John C. Mather and George F. Smoot

Nobel Fisika 2006: Penjelasan Kelahiran Alam Semesta

Hadiah Nobel Fisika 2006 ini jatuh kepada dua astrofisikawan eksperimen berkebangsaan Amerika, John C Mather dan George F Smoot, untuk jasa mereka dalam mengukur secara akurat radiasi latar belakang kosmik (cosmic microwave background atau CMB).

John C Mather adalah peneliti senior pada Divisi Sains Astrofisika NASA, berusia 60 tahun, sedangkan George F Smoot adalah profesor fisika di Universitas California Berkeley. Penemuan spektakuler mereka dipublikasikan pada jurnal Astrophysics tahun 1990 dan 1992.

Penemuan yang dilakukan melalui satelit COBE ini semakin mengukuhkan teori Big Bang yang menyatakan bahwa alam semesta berawal dari suatu ledakan.

Cukup mencengangkan jika kita tahu bahwa CMB ditemukan secara tidak sengaja oleh dua fisikawan instrumen. Adalah Arno Penzias dan Robert Wilson yang berjasa menemukan CMB pertama kali pada tahun 1964 dalam bentuk derau (noise) radio yang pada saat itu sangat membingungkan mereka.

Kedua ilmuwan tersebut bekerja di laboratorium Bell di New Jersey dengan sebuah teleskop radio ultrasensitif (saat itu) yang dirancang untuk menerima sinyal dari satelit. Teleskop tadi menangkap derau yang berasal jauh dari luar angkasa dan, yang paling membingungkan kedua ilmuwan, sinyal tersebut tidak bergantung pada arah fokus teleskop serta tidak bergantung pada waktu pengamatan.

Pengukuran yang mereka lakukan mengantar pada kesimpulan bahwa derau tersebut adalah radiasi gelombang mikro dengan panjang gelombang 7 sentimeter yang merupakan fosil ledakan Big Bang. Untuk penemuan yang sangat menghebohkan ini, Penzias dan Wilson dianugerahi hadiah Nobel pada tahun 1978.

Dari sifat isotropiknya wajar jika diyakini bahwa radiasi CMB berasal dari tempat yang sangat jauh di jagat raya. Namun, bagaimana para ilmuwan dapat yakin bahwa radiasi ini merupakan fosil dari ledakan mahadahsyat di masa lampau saat alam semesta tercipta?

Lebih dari 20 tahun sebelum penemuan CMB, George Gamow, seorang profesor fisika pada George Washington University di Washington DC, bersama dengan mahasiswanya mengusulkan teori penciptaan alam semesta melalui ledakan sangat dahsyat yang mereka sebut teori Big Bang.

Dua mahasiswanya, Ralph Alpher dan Robert Herman, pada tahun 1949 memperkirakan bahwa temperatur rata-rata alam semesta saat ini sebagai konsekuensi dari ledakan besar di masa lalu serta berkembangnya alam semesta pada kisaran 5 derajat Kelvin (minus 268 derajat Celsius).

Sayangnya, mereka tidak sempat mengusulkan eksperimen dengan menggunakan teleskop radio.

Menariknya, hubungan antara derau statik gelombang mikro dan temperatur alam semesta merupakan kisah sukses fisika selain mekanika kuantum dan relativistik.

Di dalam termodinamika, salah satu cabang fisika yang banyak membahas hubungan antara temperatur dan sifat suatu zat, dikenal hukum Wien yang menyatakan bahwa untuk distribusi radiasi benda hitam perkalian antara panjang gelombang radiasi berintensitas maksimum dan temperaturnya ekuivalen dengan bilangan 0,3.

Pengukuran yang dilakukan oleh Penzias dan Wilson tidak persis tepat pada puncak distribusi. Namun, karena kegigihan dan keyakinan para ilmuwan, pengukuran-pengukuran yang dilakukan selama lebih dari dua dekade, hingga tahun 1991 dengan menggunakan satelit COBE, berhasil mengonfirmasi distribusi radiasi benda hitam dari CMB dengan akurasi yang sangat mengesankan (lihat gambar 1). Dari distribusi tersebut diperoleh kesimpulan bahwa temperatur alam semesta saat ini, lebih dari 10 miliar tahun setelah Big Bang, adalah 2,726 Kelvin.


