Discourse over the shape of the earth[^1] has likely been among the most consistent pastimes for academics throughout recorded history, and the modern era is no different in that regard. Expecting one of the longest-running debates in academia to be settled by yet more academic literature is a questionable stance when centuries of existing literature have failed to settle it. This kind of situation is an excellent opportunity to review the foundational principles of science and the philosophy of knowledge: epistemology. This article will be a skeptic's journey through the contemporary meaning of science, its roots in the question of what can be known, the pitfalls of modern science, and a careful analysis of geodesy, astronomy, and navigation to draw a conclusion based on direct experience.
[^1]: My writing follows the Chicago Manual of Style's convention for the capitalization of this word.
The industrialization of scientific thought
Epistemology
I'm going to start by quickly reviewing epistemology since it's conceptually important to the rest of the article. Epistemology is a broad branch of philosophy which deals with the question of what knowledge is, and how people can truly know things. A common thought experiment is to consider the possibility that you're actually a brain in a vat in some lab and your nerve endings and fiber bundles are being stimulated by an evil scientist to make you believe that you're a person living somewhere in the world doing whatever you happen to believe you're doing right now. If you accept that to be conceptually possible, then you accept that you really don't "know" much of anything that you thought you did. The real world could be completely alien to what you believed it to be. In a situation like this, what can you truly know? Descartes' answer to this question is simple: "I think, therefore I am"[^2]. That is to say, since you're self-aware and thinking, it means that you individually can conclude that something must exist that is doing the thinking. This doesn't extend to other people since they may be part of the simulation and it doesn't necessarily mean that you exist in a manner that would be recognizable to you.
If you take this skeptical standpoint seriously, then very little can be established with absolute certainty about the external world. This is somewhat at odds with the whole idea of science, which seeks to expand our knowledge through observation. The reliability of our observations is itself an epistemological assumption rather than something that can be established through observation alone, but it is a necessary starting point for science to move forward. The more detached science becomes from observations that an individual can independently examine, the more it relies on trust in the people and institutions providing those observations.
Revisiting the school experience
If you went through a typical elementary and high school curriculum, you’ve likely been presented at some point with the oft-cited steps of the Scientific Method:
- Ask a question
- Do background research
- Construct a hypothesis
- Test your hypothesis by forming an experiment
- Analyze your data and draw a conclusion
- Communicate your results
You were probably asked at some point to execute these steps in order to demonstrate your understanding of the scientific method. If your background in the philosophy of science was limited at the time, as is typical for young children, then you probably found some of these steps difficult. Not difficult in the sense that you were academically challenged by the project, but in the sense that you did not understand the value in the exercise. For example, it’s challenging for a young child to come up with a question that would not fall into one of three categories:
- Is easily answered by background research (e.g. does plastic float?)
- Is so obscure that an informed hypothesis is impossible to generate (e.g. does my cat like carrots?)
- Is so abstract that it cannot be effectively tested by an experiment devised by a child (e.g. are unicorns real?)
Encouraging young children to explore the scientific method in this way is frequently going to become an exercise in undermining the philosophy of science by, investigating questions they likely already know the answer to, sabotaging their background research to avoid trivializing their experiment, and/or making unfounded conclusions from the outcome of their experiment. Appreciation for the nuances and benefits of the scientific method isn’t necessarily gained from rote execution of the “steps” without an understanding of the underlying philosophy.
Outlining the “steps” of the scientific method in the way that school curriculums often do deepens the issue for several reasons:
- The steps give no insight into the concept of a “theory”, which is quite central to scientific discourse.
- Beginning the steps with “Ask a question” circumvents the scientific foundation of forming broad self-consistent models and implies that any question should be answerable with a single experiment.
- The steps give no insight into what makes a hypothesis “good” by scientific standards.
- The steps give no insight into how to devise an effective experiment.
- The inclusion of a “data analysis” item independent of the performance of the experiment tends to imply that a good experiment should require extensive data analysis.
- The inclusion of a “communicate your results” item blurs the foundational philosophy of science with the industry of science.
That's not to say that I don't think the scientific method should be practiced in schools, or that school teachers should be burdened with reviewing the epistemological foundation of science with young children. It's easy to see the logic that the simple practice of the modern formulation of science is a good experience for a child to determine if it's something they want to pursue further. What I am saying is that the result is that it should not come as a surprise that young scientists entering higher education may already be comfortable practicing science without having had much opportunity to study the epistemological questions underlying those practices.
