Thursday, 16 May 2013

366. Stephen Hawking


 

Stephen Hawking

This article is semi-protected due to vandalism.
Born
Stephen William Hawking
8 January 1942 (1942-01-08) (age 68)
Oxford, England, United Kingdom
Residence
England, United Kingdom
Nationality
Fields
Institutions
Other academic advisors
Doctoral students
Bruce Allen
Raphael Bousso
Fay Dowker
Malcolm Perry
Bernard Carr
Gary Gibbons
Harvey Reall
Don Page
Tim Prestidge
Raymond Laflamme
Julian Luttrell
Known for
Influences
Notable awards
Signature
        Stephen William Hawking, CH, CBE, FRS, FRSA (born 8 January 1942) is a British theoretical physicist, whose world-renowned scientific career spans over 40 years. His books and public appearances have made him an academic celebrity and he is an Honorary Fellow of the Royal Society of Arts, a lifetime member of the Pontifical Academy of Sciences, and in 2009 was awarded the Presidential Medal of Freedom, the highest civilian award in the United States.
        Hawking was the Lucasian Professor of Mathematics at the University of Cambridge for thirty years, taking up the post in 1979 and retiring on 1 October 2009. He is also a Fellow of Gonville and Caius College, Cambridge and a Distinguished Research Chair at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario.
He is known for his contributions to the fields of
cosmology and
quantum gravity, especially in the context of
        He has also achieved success with works of popular science in which he discusses his own theories and cosmology in general; these include the runaway best seller A Brief History of Time, which stayed on the British Sunday Times bestsellers list for a record-breaking 237 weeks.
        Hawking's key scientific works to date have included providing, with Roger Penrose, theorems regarding singularities in the framework of general relativity, and the theoretical prediction that black holes should emit radiation, which is today known as Hawking radiation (or sometimes as Bekenstein-Hawking radiation).
        Hawking has a neuro-muscular dystrophy that is related to amyotrophic lateral sclerosis (ALS), a condition that has progressed over the years and has left him almost completely paralysed.

Early life and education

When asked later to name a teacher who had inspired him, Hawking named his Mathematics teacher, Dikran Tahta.

        Once at University College, Hawking specialised in physics. His interests during this time were in thermodynamics, relativity, and quantum mechanics.
His physics tutor, Robert Berman, later said in The New York Times Magazine:
It was only necessary for him to know that something could be done, and he could do it without looking to see how other people did it. [...] He didn't have very many books, and he didn't take notes. Of course, his mind was completely different from all of his contemporaries.
Hawking was passing, but his unimpressive study habits resulted in a final examination score on the borderline between first and second class honours, making an "oral examination" necessary.
Berman said of the oral examination:
And of course the examiners then were intelligent enough to realize they were talking to someone far more clever than most of themselves.

Career in theoretical physics

Hawking's achievements were made despite the increasing paralysis caused by the ALS. By 1974, he was unable to feed himself or get out of bed. His speech became slurred so that he could only be understood by people who knew him well. In 1985, he caught pneumonia and had to have a tracheotomy, which made him unable to speak at all. A Cambridge scientist built a device that enables Hawking to write onto a computer with small movements of his body, and then have a voice synthesizer speak what he has typed.[16]

