Demonstrating How Refraction Helps You See Over The Horizon

[Mick West]

Source: https://www.youtube.com/watch?v=KLufSkz-et0

If there were no atmosphere, and somehow the Earth still had oceans, then the curvature of those oceans would be readily apparent, with a pin-sharp horizon cutting off distant objects with mathematical precision. You'd be able to zoom in clearly on ships vanishing over the horizon, and calculate the radius of the earth with great precision.

But back in the real world, we have an atmosphere. That atmosphere is generally denser as it gets lower down, and this makes the light bend down a bit, which lets you see beyond the mathematically calculated horizon.

This is normally illustrated with a side view, with the camera on one side and the target object on the other, and a greatly exaggerated curve of the Earth, like this:

This is where the explanation starts to get lost on people. This abstract side view is something that often causes confusion.

So I'm seeing if I can get some kind of physical demonstration of what is going on. I've got a fishtank partly filled it with water, layered some sugar on the bottom so it would dissolve and create higher refractive index the lower down you went, and I've got a laser with a beam splitter:

The idea is that from the side it's like the diagram. There's rays of light, they curve slightly, and there's the slight curve of the earth:

The curve is slight, but there. More visible with some compression.

At the other end of the tank, I put a photo of Toronto, and flipped the laser to a single beam and put it behind it.

I then moved the camera up and down.

This compression of the scene near the horizon is very similar to that observed in the Jenna Fredo video (@jenna1789), discussed in this thread: https://www.metabunk.org/views-of-t...rt-niagara-illustrate-earths-curvature.t8149/
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And this setup can be duplicated in the refraction simulator, with a very cool lower layer, taking it from 80 feet to 1 foot above the water:
https://www.metabunk.org/refraction/?~(profile~(~12.41~0~13.084~6.017~17.352~32.883~17.315~15.205~16.48~287.6~16.52875552~262.976)~useRefraction~true~useStandard~false~useFlat~false~useNarrow~false~useNight~false~showSideView~true~showSideGradient~true~useDebug~false~showEyeLevel~false~vFOV~0.022689280275926284~tilt~0.0008726646259971648~showEveryLines~10~viewerHeight~1~viewerOffset~773~minX~12~maxX~18~minY~-10~maxY~300~RH~50~wavelength~550~computedParams~false~name~'Toronto*20From*20Hamilton*20Beach~src~'Toronto*20From*20Hamilton*20Beach*2032*20miles.png~sourceURL~'https*3a*2f*2fwww.youtube.com*2fwatch*3fv*3dAFJnrMZT7KA~targets~(~(distance~168960~height~1815~name~'Toronto~multiple~0~gap~0)))_
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So, a good practical results. But I wonder how best to communicate it to people. I think the key concept is how the laser line is the same as a line of sight. If you shine a laser in a particular direction it will hit a spot. If you look in exactly the same direction your were shining the laser, and from the same position, then your line of sight will follow that same (possibly curved) line, and you will be looking directly at the spot.

 

[Mechanik]

Awesome experiment, @Mick. Beautiful and easily understood analog that can be replicated by anyone with minimal equipment.

The communication part is going to be tricky. Putting on my tinfoil hat, my first response is "What does sugar water have to do with atmospheric refraction?" Is there some (indisputable) math that can equate atmospheric density to liquid density over distance? Perhaps some added math to your refraction calculator that lets you swap air for water? I'm sure the math exists, but this is well beyond my expertise.

Just trying to red-blue team the argument. As a recreational sailor who has navigated beyond the horizon using nothing but a compass and a map, I'm baffled that there is a flat earth controversy. If any of these flat earth folks had tried to sail to an island that was not visible from shore, I'm sure many of them would be converted. None of them can imagine the relief one feels when the expected peak first shows over the horizon.

