See “true cyan”!

February 10, 2022 • 2:00 pm

This video supposedly enables you to see a color that apparently can’t be reproduced on the screen: “true cyan“, a color between green and blue.   Turn on the sound, put your face about a foot from the screen, and then fix your gaze on the white dot in the center for the duration of the soundtrack. When the music ends, close your eyes, and with luck you’ll have an afterimage of the “true cyan” color. It is a lovely blue.

This source gives a bit more information:

True cyan illusion

Even though the human eye is incredibly sophisticated, there are times when you can trick your brain into seeing things that completely bizarre. For example, we know that there are three primary colours – red, yellow and blue – and all other colours are formed by mixing them. There are still shades of colour that often occur naturally and are difficult to produce on electronic screens.

What if we tell you there’s a colour known as true cyan, which is a greenish-blue pigment and is difficult to capture on television and is often diluted to a lesser form?

An optical illusion posted on social media has left netizens amazed as they could see the dazzling green-blue pigment.

TikTok user Kate Bacon posted a video telling people that would show them a colour that they’ve probably never seen before. She said, “It’s called true cyan, and most TVs and monitors aren’t capable of producing this pigment.”

Viewers are shown a red circle with a white dot against a blue background. Kate says that you need to stare at the white dot for at least 30 seconds, but the longer the better. Afterwards, if you close your eyes really tightly, you should see a ‘glowing orb’ in the colour of true cyan.

A similar video available on Youtube instructs the viewer to stare at the white dot in the centre of the red circle as the camera slowly pans out. By the time the video ends, the viewer will be able to see the true cyan colour appear like a halo around the red circle.

A mirage of Chicago

April 13, 2020 • 12:45 pm

Reader Edward sent this breathtaking photo of a mirage of the Chicago Skyline, just featured as the Earth Science Photo of the Day.  It was taken in 2008 from the Indiana Dunes, a state park 37 miles from the city, and a place from which the city isn’t visible.  It is in fact an inferior mirage, formed only under special atmospheric conditions (see also here). Those distant “puddles of water” that you see far away on a hot highway, for instance, are inferior mirages of the sky. Read more at the first link, including details about the equipment and how the photo was taken.

Optical illusion: the Troxler effect

April 10, 2018 • 2:30 pm

Have a look at the video below, which demonstrates “the Troxler effect” or “Troxler fading”, a phenomenon that occurs when you try to stop the involuntary movements of your eye (“scanning”):

As we focus on a certain point in our perception field, that point becomes the main object of our visual system. When a blurry stimulus appears in a region of the visual field further from the point we are fixating, and we keep our eyes still, that stimulus will disappear even though it is still there. The phenomenon is known as Troxler’s fading. It occurs because even if our eyes move a little when we are fixating a point, away from that point, in the perception field, the movements aren’t large enough to observe other elements. The neurons remain focused on the main object and our visual system doesn’t involve new ones for the other elements.

Here’s an example from Wikipedia:

In this example, the spots in the “lilac chaser” illusion fade away after several seconds when the black cross is stared at long enough. This leaves a grey background and the cross. Some viewers may notice that the moving space has faded into a moving blue-green spot, possibly with a short trail following it. Furthermore, moving one’s eyes away from the image after a period of time may result in a brief, strong afterimage of a circle of green spots.

And here’s the most obvious picture to use to demonstrate the effect: a Cheshire cat!

INSTRUCTIONS. Keep very still and keep your gaze focused on the central black cross. Do not strain your eyes, but try not to let your gaze wander from the cross.

You can read more on the Troxler Effect here, including this:

The Troxler Effect is named after Swiss physician and philosopher Ignaz Paul Vital Troxler (1780-1866). In 1804, Troxler made the discovery that rigidly fixating one’s gaze on some element in the visual field can cause surrounding stationary images to seem to slowly disappear or fade. They are replaced with an experience, the nature of which is determined by the background that the object is on. This is known as filling-in.