Perhaps this is one of those topics that higher education should be expected to course-correct with an early focus on philosophy in the science curriculum, but unfortunately that doesn't appear to be common.
[^2]: He originally coined this in Latin. Contemporary philosophers still don't understand why he felt the need to be so extra.
Industrial academia
I titled this section "The industrialization of scientific thought" without any exposition of what "industrialization" meant. When I say "industrialization", I don't mean the common sense of the word, i.e. in reference to the industrial revolution; I mean the conceptualization of scientific thought by scientific industry. Academic institutions such as universities, journals, and research firms have all more or less agreed upon a process that they refer to as "science": the typical modern research process of academic publication, grant proposals, and peer review. This process is imperfect in many ways,[^3] but the primary shortcoming I'd like to discuss here is specific: the industrialized scientific process places no more value on the foundational philosophy underlying science than the elementary school curriculum.
Similar to the scholastic experience discussed earlier, the higher-level academic experience also does not rigidly define what counts as a "theory", reconceptualizes a "hypothesis" as a probability topic rather than an aspect of the scientific method, and often trivializes the step of drawing conclusions.
[^3]: mostly relating to the fact that academic journals act as gatekeepers for what research gets proliferated to the broad scientific community despite their primary incentive being profit rather than the refinement of scientific discourse
The problem
The institutional procedures by which modern science is practiced do not, by themselves, teach or guarantee the epistemological principles on which scientific reasoning rests.
The strained connection between the modern execution of science and the foundational philosophy of science is a pervasive pattern that occurs at all levels of academia. It incessantly causes broad confusion about what counts as science, whether a given scientific standing is valid, and where modern or archaic scientific models come from.
It should come as no surprise that unregulated discourse on science exposes the state of discord that's been introduced by this departure of science from its epistemological roots, and at no point in history has unregulated discourse been as visible as it is in the modern internet age. The modern iteration of the earth shape debate is emblematic of this on both sides. The question underlying this debate sits largely outside the philosophical background most people receive in their scientific education: "when you remove institutional trust from the practice of science, what's left?"
None of this is to say that scientists or science educators are ignorant of philosophy. Philosophy of science is a specialized discipline and a person can become highly proficient at practicing science without receiving extensive formal exposure to it. My concern is what happens when the philosophical questions underlying scientific practice become so implicit that they disappear from the way science is ordinarily taught and discussed.
The philosophy of science
At this point I've mentioned "the philosophy of science" a few times without much explanation, and to be honest it's a little bit of a loaded term. There is a discipline called "the philosophy of science", which deals primarily in questions such as:
- What counts as science?
- What is the purpose of science?
- What are the limitations of science?
I consider this discipline to be a sort of meta-analysis of science: an analysis of science itself from a philosophical perspective rather than the scientific process of meta-analysis. It developed after science as a discipline of reflection on the already-existing practice; that is to say it's not what I'm talking about when I reference "the foundational philosophy of science". It's important to the topic of this article,[^4] but I'd like to discuss something else first: the fact that science itself originated as a branch of philosophy called "natural philosophy". If you had asked early scientists such as Isaac Newton or Galileo Galilei what they studied, they would have answered "natural philosophy" rather than "science". If you've studied mathematics you may recognize Isaac Newton's famous text "Principia" as one of the origins of modern calculus, but it's less known that the full name of his book is "Philosophiæ Naturalis Principia Mathematica" or "Mathematical Principles of Natural Science". Similarly, nearly two hundred years later Lord Kelvin (of temperature scale fame) published his book "Treatise on Natural Philosophy" which was foundational to modern physics.
At this point in history, natural philosophy was more or less the term used to describe the pursuit of understanding of the world rather than a specific method or discipline that should be used. It wasn't until the 19th century that the term "science" became commonly used in the modern sense, coinciding with the earliest iterations of what we know today as the scientific method.
All that is to say that:
- Many of the greatest revelations often credited to science were actually not the result of employing the scientific method.
- The scientific method and our modern understanding of "science" are relatively recent developments in the study of natural philosophy.
- To this day, the question of what actually counts as good science is the subject of debate.