Research fields

Hawking's principal fields of research are theoretical cosmology and quantum gravity.
Professor Stephen Hawking in Cambridge.
In the late 1960s, he and his Cambridge friend and colleague, Roger Penrose, applied a new, complex mathematical model they had created from Albert Einstein's general theory of relativity. This led, in 1970, to Hawking proving the first of many singularity theorems; such theorems provide a set of sufficient conditions for the existence of a singularity in space-time. This work showed that, far from being mathematical curiosities which appear only in special cases, singularities are a fairly generic feature of general relativity.
        He supplied a mathematical proof, along with Brandon Carter, Werner Israel and D. Robinson, of John Wheeler's "No-Hair Theorem" – namely, that any black hole is fully described by the three properties of mass, angular momentum, and electric charge.
        Hawking also suggested that, upon analysis of gamma ray emissions, after the Big Bang, primordial mini black holes were formed. With Bardeen and Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics.
        In 1974, he calculated that black holes should thermally create and emit subatomic particles, known today as Hawking radiation, until they exhaust their energy and evaporate.
        In collaboration with Jim Hartle, Hawking developed a model in which the universe had no boundary in space-time, replacing the initial singularity of the classical Big Bang models with a region akin to the North Pole: one cannot travel north of the North Pole, as there is no boundary. While originally the no-boundary proposal predicted a closed universe, discussions with Neil Turok led to the realisation that the no-boundary proposal is also consistent with a universe which is not closed.
Hawking's many other scientific investigations have included
1.      the study of quantum cosmology,
2.      cosmic inflation,
3.      helium production in anisotropic Big Bang universes,
4.      large N cosmology,
5.      the density matrix of the universe,
6.      topology and structure of the universe,
7.      baby universes,
8.      Yang-Mills instantons and
9.      the S matrix,
12.  the nature of space and time, including
13.  the arrow of time,
15.  string theory,
16.  supergravity,
17.  Euclidean quantum gravity,
19.  Brans-Dicke and
20.  Hoyle-Narlikar theories of
21.  gravitation,
23.  wormholes.
At a George Washington University lecture in honour of NASA's 50th anniversary, Professor Hawking theorised on the existence of extraterrestrial life, believing that "primitive life is very common and intelligent life is fairly rare."

Losing an old bet

U.S. President Barack Obama talks with Stephen Hawking in the Blue Room of the White House before a ceremony presenting him and 15 others the Presidential Medal of Freedom on Aug. 12, 2009. The Medal of Freedom is the nation's highest civilian honour.
Hawking was in the news in July 2004 for presenting a new theory about black holes which goes against his own long-held belief about their behaviour, thus losing a bet he made with Kip Thorne and John Preskill of Caltech. Classically, it can be shown that information crossing the event horizon of a black hole is lost to our universe, and that thus all black holes are identical beyond their mass, electrical charge and angular velocity (the "no hair theorem"). The problem with this theorem is that it implies the black hole will emit the same radiation regardless of what goes into it, and as a consequence that if a pure quantum state is thrown into a black hole, an "ordinary" mixed state will be returned. This runs counter to the rules of quantum mechanics and is known as the black hole information paradox.

Mankind's future in space

At the 50th Anniversary of NASA in 2008, Hawking gave a keynote speech on the final frontier exhorting and inspiring the space technology community on why we (the human race) explore space.[21]
At the celebration of his 65th birthday on 8 January 2007, Hawking announced his plan to take a zero-gravity flight in 2007 to prepare for a sub-orbital spaceflight in 2009 on Virgin Galactic's space service. Billionaire Richard Branson pledged to pay all expenses for the latter, costing an estimated £100,000.[22] Stephen Hawking's zero-gravity flight in a "Vomit Comet" of Zero Gravity Corporation, during which he experienced weightlessness eight times, took place on 26 April 2007.[23] He became the first quadriplegic to float in zero-gravity. This was the first time in 40 years that he moved freely, without his wheelchair. The fee is normally US$3,750 for 10–15 plunges, but Hawking was not required to pay the fee. A bit of a futurist,[24] Hawking was quoted before the flight saying:
Many people have asked me why I am taking this flight. I am doing it for many reasons. First of all, I believe that life on Earth is at an ever-increasing risk of being wiped out by a disaster such as sudden nuclear war, a genetically engineered virus, or other dangers. I think the human race has no future if it doesn't go into space. I therefore want to encourage public interest in space.[25]
In an interview with The Daily Telegraph, he suggested that space was the Earth's long term hope.[26] He continued this theme at a 2008 Charlie Rose interview.[27]