The Troxler effect illustrates the importance of saccades, the involuntary movements of the eye which occur even while one’s gaze is apparently settled. If we could perfectly fixate on some point in our visual field by suppressing saccadic movement, a static scene would slowly fade from view after a few seconds due to the local neural adaptation of the rods, cones and ganglion cells in the retina. In brief, any constant light stimulus will cause an individual neuron to become desensitized to that stimulus, and hence reduce the strength of its signal to the brain.

When we attempt to fix our gaze on an object, the eye undergoes extremely rapid and relatively large-scale sudden movements called microsaccades, in contrast to saccadic drifts or small oscillations. Microsaccades cause the pattern of activity which forms the retinal image to shift across hundreds of photoreceptors at a time, providing a constant “refreshing” of the image (Martinez-Conde 2010).


Still more on the color illusion

February 18, 2018 • 7:45 am

Well, a reader showed in an email that that the hearts in the illusion below really were very slightly different colors due to the compression algorithms used in making the image. (However, those slight differences do not account for the striking perceptual effect).  The reader who demonstrated this anomaly won an autographed book from Matthew.

HOWEVER, reader Mel made his own illusion, so we know that here the colors of the squares really are identical. His notes:

To demonstrate the phenomenon a bit more cleanly I constructed the following image using a spreadsheet. I used very small cells (0.3 cm x 0.3 cm) and filled them with various colors and then took a screenshot. The image still shows the illusion and only three colors were used in constructing the image (magenta, orange, blue-green).

And another demonstration using magic markers. I think the efficacy of the lines in fooling viewers about the color has been shown. We’ll now leave this illusion behind and move on.

Yesterday’s optical illusion: the hearts are the same color!

February 17, 2018 • 7:15 am

On yesterday’s Hili Dialogue, I posted this tweet, an optical illusion provided by Matthew:

The hearts are said to be the same color, with the illusion of their being different colors due to the different-colored stripes running through them. The was lots of argument among the readers, and, as far as I can remember, no consensus.

I put this question to Matthew (why do you readers make me do these things?), and he responded by checking. Here’s his response and his image. The conclusion is that the hearts are both the same color: a blue-tinted green.

They are the same colour. I have been in and checked the image, see here. The left half, with the orange, is from the ‘green’ heart. The right half, with the pink, is from the ‘blue’ heart.

Another response showing the color identity:

I think this settles it: if Matthew’s satisfied, so am I. However, if you can prove to Matthew’s satisfaction that they are really of different colors, you will win an autographed copy of his latest (and terrific) book: Life’s Greatest Secret, about the cracking of the genetic code. The first one to disprove color identity of the hearts will get the book. You can email me or put your “proof” in the comments.

Matthew sets out the rules:

People need to download the original large image (attached) and then enlarge it to show they are differerent colours. They won’t be able to do it.

Friday: Hili dialogue

October 13, 2017 • 6:30 am

OMG: it’s Friday the 13th (October, 2017), supposedly an unlucky day. But the odds are there will be at least one such day per year given that there are 12 thirteenths per year and only seven days of the week. And yesterday, at least, was lucky for the Chicago Cubs, who won the Central Division of the National League with a squeaker 9-8 victory over the Washington Nationals—in a game lasting over 4.5 hours. Our Cubbies now face the National League champions series against the Los Angeles Dodgers, and if they win that one they’re on to the World Series again. It looks as if baseball might extend into November this year, an outcome I predicted long ago, when I said that one day the American baseball, football, and basketball seasons would all overlap. On the down side, Trump started dismantling Obamacare by executive order and is about to use Congress to scrap the nuclear deal with Iran. 

