LightSource

lightsource

At HackerNoon, we believe transparency with the reader is the key to building trust between writer and reader. To give readers as much transparency as possible, we wanted to create quick and easy ways to tell the reader information they might want to know about a story before reading it. This could be something as simple as telling the reader if the story is a news piece or an opinion piece. On the other hand, there are more complicated things we might want to communicate to the reader, such as whether or not the writer has a vested interest in the companies they’re writing about, or if they used AI to write the piece. To accomplish these goals, we created Emoji Credibility Indicators! Now open-sourced on Figma Community & GitHub. Learn more about Emoji Credibility Indicators here. Designing Emoji Credibility Indicators Now, let’s dive into the process of designing Emoji Credibility Indicators. The initial design brief by David and our Editorial Team included 22 Emoji Credibility Indicators (related read, Every Emoji Credibility Indicator on HackerNoon Explained) divided into two categories: context/disclaimers and content types. In addition to their description, each credibility indicator was assigned an emoji for design inspiration. From here on in, it was on us (Me & Kien) to run wild with our imagination and bring these emoji indicators to life. Following HackerNoon’s design language, we chose the Pixel Art Style. After exploring several options for grid sizes, we opted for a 24px grid for pixelation since it retained the desired level of detail. As for the software of choice, I was a bit biased going for Adobe Illustrator since we get plenty of options when it comes to exporting to different file types + my familiarity with the grid tool (Adobe Photoshop, Aseprite, and Corel Draw are some good alternatives). Our pixel art design process consists of 5 steps, starting from basic shapes, drawing details, creating depth, adding strokes, and then merging shapes & exporting to different file types. Let’s take a deeper dive into these steps taking the Comedy/Satire emoji credibility indicator for example. Starting with Basic Shapes Whenever we do Pixel-Art/8-bit Designs, we start with a basic shape that resonates with the idea we have in mind. Being an ellipse, in the case of the Comedy/Satire emoji indicator (which was inspired by the ‘😂’ emoji). Drawing Details Then we head on to adding more details to the shape we just drew (like facial features in this case). Creating Depth: Highlights & Shadows To make it more realistic and less flat, we add highlights and shadows to the face. In this case, the light source was assumed to be up front and center which makes the shadows move to the edges and the highlights to the center. Pro Tip: Always try to use three shades of a color. One for the base, the lighter one for highlights, and the darker one for shadows. Adding Stroke To make it more defined, we added a stroke to wrap things up. Merging Shapes and Exporting To make them more usable, we merged the shapes and exported them as both PNGs and SVGs. Then, we repeated this whole process 21 more times and ended up with the Emoji Credibility Indicators we have on HackerNoon today. The Final Product: An Open Sourced Pixelated Emoji Pack In conclusion, the Emoji Credibility Indicators are yet another step towards enhancing online communication between our readers and writers. These pixelated emojis not only serve as credibility indicators adding context to content but have impacted users’ trust & engagement with content. They serve as an example of how thoughtful design can convey complex concepts in a simple yet intuitive manner. Join us on this quest of emojifying context, and try out The Emoji Credibility Indicators by HackerNoon. Now available on Figma Community and GitHub Stay Creative, Stay Iconic. At HackerNoon, we believe transparency with the reader is the key to building trust between writer and reader. To give readers as much transparency as possible, we wanted to create quick and easy ways to tell the reader information they might want to know about a story before reading it. This could be something as simple as telling the reader if the story is a news piece or an opinion piece. On the other hand, there are more complicated things we might want to communicate to the reader, such as whether or not the writer has a vested interest in the companies they’re writing about, or if they used AI to write the piece. To accomplish these goals, we created Emoji Credibility Indicators! Now open-sourced on Figma Community & GitHub . Figma Community GitHub Learn more about Emoji Credibility Indicators here. Learn more about Emoji Credibility Indicators here . here here Designing Emoji Credibility Indicators Now, let’s dive into the process of designing Emoji Credibility Indicators. The initial design brief by David and our Editorial Team included 22 Emoji Credibility Indicators (related read, Every Emoji Credibility Indicator on HackerNoon Explained ) divided into two categories: context/disclaimers and content types. In addition to their description, each credibility indicator was assigned an emoji for design inspiration. David Every Emoji Credibility Indicator on HackerNoon Explained From here on in, it was on us (Me & Kien ) to run wild with our imagination and bring these emoji indicators to life. Following HackerNoon’s design language, we chose the Pixel Art Style. After exploring several options for grid sizes, we opted for a 24px grid for pixelation since it retained the desired level of detail. As for the software of choice, I was a bit biased going for Adobe Illustrator since we get plenty of options when it comes to exporting to different file types + my familiarity with the grid tool ( Adobe Photoshop , Aseprite , and Corel Draw are some good alternatives). Kien Adobe Photoshop Aseprite Our pixel art design process consists of 5 steps, starting from basic shapes, drawing details, creating depth, adding strokes, and then merging shapes & exporting to different file types. Let’s take a deeper dive into these steps taking the Comedy/Satire emoji credibility indicator for example. Starting with Basic Shapes Whenever we do Pixel-Art/8-bit Designs, we start with a basic shape that resonates with the idea we have in mind. Being an ellipse, in the case of the Comedy/Satire emoji indicator (which was inspired by the ‘😂’ emoji). Drawing Details Then we head on to adding more details to the shape we just drew (like facial features in this case). Creating Depth: Highlights & Shadows To make it more realistic and less flat, we add highlights and shadows to the face. In this case, the light source was assumed to be up front and center which makes the shadows move to the edges and the highlights to the center. Pro Tip: Always try to use three shades of a color. One for the base, the lighter one for highlights, and the darker one for shadows. Pro Tip: Always try to use three shades of a color. One for the base, the lighter one for highlights, and the darker one for shadows. Adding Stroke To make it more defined, we added a stroke to wrap things up. Merging Shapes and Exporting To make them more usable, we merged the shapes and exported them as both PNGs and SVGs. Then, we repeated this whole process 21 more times and ended up with the Emoji Credibility Indicators we have on HackerNoon today. Emoji Credibility Indicators The Final Product: An Open Sourced Pixelated Emoji Pack An Open Sourced Pixelated Emoji Pack In conclusion, the Emoji Credibility Indicators are yet another step towards enhancing online communication between our readers and writers. These pixelated emojis not only serve as credibility indicators adding context to content but have impacted users’ trust & engagement with content. They serve as an example of how thoughtful design can convey complex concepts in a simple yet intuitive manner. Emoji Credibility Indicators Join us on this quest of emojifying context, and try out The Emoji Credibility Indicators by HackerNoon. Now available on Figma Community and GitHub Now available on Figma Community and GitHub Figma Community GitHub Stay Creative, Stay Iconic. Stay Creative, Stay Iconic.

