Sunday 26 February 2012

Bintang Neutron dan Teori String di dalam Laboratorium


“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.”

~ Albert Einstein~

Tired of the Endless Science Mysteries?

"No doubt you have noticed the ever-growing science mysteries: "Dark Matter", "Dark Energy", "Superstrings", "Hidden Dimensions", "Parallel Universes", "Quantum Paradoxes", "Relativistic Mysteries", "Time Travel", "Virtual Particles", multiple theories of gravity, frequent "anomalies" .. and the list goes on."
~The Final Theory~

-459 Fahrenheit

Hasil baru ini juga memberi wawasan eksperimental pada prediksi teori string, kontruksi matematis yang menyatukan dunia klasik gravitasi dengan fisika kuantum.

Dengan menggunakan laser yang mengandung beberapa atom ultra-dingin, sebuah tim ilmuwan mengukur viskositas (kekentalan) atau kerekatan dari gas yang sering dianggap sebagai keadaan keenam materi.

Pengukuran ini memverifikasi bahwa gas bisa digunakan sebagai “model skala” materi eksotis, seperti superkonduktor bersuhu super-tinggi, materi nuklir bintang neutron, dan bahkan keadaan mikrodetik materi yang tercipta setelah Big Bang.

Hasil ini juga memungkinkan pengujian eksperimental bagi teori string di masa depan.

Fisikawan Duke, John Thomas, melakukan pengukuran viskositas dengan menggunakan gas Fermi ultra-dingin dari atom lithium-6 yang terperangkap dalam mangkuk berukuran milimeter, yang tercipta dari sinar laser. Ketika didinginkan dan diletakkan di dalam medan magnet yang berukuran tepat, atom berinteraksi sama kuatnya dengan hukum mekanika kuantum. Gas yang berinteraksi sangat kuat ini menunjukkan “sifat yang luar biasa”, hampir seperti aliran fluida tanpa gesekan, kata Thomas.

Laporan tim ini muncul dalam Science edisi 10 Desember. Dalam kondisi ultra-dingin, sifat gas telah ditetapkan oleh pengatur universal, atau skala panjang alam, seperti skala pada gambar seorang arsitek. Pengatur untuk gas atom adalah jarak rata-rata di antara atom.

Menurut fisika kuantum, jarak ini menentukan semua skala alam lainnya, seperti skala untuk energi, temperatur dan viskositas, membuatkan gas ultra-dingin suatu model skala untuk hal eksotis lainnya. Thomas mengatakan bahwa ia dan yang lainnya telah memverifikasi gas sebagai model skala universal untuk sifat-sifat seperti temperatur, tapi ini adalah pertama kalinya mereka menguji skala untuk viskositas, yang kebetulan menjadi kepentingan tertentu bagi para ilmuwan saat ini.

Thomas pertama-tama mengukur viskositas gas pada beberapa milyar derajat Kelvin, atau -459 derajat Fahrenheit. Mematikan perangkap yang membatasi gas, dan kemudian menangkapnya kembali agar jari-jari gas Fermi bergetar. Osilasinya, yang disebut modus bernapas, menyerupai goyangan sepotong jelly.

Semakin lama getaran berlangsung, semakin rendah viskositasnya. Pada suhu yang sedikit lebih tinggi, sepersejuta derajat Kelvin, para peneliti mengamati seberapa cepat gas berubah dari bentuk cerutu hingga menjadi sepotong kue setelah dibebaskan dari perangkap. Perubahannya menjadi lebih lambat dalam bentuk yang tingkat kekentalan lebih tinggi.

Hasil ini “sangat penting khususnya untuk bidang fisika materi terkondensasi dan superkonduktivitas bertemperatur tinggi,” kata Kathy Levin, seorang ahli teori di Universitas Chicago, yang tidak terlibat dalam penelitian ini.

Dia mengatakan bahwa viskositas gas Fermi mirip dengan konduktivitas suatu superfluida, yang mengalir dengan tanpa resisten. “Fluiditas sempurna” ini juga terobservasi dalam dunia materi terkondensasi, terutama pada material yang digunakan untuk membuat superkonduktor bertemperatur tinggi.

