• Michael McMahon
    “Objects at a distance appear smaller because the visual angle they subtend becomes more acute with distance. The visual angle may be thought of as a triangle with the apex at the eye, and the distant object as its base.

    The apparent height of an object is directly proportional to its actual height and inversely proportional to its distance from the eye. Apparent Height = Actual Height / Distance. So to find the actual height of a distant object, multiply its apparent height by its distance. Conversely, you can divide the known actual height of a distant object by its measured apparent height to arrive at the distance.

    There is another geometrical distance relationship called the Inverse Square Law. This applies to all qualities projected by a distant object, including light bouncing off of its surface. Application of this law explains why a distant object may appear fainter than a near object.”
    - physics stackexchange

    That piece explains three distinct ways in which to infer distance by the phenomenon of perspective.

    “Point sources of gravitational force, electric field, light, sound or radiation obey the inverse square law.”

    A small object placed right beside your eye will appear to decrease significantly in apparent size when its moved to an arm’s length away. It might be half of its original size. If you were to look at a distant house on your street and took a step back from it then the house will only look marginally smaller with respect to its apparent size. Perhaps its still 95% of its previous size. However both the arm length and stride length back are almost the same length in the examples above even though the proportional change in size due to perspective is very different. Therefore the rate at which objects get smaller due to perspective is decelerating in its overall effect as the distance from you increases. This is related to the inverse square law. So the size of the various objects in your peripheral vision around your main object of focus can also provide clues as to how far away it is.
  • Michael McMahon
    We often think of perspective as being epiphenomenal because it obviously has no effect on physical objects. Changing your sightline relative to a moving object won’t make it veer off course. Clearly the changing size of distant objects won’t result in them experiencing any strain or deformation forces. The mass and density of objects remain constant irrespective of your conscious location. That said, perspective is still a major depth cue. The change of size affects the area and volume disproportionately through the square cube law. Of course it’s not that objects are orbiting around you but visually speaking you are essentially the centre of your own subjective perception. Light travels in straight lines from the top and bottom of the object to your eye. But we’ve no way of seeing the absolute size of the object seeing as we can only see it’s subsequent apparent size due to perspective. So the way that light gets translated into colour qualia might be indirect. Motion parallax seems to exploit this mismatch between apparent and absolute size. An identical eye movement from left to right will correspond to a larger visual displacement the further out into the horizon you can see. So if your head is directed downwards the eye movement merely equates to a few meters of the ground below you. If you look out in front of you from a high vantage point then this same eye angle across will cause a change of perhaps a kilometre.

    “Q: Can you explain the "square-cube" law in easy to understand terms?

    A: It’s not that hard to get. The square-cubed law is about the relationship between volume and area.

    Let’s take a water tank that holds 1 cubic metre of water. If you double every side of it, how much more water can it hold? And how much more material will you need to build one?...

    To build the first tank, you need 6 sides of 1 square metre, so 6 2 of stainless steel. To build the second tank, you need 6 sides of 2x2 m of stainless steel, or 6 sides of 4m2=24m2 of stainless steel, four times as much.

    So if you double the size in length, the surface area is double-squared, while the volume is double-cubed. Okay?

    And this has all kinds of consequences in real life. Say that you are an airplane manufacturer and you have a very successful airplane. But now you need to scale up. To remain competitive, you need to offer a plane that can carry eight times as many passengers.

    Oh, simple, you say. Just take the old plane and double every measurement. We can probably save tons of money because we will only need four times as much material on the hull. Right?

    Wrong. You see, while carrying capacity (in terms of fuel, passengers, kilograms, whatever) is determined by volume, the lift of the wing is determined by area. So if you double every measurement, you will have 8 times as much aircraft, passengers, fuel, cargo etc, but you will only have 4 times as much lift. And that means that your scaled-up plane will not be able to get off the ground – it will only have half of the lift per kg airplane than your original one.

    There are lots of other examples, from sailing ships (sail area is squared, cargo volume is cubed) to rocket engines (heat transfer in rocket engines depend on the area of the nozzles, not on the volume of fuel).”
  • Michael McMahon
    Other people have a different perspective than you; both metaphorically and literally. If someone looks at a scene and then moves away so that I can look from the exact same position, will we have both experienced the same perspective and depth perception from that vantage point? Will there be any slight geometrical differences? My sense of perspective will obviously conflict with another person’s view of perspective when we’re at different locations. If an object is closer to you than it is to me then you’ll perceive it as being bigger. So if I’m at the centre of my reality that doesn’t make me the visual centre of anyone else’s reality; we each have a unique locus of perspective.

