A prayer wheel is a cylindrical object on a spindle made from metal, wood, stone, leather, or coarse cotton. Traditionally, the mantra Om Mani Padme Hum is written in Sanskrit externally on the wheel. Sometimes Dakinis, Protectors, and very often the eight auspicious symbols known as Ashtamangala are depicted. According to the Tibetan Buddhist tradition, spinning such a wheel will have much the same meritorious effect as orally reciting the prayers.

It is said that prayer wheels are used to accumulate wisdom and merit, and to purify negativities such as bad karma. The idea of spinning mantras comes from numerous Tantric practices where the Tantric practitioner visualizes mantras revolving around the meridian chakras such as the heart and crown. Therefore, prayer wheels are a visual aid for developing one’s capacity for these types of Tantric visualizations.

The spiritual method for those practicing with a prayer wheel is very specific. The practitioner most often spins the wheel clockwise, for the direction the mantras are written is that of the movement of the sun across the sky. Before, during and after the practitioner turns the wheel, it is best to focus the mind and repeat the Om Mani Padme Hum mantra, as this increases the merit earned by the wheel’s use. However, it is said that even turning it while distracted has benefits and merits, and that even insects that cross a prayer wheel’s shadow will gain some benefit.

Some prayer wheels are powered by electric motors. Thardo Khorlo, as these electric wheels are sometimes known, contain one thousand copies of the mantra Om Mani Padme Hum and many copies of other mantras. The Thardo Khorlo can be accompanied by lights and music if one so chooses. However, Lama Zopa Rinpoche has said, “The merit of turning an electric prayer wheel goes to the electric company. This is why I prefer practitioners to use their own right energy to turn a prayer wheel”.

The Dalai Lama has commented that animations on websites work just as well as other prayer wheels. As the animated image turns, waves of compassion emanate in all directions to the surrounding area. Some have suggested that the spinning of a hard drive at several thousand rotations per minute can act in similar function to a prayer wheel by saving an image of Om mani padme hum or other mantras on a local computer or server.

Rubin’s vase is a famous set of cognitive optical illusions developed around 1915 by the Danish psychologist Edgar Rubin. The illusion generally presents the viewer with a mental choice of two interpretations, each of which is valid. Often, the viewer sees only one of them, and only realizes the second valid interpretation after some time or prompting. When the viewer attempts to simultaneously see the interpretations together, they suddenly cannot see the first interpretation anymore, and no matter how they try they simply cannot encompass both interpretations simultaneously; one occludes the other.

The illusions are useful because they are an intuitive demonstration of the figure-ground distinction the brain makes during visual perception. Rubin’s figure-ground distinction influenced the Gestalt psychologists, who discovered many similar illusions themselves. It involves higher-level cognitive pattern matching in which the overall picture determines its mental interpretation, rather than the net effect of the individual pieces.

Normally the brain classifies images by what surrounds what, establishing depth and relationships. If something surrounds another thing, the surrounded object is seen as figure, and the presumably further away (and hence background) object is the ground, and vice versa. This makes sense, since if a piece of fruit is lying on the ground, one would want to pay attention to the “figure” and not the “ground”.

However, when the contours are not so unequal, ambiguity starts to creep into the previously simple inequality and the brain must begin “shaping” what it sees. It can be shown that this shaping overrides and is at a higher level than feature recognition processes that pull together the face and the vase images. One can think of the lower levels putting together distinct regions of the picture (each region of which makes sense in isolation), but when the brain tries to make sense of it as a whole, contradictions ensue, and patterns must be discarded.

The Meyer lemon is a citrus fruit native to China, thought to be a cross between a true lemon and a mandarin orange or sweet orange. The Meyer lemon was introduced to the United States in 1908 by the agricultural explorer Frank Nicholas Meyer, an employee of the United States Department of Agriculture who collected a sample of the plant on a trip to China. It is commonly grown in China potted as an ornamental plant.

The fruit is yellow and rounder than a true lemon with a slight orange tint when ripe. It has a sweeter, less acidic flavor than the more common grocery store varieties of lemon and has a fragrant edible skin. All lemons are widely known as powerful digestive aids. The combination of high acidity and fiber are effective in cleansing digestion organs.

