How can people on different sides of Earth all have objects fall down?
Submit: A three-location model and evidence-based explanation.
Related lesson: Stars and the Solar System
This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.
Teacher review guideBuild the idea
Earth attracts objects toward its center. “Down” is a local direction: it points inward toward Earth’s center, not toward the bottom of every drawing. People at different surface positions have different inward arrows. A globe model helps distinguish the force direction from the flat page’s orientation.
Science / engineering practice
Argument from evidenceCore idea
Earth’s gravitational force points toward its centerCrosscutting concept
Cause and effectEvidence and model inputs
Observation to collect: from a low height, an adult releases a soft object without throwing it; it moves toward the ground. Model evidence: on a drawn round Earth, a surface-to-center arrow at the top, bottom and side of the circle points in different directions on the paper while representing local down in each place.
Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.
Materials and preparation
Globe or circle drawing, soft large object, low safe release area and paper. No climbing or dropping objects near people.
Grade-level scope
Do not require a mathematical gravitational-force equation at this grade.
Do the work
- Record a safe release observation. Distinguish the object’s location from the direction of Earth’s pull.
- Draw Earth as a circle and mark three people at well-separated surface positions.
- Draw a down arrow from each person toward the center and an up arrow away from the center.
- Rotate the paper. Explain why the page’s bottom is not the definition of down.
- Present an argument connecting the observation and model, and describe why a classroom release alone does not observe every place on Earth.
Learner worksheet
Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.
Check your reasoning
- Where should the arrow at the bottom of the drawn Earth point?
- Does gravity switch off when an object rests on the ground?
- Why is “down is south” incorrect?
- What is the model’s limitation?
Teacher review guide
Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.
- Makes the claim that Earth’s gravitational pull is locally downward.
- Draws consistent inward arrows at multiple surface positions.
- Connects observations and the model to the claim.
- Distinguishes the model from the page orientation and states a limitation.
Answer guidance for the reasoning checks
Where should the arrow at the bottom of the drawn Earth point?
Upward on the page, toward the center; that is local down there.
Does gravity switch off when an object rests on the ground?
No. Earth still pulls; the ground also exerts a supporting force.
Why is “down is south” incorrect?
South is a surface direction; down points inward toward Earth’s center.
What is the model’s limitation?
A flat drawing simplifies a three-dimensional Earth and does not show every force or motion.
Access, support and extension
Offer read-aloud support, labeled diagrams, larger print or an oral/recorded explanation while preserving the scientific reasoning. A partner or teacher can handle physical manipulation while the learner plans, records and interprets. Use a teacher-provided measured dataset only when its provenance and limitations are explicit; it does not replace conducting an investigation when that is the assessed practice. For greater independence, remove prompts and ask learners to compare a second explanation or test another justified revision.
Sources and standard reference
- Official NGSS 5-PS2-1 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.
Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.