
Answer guidance
- Every question has an explanation and a 'What scientists conclude' statement.
- Where relevant, a 'What this does not prove' note is included to guard against overreach.
- Numeric tolerance is set per grade — younger grades are more forgiving.
Discussion prompts
- What evidence changed your mind while working through this investigation?
- How could this evidence be wrong? What would you check next?
- Could someone use this same evidence to reach a different conclusion?
Accommodations
- Hints are hidden by default for the last grade in each band — enable them for students who need scaffolding.
- Charts always include an accessible data table so students using screen readers can complete the same activity.
- For CER responses, allow voice-to-text; nothing is scored automatically.
What is stored locally
Everything is stored only in this browser. No student name, email, school, age, precise location, sketches, or free-text responses ever leave the device.