Introduction to Theoretical Time Travel

Time-Travel is easy.  All of us do it every day.  But only in one direction.  For thousands of years,scientists  and  philosophers  have  talked  of  time  as  a  "river  that  flows  steadily  onward  year-after-year". But  what  if  there  were  a  way  to  swim  against  the  flow?    Or  to  run  down  the  bank  ahead  of  the  river? Might we might be able to journey back-and-forth in time just as we travel through space.  The idea is not as far-fetched as it sounds.  And the implications for the future are intriguing. 

Super-Science , NOT Fantasy!

Ever  since  Einstein,  scientists  have  considered  time  and  3-dimensional  space  not  as  2  different things  but  as  different  aspects  of  a  4-dimensional  "space-time".    Quantum  physicists(who  study  the world of subatomic particles) often find it easier to explain events by assuming time runs  backward as well as forward despite however much it defies common sense.

At the other extreme, cosmologists looking at the Universe on a grand scale have found that  space and  time  can  be  warped  by  gravity  and speed.    Back  in  the  1940s,  German mathematician  Kurt Goedel  proved  that  if  we could  warp  and  twist  space-time  enough creating  what  he  called  "Closed, Time-like Curves (CTC)" -- then we could bore tunnels through time itself.  But no one knew how to do the twisting.  Until black holes.

The gravitational pull of a black hole is so enormous that it distorts the very fabric of space-time into what is called a  singularity.  When singularities were found to spin, it was proved that Closed, Time-like Curves not only can occur -- they MUST occur!  The singularity forms a doughnut shape in space-time while the hole in the middle is a perilous gateway to somewhere -- or when.

3 Ways to Travel in Time Without Breaking the Rules 

Wormhole-artist depiction

1.  Wormholes

Since the 1930s, physicists have speculated about the existence of "wormholes" in the fabric of space.  Wormholes are essentially gateway between different parts of the Universe and are made by  linking  a  pair  of  black  holes. This  effectively  creates  a  tunnel  through  time  and  space: a traveler entering at one end would exit the other at a different time as well as a different place.

Kip Thorne

The difficulty likes in keeping the wormhole open while the traveler makes his journey.  If the opening  snaps  shut,  he  will  never  survive  to  emerge  at  the  other  end.    For  years,  scientists believed  that  the  transit  was  physically  impossible.    But  recent  research  especially  the  U.S. physicist  Kip  Thorne  --  suggest  that  it  could  be  done  using  exotic  materials  capable  of withstanding the immense forces involved.  Even then, the time machine would be of limited use.

For  example,  you  could  not  return  to  a  time  before  the  wormhole  was  created. Using wormhole  technology  would  also  require  a  society so  technologically  advanced  that  it  could master and exploit the energy within black holes.  But the trip would  NOT be impossible -- just very, very difficult!   

2.Rotating cylinder

Frank Tipler

Civilizations  with  the  technology  to  harness  black  holes  might  be  better  advised  to  leave wormholes and try the time-warp method suggested by U.S. astronomer Frank Tipler.  He has a simple  recipe  for  a  time  machine.

First,  take  a  piece  of  material  10  times  the  mass  of  the  Sun. Then squeeze it together and roll it into a long, thin, super-dense cylinder (a bit like a black hole that has passed through a spaghetti factor). Lastly, spin this cylinder at a few billion revolutions-per-minute and see what happens. 

Tipler predicts that a ship following a carefully plotted spiral course around the cylinder would immediately  find  itself  on  a  "Closed, Time-like  Curve".    It  would  emerge  thousand  --  even  billions -- of years from its starting point and possibly several galaxies away.

There are problems, though.  For the mathematics to work properly, Tipler's cylinder has to be infinitely long.  Also, odd things happen near the ends, and you need to steer well clear of them in your time-ship.  However, if  you make the device as long as  you can and stick  to paths close to the middle of the cylinder, you should survive the trip!