Emojifying Context: Designing HackerNoon's Emoji Credibility Indicators

ইমোজিফাইং কনটেক্সট: হ্যাকারনুনের ইমোজি বিশ্বাসযোগ্যতা সূচক ডিজাইন করা

Emojifying-Kontext: Entwicklung der Emoji-Glaubwürdigkeitsindikatoren von HackerNoon

Contexto emojificante: diseño de indicadores de credibilidad emoji de HackerNoon

Contexte émoticône : conception des indicateurs de crédibilité Emoji de HackerNoon

इमोजी संदर्भ: हैकरनून के इमोजी विश्वसनीयता संकेतकों का डिज़ाइन

絵文字によるコンテキストの表現: HackerNoon の絵文字信頼性指標の設計

이모티콘 컨텍스트: HackerNoon의 이모티콘 신뢰성 지표 설계

Contexto Emojifying: Projetando Indicadores de Credibilidade Emoji do HackerNoon

Контекст эмодзи: разработка индикаторов достоверности эмодзи от HackerNoon

Emojileştirme Bağlamı: HackerNoon'un Emoji Güvenilirlik Göstergelerini Tasarlama

Bối cảnh biểu tượng cảm xúc: Thiết kế các chỉ số đáng tin cậy về biểu tượng cảm xúc của HackerNoon

表情符号化语境：设计 HackerNoon 的表情符号可信度指标

Startups of The Year 2023 Winners: North America 

When I was building the website, I accidentally stumbled on a way to make Neon buttons look good. Magical Dev School https://youtu.be/uiI7eEUFbc4?embedable=true There are three important elements: 1. A little bit of glow around the text 2. A larger glow around the button 3. A nice zoom effect Making the text glow The trick here is to use `drop-shadow` instead of `text-shadow` to create the glow effect. `drop-shadow` works better because it creates a softer and more enveloping blur - very much like how a soft light source would fall into its surroundings. `text-shadow` is too harsh. We only want to use `drop-shadow` on the text, so we need to change the markup a little bit to include an extra span element. html 
<button>
  <span class="text">Text goes here </span>
</button> And we can include the `drop-shadow` like this: css
.text {
  filter: drop-shadow(0 0 1px currentcolor);
} Making the larger glow around the button We can make a larger glow around the button with `drop-shadow` and `box-shadow`. In this case, I prefer `box-shadow` over `drop-shadow` because I can control the spread. This lets me cast a harsher shadow that accentuates the border. The code for `drop-shadow` is simpler because you can attach it directly to the button. css
button {
  filter: drop-shadow(0 0 1rem var(--purple-300));
} The code for `box-shadow` is slightly harder because you'll have to use a pseudo-element to make smooth animation. That's because transitioning `box-shadow` . creates jank css
button {
  position: relative;
  z-index: 1;
  /* ... */
}