Superakurat

Satelit COBE yang menghasilkan pengukuran superakurat, seperti terlihat pada gambar 1, sebenarnya dirancang juga untuk eksperimen lain, yaitu pengukuran variasi temperatur CMB pada arah-arah berbeda.

Secara teoretis, variasi yang sangat kecil pun dapat memberi petunjuk bagaimana galaksi dan bintang-bintang mulai terbentuk. Pertanyaan dasarnya adalah mengapa hanya di tempat-tempat tertentu di jagat raya materi menggumpal dan, dengan bantuan gravitasi, melahirkan galaksi.

Penjelasan teoretis proses ini menyangkut masalah fluktuasi mekanika kuantum yang terjadi sesaat setelah jagat raya mulai berkembang. Saat satelit COBE dirancang, diperkirakan variasi temperatur yang diperlukan untuk menjelaskan halini berkisar seperseribu derajat Celsius.

Akan tetapi, beberapa saat kemudian para ilmuwan menemukan "materi gelap" (dark matter) yang juga dapat memengaruhi variasi temperatur pada orde seperseratus ribu derajat.

Secara teoretis, materi gelap ini merupakan agen penting pada proses akumulasi materi, dengan kata lain untuk menjawab pertanyaan dasar tadi instrumen pada COBE harus dirancang ulang lebih presisi.

Meski hasil yang lebih akurat diberikan oleh pengukuran berikutnya yang dinamakan Wilkinson Microwave Anisotropy Probe (WMAP), penelitian yang dipimpin oleh George F Smoot berhasil membuktikan adanya variasi temperatur bahkan pada orde puluhan mikro Kelvin .

Selain berhasil mengukuhkan teori Big Bang, kedua hasil pengukuran pemenang Nobel Fisika tahun ini memperlihatkan bahwa kosmologi bukan lagi merupakan spekulasi filosopis seperti sebelumnya.

Untuk pertama kalinya perhitungan-perhitungan kosmologi dapat dibandingkan dengan data eksperimen yang sangat akurat. Kosmologi modern disebut-sebut sebagai "precision science".

Hasil yang diperoleh COBE dan WMAP juga mengantarkan kita ke informasi tentang bentuk dasar jagat raya yang disebut Euclidian, atau, dalam bahasa awam, intuisi kita yang menyatakan bahwa dua garis lurus paralel tidak akan saling memotong tampaknya juga berlaku untuk skala jagat raya.

Terry Mart
Fisikawan UI; Saat Ini Menjadi Peneliti Tamu di Institut fuer Kernphysik, Universitaet Mainz, Jerman

Sumber: http://www.kompas.com/kompas-cetak/0610/12/iptek/3021422.htm
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NASA Scientist Shares Nobel Prize for Physics

Dr. John C. Mather of NASA's Goddard Space Flight Center has won the 2006 Nobel Prize for Physics, awarded by the Royal Swedish Academy of Sciences. Mather shares the prize with George F. Smoot of the University of California for their collaborative work on understanding the Big Bang.

Image Left: NASA Scientist Dr. John C. Mather shows some of the earliest data from the NASA Cosmic Background Explorer (COBE) Satellite during a press conference held at NASA Headquarters in Washington, DC. Dr. Mather was co-recipient of the 2006 Nobel Prize for Physics today October 3, 2006. Photo Credit: NASA/Bill Ingalls

+ More Press Conference Photos

Mather and Smoot analyzed data from NASA's Cosmic Background Explorer (COBE), which studied the pattern of radiation from the first few instants after the universe was formed. In 1992, the COBE team announced that they had mapped the primordial hot and cold spots in the cosmic microwave background radiation. These spots are related to the gravitational field in the early universe, only instants after the Big Bang, and are the seeds for the giant clusters of galaxies that stretch hundreds of millions of light years across the universe.

NASA Administrator Michael Griffin had this to say, "I am thrilled to hear that Dr. John Mather has been selected to receive the Nobel Prize in Physics. John would be a world-class scientist no matter where he had chosen to spend his career, but we at NASA are enormously proud that he has chosen to spend it with us."

