FPGA In Space

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: justify;"> <span class="Apple-style-span" style="color: #073763;">A quiet revolution is taking place. Over the past few years, the density of the average programmable logic device has begun to skyrocket. The maximum number of gates in an FPGA is currently around 500,000 and doubling every 18 months. Meanwhile, the price of these chips is dropping. What all of this means is thatthe price of an individual NAND or NOR is rapidly approaching zero! And the designers of embedded systems are taking note. Some system designers are buying processor cores and incorporating them into system-on-a-chip designs; others are eliminating the processor and software altogether, choosing an alternative hardware-only design. As this trend continues, it becomes more difficult to separate hardware from software. After all, both hardware and software designers are now describinglogic in high-level terms, albeit in different languages, and downloading the compiledresult to a piece of silicon. Surely no one would claim that language choice alone marks a real distinction between the two fields. Turing's notion of machine-level equivalence and the existence of language-to-language translators have long ago taught us all that that kind of reasoning isfoolish. There are even now products that allow designersto create their hardware designs in traditional programming languages like C. So language differences alone are not enough of a distinction. Both hardware and software designs are compiled from a human-readable form into a machine-readable one. And both designs are ultimately loaded into some piece of silicon. Does it matter that one chip is a memory device and the other a piece of programmable logic? If not, how else can we distinguish hardware from software? Regardless of where the line is drawn, there will continue to be engineers like you and me who cross the boundary in our work. So rather than try to nail down a precise boundary between hardware and software design, we must assume that there will be overlap in the two fields. And we must all learn about new things. Hardware designers must learn how to write better programs, and software developers must learn how to utilize programmable logic. TYPES OF PROGRAMMABLE LOGIC Many types of programmable logic are available. The current range of offerings includes everything from small devices capable of implementing only a handful of logic equations to huge FPGAs that can hold an entireprocessor core (plus peripherals!). In addition to this incredible difference in size there is also much variation in architecture. In this section, I'll introduce youto the most common types of programmable logic and highlight the most important features of each type. PLDs At the low end of the spectrum are the original Programmable Logic Devices (PLDs). These were the first chips that could be used to implement a flexible digital logic design in hardware. In other words, you could remove a couple of the 7400-series TTL parts (ANDs, ORs, and NOTs) from your board and replace them with a single PLD. Other names you might encounter for this class of device are Programmable Logic Array (PLA), Programmable Array Logic (PAL), and Generic Array Logic (GAL)</span></div> <div style="text-align: justify;"> <span class="Apple-style-span" style="color: #073763;"><br /></span></div> <div style="text-align: justify;"> <span class="Apple-style-span" style="color: #073763;">.</span></div> </div>

FPGA In Space

A quiet revolution is taking place. Over the past few years, the density of the average programmable logic device has begun to skyrocket. ...

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DOES OUR UNIVERSE BORN INSIDE A BLACK HOLE?

<div dir="ltr" style="text-align: left;" trbidi="on"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;"></span><br /> <div> <div> <div style="text-align: center;"> Cosmology, physics, nature, space, general theory of relativity.</div> </div> </div> <div> <div style="text-align: center;"> <img alt="DOES OUR UNIVERSE BORN INSIDE A BLACK HOLE? - px bh lmc" hspace="0" src="http://f0.pepst.com/c/72282F/421282/ssc3/home/039/physics.subha/300px_bh_lmc.png_480_480_0_64000_0_1_0.png" vspace="0" /></div> </div> <div> <div class="space2" style="padding-bottom: 0.5em; padding-top: 0.5em;"> <div class="hr" style="border-top-color: rgb(170, 170, 170); border-top-style: solid; border-top-width: 1px; color: #aaaaaa;"> </div> </div> </div> <div> Lee Smolin is a physicist, he is a cosmologist known for his complicated theory of Space Geometry. In his book "The Life of the Cosmos" (the book link:<a href="http://peperonity.com/go/external?act=0-5351984-1355895408_17cdb03" style="color: blue; outline-color: initial; outline-style: initial; outline-width: 0px; text-decoration: underline;">http://bit.ly/ctnoUN</a> ) he theorizes a radical possibility in the theory of origin of our Universe. He is one of the foremost proponents of the theory of Universe born inside of Black Holes. He goes even further to emphasize the hypothesis of a natural selection like drive to create black hole more efficiently. In a nutshell his theory proposes a picture of universe as a giant machinery whose sole purpose is to create black holes more smoothly as well as efficiently.<br /> <br /> Recently, a physicist fron Indiana University, Mr. Nikodem Poplawski modified the general theory of relativity to incorporates the intrinsic spin of Fermions, and is known as Einstein-Cartan-Kibble-Sciama theory of Gravity.<br /> <br /> This theory predicts a repulsive force known as "Torsion", which may act as the Repulsive Force in the theory of Inflation, incorporated within the "Big Bang Theory" of the creation of our Universe.<br /> <br /> So what is the relation of Black holes and this Torsion? One of the prediction of this theory is that the energy density inside a black hole, and the torsion that results from it, actually prevents a black hole singularity from forming. Instead, the region inside the black hole would begin expanding as its own universe, just as the "science fiction" theories of Smolin and others have predicted in the past. </div> </div>

DOES OUR UNIVERSE BORN INSIDE A BLACK HOLE?