button:after {
  content: '';
  position: absolute;
  z-index: -1;
  inset: 0;
  border-radius: inherit;
  opacity: 0.6;
  box-shadow: 0 0 1em 0.5em var(--purple-300);
} A nice zoom effect The third and final piece is to jell everything together with a little bit of animations. https://youtu.be/L-89PGVLxLo?embedable=true Here, I opted to: - Change the `background-color` - Change the `color` - Make the button bigger (as if it's floating outwards) - And make the background glow a little bit stronger by changing the `opacity` Codepen Link Here's Codepen for you to play around with this neon button. https://codepen.io/zellwk/pen/poQMqvW?embedable=true By the way, this article is originally written on my blog. Feel free to visit that if you want to have these articles delivered to your email first-hand whenever they're released! 🙂. Also published . here

A Quick CSS Guide: Crafting Neon Buttons with Glow Effects & Animations

Creating Your Own 3D Shooter Using the React and Three.js Stack — Part 1

প্রতিক্রিয়া এবং Three.js স্ট্যাক ব্যবহার করে আপনার নিজস্ব 3D শ্যুটার তৈরি করা — পার্ট 1

Erstellen Sie Ihren eigenen 3D-Shooter mit dem React- und Three.js-Stack – Teil 1

Creando tu propio shooter 3D usando React y Three.js Stack - Parte 1

Créer votre propre jeu de tir 3D à l'aide de la pile React et Three.js - Partie 1

रिएक्ट और थ्री.जेएस स्टैक का उपयोग करके अपना खुद का 3डी शूटर बनाना - भाग 1

React と Three.js スタックを使用して独自の 3D シューターを作成する — パート 1

React와 Three.js 스택을 사용하여 나만의 3D 슈터 만들기 - 1부

Criando seu próprio jogo de tiro 3D usando React e Three.js Stack - Parte 1

Создание собственного 3D-шутера с использованием стека React и Three.js — Часть 1

React ve Three.js Stack'ı Kullanarak Kendi 3D Shooter'ınızı Oluşturma - Bölüm 1

Tạo game bắn súng 3D của riêng bạn bằng cách sử dụng ngăn xếp React và Three.js - Phần 1