3.  Cosmic Strings 

Cosmic strings- An artist view

As a variation on the rotating cylinder, some scientists have suggest using "cosmic strings" to construct a time machine.  At the moment, these are purely theoretical objects that might possibly be left over from the creation of the Universe in the Big Bang.

A  black  hole  contains  a  one-dimensional  singularity  --  an  infinitely  small  point  in  the  space-time continuum. A cosmic string, if such a thing existed, would be a 2-dimensional singularity an infinitely thin line that has even stranger effects on the fabric of space and time.

Although no one has actually found a cosmic string, astronomers have suggested that they may  explain  strange  effects  seen  in  distant  galaxies. By  maneuvering  two  cosmic  strings  close together  --  or  possibly  just  one  string  plus  a  black  hole  --  it  is  theoretically  possible  to  create  a  whole array of "closed timelike curves".  Your best bet is to fire two infinitely long cosmic strings  past  each  other  at  very  high  speeds,  then  fly  your  ship  around  them  in  a  carefully  calculated  figure-eight.  In theory, you would be able to emerge anywhere, anytime! 

What If Tourists From the Future Could Visit Us ? 

 If  time  machines  are  possible,  it is  likely  that  someone  in  the  Future  will  already  have  constructed
one.    After  all,  in  the  Future  there  is  time  to  complete  even  the  largest  engineering  project!    Even  if  humans  are  not  up  to  the  task,  creatures  from  other  planets  may  try.    So  why  are  we  not  overrun  by visitors from the Future?

This is the argument used by the famous English physicist Stephen Hawking in what he called his "Chronology Protection Conjecture".  Like many other scientists, Hawking is troubled by the weird paradoxes  of  time-travel.    He  argues  that  the  Universe  simply  couldn't  allow  time-travel  to  happen because its evolution since the Big Bang cannot be reversed.  If the Universe were to contract instead of expanding, asks Hawking, would human beings "un-evolve" in the same way as they have evolved over millions of years?

A second explanation for the absence of visitors envisaged so far lets the voyager go back before the moment the machine was first constructed.  So relax.  Since no one has built a time machine yet, out-of-time tourists are not a problem!

sources

 http://www.stealthskater.com/Science.htm

http://powerlisting.wikia.com/wiki/Cosmic_String_Manipulation 

The Physics of Extraterrestrial Civilizations-Michio Kaku

How advanced could they possibly be?

Carl Sagan

 The late Carl Sagan once asked this question, “What does it mean for a civilization to be a million years old? We have had radio telescopes and spaceships for a few decades; our technical civilization is a few hundred years old… an advanced civilization millions of years old is as much beyond us as we are beyond a bush baby or a macaque.”

Although any conjecture about such advanced civilizations is a matter of sheer speculation, one can still use the laws of physics to place upper and lower limits on these civilizations. In particular, now that the laws of quantum field theory, general relativity, thermodynamics, etc. are fairly well-established, physics can impose broad physical bounds which constrain the parameters of these civilizations.

This question is no longer a matter of idle speculation. Soon, humanity may face an existential shock as the current list of a dozen Jupiter-sized extra-solar planets swells to hundreds of earth-sized planets, almost identical twins of our celestial homeland. This may usher in a new era in our relationship with the universe: we will never see the night sky in the same way ever again, realizing that scientists may eventually compile an encyclopedia identifying the precise co-ordinates of perhaps hundreds of earth-like planets.

Today, every few weeks brings news of a new Jupiter-sized extra-solar planet being discovered, the latest being about 15 light years away orbiting around the star Gliese 876. The most spectacular of these findings was photographed by the Hubble Space Telescope, which captured breathtaking photos of a planet 450 light years away being sling-shot into space by a double-star system.

But the best is yet to come. Early in the next decade, scientists will launch a new kind of telescope, the interferome try space telescope, which uses the interference of light beams to enhance the resolving power of telescopes.