Illness

Hawking on 5 May 2006, during the press conference at the Bibliothèque nationale de France to inaugurate the Laboratory of Astronomy and Particles in Paris and the French release of his work God Created the Integers.
Stephen Hawking is severely disabled by motor neuron disease also known as amyotrophic lateral sclerosis (or ALS). Hawking's illness is markedly different from typical ALS in the fact that his form of ALS would make for the most protracted case ever documented. A survival for more than 10 years after diagnosis is uncommon for ALS; the longest documented durations are 32 and 39 years and these cases were termed benign because of the lack of the typical progressive course.
When he was young, he enjoyed riding horses and playing with other children. At Oxford, he coxed a rowing team, which, he stated, helped relieve his immense boredom at the university. Symptoms of the disorder first appeared while he was enrolled at Cambridge; he lost his balance and fell down a flight of stairs, hitting his head. Worried that he would lose his genius, he took the Mensa test to verify that his intellectual abilities were intact.[29] The diagnosis of motor neuron disease came when Hawking was 21, shortly before his first marriage, and doctors said he would not survive more than two or three years. Hawking gradually lost the use of his arms, legs, and voice, and as of 2009 has been almost completely paralysed.
During a visit to the research centre CERN in Geneva in 1985, Hawking contracted pneumonia, which in his condition was life-threatening as it further restricted his already limited respiratory capacity. He had an emergency tracheotomy, and as a result lost what remained of his ability to speak. He has since used an electronic voice synthesizer to communicate.
The DECtalk DTC01 voice synthesizer he uses, which has an American accent, is no longer being produced. Asked why he has still kept it after so many years, Hawking mentioned that he has not heard a voice he likes better and that he identifies with it. Hawking is said to be looking for a replacement since, aside from being obsolete, the synthesizer is both large and fragile by current standards. As of mid 2009, he was said to be using NeoSpeech's VoiceText speech synthesizer.
In Hawking's many media appearances, he appears to speak fluently through his synthesizer, but in reality, it is a tedious drawn-out process. Hawking's setup uses a predictive text entry system, which requires only the first few characters in order to auto-complete the word, but as he is only able to use his cheek for data entry, constructing complete sentences takes time. His speeches are prepared in advance, but having a live conversation with him provides insight as to the complexity and work involved. During a Technology, Entertainment, & Design Conference talk, it took him seven minutes to answer a question.[31]
He describes himself as lucky despite his disease. Its slow progression has allowed him time to make influential discoveries and has not hindered him from having, in his own words, "a very attractive family."[32] When his wife, Jane, was asked why she decided to marry a man with a three-year life expectancy, she responded, "Those were the days of atomic gloom and doom, so we all had a rather short life expectancy."
On 20 April 2009, Cambridge University released a statement saying that Hawking was "very ill" with a chest infection, and was admitted to Addenbrooke's Hospital. The following day, it was reported that his new condition is "comfortable" and he should make a full recovery from the infection.
In 2009, Investor's Business Daily (IBD) claimed in an editorial,[36] "People such as scientist Stephen Hawking wouldn't have a chance in the UK, where the National Health Service would say the life of this brilliant man, because of his physical handicaps, is essentially worthless." This caused widespread criticism, as Hawking has in fact lived and worked in the UK his entire life and has relied extensively on NHS treatments. Hawking personally replied that, "I wouldn't be here today if it were not for the NHS," he said. "I have received a large amount of high-quality treatment without which I would not have survived." Eventually, IBD issued a correction,[39] but continued to defend the original editorial, calling the mention of Hawking a "bad example" and accusing those that mentioned their error of "chang[ing] the subject."[40]

As popular science advocate

Hawking has played himself on many television shows and has been portrayed in many more. He has played himself on a Red Dwarf anniversary special, played a hologram of himself on the episode "Descent" of Star Trek: The Next Generation, appeared in a skit on Late Night with Conan O'Brien, and appeared on the Discovery Channel special Alien Planet.[41] He has also played himself in several episodes of The Simpsons and Futurama. When he was portrayed on episodes of Family Guy, the voice was actually done by a speech synthesizer on a Macintosh computer, according to DVD Commentary. He has also appeared in an episode of the Dilbert cartoon. His actual synthesizer voice was used on parts of the Pink Floyd song "Keep Talking" from the 1994 album The Division Bell, as well as on Turbonegro's "Intro: The Party Zone" on their 2005 album Party Animals, Wolfsheim's "Kein Zurück (Oliver Pinelli Mix)". As well as being fictionalised as nerdcore hip hop artist MC Hawking, he was impersonated in duet with Richard Cheese on a cover of "The Girl Is Mine". In 2008, Hawking was the subject of and featured in the documentary series Stephen Hawking, Master of the Universe for Channel 4. He was also portrayed in the movie "Superhero Movie" by Robert Joy. In the TV series Dark Angel Logan's technology savvy colleague Sebastian is characterized with many similarities to the actual physicist. In September 2008, Hawking presided over the unveiling of the 'Chronophage' Corpus Clock (time eating) clock at Corpus Christi College Cambridge.[42]

