## Posts Tagged ‘**sains**’

## Stephen Hawking at 70: Exclusive interview – opinion – 04 January 2012 – New Scientist

Einstein referred to the cosmological constant as his “biggest blunder”. What was yours?

I used to think that information was destroyed in black holes. But the AdS/CFT correspondence led me to change my mind. This was my biggest blunder, or at least my biggest blunder in science.

NS:Black holes consume everything, including information, that strays too close. But in 1975, together with the Israeli physicist Jakob Bekenstein, Hawking showed that black holes slowly emit radiation, causing them to evaporate and eventually disappear. So what happens to the information they swallow? Hawking argued for decades that it was destroyed – a major challenge to ideas of continuity, and cause and effect. In 1997, however, theorist Juan Maldacena developed a mathematical shortcut, the “Anti-de-Sitter/conformal field theory correspondence”, or AdS/CFT. This links events within a contorted space-time geometry, such as in a black hole, with simpler physics at that space’s boundary.In 2004, Hawking used this to show how a black hole’s information leaks back into our universe through quantum-mechanical perturbations at its boundary, or event horizon. The

recantationcost Hawking a bet made with fellow theorist John Preskill a decade earlier.

Footer: Autoposted dengan [ email ] dari [ sunu’s posterous ]

* Catatan:* Pelajaran nyata yang bagus bagi para ilmuwan agar tidak merasa paling hebat dan sok pintar đ . Seorang sekaliber Stephen Hawking bahkan mau mengakui kebenaran relatif yang diajukan orang lain, bahkan dengan konsekuensi harus membatalkan (menarik kembali) argumentasinya yang terdahulu.

Itu sikap seorang ilmuwan hebat sekaliber Stephen Hawking. Siapa saya, siapa anda, siapa kita? Sudahkah kita diakui dunia internasional sehebat Stephen Hawking? Mari berpikir ulang đ

## What Exactly Is a Doctorate?

Ever wondered what getting a doctorate really means? Matt Might, professor of Computer Science at the University of Utah, explains it perfectly in this graphic presentation that starts with a simple circle.âJDEvery fall, I explain to a fresh batch of Ph.D. students what a Ph.D. is.

It’s hard to describe it in words.

So, I use pictures.

Read below for the illustrated guide to a Ph.D.

Imagine a circle that contains all of human knowledge:

By the time you finish elementary school, you know a little:

By the time you finish high school, you know a bit more:

With a bachelor’s degree, you gain a specialty:

A master’s degree deepens that specialty:

Reading research papers takes you to the edge of human knowledge:

Once you’re at the boundary, you focus:

You push at the boundary for a few years:

Until one day, the boundary gives way:

And, that dent you’ve made is called a Ph.D.:

Of course, the world looks different to you now:

So, don’t forget the bigger picture:

Click to view

Keep pushing.Matt Might is a professor of Computer Science at the University of Utah. He finished his dent at Georgia Tech in 2007, and now enjoys advising his own Ph.D. students on how to make theirs. He tweets from @mattmight and blogs at blog.might.net.

Footer: Autoposted dengan [ email ] dari [ sunu’s posterous ]

## Disc News Details: Mouse Virus Link to Fatigue Retracted

"The prominent journal Science on Thursday retracted a 2009 report linking a mouse retrovirus to chronic fatigue syndrome after it was disproved by researchers earlier this year."

http://m.discovery.com/s/4737/1932?itemPos=3&catIndex=

Footer: Autoposted dengan [ email ] dari [ sunu’s posterous ]

## Contributions to Science [an excerpt]

Classical Muslim scholars and scientists preserved, built upon, and translated classical Greek treatises.They also analyzed, collated, corrected, supplemented, and transferred classical Greek science and philosophy to Europe, thereby enabling its Renaissance. During Islam’s 200-year Golden Age, great Muslim scientists spread their knowledge through books.The first hospital was built in Damascus (707 CE) by Caliph Walid ibn ‘Abd al-Malik. Muslims made many advances, such as the idea of blood circulation and quarantine. Ibn Sina’s (d. 1037 CE) 20-volume The Book of Healing, consisting of The Canons of Medicine, was Europe’s chief medical science guide from the twelfth to the seventeenth century. Ibn Sina, the first to describe meningitis, surveyed all available medical knowledge, from ancient and Muslim sources, and made original contributions.