Cosmology, physics, nature, space, general theory of relativity. Lee Smolin is a physicist, he is a cosmologist known for...

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STEPHEN HAWKING : ALIENS EXIST !

<div dir="ltr" style="text-align: left;" trbidi="on"> <div style="text-align: center;"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; line-height: 22px;"><strong><span class="Apple-style-span" style="font-size: x-large;"><br /></span></strong></span></div> <div style="text-align: center;"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; line-height: 22px;"><strong><span class="Apple-style-span" style="font-size: x-large;">STEPHEN HAWKING : ALIENS EXIST !</span></strong></span></div> <div style="text-align: center;"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; line-height: 22px;"><strong><span class="Apple-style-span" style="font-size: x-large;"><br /></span></strong></span></div> <div style="text-align: center;"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; line-height: 22px;"><strong><span class="Apple-style-span" style="font-size: x-large;"><br /></span></strong></span></div> <div style="text-align: center;"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; line-height: 22px;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span></div> <strong></strong><br /> <strong><div> <span class="Apple-style-span" style="color: black;"><img alt="STEPHEN HAWKING : ALIENS EXIST !" hspace="0" src="http://f1.pepst.com/c/B7E06F/306401/ssc3/home/032/blog.subha/2010042661472001.jpg_480_480_0_64000_0_1_0.jpg" vspace="0" /></span></div> <div> <div class="space2" style="padding-bottom: 0.5em; padding-top: 0.5em;"> <div class="hr" style="border-top-color: rgb(170, 170, 170); border-top-style: solid; border-top-width: 1px;"> <span class="Apple-style-span" style="color: black;"></span></div> </div> </div> <div> <div style="text-align: left;"> <span class="Apple-style-span" style="color: black; font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="color: black; font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">London: Do aliens exist? They do, but humans should try to avoid any contact with them — at least, that's what one of the world's leading physicists, Stephen Hawking, claims. </span></div> </span></span></strong></span></div> <span class="Apple-style-span" style="color: black;"></span><br /> <span class="Apple-style-span" style="color: black;"><div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">The suggestions, that the extraterrestrials are almost certain to exist, come in a new documentary series for the Discovery channel, in which Dr. Hawking will set out his latest thinking on some of the universe's greatest mysteries. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">Alien life, he will suggest, is almost certain to exist in many other parts of the universe — not just in planets, but perhaps in the centre of stars or even floating in interplanetary space, T he Sunday Times reported. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">His logic on aliens is unusually simple. The universe, he points out, has 100 billion galaxies, each containing hundreds of millions of stars. In such a big place, Earth is unlikely to be the only planet where life has evolved. </span></div> </span></span></strong></span></div> </span><span class="Apple-style-span" style="color: black;"><div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">“To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like,” the 68-year-old was quoted as saying. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">The answer, Dr. Hawking suggests, is that most of it will be the equivalent of microbes or simple animals — the sort of life that has dominated Earth for most of its history. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">One scene in his documentary shows shoals of fluorescent animals living under thick ice on Europa, one of Jupiter's moons, while another shows flying yellow predators prey on two-legged herbivores. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">Such scenes are speculative, but Dr. Hawking uses them to lead on to a serious point — that a few life forms could be intelligent and pose a threat. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">He believes that contact with such a species could be devastating for humanity, and suggests that aliens might raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet. </span></div> </span></span></strong></span></div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"></span></span></strong></span><br /> <span class="Apple-style-span" style="font-size: small;"><strong><span class="Apple-style-span" style="font-size: x-large;"><span class="Apple-style-span" style="color: silver; font-size: 13px; font-weight: normal;"><div style="display: inline !important;"> <span class="Apple-style-span" style="color: black;">“I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”</span></div> </span></span></strong></span></div> </span></div> </strong></div>

STEPHEN HAWKING : ALIENS EXIST !

STEPHEN HAWKING : ALIENS EXIST ! London: Do aliens exist? They do, but humans should try to avoid any contact with t...

