Fun experiments to disprove Flat Earth

[JohnNemo]

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.

You could link up with a few other schools at varying distances to the south of you. They don't have to be due south - south west or south east, or a combination, is absolutely fine, so you could choose Florida, then southern Mexico (or Barbados if you want an Anglophone country) etc.

Get students at each school to measure the angle of the North Star. You don't need exact measurements. You could, for example, have one student raise their arm pointing to the North Star and have another student photograph the first student's raised arm so you can see the approximate angle.

The further south you are, the lower in the sky the North Star will be, then when you are south of the equator the North Star will not be visible but the Southern Cross will be, getting higher in the sky the further south you go.

 

[accelerandom]

Ah, now I remember reading about the Bedford experiment and atmospheric refraction a few years ago... annoying that that probably makes the Bremerton ferry watching unfeasible. I will work with my student to plan some kind of project that will probably involve Skyping or otherwise communicating people in different latitudes and longitudes and noting the stellar and solar differences between here and there. Thanks again everyone for the suggestions and links.

They are not joking, they are as serious as the anti vaxers / evolution deniers, the have conferences...

Will you be updating the site with your results? His arguments?

Yes I will, though it may be some time before we have the opportunity to do any of this...

 

[Alan McIntire]

If you're on a coast, watch distant vessels, and note that the masts of the vessels don't disappear below the horizon until after the rest of the ship has gone below the horizon. If you DON'T live near a coast, wait until the sun is setting on the horizon, about one solar width above the horizon . Telephone someone you know on the west coast, or better yet, overseas in England, or the Philippines, or wherever, and ask them how high above the horizon the sun is. Some of them are sure to say that the sun is BELOW the horizon. On a flat earth, the angle of the sun above the horizon could differ from place to place, but if it's below the horizon on ONE part of a flat earth, it's got to be below the horizon EVERYWHERE!

 

[Keith Mackie]

While not a classroom experiment, a great fun way to tackle the issue - you could even get the English teacher to join in - is to get a copy of Joshua Slocum's book 'Sailing alone around the world'. Slocum was the first man to sail single handed around the world back in the late 19th century and the book is an account of the voyage. It is a great read particularly at school level. The topic is rooted in the 'round earth' concept, effectively a grand experiment but also a lesson in geography. When he gets to South Africa he takes the train from Durban to Pretoria where he visits the president, Paul Kruger and gets into discussion over the 'flat earth' issue. I suspect that his account of this conversation, of how he 'teased' Kruger, made a significant contribution to the whole 'flat earth' movement.

 

[dennis_n]

An easy way I think would be to do a google call with another school at a different part of the world, then calculate the angle of the sun in the sky at the same time for both places. Obviously after doing some basic trigonometry, the results would only fit the round Earth model.

 

[DrClaude]

You could link up with a few other schools at varying distances to the south of you.

Or North! (Canada, Alaska)

 

[Tom.G]

The further south you are, the lower in the sky the North Star will be, then when you are south of the equator the North Star will not be visible but the Southern Cross will be, getting higher in the sky the further south you go.

(And others)

Counter argument: It is close by and you are seeing parallax.

I guess for a flat Earth when it is night, it means every where on Earth is at night. We can proof the Earth is round by calling somebody that their time is opposite time to caller. Modern day verification.

(And others)

Counter argument: They are on the other surface of the disc.

 

[Vanadium 50]

Here is a way to do this via surveying. Sort of. I don't really like it.

One can look at airline timetables to get distances between airports. Let A = IAD, B = ORD, C = SFO and D = IAH. AB = 589 (all distances in nautical miles), AC = 2419 , AD = 1190, BC = 1846, BD = 925 and CD = 1636. Angles are a = 49.662, b = 164.641, c= 30.044 and d = 116.856, all in degrees. This sums to 361.203 degrees, not 360. Therefore the four airports do not lie in a plane.

Why don't I like this?

1. It relies on other people's measurements
2. It requires some non-trivial facility with trig (in some cases, this might be a good thing)
   
3. If you tried to draw this with rulers and compasses, it will almost work out.
4. Not all airlines agree on these distances: United believes it's 4342 miles from FRA to ORD, but Lufthansa thinks it's 4344.

 

[OCR]

This sums to 361.203 degrees, not 360.Therefore...

Well, yes, there's that... . . However... ?

...the four airports do not lie in a plane.

I don't think that even an An-225 could handle that kind of load... .
.