Data baru, terutama pada temperatur rendah, “tampaknya cukup konsisten” dengan prediksi tentang bagaimana superkonduktor seharusnya mengalir, kata Levin.

Gas Fermi yang digunakan sebagai model skala ini juga penting untuk mempelajari elemen alam semesta di mana para ilmuwan tidak dapat menyelidikinya di dalam laboratorium, kata fisikawan Duke, Berndt Mueller. Bahkan, potongan bintang neutron yang sangat kecil, bintang mati yang belum menjadi lubang hitam, akan seberat miliaran ton di Bumi dan terlalu padat untuk dipelajari.

Bagaimanapun juga, data yang menunjukkan sifat universal gas Fermi memungkinkan para fisikawan menghitung skalanya dari atom lithium-6 jarak demi jarak di antara neutron dalam bintang-bintang ini. Pengukuran yang dilakukan pada gas Fermi kemudian dapat digunakan untuk menentukan energi alam beserta sifat-sifat lainnya pada bintang-bintang ini, yang dapat dibandingkan dengan berbagai prediksi teori.

Perhitungan serupa bisa dilakukan pada plasma quark-gluon, keadaan materi yang tercipta hanya mikrodetik setelah Big Bang dan kini sedang dipelajari di akselerator partikel seperti Large Hadron Collider di Jenewa.

Thomas mengatakan bahwa hasil baru ini juga memberi wawasan eksperimental pada prediksi yang dibuat dengan menggunakan teori string, kontruksi matematis yang menyatukan dunia klasik gravitasi dengan fisika kuantum.

Teori string telah memberikan batas bawah bagi rasio viskositas atau aliran fluida ke entropi, atau disorder, dalam sebuah sistem yang berinteraksi kuat. Percobaan terbaru ini mengukur sifat-sifat pada gas Fermi dan menunjukkan bahwa gas minimum adalah di antara empat dan lima kali batas bawah teoretisi string.

“Pengukuran ini tidak menguji teori string secara langsung,” kata Thomas, mencatat beberapa peringatan – batas bawah diperoleh untuk sistem energi tinggi, di mana teori relativitas Einstein sangatlah penting, sedangkan eksperimen gas Fermi mempelajari gas rendah energi.

Jika teori string membuat perhitungan baru yang khusus untuk gas Fermi, maka para ilmuwan akan mampu membuat pengujian eksperimental yang tepat pada teori tersebut dengan peralatan yang tidak lebih besar dari sebuah desktop.

Sumber artikel: Fahrenheit -459: Neutron Stars and String Theory in a Lab
(dukenews.duke.edu)

Kredit: Duke University

Informasi lebih lanjut: C. Cao, E. Elliott, J. Joseph, H. Wu, J. Petricka, T. Schäfer, and J. E. Thomas. Universal Quantum Viscosity in a Unitary Fermi Gas. Science, 2010; DOI: 10.1126/science.1195219

Sumber: Fisika Net

1. http://superstringtheory.com/
2. http://www.theoryofeverything.net/

Friday 24 February 2012

Neutron Star Subtypes

Sumber; Wikipedia

Wednesday 22 February 2012

Binary Neutron Stars

About 5% of all known neutron stars are members of a binary system. The formation and evolution scenario of binary neutron stars is a rather exotic and complicated process.

The companion stars may be either ordinary starswhite dwarfs or other neutron stars. According to modern theories of binary evolution it is expected that neutron stars also exist in binary systems with black hole companions. 

Such binaries are expected to be prime sources for emittinggravitational waves. Neutron stars in binary systems often emit X-rays which is caused by the heating of material (gas) accreted from the companion star. 

Material from the outer layers of a (bloated) companion star is sucked towards the neutron star as a result of its very strong gravitational field. 

As a result of this process binary neutron stars may also coalesce into black holes if the accretion of mass takes place under extreme conditions.

It has been proposed that coalescence of binaries consisting of two neutron stars may be responsible for producing short gamma-ray bursts. Such events may also be responsible for creating all chemical elements beyond iron, as opposed to thesupernova nucleosynthesis theory.

Sumber:

Wikipedia

Monday 20 February 2012

Mengenal Bintang Neutron

neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type IIType Ib or Type Ic supernova event. 

