Which mountain is tallest?

Lesson: Before comparing answers, check what each answer measures.

Provenance: AI-assisted RS Learning Lab teaching example, researched and drafted in Codex with web search on 2026-09-10. The prompts, first draft, and reflection below are constructed teaching material, not a transcript of a learner session. Sources were opened for this walkthrough; classroom timing and learner responses have not been piloted. This develops the measurement question in Reality Check's illustrative field note without treating that note as an observed AI interaction.

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1. Start with the question

Ask this before revealing the comparison:

Which mountain is tallest?

Invite a first answer and a reason. Someone may name Everest; someone may remember a mountain that begins underwater. Keep both on the board. Ask people to sketch where their measurement would start and end.

Then ask: Are we measuring the same thing?

2. Give AI one useful job

Use a conversational AI tool with web search and source links to help uncover possible meanings of the question. Open its sources yourself. With a conversation-only tool, supply the source excerpts and links from step 4 and ask it to compare them.

First prompt to try live:

Which mountain is tallest? Give me a short answer and explain what you are measuring. Link a source I can open to check it.

Let the group inspect the actual response. Did it name a starting point? Did it offer alternatives? If it already explains the distinctions, follow one of them; there is no need to manufacture an error.

A facilitator or partner can operate the tool while learners choose the follow-up. The prepared walkthrough supports that live encounter.

3. Notice the hidden condition

Constructed first draft for discussion:

Mount Everest is the tallest mountain on Earth.

Ask what would make this precise. A familiar answer can leave a measurement unstated. Adding a condition may be more useful than replacing one mountain's name with another.

Follow-up prompt:

Compare height above mean sea level, height from a mountain's base to its summit, and distance from Earth's center to its summit. For each, name the starting point, the mountain identified by your source, and the evidence link. Include underwater terrain. Keep approximate measurements approximate.

Choose which part to investigate first. The AI can organize the comparison; the group decides whether the sources support it.

4. Check the measurement against sources

Open NOAA's highest-point comparison. Locate the paragraph for each mountain and check that it uses the measurement in the first column.

Scroll sideways to see all columns.

Question we are answering	Mountain	What the measurement includes
Which summit is highest above global mean sea level?	Mount Everest	Elevation relative to mean sea level: about 8.85 km.
Which is tallest from base to summit in NOAA's comparison?	Mauna Kea, Hawaiʻi	The submerged part as well as the part above water: about 10.2 km in total. USGS explicitly locates the base at the ocean floor; see the source check below.
Which summit is farthest from Earth's center?	Chimborazo, Ecuador	Distance from the planet's center. Earth's equatorial bulge gives this near-equatorial summit a different starting advantage.

For the underwater branch, open USGS: How big are the Hawaiian volcanoes?. NOAA describes an origin beneath the Pacific and a base-to-peak height; USGS explicitly identifies the ocean floor and places roughly 4.2 km above sea level and about 6 km below it. Add those rounded parts. Does the total fit the comparison? The sources support the comparison at different levels of detail; this is a check of attribution, not a factual disagreement.

Sketch a sea-level line across the mountain and mark both parts. Label the drawing schematic, not to scale. For the Earth-center question, make a separate sketch: a slightly flattened globe with a center point and two summit positions. Exaggerate the shape only to make the idea visible, and label that choice.

Do not compare a center-to-summit distance with a base-to-summit height as though both start at the same place. If AI generates a diagram, check its labels and geometry against your source before using it to explain the answer.

5. Revise one claim

Constructed claim to inspect:

Mauna Kea is the real tallest mountain, so Everest is the wrong answer.

Underline “real” and “wrong.” What measurement would make each part defensible? Rewrite the statement with its starting point attached. Use the comparison board to check the revision.

Then ask the AI:

Read our revised sentence. Have we stated the measurement, or quietly switched it? Point to any wording that our linked source does not support. Suggest a clearer version for us to judge.

Keep, change, or reject the suggestion. The source check and the wording decision belong to the learners.

A useful next question is where does a mountain's base begin? This walkthrough uses NOAA's base-to-peak comparison with the ocean-floor description supplied by USGS. It does not settle every possible definition of a mountain's base. Choose that as a further investigation if it interests the group.

6. Decide what changed and where to go next

Modeled reflection, not a recorded learner response:

I started by looking for one name. Now I would ask where the measurement starts. AI helped me separate the questions; opening the sources let me check the distinction. I still want to know how people measure a mountain below the ocean.

Invite each learner to say, write, or draw their own change in understanding. They can also explain why their first answer still fits the measurement they intended.

Possible next questions:

• How do researchers map a mountain's underwater base?
• How do we measure elevation for a mountain far from the sea?
• Why does Earth bulge at the equator?
• What would we need to specify before asking for the largest mountain?

Choose one branch or stop here. Explaining the measurement in your own words is a useful result; there is no requirement to exhaust the topic.

Use this as an opening demonstration

Invite first answers, run one live prompt, let the group choose a measurement to check, open one source, and revise one sentence together. Keep the full comparison available for questions.

Before the session, review both walkthroughs in the 📎 Resource · Gallery. At the opening of the session, let the class vote between this question and refrigeration, then choose a branch. This example opens a conversation about definitions and measurements; refrigeration opens one about place, time, and access.

Source notes

Sources checked on 2026-09-10; attribution rechecked on 2026-09-11:

• NOAA National Ocean Service, highest-point comparison, linked in step 4. Agency educational explanation of the three measurements, with an infographic transcript. The page displays an older Everest figure; this walkthrough uses rounded values because the lesson does not require survey precision.
• USGS, How big are the Hawaiian volcanoes?, linked in step 4. Agency explanation supporting the underwater/above-water breakdown. Its rounded quantities are suitable for the comparison, not for a precise survey calculation.

These are agency summaries, not original survey datasets. A follow-up about exact heights, reference surfaces, or changing measurements needs the relevant survey evidence. No generated answer or illustrative field note serves as an independent factual source here.