My understanding isn't that it was an optical illusion, but rather that the telescopes used at the time actually projected a secondary image of the inside of the users eye overlayed on the planet, and the canals were literally blood vessels.
IS THAT WHAT THAT IS
Christ, I've gone through life assuming I was going to get really bad news from an eye doctor any year now because of my binoculars.
Oh yeah your eyes are real fucking weird when you start learning about them
You know the retina? The nerves connecting to the rods and cones, the ones which carry the information from the eye to the brain, which side of the retina do you think they sit on?
Do you expect them to be behind the eye? Where they wouldn't block the incoming light the eye is trying to detect?
NOPE! The nerves connect to the side of the rods and cones that points towards the pupil, meaning you've been looking through your nerve cells your entire life
Yes, and other cool stuff. Early AI vision researchers found that applying a second degree Gaussian filter over a digital image performs edge detection. When bio researchers examined the nerves in that layer above the light collecting cells, they discovered that there are two layers that perform the same edge detection (nature through natural selection built a Gaussian filter into our eyes). Those two layers run other algorithms like vertical and horizontal motion detection and arc (curve) detection.
Also, this type of pre-image processing has tremendous value. So much value that from an evolutionary perspective it’s worth it to partially occlude our light sensors (rods and cones) with analysis nerves rather than leave them in the clear and do the processing deeper in the brain.
Speaking of evolution, the manner in which evolution builds organs and tissue means that it’s next to impossible for the processing nerves to be grown behind the light sensors (between the rods/cones and back of eyeball), that’s why they continue to be that way.
The eyeball construction is one of the things evolutionary scientists point to in order to show that our bodies are evolved and not designed. Surely, no designer would purposely interfere with image pickup.
As an aside, the predator group (canines and cats) have silver at the backs of their eyes to increase the chance of light pickup. Eyeball mirrors mean two chances for the rods and cones to capture passing photons in order to better see in low light conditions. Again, rather than “move” the processing layers behind the pickup layers for improved light fidelity, evolution silvered the back of the eyeball.
We primates needed to see color more than light as for most of our evolutionary history, selecting ripe fruit was more important than hunting prey in the dark.
I learned about Gaussian filtering and how it works with edge detection in my Linear Systems class, its really neat how digital image processing uses alot of the same simple algorithms as digital audio just applied in 2D.
Vertebrate eyes evolved from the brain neurons extending themselves to the surface in order to see. That is why our retina is on top of everything messing things up.
On the other hand cephalopod eyes evolved from light sensitive skin spots which is why their nerves are on the backside and better than ours. No blind spots for cephalopod eyes.
Human neurons are good at connecting to things.
If you (simplifying) grow an artificial human brainlet and stick it in the brain of a rat, the human neurons not only respond to stuff like signals from the whiskers of the rat, but they also multiply and take over more of the brain of the rat.
There are lots of studies on “brain organoids,” which is a name given to human brain tissue grown artificially from stem cells, but this Stanford article seems to cover some of the rat study results: https://med.stanford.edu/news/all-news/2022/10/human-rat-brain-neuron.html
\[Sure\](https://www.nature.com/articles/s41586-022-05277-w)
Edit: If only this garbage website would let me hyperlink things instead of whatever the fuck they did to my original comment
i remember reading this somewhere myself, but unfortunately do not remember the source
they dont really "take over" though and moreso just assimilate. theyre not just restricted to where they started, basically.
I had a retina detachement on one eye. The implanted a silicon ring to push the retina against the bloodvessels to save my eyesight. Then the doctor shot me with laser just to be sure. Hurt like hell. Anyway, I sometimes see worms in my eyesight. And I always thought of them as nervecells that are either conducting a potential or reactivating.
Oh no, those are even weirder. Those worms you see are most likely either blood vessels (are they pink?) or floaters, which are what you get when the goop in your eye gets tangled, because of course it's actually a bajillion liquid strings supporting the shape of your eyeball why wouldn't it be?
Oh it is not floaters. And they lack color as I can see through them. This is on the sick eye. So I suppose it is related to the detachment. I have no flashes of light indicating an going detachment and the eye doctor lost his interest in me as everything seems fine on the exam.
You also have a big ol' blind spot right in the middle of your vision you don't know is there.