Such stars are composed almost entirely of neutrons, which are subatomic particles without net electrical charge and with slightly larger mass than protons. Neutron stars are very hot and are supported against further collapse by quantum degeneracy pressure due to the phenomenon described by the Pauli exclusion principle
This principle states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously.
A typical neutron star has a mass between about 1.4 and 3.2 solar masses (see Chandrasekhar Limit), with a corresponding radius of about 12 km.

In contrast, theSun's radius is about 60,000 times that. Neutron stars have overall densities of 3.7×1017 to 5.9×1017 kg/m3 (2.6×1014 to 4.1×1014 times the density of the Sun), which compares with the approximate density of an atomic nucleus of 3×1017 kg/m3

The neutron star's density varies from below 1×109 kg/m3 in the crust, increasing with depth to above 6×1017 or 8×1017 kg/m3 deeper inside (denser than an atomic nucleus). This density is approximately equivalent to the mass of a Boeing 747 compressed to the size of a small grain of sand.

In general, compact stars of less than 1.44 solar masses – the Chandrasekhar limit – are white dwarfs, and above 2 to 3 solar masses (the Tolman–Oppenheimer–Volkoff limit), aquark star might be created; however, this is uncertain. Gravitational collapse will usually occur on any compact star between 10 and 25 solar masses and produce a black hole.

Some neutron stars rotate very rapidly and emit beams of electromagnetic radiation as pulsars.

Sumber:

Wikipedia

Friday 17 February 2012

Kebijakan Pembangunan Sciences

Science policy is an area of public policy concerned with the policies that affect the conduct of the scientific enterprise, including research funding, often in pursuance of other national policy goals such as technological innovation to promote commercial product development, weapons development, health care and environmental monitoring. 

Science policy also refers to the act of applying scientific knowledge and consensus to the development of public policies. Science policy thus deals with the entire domain of issues that involve the natural sciences.

In accordance with public policy being concerned about the well-being of its citizens, science policy's goal is to consider how science and technology can best serve the public.

State policy has influenced the funding of public works and science for thousands of years, dating at least from the time of the Mohists, who inspired the study of logic during the period of the Hundred Schools of Thought, and the study of defensive fortifications during the Warring States period in China. 

In Great Britain, governmental approval of the Royal Society in the 17th century recognized a scientific community which exists to this day.

The professionalization of science, begun in the 19th century, was partly enabled by the creation of scientific organizations such as the National Academy of Sciences, the Kaiser Wilhelm Institute, and State funding of universities of their respective nations. 

Public policy can directly affect the funding of capital equipment, intellectual infrastructure for industrial research, by providing tax incentives to those organizations that fund research. 

Vannevar Bush, director of the office of scientific research and development for the United States government, the forerunner of the National Science Foundation, wrote in July 1945 that "Science is a proper concern of government" 

Science and technology research is often funded through a competitive process, in which potential research projects are evaluated and only the most promising receive funding. 

Such processes, which are run by government, corporations or foundations, allocate scarce funds.

Total research funding in most developed countries is between 1.5% and 3% of GDP.

In the OECD, around two-thirds of research and development in scientific and technical fields is carried out by industry, and 20% and 10% respectively by universities and government. 

The government funding proportion in certain industries is higher, and it dominates research in social science and humanities. 

Similarly, with some exceptions (e.g. biotechnology) government provides the bulk of the funds for basic scientific research. In commercial research and development, all but the most research-oriented corporations focus more heavily on near-term commercialisation possibilities rather than "blue-sky" ideas or technologies (such as nuclear fusion).

Sumber:

Wikipedia

Wednesday 15 February 2012

Certainty and Science

A scientific theory is empirical, and is always open to falsification if new evidence is presented. That is, no theory is ever considered strictly certain as science accepts the concept of fallibilism. 

The philosopher of science Karl Popper sharply distinguishes truth from certainty. He writes that scientific knowledge "consists in the search for truth", but it "is not the search for certainty ... All human knowledge is fallible and therefore uncertain."

New scientific knowledge rarely results in vast changes in our understanding. 

According to psychologist Keith Stanovich, it may be the media's overuse of words like "breakthrough" that leads the public to imagine that science is constantly proving everything it thought was true to be false.