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VAST UNIVERSE

<div dir="ltr" style="text-align: left;" trbidi="on"> Until the invention of the telescopeastronomers believed that the universe consisted of a few planetsand the 6000 or so stars they could see with the naked eye. When the telescopebecame available tothem they were amazedto see thatthere were millions of stars in the heavens. In 1785 the German-born English astronomer William Herschel came to the conclusion that our solar system was at the centre of a vast conglomeration of stars which were arranged in the shape of a lens. He estimated that the diameter of the universe was 7,500 light - years. Over the next few centuries European and American astronomers worked doggedly to advance man's knowledge of the universe and by 1920 we knew this much : we were located not at the centre but at the edge of a disc- shaped galaxy. We had two star systems -- the Large Magellanic Cloud and the Small Magellanic Cloud -- as neighbours. This 'universe' was less than 20,000 light-years in diameter. Scientists wondered if that was all there was to the universe. In 1924 the American astronomer, Edwin Hubble found that there was much, much more to it. He discovered that we were not alone,that there were other galaxies besides our own. In 1929 he made the astonishing suggestion that the galaxies were flying away from each other at tremendous speeds. The farthera galaxy, the fasterit moved. Today we know that some of the galaxies are flying away at speeds comparable to the speed of light! So this is the picture we have of the universe now -- a universe thatis perhaps hundreds of millions of light-years in diameter -- and expanding all the while</div>

VAST UNIVERSE

Until the invention of the telescopeastronomers believed that the universe consisted of a few planetsand the 6000 or so stars they could se...

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MY WORLD OF SCIENCE AND FANTASY

<div dir="ltr" style="text-align: left;" trbidi="on"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;"></span><br /> <div> <a href="http://peperonity.com/go/media/13048690%213" style="color: blue; outline-color: initial; outline-style: initial; outline-width: 0px; text-decoration: none;"><img alt="MY WORLD OF SCIENCE AND FANTASY" hspace="0" src="http://f1.pepst.com/c/FF4351/510779/ssc3/home/039/physics.subha/06032010408_002.jpg_480_480_0_64000_0_1_0.jpg" vspace="0" /></a></div> <div> <div class="space2" style="padding-bottom: 0.5em; padding-top: 0.5em;"> <div class="hr" style="border-top-color: rgb(170, 170, 170); border-top-style: solid; border-top-width: 1px; color: #aaaaaa;"> <span></span></div> </div> </div> <div> WEAK ANTHROPIC PRINCIPLE<br /><br />One may wonder but it is a certified fact that if the basic laws of Universe were just slightly different, like the change in value of the fundamental constants of the basic physical constants then it was not possible for life to grow in. As if the Universe has already know that life is coming into existence and for that purpose he fine tuned the basic laws of the universe. This theme about Universe is known as Anthropic Principle. It is true that science can not explain the cause of our existence and the existence of our Universe? Are we some special purpose machine? Is there any Grand Design behind the creation of this Universe.<br /><br />The question that arise here is also very fundamental. So, why is the universe just right for life. Since the beginning of human civilisations the great question that haunts human being forever is the question about our Existence, our entity. Why do we exist? And why does the universe exist? From where our universe has been created or what is mass of any matter that exist in this physical world.<br /><br />When I was a school student I used to think that everything has an answer. Some one or other must know the answer. We don't know the answer of a certain comment, solely because we didn't study enough, and when we got physics for the first time in class VIII, believe me I thought now I come to know what is matter itself. But, alas, while studying Physics I amazingly find that not only matter, also we could not define what is time and length(space) even.<br /><br />KANAI SIR AND PHYSICS :<br /><br />I was completely indebted to the great teacher, kanai sir, who had infused a sense of scientific curiosity inside my little mind. He introduced physics as a law of nature and still now, when I am an university teacher, I honestly try to infuse the zeal once he had injected in me. Particular one incident I still remember, at that time I was in class VII, and for the first time we come to know about Rutherford model of atomic nucleas. Well, at first he introduced charge as a fundamental property of matter and next he told them the nucleus is made of several protons and around which electrons are orbitting, like planets are revolving around Sun, and both electrons and protons are charged particles, but their charges are opposite to each other.</div> </div>

MY WORLD OF SCIENCE AND FANTASY

WEAK ANTHROPIC PRINCIPLE One may wonder but it is a certified fact that if the basic laws of Universe were just slightly differen...