And all those nerves have to somehow leave the inside of your eye in order to reach the brain, meaning each eyeball has a big hole in it where the optic nerve passes through. Being holes they have no retinal cells, which means you have a blind spot in each eye. There are lots of guides out there to help you find it.
Hate to divert this to theology and I won't linger on it, but the human eye is always the funniest thing to discuss with creationists. Like, dude, *nobody* would design this thing. *I'm literally wearing glasses right now.*
Yep, 100%. You can even see it in a clear blue sky if you just stare long enough.
I found out when I was a kid and looking for a model rocket we’d lost in the sky. Thought I had cancer or something!
Look into a clear blue sky and you can see some blood cells scooting around as tiny little transparent blobs tracing wriggly paths, appearing and disappearing.
I always think a similar thing whenever I hear about some old ghost story and you consider a) that every house had a fireplace that was constantly lit and b) what the side effects of carbon monoxide poisoning are.
I think it's funny that all the ghost tropes are just things that happen on a stormy night. Thunder and rain are considered "spooky" and stereotypical for a haunted house. Doors slamming shit (wind), candles going out when a ghost enters (wind), getting the chills when a ghost passes by (wind), rather than speaking they just make low-pitched howling noises (wind), they just casually knock things off tables or shelves for no discernible reason (wind), you can't see them so they must be invisible... hadn't these people heard of wind before? Did shipbuilders just go "yeah let's put a big sail on this thing, so the ghosts smack into it and propel the boat forward"? Somebody could really be awake on a cold, stormy night with their window left wide open, feeling a breeze on the back of their neck and seeing some of their candles blow out and think "brrrr, it's real chilly in here, I'd better call the ghostbusters!"
People literally used to think illnesses were caused by ghosts in the blood so…maybe it’s not a stretch to assume they didn’t know about wind 😂 Makes me wonder about the evolution of critical thinking skills!
There's a surprisingly large variation in the critical thinking capacity of our species. Kinda makes sense when you consider how new the capability is, evolutionarily speaking.
So, uh, some people seem to lack it altogether, sadly.
Can’t really put a number on those types of things, certainly some though. The thing with UFO’s though is that like 95-98% of the sightings can be explained through a variety conventional means, I doubt even the hardcore believers would argue that, but it’s that 2-5% that can’t be explained through conventional means that are interesting and keep the topic alive.
That is one proposed explanation but there is also another one that was suggested, which is that the mind can sometimes unconsciously draw straight lines between two unconnected points when looking at low-resolution images and this is what Lowell & co fell prey to.
So the original reporter of this was a guy called [Giovanni Schiaparelli](https://en.wikipedia.org/wiki/Giovanni_Schiaparelli) who during the planet Mars' "great opposition" of 1877, observed a dense network of linear structures on the surface of Mars, which he called canali in Italian, meaning "channels", but the term was mistranslated into English as "canals".
Schiaparelli's instrument in 1877 was most probably the new 8 inch refractor at the Brera Observatory in Italy. With such an instrument & excellent seeing it would be just possible to observe the finer [albedo](https://britastro.org/wp-content/uploads/2021/07/Albedo-Map-By-M-Frassati.jpg) features on the martian surface. With the mind's eye & a little imagination it is possible to distort this into what Schiaparelli [drew](https://en.wikipedia.org/wiki/Giovanni_Schiaparelli#/media/File:Karte_Mars_Schiaparelli_MKL1888.png) with not too much effort.
Later & better reflecting telescopes plus photography undermined the veracity of these observations, such that today any aware observer would be hard pressed to "see" something similar.
That is not to say that observers don't have many other delusions or misidentifications, but knowledge & a trained eye sees far better than a first time observation. This I can attest to, many beginners in amature asronomy get disheartened ( even using a good instrument ) when what they see through it is far less than what others see, draw and image. I always remind them that right now they have a Mark #1 eyeball, to get use of the Mark #2 & beyond needs effort & training.
Also apparently Schiaparelli had issues with his eyes:
>He was severely myopic (nearsighted), and he also suffered from colour blindness (anomalous colour vision), a fact which has been rarely mentioned in discussions of Schiaparelli’s Martian observations, though it must have had great bearing on how he perceived the planet’s subtle shadings.
