Saturday, 5 July 2008

Does the Sun look smaller to you?

Criminy, I almost forgot: today, July 4th, at roughly 08:00 UT, the Earth was at aphelion.

Uh, what? I hear you ask. OK, brief astrolesson for ya, then back to the grill!

The Earth does not orbit the Sun in a perfect circle. The orbit is slightly elliptical. If you were to draw the Earth’s orbit on a piece of paper, you’d need a sharp eye to detect its non-circularity, but deviant it is. What this means in real terms is that the Earth ranges from about 148 to about 152 million kilometers from the Sun over the course of six months (which is how long it takes to get from one side of the orbit to the other, of course).

When the Earth is closest to the Sun it’s at perihelion, and when it’s farthest it’s called aphelion (I usually pronounce that app-helion, if you care, though I’ve heard others say aff-helion). So today we passed aphelion, and slowly but inexorably, over the next six months we’ll draw slightly closer to the Sun, and then the whole thing repeats.

That 4 million km difference sounds like a lot. But over the 150 million average radius of the orbit it’s only a slight difference by eye. The Sun will look about 3% larger at perihelion versus aphelion, and you’d never notice that, especially since the change is slow and takes six months. The amount of sunlight hitting the Earth does increase at perihelion, being about 5% greater than at aphelion. That’s quite a bit! But the effect isn’t as bad as you’d think. Why not?

For us northern hemisphere folks, we are farthest from the Sun in summer, and closest in winter, so that mitigates the temperature extreme. On average, winters are a bit warmer and summers a bit cooler. But wait! In the southern hemisphere, the seasons are reversed! So they should have extra hot summers and extra cold winters.

But they don’t. Why not? Because the southern hemisphere is mostly water. Go ahead, find a globe and take a look; it’s incredible how much of that half the Earth is water bound. Water absorbs and releases heat slowly, so all summer the oceans suck down that extra solar energy, and release it all winter. That helps balance out the temperature extremes.

Oh, one more thing: the Earth precesses, that is, the axis of rotation moves like a wobbling top. It takes a long time for the wobble to make one cycle, well over 20,000 years. But this changes the timing of the seasons compared to the orbit. In a few millennia, we’ll have perihelion at the same time as northern summer, and aphelion at northern winter. It’s hard to say what effect this will have on the environment, since it brings extra-hot summers and extra-cold winters. However, the last time this happened was around the same time the Sahara forest went away and was replaced by, well, guess.

But for today, don’t fret too much about wandering poles and aphelion… except to say, if you’re out sweltering in the Sun today celebrating the holiday in the U.S., you might want to take just a moment and be glad our orbit isn’t more elliptical, or that it isn’t 15,000 AD.

