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53. Dan mereka meminta kepadamu menyegerakan kedatangan azab (yang dijanjikan); dan kalau tidaklah kerana adanya tempoh yang telah ditetapkan, tentulah azab itu akan datang menimpa mereka dan azab itu tetap akan datang menimpa mereka secara mengejut, sedang mereka tidak menyedarinya.

54. Mereka meminta kepadamu menyegerakan kedatangan azab itu, padahal sesungguhnya Neraka Jahannam tetap akan meliputi orang-orang yang kafir –

55. Pada hari azab itu menyelubungi mereka dari sebelah atas mereka dan dari bawah kaki mereka dan (malaikat yang melakukannya) akan berkata kepada mereka: Rasalah kamu (balasan) apa yang kamu telah kerjakan.

56. Wahai hamba-hambaKu yang beriman! Sesungguhnya bumiKu adalah luas (untuk kamu bebas beribadat); oleh itu, (di mana sahaja kamu dapat berbuat demikian) maka hendaklah kamu ikhlaskan ibadat kamu kepadaKu.

57. Tiap-tiap diri (sudah tetap) akan merasai mati, kemudian kamu akan dikembalikan kepada Kami (untuk menerima balasan).

58. Dan orang-orang yang beriman serta beramal soleh, Kami akan tempatkan mereka dalam mahligai-mahligai di Syurga yang mengalir di bawahnya beberapa sungai, mereka kekal di dalamnya. Demikianlah balasan yang sebaik-baiknya bagi orang-orang yang beramal soleh;

59. (Iaitu) mereka yang sabar dan mereka pula berserah diri bulat-bulat kepada Tuhannya.

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The proton-proton chain reaction is one of several fusion reactions by which stars convert hydrogen to helium, the primary alternative being the CNO cycle. The proton-proton chain dominates in stars the size of the Sun or smaller.

Overcoming electrostatic repulsion between two hydrogen nuclei requires a large amount of energy, and this reaction takes an average of 10⁹ years to complete at the temperature of the Sun’s core. Because of the slowness of this reaction the Sun is still shining; if it were faster, the Sun would have exhausted its hydrogen long ago.

In general, proton-proton fusion can occur only if the temperature (i.e. kinetic energy) of the protons is high enough to overcome their mutual Coulomb repulsion. The theory that proton-proton reactions were the basic principle by which the Sun and other stars burn was advocated by Arthur Stanley Eddington in the 1920s. At the time, the temperature of the Sun was considered too low to overcome the Coulomb barrier. After the development of quantum mechanics, it was discovered that tunneling of the wavefunctions of the protons through the repulsive barrier allows for fusion at a lower temperature than the classical prediction.

http://en.wikipedia.org/wiki/Proton-proton_chain

The CNO cycle (for carbon-nitrogen-oxygen), or sometimes Bethe-Weizsäcker-cycle, is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton-proton chain. Theoretical models show that the CNO cycle is the dominant source of energy in stars heavier than the sun. The proton-proton chain is more important in stars the mass of the sun or less. This difference stems from temperature dependency differences between the two reactions; pp-chain reactions start occurring at temperatures around ~4×10⁶ K, making it the dominant force in smaller stars. The CNO chain starts occurring at ~13×10⁶ K, but its energy output rises much faster with increasing temperatures. At ~17×10⁶ K, the CNO cycle start becoming the dominant source of energy. The sun has a temperature of around ~15.7×10⁶ K and only 1.7% of ⁴He nuclei being produced in the Sun are born in the CNO cycle. The CNO process was proposed by Carl von Weizsäcker^[1] and Hans Bethe^[2] independently in 1938 and 1939, respectively.

In the CNO cycle, four protons fuse using carbon, nitrogen and oxygen isotopes as a catalyst to produce one alpha particle, two positrons and two electron neutrinos . The positrons will almost instantly annihilate with electrons, releasing energy in the form of gamma rays. The neutrinos escape from the star carrying away some energy. The carbon, nitrogen, and oxygen isotopes are in effect one nucleus that goes through a number of transformations in an endless loop.

http://en.wikipedia.org/wiki/CNO_cycle

Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only few millions of years (for the most massive) to trillions of years (for the less massive), considerably more than the age of the universe.

Stellar evolution is not studied by observing the life of a single star: most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars, each at a different point in its life, and by simulating stellar structure with computer models.