 

[deirdre]

if you used some little aquarium heaters and had the tank more full of cold water to start, and filmed how the refraction changed over time as the heaters heated up? would that work? if the heaters were small enough (or could be lowered in temp enough) and placed on the two ends it might sort of demonstrate how the sea is colder in the middle than at the shore. ?? might need a bigger tank though.

 

[Mick West]

I made a video explaining how I set up the experiment. I figure I'll make a few more videos dealing with misunderstandings and Flat Earth objections.

Source: https://www.youtube.com/watch?v=KLufSkz-et0

 

[Mendel]

Dang Jos has made experiments with butane and liquid nitrogen that show this by using gas to cause refraction. The first two use butane, the third uses liquid nitrogen, and there are more on his youtube channel. He is open to suggestions.


Source: https://youtu.be/5lmmzvzz_Xs


Source: https://youtu.be/yFQDtzu-47s


Source: https://youtu.be/o0fnsGDP1pU

 

[Mick West]

I took these seven 2" screws and put them in the tank along one side.

View from the front of the tank, minimal refraction.

View from the end, with progressively more refraction the deeper you go.

The shrinking you see is mostly not from perspective. It's mostly vertical compression (notice how the far screws look much fatter).

See the compression is much more pronounced lower down. There are equally spaced black bands on the lower parts. You can also see the thread spacing change.

 

[Mick West]

Repeating it with visible light, to show it bends just like the laser.

The light comes in angled slightly upwards, and hits the ground at screw #3

 

[Astro]

Repeating it with visible light, to show it bends just like the laser.

Brilliant, is that sunlight you're letting in there through that slit? I assume this is to put to bed Mr. Riley's excuse that the laser reacts differently than sunlight would.

 

[Mick West]

Brilliant, is that sunlight you're letting in there through that slit? I assume this is to put to bed Mr. Riley's excuse that the laser reacts differently than sunlight would.

It's a powerful flashlight through a slit. No sun today

 

[Mendel]

Suggestion: you could draw equidistant parallel lines on the outside of the tank, see how they look from inside

 

[Mick West]

Suggestion: you could draw equidistant parallel lines on the outside of the tank, see how they look from inside

You can't see out of the side of the tank from the end, because of total internal reflection

 

[Leifer]

Along with a version of this and many other "home experiments" prevoiusly described....might I suggest that you post or create a separate area for DIY (do it yourself) home experiments and tests ?
Maybe a place for interested people to either replicate, prove / disprove, or expand on the ideas ?

My thrust about this, is to entice people to experiment for themselves, in an effort to "learn from doing".....instead of simply " learn from reading".
.

 

[JFDee]

There is a video response from "Dr John D.". As I understand, his critique mainly revolves around the claim that air above the sea is normally less dense so that the density gradient is reversed.

Comments are disabled for the video.

 

[Rory]

Looking through, his main objections seem to be that sugar in a fish tank can't represent the actual atmosphere we live in, and his idea that the air 0-1km above the sea is less dense than the air above it, therefore refraction actually bends light up (he also shows pictures of lasers bending up, and claims to be unable to find any of lasers or lights bending down).

Here are some of the most pertinent slides:

 

[Mick West]

(he also shows pictures of lasers bending up, and claims to be unable to find any of lasers of lights bending down).

There's a good reason for that. I'm adding lasers to the refraction simulator to explain. Still a work in progress, but here's the basic illustration of what is happening.

Laser over warm water:

Laser over cold water

 

[JFDee]

his idea that the air 0-1km above the sea is less dense than the air above it

He obviously thinks that the standard atmosphere applies always and everywhere which is of course not true. There are local deviations all the time, like with inversions where the gradient actually reverses direction (warm air above cold air).

Also, the decreasing temperature with altitude in the standard atmosphere is a consequence of the decreasing density, so it's a misunderstanding to assume that density normally increases with altitude.

Cold air is necessarily denser than warm air only when at the same altitude.