    The image we see can represent a far greater area than the surface area of our eye. The scale of the background could be 1000s of times the size of our eyes. However we could still interpret the external image as being the same size as the eye. Consequently everything you see, from the floor below to the sky above, would be miniaturised and only a few centimetres long in total image height. The image would be almost entirely parallel to your eyes as you look straight ahead. Your perception of the ground would counterintuitively be at the same height level as the lower half of the eye. Perhaps a shortcut to think of this idea would be that the image we see exists inside of the eye rather than behind the eye in the brain or in front of the eye in external reality. An analogy for it would be like the visual image we see with its colour qualia is almost directly inside the vitreous humour itself. Invisible external light needs to first enter the eye to become visible while the brain subsequently reinterprets and resizes the image even though the image itself is right inside the middle of your own eye. We interpret light as being external because we cannot sense the fact that it has been refracted as it enters your eye. For example in the case of virtual images we view light as having travelled in a straight line even though it might have been redirected or reflected several times before it reached your retina.

    Definition: “The vitreous humour (also known simply as the vitreous) is a clear, colourless fluid that fills the space between the lens and the retina of your eye.”
  • Michael McMahon
    “Past research in experimental psychology and human physiology showed that perceiving the vertical and the “up” direction is based on multimodal integration of vestibular, somatosensory, and visual signals. Vestibular receptors located in the inner ear are directly sensitive to linear accelerations, and the vestibular system has been shown to play a crucial role in sensing the vertical... Another reference for the perception of the vertical and “up” direction is a body-centered reference based on somatosensory information emanating from the receptors distributed in the muscles, joints, skin, and viscera...
    Although most research on internal models of gravity has focused on the perception of visual stimuli in motion, it is very likely that representation of the vertical and “up” direction may modulate the perception of static visual stimuli as well...
    Our data show that pictures of a human body that is tilted in the direction opposite to physical gravity (“up”) are judged as more stable than pictures of a body that is tilted in the direction of physical gravity (“down”)...
    Collectively, the present data point to the highly adaptive role of the representation of the vertical and “up” direction and that humans constantly update this representation on the basis of multisensory cues, not only to maintain balance for standing upright or achieving acrobatic feats... but also for accurate visual perception.”

    It would look very weird if we didn’t perceive the ground as below us. It’d be like everyone was abseiling as they walked vertically up and down the footpath. It would seem as if gravity was acting horizontally on our physical body if we were at the equator. But that’s not how we perceive gravity and it’s like wherever on earth we look out towards the horizon is the top of the earth. Everyone almost perceives themselves to be at the north pole in the way that we can’t directly see the curvature of our planet on the ground in front of us. Location and space is relative that way so what I perceive as up in Ireland will be inverted in Australia. I’m not sure how exactly it is that our physical sense of balance can realign our perception of completely massless light given that light and gravity don’t seem to interact too much. Is the image rotated a bit in our brain?
  • Michael McMahon
    Light travels so fast that it’s unaffected by the curvature of Earth. It’s only under certain circumstances of massive stars that there’s any gravitational lensing. We’ll feel the effects of gravity on solid objects when we touch them. But our sensation of colour is unrelated to mass.

    “A gravitational lens can occur when a huge amount of matter, like a cluster of galaxies, creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight. The effect is like looking through a giant magnifying glass.”
  • Michael McMahon
    It’s quite easy to distinguish a flat 2D screen from it’s surroundings as it’s small and lacks resolution. But our retina has a much higher resolution than a TV screen. So even if the retina conveyed a 2D version of a 3D world we’d really still perceive it as 3D. The plank scale of our physical world is a lot more miniscule than an electronic pixel:

    “The proton is about 100 million trillion times larger than the Planck length...
    The Planck scale was invented as a set of universal units, so it was a shock when those limits also turned out to be the limits where the known laws of physics applied. For example, a distance smaller than the Planck length just doesn’t make sense—the physics breaks down.”
    -symmetry magazine