使用 React 和 Three.js 堆栈创建您自己的 3D 射击游戏 — 第 1 部分

Lasers by Hal Hellman, is part of the HackerNoon Books Series. You can jump to any chapter in this book . LIGHT AND THE ATOM here LIGHT AND THE ATOM Since light waves have such high frequencies, a different mode of generation comes into play. We can no longer count on the controlled movement of free electrons atoms and molecules. Rather, light and all the radiations in the higher frequencies are generated by the movement of electrons atoms and molecules. outside inside Let us review momentarily the modern, albeit highly simplified, conception of an atom. Remember that no one has yet seen one. We describe the atom on the basis of how it acts, as well as how it reacts to things scientists do to it. For the present purpose, the best model we have of the atom is that of a miniature solar system, with a nucleus or heavy part at the center and a cloud of electrons dashing around the nucleus in fixed orbits. The term “fixed orbits” is used advisedly. Our planet moves in a certain orbit around the sun. If we attached a large enough rocket to the earth we theoretically move it closer to or farther away from the sun. In the atom, we have learned, this cannot be done. An electron can only exist in one of a certain number of fixed orbits; different kinds of atoms have different numbers of orbits. could We might think in terms of an elevator that can only stop at the various floors of an apartment building. Each upper floor is like an orbit of the electron. But you get nothing for nothing in the world of physics, and just as it takes energy to raise an elevator to a higher floor, it takes energy to move an electron to an outer orbit. Hence the atom is said to be raised to higher levels when an electron is nudged to an outer orbit. The energy input can be of many different kinds. Examples are heat, pressure, electrical current, chemical energy, and various forms of electromagnetic radiation. If too much energy is put into the elevator it goes flying out the roof. If too much energy is put into the atom, one or more of its electrons will go flying out of the atom. This is called , and the atom, now minus one of its negative electrons and therefore positively charged, is called a positive . energy ionization ion But if the amount of energy is put into the atom, one of its electrons will merely be raised to a higher energy level. Shown in , for instance, are the ground state (Circle No. 1) and two possible higher energy levels. As you can see there are three possible transitions. right Figure 9 Figure 9 Schematic representation of the electron orbits and energy levels of an atom. Each circle represents a separate possible orbit and each arrow a possible energy level difference. The higher energy levels are abnormal, or excited, states, however, and the electron will shortly fall back to its normal (ground state) orbit (assuming some other electron has not fallen into it first). In order for the electron to do this (go back to its normal orbit), it must give off the energy it has acquired. This it does in the form of electromagnetic radiation. The energy difference between the two levels will determine what kind of radiation is emitted, for there is a direct correlation between energy and frequency. If the energy difference between the two levels is such that the frequency of emitted radiation is roughly between 10¹⁴ and 10¹⁵ cycles per second, we see the radiation as light. When more energy is added, the radiation emerges as ultraviolet or X rays. In other words the higher the energy difference, the higher the frequency, and vice versa. Thus it is that cosmic rays, with the highest frequencies known to man, can pass right through us as if we weren’t there. This simple picture of energy levels and associated frequencies doesn’t quite hold for ordinary white light, however. Such light is generally produced by a process called incandescence, which results from the heating of a material until it glows. True, the atoms of the incandescent material are being raised to higher energy levels by chemical energy (as in fire), electricity (light bulb), or nuclear energy (the sun). In a hot solid, however, the explanation becomes more complicated. Many different electronic configurations are possible and the differences in energy among the various levels (which can be many more than the three shown in ) vary only slightly from one another. The result is a wide band of radiation. Figure 9 Thus, while the incandescent electric bulb is a great advance over fire, it is still a very inefficient source of light. Because it depends upon incandescence, a considerable portion of the electrical input goes into the production of unwanted heat, for the bulb’s filament radiates in the infrared as well as the visible region. For providing illumination, the fluorescent tube is far more efficient than the incandescent lamp: a 40-watt fluorescent tube gives as much light as a 150-watt incandescent light. This is because its radiation is more controlled, operating more in accord with our description of electronic energy levels. Hence more of its output is in the desired visual region of the spectrum. In certain types of lighting, particular energy level changes may predominate, leading to the characteristic colors of neon tubes and vapor lamps. Although the resulting radiation bandwidth is narrow enough in these devices to appear as a definite color instead of the broad spectrum we know as white, it is still quite broad. In other words, the radiation is still frequency incoherent—and it is still spatially incoherent. To understand this, let us return for a moment to the group of radio antennas we showed in . All of them, you will recall, could be made to radiate in phase. In the production of light, however, each antenna is replaced by a single atom! Figure 8 This creates two problems. First, because the energy stored in the atom is quite small, it comes out not as a continuous wave but as a tiny packet of radiation—a . It has an effect more like the hack of an ax than the buzz of a power saw. photon Second, atoms are notoriously “individualistic”. When a batch of atoms in a material has been raised to higher energy levels there is no way to know in what order, or in what direction, they will release their energy. This kind of process is called , since each atom “makes up its own mind”. All we know is that within a certain period of time—a short period, to be sure—a certain percentage of these higher energy atoms will release their photons. spontaneous emission Figure 10 Ordinary light is a jumble of frequencies, directions, and phases. What we have, then, is incoherent radiation—a jumble of frequencies (or colors), directions, and phases. Such light, symbolized in , works well enough in lighting up this page, but is almost worthless as a carrier of information (and in other ways, as we shall see shortly). About the best that can be done with it is to turn it on and off in a sort of visual Morse code, which is exactly what is done on the blinker communication systems sometimes used for ship-to-ship communication. Figure 10 In other words, ordinary light cannot be modulated as radio waves can. It is of interest to note, however, that ordinary white light be made coherent, to some extent, but at a very high cost in the intensity of the light. For example, we might first pass the light through a series of filters, each of which would subtract some portion of the spectrum, until only the desired wavelength came through. As can be seen in , only a small fraction of the original light would be left. can Figure 11 Figure 11 Obtaining coherent radiation the hard way. Filters and pinhole block all but a small amount of the original radiation. Incoherent Filters Coherent in time Pinhole Coherent in time and space We would then have monochromatic (one color) light, which is temporally coherent radiation, but it would still be spatially incoherent. In our diagram, we show three monochromatic waves. If we then passed this light through a tiny pinhole as shown, most of these few remaining waves would be blocked; the ones that got through would be pretty much in step. (In a similar manner, a true point source of light would produce spatially coherent radiation; but, as in the process described here, there wouldn’t be very much of it.) We have, finally, obtained coherent light. The important thing about the laser is that, by its very nature, it produces coherent light automatically. Now.... About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Hal Hellman (2021). Laser. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/65512/pg65512-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