 

[Vanadium 50]

I thought about it, and one can avoid trig. One can get the area of the quadrilateral formed by the four airports by using Heron's formula on the east and west triangles or the north and south triangles. They differ by a percent.

My other objections remain.

 

[JohnNemo]

Counter argument: It is close by and you are seeing parallax.

But if it is close by and you are seeing parallax from a flat Earth, the North Star would not disappear below the horizon as you go over the equator.

 

[zul8tr]

Ask your students to point to places on a flat map where there have been reports of people and/or animals falling off. Then suggest maybe in the future they go there and observe the edge? Reminds me of the movie "The Gods must be Crazy" where the coke bottle dropped from the sky was a desired thing for all in the clan to own. It eventually was considered to be evil and the main native character was tasked to take the bottle to the end of the Earth and throw it off.

It took over 2000 years to finally nail down (for most) that the sun is the center of our solar system and there are probably some that still do not believe that.
Go figure?

 

[Skeptic Tom]

Take your students to the seaside with a pair of binoculars and ask them to look at land/island about 10 to 12 kilometres away. No matter how hard they try they will not be able to see the shore where the sea meets the land because the curvature of the Earth blocks their view

 

[sysprog]

My calculations tell me that the Seattle to Bremerton ferry will sink about 40 feet by the time it makes it's right turn. Of course, you would have to be watching from water level. Seems like that should be visible with binoculars, or better yet, a camera with a healthy zoom.

View attachment 221746

Someone at stackexchange described the experiment. It's the first response to someone's question; "How high up do you have to go before you can sense the curve of the earth?"

I'll have to remember to try and recreate the experiment this summer.

Ah, now I remember reading about the Bedford experiment and atmospheric refraction a few years ago... annoying that that probably makes the Bremerton ferry watching unfeasible. I will work with my student to plan some kind of project that will probably involve Skyping or otherwise communicating people in different latitudes and longitudes and noting the stellar and solar differences between here and there. Thanks again everyone for the suggestions and links.Yes I will, though it may be some time before we have the opportunity to do any of this...

A field trip to the Space Needle would allow comparing visibility distances at ground level and from the observation deck. That would easily confirm that from up top, the boats that from the ground appear to have disappeared into the water can be seen all the way across Puget Sound, and that landmarks completely invisible from the ground come prominently into view as you take the upward Otis ride, and fall back out of view during descent. Perhaps you could add additional learning objectives in re history, architecture, engineering, etc. to help justify the associated effort and expense.

 

[zul8tr]

Ask your students to point to places on a flat map where there have been reports of people and/or animals falling off. Then suggest maybe in the future they go there and observe the edge? Reminds me of the movie "The Gods must be Crazy" where the coke bottle dropped from the sky was a desired thing for all in the clan to own. It eventually was considered to be evil and the main native character was tasked to take the bottle to the end of the Earth and throw it off.

It took over 2000 years to finally nail down (for most) that the sun is the center of our solar system and there are probably some that still do not believe that.
Go figure?

I was keeping it in the classroom, that's what was asked.

 

[stickman76]

I would suggest doing the test of Eratostenes. In the classroom, you could use a globe, a light and some matchsticks. Duplicate the experiment and use a ruler to measure the shadows and come up with approximate measurements. Not perfect but it will certainly show that Earth is a sphere, not flat. As an aside, I find it shocking that we are having to debunk 1st century science in 2018. :-)

 

[OmCheeto]

I would suggest doing the test of Eratostenes. In the classroom, you could use a globe, a light and some matchsticks. Duplicate the experiment and use a ruler to measure the shadows and come up with approximate measurements. Not perfect but it will certainly show that Earth is a sphere, not flat. As an aside, I find it shocking that we are having to debunk 1st century science in 2018. :-)

I don't know that any of us are trying to debunk the myth. I'm pretty sure the forum would have locked this thread on day 1 if that were the case.
I think it's a fun science project.
3 high school students from France dropped by last November and asked for help with the Eratosthenes experiment. I was surprised how difficult it was.

This experiment is making me want to cry.
Yesterday I measured the shadow being 2.10 meters long, by a new method. I think the error was much less than before.

Today I used a different method, and the shadow measured 2.04 meters long.
At this time of year, the shadows should be getting longer.

hmmmm...
I wonder how many times Eratosthenes did this experiment, before he figured out that science is kind of hard.

 

[stickman76]

"I don't know that any of us are trying to debunk the myth. I'm pretty sure the forum would have locked this thread on day 1 if that were the case."