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UNIVERSE : SOME FACTS

<div dir="ltr" style="text-align: left;" trbidi="on"> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;"></span><br /> <div> <div> <strong>UNIVERSE : SOME FACTS</strong></div> </div> <div> <div> COSMOLOGY</div> </div> <div> <a href="http://peperonity.com/go/media/13816514%213" style="color: blue; outline-color: initial; outline-style: initial; outline-width: 0px; text-decoration: underline;"><img alt="UNIVERSE : SOME FACTS - hst keyhole nebula" hspace="0" src="http://f0.pepst.com/c/33B4D5/944057/ssc3/home/039/physics.subha/hst_keyhole_nebula.jpg_480_480_0_64000_0_1_0.jpg" vspace="0" /></a></div> <div> <div class="space2" style="padding-bottom: 0.5em; padding-top: 0.5em;"> <div class="hr" style="border-top-color: rgb(170, 170, 170); border-top-style: solid; border-top-width: 1px; color: #aaaaaa;"> <span></span></div> </div> </div> <div> INTRODUCTION :<br /><br />To us universe is the representation of eternity. Although in formal mathematics we use the concept of infinity but we can't yet define infinity accurately, all the definition of infinity just partially fulfilled the concept. The most important of all is the news that although it may look like that universe is finite but it is unbounded like the surface of a sphere. If so universe is seamless in that case, but like other theories of cosmology, it is also speculative and hence a hypothesis.<br /><br />THE UNIVERSE :<br /><br />The Universe comprises everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term "Universe" may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature.<br /><br />THE PARADOX :<br /><br />Astronomical observations indicate that the age of the Universe is 13.73 (± 0.12) billion years approximately, and that the diameter of the observable Universe is at least 93 billion light years, or 8.80 × 10²⁶ metres. But along with it a paradox also appears, as two galaxies that are on the opposite side separated by 93 billion light years it means a beam of light from one side of the Universe to reach the other side of the universe needs 93 bn years, but it also means that the faraway galaxies had travelled nearly 46 bn light years in seemingly inadequate nearly 13.73 bn years as those galaxies have come from the big bang explosion, it indicates one more case of FTL faster than light travel. So can space violate the speed limits of theory of relativity?<br /><br />ORIGIN OF UNIVERSE :<br /><br />According to the prevailing scientific model of the Universe, known as the Big Bang, the Universe expanded from an extremely hot, dense phase called the Planck epoch, in which all the matter and energy of the observable Universe was concentrated. Since the Planck epoch, the Universe has been expanding to its present form, possibly with a brief period (less than 10<super>−32</super> seconds) of cosmic inflation. Several independent experimental measurements support this theoretical expansion and, more generally, the Big Bang theory.<br /><br />Recent observations indicate that this expansion is accelerating because of the dark energy, and that most of the matter and energy in the Universe is fundamentally different from that observed on Earth and not directly observable. The imprecision of current observations has hindered predictions of the ultimate fate of the Universe.<br /><br />Experiments and observations suggest that the Universe has been governed by the same physical laws and constants throughout its extent and history. The dominant force at cosmological distances is gravity, and general relativity is currently the most accurate theory of gravitation. The remaining three fundamental forces and all the known particles on which they act are described by the Standard Model of particle physics. The Universe has at least three dimensions of space and one of time, although extremely small additional dimensions cannot be ruled out experimentally. Spacetime appears to be smooth and simply connected, and space has very small mean curvature, so that Euclidean geometry is accurate on the average throughout the Universe. Conversely, on a quantum scale spacetime is highly turbulent.<br /><br />ALTERNATIVE THEORIES :<br /><br />The word Universe is usually defined as encompassing everything. However, using an alternate definition, some have speculated that this "Universe" is just one of many disconnected "universes", which are collectively denoted as the multiverse. For example, in Bubble universe theory, there are an infinite variety of "universes", each with different physical constants. Similarly, in the many-worlds hypothesis, new "universes" are spawned with every quantum measurement. These universes are usually thought to be completely disconnected from our own and therefore impossible to detect experimentally.<br /><br />EVOLUTION OF COSMOLOGY :<br /><br />Throughout recorded history, several cosmologies and cosmogonies have been proposed to account for observations of the Universe. The earliest quantitative geocentric models were developed by the ancient Greeks, who proposed that the Universe possesses infinite space and has existed eternally, but contains a single set of concentric spheres of finite size – corresponding to the fixed stars, the Sun and various planets – rotating about a spherical but unmoving Earth. Over the centuries, more precise observations and improved theories of gravity led to Copernicus' heliocentric model and the Newtonian model of the Solar System, respectively. Further improvements in astronomy led to the characterization of the Milky Way, and the discovery of other galaxies and the microwave background radiation; careful studies of the distribution of these galaxies and their spectral lines have led to much of modern cosmology. </div> </div>

UNIVERSE : SOME FACTS

UNIVERSE : SOME FACTS COSMOLOGY INTRODUCTION : To us universe is the representation of eternity. Although in formal mathe...

