From a scientific perspective, “touching” an object is more complex than it seems. For all objects with mass, it appears they are touching, but in reality, they aren’t in physical contact. This phenomenon can be explained by two main factors.
First, the structure of atoms plays a crucial role. Atoms consist of positively charged protons and negatively charged electrons. Protons, along with neutral neutrons, form the nucleus at the center of the atom, while electrons orbit this nucleus.
According to the principles of electromagnetic force, opposite charges attract and like charges repel. When two atoms approach one another, their outer electrons typically repel due to their similar charges, leading to the sensation of not truly touching.
Another essential concept is Pauli’s Exclusion Principle. In simple terms, this principle states that no two electrons in the same atom can occupy the same quantum state, meaning their “orbitals” must differ.
This leads to a short-range repulsive force, referred to as Pauli’s Repulsion, affecting electrons and, consequently, atoms. Combined with electromagnetic forces, these interactions typically result in atoms repelling each other.
So when you “touch” an object, the atoms or molecules involved are usually repelled by one another, creating a small repulsive force that prevents real contact.
For instance, when you sit in a chair, you’re essentially floating on a cushion of subatomic repulsive forces.
While we may perceive that we are in contact with our surroundings, what we actually sense is a repulsive force – Credit: Getty
The reality is slightly more intricate. When we touch an object, a minimal chemical interaction may occur.
Some atoms can overcome electromagnetic repulsion, allowing them to exchange or share electrons with those of the object, forming bonds. This leads to the forces commonly associated with “friction,” but fundamentally, Pauli repulsion prevents true contact.
When you “touch” something, your body perceives this sensation, thanks to specialized sensory organs known as mechanoreceptors. These receptors respond to pressure and vibration, sending electrical signals to the brain, which interprets these signals as the sensation of “touch.”
Ultimately, these mechanoreceptors are detecting small repulsive forces between atoms and molecules, rather than direct physical contact. Hence, “touch” can be regarded as an illusion.
This article addresses the question raised by Josh Greene from Leeds: “Have you ever touched anything technically?”
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Fantasy is loved by all: it’s fun, intriguing, and messes with our minds.
There are various types of optical illusions, and science often struggles to explain why they deceive human perception. Our brains interpret information from our eyes and fill in the gaps to create what we see in our minds. However, this interpretation is not always accurate.
We’ve compiled some of our favorite visual tricks to challenge your brain.
Checker Shadow Illusion
Photo credit: Edward H. Adelson/Wikipedia
In the image above, rectangles A and B are the same color, although it seems impossible. To demonstrate this fact, here is a rectified image.
Photo credit: Edward H. Adelson/Wikipedia
It’s an example of a contrast illusion where two areas of the same color appear different based on circumstances.
In the checkered shadow illusion, the shadow cast by the green shape seems to darken light areas, creating a surprising effect. Vision scientists created this illusion, and it was developed by Edward Howard Adelson in 1995 to showcase the capabilities of the human visual system in interpreting image information.
Instead of being a flaw, this illusion highlights the effectiveness of our visual perception.
Cafe Wall Illusion
The Cafe Wall illusion. Straight lines appear to be non-straight. Photo credit: Fibonacci/Wikipedia
The Café Wall illusion is a geometric optical illusion where the straight boundaries between dark and light blocks appear curved.
Our brains perceive white areas as larger than black areas in a phenomenon known as the radial illusion. This perception can be changed by swapping white and black colors for lower-contrast colors.
When the color is changed, the lines appear straighter. Photo from Fibonacci/Wikipedia
This illusion, known by various names, was named “café wall illusion” by scientist Richard Gregory, inspired by the design on a café in Bristol, England.
Richard Gregory standing outside the café that inspired the name behind the café wall illusion. Photo by Stephen Battle/Wikipedia
Penrose triangle
3D illustration of the Penrose triangle. Photo courtesy of Getty Images
The Penrose triangle is a geometric optical illusion paradox as it is an impossible 3D object that cannot exist physically. Scientist Lionel Penrose popularized it in the 1950s, and similar versions existed earlier, such as the Reutersvard triangle illusion.