LIGHT AND THE ATOM

ARTIFICIAL LIGHT IN WARFARE

Lighting of objects or of a scene can alone produce an illusion

Visual Illusions: Their Causes, Characteristics and Applications by Matthew Luckiesh is part of the HackerNoon Books Series. You can jump to any chapter in this book here . EQUIVOCAL FIGURES V. EQUIVOCAL FIGURES MANY figures apparently change in appearance owing to fluctuations in attention and in associations. A human profile in intaglio ( and ) may appear as a bas-relief. Crease a card in the middle to form an angle and hold it at an arm’s length. When viewed with one eye it can be made to appear open in one way or the other; that is, the angle may be made to appear pointing toward the observer or away from him. The more distant part of an object may be made to appear nearer than the remaining part. Plane diagrams may seem to be solids. Deception of this character is quite easy if the light-source and other extraneous factors are concealed from the observer. It is very interesting to study these fluctuating figures and to note the various extraneous data which lead us to judge correctly. Furthermore, it becomes obvious that often we see what we expect to see. For example, we more commonly encounter relief than intaglio; therefore, we are likely to think that we are looking at the former. Figs. 72 73 Proper consideration of the position of the dominant light-source and of the shadows will usually provide the data for a correct conclusion. However, habit and probability are factors whose influence is difficult to overcome. Our perception is strongly associated with accustomed ways of seeing objects and when the object is once suggested it grasps our mind completely in its stereotyped form. Stairs, glasses, rings, cubes, and intaglios are among the objects commonly used to illustrate this type of illusion. In connection with this type, it is well to realize how tenaciously we cling to our perception of the real shapes of objects. For example, a cube thrown into the air in such a manner that it presents many aspects toward us is throughout its course a cube. [Pg 65] Fig. 27.—Illustrating fluctuation of attention. The figures which exhibit these illusions are obviously those which are capable of two or more spatial relations. The double interpretation is more readily accomplished by monocular than by binocular vision. consists of identical patterns in black and white. By gazing upon this steadily it will appear to fluctuate in appearance from a white pattern upon a black background to a black pattern upon a white background. Sometimes fluctuation of attention apparently accounts for the change and, in fact, this can be tested by willfully altering the attention from a white pattern to a black one. Incidentally one investigator found that the maximum rate of fluctuation was approximately equal to the pulse rate, although no connection between the two was claimed. It has also been found that inversion is accompanied by a change in refraction of the eye. Fig. 27 [Pg 66] Fig. 28.—The grouping of the circles fluctuates. Another example is shown in . This may appear to be white circles upon a black background or a black mesh upon a white background. However, the more striking phenomenon is the change in the grouping of the circles as attention fluctuates. We may be conscious of hollow diamonds of circles, one inside the other, and then suddenly the pattern may change to groups of diamonds consisting of four circles each. Perhaps we may be momentarily conscious of individual circles; then the pattern may change to a hexagonal one, each “hexagon” consisting of seven circles—six surrounding a central one. The pattern also changes into parallel strings of circles, triangles, etc. Fig. 28 [Pg 67] Fig. 29.—Crossed lines which may be interpreted in two ways. The crossed lines in can be seen as right angles in perspective with two different spatial arrangements of one or both lines. In fact there is quite a tendency to see such crossed lines as right angles in perspective. The two groups on the right represent a simplified Zöllner’s illusion ( ). The reader may find it interesting to spend some time viewing these figures and in exercising his ability to fluctuate his attention. In fact, he must call upon his imagination in these cases. Sometimes the changes are rapid and easy to bring about. At other moments he will encounter an aggravating stubbornness. Occasionally there may appear a conflict of two appearances simultaneously in the same figure. The latter may be observed occasionally in . Eye-movements are brought forward by some to aid in explaining the changes. Fig. 29 Fig. 37 [Pg 68] Fig. 30 Fig. 30.—Reversible cubes. In a reversal of the aspect of the individual cubes or of their perspective is very apparent. At rare moments the effect of perspective may be completely vanquished and the figure be made to appear as a plane crossed by strings of white diamonds and zigzag black strips. Fig. 30 The illusion of the bent card or partially open book is seen in . The tetrahedron in may appear either as erect on its base or as leaning backward with its base seen from underneath. [Pg 69] Fig. 31 Fig. 32 Fig. 31.—The reversible “open book” (after Mach). Fig. 32.—A reversible tetrahedron. The series of rings in may be imagined to form a tube such as a sheet-metal pipe with its axis lying in either of two directions. Sometimes by closing one eye the two changes in this type of illusion are more readily brought about. It is also interesting to close and open each eye alternately, at the same time trying to note just where the attention is fixed. Fig. 33 The familiar staircase is represented in . It is likely to appear in its usual position and then suddenly to invert. It may aid in bringing about the reversal to insist that one end of a step is first nearer than the other and then farther away. By focusing the attention in this manner the fluctuation becomes an easy matter to obtain. Fig. 34 [Pg 70] 33.