The white coating or inner rind of a lemon contains the highest vitamin content per volume of most any food. Some studies show that the white coating of a single lemon can contain ten times the amount of Vitamin C as an entire bottle of Vitamin C supplements.

A lemon battery is a device used in experiments proposed in many science textbooks around the world. It is made by inserting two different metallic objects, for example a galvanized nail and a copper coin, into a lemon. The copper coin serves as the positive electrode or cathode and the galvanized nail as the electron-producing negative electrode or anode. These two objects work as electrodes, causing an electrochemical reaction which generates a small potential difference.

In practice, a single lemon battery is incapable of lighting a light bulb. One would need about 500 lemons wired in parallel to light a standard flashlight bulb.

The Ganzfeld effect is a phenomenon of visual perception caused by staring at an undifferentiated and uniform field of color. The effect is described as the loss of vision as the brain cuts off the unchanging signal from the eyes. The result is “seeing black” or apparent blindness. The word is from German for “complete field”.

The effect is the result of the brain amplifying neural noise in order to look for the missing visual signals. The noise is interpreted in the higher visual cortex, and gives rise to hallucinations. This is similar to dream production because of the brain’s state of sensory deprivation during sleep.

The Ganzfeld effect has been reported since ancient times. The adepts of Pythagoras retreated to pitch black caves to receive wisdom through their visions. Miners trapped by accidents in mines frequently reported hallucinations, visions and seeing ghosts when they were in the pitch dark for days. Arctic explorers seeing nothing but featureless landscape of white snow for a long time also reported hallucinations and an altered state of mind.

In Tibetan Buddhism a dark retreat refers to advanced practices of isolation in darkness. The time period dedicated to dark retreat varies from a few hours to decades. Dark retreat in the Himalayan tradition is a restricted practice only to be engaged by the senior spiritual practitioner under appropriate spiritual guidance. This practice is considered conducive for navigating the bardo at the time of death and for realising the rainbow body. The traditional dark retreat requires stability in the natural state and is only suitable for advanced practitioners.

Ancient Egyptians and Mayans practiced a form of the dark retreat as well, traditionally lasting 10 days. Holy men would enter into the center of their respective pyramids, completely removed from light and sound, and have visions of the workings of the universe. Today, scientists have hypothesized that when the human body is deprived of visual stimulation, the brain produces a substance called Dimethyltryptamine (DMT), a tryptamine, which results in intense visions.

Brainwave synchronization is a practice that aims to cause brainwave frequency to synchronize with a frequency corresponding to the intended brain state. The technique has been used to induce sleep or to treat numerous psychological and physiological conditions.

It is usually performed with the use of specialized medical software. It depends upon a “frequency following” response, a naturally occurring phenomenon where the human brain has a tendency to change its dominant EEG frequency to the frequency of a dominant external stimulus. Such a stimulus may be aural, as in the case of binaural or monaural beats and isochronic tones, or visual, as with a dreamachine, a combination of the two with a mind machine, or even electromagnetic radiation.

Brainwave synchronization has been used in one form or another for centuries, from shamanistic societies’ use of drum beats to Ptolemy noting in 200 A.D. the effects of flickering sunlight generated by a spinning wheel. In the 1930s and ’40s, with then-new EEG equipment and strobe lights, W. Gray Walter performed some of the first scientific research on the subject. Later, in the 1960s and ’70s, interest in altered states led many artists to become interested in the subject, most notably Brion Gysin who, along with a Cambridge math student, invented the Dreammachine.

From the 1970s to date there have been numerous studies and various machines built that combine light and sound. These efforts were aided by continued development of micro circuitry and other electronic breakthroughs allowing for ever more sophisticated equipment for measuring and inducing brainwave synchronization. One of the most important breakthroughs was the discovery of binaural beats, first published in Scientific American in 1973 by Gerald Oster. With the development of isochronic tones by Arturo Manns, combined with more sophisticated equipment, these discoveries led to many attempts to use brainwave synchronization in the treatment of numerous diseases and disorders.