Recognition

Acclaim

On 19 December 2007, a statue of Professor Stephen Hawking by renowned late artist Ian Walters was unveiled at the Centre for Theoretical Cosmology, Cambridge University.[43] In May 2008 the statue of Hawking was unveiled at the African Institute for Mathematical Sciences in Cape Town. The Stephen W. Hawking Science Museum in San Salvador, El Salvador is named in honour of Stephen Hawking, citing his scientific distinction and perseverance in dealing with adversity.[44] Stephen Hawking Building in Cambridge, opened on 17 April 2007. The building belongs to Gonville and Caius College and is used as an undergraduate accommodation and conference facility.[45]

Distinctions

Hawking's belief that the lay person should have access to his work led him to write a series of popular science books in addition to his academic work. The first of these, A Brief History of Time, was published on 1 April 1988 by Hawking, his family and friends, and some leading physicists. It surprisingly became a best-seller and was followed by The Universe in a Nutshell (2001). Both books have remained highly popular all over the world. A collection of essays titled Black Holes and Baby Universes (1993) was also popular. His most recent book, A Briefer History of Time (2005), co-written by Leonard Mlodinow, aims to update his earlier works and make them accessible to an even wider audience. He and his daughter, Lucy Hawking, have recently published a children's book focusing on science that has been described to be "like Harry Potter, but without the magic." This book is called George's Secret Key to the Universe and includes information on Hawking radiation.
Hawking is also known for his wit; he is famous for his oft-made statement, "When I hear of Schrödinger's cat, I reach for my pistol." This was a deliberately ironic paraphrase of "Whenever I hear the word culture... I release the safety-catch of my Browning", from the play Schlageter (Act 1, Scene 1) by German playwright and Nazi Poet Laureate Hanns Johst. His wit has both entertained the non-specialist public and helped them to understand complex questions. Asked in October 2005 on the British daytime chat show Richard & Judy, to explain his assertion that the question "What came before the Big Bang?" was meaningless, he compared it to asking "What lies north of the North Pole?"
Hawking has generally avoided talking about politics at length, but he has appeared on a political broadcast for the United Kingdom's Labour Party. He supports the children's charity SOS Children's Villages UK.[46]

Religious views

Hawking takes an agnostic position on matters of religion, He has repeatedly used the word 'God' (in metaphorical meanings) to illustrate points made in his books and public speeches. His ex-wife Jane however said he was an atheist during their divorce proceedings, Hawking has stated that he is "not religious in the normal sense" and he believes that "the universe is governed by the laws of science. The laws may have been decreed by God, but God does not intervene to break the laws."

365. What Is Vertigo?


What Is Vertigo?

What Causes Vertigo?


Vertigo is a feeling of dizziness, the patient feels that all around him is moving or spinning. Vertigo is usually caused by an inner ear problem, but may also be linked to some kind of eyesight problem.

Most of us have the occasional dizzy spell; vertigo is different. Vertigo is a persistent sense of motion, a feeling of tilting, swaying, spinning, when nothing is moving. The sensations are typically accompanied by sweating, vomiting and nausea.

People with vertigo often feel that things around them are moving when they are standing completely still.

Vertigo is medically different from dizziness, lightheadedness, and unsteadiness. Lay people commonly use the terms dizziness and vertigo indistinctly. If this happens, it is important for a doctor to determine exactly what the patient is trying to describe.

Doctors say that vertigo is more severe than dizziness, which commonly happens when a person stands up and feels light-headed. People with vertigo may find it harder to move around because the spinning sensation tends to affect balance.

"Vertigo" is often used, incorrectly, to describe the fear of heights, but the correct term for this is acrophobia. The medical term vertigo can occur at any time and may last for days, weeks, months, and even years, while acrophobia symptoms only occur only when the person is high up and looking down. However, vertigo is so commonly used 'incorrectly' by lay people that it would be naive today to say it only has one meaning.

What are the symptoms of vertigo?

The patient may feel that his/her surroundings seem to be moving either vertically or horizontally. There may also be a sensation of spinning. Sometimes the feeling may be so slight that it is hardly noticeable. However, for some people the severity of symptoms makes it hard to keep balance and carry out everyday tasks.