—Reversible perspective of a group of rings or of a tube. Fig. 34.—Schröder’s reversible staircase. In is a similar example. First one part will appear solid and the other an empty corner, then suddenly both are reversed. However, it is striking to note one half changes while the other remains unchanged, thus producing momentarily a rather peculiar figure consisting of two solids, for example, attached by necessarily warped surfaces. Fig. 35 [Pg 71] Fig. 35.—Thiéry’s figure. Perhaps the reader has often witnessed the striking illusion of some portraits which were made of subjects looking directly at the camera or painter. Regardless of the position of the observer the eyes of the portrait appear to be directed toward him. In fact, as the observer moves, the eyes in the picture follow him so relentlessly as to provoke even a feeling of uncanniness. This fact is accounted for by the absence of a third dimension, for a sculptured model of a head does not exhibit this feature. Perspective plays a part in some manner, but no attempt toward explanation will be made. In are two sketches of a face. One appears to be looking at the observer, but the other does not. If the reader will cover the lower parts of the two figures, leaving only the two pairs of eyes showing, both pairs will eventually appear to be looking at the observer. Perhaps the reader will be conscious of mental effort and the lapse of a few moments before the eyes on the left are made to appear to be looking directly at him. Although it is not claimed that this illusion is caused by the same conditions as those immediately preceding, it involves attention. At least, it is fluctuating in appearance and therefore is equivocal. It is interesting to note the influence of the other features (below the eyes). The perspective of these is a powerful influence in “directing” the eyes of the sketch. [Pg 72] Fig. 36 In the foregoing only definite illusions have been presented which are universally witnessed by normal persons. There are no hallucinatory phases in the conditions or causes. It is difficult to divide these with definiteness from certain illusions of depth as discussed in Chapter VII. The latter undoubtedly are sometimes entwined to some extent with hallucinatory phases; in fact, it is doubtful if they are not always hallucinations to some degree. Hallucinations are not of interest from the viewpoint of this book, but illusions of depth are treated because they are of interest. They are either hallucinations or are on the border-line between hallucinations and those illusions which are almost universally experienced by normal persons under similar conditions. The latter statement does not hold for illusions of depth in which objects may be seen alternately near and far, large and small, etc., although they are not necessarily pure hallucinations as distinguished from the types of illusions regarding which there is general perceptual agreement. [Pg 73] Larger Image Fig. 36.—Illustrating certain influences upon the apparent direction of vision. By covering all but the eyes the latter appear to be drawn alike in both sketches. In explanation of the illusory phenomena pertaining to such geometrical figures as are discussed in the foregoing paragraphs, chiefly two different kinds of hypotheses have been offered. They are respectively psychological and physiological, although there is more or less of a mixture of the two in most attempts toward explanation. The psychological hypotheses introduce such factors as attention, imagination, judgment, and will. Hering and also Helmholtz claim that the kind of inversion which occurs is largely a matter of chance or of volition. The latter holds that the perception of perspective figures is influenced by imagination or the images of memory. That is, if one form of the figure is vividly imagined the perception of it is imminent. Helmholtz has stated that, “Glancing at a figure we observe spontaneously one or the other form of perspective and usually the one that is associated in our memory with the greatest number of images.” The physiological hypotheses depend largely upon such factors as accommodation and eye-movement. Necker held to the former as the chief cause. He has stated that the part of the figure whose image lies near the fovea is estimated as nearer than those portions in the peripheral regions of the visual field. This hypothesis is open to serious objections. Wundt contends that the inversion is caused by changes in the points and lines of fixation. He says, “The image of the retina ought to have a determined position if a perspective illusion is to appear; but the form of this illusion is entirely dependent on motion and direction.” Some hypotheses interweave the known facts of the nervous system with psychological facts but some of these are examples of a common anomaly in theorization, for facts plus facts do not necessarily result in a correct theory. That is, two sets of facts interwoven do not necessarily yield an explanation which is correct. [Pg 75] About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Matthew Luckiesh (2011). Visual Illusions: Their Causes, Characteristics and Applications. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/36297/pg36297-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org , located at https://www.gutenberg.org/policy/license.html.