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STEPHEN HAWKING : Warp of Space-time

<div dir="ltr" style="text-align: left;" trbidi="on"> <span class="Apple-style-span" style="border-collapse: collapse; color: silver; font-family: Arial; font-size: 13px; line-height: 22px;"></span><br /> <div> <a href="http://peperonity.com/go/media/13347980%213" style="outline-color: initial; outline-style: initial; outline-width: 0px; text-decoration: underline;"><span class="Apple-style-span" style="color: black;"><img alt="STEPHEN HAWKING : Warp of Space-time - hawkings" hspace="0" src="http://f1.pepst.com/c/A88CC3/584771/ssc3/home/032/blog.subha/hawkings.gif_480_480_0_64000_0_1_0.gif" vspace="0" /></span></a></div> <div> <div class="space2" style="padding-bottom: 0.5em; padding-top: 0.5em;"> <div class="hr" style="border-top-color: rgb(170, 170, 170); border-top-style: solid; border-top-width: 1px;"> <span class="Apple-style-span" style="color: black;"><span></span></span></div> </div> </div> <div> <span class="Apple-style-span" style="color: black;">||| THE BEGINNING OF TIME |||<br /><br />In this article, we would like to discuss whether TIME itself has a beginning, and whether it will have an end....<br />| ||| | ||| | ||| | ||| | ||| | ||| | ||| | ||| | ||| |<br />All the evidence seems to indicate, that the universe has not existed forever, but that it had a beginning, about 15 billion years ago. This is probably the most remarkable discovery of modern cosmology. Yet it is now taken for granted. We are not yet certain whether our Universe will have an end!<br />| ||||||||||| | |||||||||||| | ||||||||||| | |||||||||||| |<br />The time scale of the universe is very long compared to that for human life. It was therefore not surprising that until recently, the universe was thought to be essentially static, and unchanging in time. On the other hand, it must have been obvious, that society is evolving in culture and technology. This indicates that the present phase of human history can not have been going for more than a few thousand years. Otherwise, we would be more advanced than we are. It was therefore natural to believe that the human race, and maybe the whole universe, had a beginning in the fairly recent past. However, many people were unhappy with the idea that the universe had a beginning, because it seemed to imply the existence of a supernatural being who created the universe. They preferred to believe that the universe, and the human race, had existed forever. Their explanation for human progress was that there had been periodic floods, or other natural disasters, which repeatedly set back the human race to a primitive state.<br /><br />This argument about whether or not the universe had a beginning, persisted into the 19th and 20th centuries. It was conducted mainly on the basis of theology and philosophy, with little consideration of observational evidence. This may have been reasonable, given the notoriously unreliable character of cosmological observations, until fairly recently. The cosmologist, Sir Arthur Eddington, once said, 'Don't worry if your theory doesn't agree with the observations, because they are probably wrong.' But if your theory disagrees with the Second Law of Thermodynamics, it is in bad trouble. In fact, the theory that the universe has existed forever is in serious difficulty with the Second Law of Thermodynamics. The Second Law, states that disorder always increases with time. Like the argument about human progress, it indicates that there must have been a beginning. Otherwise, the universe would be in a state of complete disorder by now, and everything would be at the same temperature. In an infinite and everlasting universe, every line of sight would end on the surface of a star. This would mean that the night sky would have been as bright as the surface of the Sun. The only way of avoiding this problem would be if, for some reason, the stars did not shine before a certain time.<br /><br />In a universe that was essentially static, there would not have been any dynamical reason,why the stars should have suddenly turned on, at some Time. Any such "lighting up time" would have to be imposed by an intervention from outside the universe. The situation was different,however, when it was realized that the universe is not static, but expanding. Galaxies are moving steadily apart from each other. This means that they were closer together in the past. One can plot the separation of two galaxies, as a function of time. If there were no acceleration due to gravity, the graph would be a straight line. It would go down to zero separation, about twenty billion years ago. One would expect gravity, to cause the galaxies to accelerate towards each other. This will mean that the graph of the separation of two galaxies will bend downwards, below the straight line. So the time of zero separation, would have been less than twenty billion years ago.<br />At this time, the Big Bang, all the matter in the universe, would have been on top of itself. The density would have been infinite. It would have been what is called, a singularity. At a singularity, all the laws of physics would have broken down. This means that the state of the universe, after the Big Bang, will not depend on anything that may have happened before, because the deterministic laws that govern the universe will break down in the Big Bang. The universe will evolve from the Big Bang, completely independently of what it was like before. Even the amount of matter in the universe, can be different to what it was before the Big Bang, as the Law of Conservation of Matter, will break down at the Big Bang.<br />Since events before the Big Bang have no observational consequences, one may as well cut<br />them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them. This kind of beginning to the universe, and of time itself, is very different to the beginnings that had been considered earlier. These had to be imposed on the universe by some external agency. There is no dynamical reason why the motion of bodies in the solar system can not be extrapolated back in time, far beyond four thousand and four BC, the date for the creation of the universe, according to the book of Genesis. Thus it would require the direct intervention of God, if the universe began at that date. By contrast, the Big Bang is a beginning that is required by the dynamical laws that govern the universe. It is therefore intrinsic to the<br />universe, and is not imposed on it from outside.