While there are such famous cases as the theory of relativity that required a complete reconceptualization, these are extreme exceptions. 

Knowledge in science is gained by a gradual synthesis of information from different experiments, by various researchers, across different branches of science; it is more like a climb than a leap.

Theories vary in the extent to which they have been tested and verified, as well as their acceptance in the scientific community.

For example, heliocentric theory, the theory of evolution, relativity theory, and germ theory still bear the name "theory" even though, in practice, they are considered factual.

Philosopher Barry Stroud adds that, although the best definition for "knowledge" is contested, being skeptical and entertaining the possibility that one is incorrect is compatible with being correct. 

Ironically then, the scientist adhering to proper scientific approaches will doubt themselves even once they possess the truth.

The fallibilist C. S. Peirce argued that inquiry is the struggle to resolve actual doubt and that merely quarrelsome, verbal, or hyperbolic doubt is fruitless but also that the inquirer should try to attain genuine doubt rather than resting uncritically on common sense.

He held that the successful sciences trust, not to any single chain of inference (no stronger than its weakest link), but to the cable of multiple and various arguments intimately connected.

Stanovich also asserts that science avoids searching for a "magic bullet"; it avoids the single-cause fallacy. This means a scientist would not ask merely "What is the cause of ...", but rather "What are the most significant causes of ...". This is especially the case in the more macroscopic fields of science (e.g. psychology, cosmology).

Of course, research often analyzes few factors at once, but these are always added to the long list of factors that are most important to consider.

For example: knowing the details of only a person's genetics, or their history and upbringing, or the current situation may not explain a behaviour, but a deep understanding of all these variables combined can be very predictive.

Sumber:

Wikipedia

Friday 10 February 2012

Falsafah Ilmu Pengetahuan Alam Lebih Lanjut

Another approach, instrumentalism, colloquially termed "shut up and calculate", emphasizes the utility of theories as instruments for explaining and predicting phenomena.

It claims that scientific theories are black boxes with only their input (initial conditions) and output (predictions) being relevant. Consequences, notions and logical structure of the theories are claimed to be something that should simply be ignored and that scientists shouldn't make a fuss about (see interpretations of quantum mechanics). 

Close to instrumentalism is Constructivist epistemology according to which the main task of science is constructing models that can be given input and will give you an output that will predict the output given by the reality under same conditions accurately and validly enough.

Paul K Feyerabend advanced the idea of epistemological anarchism, which holds that there are no useful and exception-free methodological rules governing the progress of science or the growth of knowledge, and that the idea that science can or should operate according to universal and fixed rules is unrealistic, pernicious and detrimental to science itself.

Feyerabend advocates treating science as an ideology alongside others such as religion, magic and mythology, and considers the dominance of science in society authoritarian and unjustified. 

He also contended (along with Imre Lakatos) that the demarcation problem of distinguishing science from pseudoscience on objective grounds is not possible and thus fatal to the notion of science running according to fixed, universal rules.

Feyerabend also stated that science does not have evidence for its philosophical precepts, particularly the notion of Uniformity of Law and the Uniformity of Process across time and space.

Finally, another approach often cited in debates of scientific skepticism against controversial movements like "scientific creationism", is methodological naturalism. Its main point is that a difference between natural and supernatural explanations should be made, and that science should be restricted methodologically to natural explanations.

That the restriction is merely methodological (rather than ontological) means that science should not consider supernatural explanations itself, but should not claim them to be wrong either. Instead, supernatural explanations should be left a matter of personal belief outside the scope of science. 

Methodological naturalism maintains that proper science requires strict adherence to empirical study and independent verification as a process for properly developing and evaluating explanations for observable phenomena.

The absence of these standards, arguments from authority, biased observational studies and other common fallacies are frequently cited by supporters of methodological naturalism as criteria for the dubious claims they criticize not to be true science.

Sumber:

Wikipedia

Monday 6 February 2012

Falsafah Ilmu Pengetahuan Alam

Working scientists usually take for granted a set of basic assumptions that are needed to justify the scientific method:

(1) that there is an objective reality shared by all rational observers;

(2) that this objective reality is governed by natural laws; 

(3) that these laws can be discovered by means of systematic observation and experimentation. 