    “Pixels are the individual points of light that make up a digital picture. For example, an 8K TV has 33, 177, 600 pixels. To note, the term 8K refers to the number of pixels (about 8000) displayed horizontally per line.
    However, in human vision, eyes do not contain pixels. The closest comparison would be the rods and cones in your eyes that help you see. What’s more, what you resolve is the picture you are able to put together with your eyes and brain, not what necessarily exists in reality.
    Since the human eye doesn’t see in pixels at all, it’s pretty hard to compare them to a digital display.
    But curious minds want to know, if you could compare the two, how many pixels would the human eye likely have? It turns out, someone smart used some pretty complex math and (assuming 20/20 vision) got to 576 megapixels. 576 megapixels is roughly 576,000,000 individual pixels, so at first glance, it would seem that we could see way more than an 8K TV has to offer. But it’s not that simple. For instance, we see in 576 megapixel definition when our eyes are moving, but a single glance would only be about 5-15 megapixels.
    What’s more, your eyes naturally have a lot of flaws that a camera or digital screen don’t. For example, you have a built-in blind spot where your optic nerve meets up with your retina. You might also have a refractive error like nearsightedness or farsightedness. You might have also been born with (seemingly) super-powered eyes, like tetrachromats: people with four cone cells in their eyes instead of three. This means they can see many more colour varieties and therefore, when looking at a TV, could potentially distinguish much more than the average person...
    So if you’re wondering if your potentially extreme high-definition 576 megapixel eyes can see more than an 8K TV has to offer, consider this experiment: think of when you are at the beach. If you look down at the sand closest to you, you can easily count the individual grains, right? But the farther you look, the more difficult or impossible it becomes. That’s because distance plays a huge role in our resolution.”

    Perhaps we could eventually use a binoculars or a telescope to discern distant areas on a high-resolution TV screen!

    “Steve Jobs introduced the Retina display like this: "There's a magic number right around 300 pixels per inch, that when you hold something around to 10 to 12 inches away from your eyes, is the limit of the human retina to differentiate the pixels." In other words, the individual points of light would, theoretically vanish, creating a seamless image.
    But Raymond Soneira, president of DisplayMate Technologies and a frequent critic of screen-makers' marketing claims, calls that "marketing puffery." He says that your eye’s resolution isn't counted in pixels. Instead, your eye is limited by its angular resolution. "The angular resolution of the eye is 0.6 arc minutes per pixel,” he wrote in an e-mail to tech publications in 2010. "So, if you hold an iPhone at the typical 12 inches from your eyes, that works out to 477 pixels per inch." The bottom line: "The iPhone has significantly lower resolution than the [eye's] retina. It actually needs a resolution significantly higher than the retina in order to deliver an image that appears perfect to the retina."
    Now, it's worth noting that his analysis wasn't universally accepted. Phil Plait, who spent years calibrating the Hubble Space Telescope's optics, wrote that Soneira's numbers hold true only for people with perfect vision. If you have average eyesight, Jobs's claims are fine.”
    - scientificamerican: Why Hi-Res Isn’t Always Better
  • Michael McMahon
    “In terms of length, the average brain is around 15 centimeters long.”

    If the world were like a projection in our brain where our eyes are somehow in front of what we see rather than behind it, with the visual screen extending backwards into the brain, then the third dimension of depth would have to be abbreviated to a maximum length of that of the brain itself. So in that scenario the depth axis would be minimised and an apparent metre of visual light qualia would be a lot less than the real tactile metre it corresponds to.
  • Michael McMahon
    how can one explain the astonishing degree of agreement between you and I and Aunty Millie and Fred over there, if there is no 'reality' that is somehow shared by us all?

    Two possibilities occur to me, neither of them very palatable. Perhaps me and Aunty Millie and Fred over there are your creations, you being all that there is. Or perhaps you and me and Auntie Millie and Fred over there all partake in some 'overmind' that sets us up to think much the same thing. Solipsism or panpsychism.

    Even if we can’t directly observe the physical actions of someone’s consciousness on their materialistic neuronal brain, we can always discern the after-effects of their mental processes through their apparent free will and ability to spontaneously adapt or improvise to you and their surroundings. So if you can infer that you yourself have free will and that other people can change based on your input, then logically they must also have this same capacity for free will and consciousness.
  • Michael McMahon
    We can wonder if colour is spatially real when it applies to material objects. It’s not like a more vivid shade of blue alters the density of that substance. But can this question of unrealness be extended to the temporal dimension? If colour wasn’t real in terms of time then it’d be as though the colours were eternal and timeless. What are the options? Colour might have arisen just like matter in the Big Bang. In that case the colour of a green forest would of always been there even if no one was ever there to observe it. Or else in a biological sense the qualia of colour might derive from primordial human evolution where our perception of red is based on ancient memories and associations that have trickled down by way of our genes. Alternatively we could perhaps view the sensations of colour as originating from the deepest parts of our own unconscious mind. This would be where the brain superimposes the feeling of touch and balance on top of an initial, fundamental layer of these inexplicable colours (rather than it being the other way round where colour would just be secondary or epiphenomenal). So in that scenario colour would seem to be the primary reality. To be honest I don’t exactly know.
  • Michael McMahon
    Dualism might appear to be more usually associated with free will. But what would happen if we instead combined dualism with determinism? Then our visual reality and our tactile sense could exist in parallel without directly interacting. So long as they both have the same initial conditions and that our volition during the day is in some way deterministic, then hypothetically light and matter doesn’t really have to interact.
  • noAxioms
    Sorry for long delay. I guess I sometimes go for quite some time without visiting the site.