Artist concept of Space Interferometry Mission(SIM)

 For example, the Space Interferometry Mission (SIM), to be launched early in the next decade, consists of multiple telescopes placed along a 30 foot structure. With an unprecedented resolution approaching the physical limits of optics, the SIM is so sensitive that it almost defies belief: orbiting the earth, it can detect the motion of a lantern being waved by an astronaut on Mars!

The SIM, in turn, will pave the way for the Terrestrial Planet Finder, to be launched late in the next decade, which should identify even more earth-like planets. It will scan the brightest 1,000 stars within 50 light years of the earth and will focus on the 50 to 100 brightest planetary systems.

All this, in turn, will stimulate an active effort to determine if any of them harbor life, perhaps some with civilizations more advanced than ours.

Although it is impossible to predict the precise features of such advanced civilizations, their broad outlines can be analyzed using the laws of physics. No matter how many millions of years separate us from them, they still must obey the iron laws of physics, which are now advanced enough to explain everything from sub-atomic particles to the large-scale structure of the universe, through a staggering 43 orders of magnitude.

 

Physics of Type I, II, and III Civilizations

Specifically, we can rank civilizations by their energy consumption, using the following principles:

The second law also introduces Entropy-the energy of all matter and objects will decrease over time

The future of our world, type 1 civilization

1) The laws of thermodynamics. Even an advanced civilization is bound by the laws of thermodynamics, especially the Second Law, and can hence be ranked by the energy at their disposal.

Artistic concept of Type 2 civilization

2) The laws of stable matter. Baryonic matter (e.g. based on protons and neutrons) tends to clump into three large groupings: planets, stars and galaxies. (This is a well-defined by product of stellar and galactic evolution, thermonuclear fusion, etc.) Thus, their energy will also be based on three distinct types, and this places upper limits on their rate of energy consumption.

3) The laws of planetary evolution. Any advanced civilization must grow in energy consumption faster than the frequency of life-threatening catastrophes (e.g. meteor impacts, ice ages, supernovas, etc.). If they grow any slower, they are doomed to extinction. This places mathematical lower limits on the rate of growth of these civilizations.

In a seminal paper published in 1964 in the Journal of Soviet Astronomy, Russian astrophysicist Nicolai Kardashev theorized that advanced civilizations must therefore be grouped according to three types: Type I, II, and III, which have mastered planetary, stellar and galactic forms of energy, respectively. He calculated that the energy consumption of these three types of civilization would be separated by a factor of many billions. But how long will it take to reach Type II and III status?

Shorter than most realize.

Don Goldsmith

Berkeley astronomer Don Goldsmith reminds us that the earth receives about one billionth of the suns energy, and that humans utilize about one millionth of that. So we consume about one million billionth of the suns total energy. At present, our entire planetary energy production is about 10 billion billion ergs per second. But our energy growth is rising exponentially, and hence we can calculate how long it will take to rise to Type II or III status.

Goldsmith says, “Look how far we have come in energy uses once we figured out how to manipulate energy, how to get fossil fuels really going, and how to create electrical power from hydropower, and so forth; we’ve come up in energy uses in a remarkable amount in just a couple of centuries compared to billions of years our planet has been here … and this same sort of thing may apply to other civilizations.”

Freeman Dyson

Physicist Freeman Dyson of the Institute for Advanced Study estimates that, within 200 years or so, we should attain Type I status. In fact, growing at a modest rate of 1% per year, Kardashev estimated that it would take only 3,200 years to reach Type II status, and 5,800 years to reach Type III status. Living in a Type I,II, or III civilization

For example, a Type I civilization is a truly planetary one, which has mastered most forms of planetary energy. Their energy output may be on the order of thousands to millions of times our current planetary output. Mark Twain once said, ”Everyone complains about the weather, but no one does anything about it.“ This may change with a Type I civilization, which has enough energy to modify the weather. They also have enough energy to alter the course of earthquakes, volcanoes, and build cities on their oceans.