Stendhal syndrome is a psychosomatic illness that causes rapid heartbeat, dizziness, fainting, confusion and hallucinations when an individual is exposed to art, usually when the art is particularly beautiful or a large amount of art is in a single place. The term can also be used to describe a similar reaction to other circumstances, as when confronted with immense beauty in the natural world.

The illness is named after the famous 19th century French author Marie-Henri Stendhal, who described his experience with the phenomenon during his 1817 visit to Florence, Italy in his book Naples and Florence: A Journey from Milan to Reggio.

Although there are many descriptions, dating from the early 19th century on, of people becoming dizzy and fainting while taking in Florentine art, the syndrome was only named in 1979, when it was described by Italian psychiatrist Graziella Magherini, who observed and described more than 100 similar cases among tourists and visitors in Florence. The syndrome was first diagnosed in 1982. The term is also used when describing the reactions of audiences to music of the Romantic period.

It is similar but not identical to Paris Syndrome, a transient psychological disorder encountered by some people visiting or vacationing in Paris, France. The symptoms occur during a trip which confronts the traveller with things they had not previously experienced and did not anticipate. The symptoms did not exist before the trip and they disappear with a return to familiar surroundings.

Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters. Spiral galaxies make up approximately 60% of galaxies in the local Universe. They are mostly found in low-density regions and are rare in the centers of galaxy clusters.

Spiral galaxies are named for the spiral structures that extend from the center into the disk. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disk because of the hot, massive stars that inhabit them. Spiral arms contain a great many young, blue stars, which make the arms so remarkable. Roughly half of all spirals are observed to have an additional component in the form of a bar-like structure, extending from the central bulge, at the ends of which the spiral arms begin.

Our own Milky Way has recently been confirmed to be a barred spiral, although the bar itself is difficult to observe from our position within the Galactic disk. The most convincing evidence for its existence comes from a recent survey, performed by the Spitzer Space Telescope, of stars in the Galactic center.

Bertil Lindblad proposed that the arms represent regions of enhanced density waves that rotate more slowly than the galaxy’s stars and gas. As gas enters a density wave, it gets squeezed and makes new stars, some of which are short-lived blue stars that light the arms.

This idea was developed into density wave theory by C. C. Lin and Frank Shu in 1964. They suggested that the spiral arms were manifestations of spiral density waves, attempting to explain the large-scale structure of spirals in terms of a small-amplitude wave propagating with fixed angular velocity, that revolves around the galaxy at a speed different from that of the galaxy’s gas and stars.

Watermelon snow, also called snow algae, is snow that is reddish or pink in color, with the slight scent of a fresh watermelon. Compressing the snow by stepping on it or making snowballs leaves it looking red. Walking on watermelon snow often results in bright red soles and pinkish pant cuffs.

This type of snow is common during the summer in alpine and coastal polar regions worldwide, such as the Sierra Nevada of California. The snow is caused by the presence of Chlamydomonas nivalis, a species of green algae containing a secondary red carotenoid pigment. Unlike most species of fresh-water algae, it is cold-loving and thrives in freezing water. At altitudes of 10,000 to 12,000 feet, the temperature is cold throughout the year, and the snow has lingered from winter storms.

Chlamydomonas nivalis owes its red color to a bright red pigment which protects the chloroplasts from intense visible and ultraviolet radiation. They also absorb heat, which provides the algae with liquid water as the snow melts around it. Algal blooms may extend to a depth of 10 inches. It has been calculated that a teaspoon of melted snow contains a million or more of these cells.

The algae sometimes accumulate in “sun cups”, which are shallow depressions in the snow. The carotenoid pigment absorbs heat and as a result it deepens the sun cups and accelerates the melting rate of snowbanks. During the winter months when snow covers them, the algae become dormant. In spring, increased levels of light and melting water stimulate germination.

The first accounts of watermelon snow are in the writings of Aristotle. Watermelon snow has puzzled mountain climbers, explorers, and naturalists for thousands of years, some speculating that it was caused by mineral deposits or oxidation products that were leached from rocks.