Academia Arena
Energy budget of the universe
Yüklə 283,52 Kb.
|
Energy budget of the universe Today Dark Matter, 23 % Dark Energy, 73% Ordinary Matter, 4% Out of 4% we only make up 0.03% of the ordinary matter.
Dark Matter, 63% Neutrinos, 10% Photons, 15% Ordinary Matter, 12% Opening up the splendor of the immense heavens for the first time to serious scientific investigation. On the short time scale of our lives, not surprisingly, we underwent many transformations in our slow, painful evolution, an evolution often overshadowed by religious dogma and superstition to seek the answer to the question from the beginnings of our understanding. No progress was made in any scientific explanations because the experimental data were non-existent and there were no theoretical foundations that could be applied. In the latter half of the 20th century, there were several attempts such as quantum mechanics (the theory of subatomic physics and is one of the most successful theories of all time which is based on three principles: (1) energy is found in discrete packets called quanta; (2) matter is based on point particles but the probability of finding them is given by a wave, which obeys the Schrödinger wave equation; (3) a measurement is necessary to collapse the wave and determine the final state of an object), the “big bang,” probability theory, the general relativity (a theoretical framework of geometry which has been verified experimentally to better than 99.7 percent accuracy and predicts that the curvature of space-time gives the illusion that there is a force of attraction called gravity) to adjust to ensure agreement with experimental measurements and answer the questions that have so long occupied the mind of philosophers (from Aristotle to Kant) and scientists. However, we must admit that there is ignorance on some issues, for example, “we don’t have a complete theory of universe which could form a framework for stitching these insights together into a seamless whole – capable of describing all phenomena…. We are not sure exactly how universe happened.” However, the generally accepted history of the universe, according to what is so-called the big bang theory (proposed by a Belgian priest, Georges Lemaître, who learned of Einstein’s theory and was fascinated by the idea that the theory logically led to a universe that was expanding and therefore had a beginning) has completely changed the discussion of the origin of the universe from almost pure speculation to an observational subject. In such model one finds that our universe started with an explosion. This was not any ordinary explosion as might occur today, which would have a point of origin (center) and would spread out from that point. The explosion occurred simultaneously everywhere, filling all space with infinite heat and energy. At this time, order and structure were just beginning to emerge − the universe was hotter and denser than anything we can imagine (at such temperatures and densities (of about a trillion trillion trillion trillion trillion trillion (1 with 72 zeros after it) tons per cubic inch) gravity and quantum mechanics were no longer treated as two separate entities as they were in point-particle quantum field theory, the four known forces were unified as one unified super force) and was very rapidly expanding much faster than the speed of light (this did not violate Einstein’s dictum that nothing can travel faster than light, because it was empty space that was expanding) and cooling in a way consistent with Einstein field equations. As the universe was expanding, the temperature was decreasing. Since the temperature was decreasing, the universe was cooling and its curvature energy was converted into matter like a formless water vapor freezes into snowflakes whose unique patterns arise from a combination of symmetry and randomness. Approximately 10−37 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe underwent an incredible amount of superliminal expansion and grew exponentially by a factor e3Ht (where H was a constant called Hubble parameter and t was the time) – just as the prices grew by a factor of ten million in a period of 18 months in Germany after the First World War and it doubled in size every tiny fraction of a second – just as prices double every year in certain countries. After inflation stopped, the universe was not in a de Sitter phase and its rate of expansion was no longer proportional to its volume since H was no longer constant. At that time, the entire universe had grown by an unimaginable factor of 1050 and consisted of a hot plasma “soup” of high energetic quarks as well as leptons (a group of particles which interacted with each other by exchanging new particles called the W and Z bosons as well as photons). There were a number of different varieties of quarks: there were six “flavors,” which we now call up, down, strange, charmed, bottom, and top. And among the leptons the electron was a stable object and muon (that had mass 207 times larger than electron and now belongs to the second redundant generation of particles found in the Standard Model) and the tauon (that had mass 3,490 times the mass of the electron) were allowed to decay into other particles. And associated to each charged lepton, there were three distinct kinds of ghostly particles called neutrinos (the most mysterious of subatomic particles, are difficult to detect because they rarely interact with other forms of matter. Although they can easily pass through a planet or solid walls, they seldom leave a trace of their existence. Evidence of neutrino oscillations prove that neutrinos are not massless but instead have a mass less than one-hundred-thousandth that of an electron):