Currently, our energy output qualifies us for Type 0 status. We derive our energy not from harnessing global forces, but by burning dead plants (e.g. oil and coal). But already, we can see the seeds of a Type I civilization. We see the beginning of a planetary language (English), a planetary communication system (the Internet), a planetary economy (the forging of the European Union), and even the beginnings of a planetary culture (via mass media, TV, rock music, and Hollywood films).

By definition, an advanced civilization must grow faster than the frequency of life-threatening catastrophes. Since large meteor and comet impacts take place once every few thousand years, a Type I civilization must master space travel to deflect space debris within that time frame, which should not be much of a problem. Ice ages may take place on a time scale of tens of thousands of years, so a Type I civilization must learn to modify the weather within that time frame.

Artificial and internal catastrophes must also be negotiated. But the problem of global pollution is only a mortal threat for a Type 0 civilization; a Type I civilization has lived for several millennia as a planetary civilization, necessarily achieving ecological planetary balance. Internal problems like wars do pose a serious recurring threat, but they have thousands of years in which to solve racial, national, and sectarian conflicts.

Eventually, after several thousand years, a Type I civilization will exhaust the power of a planet, and will derive their energy by consuming the entire output of their suns energy, or roughly a billion trillion trillion ergs per second.

With their energy output comparable to that of a small star, they should be visible from space. Dyson has proposed that a Type II civilization may even build a gigantic sphere around their star to more efficiently utilize its total energy output. Even if they try to conceal their existence, they must, by the Second Law of Thermodynamics, emit waste heat. From outer space, their planet may glow like a Christmas tree ornament. Dyson has even proposed looking specifically for infrared emissions (rather than radio and TV) to identify these Type II civilizations.

Perhaps the only serious threat to a Type II civilization would be a nearby supernova explosion, whose sudden eruption could scorch their planet in a withering blast of X-rays, killing all life forms. Thus, perhaps the most interesting civilization is a Type III civilization, for it is truly immortal. They have exhausted the power of a single star, and have reached for other star systems. No natural catastrophe known to science is capable of destroying a Type III civilization.

Faced with a neighboring supernova, it would have several alternatives, such as altering the evolution of dying red giant star which is about to explode, or leaving this particular star system and terraforming a nearby planetary system.

However, there are roadblocks to an emerging Type III civilization. Eventually, it bumps up against another iron law of physics, the theory of relativity. Dyson estimates that this may delay the transition to a Type III civilization by perhaps millions of years.

But even with the light barrier, there are a number of ways of expanding at near-light velocities. For example, the ultimate measure of a rockets capability is measured by something called “specific impulse” (defined as the product of the thrust and the duration, measured in units of seconds). Chemical rockets can attain specific impulses of several hundred to several thousand seconds. Ion engines can attain specific impulses of tens of thousands of seconds. But to attain near-light speed velocity, one has to achieve specific impulse of about 30 million seconds, which is far beyond our current capability, but not that of a Type III civilization. A variety of propulsion systems would be available for sub-light speed probes (such as ram-jet fusion engines, photonic engines, etc.)

sources
http://mkaku.org/home/?page_id=246 
image sources
http://canspeccy.blogspot.in/2012/03/flake-fake-fantasist-or-shill-no-43.html 
http://scifi.wikia.com/wiki/Type_III_Civilizations 
http://www.maybusher.com/Comments.aspx?eID=13
http://sites.google.com/site/academicportfoliosite/Home/PHYSICS/Unit-4-Heat-and-Thermodynamics 
http://en.wikipedia.org/wiki/Space_Interferometry_Mission 
http://map.vbgood.com/space%20probe/space%20probe.htm 
http://diariodeunaolla.blogspot.in/2008/09/exoplanetas-i.html

The physics of Time Travel- Is it real or is it fable? Michhio Kaku

Michio kaku a renowned American theoretical physicist, author of New York times' best sellers Physics of the Impossible (2008) and Physics of the Future (2011). In this article he talks about time travel and time travel paradox by providing some interesting examples. Here is the article,enjoy reading.