…

The founder of modern algebra, al-Khwarizmi’s (d. 850 CE) Calculating Integration and Equation was used until the sixteenth century as the principal textbook in European universities. He also helped introduce Arabic numerals, the decimal point system, and the concept of zero. Algebra and algorithm are corruptions of his work and name. Under al-Ma’mun, he and his colleagues were the first to map the globe. In algebra, the Muslims continued with Thabit Ibn Qurra’s more general equations solved by geometrical arguments. In 901 Abu Kamil, “the Egyptian calculator,” established rules for manipulating algebraic expressions. Around 1000, al-Karaji’s The Marvelous discussed higher order equations, combing geometry and arithmetic. Al-Samaw’al established the power law x^nx^n=x^(m+n) in 1180. Abu Yunus proved the famous identity cos(a)cos(b)={cos(a+b)+cos(a-b)}/2 and used spherical trigonometry to compute prayer times. Al-Biruni (d. 1050 CE) used spherical trigonometry to find any city’s direction. Another outstanding late-fourteenth century mathematician, Ghiyath al-Din al Kashani, worked on number theory and computation techniques. In 1424, he computed a value of 2pi to 16 decimal points. In his The Calculators’ Key, he described an algorithm for finding the fifth root of any number.

Omar Khayyam (d. 1131 CE), famous in the West as a poet, was an excellent mathematician who criticized Euclid’s theorems, evolved a methodology to solve thrid degree equations, and researched binomials and their coefficients. Methematician and atronomer al-Buzanji’s (d. 997 CE) main contribution lies in mathematics, especially geometry, and a sizable part of today’s trigonometry can be traced to him. Al-Battani (d. 929 CE) was a famous astronomer, mathematician, and astrologer who is often considered one of Islam’s greatest astronomers. He determined the solar year to be 365 days, 5 hours, 46 minutes, and 24 seconds – very close to modern estimates. He proved that, in contrast to Ptolemy, the sun’s variation of the apparent angular diameter and the possibility of annular eclipses. In 1749, Dunthorne used al-Battani’s observations of lunar and solar eclipses to determine the moon’s secular acceleration of motion. His most famous astonomical treatise, translated into Latin in the twelfth century, was extremely influential in Europe until the Renaissance.

…

Muslims discovered such new substances as potash, silver nitrate, corrosive sublimate, nitrate, and sulfuric acid, and improved methods for evaporation, filtration, sublimation, calcinations, melting, distillation, and crystallization.

…

Link to the full article.

## Science in Al-Andalus [an excerpt]

Another great area of Andalusian intellectual activity was philosophy, but it is impossible to do more than glance at this difficult and specialized study. From the ninth century, Andalusian scholars, like those in Baghdad, had to deal with the theological problems posed by the introduction of Greek philosophy into a context of Islam. How could reason be reconciled with revelation? This was the central question.

Ibn Hazm was one of the first to deal with this problem. He supported certain Aristotelian concepts with enthusiasm and rejected others. For example, he wrote a large and detailed commentary on Aristotle’s Posterior Analects, that abstruse work on logic. Interestingly, Ibn Hazm appears to have had no trouble relating logic to Islam—in fact, he gives illustrative examples of how it can be used in solving legal problems, drawn from the body of Islamic law. Nothing better illustrates the ability of Islam to assimilate foreign ideas and acclimatize them than Ibn Hazm’s words in the introduction to his work: “Let it be known that he who reads this book of ours will find that the usefulness of this kind of work is not limited to one single discipline but includes the Qur’an, hadith and legal decisions concerning what is permissible and what is not, and what is obligatory and what is lawful.”…

## SCIENCE AND SCHOLARSHIP IN AL-ANDALUS [an excerpt]

For Europe and Western civilization the contributions of Islamic Spain were of inestimable value. When the Muslims entered southern Spain – which they called al-Andalus – barbarians from the north had overrun much of Europe and the classical civilization of Greece and Rome had gone into eclipse. Islamic Spain then became a bridge by which the scientific, technological, and philosophical legacy of the ‘Abbasid period, along with the achievements of al-Andalus itself, passed into Europe.

…

‘Abd al-Rahman III was passionately interested in both the religious and the secular sciences. He was also determined to show the world that his court at Cordoba equaled in greatness that of the caliphs at Baghdad. Sparing neither time nor expense, he imported books from Baghdad and actively recruited scholars by offering hand some inducements. Soon, as a result, scholars, poets, philosophers, historians, and musicians began to migrate to al-Andalus. Soon, too, an infrastructure of libraries, hospitals, research institutions, and centers of Islamic studies grew up, establishing the intellectual tradition and educational system which made Spain outstanding for the next four hundred years.

One of the earliest of the scholars drawn to al-Andalus was ‘Abbas ibn Firnas, who came to Cordoba to teach music (then a branch of mathematical theory) and to acquaint the court of ‘Abd al-Rahman with the recent developments in this field in Baghdad. Not a man to limit himself to a single field of study, however, Ibn Firnas soon began to investigate the mechanics of flight.

He constructed a pair of wings out of feathers on a wooden frame and made the first attempt at flight, anticipating Leonardo da Vinci by some six hundred years.Later, having survived the experiment with a back injury, he also constructed a famous planetarium. Not only was it mechanized – the planets actually revolved – but it simulated such celestial phenomena as thunder and lightning.…

Click this link to continue reading