Assuming the black hole of mass M would emit Hawking radiation at the same rate P through its evaporation time, expression for evaporation time of the black hole can be written as tev = Mc2/P On the other hand, assuming the black hole would not emit Hawking radiation at the same rate through its evaporation time, expression for evaporation time of the black hole can be written as tev = Mc2/3P In general, tev = k (Mc2/P) If k =1, then the black hole would emit Hawking radiation at the same rate through its evaporation time. If k =1/3, then the black hole would not emit Hawking radiation at the same rate through its evaporation time. What the factor k imply? Temperatures were so high that these quarks and leptons were moving around so fast that they escaped any attraction toward each other due to nuclear or electromagnetic forces. However, they possessed so much energy that whenever they collided, particle – antiparticle pairs of all kinds were being continuously created and destroyed in collisions. And the uncertainty in the position of the particle times the uncertainty in its velocity times the mass of the particle was never smaller than a certain quantity, which was known as Planck’s constant. Similarly, ∆E × ∆t was ≤ h/4π (where h was a quantity called Planck’s constant and π = 3.14159... was the familiar ratio of the circumference of a circle to its diameter). Hence the Heisenberg’s uncertainty principle (which captures the heart of quantum mechanics – i.e. features normally thought of as being so basic as to be beyond question (e.g. that objects have definite positions and speeds and that they have definite energies at definite moments) are now seen as mere artifacts of Planck’s constant being so tiny on the scales of the everyday world) was a fundamental, inescapable property of the universe. At some point an unknown reaction led to a very small excess of quarks and leptons over antiquarks and antileptons — of the order of one part in 30 million. This resulted in the predominance of matter over antimatter in the universe. The universe continued to decrease in density and fall in temperature, hence the typical energy of each particle was decreased in inverse proportion to the size of the universe (since the average energy – or speed – of the particles was simply a measure of the temperature of the universe). The symmetry (a central part of the theory [and] its experimental confirmation would be a compelling, albeit circumstantial, piece of evidence for strings) however, was unstable and, as the universe cooled, a process called spontaneous symmetry breaking phase transitions placed the fundamental forces of physics and the parameters of elementary particles into their present form. After about 10−11 seconds, the picture becomes less speculative, since particle energies drop to values that can be attained in particle physics experiments. At about 10−6 seconds, there was a continuous exchange of smallest constituents of the strong force called gluons between the quarks and this resulted in a force that pulled the quarks to form little wisps of matter which obeys the strong interactions and makes up only a tiny fraction of the matter in the universe and is dwarfed by dark matter called the baryons ( protons – a positively charged particles very similar to the neutrons, which accounts for roughly half the particles in the nucleus of most atoms and are much more massive than electrons -1,836 times more massive − and neutrons – a neutral subatomic particles which, along with the protons, makes up the nuclei of atoms and are 1,838 times more massive than electrons – belonged to the class baryons) as well as other particles. The small excess of quarks over antiquarks led to a small excess of baryons over antibaryons. The proton was composed of two up quarks and one down quark and the neutron was composed of two down quarks and one up quark. And other particles contained other quarks (strange, charmed, bottom, and top), but these all had a much greater mass and decayed very rapidly into protons and neutrons. The charge on the up quark was = + 2/3 e and the charge on the down quark was = – 1/3 e. The other quarks possessed charges of + 2/3 e or – 1/3 e. The charges of the quarks added up in