In H.G. Wells’ novel, The Time Machine, our protagonist jumped into a special chair with blinking lights, spun a few dials, and found himself catapulted several hundred thousand years into the future, where England has long disappeared and is now inhabited by strange creatures called the Morlocks and Eloi. That may have made great fiction, but physicists have always scoffed at the idea of time travel, considering it to be the realm of cranks, mystics, and charlatans, and with good reason

However, rather remarkable advances in quantum gravity are reviving the theory; it has now become fair game for theoretical physicists writing in the pages of Physical Review magazine. One stubborn problem with time travel is that it is riddled with several types of paradoxes. For example, there is the paradox of the man with no parents, i.e. what happens when you go back in time and kill your parents before you are born? Question: if your parents died before you were born, then how could you have been born to kill them in the first place?

There is also the paradox of the man with no past. For example, let’s say that a young inventor is trying futilely to build a time machine in his garage. Suddenly, an elderly man appears from nowhere and gives the youth the secret of building a time machine. The young man then becomes enormously rich playing the stock market, race tracks, and sporting events because he knows the future. Then, as an old man, he decides to make his final trip back to the past and give the secret of time travel to his youthful self. Question: where did the idea of the time machine come from?

There is also the paradox of the man who is own mother (my apologies to Heinlein.) “Jane” is left at an orphanage as a foundling. When “Jane” is a teenager, she falls in love with a drifter, who abandons her but leaves her pregnant. Then disaster strikes. She almost dies giving birth to a baby girl, who is then mysteriously kidnapped. The doctors find that Jane is bleeding badly, but, oddly enough, has both sex organs. So, to save her life, the doctors convert “Jane” to “Jim.”

“Jim” subsequently becomes a roaring drunk, until he meets a friendly bartender (actually a time traveler in disguise) who wisks “Jim” back way into the past. “Jim” meets a beautiful teenage girl, accidentally gets her pregnant with a baby girl. Out of guilt, he kidnaps the baby girl and drops her off at the orphanage. Later, “Jim” joins the time travelers corps, leads a distinguished life, and has one last dream: to disguise himself as a bartender to meet a certain drunk named “Jim” in the past. Question: who is “Jane’s” mother, father, brother, sister, grand- father, grandmother, and grandchild?

 Not surprisingly, time travel has always been considered impossible. After all, Newton believed that time was like an arrow; once fired, it soared in a straight, undeviating line. One second on the earth was one second on Mars. Clocks scattered throughout the universe beat at the same rate. Einstein gave us a much more radical picture. According to Einstein, time was more like a river, which meandered around stars and galaxies, speeding up and slowing down as it passed around massive bodies. One second on the earth was Not one second on Mars. Clocks scattered throughout the universe beat to their own distant drummer.

However, before Einstein died, he was faced with an embarrassing problem. Einstein’s neighbor at Princeton, Kurt Goedel, perhaps the greatest mathematical logician of the past 500 years, found a new solution to Einstein’s own equations which allowed for time travel! The “river of time” now had whirlpools in which time could wrap itself into a circle. Goedel’s solution was quite ingenious: it postulated a universe filled with a rotating fluid. Anyone walking along the direction of rotation would find themselves back at the starting point, but backwards in time!

Einstein with Kurt Goedel

In his memoirs, Einstein wrote that he was disturbed that his equations contained solutions that allowed for time travel. But he finally concluded: the universe does not rotate, it ex- pands (i.e. as in the Big Bang theory) and hence Goedel’s solution could be thrown out for “physical reasons.” (Apparently, if the Big Bang was rotating, then time travel would be possible throughout the universe!)