Tuesday, 1 July 2008

Sleep paralysis

Sleep paralysis is a condition characterized by temporary paralysis of the body shortly after waking up (known as hypnopompic paralysis) or, less often, shortly before falling asleep (known as hypnagogic paralysis).[1] Physiologically, it is closely related to the paralysis that occurs as a natural part of REM (rapid eye movement) sleep, which is known as REM atonia. Sleep paralysis occurs when the brain awakes from a REM state, but the bodily paralysis persists. This leaves the person fully aware, but unable to move. In addition, the state may be accompanied by hypnagogic hallucinations. More often than not, sleep paralysis is believed by the person affected by it to be no more than a dream. This explains many dream recountings which describe the person lying frozen and unable to move. The hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as a dream, since completely fanciful, or dream-like, objects may appear in the room alongside one's normal vision.
Possible causesSleep paralysis occurs during REM sleep, thus preventing the body from manifesting movements made in the subject's dreams. Very little is known about the physiology of sleep paralysis. However, some have suggested that it may be linked to post-synaptic inhibition of motor neurons in the pons region of the brain. In particular, low levels of melatonin may stop the depolarization current in the nerves, which prevents the stimulation of the muscles, to prevent the body from enacting the dreamt activity (e.g. preventing a sleeper from flailing his legs when dreaming about running). Many people who commonly enter sleep paralysis also suffer from narcolepsy. Especially in African-Americans panic disorder often co-occurs with sleep paralysis[2]. However, various studies suggest that many or most people will experience sleep paralysis at least once or twice in their lives. Some reports read that various factors increase the likelihood of both paralysis and hallucinations. These include: [3]
Sleeping in an upwards supine position
Irregular sleeping schedules; naps, sleeping in, sleep deprivation
Increased stress
Sudden environmental/lifestyle changes
A lucid dream that immediately precedes the episode. Also conscious induction of sleep paralysis is a common technique to enter a state of lucid dreams, also known as WILD .
Artificial sleeping aids, ADD medications and/or antihistamines
Recent use of hallucinogenic drugs
TreatmentDuring paralysis episodes, patients may be advised to try moving the facial muscles and moving eyes from one side to the other. This may hasten the termination of the attack. Clonazepam is highly effective in the treatment of sleep paralysis.[4] The initial dose is 0.5 mg at bedtime, while an increase to 1 mg per night might be necessary to maintain potency. Anecdotal reports indicate SSRIs such as fluoxetine markedly decrease the incidence of sleep paralysis. Several people who have been both on and off SSRIs have reported corresponding decreases and increases in sleep paralysis episodes. Others report no effects at all.
Cultural referencesComplete references to many cultures are given in the References section
In Vietnamese, sleep paralysis is referred to as "ma de", meaning "held down by a ghost". Most people in this culture believe that a ghost has entered your body, causing the paralysis state.
In Japanese, sleep paralysis is referred to as kanashibari (, literally "bound or fastened in metal," from kane "metal" and shibaru "to bind, to tie, to fasten"). This term is occasionally used by English speaking authors to refer to the phenomenon both in academic papers and in pop psych literature.
In Hungarian folk culture sleep paralysis is called "lidércnyomás" ("lidérc pressing") and can be attributed to a number of supernatural entities like "lidérc", "boszorkány" (witch), "tündér" (fairy) or "ördögszerető".[5] The word "boszorkány" itself stems from the Turkish root "bas-", meaning "to press".[6]
Kurdish people call this phenomenon a "mottaka", they believe that some one, in a form of a ghost or perhaps an evil spirit, turns up on top the of the person in the middle of the night and suffocates him/her. Apparently this happens usually when some one has done something bad.
In New Guinea, people refer to this phenomenon as "Suk Ninmyo", believed to originate from sacred trees that use human essence to sustain its life. The trees are said to feed on human essence during night as to not disturb the human's daily life, but sometimes people wake unnaturally during the feeding, resulting in the paralysis.
In Turkey this is called "karabasan" ("black-pressing"). It is believed that it is a creature which attacks people in their sleep.
In Mexico, it's believed that sleep paralysis is in fact the spirit of a dead person getting on the person and impeding movement, calling this "se me subió el muerto" (the dead person got on me).
Ogun Oru is a traditional explanation for nocturnal disturbances among the Yoruba of Southwest Nigeria; ogun oru (nocturnal warefare) involves an acute night-time disturbance that is culturally attributed to demonic infiltration of the body and psyche during dreaming. Ogun oru is characterized by its occurrence, a female preponderance, the perception of an underlying feud between the sufferer's earthly spouse and a ;spiritual' spouse, and the event of bewitchment through eating while dreaming. The condition is believed to be treatable through Christian prayers or elaborate traditional rituals designed to exorcise the imbibed demonic elements. [7]
Several studies have shown that African-Americans may be predisposed to isolated sleep paralysis also known as "the witch is riding you," or "the haint is riding you." [8] In addition, other studies have shown that African-Americans who have frequent episodes of isolated sleep paralysis, i.e., reporting having one or more sleep paralysis episodes per month coined as "sleep paralysis disorder," were predisposed to having panic attacks. [9] This finding has been replicated by other independent researchers [10] [11]
Sleep paralysis in literature, art and music
(1605) Miguel de Cervantes makes mention of the phenomenon in Don Quixote when a tavern wench jumps into the bed of the soundly sleeping Sancho Panza, who, started, and feeling a prodigious weight upon him, thought he was labouring under the nightmare.