A bout of vertigo can last from a few minutes to several days, and sometimes much longer. The following symptoms are possible:
  • A sensation that everything around you is moving or spinning
  • Loss of balance
  • Nausea
  • Vomiting
  • Light-headedness
  • Problems walking properly
  • Problems standing still properly
  • Blurred vision
  • Earache

What are the causes of vertigo?

Vertigo can be caused by a problem with the balance mechanisms of the inner ear, a problem with the brain, or a problem with the nerves that connect the brain to the middle ear.

Labyrinthitis
Inflammation of the labyrinth, a system of canals and cavities within the inner ear which gives us our sense of balance. The sudden onset of a feeling of vertigo caused by labirynthitis is triggered by head or body movement, and is usually accompanied by a feeling of nausea and malaise.


Labyrinthitis may be caused by a viral or bacterial infection. Viral infections, such as a common cold or flu can spread to the labyrinth - labyrinthitis. Bacterial infections are less common.

The patient may also have a painful ear and fever.
Vestibular neuritis
The vestibule is in the inner ear. It is like an internal carpenter's level. The vestibule and the semicircular canals work with the brain to control balance. Vestibular neuritis is inflammation of the vestibular nerve - the nerve running to the vestibule. Vestibular neuritis often follows an upper respiratory infection. Patients will experience vertigo, but will not usually have ringing in the ear (tinnitus) or hearing problems.
Benign paroxysmal positional vertigo (BPPV)
The vestibular labyrinth, inside the ear, includes semicircular canals (loop-shaped structures) that contain fluid and tiny hair-like sensors that monitor the rotation of the head. The otolith organs, also in the ear, monitor movements of the head and its position. There are crystals in the otolith organs that make us sensitive to movement. Sometimes, when the patient is lying down, these crystals can become dislodged and move into one of the semicircular canals, making it sensitive to head position changes - something it would not normally do. This unusual response to head movements by the semicircular canal can give patients vertigo symptoms.

BBPV most commonly occurs in elderly patients. A blow to the head can cause BBPV; even a minor blow. BBPV can also be caused by disorders that damage the inner ear, infection, ear surgery damage, or if the patient has been lying on his/her back for too long.

Most BBPV attacks clear up within a few days. The condition generally goes away within a few weeks or months, but can sometimes recur.
Meniere's disease
Dysfunction of the semi-circular canals (endolymphatic sac) in the inner ear. Patients experience recurrent vertigo, as well as tinnitus and loss of hearing in the affected ear, abnormal eye movements, nausea, and vomiting. People with Meniere's disease usually find that the tinnitus gets worse over time. Hearing loss may start off as intermittent, but gradually progresses until it becomes permanent.
Head injury
Some patients can develop vertigo after a head injury. If you have had a head injury and subsequently experience vertigo or dizziness you should tell your doctor straight away.
Migraine
Usually characterized by periodic headaches and some vision problems, such as seeing stars (as if someone had quickly flashed a strong light in your eyes). Some migraine patients also experience dizziness and vertigo. In fact, for some migraine patients, vertigo can eventually become the only symptom. Some studies have shown that migraine patients who experience vertigo during their attacks tend to show a higher lifetime prevalence of migraine.
Chronic otitis media
Long-term infection of the inner ear, or infection of the inner ear that recurs over a long period. Some patients with chronic otitis media have episodes of vertigo.
Acoustic neuroma
A benign (non-cancerous) tumor that develops on the acoustic nerve of the inner ear; this nerve is involved in helping us balance. Patients who do experience vertigo usually have mild symptoms.
Dehydration
Dehydration may lead to feelings of lightheadedness, dizziness, and/or vertigo, especially when changing positions. This symptom is due to a drop in blood pressure.
Some medications
Salicylates, quinine, and aminoglycosides may sometimes cause vertigo.
Boat, airplane, car travel (motion sickness)
Some people experience vertigo during and/or after a plane, boat, or even a car trip. This may last from a few minutes, hours to a couple of days.
Earthquakes
Some people who have been in a strong earthquake can suddenly feel that the firm ground around them moves long after the earthquake is over. This sudden sensation can occur on-and-off over a number of days, and sometimes weeks.

I was in the devastating Mexico City earthquake of 1985 (Richter 8.2). For a couple of weeks I would occasionally feel that the firm ground was wobbling - the sensation would last a couple of seconds and slightly affected my balance. I know a number of people who had to sit down when this happened to them.


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