Philosophy of science seeks a deep understanding of what these underlying assumptions mean and whether they are valid.

The belief that all observers share a common reality is known as realism. It can be contrasted with anti-realism, the belief that there is no valid concept of absolute truth such that things that are true for one observer are true for all observers. 

The most commonly defended form of anti-realism is idealism, the belief that the mind or consciousness is the most basic essence, and that each mind generates its own reality.

In an idealistic world-view, what is true for one mind need not be true for other minds.

There are different schools of thought in philosophy of science. 

The most popular position is empiricism, which claims that knowledge is created by a process involving observation and that scientific theories are the result of generalizations from such observations.

Empiricism generally encompasses inductivism, a position that tries to explain the way general theories can be justified by the finite number of observations humans can make and the hence finite amount of empirical evidence available to confirm scientific theories. 

This is necessary because the number of predictions those theories make is infinite, which means that they cannot be known from the finite amount of evidence using deductive logic only. Many versions of empiricism exist, with the predominant ones being bayesianism and the hypothetico-deductive method.

Empiricism has stood in contrast to rationalism, the position originally associated with Descartes, which holds that knowledge is created by the human intellect, not by observation.

A significant 20th-century version of rationalism is critical rationalism, first defined by Austrian-British philosopher Karl Popper. 

Popper rejected the way that empiricism describes the connection between theory and observation.

He claimed that theories are not generated by observation, but that observation is made in the light of theories and that the only way a theory can be affected by observation is when it comes in conflict with it.

Popper proposed falsifiability as the landmark of scientific theories, and falsification as the empirical method, to replace verifiability and induction by purely deductive notions.

Popper further claimed that there is actually only one universal method, and that this method is not specific to science: The negative method of criticism, trial and error.

It covers all products of the human mind, including science, mathematics, philosophy, and art.

Sumber:

Wikipedia

Friday 3 February 2012

Memahami Pendidikan Sains

Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.

In an older and closely related meaning, "science" also refers to a body of knowledge itself, of the type that can be rationally explained and reliably applied. A practitioner of science is known as a scientist.

Since classical antiquity, science as a type of knowledge has been closely linked to philosophy. In the early modern period the words "science" and "philosophy of nature" were sometimes used interchangeably.

By the 17th century, natural philosophy (which is today called "natural science") was considered a separate branch of philosophy.

In modern usage, "science" most often refers to a way of pursuing knowledge, not only the knowledge itself. It is also often restricted to those branches of study that seek to explain the phenomena of the material universe.

In the 17th and 18th centuries scientists increasingly sought to formulate knowledge in terms of laws of nature such as Newton's laws of motion. And over the course of the 19th century, the word "science" became increasingly associated with the scientific method itself, as a disciplined way to study the natural world, including physics, chemistry, geology and biology. It is in the 19th century also that the term scientist was created by the naturalist-theologian William Whewell to distinguish those who sought knowledge on nature from those who sought other types of knowledge.

However, "science" has also continued to be used in a broad sense denoting reliable, teachable knowledge about a topic, as in modern terms like library science or computer science. 

This is also reflected in the names of some areas of academic study such as "social science" or "political science".

Sumber:

Wikipedia

Wednesday 1 February 2012

Can Science Save the World?


"The world spends nearly $7 trillion a year on energy and its infrastructure"

By: Prof. Martin John Rees, Ph.D.
http://www.ast.cam.ac.uk/~mjr/
Master of the University of Cambridge, and Professor of Cosmology and Astrophysics.


CAMBRIDGE – For most people, there has never been a better time to be alive than now. The innovations that drive economic advances – information technology, biotech, and nanotech – can boost living standards in both the developing and the developed world. We are becoming embedded in a cyberspace that can link anyone, anywhere, to all the world’s information and culture – and to every other person on the planet.

Twenty-first century technologies will offer environmentally benign lifestyles and the resources to ease the plight and enhance the life chances of the world’s two billion poorest people. Moreover, the greatest threat of the 1960’s and 1970’s – nuclear annihilation – has diminished. This threat could recur, however, if there is a renewed standoff between new superpowers. And there are other risks stemming from humanity’s greater collective impact on the planet, and from the growing empowerment of individuals.