<br />Although the laws of science seemed to predict the universe had a beginning, they also seemed to predict that they could not determine how the universe would have begun. This was obviously very unsatisfactory. So there were a number of attempts to get round the conclusion, that there was a singularity of infinite density in the past. One suggestion was to modify the law of gravity, so that it became repulsive. This could lead to the graph of the separation between two galaxies, being a ..curve that approached zero, but didn't actually pass through it, at any finite time in the past. Instead, the idea was that, as the galaxies moved apart, new galaxies were formed in between, from matter that was supposed to be continually created. This was the Steady State theory, proposed by Bondi, Gold, and Hoyle. </span></div> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;"><br />The Steady State theory, was what Karl Popper would call, a good scientific theory: it made<br />definite predictions, which could be tested by observation, and possibly falsified. Unfortunately<br />for the theory, they were falsified. The first trouble came with the Cambridge observations, of<br />the number of radio sources of different Strengths. On average, one would expect that the<br />fainter sources would also be the more distant. One would therefore expect them to be more numerous than bright sources, which would tend to be near to us. However, the graph of the number of radio sources, against there strength, went up much more sharply at low source strengths, than the Steady State theory predicted.<br />There were attempts to explain away this number count graph, by claiming that some of the faint radio sources, were within our own galaxy, and so did not tell us anything about cosmology. This argument didn't really stand up to further observations. But the final nail in the coffin of the Steady State theory came with the discovery of the microwave background radiation, in 1965. This radiation is the same in all directions. It has the spectrum of radiation in thermal equilibrium at a temperature of 2 point 7 degrees above the Absolute Zero of temperature. There doesn't seem any way to explain this radiation in the Steady State theory.<br />Another attempt to avoid a beginning to time, was the suggestion, that maybe all the galaxies<br />didn't meet up at a single point in the past. Although on average, the galaxies are moving<br />apart from each other at a steady rate, they also have small additional velocities, relative to<br />the uniform expansion. These so-called "peculiar velocities" of the galaxies, may be directed<br />sideways to the main expansion. It was argued, that as you plotted the position of the galaxies<br />back in time, the sideways peculiar velocities, would have meant that the galaxies wouldn't<br />have all met up. Instead, there could have been a previous contracting phase of the universe,<br />in which galaxies were moving towards each other. The sideways velocities could have meant that the galaxies didn't collide, but rushed past each other, and then started to move apart.There wouldn't have been any singularity of infinite density, or any breakdown of the laws of physics. Thus there would be no necessity for the universe, and time itself, to have a beginning. Indeed, one might suppose that the universe had oscillated, though that still wouldn't solve the problem with the Second Law of Thermodynamics: one would expect that the universe would become more disordered each oscillation. It is therefore difficult to see how the universe could have been oscillating for an infinite time. This possibility, that the galaxies would have missed each other, was supported by a paper by two Russians. They claimed that there would be no singularities in a solution of the field equations of general relativity, which was fully general, in the sense that it didn't have any exact symmetry. However, their claim was proved wrong. These showed that general relativity predicted singularities, whenever more than a certain amount of mass was present in a region. The first theorems were designed to show that time came to an end, inside a black hole, formed by the collapse of a star. However, the expansion of the universe, is like the time reverse of the collapse of a star.I therefore want to show you, that observational evidence indicates the universe contains sufficient matter, that it is like the time reverse of a black hole, and so contains a singularity.In order to discuss observations in cosmology, it is helpful to draw a diagram of events in space and time, with time going upward, and the space directions horizontal. To show this diagram properly, I would really need a four dimensional screen.As we look out at the universe, we are looking back in time, because light had to leave distant objects a long time ago, to reach us at the present time. This means that the events we observe lie on what is called our past light cone. The point of the cone is at our position, at the present time. As one goes back in time on the diagram, the light cone spreads out to greater distances, and its area increases. However, if there is sufficient matter on our past light cone, it will bend the rays of light towards each other. This will mean that, as one goes back into the past, the area of our past light cone will reach a maximum, and then start to decrease. It is this focusing of our past light cone, by the gravitational effect of the matter in the universe,that is the signal that the universe is within its horizon, like the time reverse of a black hole. If one can determine that there is enough matter in the universe, to focus our past light cone, One can then apply the singularity theorems, to show that time must have a beginning.