One of the well-known impossible objects, it features prominently in the works of artist MC Escher, like “Relativity” and “Belvedere.”
The Penrose Triangle sculpture in East Perth, Australia, showcases its shape from different perspectives. Photo credit: Bjørn Christian Tørrissen/Wikipedia
Motion-induced blindness
Observing the green dot in the center animation can make the stationary yellow dot appear to vanish. Animation: Mlechowicz/Wikipedia
The Bonnet illusion, known as “motion-induced blindness,” is a recently discovered optical illusion. A moving pattern rotates around a flashing green dot in the center of the screen, causing yellow dots within the pattern to disappear and reappear at random intervals if stared at for about 10 seconds.
The reasons behind this illusion are complex, but the lack of focus while viewing a moving image plays a significant role.
Necker Cube
The Necker Cube Illusion: Multiple possible interpretations. Photo credit: Getty Images
The Necker Cube is a shape with multiple perspectives, known as “multistable,” rather than an illusion itself. It lacks visual clues about its orientation, allowing for various interpretations by the brain.
Most individuals perceive the bottom left face of the cube as the front, likely due to our inclination to view things from above straight on, leading to this preferred interpretation.
Similar to Rubin’s Vase Illusion, where a single image can appear as either two faces or a vase, the Necker Cube demonstrates multistability.
An example of a Rubin vase. Photo courtesy of Getty Images
Sparkling grid illusion
The shimmering grid illusion. Dark dots appear and disappear where the grey lines intersect. Photo credit: Tó campos1/Wikipedia
The shimmering grid illusion challenges your brain by making black dots appear on a grid where white circles intersect, only to quickly disappear. This effect, known as the Hermann grid illusion, is a more recent version of a discovery made by Rudimar Hermann in 1870.
Peripheral drift illusion
Peripheral drift illusion – Colorful magenta dots grow larger and drift outwards as you move your eyes from one dot to another. Photo courtesy of Getty Images
The peripheral drift illusion, seen most clearly in circular designs, was described in 1999 by Jocelyn Forbert and Andrew Herbert. They found that the effect intensifies when the eyes are in motion or blinking.
Forbert and Herbert suggest that a combination of factors, including eye movements, light intensity differences, and depth perception, contribute to this illusion.
The motion illusion of spinning snakes created by Akiyoshi Kitaoka. Photo credit: Trent Steele/Wikipedia
Rabbit and duck illusion
The oldest known example of the rabbit-duck illusion (1892). Photo by Fliegende Blätter/Wikipedia
The rabbit and duck illusion is a type of ambiguous drawing where two objects can be seen, known as a “figure-ground configuration.” Originally published in a German humor magazine, this illusion had the caption “Which animals are most similar? A rabbit and a duck.”
Our brain’s perception is influenced by various factors, including creativity, leading to different interpretations. Another example of this phenomenon is the classic painting of two faces that can also be seen as a vase.
Color constancy
The Roman Originals dress demonstrates how humans perceive color differently. Photo by PA/Alamy
In 2015, a viral debate arose over the colors of a dress in a Cheshire store – some saw it as black and blue, while others as white and gold.
The differences in color perception can be attributed to the brain’s response to different colors under varying lighting conditions, as proposed by neuroscientists Bevil Conway and Jay Knights. Your perception of the dress’s color may vary based on whether you believe the image was taken in natural or artificial light.
Despite the dress manufacturer confirming it as black and blue, the white and gold interpretations made it a well-known example of human color vision discrepancies.
Ponzo illusion
In the Ponzo illusion, both blue horizontal lines are the same length. This illusion shows how the human mind judges the size of an object based on its background. Photo courtesy of Getty Images
The Ponzo illusion is a geometric optical illusion named after Italian psychologist Mario Ponzo, though he did not claim its discovery.
There are several explanations for why the top line appears longer than the bottom one, including the brain perceiving the top line as further away due to converging lines towards a vanishing point.
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