the combination that composed the proton but cancelled out in the combination that composed the neutron i.e., Proton charge was = (2/3 e) + (2/3 e) + (–1/3 e) = e Neutron charge was = (2/3 e) + (–1/3 e) + (–1/3 e) = 0 And the force that confined the mass of the proton or the neutron (i.e., its constituent particles) to its radius was = its rest mass energy divided by its radius i.e., for the proton of radius ≈ 1.112 × 10 −15 meter: F was = 13.52 × 10 to the power of 26 Newton. And this force was so strong that it is now proved very difficult if not impossible to obtain an isolated quark. As we try to pull them out of the proton or neutron it gets more and more difficult. Even stranger is the suggestion that the harder and harder if we could drag a quark out of a proton this force gets bigger and bigger – rather like the force in a spring as it is stretched causing the quark to snap back immediately to its original position. This property of confinement prevented one from observing an isolated quark (and the question of whether it makes sense to say quarks really exist if we can never isolate one was a controversial issue in the years after the quark model was first proposed). However, now it has been revealed that experiments with large particle accelerators indicate that at high energies the strong force becomes much weaker, and one can observe an isolated quark. In fact, the standard model (one of the most successful physical theories of all time and since it fails to account for gravity (and seems so ugly), theoretical physicists feel it cannot be the final theory) in its current form requires that the quarks not be free. The observation of a free quark would falsify that aspect of the standard model, although nicely confirm the quark idea itself and fits all the experimental data concerning particle physics without exception. Each quark possessed baryon number = 1/3: the total baryon number of the proton or the neutron was the sum of the baryon numbers of the quarks from which it was composed. And the electrons and neutrinos contained no quarks; they were themselves truly fundamental particles. And since there were no electrically charged particles lighter than an electron and a proton, the electrons and protons were prevented from decaying into lighter particles – such as photons (that carried zero mass, zero charge, a definite energy Ephoton = pc and a momentum p = mc) and less massive neutrinos (with very little mass, no electric charge, and no radius — and, adding insult to injury, no strong force acted on it). And a free neutron being heavier than the proton was not prevented from decaying into a proton (plus an electron and an antineutrino). The temperature was now no longer high enough to create new proton–antiproton pairs, so a mass annihilation immediately followed, leaving just one in 1010 of the original protons and neutrons, and none of their antiparticles (i.e., antiparticle was sort of the reverse of matter particle. The counterparts of electrons were positrons (positively charged), and the counterparts of protons were antiprotons (negatively charged). Even neutrons had an antiparticle: antineutrons). A similar process happened at about 1 second for electrons and positrons (positron: the antiparticle of an electron with exactly the same mass as an electron but its electric charge is +1e). After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistically and the energy density of the universe was dominated by photons − (what are sometimes referred to as the messenger particles for the electromagnetic force) − with a minor contribution from neutrinos. The density of the universe was about 4 × 10 9 times the density of water and much hotter than the center of even the hottest star – no ordinary components of matter as we know them – molecules, atoms, nuclei – could hold together at this temperature. And the total positive charge due to protons plus the total negative charge due to electrons in the universe was = 0 (Just what it was if electromagnetism would not dominate over gravity and for the universe to remain electrically neutral). And a few minutes into the expansion, when the temperature was about a billion (one thousand million; 10 to the power of 9) kelvin and the density was about that of air, protons and neutrons no longer had sufficient energy to escape the attraction of the strong nuclear force and they started to combine together to produce the universe’s deuterium and helium nuclei in a process called Big Bang nucleosynthesis. And most of the protons remained uncombined as hydrogen nuclei. And inside the tiny core of an atom, consisting of protons and neutrons, which was roughly 10 −13 cm across or roughly an angstrom, a proton was never permanently a proton and also a neutron was never permanently a neutron. They kept on changing into each other. A neutron emitted a π meson (a particle predicted by the Japanese physicist Hideki Yukawa and observed in cosmic ray experiments (for which