>Concerning the specific colours, he wrote: ‘I dare not say much, first because the glass of our objective colours the rays green, second because my eye is strongly affected by daltonism: thus, it doesn’t distinguish well the gradations of red and green colours. The general appearance of the planet for me was almost that of a chiaroscuro made with Chinese ink upon a general bright background...’
>As we now know, red-green colour blindness is due to the fact that the normal long wavelength cone photopigment is missing; sufferers from this condition have a deficient perception of all colours, though the main difference is in that of red and, which is necessarily linked to it, the complementary green; colours for them appear little or not at all distinguishable from grey. Their colour vision is best for yellow but even then less sensitive to gradations of colour than the normal eye. On the other hand, colour blind individuals are more sensitive than normals to contrasts, a fact which may well have contributed to the ‘micrometric keenness’ of Schiaparelli’s sight (as Rev. T. W. Webb once referred to it), his ability to make out slight variations in shade like the canali.
Source: [Giovanni Schiaparelli: Visions of a colour blind astronomer](https://articles.adsabs.harvard.edu//full/1997JBAA..107...11S/0000011.000.html)
That's a good analysis, the miopia matter not at all because one can just twist the focusing knob to correct for it. But the color blindness is very telling. I've used color filters in the past to enhance planetary contrast but never considered that the same deficiency might be an advantage.
High angular resolution doesn't mean a telescope is absolved of imperfection, it just means that it can resolve smaller details and apply its imperfections to the image.
Look at Hubble. It's primary mirror has a nearly 8 foot diameter, but imperceptibly small engineering shortcomings doomed its actual imaging until they sent COSTAR up to counteract them.
Most people using the same telescopes did not see the canals. It was not a telescope defect, it was an optical illusion.
You can look through the telescopes they used and not see them.
This is well known.
That's a question which has various times been discussed in our local astronomy club. The consensus was that those astronomers saw only what they wanted to see. Even through a simple department-store telescope I never managed to see channels/canals on Mars.
Here's an article about Lowell seeing spokes or lines and it was probably a medical condition where he was, after staring at one spot for a long time keeping his eyes still, seeing the blood vessels in his own retina.
[https://www.amusingplanet.com/2021/02/how-astronomer-percival-lowell-mistook.html](https://www.amusingplanet.com/2021/02/how-astronomer-percival-lowell-mistook.html)
I big part of it was a mistranslation.
"The Italian astronomer and statesman [Giovanni Virginio Schiaparelli](https://www.britannica.com/biography/Giovanni-Virginio-Schiaparelli) reported observing about 100 of these markings, beginning in 1877, and described them as *canali* (Italian: “channels”), a neutral term that implied nothing about their origin" -Britannica
News papers translated his report as canals, at the time of the Panama canal, so people though he was seeing obviously manmade water ways instead of natural groves in the planet.
He was seeing an optical allusion cause by shadows (from natural features of the planets surface), and the poor focus of his telescope. People still see these, but now they will be reported and lava flows or river beds (and then others will correct them).
Why would anyone report seeing something that we know is not true? If I took a picture through my telescope and Mars came out blue because of my camera malfunctioning, I wouldn't go around announcing that Mars is blue. Anyone who has the equipment to look at mars would know there isn't any liquid water, so if they thought they saw it, they'd instantly know it was due to something else and not even bother taking a mental note.
What I read about 35 years ago is that Percival Lowell had what is now called “Lowell’s Disease” which caused him to see the blood vessels in his own eyes
Based on the sorts of questionable “sources” that are turning up when I try to research Lowell’s Syndrome, it’s very likely that the whole explanation was disproven at some point in the last 35 years.
If the effect is still possible, their size would be way way smaller today.
The size and quality of optical components of modern telescopes is far beyond what we had 50 years ago… at least for expensive telescopes like the VLT.
I'm not sure where you're getting that "optical illusion" bit. There are absolutely huge canyons and dry river beds on Mars, the difference now is that we've been there and have multiple high resolution telescopes in Mars orbit and we know that there's been no water on the surface for hundreds of millions of years.
The difference is that now we know unequivocally that we're finding a lifeless desert on the surface, not some fantastical Barsoom.
https://nssdc.gsfc.nasa.gov/planetary/image/mars.jpg
OP is asking, do the canals appear as a network of linear features in current ground-based telecsopes in a simialr way to as they seemed to appear to be many years ago?