Soon after World War II, physicists at the University of Chicago started a journal called the Bulletin of Atomic Scientists to promote arms control. The logo on the Bulletin’s cover is a clock, the proximity of whose hands to midnight indicates the editors’ judgment of the precariousness of the world situation. Every few years, the minute hand shifted, either forwards or backwards. It came closest to midnight in 1962 during the Cuban Missile Crisis.

When the Cold War ended, the Bulletin’s clock was put back to 17 minutes to midnight. But the clock has been creeping forward again. We are confronted by proliferation of nuclear weapons (by, say, North Korea and Iran). Al-Qaeda-style terrorists might willingly detonate a nuclear weapon in a city center, killing tens of thousands.

Even if the nuclear threat is contained, the twenty-first century could confront us with grave new global perils. Climate change looms as this century’s primary long-term environmental challenge. Human actions – burning fossil fuels – have already raised the carbon dioxide concentration higher than it has ever been in the last 500,000 years, and it is rising by about 0.5 % a year.

More disturbingly, coal, oil, and gas are projected to supply most of the world’s growing energy needs for decades to come. If that continues, the concentration of CO2 will rise to twice the pre-industrial level by 2050, and three times that level later in the century.

The world spends nearly $7 trillion a year on energy and its infrastructure; yet our current research and development efforts are not up to meeting the challenge of climate change. There is no single solution, but some measures, like better insulation of buildings, would save rather than cost money.

Efforts to economize on energy, storing it, and generating it by “clean” or low-carbon methods deserve priority and the sort of commitment from governments that were accorded to the Manhattan Project (which created the atomic bomb) or the Apollo moon landing.

The top priority should be a coordinated effort by Europe, the United States, and the other G-8+5 countries to build demonstration plants to develop carbon capture and storage (CCS) technology. This is crucial, because whatever technical advances there may be in solar and other renewable energy sources, we will depend on coal and oil for the next 40 years. Yet unless the rising curve of annual emissions can be reversed, the CO2 concentration will irrevocably reach a truly threatening level.

Mankind must also confront other global “threats without enemies” that are separate from (though linked with) climate change. Loss of biological diversity is one of the most severe such threats. The extinction rate is 1,000 times higher than normal, and is increasing.

Biodiversity is a crucial component of human well-being and economic growth. We are clearly harmed if fish stocks dwindle to extinction. Less evidently, there are plants in the rain forest whose gene pool might be useful to us.

The pressures on our planet depend, of course, on our lifestyle. The world could not sustain its 6.5 billion people if they all lived like present-day Americans. But it could if even prosperous people adopted a vegetarian diet, traveled little, and interacted virtually. New technology will determine our lifestyle, and the demands that we make on energy and environmental resources.

Nevertheless, our problems are aggravated by rapid growth in the human population, which is projected to reach eight or even nine billion by 2050. If the increase continues beyond 2050, one cannot help but be gloomy about most people’s prospects.

There are now, however, more than 60 countries where the fertility rate is below replacement level. If this were true of all countries, the global population would start to decline after 2050 – a development that would surely be benign.

All of today’s developments – cyber, bio, or nano – will create new risks of abuse. The American National Academy of Sciences has warned that, “Just a few individuals with specialized skills…could inexpensively and easily produce a panoply of lethal biological weapons.…The deciphering of the human genome sequence and the complete elucidation of numerous pathogen genomes…allow science to be misused to create new agents of mass destruction.”

Not even an organized network would be required; just a fanatic with the mindset of those who now design computer viruses. The global village will have its village idiots.

In our increasingly interconnected world, there are new risks whose consequences could be widespread – and perhaps global. Even a tiny probability of global catastrophe is unacceptable. If we apply to catastrophic risks the same prudent analysis that leads us to buy insurance – multiplying probability by consequences – we would surely prioritize measures to reduce this kind of extreme risk. The decisions that we will make both individually and collectively in the foreseeable future will determine whether twenty-first century science yields benign or devastating outcomes.

By:
Lord Rees is Britain’s Astronomer Royal, President of the Royal Society, Master of the University of Cambridge’s Trinity College, and Professor of Cosmology and Astrophysics.

Copyright: Project Syndicate/Europe’s World, 2008.

http://www.project-syndicate.org/

http://www.europesworld.org/