he was awarded the Nobel Prize in physics in 1949) – composed of a quark and antiquark, which is unstable because the quark and antiquark can annihilate each other, producing electrons and other particles) and became proton and a proton absorbed a π meson and became a neutron. That is, the exchange force resulted due to the absorption and emission of π mesons kept the protons and neutrons bound in the nucleus. And the time in which the absorption and emission of π mesons took place was so small that π mesons were not detected. And a property of the strong force called asymptotic freedom caused it to become weaker at short distances. Hence, although quarks were bound in nuclei by the strong force, they moved within nuclei almost as if they felt no force at all. Within only a few hours of the big bang, the Big Bang nucleosynthesis stopped. And after that, for the next million years or so, the universe just continued expanding, without anything much happening. Eventually, once the temperature had dropped to a few thousand degrees, there was a continuous exchange of virtual photons between the nuclei and the electrons. And the exchange was good enough to produce — what else? — A force (proportional to a quantity called their charge and inversely proportional to the square of the distance between them). And that force pulled the electrons towards the nuclei to form neutral atoms (the basic unit of ordinary matter (Atom is from a Greek word meaning “unbreakable” because at the time atoms were first dealt with, it was thought they could not be broken up into smaller units), made up of a tiny nucleus (consisting of protons and neutrons) surrounded by orbiting electrons). And these atoms reflected, absorbed, and scattered light and the resulted light was red shifted by the expansion of the universe towards the microwave region of the electromagnetic spectrum. And there was cosmic microwave background radiation (which, through the last 15 billion years of cosmic expansion, has now cooled to a mere handful of degrees above absolute zero (–273ºC − the lowest possible temperature, at which substances contain no heat energy and all vibrations stop—almost: the water molecules are as fixed in their equilibrium positions as quantum uncertainty allows) and today, scientists measure tiny deviations within this background radiation to provide evidence for inflation or other theories). The irregularities in the universe meant that some regions of the nearly uniformly distributed atoms had slightly higher density than others. The gravitational attraction of the extra density slowed the expansion of the region, and eventually caused the region to collapse to form galaxies and stars. And the nuclear reactions in the stars transformed hydrogen to helium (composed of two protons and two neutrons and symbolized by 2He4, highly stable—as predicted by the rules of quantum mechanics) to carbon (with their self-bonding properties, provide the immense variety for the complex cellular machinery— no other element offers a comparable range of possibilities) with the release of an enormous amount of energy via Einstein’s equation E = mc2. This was the energy that lighted up the stars. And the process continued converting the carbon to oxygen to silicon to iron. And the nuclear reaction ceased at iron. And the star experienced several chemical changes in its innermost core and these changes required huge amount of energy which was supplied by the severe gravitational contraction. And as a result the central region of the star collapsed to form a neutron star. And the outer region of the star got blown off in a tremendous explosion called a supernova, which outshone an entire galaxy of 100 billion stars, spraying the manufactured elements into space. And these elements provided some of the raw material for the generation of cloud of rotating gas which went to form the sun and a small amount of the heavier elements collected together to form the asteroids, stars, comets, and the bodies that now orbit the sun as planets like the Earth and their presence caused the fabric of space around them to warp (more massive the bodies, the greater the distortion it caused in the surrounding space). The earth was initially very hot and without an atmosphere. In the course of time the planet earth produced volcanoes and the volcanoes emitted water vapor, carbon dioxide and other gases. And there was an atmosphere. This early atmosphere contained no oxygen, but a lot of other gases and among them some were poisonous, such as hydrogen sulfide (the gas that gives rotten eggs their smell). And the sunlight dissociated water vapor and there was oxygen. And carbon dioxide in excess heated the earth and balance was needed. So carbon dioxide dissolved to form carbonic acid and carbonic acid on rocks produced limestone and subducted limestone fed volcanoes that released more carbon dioxide. And there was high temperature and high temperature meant more evaporation and