It’s National M&M’s Day, and how many of you haven’t eaten one? Here are some fun facts about the ubiquitous candy introduced in 1940 (the first five are from Foodimentary):

  1. From 1976 to 1985, there were no red M&Ms (see below)
  2. Blue M&Ms were introduced in 1995.
  3. M&Ms were taken along on the first space shuttle voyage in 1982.
  4. There are 340 million M&M’s produced daily. [JAC: Wikipedia now says 400 million]
  5. The “M&M” was modeled after a candy Forrest Mars, Sr. encountered while in Spain during the 1930s. During the Spanish civil war there, he observed soldiers eating chocolate pellets with a hard shell of tempered chocolate. This prevented the candies from melting, which was essential when included in soldiers rations as they were.
  6. (From Wikipedia) “The following is a summary of the changes to the colors of the flagship (milk chocolate) flavor of M&M’s, the only filling manufactured continuously since the beginning of the brand. From 1941 until 1969, each package contained M&M’s in five different colors; when red M&M’s were reintroduced in 1987, they were added as a sixth color instead of replacing any of the existing colors.”

Bring back the violet ones!! We’ll have an M&M based quiz in an hour or so.

It’s also the International Day for Disaster Reduction, which means to me a day on which we should impeach Trump. On this day in 1792, the cornerstone of the White House (the “Executive Mansion”) was laid. And, October 13, 1881, Hebrew revivalist Eliezer Ben-Yehuda had the first conversation in modern Hebrew with his friends. I had no idea that Hebrew was a dead language for a long time, which shows you what a bad (secular) Jew I am. On this day in 1884, the zero meridian for longitude was decreed by the International Meridian Conference to pass through the Greenwich Observatory. On this day in 1903, the Boston Red Sox defeated the Pittsburgh Pirates to win the first “modern” World Series.  The Sox won again in 1918, but then had a long drought, not winning again until 2004. The only longer “Series Drought” was by our Cubbies, who won last year after not winning since 1908. On this day in 1917, the so-called “Miracle of the Sun” occurred in Fátima Portugal, where some solar anomaly was witnessed by 70,000 people. It was most likely either mass hallucination or an atmospheric anomaly; see here for other explanations). Here’s a Portuguese newspaper reporting the event, officially recognized by the Vatican as a “miracle.”

Finally, on October 12, 1983, the first cellular network began; it was set up in Chicago by Ameritech (now AT&T). And so we will always be connected. I know almost nobody who doesn’t have a cellphone.

Notables born on this day include Rudolf Virchow (1821), Wilfred Pickles (1904; I like the name), the cartoonist Herblock (1909), Lenny Bruce and Margaret Thatcher (both 1925), Paul Simon (1941), Marie Osmond (1959), and Sacha Baron Cohen (1971). Those who died on this day include Milton S. Hershey (1945; chocolate magnate) Ed Sullivan (1974) and Lê Đức Thọ (1990).  Here’s a 1978 clip of Barbara Walters interviewing Donnie and Marie Osmond, asking them why blacks can’t be priests in their Mormon faith. (Church officials had a “revelation” in 1978 in which God said it was okay after all.) Watch Donnie equivocate!

Meanwhile in Dobrzyn, the Editor in Chief is issuing orders:

Hili: Efficient management requires delegation.
A: So what am I supposed to do?
Hili: Think for yourself and start thinking from the kitchen.
In Polish:
Hili: Sprawne zarządzanie wymaga delegowania.
Ja: Czyli co mam zrobić?
Hili: Sam pomyśl, zacznij myślenie od kuchni.

And from Winnipeg we have a photo of Gus that his staff calls “a nice picture”. Indeed. Look at that adorable face, stuffy ears (the result of frostbite) and snow white fur!

Finally, a tw**t from Matthew, who loves optical illusions:

Saturday: Hili dialogue

September 16, 2017 • 6:30 am

It’s Caturday, September 16, 2017, and in a few hours I’ll haul my weary carcass to the Chopin Airport in Warsaw for the nine-hour flight back to Chicago. That means, of course, that posting will be light today. If my plane crashes, it’s been a good run. If it doesn’t, let’s hope the airplane movies are decent (and no, “Interstellar” didn’t suck because the screen was small; it sucked because the plot was dumb and the acting and script lame). In the news, I’m grateful that nobody was killed in London bombing, though 29 people were injured and ISIS has claimed responsibility. I note as well that Trump embarrassed himself, and angered the Brits, by unleashing a series of dumb tw**ts. I shudder to think that this parody of a leader might be reelected in a bit more than three years.