    What would the phrases, "living under a rock", or "living in a bubble" mean for an anti-realist?Harry Hindu
    Not claiming to be one, so I'll let them answer that. I make no claims of the unreality of anything.

    Are there other minds, or other bodies?
    I favor a relational stance (Rovelli), so I'd say that other people exist to me, and I to them. We measure each other, so each exists relative to the other. This has nothing at all to do with people, mind, consciousness or epistemology. I exist relative to my keyboard because it measures me (I have a causal effect on it). I do not exist relative to the current state of Betelgeuse since that 'system' has not measured me. I suppose I exist to some future state of Betelgeuse, but not necessarily any future state.

    Per Rovelli, I do not exist relative to myself, which makes sense, and is essentially why Schrodinger's cat, perfectly capable of sensing its various parts, cannot collapse its own wave function relative to the outside of the closed box.

    I favor such a view because it seems to avoid the general paradox of realism which is its inability to explain the reality of whatever the realist considers to be real.

    so anti-realism defeats itself by rejecting it's own existence as a belief? A non-existent nihilist? :lol:Harry Hindu
    That's their claim it seems. They give meaning to the property of existence, but claim nothing has that property. I see little point in positing a property that nothing has, but other than that (and your wonderfully worded argument from incredulity aside), I see no contradiction in the stance, even if it isn't my stance.

    What do you mean by, "'existence of an objective reality" to say that it is meaningless?
    No relation specified, so the statement is meaningless in my view. For something to exist objectively, it would have to exist in relation to, what?... something more encompassing than the universe at least. The proverbial view from nowhere it seems. Is a member of the set of all that exists, except the set cannot list itself for the reason given above.
  • Michael McMahon
    What would happen if we viewed the brain as purely physical; as though it’s simply where all of the sentient memory is being stored? Then your consciousness would literally “be” the entire world that you see with it’s myriad colours and diverse qualia. It would be like perspective were a real physical force in your subjective sense of photon vision. Although it’d clearly have no effect at all on the actual matter of objects or indeed the living minds of others.
  • Manuel

    Well, this may be a roughly Neo-Kantian or Rationalistic-Idealist understanding, but I believe it to be accurate nevertheless. The idea would be that what we see and experience is an interplay between whatever is "out there" with some innate capacities to structure, shape and imbue experience with meaning.

    So the "external world", as it is "in itself" is not something we can know. This does not imply at all that all the ordinary things we take for granted "trees", "rivers", etc. are illusions at all, no, they are the most evident aspect of our conscious experience, but these things aren't mind-independent.

    Some argue that modern science may tell us about "things in themselves", others are more skeptical and think that science only tells us about the structural aspects of reality, and not there inner nature. I tend to side with this latter view.

    But I should add something which I think is important, which Chomsky has pointed out. The word "real" is honorific. So when we say "this is the real truth" or "this is the real deal", we are not saying that there are two kinds of truth or deals, we are only emphasizing our statements. In this sense the word "real" can often lead to confusion, though not always.
  • j0e
    The word "real" is honorific. So when we say "this is the real truth" or "this is the real deal", we are not saying that there are two kinds of truth or deals, we are only emphasizing our statements. In this sense the word "real" can often lead to confusion, though not always.Manuel


    That's one important use of 'real.' I'd go farther and say that it has many uses. 'Are you for real?" 'This almond butter is really good.' 'That's unreal, bro.' 'The real is that which resists.'
    'Is that gun real?' 'See you all later. It's been real.'

    IMO, we are great at using the word in ordinary life. Philosophers tie themselves in knots when they try to pin down an official or absolute meaning, which is like catching the wind in a net.
  • Manuel
    IMO, we are great at using the word in ordinary life. Philosophers tie themselves in knots when they try to pin down an official or absolute meaning, which is like catching the wind in a net.j0e

    Absolutely. It's hard not to confuse the words we use with the things we are talking about.
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