<br />How can we tell from the observations, whether there is enough matter on our past light cone,<br />to focus it? We observe a number of galaxies, but we can not measure directly how much<br />matter they contain. Nor can we be sure that every line of sight from us will pass through a<br />galaxy. So I will give a different argument, to show that the universe contains enough matter,<br />to focus our past light cone. The argument is based on the spectrum of the microwave<br />background radiation. This is characteristic of radiation that has been in thermal equilibrium,<br />with matter at the same temperature. To achieve such an equilibrium, it is necessary for the<br />radiation to be scattered by matter, many times. For example, the light that we receive from<br />the Sun has a characteristically thermal spectrum. This is not because the nuclear reactions,<br />which go on in the centre of the Sun, produce radiation with a thermal spectrum. Rather, it is<br />because the radiation has been scattered, by the matter in the Sun, many times on its way<br />from the centre.<br /><br />In the case of the</span><span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;">universe, the fact that the microwave background has such an exactly </span><br /> <span class="Apple-style-span" style="border-collapse: collapse; font-family: Arial; font-size: 13px; line-height: 22px;">thermal spectrum indicates that it must have been scattered many times. The universe must<br />therefore contain enough matter, to make it opaque in every direction we look, because the<br />microwave background is the same, in every direction we look. Moreover, this opacity must<br />occur a long way away from us, because we can see galaxies and quasars, at great distances.<br />Thus there must be a lot of matter at a great distance from us. The greatest opacity over a<br />broad wave band, for a given density, comes from ionised hydrogen. It then follows that if<br />there is enough matter to make the universe opaque, there is also enough matter to focus our<br />past light cone. One can then apply the theorem of Penrose and myself, to show that time<br />must have a beginning.<br /><br />The focussing of our past light cone implied that time must have a beginning, if the General<br />Theory of relativity is correct. But one might raise the question, of whether General Relativity<br />really is correct. It certainly agrees with all the observational tests that have been carried out.<br />However these test General Relativity, only over fairly large distances. We know that General<br />Relativity can not be quite correct on very small distances, because it is a classical theory. This<br />means, it doesn't take into account, the Uncertainty Principle of Quantum Mechanics, which<br />says that an object can not have both a well defined position, and a well defined speed: the<br />more accurately one measures the position, the less accurately one can measure the speed,<br />and vice versa. Therefore, to understand the very high-density stage, when the universe was<br />very small, one needs a quantum theory of gravity, which will combine General Relativity with<br />the Uncertainty Principle.<br /><br />Many people hoped that quantum effects, would somehow smooth out the singularity of infinite<br />density, and allow the universe to bounce, and continue back to a previous contracting phase.<br />This would be rather like the earlier idea of galaxies missing each other, but the bounce would<br />occur at a much higher density. However, I think that this is not what happens: quantum<br />effects do not remove the singularity, and allow time to be continued back indefinitely. But it<br />seems that quantum effects can remove the most objectionable feature, of singularities in<br />classical General Relativity. This is that the classical theory, does not enable one to calculate<br />what would come out of a singularity, because all the Laws of Physics would break down there.<br />This would mean that science could not predict how the universe would have begun. Instead,<br />one would have to appeal to an agency outside the universe. This may be why many religious<br />leaders, were ready to accept the Big Bang, and the singularity theorems.<br /><br />It seems that Quantum theory, on the other hand, can predict how the universe will begin.<br />Quantum theory introduces a new idea, that of imaginary time. Imaginary time may sound like<br />science fiction, and it has been brought into Doctor Who. But nevertheless, it is a genuine<br />scientific concept. One can picture it in the following way. One can think of ordinary, real, time<br />as a horizontal line. On the left, one has the past, and on the right, the future. But there's<br />another kind of time in the vertical direction. This is called imaginary time, because it is not the<br />kind of time we normally experience. But in a sense, it is just as real, as what we call real<br />time.<br /><br />The three directions in space, and the one direction of imaginary time, make up what is called<br />a Euclidean space-time. I don't think anyone can picture a four dimensional curve space. But it<br />is not too difficult to visualise a two dimensional surface, like a saddle, or the surface of a<br />football.<br /><br />In fact, James Hartle of the University of California Santa Barbara, and I have proposed that<br />space and imaginary time together, are indeed finite in extent, but without boundary. They<br />would be like the surface of the Earth, but with two more dimensions. The surface of the Earth<br />is finite in extent, but it doesn't have any boundaries or edges. I have been round the world,<br />and I didn't fall off.<br /><br />If space and imaginary time are indeed like the surface of the Earth, there wouldn't be any<br />singularities in the imaginary time direction, at which the laws of physics would break down.<br /><br />And there wouldn't be any boundaries, to the imaginary time space-time, just as there aren't<br />any boundaries to the surface of the Earth. This absence of boundaries means that the laws of<br />physics would determine the state of the universe uniquely, in imaginary time. But if one<br />knows the state of the universe in imaginary time, one can calculate the state of the universe<br />in real time. One would still expect some sort of Big Bang singularity in real time. So real time<br />would still have a beginning. But one wouldn't have to appeal to something outside the<br />universe, to determine how the universe began. Instead, the way the universe started out at<br />the Big Bang would be determined by the state of the universe in imaginary time. Thus, the<br />universe would be a completely self-contained system. It would not be determined by anything<br />outside the physical universe, that we observe.