Stellar_evolution

In physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i.e. the normal, light isotope of hydrogen, whose nuclei consist of a single proton each) during the early phases of the universe. Primordial nucleosynthesis took place just a few minutes after the Big Bang and is believed to be responsible for the formation of a heavier isotope of hydrogen known as deuterium (H-2 or D), the helium isotopes He-3 and He-4, and the lithium isotopes Li-6 and Li-7. In addition to these stable nuclei some unstable, or radioactive, isotopes were also produced during primordial nucleosynthesis: tritium or H-3; beryllium-7 (Be-7), and beryllium-8 (Be-8). These unstable isotopes either decayed or fused with other nuclei to make one of the stable isotopes.

Big Bang nucleosynthesis produced no elements heavier than beryllium, thanks to a bottleneck due to the absence of a stable nucleus with 8 nucleons. In stars, the bottleneck is passed by triple collisions of helium-4 nuclei, producing carbon (the triple-alpha process). However, this process is very slow, taking tens of thousands of years to convert a significant amount of helium to carbon in stars, and therefore it made a negligible contribution in the minutes following the Big Bang.

http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis

Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. (For other such processes, see nucleosynthesis.)

The processes involved began to be understood early in the twentieth century, when it was first realized that the energy released from nuclear reactions accounted for the longevity of the Sun as a source of heat and light. The prime energy producer in the sun is the fusion of hydrogen to helium, which occurs at a minimum temperature of 3 million kelvins.

In 1920, Arthur Eddington, on the basis of the precise measurements of atoms by F.W. Aston, was the first to suggest that stars obtained their energy from nuclear fusion of hydrogen to form helium. In 1928, George Gamow derived what is now called the Gamow factor, a quantum-mechanical formula that gave the probability of bringing two nuclei sufficiently close for the strong nuclear force to overcome the Coulomb barrier. The Gamow factor was used in the decade that followed by Atkinson and Houtermans and later by Gamow himself and Teller to derive the rate at which nuclear reactions would proceed at the high temperatures believed to exist in stellar interiors.

In 1939, in a paper entitled “Energy Production in Stars“, Hans Bethe analyzed the different possibilities for reactions by which hydrogen is fused into helium. He selected two processes that he believed to be the sources of energy in stars. The first one, the proton-proton chain, is the dominant energy source in stars with masses up to about the mass of the Sun. The second process, the carbon-nitrogen-oxygen cycle, which was also considered by Carl Friedrich von Weizsäcker in 1938, is most important in more massive stars. These works concerned the energy generation capable of keeping stars hot. They did not address the creation of heavier nuclei, however. That theory was begun by Fred Hoyle in 1946 with his argument that a collection of very hot nuclei would assemble into iron.^[1] Hoyle followed that in 1954 with a large paper outlining how advanced fusion stages within stars would synthesize elements between carbon and iron in mass.

Key reactions

Cross section of a red giant showing nucleosynthesis and elements formed

The most important reactions in stellar nucleosynthesis:

• Hydrogen burning:
  • The proton-proton chain
  • The carbon-nitrogen-oxygen cycle
• Helium burning:
  • The triple-alpha process
  • The alpha process
• Burning of heavier elements:
  • Carbon burning process
  • Neon burning process
  • Oxygen burning process
  • Silicon burning process
• Production of elements heavier than iron:
  • Neutron capture:
    • The R-process
    • The S-process
  • Proton capture:
    • The Rp-process
  • Photo-disintegration:
    • The P-process

http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

In cosmology, the cosmic microwave background radiation CMB (also CMBR, CBR, MBR, and relic radiation) is a form of electromagnetic radiation filling the universe. ^[1] It has a thermal black body spectrum at a temperature of 2.725 K, thus the spectrum peaks in the microwave range frequency of 160.2GHz, corresponding to a 1.9mm wavelength. The CMB’s discovery in 1965 was the culmination of work initiated in the 1940s.

Measurements of cosmic background radiation are critical to cosmology, since any proposed model of the universe must explain this radiation as we observe it. Although the general feature of a black-body radiation spectrum could potentially be produced by many processes, the spectrum also contains small anisotropies, or irregularities, which vary with the size of the region examined. They have been measured in detail, and match to within experimental error that would be expected if small thermal fluctuations had expanded to the size of the universe we see today. As a result, most cosmologists consider this radiation to be the best evidence for the Big Bang model of the universe. See the plot of power spectrum of the cosmic microwave background radiation temperature anisotropy in terms of the angular scale below for details.

http://en.wikipedia.org/wiki/Cosmic_background_radiation

The Big Bang is the cosmological model of the universe that is best supported by all lines of scientific evidence and observation. The essential idea is that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past and continues to expand to this day. Georges Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, although he called it his ‘hypothesis of the primeval atom’. The framework for the model relies on Albert Einstein‘s General Relativity as formulated by Alexander Friedmann. After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, this observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point. The farther away, the higher the apparent velocity.^[1] If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of the theory. But these accelerators can only probe so far into such high energy regimes. Without any evidence associated with the earliest instant of the expansion, the Big Bang theory cannot and does not provide any explanation for such an initial condition, rather explaining the general evolution of the universe since that instant. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nucleosynthesis.

