Is the Earth round? Avoiding The Absolute Truth to Find the Practical Truth: the Devil is in the Level of Detail

Most people hold a “binary” notion of the truth. For them things can either be true or false, because that which is false cannot be true, and that which is true cannot be false. We will call this notion the “absolute truth”. I want to argue that this absolute truth notion is unsatisfactory and impractical at addressing the worthiness of scientific theories. For this purpose I will use an example.
 
Consider the idea that the Earth is flat. For people in antiquity living in a flat place like the plains or a desert it probably made sense to think this, but eventually the ancients figured out that the Earth was not flat. The Earth is round and we know that for a fact nowadays.
 
So, the Earth is flat: false, the Earth is round: true; right?
 
Actually, the Earth is not round!  As Isaac Newton proposed and was later found to be correct, the Earth, due to its rotation, is an “oblate spheroid”, which means it is flater at the poles and bulging at the equator (the distance from the Earth’s center to sea level is 13 miles longer at the equator).
 
OK, so, the Earth is round: false, the Earth is an oblate spheroid: true, right?
 
Well, not quite. The Earth is an oblate spheroid, but the southern hemisphere is wider than the northern hemisphere giving the Earth a bit of a pear shape.
 
Fine, so the Earth is an oblate spheroid: false, the Earth is a pear-shaped, oblate spheroid: true, right?
 
Actually, even this is false! The Earth’s mass is not distributed evenly across the planet, and the greater the mass, the greater the gravitational force, which leads to the creations of bumps in the Earth’s crust. Additionally these bumps change overtime due to the movement of continental plates, the changing weight of the oceans, lakes, ice masses, and atmosphere, and the gravitational pull of the sun and the moon. All of these processes can deform the Earth’s crust by the order of millimeters to a few dozen centimeters daily and by much larger amounts over geologic times.
 
So the Earth is a bumpy, shapeshifting, pear-shaped, oblate spheroid?
 
Yes.
 
Wahoo, we did it! At last we have the absolute truth! The Earth is an pear-shaped, oblate spheroid: false, the Earth is a bumpy, shapeshifting, pear-shaped, oblate spheroid: true, right?
 
At this point you are probably thinking: seriously, are you kidding?
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This is the problem with the absolute truth notion: it ignores the level of detail that is required for adequately describing physical phenomena. The level of detail that is required from a description of the shape of the Earth will vary depending on what you are intending to use it for. For surveyors determining distances in small patches of the Earth’s surface, a flat Earth model is perfectly suitable, as the error in the measurements is negligible. For people dealing with time zones, the round Earth description is perfectly adequate. On the other hand, satellite orbits can be affected by small deviations of the Earth’s crust from a perfect sphere, so people following satellites must take into account the oblate spheroid and pear deformities of the Earth. Similarly, people running particle accelerators must understand that the Earth is constantly shifting its shape so they can keep track of very small deformities in the Earth’s crust that arise daily and may mess up their measurements.
 
The vast majority of people would accept that the claim that the Earth is flat is false (low level of detail). On the other hand, most people would consider further refinements to the round Earth claim such as the oblate spheroid; pear-shaped, oblate spheroid; or bumpy, shapeshifting, per-shaped, oblate spheroid to be a needless amount of precision (too high a level of detail), and rightly so. The type of deviations from a spherical shape that these highly detailed models of the Earth deal with is at most about a dozen miles. If you take into account that the Earth’s radius is 3,959 miles, we are talking about a difference of 0.3%. By this token the Earth’s crust, despite its mountains and sea trenches, is very smooth. So for the use that most of us make of the information regarding the shape of the Earth, a round Earth model is an acceptable level of detail.
 
Depending on what you are trying to explain or achieve, trying to find the absolute truth may be not only impossible or unnecessary, but also cumbersome. So we come to the paradoxical realization that seeking the absolute truth may actually hinder or prevent our discovery of the practical truth! When scientists seek the truth regarding physical phenomena, what they have in mind is the practical truth which is a truth defined at a sufficiently high level of detail to explain the phenomena they are studying and derive predictions and useful applications. Later on other scientists may seek to explain things at a higher level of detail to address more complex questions that a lower detailed truth can’t answer satisfactorily, and so on.
 
What the public has to understand is that a scientific theory does not have to explain everything to be considered “true”. It just has to explain the relevant phenomena at a sufficiently high level of detail to generate accurate predictions and useful applications. The debate should not be about whether a given theory is true or false, but rather about whether a theory has been formulated at a sufficiently high level of detail for society to benefit from it.
 
The image from NASA is in the public domain.

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