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What's the Tallest Mountain On Earth?

If, like most everyone else, you answered, "Mount Everest," then you are not quite right. But you are not quite wrong, either.

The real answer has to do with a concept I wrote about in an earlier blog post. Scientists can all objectively agree where mountains "finish". That is, it's extremely hard to argue about where a mountain "peaks". But when measuring, we know that "finished" is only half the battle. Agreeing where a mountain "starts" is a whole other conversation altogether -- and not nearly as straightforward as it may sound.

For example, more than half of the Mauna Kea volcano in Hawaii is underwater. Only 4,205 meters of the whole mountain is above sea level. But if we measure from the base to the summit of Mauna Kea, it is 10,211 meters -- that's about 20% taller than Everest's 8,848 meters. If you only want to talk about mountains on land, then, base-to-summit, Denali in Alaska is actually taller (5,900m) than Everest base-to-summit (4,650m).

So why does Everest get the crown? The reason is that most scientists choose to start their measurements of mountain heights from a concept known as sea level. But the problem with sea level is that anyone who has studied geography knows that the sea ain't so level. The physics of the earth are such that different densities of the earth's makeup at different locations cause different gravitational pulls resulting in "hills and valleys" of sea level across the planet (the European Space Agency has an outstanding visualization of this)

Add to that things like tides, storms, wind, and a bulge around the equator due to the earth's rotation means there is no one true level for the sea. Scientists cheat to solve this problem by calculating a "mean" (arithmetic mean or average) sea level. This "average" sea level represents the zero starting point at which all land mountains are measured (cue the "Flaw of Averages").

You might ask, why don't we choose a more rigorous starting point like the center of the earth? The reason for that is... remember that bulge around the equator that I just alluded to? The earth itself is not quite spherical, and the distance from its center at the equator is longer than the distance from the center to either the north or south pole. In case you were wondering, if we were to measure from the center of the earth, then Mount Chimborazo in Ecuador would win.

It seems that geologists fall prey to the same syndrome that afflicts most Agile methodologies. A bias toward defining only when something is "done" ignores half of the equation -- and the crucial half at that. What's more, you have Agilists out there who actively rant against any notion of a defined "start" or "ready". What I hope to have proven here is that, in many instances, deciding where to start can be a much more difficult (and usually much more important) problem to solve, depending on what question you are trying to solve.

At the risk of repeating myself, a metric is a measurement, and any measurement contains BOTH a start point AND a finish point. Therefore, begin your flow data journey by defining the start and end points in your process. Then consider updating those definitions as you collect data and as your understanding of your context evolves. Anything else is just theatre.


  •, "Be Smart", Season 10, Episode 9, 08/10/2022

  • The European Space Agency,


About Daniel Vacanti, Guest Writer

Daniel Vacanti is the author of the highly-praised books "When will it be done?" and "Actionable Agile Metrics for Predictability" and the original mind behind the ActionableAgile™️ Analytics Tool. Recently, he co-founded, an inclusive community where everyone can learn about Professional Kanban, and he co-authored their Kanban Guide.

When he is not playing tennis in the Florida sunshine or whisky tasting in Scotland, Daniel can be found speaking on the international conference circuit, teaching classes, and creating amazing content for people like us.

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