Then in 1963, Roy Kerr, a New Zealand mathematician, found a solution of Einstein’s equations for a rotating black hole, which had bizarre properties. The black hole would not 

collapse to a point (as previously thought) but into a spinning ring (of neutrons). The ring would be circulating so rapidly that centrifugal force would keep the ring from collapsing under gravity. The ring, in turn, acts like the Looking Glass of Alice. Anyone walking through the ring would not die, but could pass through the ring into an alternate universe. Since then, hundreds of other “wormhole” solutions have been found to Einstein’s equations. These wormholes connect not only two regions of space (hence the name) but also two regions of time as well. In principle, they can be used as time machines.

Recently, attempts to add the quantum theory to gravity (and hence create a “theory of everything”) have given us some insight into the paradox problem. In the quantum theory, we can have multiple states of any object. For example, an electron can exist simultaneously in different orbits (a fact which is responsible for giving us the laws of chemistry). Similarly, Schrodinger’s famous cat can exist simultaneously in two possible states: dead and alive. So by going back in time and altering the past, we merely create a parallel universe. So we are changing someone ELSE’s past by saving, say, Abraham Lincoln from being assassinated at the Ford Theater, but our Lincoln is still dead. In this way, the river of time forks into two separate rivers. But does this mean that we will be able to jump into H.G. Wells’ machine, spin a dial, and soar several hundred thousand years into England’s future? No. There are a number of difficult hurdles to overcome.

First, the main problem is one of energy. In the same way that a car needs gasoline, a time machine needs to have fabulous amounts of energy. One either has to harness the power of a star, or to find something called “exotic” matter (which falls up, rather than down) or find a source of negative energy. (Physicists once thought that negative energy was impossible. But tiny amounts of negative energy have been experimentally verified for something called the Casimir effect, i.e. the energy created by two parallel plates). All of these are exceedingly difficult to obtain in large quantities, at least for several more centuries!

Then there is the problem of stability. The Kerr black hole, for example, may be unstable if one falls through it. Similarly, quantum effects may build up and destroy the wormhole before you enter it. Unfortunately, our mathematics is not powerful enough to answer the question of stability because you need a “theory of everything” which combines both quantum forces and gravity. At present, superstring theory is the leading candidate for such a theory (in fact, it is the ONLY candidate; it really has no rivals at all). But superstring theory, which happens to be my specialty, is still to difficult to solve completely. The theory is well-defined, but no one on earth is smart enough to solve it.

 

 Interestingly enough, Stephen Hawking once opposed the idea of time travel. He even claimed he had “empirical” evidence against it. If time travel existed, he said, then we would have been visited by tourists from the future. Since we see no tourists from the future, ergo: time travel is not possible. Because of the enormous amount of work done by theoretical physicists within the last 5 years or so, Hawking has since changed his mind, and now believes that time travel is possible (although not necessarily practical). (Furthermore, perhaps we are simply not very interesting to these tourists from the future. Anyone who can harness the power of a star would consider us to be very primitive. Imagine your friends coming across an ant hill. Would they bend down to the ants and give them trinkets, books, medicine, and power? Or would some of your friends have the strange urge to step on a few of them?)

 

In conclusion, don’t turn someone away who knocks at your door one day and claims to be your future great-great-great grandchild. They may be right.

sources

http://mkaku.org/home/?page_id=252 

about Michio Kaku-Wikipedia page

Stephen William Hawking's 70th Birthday speech

The most intelligent person in the world Stephen William Hawking turns 70 on 8th Jan 2012. He gives a speech to Cambridge university physicists, leading cosmologists.

A public symposium in Cambridge was told that, far from being top of the class, he was never more than half-way up. "My classwork was very untidy, and my handwriting was the despair of my teachers," he said. "But my classmates gave me the nickname Einstein, so presumably they saw signs of something better.

"When I was 12, one of my friends bet another friend a bag of sweets that I would never come to anything. I don't know if this bet was ever settled and, if so, which way it was decided."

Unable to attend the event in person due to ill health, Hawking sent a speech which marked the culmination of four days of birthday celebrations organised by his colleagues at Cambridge University. The festivities were attended by the world's leading cosmologists, including Nobel laureates Frank Wilczek and Saul Perlmutter, and celebrities including Richard Branson.