 

[Mendel]

https://en.m.wikipedia.org/wiki/Density_of_air#Variation_with_altitude , public domain image by Beojan

Standard Atmosphere: p0 = 101.325 kPa, T0 = 288.15 K, ρ0 = 1.225 kg/m³

Search for air density height and you'll find more variations of this diagram.

 

[Mick West]

He obviously thinks that the standard atmosphere applies always and everywhere which is of course not true. There are local deviations all the time, like with inversions where the gradient actually reverses direction (warm air above cold air).

The standard atmosphere isn't just "it gets colder with altitude", it's getting colder at a specific linear rate (0.0065 °K/m) that results in a fairly linear refractive index gradient. He's discussed different conditions over water at night, where warm water creates a much steeper (and non-linear) gradient, resulting in inferior mirages.

He's got several mistakes there, but his basic point seems to be that the density gradient (density decreasing with altitude) isn't something we see in reality. Clearly, though it is, and it's easily observed in daylight.

The graph above though is for the standard atmosphere, it's also for a largely irrelevant range, up to 10km. We are really interested in the first 100m or even less. Over water, there can be a significant effect. Here's a simple rendering of the refractive index in white (representative of density) with temperature in red. The white line is like a zoom in on the lower left 15m of the graph above, so looks linear. Red is linear temperature.

If we then compare that to a typical inferior mirage situation where warm ground or water is heating the air directly above it, causing a more rapid decline in temperature (red), we see that the density DOES increase with altitude, but only while this steep temperature .gradient exists.

To make this consistent up to 1km would require a constant steep gradient up to 1km, roughly around -3°C (or more) per 100m - something that obviously does not happen.

Getting back to the topic of the thread here though. It's "how refraction helps you see over the horizon" it is NOT "this fishtank of sugar water is exactly like the atmosphere". The idea here is to help people understand what is going on with the paths of light when they observe things looming over the horizon.

 

[Mick West]

There's a good reason for that. I'm adding lasers to the refraction simulator to explain.

And with the laser rendered.

Warmer lower:

Colder lower

The laser is level at five feet, the viewer is 2 feet above and 3 feet to the side. Even though the laser has more of a curve in the cold situation (where it bends around the curve) it's less apparent to the viewer.

 

[Mick West]

One last experiment with the tank — mixing it up to see the gradient and the refraction vanish.


Source: https://www.youtube.com/watch?v=oGMkIqAidK4

 

[Mechanik]

With regards to Dr John and his temperature gradient, I have to wonder whether he has ever heard of the Southern California "June Gloom" or a temperature inversion. June gloom refers to the fog that forms in summer due to the cold ocean air mixing with the hot air off the land. When that cold moist air comes inland in the evenings (as the deserts cool), it forms summer fog in the coastal basin (atmosphere cold at the bottom, then warm, then gradually cooling as you go up). The temperature inversions (remember the famous Los Angeles smog?) have a cap of colder air over the warmer ground air, trapping heat and pollution below (warm, cold, warm or cold and eventually cooling?).

I guess my point is that, in a geophysical sense, the air density decreases with altitude, but in the local sense i.e. the first 2,000 feet above the surface of the earth, relatively tiny pressure and temperature variations have a profound effect on air density and thus, refraction.

@Mick West, was just re-watching the original video and noticed that you misspoke at about 10:03. Missed it the first couple of times. Doesn't look like anyone jumped on this but you said "sea level" when it's obvious you meant water level as Toronto (not Chicago) is a couple hundred feet above sea level.

 

[DavidB66]

Not sure if this is the most relevant thread for this, but I wanted to draw attention to a new video by Al K, showing some more examples of extreme refraction effects, mainly from his own observations on the coast of Scotland:

Source: https://www.youtube.com/watch?v=fR3YctWFj00&t=27s

 

[scroydon]

Awesome experiment, @Mick. Beautiful and easily understood analog that can be replicated by anyone with minimal equipment.