dissolved more carbon dioxide. And as the carbon dioxide turned into limestone, the temperature began to fall. And a consequence of this was that most of the water vapor condensed and formed the oceans. And the low temperature meant less evaporation and carbon dioxide began to build up in the atmosphere. And the cycle went on for billions of years. And after the few billion years, volcanoes ceased to exist. And the molten earth cooled, forming a hardened, outer crust. And the earth’s atmosphere consisted of nitrogen, oxygen, carbon dioxide, plus other miscellaneous gases (hydrogen sulfide, methane, water vapor, and ammonia). And then a continuous electric current through the atmosphere simulated lightning storms. And some of the gases came to be arranged in the form of more complex organic molecules such as simple amino acids (the basic chemical subunit of proteins, when, when linked together, formed proteins) and carbohydrates (which were very simple sugars). And the water vapor in the atmosphere probably caused millions of seconds of torrential rains, during which the organic molecules reached the earth. And it took two and a half billion years for an ooze of organic molecules to react and built earliest cells as a result of chance combinations of atoms into large structures called macromolecules and then advance to a wide variety of one – celled organisms, and another billion years to evolve through a highly sophisticated form of life to primitive mammals endowed with two elements: genes (a set of instructions that tell them how to sustain and multiply themselves), and metabolism (a mechanism to carry out the instructions). But then evolution seemed to have speeded up. It only took about a hundred million years to develop from the early mammals (the highest class of animals, including the ordinary hairy quadrupeds, the whales and Mammoths, and characterized by the production of living young which are nourished after birth by milk from the teats (MAMMAE, MAMMARY GLANDS) of the mother) to Homosapiens. This picture of a universe that started off very hot and cooled as it expanded (like when things are compressed they heat up... and, when things... expand... they cool down) is in agreement with all the observational evidence which we have today (and it explains Olbers’ paradox: The paradox that asks why the night sky is black. If the universe is infinite and uniform, then we must receive light from an infinite number of stars, and hence the sky must be white, which violates observation). Nevertheless, it leaves a number of important questions unanswered: Why the universe started off very hot i.e., why it violently emerged from a state of infinite compression? Why is the universe the same everywhere i.e., looks the same from every point (homogeneous) and looks the same in every direction (isotropic)? If the cosmic inflation made the universe flat, homogeneous and isotropic, then what is the hypothetical field that powered the inflation? What are the details of this inflation? Much is explained by protons and electrons. But there remains the neutrino… ≈10 9 neutrinos/ proton. What is their physical picture in the universe? The big bang theory, on its own, cannot explain these features or answer these questions because of its prediction that the universe started off with infinite density at the big bang singularity. At the singularity (a state of infinite gravity), all the known physical laws of cosmology would break down: one couldn’t predict what would come out of the infinitely dense Planck-sized nugget called the singularity. The search for the origin and fate of the universe (which is determined by whether the Omega (Ω0) density parameter is less than, equal to or greater than 1) is a distinctly human drama, one that has stretched the mind and enriched the spirit. We (a species ruled by all sorts of closer, warmer, ambitions and perceptions) are all, each in our own way, seekers of an absolute limit of scientific explanation (that may never be achieved) and we each long for an answer to why we exist... as our future descendants marvels at our new view of the universe... we are... contributing our wrong to the human letter reaching for the stars. Sun emits 2×1038 neutrinos per second but only 30 neutrinos are interacting in a person per year. The fine tuning coincidences are updated and refurbished and have been somewhat misleadingly categorized under the designation anthropic principle, a term coined by astronomer Brandon Carter in 1974 – which states that the physical properties of the universe are as they are because they permit the emergence of life. This teleological principle tries to explain why some physical properties of matter seem so fine-tuned as to permit the existence of life -- and are widely claimed to provide prima facie evidence for purposeful design—a design with life and perhaps humanity in mind. However, fatal to the evidence of deistic design: ARGUMENT 1 As we know that, inside the sun, we have