Hawking's laidback approach to education continued during his years studying physics at the University of Oxford. "I did one exam before I went up, then had three years at Oxford with just the final exams at the end," he said. "I once calculated that I did about a thousand hours' work in the three years I was there, an average of an hour a day. I'm not proud of this."

In his half-century career as a researcher, Hawking has been at the forefront of the understanding of black holes and quantum cosmology. His fame has also brought his ideas to a vast audience outside academia. His first book, A Brief History of Time, has reportedly sold more than 10m copies worldwide and he has made guest appearances on The Simpsons and Star Trek.

In the speech, Hawking spoke of his early life growing up in St Albans and gave the highlights of his scientific career. But his main message was to "be curious" and never give up, however difficult things might seem. "Remember to look up at the stars and not down at your feet," he said. "Try to make sense of what you see and about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do, and succeed at. It matters that you don't just give up."

Around the age of 21, as he started his PhD in Cambridge, Hawking was diagnosed with motor neurone disease. The first signs that something was wrong came after he fell over while ice-skating on a lake near his childhood home in St Albans.

"At first I became depressed. I seemed to be getting worse pretty rapidly. There didn't seem any point in working on my PhD because I didn't know I would live long enough to finish it."

After his expectations had been reduced to zero, he said, he was only emboldened when he met his future wife, Jane, at a party. "Getting engaged lifted my spirits and I realised, if we were going to get married, I had to do a job and finish my PhD. I began to work hard and I enjoyed it."

Other speakers in the public seminar at Cambridge University included Lord Rees, the astronomer royal, and Perlmutter, who won the Nobel prize in physics last year for the co-discovery of dark energy, the mysterious substance said to drive the expansion of the universe. Professor Kip Thorne, formerly of the California Institute of Technology and a longtime collaborator of Hawking, spoke of a "new golden age" in the study of black holes.

Attending the birthday celebrations, Virgin chief executive Richard Branson said it was "wonderful to be celebrating his 70th birthday, which in itself is remarkable. He should have won the Nobel prize many times, he is somebody who has discovered many things in his lifetime and he has managed to do that through extreme disability. Stephen Hawking is very keen to go into space and one of his greatest desires is to find out if there is other life in space. We are hoping that by Christmas time we will have put our spaceship [Virgin Galactic] up into space, and hopefully soon it should be possible to get Stephen Hawking into space."

Hawking finished his statement, to a standing ovation from the audience, by saying that it had been a glorious time to be alive and be a researcher in theoretical physics. "Our picture of the universe has changed a great deal in the past 40 years and I'm happy if I've made a small contribution. The fact that we humans – who are ourselves mere collections of fundamental particles of nature – have been able to come this close to an understanding of the laws governing us and our universe is a great triumph."

For more information please visit the links
http://www.guardian.co.uk/science/2012/jan/08/stephen-hawking-70-cambridge-speech
http://www.guardian.co.uk/news/blog/2012/jan/08/stephen-hawking-birthday-70-live-updates

The Universe from Nothing- Lawrence Krauss Lecture

Lawrence Krauss, a wonderful physicist with good humor sense, gives a talk about the beginning of Universe, how it came from nothing and how the end will be, and many more interesting things. The highlight of his talk is, when he comment about jesus, a huge applause came from the audience that took long time to settle down.. "Forget Jesus, a star died so you could be born here!!"...

video link here

The Universe from nothing- Lawrence krauss lecture

Black Holes- Snippets from Hawking's A Brief History of Time

                                   A Black Hole gulping a nearby galaxy

I posted the informations that are made me startling and wondering about the universe that hide lot of mysteries. Here I posted one of the mysteries i.e Black holes.

... a star that was sufficiently massive and compact would have such a strong gravitational field that light could not escape: any light emitted from the surface of the star would be dragged back by the star's gravitational attraction before it could get very far... Such objects are what we now call black holes...