(1851) There is a particularly fascinating account of sleep paralysis in Herman Melville's novel Moby-Dick. Chapter 4 (The Counterpane) is an account of Ishmael's meditation on an episode of sleep paralysis in the middle of which he could not distinguish the difference between Queequeg's arm and the quilt. Indeed, he could not even distinguish the difference between his own body and his surroundings. He then recalls an earlier episode of sleep paralysis from his childhood, which he determines was the precise moment he discovered the feeling of "otherness" of his own body with respect to his surroundings.
(1936) An account can also be found in Ernest Hemingway's The Snows of Kilimanjaro, in which death approaches and sits upon the narrator's chest so that he cannot breathe.
(1969) The main character in Kingsley Amis' novel The Green Man also suffers from the affliction.
(1975) Maxine Hong Kingston recounts an episode in her book The Woman Warrior where her mother, Brave Orchid, suffers a night of sleep paralysis in the "Haunted Room", in which she claims she battles a "Sitting Ghost".
In Zimbabwean Shona culture the word Madzikirira is used referring to the fact that something will really be pressing you down and mostly they refer to the spiritual world where some other spirit especially evil one will be trying to use you. The people believe that witches can only be people of close relations to be effective and hence a witch can try to use your spirit to bewitch your relatives.
(2001) The progressive rock band Dredg explores the different aspects of sleep paralysis, on their album El Cielo. The booklet with El Cielo contains letters written by sufferers of sleeping disorders with descriptions of various experiences with or relating to sleep paralysis. Singer Gavin Hayes incorporates and expands upon the material found in the booklet for the lyrics to the album; all of the songs on the album (except the instrumentals) contain snippets of the text in the booklet.
(2006) Experimental band Fear Before the March of Flames talk about the struggles of dealing with constant sleep paralysis on their album "The Always Open Mouth". One of the songs is even called "Drowning the Old Hag".
Notes
1. ^ When considered a disease, isolated sleep paralysis is classified as: Diseases Database 12182, MeSH D0201882. ^ Friedman, S. & Paradis, C. (2002). Panic disorder in African-Americans: Symptomatology and isolated sleep paralysis. Culture, Medicine and Psychiatry, 26,179-198.3. ^ J. A. Cheyne. Preventing and Coping with Sleep Paralysis. Retrieved on 17 July, 2006.4. ^ Wills L, Garcia J. (2002) Parasomnias: epidemiology and management16(12):803-10.5. ^ lidérc, Magyar Néprajzi Lexikon, Akadémiai Kiadó, Budapest 1977, ISBN6. ^ boszorkány, Magyar Néprajzi Lexikon, Akadémiai Kiadó, Budapest 1977, ISBN7. ^ Aina OF, Famuyiwa OO (2007). "Ogun Oru: a traditional explanation for nocturnal neuropsychiatric disturbances among the Yoruba of Southwest Nigeria". Transcultural psychiatry 44 (1): 44-54. DOI:10.1177/1363461507074968. PMID 17379609. 8. ^ Bell CC, Shakoor B, Thompson B, Dew D, Hughley E, Mays R, Shorter-Gooden K (1984). "Prevalence of isolated sleep paralysis in black subjects". Journal of the National Medical Association 76 (5): 501-508. PMID 6737506. 9. ^ Bell CC, Dixie-Bell DD, Thompson B (1986). "Further studies on the prevalence of isolated sleep paralysis in black subjects". Journal of the National Medical Association 78 (7): 649-659. PMID 3746934. 10. ^ Paradis CM, Friedman S (2006). "Sleep Paralysis in African Americans with Panic Disorder". Transcultural psychiatry 43 (4): 692-694. PMID 15881272. 11. ^ Friedman S, Paradis CM, Hatch M (1994). "Characteristics of African-Americans and white patients with panic disorder and agoraphobia". Hospital and Community Psychiatry 45 (8): 798-803. PMID 7982696.
References
Bower, Bruce (July 9, 2005). "Night of the Crusher." Science News.
Conesa, J. (2000). Geomagnetic, cross-cultural and occupational faces of sleep paralysis: An ecological perspective. Sleep and Hypnosis, 2, (3), 105-111.
Conesa, J. (2002). Isolated Sleep Paralysis and Lucid Dreaming: Ten-year longitudinal case study and related dream frequencies, types, and categories. Sleep and Hypnosis, 4, (4), 132-143.
Conesa, J. (2003). Sleep Paralysis Signaling (SPS) As A Natural Cueing Method for the Generation and Maintenance of Lucid Dreaming. Presented at The 83rd Annual Convention of the Western Psychological Association, May 1 - 4, 2003 in Vancouver, BC, Canada.
Conesa-Sevilla, Jorge (2004). Wrestling With Ghosts: A Personal and Scientific Account of Sleep Paralysis. Pennsylvania: Xlibris/Randomhouse.
Firestone K. The “Old Hag”: sleep paralysis in Newfoundland. The Journal of Psychoanalytic Anthropology 1985; 8:47-66.
Fukuda K, Miyasita A, Inugami M, Ishihara K. High prevalence of isolated sleep paralysis: kanashibari phenomenon in Japan. Sleep 1987; 10:279-286.
Hartmann E. The nightmare: the psychology and biology of terrifying dreams. New York:Basic,1984.
Hufford D.J. The terror that comes in the night: an experience-centered study of supernatural assault traditions. Philadelphia:University of Pennsylvania Press, 1982
Kettlewell, N; Lipscomb, S; Evans, E. (June, 1993). "Differences in neuropsychological correlates between normals and those experiencing "Old Hag Attacks'." Perceptual and Motor Skills. 76 (3 Pt 1): 839-45; discussion 846. PMID 8321596
Ness RC. “The Old Hag” phenomenon as sleep paralysis: a bicultural interpretation . Culture, Medicine and Psychiatry 1978; 2:15-39.
Ohayon MM, Zulley J, Guilleminault C, Smirne, S. Prevalence and pathologic associations of sleep paralysis in the general population. Neurology, 1999; 52:1194-1200.
Sagan, Carl (1997). The Demon-Haunted World: Science as a Candle in the Dark.
Schneck JM. Sleep paralysis and microsomatognosia with special reference to hypnotherapy . The International Journal of Clinical and Experimental Hypnosis 1977; XXV:72-77.
Takeuchi T, Miyasita A, Sasaki Y, Inugami M, Fukuda K. Isolated sleep paralysis elicited by sleep interruption. American Sleep Disorders Association and Sleep Research Society, 1992; 15: 217-225.

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