EQUIVOCAL FIGURES

From earliest times the beacon-fire has sent forth messages

Artificial Light: Its Influence Upon Civilization by Matthew Luckiesh is part of the HackerNoon Books Series. You can jump to any chapter in this book here . THE LIGHT OF THE FUTURE XI. THE LIGHT OF THE FUTURE In viewing the development of artificial light and its manifold effects upon the activities of mankind, it is natural to look into the future. Jules Verne possessed the advantage of being able to write into fiction what his riotous imagination dictated, and so much of what he pictured has come true that his success tempts one to do likewise in prophesying the future of lighting. Surely a forecast based alone upon the past achievements and the present indications will fall short of the actual realizations of the future! If the imagination is permitted to view the future without restrictions, many apparently far-fetched schemes may be devised. It may be possible to turn to nature's supply of daylight and to place some of it in storage for night use. One millionth part of daylight released as desired at night would illuminate sufficiently all of man's nocturnal activities. The fictionist need not heed the scientist's inquiry as to how this daylight would be bottled. Instead of giving time to such inquiries he would pass on to another scheme, whereby earth would be belted with optical devices so that day could never leave. When the sun was shining in China its light would be gathered on a large scale and sent eastward and westward in these great optical "pipe-lines" to the regions of darkness, thus banish ing night forever. The writer of fiction need not bother with a consideration of the economic situation which would demand such efforts. This line of conjecture is interesting, for it may suggest possibilities toward which the present trend of artificial lighting does not point; however, the author is constrained to treat the future of light-production on a somewhat more conservative basis. At the present time the light-source of chief interest in electric lighting is the incandescent filament lamp; but its luminous efficiency is limited, as has been shown in a previous chapter. When light is emitted by virtue of its temperature much invisible radiant energy accompanies the visible energy. The highest luminous efficiency attainable by pure temperature radiation will be reached when the temperature of a normal radiator reaches the vicinity of 10,000°F. to 11,000°F. The melting-points of metals are much lower than this. The tungsten filament in the most efficient lamps employing it is operating near its melting-point at the present time. Carbon is a most attractive element in respect to melting-point, for it melts at a temperature between 6000°F. and 7000°F. Even this is far below the most efficient temperature for the production of light by means of pure temperature radiation. There are possibilities of higher efficiency being obtained by operating arcs or filaments under pressure; however, it appears that highly efficient light of the future will result from a radical departure. Scientists are becoming more and more intimate with the structure of matter. They are learning secrets every year which apparently are leading to a fundamental knowledge of the subject. When these mysteries are solved, who can say that man will not be able to create elements to suit his needs, or at least to alter the properties of the elements already available? If he could so alter the mechanism of radiation that a hot metal would radiate no invisible energy, he would have made a tremendous stride even in the production of light by virtue of high temperature. This property of selective radiation is possessed by some elements to a slight degree, but if treatment could enhance this property, luminous efficiency would be greatly increased. Certainly the principle of selectivity is a byway of possibilities. A careful study of commonplace factors may result in a great step in light-production without the creation of new elements or compounds, just as such a procedure doubled the luminous efficiency of the tungsten filament when the gas-filled lamp appeared. There are a few elements still missing, according to the Periodic Law which has been so valuable in chemistry. When these turn up, they may be found to possess valuable properties for light-production; but this is a discouraging byway. It is natural to inquire whether or not any mode of light-production now in use has a limiting luminous efficiency approaching the ultimate limit which is imposed by the visibility of radiation. The eye is able to convert radiant energy of different wave-lengths into certain fixed proportions of light. For example, radiant energy of such a wave-length as to excite the sensation of yellow-green is the most efficient and one watt of this energy is capable of being converted by the visual apparatus into about 625 lumens of light. Is this efficiency of conversion of the visual apparatus everlastingly fixed? For the answer it is necessary to turn to the physiologist, and doubtless he would suggest the curbing of the imagination. But is it unthinkable that the visual processes will always be beyond the control of man? However, to turn again to the physics of light-production, there are still several processes of producing light which are appealing. Many years ago Geissler, Crookes, and other scientists studied the spectra of gases excited to incandescence by the electric discharge in so-called vacuum tubes. The gases are placed in transparent glass or quartz tubes at rather low pressures and a high voltage is impressed upon the ends of these tubes. When the pressure is sufficiently low, the gases will glow and emit light. Twenty-eight years ago, D. McFarlan Moore developed the nitrogen tube, which was actually installed in various places. But there is such a loss of energy near the cathode that short "vacuum" tubes of this character are very inefficient producers of light. Efficiency is greatly increased by lengthening the tubes, so Moore used tubes of great length and a rather high voltage. As a tube of this sort is used, the gas gradually disappears and it must be replenished. In order to replenish the gas, Moore devised a valve for feeding gas automatically. An advantage of this mode of light-production is that the color or quality of the light may be varied by varying the gas used. Nitrogen yields a pinkish light; neon an orange light; and carbon dioxide a white light. Moore's carbon-dioxide tube is an excellent substitute for daylight and has been used for the discrimination of colors where this is an important factor. However, for this purpose devices utilizing color-screens which alter the light from the tungsten lamp to a daylight quality are being used extensively. The vacuum-tube method of producing light has an advantage in the selection of a gas among a large number of possibilities, and some of the color effects of the future may be obtained by means of it. Claude has lately worked on light-production by vacuum tubes and has combined the neon tube with the mercury-vapor tube. The spectrum of neon to a large extent compensates