Basically, we're still early in the "trial and error" phase of defining the discipline of science. The term "pseudoscience" itself remains poorly defined,[^5] and declaring something to be pseudoscience because it doesn't fit in with the contemporary zeitgeist of the scientific community is at best irrelevant to the debate and at worst unfounded. It's important to understand that science has a strong historical precedent of giving skeptics the tools to question institutional dogma. That is to say, perhaps the most foundational principle of science is that no institution can make an observation true by reporting it, or make an observation false by disputing it. Scientific knowledge ultimately has to be grounded in what can actually be observed in the world. Concepts like peer review, the scientific community, and scientific publications require trust that others are representing their experiences accurately and honestly. How that trust can be meshed with pure scientific thought is perhaps the most challenging problem in the philosophy of science.
Separating the epistemological foundations of scientific reasoning[^6] from the institutional mechanisms of scientific trust is critical to begin the process of using scientific reasoning to examine the institution of science itself. The distinction is what many traditional science backgrounds fail to provide insight on and is what I view as the reason that debates such as this one are so often reduced to the rehearsal of claims that simply do not touch the other party's belief system. Appeals to results provided by an institution are not effective if the opposing party does not respect the integrity of the institution itself.
That's not to say that you should value your limited set of experiences over the results of a much more rigorous experiment just because the experiment was reported by an institution. Of course, if you distrust the institution that's informing you of the experiment then you won't value its results. In this scenario, I would ask the reader to do some introspection as to why they're skeptical of the institution's honesty and consider whether they're preemptively treating any other institutions with less skepticism than is appropriate.
Excessive trust in institutionally reported results and excessive reliance on anecdotal observations are each their own form of epistemological dogma, and a scientist should be able to recognize them. If an individual has reason to distrust the institution of science then citing institutional results doesn't address their position. The epistemological grounding of science is what gives us the tools to test if an institution is being dishonest, even if that institution is the modern incarnation of the scientific community.
If you're debating with someone who often cites individual experience or research from organizations they've chosen to trust then you shouldn't assume they're not still engaging in scientific reasoning. The appropriate way to pursue the debate is by proposing and executing an experiment to test their assumptions which is independent of the conflicting institutions.
[^4]: More specifically it is the topic of this article
[^5]: There's literature on this; it's called the "demarcation problem" if you want to learn more
[^6]: A philosopher near you calls this "critical rationalism". I'm avoiding the term since throwing the word "rationalism" around in this debate could be escalatory.
How to do science
Definitions
I've gone on for a while now about how poorly some concepts in science are articulated by practitioners and educators, so I owe you some definitions. I'll note that different academic disciplines and levels define some of these terms differently, so you should take this as "how Shannon uses these terms" rather than absolute truth.
- An experiment is something that a scientist can do which will have a measurable outcome which is of interest to the scientist.
- A hypothesis is a prediction about the outcome of an experiment, derived from a theory or other set of assumptions.
- A theory is an explanatory framework that describes how a set of observations and phenomena are related, and from which predictions can be derived.
- A law is a concise description of a repeatable relationship or regularity observed in nature, often expressed mathematically.
Keep in mind that the words theory and law do not imply anything about the framework's status as "proven", "disproven", "accepted", or "likely".
How to learn about the world using science
Now that we know how I'm going to be using some important terms, let's quickly cover what it looks like to use the principles of science to broaden your understanding of something.
Let's presume that you already think you know how the world works because you've lived in it your whole life. You may be more sure about some things than others and you may have some rough ideas about topics you don't have a lot of experience with. I'm going to broadly refer to these beliefs as your personal theories of the world. They may be theories that are shared by the scientific community, like the theory of gravity, or they could be theories pertaining to your personal life, like whether your dog likes you.
If you're uncertain between two theories, you should test it. Quite intuitively, that involves some introspection or research to come up with something that you can do (an experiment) which will reveal evidence as to which theory is true. The experiment should be devised in such a way that the outcome will be different depending on which theory is correct. Each theory's predicted outcome is its hypothesis. You can then perform the test and observe the outcome. If it matches one of the hypotheses, then the experiment supports that theory. If it doesn't match a hypothesis, then something is wrong. Either the experiment was invalid for some reason you hadn't considered, or both theories are incorrect and you need to come up with something new that's consistent with your most recent experiment as well as your past observations.
This line of thinking is so intuitive that most people do it instinctively all the time. The conflicts often appear in the case of theories that cannot be tested by the individual due to lack of time, resources, or expertise. In these cases, one must often look to other people's recorded experiences, which involves deciding which of several institutions to trust on the matter. Whether that be members of the scientific community, a religious group, friends, news organizations, or influencers, the removal of science from its epistemological grounding is the same. It's true that the scientific community goes to great lengths to provide trustworthy information through peer review and independent replication and provides considerable overall value to society, but the scientific community has been wrong before, there have been messy paradigm shifts, and in some cases prolific researchers have been found to be faking their results.