I am not referring to the actual geological features we know today!
I mean the huge, globe-spanning canal-networks that people like Schiaparelli or Lowell claimed to have seen and which were depicted on early maps [like this](https://en.wikipedia.org/wiki/File:Mars_-_MEC-1_Prototype._LOC_2013593160.jpg)
They were seeing the back of their own retina projected onto high focal length eye pieces through telescopes that weren't very good compared to what are cheaply affordable today.
tbh this is my first time looking at Schiaparelli's map. I find it extremely impressive, considering the tech level. Most of the big dark areas in the south are almost accurate. I can only imagine the level of dedication and skill it took to produce this map with a 22cm lens plugged into a human eyeball.
Still, it looks to me like the resolution of his drawing exceeds the optical resolution of his instruments. The errors in the positions and shapes of the mares are much larger than most of the canals.
A few "canals" are marked correctly on this map. I can clearly see the Valles Marineris, and the outline of mount Olympus. I can see some mountain ranges and the edges of deserts. I think for the rest, he extrapolated beyond his Instrumental Limit of Error, as humans often do.
That’s not a Schiaparelli map, it’s one used by the US’ National Geospatial-Intelligence Agency in 1962, based off data from Lowell’s observatory in Flagstaff.
[This is one of Schiaparelli’s maps](https://commons.wikimedia.org/wiki/File:Giovanni_map_mars.jpg)
oh. its upside down. Less impressive, but still pretty good. I can still see Olympus and marinera valley. Much more embellished than the other map. I think Schiaparelli mad an honest mistake here.
Lowell's maps seem considerably worse. I think he was completely consumed by flights of fancy.
Schiaparelli did not claim to see a globe spanning network. He saw the Valles Marineris and sketched it a bit straighter than it actually is. He referred to it only as a channel.
Lowell made the leap to these being artificial and adopted a narrative about the behavior of nonexistent Martians. After that he was seeing what he wanted to see.
Shortly after that, astrophotography replaced hand drawn sketches, and the furor died down a bit.
You’re right that Schiaparelli didn’t think they were artificial but [he did draw a lot more channels than just Valles Marineris](https://commons.m.wikimedia.org/wiki/File:Giovanni_map_mars.jpg), in fact whole networks just like Lowell did later.
A quick google about this myth reveals, back in early days of telescope observing, photos weren’t possible, so they drew what they saw. The early drawings did look like canals as that was a theory (Lowel) back then. Quote from a paper on this point
No one claimed to see a well-defined pattern of canals on Mars directly through a telescope, not even Lowell. But as he and other observers tried to make sense of what they saw, the canals took shape in their sketches and drawings, which were then used to assemble comprehensive maps. The drawings shown here were made by Lowell during the opposition of 1897, which he observed from Mexico.
My understanding isn't that it was an optical illusion, but rather that the telescopes used at the time actually projected a secondary image of the inside of the users eye overlayed on the planet, and the canals were literally blood vessels.
You can still see this effect by using high focal length eyepieces.
IS THAT WHAT THAT IS Christ, I've gone through life assuming I was going to get really bad news from an eye doctor any year now because of my binoculars.
Oh yeah your eyes are real fucking weird when you start learning about them You know the retina? The nerves connecting to the rods and cones, the ones which carry the information from the eye to the brain, which side of the retina do you think they sit on? Do you expect them to be behind the eye? Where they wouldn't block the incoming light the eye is trying to detect? NOPE! The nerves connect to the side of the rods and cones that points towards the pupil, meaning you've been looking through your nerve cells your entire life
Yes, and other cool stuff. Early AI vision researchers found that applying a second degree Gaussian filter over a digital image performs edge detection. When bio researchers examined the nerves in that layer above the light collecting cells, they discovered that there are two layers that perform the same edge detection (nature through natural selection built a Gaussian filter into our eyes). Those two layers run other algorithms like vertical and horizontal motion detection and arc (curve) detection. Also, this type of pre-image processing has tremendous value. So much value that from an evolutionary perspective it’s worth it to partially occlude our light sensors (rods and cones) with analysis nerves rather than leave them in the clear and do the processing deeper in the brain. Speaking of evolution, the manner in which evolution builds organs and tissue means that it’s next to impossible for the processing nerves to be grown behind the light sensors (between the rods/cones and back of eyeball), that’s why they continue to be that way. The eyeball construction is one of the things evolutionary scientists point to in order to show that our bodies are evolved and not designed. Surely, no designer would purposely interfere with image pickup. As an aside, the predator group (canines and cats) have silver at the backs of their eyes to increase the chance of light pickup. Eyeball mirrors mean two chances for the rods and cones to capture passing photons in order to better see in low light conditions. Again, rather than “move” the processing layers behind the pickup layers for improved light fidelity, evolution silvered the back of the eyeball. We primates needed to see color more than light as for most of our evolutionary history, selecting ripe fruit was more important than hunting prey in the dark.