Image right: Dr. Mather (far left) and his colleagues, (counterclockwise) Al Kogut, Gary Hinshaw, and Dr. Chuck Bennett. Click image to enlarge. Credit: NASA

The team also showed that the big bang radiation has a spectrum that agrees exactly with the theoretical prediction, confirming the Big Bang theory and showing that the Big Bang was complete in the first instants, with only a tiny fraction of the energy released later.

Biography of John C. Mather

Educational Background:

B.A., Physics, Swarthmore College (Highest Honors, Phi Beta Kappa), 1968
Ph.D., Physics, University of California at Berkeley (4.0 GPA), 1974

Brief Bio:

Dr. Mather joined the Goddard Space Flight Center in Greenbelt, Maryland to head the Cosmic Background Explorer (COBE) Mission as Project Scientist. He has been a Goddard Fellow since 1994 and currently serves as Senior Project Scientist and Chair of the Science Working Group of the James Webb Space Telescope (JWST) Mission. He is also working on the SAFIR , SPECS, GEST, and WISE missions. Dr. Mather's numerous awards include the John C. Lindsay Memorial Award, National Air and Space Museum Trophy, AIAA Space Science Award, Aviation Week and Space Technology Laurels for Space/Missiles, Dannie Heinemann Prize for Astrophysics, Rumford Prize, the Benjamin Franklin Medal in Physics, and membership in the National Academy of Sciences. He has been elected to the American Astronomical Society Council.

Image left: Dr. Mather (kneeling) examines the map of the universe along with Nancy Boggess, Michael Hauser (sitting), and Dr. Chuck Bennett (standing). Click image to enlarge. Credit: NASA

Research Interests:

Research interests include cosmology, far infrared astronomy and instrumentation, and Fourier transform spectroscopy.



Related Links:

+ Royal Academy Press Release
+ Spotlight on Dr. Mather
+ Photo Gallery from Press Conference on Oct. 3
+ Background on the Cosmic Background Explorer and the Big Bang theory
+ Gruber Cosmology Prize
+ COBE Archive website
+ Images of COBE
+ COBE's view of the Milky Way
+ NASA and COBE Scientists Win Top Cosmology Prize

Selected Publications:

J.C. Mather and J. Boslough, "The Very First Light," Basic Books, New York, 1996.

A. Kashlinsky, J.C. Mather, S. Odenwald, M.G. Hauser, "Clustering of the Diffuse Infrared Light from the COBE DIRBE maps, I. C (O) and limits on the near-IR background," Astrophysical Journal, 470, 681, 1996.

D.J. Fixsen, E.S. Cheng, J.M. Gales, J.C. Mather, R.A. Shafer, and E.L. Wright, "The Cosmic Microwave Background Spectrum from the Full COBE FIRAS Data Set," Astrophysical Journal, 473, 576, 1996.

R.A. Shafer, J.C. Mather, D.J. Fixen, K.A. Jensen, W.T. Reach, E. Dwek, and E.S. Cheng, "The Far Infrared Background as Measured by COBE FIRAS I: Limits from Dark Sky Measurements," Astrophysical Journal, 470, 681, 1996.

N.N. Gor’kavyi, L.M. Ozernoy, and J.C. Mather, "A New approach to Dynamical Evolution of Interplanetary Dust," Astrophysical Journal, 474, 496, 1996.

A. Kashlinsky, J.C. Mather, S. Odenwald, "Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. II. An All-sky Survey of C(0), Astrophysical Journal, 473L, 9, 1996.

D.J. Fixsen, G. Hinshaw, C.L. Bennett, J.C. Mather, "The Spectrum of the CMB Anisotropy from the Combined COBE FIRAS and DMR Observations," Astrophysical Journal, 486, 1997.

D.J. Fixsen, J.L. Weiland, S. Brodd, M.G. Hauser, T. Kelsall, D.T. Leisawitz, J.C. Mather, K.A. Jensen, R.A. Shafer, and R.F. Silverberg, "The Comparison of the FIRAS and DIRBE Data from COBE,", Astrophysical Journal, submitted May 1997.

http://www.nasa.gov/vision/universe/starsgalaxies/nobel_prize_mather.html
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Americans John C. Mather and George F. Smoot win the Nobel Prize in physics

By Dan Vergano, USA TODAY

Flickers spotted in the afterglow of the big bang led two American scientists to the Nobel Prize in physics Tuesday.