Fred Hoyle is credited with coining the phrase ‘Big Bang’ during a 1949 radio broadcast, as a derisive reference to a theory he did not subscribe to.^[2] Hoyle later helped considerably in the effort to figure out the nuclear pathway for building certain heavier elements from lighter ones. After the discovery of the cosmic microwave background radiation in 1964, and especially when its collective frequencies sketched out a blackbody curve, most scientists were fairly convinced by the evidence that some Big Bang scenario must have occurred.

http://en.wikipedia.org/wiki/Big_Bang

The Earth’s atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth’s gravity. It contains roughly (by molar content/volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere’s mass is within 11 km of the planetary surface. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space.

http://en.wikipedia.org/wiki/Earth%27s_atmosphere

Outer space, often simply called space, comprises the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations). Contrary to popular understanding, outer space is not completely empty (i.e. a perfect vacuum) but contains a low density of particles, predominantly hydrogen plasma, as well as electromagnetic radiation. Hypothetically, it also contains dark matter and dark energy.

The term “outer space” was first recorded by H. G. Wells in 1901.^[1] The shorter term space is actually older, being first used to mean the region beyond Earth’s sky in John Milton‘s Paradise Lost in 1667.^[2]

All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos. The current temperature of this radiation is about 3 K, or −270 °C (−454 °F).

http://en.wikipedia.org/wiki/Outer_space

Photosynthesis is a series of enzyme-catalyzed steps for the conversion of light energy into chemical energy by living organisms. Its initial substrates are carbon dioxide and water; the energy source is light (electromagnetic radiation); and the end-products are oxygen and (energy-containing) carbohydrates, such as sucrose, glucose or starch. This process is arguably the most important biochemical pathway,^[1] since nearly all life on Earth either directly or indirectly depends on it. It is a complex process occurring in plants, algae, as well as bacteria such as cyanobacteria. Photosynthetic organisms are also referred to as photoautotrophs.^[1]

http://en.wikipedia.org/wiki/Photosynthesis_and_Respiration

Sunlight is Earth’s primary source of energy. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is equal to approximately 1370 watts per square meter at a distance of one AU from the Sun (that is, on or near Earth). Sunlight on the surface of Earth is attenuated by the Earth’s atmosphere so that less power arrives at the surface—closer to 1,000 watts per directly exposed square meter in clear conditions when the Sun is near the zenith. This energy can be harnessed via a variety of natural and synthetic processes—photosynthesis by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds), while direct heating or electrical conversion by solar cells are used by solar power equipment to generate electricity or to do other useful work. The energy stored in petroleum and other fossil fuels was originally converted from sunlight by photosynthesis in the distant past.

http://en.wikipedia.org/wiki/Sun

Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. This is usually during the hours known as day. Near the poles in summer, sunlight also occurs during the hours known as night and in the winter at the poles sunlight may not occur at any time. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun’s radiation. Sunlight may be recorded using a sunshine recorder. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 W•m⁻².

Direct sunlight gives about 93 lumens of illumination per watt of electromagnetic power, including infrared, visible, and ultra-violet.

Bright sunlight provides illumination of approximately 100,000 candella per square meter at the Earth’s surface.

Sunlight is a key factor in the process of photosynthesis.

http://en.wikipedia.org/wiki/Sunlight

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In thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration. A real or imaginary boundary separates the system from the rest of the universe, which is referred to as the environment or surroundings (sometimes called a reservoir). A useful classification of thermodynamic systems is based on the nature of the boundary and the quantities flowing through it, such as matter, energy, work, heat, and entropy. A system can be anything, for example a piston, a solution in a test tube, a living organism, a planet, etc.

The article Carnot heat engine shows the original piston-and-cylinder diagram used by Carnot in discussing his ideal engine; below, we see the Carnot engine as is typically modeled in current use:

Carnot engine diagram (modern) – where heat flows from a high temperature T_H furnace through the fluid of the “working body” (working substance) and into the cold sink T_C, thus forcing the working substance to do mechanical work W on the surroundings, via cycles of contractions and expansions.