The communication part is going to be tricky. Putting on my tinfoil hat, my first response is "What does sugar water have to do with atmospheric refraction?" Is there some (indisputable) math that can equate atmospheric density to liquid density over distance? Perhaps some added math to your refraction calculator that lets you swap air for water? I'm sure the math exists, but this is well beyond my expertise.

Just trying to red-blue team the argument. As a recreational sailor who has navigated beyond the horizon using nothing but a compass and a map, I'm baffled that there is a flat earth controversy. If any of these flat earth folks had tried to sail to an island that was not visible from shore, I'm sure many of them would be converted. None of them can imagine the relief one feels when the expected peak first shows over the horizon.

My first post and I thought I would comment, here. I'm a Boomer. My education is somewhat typical of others in my demographic, high school and post graduate University. I was brought up asking questions and looking for answers. Opinions are fine but consider the source and qualify those opinions. I grew up using the library to get answers. As a sojourner in many regards can you imagine the freedom to know anything without a trip to the local library?

Unfortunately, the freedom gain from Google has a troubling cost that has not affected those who ponder like myself. I ask questions but I don't fear the requirements to gain answers. And, that is the real challenge set before us. How do we affect those, our children and grandchildren who would ask the question but would rather seek anecdotal opinions from a friend or what not. They have neither the skills nor the desire to query Google nor do they have even the basic understanding of cause and effect. Sadly, it is their expectations that everything be hand to them on a platter that they care little to educate or challenge their mindset.

A friend reminds me frequently that today's "yutes" can not conjugate a verb. I ask my two grandsons whom I'm raising what is language arts and they can't give me an answer. This entire generation is so passive that their future will be bankrupt of most financial well being expecting to be entertained to never stretch their imaginations or their experiences. If it is not found on their smartphone or YouTube then it is neither valid nor worthwhile.

So, I am very grateful for stumbling across this website. I am certain those seeking knowledge will benefit from the content published here as much of the content is for those who are not Phd's. For this I am very grateful.

So, how will you reach young minds (or even old ones like mine?) Honestly, I don't know. I fear entire generations lost to ignorance and laziness. Finding ways to communicate scientific ideas to those heads filled with mush is only half the problem. Getting them to develop an inquisitive mind is the other half of the problem.

I know I'll be visiting more often and perhaps with your direction, I can challenged myself to delve into the question my grandson just asked concerning the validity of the flat-earth controversy. I have only started looking for simple ways to explain a global viewpoint and invalidate a flat-earth philosophy.

Thx

 

[scroydon]

Thanks for a great presentation on light bending, Mick.

I have spent a few days looking for simple ways to understand the Flat-earth viewpoint. My 14 year old grandson popped the question concerning how anyone could see Earth as a flat disc. I told him that this is a large can of worms. I said many flat-earth followers reason anecdotally, that there is a seriously bankrupt scientific understanding as many viewpoints are faulty. And I said the same criticism can be made by those supporting a global Earth. The unfortunate reality is that ignorance eclipses both camps. Here I speak of anecdotal talking points found in many discussions.

So, I shared with my grandson a study using laser light and a boat on a large lake. Sighting the beam on the boat the spotlight tracked upwards as the boat moved further away from the source of light. This suggested a curved body of water resulting in a boat lower in the horizon.

It is an interesting theory explaining cause and effect but I fear it is too simple an effect. I know a little about laser light being the victim of moisture and gases. In an earlier time I was a G.S. Field inspector for an engineering firm building sanitary sewer systems. I also cleaned my share of swimming pools and saw how water bent the skimmer pole.

So I am very grateful for your thorough explanation on how light can bend over water. My question concerns the laser/boat study. Does your experiment invalidate this study and it's conclusions given that water moisture on the lake surface would cause the laser to rise in relationship to a boat moving further away even if the lake we're actually flat as in a Flat-earth?