for the absence of red light in the mercury spectrum, with a result that the mixture produces a more satisfactory light than that of either tube. However, this mode of light-production has not proved practicable in its present state of development. Fundamentally the limitations are those of the inherent spectral characteristics of gases. Doubtless the possibilities of the mechanisms of the tubes and of combining various gases have not been exhausted. Furthermore, if man ever becomes capable of controlling to some extent the structure of elements and of compounds, this method of light-production is perhaps more promising than others of the present day. There is another attractive method of producing light and it has not escaped the writer of fiction. H. G. Wells, with his rare skill and with the license so often envied by the writer of facts, has drawn upon the characteristics of fluorescence and phosphorescence. In his story "The First Men in the Moon," the inhabitants of the moon illuminate their caverns by utilizing this phenomenon. A fluorescent liquid was prepared in large quantities. It emitted a brilliant phosphorescent glow and when it splashed on the feet of the earth-men it felt cold, but it glowed for a long time. This is a possibility of the future and many have had visions of such lighting. If the ceiling of a coal-mine was lined with glowing fireflies or with phosphorescent material excited in some manner, it would be possible to see fairly well with the dark-adapted eyes. This leads to the class of phenomena included under the general term "luminescence." The definition of this term is not thoroughly agreed upon, but light produced in this manner does not depend upon temperature in the sense that a glowing tungsten filament emits light because it is sufficiently hot. A phosphorus match rubbed in the moist palm of the hand is seen to glow, although it is at an ordinary temperature. This may be termed "chemi-luminescence." Sidot blende, Balmain's paint, and many other compounds, when illuminated with ordinary light, and especially with ultra-violet and violet rays, will continue to glow for a long time. Despite their brightness they will be cold to the touch. This phenomenon would be termed "photo-luminescence," although it is better known as "phosphorescence." It should be noted that the latter term was carelessly originated, for phosphorus has nothing to do with it. The glow of the Geissler tube or electrically excited gas at low pressure would be an example of "electro-luminescence." The luminosity of various salts in the Bunsen-flame is due to so- called luminescence and there are many other examples of light-production which are included in the same general class. Inasmuch as light is emitted from comparatively cold bodies in these cases, it is popularly known as "cold" light. There are many instances of light being emitted without being accompanied by appreciable amounts of invisible radiant energy and it is natural to hope for practical possibilities in this direction. As yet little is known regarding the efficiency of light-production by phosphorescence. The luminous efficiency of the radiant energy emitted by phosphorescent substances has been studied, but it seems strange that among the vast works on phosphorescent phenomena, scarcely any mention is made of the efficiency of producing light in this manner. For example, assume that phosphorescent zinc sulphide is excited by the light from a mercury-arc. All the energy falling upon it is not capable of exciting phosphorescence, as may be readily shown. Assuming that a known amount of radiant energy of a certain wave-length has been permitted to fall upon the phosphorescent material, then in the dark the latter may be seen to glow for a long time. An interesting point to investigate is the relation of the output to input; that is, the ratio of the total emitted light to the total exciting energy. This is a neglected aspect in the study of light-production by this means. The firefly has been praised far and wide as the ideal light-source. It is an efficient radiator of light, for its light is "cold"; that is, it does not appear to be accompanied by invisible radiant energy. But little is said about its efficiency as a light-producer. Who knows how much fuel its lighting-plant consumes? The chemistry of light-production by living organisms is being unraveled and this part of the phenomenon will likely be laid bare before long. For an equal amount of energy radiated, the firefly emits a great many times more light than the most efficient lamp in use at the present time, but before the firefly is pronounced ideal, the efficiency of its light-producing process must be known. There are many ways of exciting phosphorescence and fluorescence, the latter being merely an unenduring phosphorescence, which ceases when the exciting energy is cut off. Ultra-violet, violet, and blue rays are generally the most effective radiant energy for excitation purposes. X-rays and the high-frequency discharge are also powerful excitants. As already stated, virtually nothing is known of the efficiency of this mode of light-production or of the mechanism within the substance, but on the whole it is a remarkable phenomenon. Radium is also a possibility in light-production and in fact has been practically employed for this purpose for several years. It or one of its compounds is mixed with a phosphorescent substance such as zinc sulphide and the latter glows continuously. Inasmuch as the life of some of the radium products is very long, such a method of illuminating watch-dials, scales of instruments, etc., is very practicable where they are to be read by eyes adapted to darkness and consequently highly sensitive to light. Whether or not radium will be manufactured by the ton in the future can only conjectured. Owing to the limitations imposed by physical laws of radiation and by the physiological processes of vision the highest luminous efficiency obtainable by heating solid materials is only about 15 per cent. of the luminous efficiency of the most luminous radiant energy. At present there are no materials available which may be operated at the temperature necessary to reach even this efficiency. Great progress in the future of light-production as indicated by present knowledge appears to lie in the production of light which is unaccompanied by invisible radiant energy. At present such phenomena as fluorescence, phosphorescence, the light of the firefly, chemi-luminescence, etc., are examples of this kind of light-production. Of course, if science ever obtains control over the constitution of matter, many difficulties will disappear; for then man will not be dependent upon the elements and compounds now available but will be able to modify them to suit his needs. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Matthew Luckiesh (2006). Artificial Light: Its Influence upon Civilization. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/17625/pg17625-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org , located at https://www.gutenberg.org/policy/license.html.

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