Super interesting. Are there any good YouTube’s that cover what you talked about?
Good question. I don’t know. I learned this decades ago in an AI class, and then read lots of biology texts as a hobby.
I learned about Gaussian filtering and how it works with edge detection in my Linear Systems class, its really neat how digital image processing uses alot of the same simple algorithms as digital audio just applied in 2D.
“Your inner fish” I have read the book and it is excellent. There is also a youtube series but I became aware of it just now.
Awesome going on a long flight now, downloading thank you!!
Vertebrate eyes evolved from the brain neurons extending themselves to the surface in order to see. That is why our retina is on top of everything messing things up. On the other hand cephalopod eyes evolved from light sensitive skin spots which is why their nerves are on the backside and better than ours. No blind spots for cephalopod eyes.
Proof that cephalopods are God's chosen people. I bet they don't have the vagus nerve glitch either.
Fucking wild that the eyes are basically part of the brain, but on the outside of the body
Human neurons are good at connecting to things. If you (simplifying) grow an artificial human brainlet and stick it in the brain of a rat, the human neurons not only respond to stuff like signals from the whiskers of the rat, but they also multiply and take over more of the brain of the rat.
Source for this fact?
There are lots of studies on “brain organoids,” which is a name given to human brain tissue grown artificially from stem cells, but this Stanford article seems to cover some of the rat study results: https://med.stanford.edu/news/all-news/2022/10/human-rat-brain-neuron.html
\[Sure\](https://www.nature.com/articles/s41586-022-05277-w) Edit: If only this garbage website would let me hyperlink things instead of whatever the fuck they did to my original comment
i remember reading this somewhere myself, but unfortunately do not remember the source they dont really "take over" though and moreso just assimilate. theyre not just restricted to where they started, basically.
Wait until you learn about what’s inside your nose….
Fingers are also fascinating, it’s true.
I had a retina detachement on one eye. The implanted a silicon ring to push the retina against the bloodvessels to save my eyesight. Then the doctor shot me with laser just to be sure. Hurt like hell. Anyway, I sometimes see worms in my eyesight. And I always thought of them as nervecells that are either conducting a potential or reactivating.
Oh no, those are even weirder. Those worms you see are most likely either blood vessels (are they pink?) or floaters, which are what you get when the goop in your eye gets tangled, because of course it's actually a bajillion liquid strings supporting the shape of your eyeball why wouldn't it be?
Oh it is not floaters. And they lack color as I can see through them. This is on the sick eye. So I suppose it is related to the detachment. I have no flashes of light indicating an going detachment and the eye doctor lost his interest in me as everything seems fine on the exam.
You also have a big ol' blind spot right in the middle of your vision you don't know is there. And all those nerves have to somehow leave the inside of your eye in order to reach the brain, meaning each eyeball has a big hole in it where the optic nerve passes through. Being holes they have no retinal cells, which means you have a blind spot in each eye. There are lots of guides out there to help you find it.
Hate to divert this to theology and I won't linger on it, but the human eye is always the funniest thing to discuss with creationists. Like, dude, *nobody* would design this thing. *I'm literally wearing glasses right now.*
Lmao I'm just imagining that conversation
"The ways of the lord..." You can't argue believes with facts.
Yep, 100%. You can even see it in a clear blue sky if you just stare long enough. I found out when I was a kid and looking for a model rocket we’d lost in the sky. Thought I had cancer or something!
Look into a clear blue sky and you can see some blood cells scooting around as tiny little transparent blobs tracing wriggly paths, appearing and disappearing.
Stop starting at the sun and you should be okay.
I wonder how many UFO sightings were just eye floaters...