Yes I 100% agree on that- it wasn't what I was suggesting, just that it's frustrating that wackadoodles on YouTube have kids believing that the Earth might not be round. Having not tried the experiment myself, I don't know how hard it is. I am however, very thankful for forums such as this where science and facts rule.

 

[rootone]

wackadoodles on YouTube

Best to react with non-wacky videos on Youtube, and there is quite a lot.

 

[Stephenk53]

Here is some of Cody's lab videos that may help
Measuring the curvature with a telescope

reply to flat earther

 

[Stephenk53]

And here is hopefully my last post on this matter (I can't think of the word right now but negatively excited)
Here is 10 ways
https://www.popsci.com/10-ways-you-can-prove-earth-is-round#page-12

 

[Guest812]

How to measure the Earth's radius using a watch, tape measure, and trigonometry:

It is possible to easily see the effects of the Earth's curvature by simply observing the Sun set while you lie on the ground, and afterwards see the sun set again approximately 10 seconds later if you stand up.

In fact, while watching the "double" sunset, anyone can measure the Earth's size with a Meter Stick and a Watch within a matter of a few seconds. For example: suppose while lying on a beach watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears. You then stand, elevating your eyes by a height H=1.70 m, and stop the watch when the top of the Sun again disappears. If the elapsed time is t=11.1 s, what is the radius r of Earth?

Knowing nothing more than the height of the eye while lying and standing, and their corresponding "double sunset" elapsed time measurement, knowing the Earth rotates a complete 360 degrees in 24 hours, the Pythagorus right triangle equation, and basic trigonometry, it is possible to fairly accurately calculate the Earth's radius.

If a person wants, a solution to this problem can be found in a book called Fundamentals of Physics by Halliday, Resnick, Walker on page 7 which can be viewed at Amazon's website: http://www.amazon.com/Fundamentals-Physics-Chapters-David-Halliday/dp/0471332356/ref=sr_1_23? s=books&ie=UTF8&qid=1361960056&sr=1-23&keywords=halliday+physics

NOTE: to view page 7 of the book on Amazon's website, I had to first log in, click on the book's "Look Inside" icon, then do a search for the terms "Sun set", and click on the first two search results.

NOTE: I don’t live next to a wide level body of water (i.e. wide level surface), and therefore haven’t taken the above measurements, nor given it much more thought; however I suspect the time difference measurements between Sun sets observed at different heights may vary depending where on Earth, and what time of year the measurements were taken.

 

[Guest812]

About 1,000 years ago, a more accurate calculation of the Earth's radius was made by Al-biruni using a protractor, tape measure, and trigonometry as shown in the below video:

 

[nuuskur]

A thought experiment. If you take off in, say, London and keep flying east. If the Earth was flat, how is it you will get back to London (assuming you keep flying east all the time)?

Any sub-variant will suffice. We know New York lies west from London (general direction). If we fly east, though, at some point we will have passed New York?!

 

[Dr. Courtney]

Wait, it's not flat?

 

[rootone]

Wait, it's not flat?

Yeah, I heard some clever guys discussing that it might be curved in some way, like a donut.

 

[Dr. Courtney]

Yeah, I heard some clever guys discussing that it might be curved in some way, like a donut.

The topological issues are much deeper.

 

[OmCheeto]

Collected some data yesterday, and today I did the maths.

Visually, even at 5 miles, it's obvious.

Guessing that my maths is a bit off (distance of 2.5 miles ≠ 3.8 miles) because of resolution problems.

Regarding the equation in the image:

d = atan((√(z^2+2rz))/r)r
d = how far you have to walk to see something of height z disappear over the horizon.
r = radius of Earth​

Camera was positioned ≈ 0.8 meter above the water line.

 

[ZapperZ]

That's a neat and fun set of observation, @OmCheeto . I've always wanted to do that, but never had the chance.

Now, if only those Flat Earthers actually understand what this all mean.

Zz.

 

[nuuskur]

That's a neat and fun set of observation, @OmCheeto . I've always wanted to do that, but never had the chance.

Now, if only those Flat Earthers actually understand what this all mean.

Zz.

I recall reading or watching a video or something of the sort about a Flat Earther who "debunked" OmCheeto's argument by...climbing higher with the binoculars Then he claimed, he could still see the entire ship even if it's 10 or so miles into the sea (which apparently contradicts this so called math).
I was like "..you don't say" while reading (watching).