To make sure there is no dishonest misrepresentation of what the scientific method is, we should probably start with the question, and start formulating testable experiments that allow various topologies and geometries to be discounted. From here we can rapidly narrow down to one or two geometries, then can select the geometry that best fits the evidence and experiments.
So let’s start off with the basics. We’re talking about geometry, so we can determine the geometry of the earth we are standing on by attempting to determine a single property:
What is our orientation compared to all other observers.
If up is the same for all observers, the earth is flat. If there are six different “ups” that are all 90 degrees different from any other: the earth is a cube, if the change in orientation for any observer is directly linearly proportional to distance, the earth is a sphere.
So; a way to scientifically prove the geometry of the earth is by finding a test that allows us to determine the orientation of all observers.
The best way of confirming the orientation is to have each observer measure the position of an object multiple observers can see at the same time.
You can do this with the sun, the moon or stars.
Their observed location will be a product of where they actually are, combined with the observers orientation. The latter is what we are attempting to determine.
If you make a number of measurements; you will see something interesting:
No matter where you are, or what location you are, if two observers are 69 miles apart, in any direction, the sun, the moon, or the stars will be in exactly 1 degree different positions in the sky.
On a flat surface this isn’t possible. As the object and each observer should form a triangle. Tan(o/a) shows that has you get further away from the object on the earths surface, the amount the angle changes decreases: ie: if you move 70 miles, you will have a bigger change in perceived angle if you are closest to the object than if you are 5000 miles away.
While this effectively means that observers must be orientated 360 degrees in 3 dimensions. While this could be described by a football type geometry or a geodesic with many sides: as we’ve never seen any form of ridge these can all be discounted.
So geometrically; this proves the earth is a sphere, as these measurements are not consistent with the geometry of a flat surface.
So, now we can get into the realm of confirmations, this takes the form of measurements that are consistent with the earth being a sphere. We should see most observations being consistent with a the earth being a sphere, and a flat earth. Consistence here is based on geometry only without additional explanations or theories added.
So let’s go through them: (I’m assuming people know how to use google: every thing on the list below can be confirmed with a quick google search).
1.) all other planets appear to be spheres. If any of the other planets appeared flat, the idea that the earth were flat would be more plausible.
2.) the sun appears to set for all observers on the earth. The times and nature is consistent with a spherical earth, but not flat.
3.) There is a horizon for all observers, that objects appear to fall over, and tall buildings are obscured by. This is consistent with a spherical earth, and not with a flat earth.
4.) the sun moves at a constant rate through the sky. This is consistent with the earth being a rotating sphere, and inconsistent with the earth being flat, and the sun rotating overhead. This is the principle of how sundials work:
5.) the sunset is at locations inconsistent with a flat earth and consistent with a sphere: at the horizon on the equinox, the sun rises due east and sets due west. On a flat earth, as described by flat earthers, the sun would be north east and north west respectively.
6.) the regions of earth that have daylight are consistent with a spherical earth: with a straight edged terminator.when the map of the earth is flattened, the regions of daylight and nighttime make no sense when the earth is flat, as some night time areas would be closer to the Sun than areas of day time. In addition on a flat earth, even a close sun would be higher over the horizon at all times due to perspective, meaning all parts of the world would be within line of sight of the sun.
7.) lunar eclipses are always round: never a line, no matter when or where they occur. This is consistent with a spherical earth, and inconsistent with a flat earth.
8.) pictures of earth, as a sphere, from space have been provided by multiple space agencies and governments hostile to each other, and a number of private organizations.
9.) GPS satellite technology has been developed that is based off satellite signals being received in the sphere. Hundreds of disparate companies are involved with the development of the satellite, commercial GPS chips, test equipment for validating them, etc: and gps is confirmed to work in the ocean, in the desert and in the arctic. This is not consistent with a flat earth, and is consistent with a spherical earth.
10.) Gravity is measured to be stronger North/south by an amount consistent with gravity being cancelled out by the centripetal force at the equator more than at the poles.
11.) Gravity would prevent the earth being flat, and requires it to be a sphere. This is also provides consistent explanations for the formation of the earth, and why all other planets are spheres.
12.) the distance you can see and the objects you can observe are related to how high up you are, this is consistent with a spherical earth and not a flat earth where you would have consistent depth of view with objects in the way the only limiting factor other than this.
13.) when using a device (a pendulum or gyroscope) with sufficiently low friction, the change they exhibit appears consistent with a rotating earth.
14.) lunar eclipses can happen, which are inconsistent with a flat earth.
15.) multiple dozens of companies in multiple countries develop and use satellites, including television, communications, satellite phones and have done since the days of Telstar.
16.) we can observe satellites like the ISS, and others passing behind the shadow of the earth on a daily basis.
17.) the stars rotate in different directions in the north and south, and appear to be moving in a straight line at the equator. This is perfectly consistent with a spherical earth.
In addition it’s worth covering the observations that are not consistent with a curved earth.
1.) There is always a horizon, but objects that should be a little beyond the horizon are sometimes visible.
2.) lunar eclipses are sometimes visible when the moon and sun are both visible to an observer.
3.) at short distances the earth appears flat.
(1) and (2) are not evidence of a flat earth, as they could also explained by other geometries (such as parts of the earth being flatter than others, or the globe being larger than thought.
(3) is not inconsistent with a spherical earth that is large, as any curvature or racing away of the earth would be nearly inperceptible and difficult to measure accurately.
(1) is explained by measurable effects: the atmosphere can bend light as warm humid air and cold air have different refractive indexes, as this ends up curving light by small amounts. Measurements of air and snells law of refraction make this apparent. This is also a consistent explanation as these locations that are visible are only visible in specific conditions, and non predictable times; rather than all the time.
(2), as with 1; knowns properties of air, and known laws of physics allows us to determine that the position of the sun and moon would be raised due to refraction; happily explaining this geometry.
So, let’s compare the explanations side by side to which explanation best fits the facts.
Or (given what I understand listening to flat earthers)
It’s pretty clear here that the idea of that multiple coincidental process all “just so happen” to conspire to make the world look as if it’s spherical strains credulity.
Most importantly: as there are multiple unknowns that would have to be assumed to exist; as well as multiple coincidences that conspire, it’s clear that flat earth fails Occam’s razor by a massive gulf; and thus a spherical earth most clearly and self evidently matches all the observations concisely, and with the fewest assumptions.
So as a result; actually applying the scientific method; flat earth absolutely fails to meet even the most basic scientific standard.
Indeed, it is not clear how anyone can think it is a scientific position given the number of unknowns, coincidences and unexplainable happenstance is necessary for it to be true.