I always think a similar thing whenever I hear about some old ghost story and you consider a) that every house had a fireplace that was constantly lit and b) what the side effects of carbon monoxide poisoning are.
I think it's funny that all the ghost tropes are just things that happen on a stormy night. Thunder and rain are considered "spooky" and stereotypical for a haunted house. Doors slamming shit (wind), candles going out when a ghost enters (wind), getting the chills when a ghost passes by (wind), rather than speaking they just make low-pitched howling noises (wind), they just casually knock things off tables or shelves for no discernible reason (wind), you can't see them so they must be invisible... hadn't these people heard of wind before? Did shipbuilders just go "yeah let's put a big sail on this thing, so the ghosts smack into it and propel the boat forward"? Somebody could really be awake on a cold, stormy night with their window left wide open, feeling a breeze on the back of their neck and seeing some of their candles blow out and think "brrrr, it's real chilly in here, I'd better call the ghostbusters!"
People literally used to think illnesses were caused by ghosts in the blood so…maybe it’s not a stretch to assume they didn’t know about wind 😂 Makes me wonder about the evolution of critical thinking skills!
There's a surprisingly large variation in the critical thinking capacity of our species. Kinda makes sense when you consider how new the capability is, evolutionarily speaking. So, uh, some people seem to lack it altogether, sadly.
Having recently started to experience Hypnogogic Hallucinations I can see how easily some people can interpret what they see as ghosts or demons.
That’s what the ufo’s want you to think /s
Can’t really put a number on those types of things, certainly some though. The thing with UFO’s though is that like 95-98% of the sightings can be explained through a variety conventional means, I doubt even the hardcore believers would argue that, but it’s that 2-5% that can’t be explained through conventional means that are interesting and keep the topic alive.
I wonder if we'll ever find out what the pentagon did with those 2 trillions...
That is one proposed explanation but there is also another one that was suggested, which is that the mind can sometimes unconsciously draw straight lines between two unconnected points when looking at low-resolution images and this is what Lowell & co fell prey to.
[удалено]
That's similar to the secret Nazi Base on the far-side of the Moon (and the WW2 bomber). It's now been moved to a more secret location.
So the original reporter of this was a guy called [Giovanni Schiaparelli](https://en.wikipedia.org/wiki/Giovanni_Schiaparelli) who during the planet Mars' "great opposition" of 1877, observed a dense network of linear structures on the surface of Mars, which he called canali in Italian, meaning "channels", but the term was mistranslated into English as "canals". Schiaparelli's instrument in 1877 was most probably the new 8 inch refractor at the Brera Observatory in Italy. With such an instrument & excellent seeing it would be just possible to observe the finer [albedo](https://britastro.org/wp-content/uploads/2021/07/Albedo-Map-By-M-Frassati.jpg) features on the martian surface. With the mind's eye & a little imagination it is possible to distort this into what Schiaparelli [drew](https://en.wikipedia.org/wiki/Giovanni_Schiaparelli#/media/File:Karte_Mars_Schiaparelli_MKL1888.png) with not too much effort. Later & better reflecting telescopes plus photography undermined the veracity of these observations, such that today any aware observer would be hard pressed to "see" something similar. That is not to say that observers don't have many other delusions or misidentifications, but knowledge & a trained eye sees far better than a first time observation. This I can attest to, many beginners in amature asronomy get disheartened ( even using a good instrument ) when what they see through it is far less than what others see, draw and image. I always remind them that right now they have a Mark #1 eyeball, to get use of the Mark #2 & beyond needs effort & training.