In the diagram shown, the “working body” (system), a term introduced by Clausius in 1850, can be any fluid or vapor body through which heat Q can be introduced or transmitted through to produce work. In 1824, Sadi Carnot, in his famous paper Reflections on the Motive Power of Fire, had postulated that the fluid body could be any substance capable of expansion, such as vapor of water, vapor of alcohol, vapor of mercury, a permanent gas, or air, etc. Although, in these early years, engines came in a number of configurations, typically Q_H was supplied by a boiler, wherein water was boiled over a furnace; Q_C was typically a stream of cold flowing water in the form of a condenser located on a separate part of the engine. The output work W here is the movement of the piston as it is used to turn a crank-arm, which was then typically used to turn a pulley so to lift water out of flooded salt mines. Carnot defined work as “weight lifted through a height”.

http://en.wikipedia.org/wiki/Thermodynamic_system

Thermodynamics (from the Greek θερμη, therme, meaning “heat“^[1] and δυναμις, dynamis, meaning “power“) is a branch of physics and is used extensively in chemistry. Thermodynamics studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analysing the collective motion of their particles using statistics.^[2][3] Roughly, heat means “energy in transit” and dynamics relates to “movement”; thus, in essence thermodynamics studies the movement of energy and how energy instills movement. Historically, thermodynamics developed out of need to increase the efficiency of early steam engines.^[4]

Typical thermodynamic system, showing input from a heat source (boiler) on the left and output to a heat sink (condenser) on the right. Work is extracted, in this case by a series of pistons.

The starting point for most thermodynamic considerations are the laws of thermodynamics, which postulate that energy can be exchanged between physical systems as heat or work.^[5] They also postulate the existence of a quantity named entropy, which can be defined for any system.^[6] In thermodynamics, interactions between large ensembles of objects are studied and categorized. Central to this are the concepts of system and surroundings. A system is composed of particles, whose average motions define its properties, which in turn are related to one another through equations of state. Properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes.

With these tools, thermodynamics describes how systems respond to changes in their surroundings. This can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, and even black holes. The results of thermodynamics are essential for other fields of physics and for chemistry, chemical engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, materials science, and economics to name a few.^[7][8]

Thermodynamic_parameters

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In thermodynamics and molecular chemistry, the enthalpy or heat content (denoted as H, h, or rarely as χ) is a quotient or description of thermodynamic potential of a system, which can be used to calculate the “useful” work obtainable from a closed thermodynamic system under constant pressure and entropy.

The term enthalpy was composed of the prefix en-, meaning to “put into” and the Greek word -thalpein, meaning “to heat”, although the original definition is thought to have stemmed from the word “enthalpos” (ἐνθάλπος).^[1]

A thermodynamic potential is a scalar potential function used to represent the thermodynamic state of a system. One main thermodynamic potential which has a physical interpretation is the internal energy, U. It is the energy of configuration of a given system of conservative forces (that is why it is a potential) and only has meaning with respect to a defined set of references (or data). Expressions for all other thermodynamic energy potentials are derivable via Legendre transforms from an expression for U. In thermodynamics, certain forces, such as gravity, are typically disregarded when formulating expressions for potentials. For example, while all the working fluid in a steam engine may have higher energy due to gravity while sitting on top of Mt. Everest than it would at the bottom of the Mariana trench, the gravitational potential energy term in the formula for the internal energy would usually be ignored because changes in gravitational potential within the engine during operation would be negligible. Five common thermodynamic energy potentials are^[1]:

http://en.wikipedia.org/wiki/Thermodynamic_potential

Thermodynamics concerns the physics of heat, work, temperature, energy, and entropy

http://en.wikipedia.org/wiki/Category:Thermodynamics

In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature.^[1][2] In thermodynamics, the quantity TdS is used as a representative measure of the (inexact) heat differential δQ, which is the absolute temperature of an object multiplied by the differential quantity of a system’s entropy measured at the boundary of the object. Heat can flow spontaneously from an object with a high temperature to an object with a lower temperature. The transfer of heat from one object to another object with an equal or higher temperature can happen only with the aid of a heat pump.

High temperature bodies, which often result in high rates of heat transfer, can be created by chemical reactions (such as burning),

nuclear reactions (such as fusion taking place inside the Sun),

electromagnetic dissipation (as in electric stoves), or

mechanical dissipation (such as friction).

Heat can be transferred between objects by radiation, conduction and convection. Temperature is used as a measure of the internal energy or enthalpy, that is the level of elementary motion giving rise to heat transfer. Heat can only be transferred between objects, or areas within an object, with different temperatures (as given by the zeroth law of thermodynamics), and then, in the absence of work, only in the direction of the colder body (as per the second law of thermodynamics). The temperature and phase of a substance subject to heat transfer are determined by latent heat and heat capacity. A related term is thermal energy, loosely defined as the energy of a body that increases with its temperature.

http://en.wikipedia.org/wiki/Heat