It’s National Peach Pie Day, and I’ll court sympathy by saying that my Days of Pie have ended. But Wikipedia adds that it’s also two other food days: National Guacamole Day and National Cinnamon-Raisin Bread Day. September 16 is also Cry of Dolores, celebrating the beginning of Mexico’s war of independence from Spain.

On this day in 1620, the Pilgrims left England for America on the Mayflower—or so says Wikipedia in its “September 16” entry. But the Mayflower entry says “the Mayflower sailed from Plymouth on September 6, 1620. . .”, so this is likely an error (if you’re an editor, correct it, please). The first winter in America killed off just over half of the hundred-odd Pilgrims. On September 16, 1814, Francis Scott Key finished his poem, “The Star-Spangled Banner”; its lyrics would become, in 1931, the words to America’s National Anthem—one of the worst of all such anthems. On this day in 1959, The first Xerox 914, the world’s first successful photocopier, was demonstrated on television in the U.S. Are you old enough to remember its predecessor: the mimeograph machine with its fragrant purple ink.

On this day in 1975, Papua New Guinea gained independence from Australia. And exactly one year later, the championship swimmer Shavarsh Karapetyan saved 20 people from drowning after a trolleybus went into the water in Yerevan, Armenia. Breaking the glass with his legs, he repeatedly dove down into the cold, silty water—30 times—(the bus was 10 m deep) to rescue people, after which he was in a coma for 46 days and got a bad infection, which ended his career as a swimmer. What a hero that man was! Did you even know that tale? (I didn’t.) And he later saved several people from death by running into a burning building.

Karapetyan’s photo is below. You can read about his heroism here, and here’s a quote from that link:

Bystanders who watched Shavarsh bring people up to the surface said that his feet and back were full of glass shards. When later asked, what was the most horrifying part of this, Shavarsh replied by saying:

“I knew that I could only save so many lives, I was afraid to make a mistake. It was so dark down there that I could barely see anything. One of my dives, I accidentally grabbed a seat instead of a passenger… I could have saved a life instead. That seat still haunts me in my nightmares.”

After his 30th dive, Shavarsh lost consciousness. This courageous act has cost him dearly; he incurred heavy 2-sided pneumonia and blood contamination from the polluted water. Doctors were unsure if Shavarsh would ever recover. His life was hanging on by a thread while he stayed unconscious for 46 days. He finally recovered, but was never able to compete again. Today’s experts agree that no one but Shavarsh could have done what he has done.

Karapetyan now lives quietly, running a shoe shop in Moscow.

Finally, on this day in 1992, Panamanian dictator Manuel Noriega was sentenced to 40 years in prison for drug trafficking and money laundering. Extradited to Panama in 2011, Noriega died in May of this year after brain surgery.

Notables born on this day include Clive Bell (1881), Nadia Boulanger (1887), Lauren Bacall (1924), B. B. King (1925) and Henry Louis Gates, Jr. (1950), Those who died on September 16 include Edward Whymper (1911), Maria Callas (1977), Mary Travers (2009), and Edward Albee (2016). And I’ve just noticed that Harry Dean Stanton died today. Meanwhile in Dobrzyn, Hili is suffering existential despair:

Hili: Not a single hope from anywhere.
A: What for?
Hili: That’s what I don’t know.
In Polish:
Hili: Znikąd nadziei.
Ja: Na co?
Hili: Właśnie nie wiem.

Matthew wants us all to see this illusion. Can you figure out how it was done? I think I can.

The proper hierarchy of beasts:

And a cartoon from readers jsp:

The Coffer illusion

August 11, 2017 • 3:52 pm

Okay, look at the photo of the door below. Time yourself from the start to see how long it takes you to find the circles.

How many circles do you see? Do you see any?

There are sixteen circles. Do you see them? If you don’t, and for an explanation, go to the next page by clicking “read more”

Continue reading “The Coffer illusion”