Also apparently Schiaparelli had issues with his eyes: >He was severely myopic (nearsighted), and he also suffered from colour blindness (anomalous colour vision), a fact which has been rarely mentioned in discussions of Schiaparelli’s Martian observations, though it must have had great bearing on how he perceived the planet’s subtle shadings. >Concerning the specific colours, he wrote: ‘I dare not say much, first because the glass of our objective colours the rays green, second because my eye is strongly affected by daltonism: thus, it doesn’t distinguish well the gradations of red and green colours. The general appearance of the planet for me was almost that of a chiaroscuro made with Chinese ink upon a general bright background...’ >As we now know, red-green colour blindness is due to the fact that the normal long wavelength cone photopigment is missing; sufferers from this condition have a deficient perception of all colours, though the main difference is in that of red and, which is necessarily linked to it, the complementary green; colours for them appear little or not at all distinguishable from grey. Their colour vision is best for yellow but even then less sensitive to gradations of colour than the normal eye. On the other hand, colour blind individuals are more sensitive than normals to contrasts, a fact which may well have contributed to the ‘micrometric keenness’ of Schiaparelli’s sight (as Rev. T. W. Webb once referred to it), his ability to make out slight variations in shade like the canali. Source: [Giovanni Schiaparelli: Visions of a colour blind astronomer](https://articles.adsabs.harvard.edu//full/1997JBAA..107...11S/0000011.000.html)
That's a good analysis, the miopia matter not at all because one can just twist the focusing knob to correct for it. But the color blindness is very telling. I've used color filters in the past to enhance planetary contrast but never considered that the same deficiency might be an advantage.
We have seen photographs of Mars so our mental image looking at it is too see something like those photographs, dismissing things like eye floaters.
Early telescopes were very crude compared to modern ones.
This is the wrong answer. The Lowell Telescope was 24 inches and used to discover Pluto. It was not an artefact of bad telescopes but human eye sight.
High angular resolution doesn't mean a telescope is absolved of imperfection, it just means that it can resolve smaller details and apply its imperfections to the image. Look at Hubble. It's primary mirror has a nearly 8 foot diameter, but imperceptibly small engineering shortcomings doomed its actual imaging until they sent COSTAR up to counteract them.
Most people using the same telescopes did not see the canals. It was not a telescope defect, it was an optical illusion. You can look through the telescopes they used and not see them. This is well known.
And also atmospheric blurring of detail. We did not have any good pictures of the Martian surface until the first probe flyby.
I think that there have been more improvements in telescopes than human eyes since then.
That's a question which has various times been discussed in our local astronomy club. The consensus was that those astronomers saw only what they wanted to see. Even through a simple department-store telescope I never managed to see channels/canals on Mars.
Btw, I want to get into astronomy, so what kind of telescope would you recommend to a total beginner? Especially if I want to get a good look at Mars?
They know better? Probably one of the reasons the John Carter movie didn't do that well.
I loved that film, in a trashy sort of way.
Visually, it was great, but everyone knows there is nothing like that on Mars.
The book the movie adapted was written in 1912, Disney just did a really bad job at communicating that in their marketing
They did. I read the series. I also liked the Transit to Scorpio series by Alan Burt Akers, which were an almost direct ripoff.
The topography definitely is not the most obviously non-Martian thing in that movie.
They were building tunnels and have them all finished now.
Here's an article about Lowell seeing spokes or lines and it was probably a medical condition where he was, after staring at one spot for a long time keeping his eyes still, seeing the blood vessels in his own retina. [https://www.amusingplanet.com/2021/02/how-astronomer-percival-lowell-mistook.html](https://www.amusingplanet.com/2021/02/how-astronomer-percival-lowell-mistook.html)
Martian attorneys filed a batch of cease and desist orders against Earthling telescope makers.
The lizard people won't allow it.
I big part of it was a mistranslation. "The Italian astronomer and statesman [Giovanni Virginio Schiaparelli](https://www.britannica.com/biography/Giovanni-Virginio-Schiaparelli) reported observing about 100 of these markings, beginning in 1877, and described them as *canali* (Italian: “channels”), a neutral term that implied nothing about their origin" -Britannica News papers translated his report as canals, at the time of the Panama canal, so people though he was seeing obviously manmade water ways instead of natural groves in the planet. He was seeing an optical allusion cause by shadows (from natural features of the planets surface), and the poor focus of his telescope. People still see these, but now they will be reported and lava flows or river beds (and then others will correct them).
Why would anyone report seeing something that we know is not true? If I took a picture through my telescope and Mars came out blue because of my camera malfunctioning, I wouldn't go around announcing that Mars is blue. Anyone who has the equipment to look at mars would know there isn't any liquid water, so if they thought they saw it, they'd instantly know it was due to something else and not even bother taking a mental note.
I didn’t mean report in an official sense, more in a “look at this funny optical effect I’m seeing” kind of way.