This is often proclaimed as success by supporters of the scientific community, where ideas that were once believed are found to be wrong and the understanding grows, or the replication process has worked by identifying cases of fraud. In a way it is a success; the process is working as it's intended and our scientific knowledge is more complete than it ever has been. However, when it comes to an individual's decision to trust the scientific community's stance on a matter, frequent revision is a rational topic of concern.
It's not unscientific to distrust the scientific community, but it is unscientific to dogmatically trust another's observations without taking opportunities to experiment individually when you're able to. Especially if there's disagreement about the outcome of an experiment between communities.
With all of that out of the way, we can at last begin to consider the question of the shape of the earth.
Background research: The competing theories
Let's take some time to review the competing theories at play here so that we can devise an experiment to test them. Of course, there's the flat earth theory, but in my experience the competing theory is actually the combination of the law of universal gravitation and the round earth model. It seems like the most compelling aspect of the flat earth theory to some of the believers is that it does not require universal gravitation to be true. Universal gravitation has historically led to heated debate due to how unintuitive it is to accept in conjunction with most people's personal experience with gravity.
The flat earth theory
There are a few variants of the flat earth theory. For my investigation I'm leveraging the Flat Earth Society's wiki page. There are a couple of different geometries proposed here, but I'll be exploring the monopole variation since that appears to be the most ubiquitous and has the most supplemental material available. According to the theory, the earth is shaped like a large disk with the north pole located in the center and an ice wall around the circumference. The continents are distributed within the model such that their distance and angle from the north pole is consistent with our expectations from the common round-earth model (i.e. projected azimuthally about the north pole). The sun and moon are both suspended above the disk by some distance and revolve around the center with their path radii being half the radius of the disk.
The sun revolves around its path once per day, which is what causes day/night phenomenology since only the near half of the disk is illuminated by the sun, while the far half is in darkness. The sun's path radius changes from season to season, explaining the seasonal shifts in the sun's path through the sky. The altitude of the sun and moon above the earth disk also varies over time, explaining the phases of the moon.
The moon presumably revolves around its path about once per month, which explains its intermittent visibility in the sky.
The phenomenon of gravity is caused by a constant upward acceleration of the disk.[^7]
The disk is magnetized similarly to a ring magnet, with the north pole of the magnetic field being in the center of the disk and the south pole being on the circumference. This is why magnetic compasses point toward the north pole.
The other planets in our solar system are revolving around the sun as it transits its path along the equator. This explains the apparent motion of the planets in the sky in a manner typical to a geocentric model of the solar system.
[^7]: Somewhat strikingly similar to some principles of general relativity, but that's out of scope
The round earth model and the law of universal gravitation
This is taught in most school curriculums, but I'll cover it here for completeness. The round earth model proposes that the earth is essentially shaped like a sphere[^8] and is rotating upon its north/south axis at a rate of one rotation per day. The earth is also revolving around the sun at a rate of one revolution per year. The axis of rotation of the earth is tilted 23.4 degrees relative to the axis perpendicular to its orbital plane.
The earth's rotation with respect to the sun causes the day/night cycles and its slanted axis combined with its motion around the sun explains the seasonal shifts in the apparent path of the sun through the sky.
The moon is revolving around the earth at a rate of once per month and the planets in the solar system are revolving around the sun at their various rates. Note that the orbital planes are all closely but not exactly aligned. In particular, the moon's orbital plane about the earth is about 5 degrees offset from the earth's orbital plane about the sun.
The reason that all of these objects are revolving around each other is the same reason that things don't fall off the bottom of the earth: there's a gravitational force of attraction between all things that have mass, and large objects like planets or stars attract things like people, moons, and planets to them. The reason that the earth and whatever's on it doesn't careen into the sun is because its velocity is high enough that the gravitational pull of the sun continually bends its trajectory into an orbit. It's the same phenomenon that allows a motorcyclist to complete the "wall of death".
[^8]: Yes, it's an oblate spheroid. Thank you.
Simple observables
Now that we've reviewed the theories, let's take a look at some simple observations that might make someone inclined to believe one or the other. Keep in mind that both theories have explanations for all of these observations, but these are the points that are typically associated with the two viewpoints.