As the star contracts, the gravitational field at its surface gets stronger and the light cones get bent inward more. This makes it more difficult for light from the star to escape, and the light appears dimmer and redder to an observer at a distance. Eventually, when the star has shrunk to a certain critical radius, the gravitational field at the surface becomes so strong that the light cones are bent inward so much that light can no longer escape. According to the theory of relativity, nothing can travel faster than light. Thus if light cannot escape, neither can anything else..

The event horizon , the boundary of the region of space-time from which it is not possible to escape, acts rather like a one-way membrane around the black hole... One could well say of the event horizon what the poet Dante said of the entrance to Hell: "All hope abandon, ye who enter here." Anything or anyone who falls through the event horizon will soon reach the region of infinite density and the end of time.

... the movement of the earth in its orbit round the sun produces gravitational waves. The effect of the energy loss will be to change the orbit of the earth so that gradually it gets nearer and nearer to the sun, eventually collides with it, and settles down to a stationary state. The rate of energy loss in the case of the earth and the sun is very low - about enough to run a small electric heater. This means it will take about a thousand million million million million years for the earth to run into the sun...

We also now have evidence for several other black holes in systems like Cygnus X-1 in our galaxy and in two neighbouring galaxies called the Magellanic Clouds. The number of black holes, however, is almost certainly very much higher; in the long history of the universe, many stars must have burned all their nuclear fuel and have had to collapse. The number of black holes may well be greater even than the number of visible stars, which totals about a hundred thousand million in our galaxy alone.

Does god play Dice? A lecture by Hawking

This lecture is about whether we can predict the future, or whether it is arbitrary and random. In ancient times, the world must have seemed pretty arbitrary. Disasters such as floods or diseases must have seemed to happen without warning, or apparent reason. Primitive people attributed such natural phenomena, to a pantheon of gods and goddesses, who behaved in a capricious and whimsical way. There was no way to predict what they would do, and the only hope was to win favour by gifts or actions. Many people still partially subscribe to this belief, and try to make a pact with fortune. They offer to do certain things, if only they can get an Agrade for a course, or pass their driving test.

Einstein views were summed up in his famous phrase, 'God does not play dice'. He seemed to have felt that the uncertainty was only provisional: but that there was an underlying reality, in which particles would have well defined positions and speeds, and would evolve according to deterministic laws, in the spirit of Laplace. This reality might be known to God, but the quantum nature of light would prevent us seeing it, except through a glass darkly.

In space and time were no longer separate and independent entities. Instead, they were just different directions in a single object called space-time. This space-time was not flat, but was warped and curved
by the matter and energy in it. In order to understand this, considered a sheet of rubber, with a weight placed on it, to represent a star. The weight will form a depression in the rubber, and will cause the sheet near the star to be curved, rather than flat. If one now rolls marbles on the rubber sheet, their paths will be curved, rather than being straight lines. In 1919, a British expedition to West Africa, looked at light from distant stars, that passed near the Sun during an eclipse. They found that the images of the stars were shifted slightly from their normal positions. This indicated that the paths of the light from the stars had been bent by the curved
space-time near the Sun. General Relativity was confirmed.

To sum up, what I have been talking about, is whether the universe evolves in an arbitrary way, or whether it is deterministic. The classical view, put forward by Laplace, was that the future motion of particles was completely determined, if one knew their positions and speeds at one time. This view had to be modified, when Heisenberg put forward his Uncertainty Principle, which said that one could not know both the position, and the speed, accurately. However, it was still possible to predict one combination of position and speed. But even this limited predictability disappeared, when the effects of black holes were taken into account. The loss of particles and information down black holes meant that the particles that came out were random. One could calculate probabilities, but one could not make any definite predictions. Thus, the future of the universe is not completely determined by the laws of science, and its present state, as Laplace thought. God still has a
few tricks up his sleeve. That is all I have to say for the moment. Thank you for listening.

-Stephen William Hawking