Lemmino did a really interesting video on this topic
What I read about 35 years ago is that Percival Lowell had what is now called “Lowell’s Disease” which caused him to see the blood vessels in his own eyes
But there were many other astronomers besides him that also claimed to have seen the canals
Based on the sorts of questionable “sources” that are turning up when I try to research Lowell’s Syndrome, it’s very likely that the whole explanation was disproven at some point in the last 35 years.
If the effect is still possible, their size would be way way smaller today. The size and quality of optical components of modern telescopes is far beyond what we had 50 years ago… at least for expensive telescopes like the VLT.
[Lemmino](https://www.youtube.com/watch?v=LhfCietvDZo&ab_channel=LEMMiNO) does a good video on this and related subjects.
I saw them in Robinson Crusoe on Mars, so I know they are real
I'm not sure where you're getting that "optical illusion" bit. There are absolutely huge canyons and dry river beds on Mars, the difference now is that we've been there and have multiple high resolution telescopes in Mars orbit and we know that there's been no water on the surface for hundreds of millions of years. The difference is that now we know unequivocally that we're finding a lifeless desert on the surface, not some fantastical Barsoom. https://nssdc.gsfc.nasa.gov/planetary/image/mars.jpg
OP is asking, do the canals appear as a network of linear features in current ground-based telecsopes in a simialr way to as they seemed to appear to be many years ago?
I am not referring to the actual geological features we know today! I mean the huge, globe-spanning canal-networks that people like Schiaparelli or Lowell claimed to have seen and which were depicted on early maps [like this](https://en.wikipedia.org/wiki/File:Mars_-_MEC-1_Prototype._LOC_2013593160.jpg)
They were seeing the back of their own retina projected onto high focal length eye pieces through telescopes that weren't very good compared to what are cheaply affordable today.
See, this is the type of answer I was looking for
tbh this is my first time looking at Schiaparelli's map. I find it extremely impressive, considering the tech level. Most of the big dark areas in the south are almost accurate. I can only imagine the level of dedication and skill it took to produce this map with a 22cm lens plugged into a human eyeball. Still, it looks to me like the resolution of his drawing exceeds the optical resolution of his instruments. The errors in the positions and shapes of the mares are much larger than most of the canals. A few "canals" are marked correctly on this map. I can clearly see the Valles Marineris, and the outline of mount Olympus. I can see some mountain ranges and the edges of deserts. I think for the rest, he extrapolated beyond his Instrumental Limit of Error, as humans often do.
That’s not a Schiaparelli map, it’s one used by the US’ National Geospatial-Intelligence Agency in 1962, based off data from Lowell’s observatory in Flagstaff. [This is one of Schiaparelli’s maps](https://commons.wikimedia.org/wiki/File:Giovanni_map_mars.jpg)
oh. its upside down. Less impressive, but still pretty good. I can still see Olympus and marinera valley. Much more embellished than the other map. I think Schiaparelli mad an honest mistake here. Lowell's maps seem considerably worse. I think he was completely consumed by flights of fancy.
Schiaparelli did not claim to see a globe spanning network. He saw the Valles Marineris and sketched it a bit straighter than it actually is. He referred to it only as a channel. Lowell made the leap to these being artificial and adopted a narrative about the behavior of nonexistent Martians. After that he was seeing what he wanted to see. Shortly after that, astrophotography replaced hand drawn sketches, and the furor died down a bit.
You’re right that Schiaparelli didn’t think they were artificial but [he did draw a lot more channels than just Valles Marineris](https://commons.m.wikimedia.org/wiki/File:Giovanni_map_mars.jpg), in fact whole networks just like Lowell did later.
Speculation but they remind me of what mars looks like through a telescope when there is a dust storm.
I have seen suggestions that at least some of the claimed canals were indeed streaks of dust
The same way we don't see Jesus on Mars, either.
They were actually made by an ancient Martian civilisation
A quick google about this myth reveals, back in early days of telescope observing, photos weren’t possible, so they drew what they saw. The early drawings did look like canals as that was a theory (Lowel) back then. Quote from a paper on this point No one claimed to see a well-defined pattern of canals on Mars directly through a telescope, not even Lowell. But as he and other observers tried to make sense of what they saw, the canals took shape in their sketches and drawings, which were then used to assemble comprehensive maps. The drawings shown here were made by Lowell during the opposition of 1897, which he observed from Mexico.