Observations that support the flat earth theory:
- The earth feels flat. The round earth model explains this with the massive scale of the planet, where its curvature through a normal observable distance is minuscule.
- The horizon looks flat when viewing the ocean. The round earth model explains this because the horizon is where your field of view meets the descending surface of the earth, which is roughly symmetrical at all sides.
Observations that support the round earth theory:
- When looking out over open ocean, you can see ships and landforms "sink" into the horizon as they get farther away. The flat earth model explains this as a phenomenon caused by the atmospheric refraction of light.
- Other planets that we can see in the night sky are spherical. The flat earth model explains this as the earth simply not being a planet like the ones we can see in the sky.
Celestial navigation
One of the focal points of any model of the earth and cosmos is celestial navigation. For thousands of years, navigators have been making careful measurements of celestial features like the stars and the sun to help determine their location in the open ocean. A common tool for this is the sextant, which is essentially an arrangement of mirrors that allows the user to precisely determine the angle between their line of sight to two objects. The North Star is a prime example; in both models it's located some distance away from the earth and approximately aligned with the northern axis of the earth. Using this information, navigators in the northern hemisphere can use a sextant to measure the angle of elevation of the North Star from the horizon to approximate their latitude.
With the advent of satellite navigation systems like GPS, celestial navigation is often thought of as archaic, but it's still quite commonly used. For instance, submarine-launched ICBMs have a requirement to be able to determine their position on Earth when they emerge from the water so they know what trajectory to take to hit their target. Since complex satellite systems like GPS may not be functioning late in a destructive war, the missiles need to use other means to determine their location. A popular method is to use an infrared camera to photograph the sky and analyze the stars (which are visible in the daylight in infrared) to calculate their location.
It's important that a model of the cosmos supports this practice, and both models do. In the flat earth model's case, you have to make some assumptions about atmospheric refraction to make the geometry work, but those assumptions more-or-less were already made in the explanation of the day-night cycle. Without refraction, the sun and moon should be visible to all observers at all times, but according to the flat earth model's claims atmospheric refraction prevents the low-angle line-of-sight that would be needed to observe the sun from the night side of the disk. A similar explanation could be used to justify some of the apparent conflicts here (i.e. if the North Star is suspended above the north pole, shouldn't it be visible from the southern hemisphere?).
Devise an experiment
As you read into these theories, you'll find that they each have some literature citing experiments that support them. A lot of these experiments follow the same essential setup of placing some target at a fixed height above the level of a body of water and trying to determine if the elevation angle of the line-of-sight to the target is as expected by one theory or another. These aren't really ideal experiments for a couple of reasons:
- They're difficult for an individual to perform.
- They have mixed results, and each community often cites the results that support their theory as valid while dismissing other results as invalid due to refraction of light in the atmosphere.
- Even if we assume that atmospheric refraction is negligible, the commonly accepted iteration of the round earth model actually proposes that the surface of a body of water does not follow the curvature of the earth and the direction of gravity is not necessarily straight down.[^9]
Due to all of these concerns, I would rather avoid an experiment that's dependent on precision measurements across long distances in favor of something that anyone can do and which can't be discredited as a refraction phenomenon.
Let's think about the phases of the moon for a moment. Both theories explain the changing phases of the moon as an effect of the moon being half lit by the sun from various angles as viewed from the earth throughout their orbital cycles. Thinking about the geometry, there's a clear conflict between these two models in the phases of the moon they predict in certain conditions.
The most trivial to consider is the case of a moon cycle that crosses the observer's longitude[^10] at exactly midnight.[^11]
[^9]: If you want some fun late night reading, the geoid and deflection of the vertical are prime candidates. I'll stop by to talk about tidal theory.
[^10]: The more contextually correct term here is actually "meridian" but I thought that would be confusing.
[^11]: Solar midnight. More on that later.
Form a hypothesis
In the flat earth model, this would imply the geometry of the sun being located directly across the north pole from the observer's location (midnight) and the moon being located at the observer's longitude on the observer's side of the earth, directly opposing the position of the sun. In this case, the moon would be lit by the sun from the observer's north. Depending on the observer's latitude and the altitudes of the sun and moon at the time, they may see a larger or smaller portion of the moon lit, but the lit portion would be the north side of the moon according to the observer's magnetic compass.