The Royal Swedish Academy of Sciences awarded the $1.365 million prize to George Smoot of the University of California-Berkeley and John Mather of NASA's Goddard Space Flight Center for the discovery of small temperature variations in the "cosmic microwave background" that fills space.

The prize goes for a 1992 discovery by NASA's Cosmic Background Explorer (COBE) satellite team that opened a new era of precise measurements of the first moments of the universe.

AUDIO: Dan Vergano explains Mather and Smoot's work

Smoot and Mather "have really helped us to find the missing link in cosmology," said physicist Per Carlsson of the Royal Institute of Technology at Tuesday's announcement in Stockholm.

The cosmic microwave background emanates from every point in the sky. It is the cooled remains of the first light visible in the aftermath of the universe's origin as a rapidly expanding ball of energy about 13.7 billion years ago, the so-called big bang.

Tiny variations in this cosmic background correspond to minute clumpings of matter in the expanding universe. Smoot and Mather's discovery demonstrated how the universe of today — filled with islands of stars called galaxies and separated by vast empty pockets of space — could coalesce from these matter clusters.

"Effectively, these are baby pictures of the universe," says physicist Max Tegmark of the Massachusetts Institute of Technology. A lot of people thought COBE would be a failure and to (the prize-winners') credit, they kept going."

Says physicist Lawrence Krauss of Case Western Reserve University in Cleveland, "(The COBE mission) worked exactly the way they said it would, and that's why they deserve the prize."

The pair will receive the prize from King Carl Gustav XVI on Dec. 10. Mather is the first NASA employee to win for work performed at a NASA research center.

"The COBE results provided increased support for the Big Bang scenario for the origin of the Universe, as this is the only scenario that predicts the kind of cosmic microwave background radiation measured by COBE," the Royal Swedish Academy of Sciences in Stockholm said in its citation.

Reached at his home in Berkeley, Smoot, 61, told The Associated Press he was surprised when he got the call from the Nobel committee in the middle of the night.

"I was surprised that they even knew my number. After the discovery I got so many calls I unlisted it," he said.

"The discovery was sort of fabulous. It was an incredible milestone. Now this is a great honor and recognition. It's amazing," he said.

Mather, 60, said to the AP he was "thrilled and amazed" at receiving the prize.

"I can't say I was completely surprised, because people have said we should be awarded, but this is just such a rare and special honor," Mather said in a telephone interview with the Nobel committee.

He said he and Smoot did not realize how important their work was at the time of their discovery.

The academy called Mather the driving force behind the COBE project while Smoot was responsible for measuring small variations in the temperature of the radiation.

"The very detailed observations that the laureates have carried out from the COBE satellite have played a major role in the development of modern cosmology into a precise science," the academy said.

"They have not proven the big bang theory but they give it very strong support," said Per Carlson, chairman of the Nobel committee for physics.

"It is one of the greatest discoveries of the century. I would call it the greatest. It increases our knowledge of our place in the universe."

Since 1986, Americans have either won or shared the physics prize with people from other countries 15 times.

Last year, Americans John L. Hall and Roy J. Glauber and German Theodor W. Haensch won the prize for work that could improve long-distance communication and navigation.

This year's award announcements began Monday with the Nobel Prize in medicine going to Americans Andrew Z. Fire and Craig C. Mello for discovering a powerful way to turn off the effect of specific genes, offering new hope for fighting diseases as diverse as cancer and AIDS.

The winner of the Nobel Prize in chemistry will be named Wednesday. The Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel will be announced Oct. 9.

The winner of the peace prize — the only one not awarded in Sweden — will be announced Oct. 13 in Oslo.

A date for the literature prize has not yet been set.

Alfred Nobel, the wealthy Swedish industrialist and inventor of dynamite who endowed the prizes, left only vague guidelines for the selection committee.

In his will, he said the prize should be given to those who "shall have conferred the greatest benefit on mankind" and "shall have made the most important discovery or invention within the field of physics."

The prizes, which include the $1.4 million check, a gold medal and a diploma, are presented on Dec. 10, the anniversary of Nobel's death in 1896.

http://www.usatoday.com/tech/science/2006-10-03-physics-nobel-prize_x.htm

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Echo of the Big Bang wins US pair Nobel Prize

John C. Mather and George F. Smoot.

The Nobel Prize in Physics goes to John C. Mather and George F. Smoot "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation".