Astrofisikawan Indonesia Johny Setiawan

Allhamdulilah pagi ini penulis dapat bersahabat dengan Sang Ilmuwan Muda Kelahiran Indonesia dalam jejaring sosial Facebook:

Sang Pencari dan Penemu Planet

Dr. rer. nat. Johny Setiawan, Dipl. Phys.

1. http://www.johny-setiawan.net/
2. http://www.mpia.de/Public/menu_q2.php

Date of birth: 1974 August 16th

Place of birth: Jakarta, Indonesia

Nationality (by ethnicity): Indonesian

Citizenship: German

Home addresses: 10365 Berlin, Germany, 69126 Heidelberg, Germany

Bintaro Sektor IX, Tangerang, Banten, Indonesia


Affiliation: Embassy of the Republic of Indonesia, Lehrter Str. 16-17, 10557 Berlin, Germany

Contact: e-mail: setiawan@indonesian-embassy.de

Tel. +49 30 47807 242

Fax. +49 30 44737 142


School

1981-1986: Elementary school

SD. St. Fransiskus I, Jakarta, Indonesia.

1986-1989: Middle school

SMP Immaculata, Marsudirini, Jakarta, Indonesia.

1989-1992: High school

SMA Fons Vitae I, Marsudirini, Jakarta, Indonesia.



University


1992-1993: Preparatory courses for foreign students (University of Heidelberg).

1993-1999: Undergraduate and graduate studies in physics (Diplom) Albert-Ludwig University of Freiburg.

1999-2003: Doctoral program at the Albert-Ludwig University of Freiburg

2009- 2011: Courses in Law and Business at the University of Mannheim

Courses in Politics at the University of Mannheim

Courses in History at the University of Heidelberg


Work experience


1995-2001: Student assistant for administration of the Evangelisches Studentenwohn-Heim
(student residence) in Freiburg.

1997-1999: Cook in the gastronomy.

Apr-Sept 2000: Student research assistant at the European Southern Observatory, Garching bei München.

Sept 2000-May 2003: Research scientist and doctoral candidate at the Kiepenheuer-Institute for Solar Physics, Freiburg.

Jan-June 2001: Student research assistant at Mettler Toledo AG, Schwerzenbach/Zurich (Switzerland )

June 2003- Sept 2011: Research scientist at the Max-Planck Institute for Astronomy (MPIA) in the Department of Planet and Star formation.

Mar 2012-now: Embassy of the Republic of Indonesia in Berlin, Germany. Section for Economic (and Development).


International experience and collaborations


1999 - 2011 regular visitor at the La Silla observatory in Chile for astronomical observations.

2000 - 2011 collaborations with international colleagues from:

• European Southern Observatory (ESO)

• Université de Genève, Observatoire de Genève (Switzerland)

• Universidad Federal do Rio Grande do Norte (Brazil)

• National Astronomical Observatories, Chinese Academy of Sciences, Beijing (China)

• Department of Physics and Kavli Institute of Astrophysics and Space Research, Massachussetts Institute of Technology, Cambridge, USA

2009 - Now : Deputy chairman (Oct 2009- Jul 2011) and Advisory board member (since Sept. 2011) of Ikatan Ilmuwan Indonesia Internasional (I-4, International Indonesian Scholar Association)


Invitation for giving scientific talks


2008:  European Space Agency (the Netherlands), Kiepenheuer Institute for Solar Physics (Freiburg, Germany), University of Hamburg, University of Jena, Asian Science Camp, Bali, Indonesia

2009: Embassy of the Republic of Indonesia for Germany, Berlin, University of Heidelberg

2010: Department of Astronomy ETH, Zürich, Switzerland, Fakultas Matematika dan Ilmu Pengetahuan Alam, ITB, Indonesia

2011: Torun Centre for Astronomy, Poland

2012:  Arecibo Observatory, Puerto Rico OeAD & Embassy of the Republic of Indonesia for Austria, Vienna

Miscellaneous: language skills and hobbies

Language skills: indonesian (native), german (native-speaker level), english (fluent), spanish (good), french (fair)

Computer skills: Windows, Linux, Unix, SAP/R3

Hobbies: Cooking, travelling, fitness, cultural activities, paleontology & archeology, videography.

http://www.i-4.or.id/

Ikatan Ilmuwan Indonesia Internasional

Penemu Tata Surya Tertua

Johny Setiawan, astronom Indonesia, beserta astronom Eropa berhasil menemukan tata surya tertua. Dunia baru tersebut terdiri atas satu bintang yang dikelilingi oleh dua planet. Tata surya tersebut dikatakan tertua karena berumur 12,8 miliar tahun, hanya 900 juta tahun lebih muda dari semesta yang tercipta lewat Big Bang pada 13,7 miliar tahun lalu.

Bintang induk pada tata surya tersebut diberi nama HIP 11952 sesuai penamaan obyek dari katalog Hipparcos. Sementara kedua planet yang mengorbit bintang tersebut diberi nama HIP 11952 b dan HIP 11952 c. HIP 11952 juga dijuluki "Sannatana". Dalam bahasa Sansekerta, kata tersebut berarti abadi atau purba, sesuai dengan keunikan tata surya baru ini.

Sistem keplanetan yang baru saja ditemukan ini diperkirakan terbentuk saat galaksi Bimasakti masih bayi atau bahkan belum terbentuk. Jarak tata surya ini bahkan tak jauh, hanya 375 tahun cahaya dari Bumi. "Ini sama perumpamaannya dengan menemukan benda arkeologi di pekarangan rumah sendiri," ungkap John.

Dua planet yang mengitari HIP 11952 ditemukan dengan metode kecepatan radial. Teknik ini didasarkan pada observasi gerakan bintang induk akibat planet-planet yang mengelilinginya. Penelitian dilakukan pada tahun 2009-2011 menggunakan spektrometer FEROS (Fibre-fed Extended Range Optical Range Spectograph) pada teleskop 2,2 meter di Observatorium La Silla, Cile.

Berdasarkan penelitian, diketahui bahwa dua planet di tata surya baru ini ialah planet gas raksasa berukuran 0,8 dan 2,9 kali Jupiter. Masing-masing berevolusi dengan periode 7 dan 290 hari.

Anomali

Tata surya baru ini bisa dikatakan anomali. Pasalnya, bintang induk pada sistem keplanetan ini miskin logam, diperkirakan hanya 1 persen dari kandungan logam Matahari. Teori saat ini menyatakan bahwa bintang-bintang dengan kandungan logam tinggi cenderung memiliki peluang lebih besar untuk memiliki planet, dan sebaliknya.

Sejauh ini, HIP 11952b dan HIP 11952c adalah temuan planet kedua yang mengelilingi bintang miskin logam. Tahun 2010, ditemukan planet yang mengelilingi HIP 13044 yang juga miskin logam. Berdasarkan hasil penelitian, Johny mengatakan, "Kedua planet yang mengitari HIP 11952 membuktikan bahwa planet-planet ternyata memang dapat terbentuk di sekitar bintang yang kandungan logamnya sedikit."

Tak cuma itu, Johny yang bertahun-tahun bekerja di Max Planck Institute for Astronomy di Heidelberg, Jerman, mengatakan bahwa planet di sekelilling bintang melarat logam mungkin umum. Observasi pada bintang-bintang tua masih diperlukan untuk mengonfirmasi hal tersebut. Tim peneliti masih akan terus mencari jawabannya.

Secara lebih luas, secara teoritis diketahui bahwa lingkungan awal semesta hanya terdiri atas hidrogen dan helium. Unsur-unsur logam yang lebih berat terbentuk lewat proses lebih lanjut seperti supernova. Penelitian ini menunjukkan bahwa manusia bisa berharap adanya planet-planet purba yang terbentuk pada awal semesta, walau kondisinya dipandang kurang memungkinkan.

Hasil penelitian Johny dipublikasikan di jurnal Astronomy and Astrophysics yang terbit minggu ini. Johny kini mengabdi di Kedutaan Besar Republik Indonesia di Berlin.

Sumber:
1.  http://www.mpia.de/Public/menu_q2.php
Max Planck Institute for Astronomy
Königstuhl 17
D-69117 Heidelberg

Phone:	(++49|0) 6221 – 528-0
Fax:	(++49|0) 6221 – 528-246
E-mail:	sekretariat@mpia.de

2. http://www.eso.org/sci/facilities/lasilla/
La Silla Paranal Observatory: La Silla Facilities

3. http://www.aanda.org/
Journal of Astronomy & Astrophysics

4. http://www.indonesian-embassy.de/
Embassy of the Republic of Indonesia in Berlin - Germany

5. Kompas Sains

Sejarah Perkembangan Ilmu Kosmologi

Main article: Timeline of cosmology

The following table outlines the significant historical cosmologies in chronological order.

Historical descriptions of the cosmos

 

NAME	Author & Date	Classification	REMARKS
Brahmanda	Hindu Rigveda (1500-1200 B.C.)	Cyclical or oscillating, Infinite in time	The universe is a cosmic egg that cycles between expansion and total collapse. It expanded from a concentrated form —a point called a Bindu. The universe, as a living entity, is bound to the perpetual cycle of birth, death, and rebirth
Atomist universe	Anaxagoras (500-428 B.C.) & later Epicurus	Infinite in extent	The universe contains only two things: an infinite number of tiny seeds, or atoms, and the void of infinite extent. All atoms are made of the same substance, but differ in size and shape. Objects are formed from atom aggregations and decay back into atoms. Incorporates Leucippus’ principle of causality: ”nothing happens at random; everything happens out of reason and necessity.” The universe was not ruled by gods.
Stoic universe	Stoics (400-200 B.C.)	Island universe	The cosmos is finite and surrounded by an infinite void. It is in a state of flux, as it pulsates in size and periodically passes through upheavals and conflagrations.
Aristotelian universe	Aristotle (384-322 B.C.)	Geocentric, static, steady state, finite extent, infinite time	Spherical earth is surrounded by concentric celestial spheres. Universe exists unchanged throughout eternity. Contains a 5th element called aether (later known as quintessence).
Aristarchean universe	Aristarchus (circa 280 B.C.)	Heliocentric	Earth rotates daily on its axis and revolves annually about the sun in a circular orbit. Sphere of fixed stars is centered about the sun.
Seleucian universe	Seleucus of Seleucia (circa 190 B.C.)	Heliocentric	Modifications to the Aristarchean universe, with the inclusion of the tide phenomenon to explain heliocentrism.
Ptolemaic model (based on Aristotelian universe)	Ptolemy (2nd century A.D.)	Geocentric	Universe orbits about a stationary Earth. Planets move in circular epicycles, each having a center that moved in a larger circular orbit (called an eccentric or a deferent) around a center-point near the Earth. The use of equants added another level of complexity and allowed astronomers to predict the positions of the planets. The most successful universe model of all time, using the criterion of longevity. Almagest (the Great System).
Aryabhatan model	Aryabhata (499 A.D.)	Geocentric or Heliocentric	The Earth rotates and the planets move in elliptical orbits, possibly around either the Earth or the Sun. It is uncertain whether the model is geocentric or heliocentric due to planetary orbits given with respect to both the Earth and the Sun.
Abrahamic universe	Medieval philosophers (500-1200)	Finite in time	The universe that is finite in time and has a beginning is proposed by the Christian philosopher, John Philoponus, who argues against the ancient Greek notion of an infinite past. Logical arguments supporting a finite universe are developed by the early Muslim philosopher, Alkindus; the Jewish philosopher, Saadia Gaon; and the Muslim theologian, Algazel.
Albumasar model	Ja'far ibn Muhammad Abu Ma'shar al-Balkhi (787-886)	Heliocentric	His planetary orbits are only given with respect to the Sun rather than the Earth, thus suggesting a heliocentric model.
Maragha models	Maragha school (1259-1474)	Geocentric	Various modifications to the Ptolemaic model and Aristotelian universe, such as the rejection of the equant and eccentrics at the Maragheh observatory, the first accurate lunar model by Ibn al-Shatir, and the rejection of a stationery Earth in favour of the Earth's rotation by Ali Kuşçu.
Nilakanthan model	Nilakantha Somayaji (1444-1544)	Geocentric and Heliocentric	A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the later Tychonic system.
Copernican universe	Nicolaus Copernicus (1543)	Heliocentric	The geocentric Maragha model of Ibn al-Shatir adapted to meet the requirements of the ancient heliocentric Aristarchean universe in his De revolutionibus orbium coelestium.
Tychonic system	Tycho Brahe (1546-1601)	Geocentric and Heliocentric	A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the earlier Nilakanthan model.
Static Newtonian	Sir Isaac Newton (1642-1727)	Static (evolving), steady state, infinite	Every particle in the universe attracts every other particle. Matter on the large scale is uniformly distributed. Gravitationally balanced but UNSTABLE.
Cartesian Vortex universe	René Descartes 17th century	Static (evolving), steady state, infinite	A system of huge swirling whirlpools of aethereal or fine matter produces what we would call gravitational effects. His vacuum was not empty. All space was filled with matter that swirled around in large and small vortices.
Hierarchical universe	Immanuel Kant, Johann Lambert 1700s	Static (evolving), steady state, infinite	Matter is clustered on ever larger scales of hierarchy. Matter is endlessly being recycled.
Einstein Universe with a cosmological constant	Albert Einstein 1917	Static (nominally). Bounded (finite)	“Matter without motion.” Contains uniformly distributed matter. Uniformly curved spherical space; based on Riemann’s hypersphere. Curvature is set equal to Λ. In effect Λ is equivalent to a repulsive force which counteracts gravity. UNSTABLE.
De Sitter universe	Willem de Sitter 1917	Expanding flat space. Steady state. Λ > 0	“Motion without matter.” Only apparently static. Based on Einstein’s General Relativity. Space expands with constant acceleration. Scale factor (radius of universe) increases exponentially, i.e. constant inflation.
MacMillan	William MacMillan 1920s	Static & steady state	New matter is created from radiation. Starlight is perpetually recycled into new matter particles.
Friedmann universe of spherical space	Alexander Friedmann 1922	Spherical expanding space. k= +1 ; no Λ	Positive curvature. Curvature constant k = +1 Expands then recollapses. Spatially closed (finite).
Friedmann universe of hyperbolic space	Alexander Friedmann 1924	Hyperbolic expanding space. k= -1 ; no Λ	Negative curvature. Said to be infinite (but ambiguous). Unbounded. Expands forever.
Dirac large numbers hypothesis	Paul Dirac 1930s	Expanding	Demands a large variation in G, which decreases with time. Gravity weakens as universe evolves.
Friedmann zero-curvature, aka the Einstein-DeSitter universe	Einstein & DeSitter 1932	Expanding flat space. k= 0 ; Λ = 0 Critical density	Curvature constant k = 0. Said to be infinite (but ambiguous). ‘Unbounded cosmos of limited extent.’ Expands forever. ‘Simplest’ of all known universes. Named after but not considered by Friedmann. Has a deceleration term q =½ which means that its expansion rate slows down.
Georges Lemaître the original Big Bang. aka Friedmann-Lemaître Model	Georges Lemaître 1927-29	Expansion Λ > 0 Λ > |Gravity|	Λ is positive and has a magnitude greater than Gravity. Universe has initial high density state (‘primeval atom’). Followed by a two stage expansion. Λ is used to destabilize the universe. (Lemaître is considered to be the father of the big bang model.)
Oscillating universe (aka Friedmann-Einstein; was latter’s 1st choice after rejecting his own 1917 model)	Favored by Friedmann 1920s	Expanding and contracting in cycles	Time is endless and beginningless; thus avoids the beginning-of-time paradox. Perpetual cycles of big bang followed by big crunch.
Eddington	Arthur Eddington 1930	first Static then Expands	Static Einstein 1917 universe with its instability disturbed into expansion mode; with relentless matter dilution becomes a DeSitter universe. Λ dominates gravity.
Milne universe of kinematic relativity	Edward Milne, 1933, 1935; William H. McCrea, 1930s	Kinematic expansion with NO space expansion	Rejects general relativity and the expanding space paradigm. Gravity not included as initial assumption. Obeys cosmological principle & rules of special relativity. The Milne expanding universe consists of a finite spherical cloud of particles (or galaxies) that expands WITHIN flat space which is infinite and otherwise empty. It has a center and a cosmic edge (the surface of the particle cloud) which expands at light speed. His explanation of gravity was elaborate and unconvincing. For instance, his universe has an infinite number of particles, hence infinite mass, within a finite cosmic volume.
Friedmann-Lemaître-Robertson-Walker class of models	Howard Robertson, Arthur Walker, 1935	Uniformly expanding	Class of universes that are homogenous and isotropic. Spacetime separates into uniformly curved space and cosmic time common to all comoving observers. The formulation system is now known as the FLRW or Robertson-Walker metrics of cosmic time and curved space.
Steady-state expanding (Bondi & Gold)	Herman Bondi, Thomas Gold 1948	Expanding, steady state, infinite	Matter creation rate maintains constant density. Continuous creation out of nothing from nowhere. Exponential expansion. Deceleration term q = -1.
Steady-state expanding (Hoyle)	Fred Hoyle 1948	Expanding, steady state; but unstable	Matter creation rate maintains constant density. But since matter creation rate must be exactly balanced with the space expansion rate the system is unstable.
Ambiplasma	Hannes Alfvén 1965 Oskar Klein	Cellular universe, expanding by means of matter-antimatter annihilation	Based on the concept of plasma cosmology. The universe is viewed as meta-galaxies divided by double layers —hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic matter-antimatter annihilations keep the bubbles separated and moving apart preventing them from interacting.
Brans-Dicke	Carl H. Brans; Robert H. Dicke	Expanding	Based on Mach’s principle. G varies with time as universe expands. “But nobody is quite sure what Mach’s principle actually means.”
Cosmic inflation	Alan Guth 1980	Big Bang with modification to solve horizon problem and flatness problem.	Based on the concept of hot inflation. The universe is viewed as a multiple quantum flux —hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic expansion kept the bubbles separated and moving apart preventing them from interacting.
Eternal Inflation (a multiple universe model)	Andreï Linde 1983	Big Bang with cosmic inflation	A multiverse, based on the concept of cold inflation, in which inflationary events occur at random each with independent initial conditions; some expand into bubble universes supposedly like our entire cosmos. Bubbles nucleate in a spacetime foam.
Cyclic model	Paul Steinhardt; Neil Turok 2002	Expanding and contracting in cycles; M theory.	Two parallel orbifold planes or M-branes collide periodically in a higher dimensional space. With quintessence or dark energy

Table Notes: the term “static” simply means not expanding and not contracting. Symbol G represents Newton’s gravitational constant; Λ (Lambda) is the cosmological constant.

Unsolved Problems in Physics Part I

“This most beautiful system (The Universe) could only proceed from the dominion of an intelligent and powerful Being.”

~Isaac Newton~

Some of these problems are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

Theoretical problems

The following problems are either fundamental theoretical problems, or theoretical ideas which lack experimental evidence and are in search of one, or both, as most of them are. Some of these problems are strongly interrelated.

For example, extra dimensions or supersymmetry may solve the hierarchy problem. It is thought that a full theory of quantum gravity should be capable of answering most of these problems (other than the Island of stability problem).

Quantum gravity, cosmology, and general relativity

Vacuum catastrophe

Why does the predicted mass of the quantum vacuum have little effect on the expansion of the universe?

Quantum gravity

Can quantum mechanics and general relativity be realized as a fully consistent theory (perhaps as a quantum field theory) Is spacetime fundamentally continuous or discrete?

Would a consistent theory involve a force mediated by a hypothetical graviton, or be a product of a discrete structure of spacetime itself (as in loop quantum gravity)?

Are there deviations from the predictions of general relativity at very small or very large scales or in other extreme circumstances that flow from a quantum gravity theory?

Black holes, black hole information paradox, and black hole radiation

Do black holes produce thermal radiation, as expected on theoretical grounds?

Does this radiation contain information about their inner structure, as suggested by Gauge-gravity duality, or not, as implied by Hawking's original calculation?

If not, and black holes can evaporate away, what happens to the information stored in them

(quantum mechanics does not provide for the destruction of information)?

Or does the radiation stop at some point leaving black hole remnants?

Is there another way to probe their internal structure somehow, if such a structure even exists?

Extra dimensions

Does nature have more than four spacetime dimensions?

If so, what is their size?

Are dimensions a fundamental property of the universe or an emergent result of other physical laws?

Can we experimentally "see" evidence of higher spatial dimensions?

Cosmic inflation

Is the theory of cosmic inflation correct, and if so, what are the details of this epoch?

What is the hypothetical inflaton field giving rise to inflation?

If inflation happened at one point, is it self-sustaining through inflation of quantum-mechanical fluctuations, and thus ongoing in some impossibly distant place?

Multiverse


Are there physical reasons to expect other universes that are fundamentally non-observable?

For instance: Are there quantum mechanical "alternative histories" or "many worlds"?

Are there "other" universes with physical laws resulting from alternate ways of breaking the apparent symmetries of physical forces at high energies, possibly incredibly far away due to cosmic inflation?

Is the use of the anthropic principle to resolve global cosmological dilemmas justified?


The cosmic censorship hypothesis and the chronology protection conjecture

Can singularities not hidden behind an event horizon, known as "naked singularities", arise from realistic initial conditions, or is it possible to prove some version of the "cosmic censorship hypothesis" of Roger Penrose which proposes that this is impossible?

Similarly, will the closed timelike curves which arise in some solutions to the equations of general relativity

(and which imply the possibility of backwards time travel) be ruled out by a theory of quantum gravity which unites general relativity with quantum mechanics, as suggested by the "chronology protection conjecture" of Stephen Hawking?

Arrow of time

What do the phenomena that differ going forward and backwards in time tell us about the nature of time?

How does time differ from space?

Why are CP violations observed in certain weak force decays, but not elsewhere?

Are CP violations somehow a product of the Second Law of Thermodynamics, or are they a separate arrow of time?

Are there exceptions to the principle of causality?

Is there a single possible past?

Is the present moment physically distinct from the past and future or is it merely an emergent property of consciousness?

Why do people appear to agree on what the present moment is?

Locality

Are there non-local phenomena in quantum physics?

If they exist, are non-local phenomena limited to the entanglement revealed in the violations of the Bell Inequalities, or can information and conserved quantities also move in a non-local way?

Under what circumstances are non-local phenomena observed?

What does the existence or absence of non-local phenomena imply about the fundamental structure of spacetime?

How does this relate to quantum entanglement? How does this elucidate the proper interpretation of the fundamental nature of quantum physics?


Future of the universe

Is the universe heading towards a Big Freeze, a Big Rip, a Big Crunch or a Big Bounce?

Is our universe part of an infinitely recurring cyclic model?

Sources:

1. Wikipedia
2. List of links to unsolved problems in physics, prizes and research.
3. Ideas Based On What We’d Like to Achieve
4. 2004 SLAC Summer Institute: Nature's Greatest Puzzles

Photo By:
Arip Nurahman

Lebih Jauh Memahami Energi Gelap

Bibliography

 

 

• HubbleSite press release: New Clues About the Nature of Dark Energy: Einstein May Have Been Right After All.
• 1998 paper announcing the dark energy discovery: Riess et al
• 1999 paper confirming dark energy discovery Perlmutter et al.
• The group that first detected cosmic acceleration: High-Z supernova search team and the group that confirmed it Supernova Cosmology Project.
• Sean Carroll's technical reviews: Why is the universe accelerating?, The Cosmological Constant, and Dark Energy and the Preposterous Universe.
• Jim Peebles, Testing General Relativity on the Scales of Cosmology.
• "The World's Most Successful Nearby Supernova Search Engine", The Katzman Automatic Imaging Telescope.
• Supernova Acceleration Probe (SNAP), a proposed satellite experiment.
• A reanalysis ([2], [3]) of an experiment [R.H. Koch, D. van Harlingen, J. Clarke, Phys. Rev. B 26 (1982) 74] to find the broad-band spectrum of Josephson junction noise current claims to connect it to the spectral frequency upper limit predicted by matching estimates of the dark energy density to the measured vacuum energy density. This claim is not yet accepted. For disputes, see [4], [5], [6].
• Christopher J. Conselice, "The Universe's Invisible Hand," Scientific American. February, 2007.

 

 

External links

 

 

 

• Robert R Caldwell (May 2004). "Dark energy", Physics World.
• Dennis Overbye (November 2006). "9 Billion-Year-Old ‘Dark Energy’ Reported", The New York Times.
• "Mysterious force's long presence" BBC News online (2006) More evidence for dark energy being the cosmological constant
• "Astronomy Picture of the Day" one of the images of the Cosmic Microwave Background which confirmed the presence of dark energy and dark matter
• SuperNova Legacy Survey home page The Canada-France-Hawaii Telescope Legacy Survey Supernova Program aims primarily at measuring the equation of state of Dark Energy. It is designed to precisely measure several hundred high-redshift supernovae.
• "Report of the Dark Energy Task Force"
• "Dark energy" BBC Science & Nature (2006)
• "Dark energy in the accelerating universe" Supernova Acceleration Probe (SNAP) Satellite Observatory home page.
• Emille Ishida. "When did cosmic acceleration start", Astroparticle physics.
• "Calculation of the Cosmological Constant by Unifying Matter and Dark Energy" A geometric model of dark energy as Poincaré sphere - calculated: Ω_D = 0.734, observed: Ω_D = 0.65...0.85 (see also blog).
• "HubbleSite.org -- Dark Energy Website" Multimedia presentation explores the science of dark energy and Hubble's role in its discovery.
• "Surveying the dark side"
• "Dark energy and 3-manifold topology" Acta Physica Polonica 38 (2007), p.3633-3639
• The Dark Energy Survey: https://www.darkenergysurvey.org/
• The Information Equation of State: http://www.mdpi.org/entropy/papers/e10030150.pdf
• The Joint Dark Energy Mission: http://jdem.gsfc.nasa.gov/
• "Dark Energy Found Stifling Growth in Universe", Newswise (December 2008)., is a secondary source (with extra animations) for,
• Harvard: Dark Energy Found Stifling Growth in Universe, primary source

Retrieved from "http://en.wikipedia.org/wiki/Dark_energy"

Categories: Physical cosmology | Energy in physics

Kunjungi Juga:

Central Research for Dark Energy & Dark Matter

Wikipedia

Memahami Sejarah Energi Gelap

The cosmological constant was first proposed by Einstein as a mechanism to obtain a stable solution of the gravitational field equation that would lead to a static universe, effectively using dark energy to balance gravity. Not only was the mechanism an inelegant example of fine-tuning, it was soon realized that Einstein's static universe would actually be unstable because local inhomogeneities would ultimately lead to either the runaway expansion or contraction of the universe. 

The equilibrium is unstable: if the universe expands slightly, then the expansion releases vacuum energy, which causes yet more expansion. Likewise, a universe which contracts slightly will continue contracting. These sorts of disturbances are inevitable, due to the uneven distribution of matter throughout the universe.

More importantly, observations made by Edwin Hubble showed that the universe appears to be expanding and not static at all. Einstein famously referred to his failure to predict the idea of a dynamic universe, in contrast to a static universe, as his greatest blunder. Following this realization, the cosmological constant was largely ignored as a historical curiosity.

Alan Guth proposed in the 1970s that a negative pressure field, similar in concept to dark energy, could drive cosmic inflation in the very early universe. Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the Big Bang. Such expansion is an essential feature of most current models of the Big Bang. 

However, inflation must have occurred at a much higher energy density than the dark energy we observe today and is thought to have completely ended when the universe was just a fraction of a second old. It is unclear what relation, if any, exists between dark energy and inflation. Even after inflationary models became accepted, the cosmological constant was thought to be irrelevant to the current universe.

The term "dark energy" was coined by Michael Turner in 1998. By that time, the missing mass problem of big bang nucleosynthesis and large scale structure was established, and some cosmologists had started to theorize that there was an additional component to our universe. 

The first direct evidence for dark energy came from supernova observations of accelerated expansion, in Riess et al and later confirmed in Perlmutter et al. This resulted in the Lambda-CDM model, which as of 2006 is consistent with a series of increasingly rigorous cosmological observations, the latest being the 2005 Supernova Legacy Survey. 

First results from the SNLS reveal that the average behavior (i.e., equation of state) of dark energy behaves like Einstein's cosmological constant to a precision of 10 per cent. Recent results from the Hubble Space Telescope Higher-Z Team indicate that dark energy has been present for at least 9 billion years and during the period preceding cosmic acceleration.

Sumber:

Central Research for Dark Energy & Dark Matter 

Wikipedia

Implications for the Fate of the Universe

Cosmologists estimate that the acceleration began roughly 5 billion years ago. Before that, it is thought that the expansion was decelerating, due to the attractive influence of dark matter and baryons. 

The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).

If the acceleration continues indefinitely, the ultimate result will be that galaxies outside the local supercluster will move beyond the cosmic horizon: they will no longer be visible, because their line-of-sight velocity becomes greater than the speed of light. This is not a violation of special relativity, and the effect cannot be used to send a signal between them. (Actually there is no way to even define "relative speed" in a curved spacetime. Relative speed and velocity can only be meaningfully defined in flat spacetime or in sufficiently small (infinitesimal) regions of curved spacetime). 

Rather, it prevents any communication between them and the objects pass out of contact. The Earth, the Milky Way and the Virgo supercluster, however, would remain virtually undisturbed while the rest of the universe recedes. In this scenario, the local supercluster would ultimately suffer heat death, just as was thought for the flat, matter-dominated universe, before measurements of cosmic acceleration.

There are some very speculative ideas about the future of the universe. One suggests that phantom energy causes divergent expansion, which would imply that the effective force of dark energy continues growing until it dominates all other forces in the universe. 

Under this scenario, dark energy would ultimately tear apart all gravitationally bound structures, including galaxies and solar systems, and eventually overcome the electrical and nuclear forces to tear apart atoms themselves, ending the universe in a "Big Rip".

On the other hand, dark energy might dissipate with time, or even become attractive. Such uncertainties leave open the possibility that gravity might yet rule the day and lead to a universe that contracts in on itself in a "Big Crunch". Some scenarios, such as the cyclic model suggest this could be the case. 

While these ideas are not supported by observations, they are not ruled out. Measurements of acceleration are crucial to determining the ultimate fate of the universe in big bang theory.

Kunjungi Juga:

Central Research for Dark Energy & Dark Matter 

Wikipedia

Dark Energy and Alternative ideas

Some theorists think that dark energy and cosmic acceleration are a failure of general relativity on very large scales, larger than superclusters. It is a tremendous extrapolation to think that our law of gravity, which works so well in the solar system, should work without correction on the scale of the universe. 

Most attempts at modifying general relativity, however, have turned out to be either equivalent to theories of quintessence, or inconsistent with observations. It is of interest to note that if the equation for gravity were to approach r instead of r² at large, intergalactic distances, then the acceleration of the expansion of the universe becomes a mathematical artifact, negating the need for the existence of Dark Energy.

Alternative ideas for dark energy have come from string theory, brane cosmology and the holographic principle, but have not yet proved as compelling as quintessence and the cosmological constant. On string theory, an article in the journal Nature described:

String theories, popular with many particle physicists, make it possible, even desirable, to think that the observable universe is just one of 10⁵⁰⁰ universes in a grander multiverse, says [Leonard Susskind, a cosmologist at Stanford University in California]. The vacuum energy will have different values in different universes, and in many or most it might indeed be vast. But it must be small in ours because it is only in such a universe that observers such as ourselves can evolve.

Paul Steinhardt in the same article criticizes string theory's explanation of dark energy stating "...Anthropics and randomness don't explain anything... I am disappointed with what most theorists are willing to accept".

In a rather radical departure, an article in the open access journal, Entropy, by Professor Paul Gough, put forward the suggestion that information energy must make a significant contribution to dark energy and that this can be shown by referencing the equation of the state of information in the universe. 

Yet another, "radically conservative" class of proposals aims to explain the observational data by a more refined use of established theories rather than through the introduction of dark energy, focusing, for example, on the gravitational effects of density inhomogeneities, or on consequences of electroweak symmetry breaking in the early universe.

Kunjungi Juga:

Central Research for Dark Energy & Dark Matter 

Wikipedia

Memahami Konstanta Kosmologi

Cosmological constant

 

Main article: Cosmological constant

For more details on this topic, see Equation of state (cosmology).

The simplest explanation for dark energy is that it is simply the "cost of having space": that is, a volume of space has some intrinsic, fundamental energy. This is the cosmological constant, sometimes called Lambda (hence Lambda-CDM model) after the Greek letter Λ, the symbol used to mathematically represent this quantity. 

Since energy and mass are related by E = mc², Einstein's theory of general relativity predicts that it will have a gravitational effect. It is sometimes called a vacuum energy because it is the energy density of empty vacuum. In fact, most theories of particle physics predict vacuum fluctuations that would give the vacuum this sort of energy. 

This is related to the Casimir Effect, in which there is a small suction into regions where virtual particles are geometrically inhibited from forming (e.g. between plates with tiny separation). 

The cosmological constant is estimated by cosmologists to be on the order of 10⁻²⁹g/cm³, or about 10⁻¹²⁰ in reduced Planck units. However, particle physics predicts a natural value of 1 in reduced Planck units, a large discrepancy which is still lacking in explanation.

The cosmological constant has negative pressure equal to its energy density and so causes the expansion of the universe to accelerate. The reason why a cosmological constant has negative pressure can be seen from classical thermodynamics; Energy must be lost from inside a container to do work on the container.

A change in volume dV requires work done equal to a change of energy −p dV, where p is the pressure. But the amount of energy in a box of vacuum energy actually increases when the volume increases (dV is positive), because the energy is equal to ρV, where ρ (rho) is the energy density of the cosmological constant. Therefore, p is negative and, in fact, p = −ρ.

A major outstanding problem is that most quantum field theories predict a huge cosmological constant from the energy of the quantum vacuum, more than 100 orders of magnitude too large. This would need to be cancelled almost, but not exactly, by an equally large term of the opposite sign. 

Some supersymmetric theories require a cosmological constant that is exactly zero, which does not help. The present scientific consensus amounts to extrapolating the empirical evidence where it is relevant to predictions, and fine-tuning theories until a more elegant solution is found. Philosophically, our most elegant solution may be to say that if things were different, we would not be here to observe anything — the anthropic principle.

Technically, this amounts to checking theories against macroscopic observations. Unfortunately, as the known error-margin in the constant predicts the fate of the universe more than its present state, many such "deeper" questions remain unknown.

Another problem arises with inclusion of the cosmic constant in the standard model: i.e., the appearance of solutions with regions of discontinuities (see classification of discontinuities for three examples) at low matter density.

Discontinuity also affects the past sign of the pressure assigned to the cosmic constant, changing from the current negative pressure to attractive, as one looks back towards the early Universe. 

A systematic, model-independent evaluation of the supernovae data supporting inclusion of the cosmic constant in the standard model indicates these data suffer systematic error. The supernovae data are not overwhelming evidence for an accelerating Universe expansion which may be simply gliding.

A numerical evaluation of WMAP and supernovae data for evidence that our local group exists in a local void with poor matter density compared to other locations, uncovered possible conflict in the analysis used to support the cosmic constant.

These findings should be considered shortcomings of the standard model, but only when a term for vacuum energy is included.

In spite of its problems, the cosmological constant is in many respects the most economical solution to the problem of cosmic acceleration. One number successfully explains a multitude of observations. Thus, the current standard model of cosmology, the Lambda-CDM model, includes the cosmological constant as an essential feature.

Sumber:

Wikipedia

Kunjungi Juga:

Central Research for Dark Energy & Dark Matter

GAYA

Gaya-gaya di Alam

"Jika kita bergetar dan tertarik oleh seseorang percayalah itu bukan Gravitasi"

-Arip-

Gaya-gaya fundamental

Berbagai macam gaya yang diamati di alam dapat dijelaskan lewat 4 interaksi dasar yang terjadi antara partikel-partikel elementer:

1. Gaya gravitasi
2. Gaya elektromagnetik
3. Gaya nuklir kuat (juga dinamakan gaya hadronik)
4. Gaya nuklir lemah


Gaya gravitasi antara bumi dan sebuah benda di dekat permukaan bumi adalah berat benda.

Gaya gravitasi yang dikerjakan oleh Matahari pada bumi dan planet-planet lain bertanggung jawab untuk mempertahankan planet-planet dalam orbitnya mengelilingi Matahari.

Demikian pula, gaya gravitasi yang dikerjakan oleh Bumi pada bulan, menjaga Bulan dalam orbitnya yang mendekati lingkaran mengelilingi bumi.

Gaya gravitasi yang dikerjakan oleh bulan dan matahari pada lautan di bumi bertanggung jawab terhadap peristiwa pasang surut.

Gaya elektromagnetik mencakup gaya-gaya listrik dan gaya magnetik.

Sebuah contoh yang terkenal tentang gaya listrik adalah tarikan antara potongan-potongan kertas kecil dan sisir yang telah diberi muatan listrik dengan digosokan pada rambut.

Walaupun gaya magnetik yang terkenal antara sebuah magnet dan benda-benda besi tampaknya sangat berbeda dari gaya listrik, namun sebetulnya gaya magnetik muncul bila muatan listrik dalam keadaan bergerak.

Gaya elektromagnetik antara partikel elementer yang bermuatan sangat lebih besar daripada gaya gravitasi di antara partikel elementer sehingga gaya gravitasi dapat hampir selalu diabaikan.

Sebagai contoh, gaya tolak elektrostatik antara dua proton berorde 10^36 (Sepuluh pangkat 36) kali tarikan gravitasi antara dua proton.

Gaya nuklir kuat terjadi antara partikel-partikel elementer yang dinamakan hadron, yang di dalamnya termasuk proton dan neutron, unsur pokok inti atom.

Gaya ini bertanggung jawab untuk mengikat inti atom menjadi satu.

Sebagai contoh, kedua proton dalam atom helium terikat lewat gaya nuklir yang kuat, yang lebih dari mengimbangi tolakan elektrostatika proton.

Namun, gaya nuklir kuat mempunyai jangkauan sangat pendek. Gaya ini berkurang dengan cepat bersamaan dengan pemisahan partikel-partikel, dan dapat diabaikan jika partikel-partikel terpisah sejauh beberapa diameter nuklir.

Gaya nuklir lemah, yang juga mempunyai jangkauan pendek, terjadi antara elektron dan proton atau neutron.

Gaya inilah yang bertanggung jawab untuk sejenis peluruhan radioaktif tertentu yang dinamakan peluruhan beta.

Gaya-gaya fundamental bekerja di antara partikel-partikel yang terpisah dalam ruang.

Konsep ini dihubungkan dengan aksi pada jarak.

Newton menganggap, aksi pada suatu jarak sebagai suatu cacat dalam teori gravitasinya, tetapi beliau menolak memberikan hipotesis lain.

Dan akhirnya Prof. Newton menuliskan hal berikut ini:

Sir Isaac Newton, surat ketiga kepada Bentley (25 Februari 1692). J. Dodsley, London, 1756.

Tidaklah dapat dibayangkan bahwa benda mati, bahan kasar, tanpa perantara sesuatu yang lain, yang bukan materi, bekerja pada dan mempengaruhi benda lain tanpa saling kontak.

Seperti yang terjadi bila pengertian Gravitasi dalam pengertian Epicurus, adalah penting dan inheren di dalamnya.

Ini adalah satu sebab mengapa saya menginginkan Anda tidak menganggap swadaya gravitasi berasal dari saya.

Bahwa gravitasi haruslah swadaya, inheren dan penting bagi bahan, agar satu benda dapat bekerja pada benda lain pada suatu jarak lewat ruang hampa, tanpa perantaraan apa pun yang lain, oleh dan lewat aksi mereka dan gaya dapat diteruskan dari satu ke yang lainnya.

Untuk saya suatu kemustahilan yang demikian besarnya sehingga saya percaya tidak ada orang yang mempunyai kemampuan berpikir yang baik dalam masalah filosofi dapat jatuh kedalamnya.


Sumber:
Prof. Paul A. Tipler, Ph.D.
Professor of Physics, University of California at Berkeley.
Unduh Buku Physics:  http://www.jalurcepat.com/vzoq6p9r9nin/Physics__5_Ed._-_Paul_A._Tipler.pdf.htm