You would be easily forgiven for answering “Mount Everest” to the title question. After all, that’s what most of us are taught in school (assuming we were awake during geography class). But if you have read any of my material over the years, you know that most of what we have been taught is misleading, if not downright wrong.
To determine the tallest one, we first have to measure all of the mountains on the planet. And it turns out that measuring the world’s mountains is much more complicated than you might think. In fact, over the years, there have been several contenders for the crown:
In 1792, Mount Chimborazo (Ecuador) was thought to be the tallest
Then, in 1808, it was Mount Dhaulagiri (Nepal)
Then, in 1847, it was Kangchenjunga (Nepal/India)
It wasn’t until 1852 that the peak we now know as Mount Everest was officially named the tallest mountain in the world.
Why did it take so long to name a winner? As you’ve probably guessed, changes in technology, measuring methodology, and even changes to the earth’s crust due to plate tectonics have all contributed to updated rankings over time (as an interesting side note, because of plate tectonics, Mount Nanga Parbat is currently growing faster than Everest and in 241,000 years will be the world’s tallest, ceteris paribus).
But in reality, the hardest thing about measuring a mountain is defining what it is. In other words, when we call something a mountain, we first need to decide where it " starts” and where it " finishes.”
To most of us, spotting where a mountain “peaks” is fairly obvious. Just look for the one above all of the other ones. But finding the top is only half of the equation. It’s deciding where a mountain starts, that is the tricky bit. For example, Mauna Kea is the highest point in Hawaii—that’s easy to see. However, more than half of Mauna Kea's mountain is submerged. Measuring Mauna Kea from its base (underwater) to its summit gives 10,211 meters—which is about 20% taller than Everest.
If we only consider mountains with a base on land, then Denali in Alaska is actually “taller” (with a base-to-summit measurement about 1,000 meters more than Everest).
So why have all of us been taught that Everest is the tallest? That’s because when measuring mountains, scientists generally use a “sea level” hack as the starting point for all their calculations. Why is the sea level a hack? As you may have guessed, the sea isn’t so level. The following graphic from the European Space Agency is a brilliant illustration of this point:
Due to factors like the earth’s rotation, tides, differences in the strength of gravity at different spots, etc., the sea actually has dramatically different levels around the globe. Scientists attempt to “smooth out” these differences by calculating an arithmetic mean to use as “sea level.” That’s right, they use an average. And as we all know, an average is (generally) a hack. Therefore, Everest gets its award due to an arbitrary starting point for a calculation that creates a baseline that doesn’t in any meaningful way exist anywhere on Earth.
I don’t know about you, but that doesn’t seem quite right to me. Why not pick a more objective starting point to measure from the center of the earth? If we do that, then our good friend Mount Chimborazo, whom we saw earlier, regains the crown (due to the fact that the planet bulges around the equator).
I’ll leave it up to you to decide what you think the tallest mountain is, but the point here is that all measurements require agreement on what started and finished mean. And you can get radically different answers depending on those agreed points.
Flow metrics, in particular, are not immune to this difficulty. When they think about predictability, most people think only about the ability to answer the question, “When will it be done?” But that question ignores half the problem. How long something will take depends BOTH on when something starts AS WELL AS when something finishes. Your process could be Everest, Mauna Kea, or Chimborazo, depending on how you look at it.
Therefore, take the time to carefully consider what “started” and “finished” mean in your context. Your customers—and your predictability—will thank you for it.
*This post was inspired by and based on the “Be Smart” video series on America’s Public Broadcasting Service (PBS). If you haven’t checked that series out, do so. Most videos are available on YouTube.
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