NProtons (say), which can be calculated by the equation: NProtons = Msun / mProton, where Msun = mass of the sun and mProton = rest mass of the proton. If mProton was still smaller than 1.672 × 10 −27 kg, then NProtons would have been larger than 1.196 × 10 57. Hence, the stellar life time of the sun would have been slightly higher than its actual value. ARGUMENT 2 The universe is a pretty big place seems like an awful waste of space Nearest star: 4.22 light years. Nearest galaxy: 2.44 million light years. Galaxies within our horizon are now 40 billion light years away. Universe beyond horizon: 10 to the 10 to the 100 times bigger. ARGUMENT 3 The Goldilocks Planet is not all that well suited for human life. 2/3 salt water unfit for drinking. Humans are restricted only to surface. Atmosphere does not block harmful ultraviolet radiation which causes skin cancer and other genetic disorders. Natural calamities like floods, earthquakes, famine and droughts, diseases like cancer, AIDS, kill millions millions of people yearly. ARGUMENT 4 Only two photons of every billion emitted by sun are used to warm the Earth surface, the rest radiating uselessly into space.. And lack of oxygen and cosmic microwave background radiation (which is well characterized by a 2.728 ± 0.002 Kelvin black body spectrum over more than three decades in frequency) prevents humans from spending years in outer space. --is the unwarranted assumption that the universe is exquisitely designed with the goal of generating and sustaining observers. Of course, fine tuning coincidences are only needed to fill in the details of evidence for the existence of insulated interpositions of Divine power. If the universe were congenial to human life, then we would expect it to be easy for humanlike life to develop and survive throughout the vast stretches of the universe (an intricately complex place). We must admit that much of what we believe, including our fundamental coincidences about the universe: COINCIDENCE 1 If c would have been = 3×10 to the power of −8 meters per second, then according to the equation E = mc squared (which asserts: energy and mass is the ultimate convertible currency): 1 kg of mass would have yielded only 9 × 10 to the power of −16 joules of energy. Hence, thousands and thousands of hydrogen atoms in the sun would have to burn up to release 4 × 10 to the power of 26 joules of energy per second in the form of radiation. Therefore, sun would have ceased to black hole even before an ooze of organic molecules would react and built earliest cells and then advance to a wide variety of one – celled organisms, and evolve through a highly sophisticated form of life to primitive mammals. COINCIDENCE 2 If the value of G would have been far greater than its actual value, then according to the equation FGravity = GMm/r2 (which asserts-- that the strength of attraction between two bodies is larger for larger-mass bodies and smaller for smaller-mass bodies and is larger for smaller separations between the bodies and smaller for larger separations): Each star in the universe would have been attracted toward every other star by a force far greater than its present value, so it seemed the stars would have got very near each other, the attractive forces between them would have become stronger and dominate over the repulsive forces so that the stars would have fell together at some point to form a sphere of roughly infinite density. COINCIDENCE 3 If Λ (cosmological constant – a constant that measures the curvature of an empty space devoid of gravitational fields) would have been = 0, then according to the equation vacuum energy density (a non-vanishing energy density of the vacuum that is the same at every point in the Universe) = Λc2 /8πG would have been = 0 i.e., the entire vacuum would have been empty. The empty vacuum though unstable would have ceased to exist. COINCIDENCE 4 If the value of G would have been far greater than its actual value, then according to the equation U = −3GM2 /5r: The gravitational binding energy of a star would have been far greater than its present value, so it seemed the matter inside the star would have been very much compressed and far hotter than it is. And the distance between the constituents of the star would have been decreased beyond the optimum distance (maximum distance below which the gravitational force is no longer attractive it turns to a repulsive force) then all the stars would have exploded spraying the manufactured elements into space. No sun would have existed to support life on the earth. COINCIDENCE 5 If there was no principle what is called Pauli’s exclusion principle (discovered in 1925 by an Austrian physicist, Wolfgang Pauli – for which he received the Nobel Prize in 1945) stating that two similar particles cannot exist in the same state; that is, they cannot have both the same position and the same velocity, within the limits given by the uncertainty principle.
Yüklə 283,52 Kb. Dostları ilə paylaş:
|