accelerandom said: Hi everyone, I work at a small high school that does one-on-one teaching with students who often have some kind of attention related learning difficulty or have trouble in a large classroom. The physics and chemistry courses I have been teaching have very inadequate lab sections and we have very few lab materials, resources or suitable rooms. I've successfully hugely upgraded the chemistry labs by adapting experiments for a chemistry set. I need to do something similar for the physics labs...



One of my current students is doing physical science (and is not very interested or engaged). He noticed a poster of the Earth's core and made an odd comment - he had heard that maybe the Earth isn't really round (!!!). I suggested that we could incorporate this into the course.



I would like to do some fun experiments that can disprove or at least demonstrate evidence against "flat earth theory" - whatever bizarre internet version is currently popular. I'm convinced most people who claim to believe it are joking, but I decided to take my student's value at face value because it might be fun to examine the claims and actually his interest.



Any suggestions? Even stuff that is only tangentially related to the consequences of the earth's shape could be good, if I can tie it to the course goals. We can go outside but are very limited in equipment, though I can probably get permission to purchase anything not too specialized or too expensive. The course is a basic physical science one (introductory physics and chemistry) using Holt's Physical Science textbook.

What you can do is not an "experiment", but rather apply the "If this is true, then...." concept, and then compare it to what the students already know.First of all, you need to establish a model for a "flat earth". This isn't as easy as it sounds because, just like creationism/intelligent design, it is difficult to nail down a consensus or unambiguous model. So you need to use the simplest model that you can find. We can easily start with the earth being a flat disk, just like this picture below:I am showing the sun out of scale. It should be very far away so that the light "rays" (yellow arrows) reaching the earth is practically parallel.Now, we also must establish that the earth is spinning along some axis (a Foucault pendulum can clearly establish this unless one is at or close to the equator). To start, let's assume that it is spinning along the z-axis as shown.The sun, based on our observation, not only goes across the sky, due to the spinning earth, but also has a different maximum inclination at different times of the year, due to the tilt of the axis of rotation. In this case, I'm showing it at some tilt in the sky in the drawing.Once you have establish this, then we can play the game "If this is true, then....".Ask your student that if this model is true, how does this compare to what we already know.For example, the earth having such a shape will have the same amount of sunlight throughout the ENTIRE surface at any given time. This means that everyone will either be having winter at the same time, or summer at the same time. This is because the amount of light reaching the surface per unit area will be the same everywhere (remember, the sun is very far away). So the heating of the surface of the earth will be the same everywhere on the surface of a disk.YET, we know that this is not true, that while some parts of the earth are in the depth of winter, other parts of the earth are in the peak of summer, while other regions of the earth barely experience any seasonal change in temperature at all throughout the year. So already there is a problem with this flat earth model.Next, if this flat earth model is true, then everyone will be seeing the sun at the same inclination above the horizon at the same time. After all, the light rays are impinging on the surface at the same angle everywhere.Yet, we know that this is not true because we have time zones, and various parts of the world are at night while we are in daylight.Etc.....Now, one may also change the axis of rotation to be along "r" instead. If one does this, then maybe a flat-earther will argue that people on the "underside" of the disk will have opposite time period, i.e. the side facing the sun is having daylight, the other side will be having night. But is this valid?It isn't, because again, one side of the disk will ALL see sunrise, 12:00 noon, or sunset at the same instant. Yet, I know for a fact that the sun sets at different times in Chicago than in Fargo, ND.And so on....In other words, get your student to imagine the situation that the earth is flat, and then figure out the consequences. The compare those consequences to what they already know and take for granted. You'll see that they do not match.The most direct way to determine that the earth is a sphere is to actually look at the precession of the Foucault pendulum at different latitudes over a period of 24 hrs. The precession angle goes from 360 degrees at the North Pole, to zero at the equator, to NEGATIVE 360 degrees at the South Pole, i.e. it precesses in the opposite direction as the North Pole. So if you or your students can find friends at various latitudes all over the earth, they can collect the data for you and you can compile this.An indirect way to infer that the earth is not flat like a pancake is to simply look at the heavens above. Grab a very good telescope, and one can look at the planets all around us. They all look spherical, even though we are very far (i.e. I'm acknowledging the "spherical cow"). Very good telescope will show you Saturn, Jupiter, Mars, etc. looking very "sphericallish". It would be extremely ODD that the earth is FLAT when every celestial body we see around us are not.So without actually doing an experiment, you can already get your students to think and apply what they already know to come up with a rational argument on why the earth isn't flat.Zz.