In the round earth model, the described scenario would result from the earth being located between the sun and moon, with the observer being on the moon side of the earth. Depending on where the 5-degree offset of the orbital planes lines up, the moon could be slightly to the north or slightly to the south of the sun-earth line. In those cases, the moon would appear essentially full because the observer would be looking at the moon from nearly the same angle as the sun's illumination. If the orbital planes happened to line up, then the earth would be directly between the sun and the moon and block the sun's illumination of the moon, resulting in a lunar eclipse.
So, the hypothesis derived from the flat earth model is that if you look at the moon on a night when it's directly north or south of the observer (i.e. crosses the observer's longitude) at midnight, then the moon will be partly lit from the north. The hypothesis derived from the round earth model is that either the moon will be full or there will be a lunar eclipse on that night.
I encourage you to take some time to think about the two models yourself and make sure you agree with my finding. I haven't included any diagrams of the geometry to enable you to derive your own hypothesis.
Keep in mind that when I say midnight here I mean solar midnight rather than exactly 12:00 AM in whatever civil timezone[^12] you happen to have aligned your clock to. You can look up your solar midnight online based on your longitude and the date, or record the time that the sun reaches its highest point during the day (solar noon) and add 12 hours.
At this point I'd like to clarify something I touched on earlier: the fact that science education often doesn't teach why the scientific method is structured the way it is. Probably the most crucially overlooked detail about the method is the true purpose of the hypothesis step. Some of the most subversive human reasoning biases have a tendency to manifest upon the revelation of a new piece of evidence which does not fit in with the observer's worldview. Often the human response is to minimally modify their worldview to accept the new observation (conservatism bias) or retroactively reframe the observation to distort it into their current worldview (assimilation bias). This kind of bias often leads to overly complex and imprecise worldviews, when often the best response is a systematic re-evaluation of your worldview to arrive at the simplest theory that explains everything you've seen. It's my personal belief that the most notable emergent goal of the scientific method is to inoculate a scientist's findings against those biases. This is where the hypothesis becomes critical.
Look at the hypotheses. Look at the distinctive wording: "If I perform the experiment, then the theory predicts that this will be the outcome of the experiment". That's not a guess, that's a conclusion which is predicated on the experiment you're about to perform. More potently, it's a promise you're making to yourself that you will not allow the outcome of the experiment to cause you to abandon the careful reasoning that led you to perform the experiment in the first place. I've given you the guidance needed so that you can rationalize to yourself that this experiment is effective. You should be thinking about where the experiment could go wrong right now, before you encounter the biases that will arrive in your mind along with the outcome of the experiment. What if the geometry doesn't line up exactly right? What if your estimation of solar midnight is a few minutes off? Will that kind of error make the experiment invalid, or is the geometry of the problem resilient to that kind of noise? What about atmospheric refraction? Is the outcome of the experiment sensitive to that? How much atmospheric refraction would it take to make the experiment inconclusive? Are you willing to accept that magnitude of atmospheric refraction into your model to justify an unexpected result? Does your model predict that atmospheric refraction is the same all the time? If not, does it make sense to perform the experiment several times?
These are questions you need to answer before performing the experiment, and if you find it to be necessary you can revise your hypothesis or come up with a new experiment that you think will be more effective based on your answers to the questions. Chances are you'll have several days between reading this article and your next opportunity to perform this experiment, so I encourage you to spend some of that time reflecting on these questions to be sure that when you finally perform the observation, you'll know what the rational conclusion is.
It's your responsibility as a skeptic to maintain the falsifiability of your theories and hypotheses, and this exercise is critical to distinguish your skepticism from dogma.
[^12]: Don't get me started
Perform the experiment
Now that we have our hypothesis, all that's left is to go outside on a night when the moon is directly north or south of your location at midnight, take a look at your magnetic compass, and record what you see. If you're a night owl, I encourage you to take a look at the compass angle of the moon at midnight each night and simply wait until the night when it's directly north or south of you and make your observation of its phase.
If you'd rather not do that, there are several websites that will tell you the next night that this will occur, although be warned that they'll often phrase it as "the next full moon". You'll have to independently verify that the alignment is correct (i.e. the moon is directly north or south of you at midnight that night) and make the observation of its phase.
Draw a conclusion
Once you've performed the experiment, you can use the results to assess the theories you were testing. If what you were expecting isn't what happened, then you'll need to revisit your assumptions to make sure that your theory of choice going forward can explain the observation. I'd implore you to consider this independently for some time before reaching out to others to help explain the result.
Kind regards,
Shannon
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