<br /><br />The no boundary condition, is the statement that the laws of physics hold everywhere. Clearly,<br />this is something that one would like to believe, but it is a hypothesis. One has to test it, by<br />comparing the state of the universe that it would predict, with observations of what the<br />universe is actually like. If the observations disagreed with the predictions of the no boundary<br />hypothesis, we would have to conclude the hypothesis was false. There would have to be<br />something outside the universe, to wind up the clockwork, and set the universe going. Of<br />course, even if the observations do agree with the predictions, that does not prove that the no<br />boundary</span><span class="Apple-style-span" style="font-family: Arial; font-size: 13px; line-height: 22px;">...proposal is correct. But one's confidence in it would be increased, particularly<br />because there doesn't seem to be any other natural proposal, for the quantum state of the<br />universe.<br /><br />The no boundary proposal, predicts that the universe would start at a single point, like the<br />North Pole of the Earth. But this point wouldn't be a singularity, like the Big Bang. Instead, it<br />would be an ordinary point of space and time, like the North Pole is an ordinary point on the<br />Earth, or so I'm told. I have not been there myself.<br /><br />According to the no boundary proposal, the universe would have expanded in a smooth way<br />from a single point. As it expanded, it would have borrowed energy from the gravitational field,<br />to create matter. As any economist could have predicted, the result of all that borrowing, was<br />inflation. The universe expanded and borrowed at an ever-increasing rate. Fortunately, the<br />debt of gravitational energy will not have to be repaid until the end of the universe.<br /><br />Eventually, the period of inflation would have ended, and the universe would have settled down<br />to a stage of more moderate growth or expansion. However, inflation would have left its mark<br />on the universe. The universe would have been almost completely smooth, but with very slight<br />irregularities. These irregularities are so little, only one part in a hundred thousand, that for<br />years people looked for them in vain. But in 1992, the Cosmic Background Explorer satellite,<br />COBE, found these irregularities in the microwave background radiation. It was an historic<br />moment. We saw back to the origin of the universe. The form of the fluctuations in the<br />microwave background agree closely with the predictions of the no boundary proposal. These<br />very slight irregularities in the universe would have caused some regions to have expanded<br />less fast than others. Eventually, they would have stopped expanding, and would have<br />collapsed in on themselves, to form stars and galaxies. Thus the no boundary proposal can<br />explain all the rich and varied structure, of the world we live in. What does the no boundary<br />proposal predict for the future of the universe? Because it requires that the universe is finite in<br />space, as well as in imaginary time, it implies that the universe will re-collapse eventually.<br />However, it will not re-collapse for a very long time, much longer than the 15 billion years it<br />has already been expanding. So, you will have time to sell your government bonds, before the<br />end of the universe is nigh. Quite what you invest in then, I don't know.<br /><br />Originally, I thought that the collapse, would be the time reverse of the expansion. This would<br />have meant that the arrow of time would have pointed the other way in the contracting phase.<br />People would have gotten younger, as the universe got smaller. Eventually, they would have<br />disappeared back into the womb.<br /><br />However, I now realise I was wrong, as these solutions show. The collapse is not the time<br />reverse of the expansion. The expansion will start with an inflationary phase, but the collapse<br />will not in general end with an anti inflationary phase. Moreover, the small departures from<br />uniform density will continue to grow in the contracting phase. The universe will get more and<br />more lumpy and irregular, as it gets smaller, and disorder will increase. This means that the<br />arrow of time will not reverse. People will continue to get older, even after the universe has<br />begun to contract. So it is no good waiting until the universe re-collapses, to return to your<br />youth. You would be a bit past it, anyway, by then.<br /><br />The conclusion of this lecture is that the universe has not existed forever. Rather, the universe,<br />and time itself, had a beginning in the Big Bang, about 15 billion years ago. The beginning of<br />real time, would have been a singularity, at which the laws of physics would have broken<br />down. Nevertheless, the way the universe began would have been determined by the laws of<br />physics, if the universe satisfied the no boundary condition. This says that in the imaginary<br />time direction, space-time is finite in extent, but doesn't have any boundary or edge. The<br />predictions of the no boundary proposal seem to agree with observation. The no boundary<br />hypothesis also predicts that the universe will eventually collapse again. However, the contracting phase, will not have the opposite arrow of time, to the expanding phase. So we will<br />keep on getting older, and we won't return to our youth. Because time is not going to go<br />backwards, I think I better stop now</span></div>

STEPHEN HAWKING : Warp of Space-time

||| THE BEGINNING OF TIME ||| In this article, we would like to discuss whether TIME itself has a beginning, and whether it will ...

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