A side note. I have also started to ponder whether a navigational sextant could support a Flat-earth viewpoint? I think this is similar to trying to prove the antithesis or do I have that backwards? I have read an argument against the sextant since it and the navigational tables assume a round Earth and thus can not support a Flat-earth. I think this kind of argument is weak. Your thoughts?

One last thought. During the age of "tall ships" one would observe the tall mast long before the hull appeared upon the horizon. Can this invalidate a Flat-earth view?

Thx

 

[Mick West]

So I am very grateful for your thorough explanation on how light can bend over water. My question concerns the laser/boat study. Does your experiment invalidate this study and it's conclusions given that water moisture on the lake surface would cause the laser to rise in relationship to a boat moving further away even if the lake we're actually flat as in a Flat-earth?

It's not a very good experiment. Like all experiments close to the surface there are refraction problems. More to do with temperature than with humidity though.

I always advise people against such low-level experiments, and use things larger in scale, like mountains, or tall buildings.

A side note. I have also started to ponder whether a navigational sextant could support a Flat-earth viewpoint? I think this is similar to trying to prove the antithesis or do I have that backwards? I have read an argument against the sextant since it and the navigational tables assume a round Earth and thus can not support a Flat-earth. I think this kind of argument is weak. Your thoughts?

I'm not sure exactly what the argument is. Perhaps you could explain, and also explain why you think it is weak.

 

[Mick West]

One last thought. During the age of "tall ships" one would observe the tall mast long before the hull appeared upon the horizon. Can this invalidate a Flat-earth view?

Only if you agree with the science of optics.

 

[scroydon]

It's not a very good experiment. Like all experiments close to the surface there are refraction problems. More to do with temperature than with humidity though.

I always advise people against such low-level experiments, and use things larger in scale, like mountains, or tall buildings.



I'm not sure exactly what the argument is. Perhaps you could explain, and also explan why you think it is weak.

The claims is that a sextant can not be used to disprove a Flat-earth because the device and the math table assumes a global Earth. I believe the criticism is logically weak.

 

[Mick West]

The claims is that a sextant can not be used to disprove a Flat-earth because the device and the math table assumes a global Earth. I believe the criticism is logically weak.

You are going to need to be a bit more specific there.

 

[Tonymelenas]

Sorry for my English. I use google translation.
In Dang Jos's experiment, a mirror effect is produced.
If you look, the red part does not rise, it is reflected.
You can measure the gray part and you will see the difference. He recognizes it in his channel.
Regards.

 

[Hepper]

Just one more question concerning refraction of laser light:
West's demonstration of refraction of laser light in a fish tank with an artificially created density gradient has sparked substantial criticism from some flat earthers. For example, Sleeping Warrior uploaded a video in which he claimed the following:

If the earth is flat and light curves this way, it's going to give you the appearance of curvature [...]. (2:56)

See here:

Source: https://www.youtube.com/watch?v=Tde1_P7W4ys


He tried to prove this by the end of his video. I have two screenshots of his "experiment". Both of them quite clearly demonstrate that the bottom of the fish tank appears to be curved although it certainly isn't curved in reality. However, I do believe that the buildings in the background are compressed rather than obstructed by the supposed "horizon line".

(12:34)

(12:56)
Is this caused by refraction? Could refraction actually make a flat plane look curved?

 

[Mick West]

Is this caused by refraction? Could refraction actually make a flat plane look curved?

All visual distortion that we see in everyday life is caused by refraction or reflection. So the curve you see at the edges of the tank is caused by refraction.

 

[AmberRobot]

Why would a flat earther try to claim that refraction causes the appearance of curvature when they're constantly saying that curvature can't be seen??

There is never any cohesive logic to their claims and never any rigorous quantitative determination of the results of their claims.

 

[Jesse3959]

Here's just a simple diagram showing what heavy atmospheric refraction would look like on a globe -- allowing two oil platforms to be seen around the curve, and the horizon to be seen beyond them.

Many thanks to the original youtube author from whom I took the screenshot, Alejandro del Mazo Vivar!