Part 12 (1/2)

So Feynman revealed the true secret of anti backward in time This simple observation immediately explained the puzzle that all particles have antiparticle partners: it's because all particles can travel backward in time, and hence masquerade as antimatter (This interpretation is equivalent to the ”Dirac sea,” mentioned earlier, but it is simpler, and it is the explanation currently accepted today) Now let's say we have a lump of antie explosion There are now trillions of electrons and trillions of antielectrons being annihilated But if we reversed the direction of the arrow for the antielectron, turning it into an electron going backward in ti backward and forward trillions of times

There was a further curious result: there must be just one electron in the lu back and forth, zigzagging in time Each time it did a U-turn in time it became antimatter But if it did another U-turn in time then it turned into another electron

(With his thesis adviser, John Wheeler, Feynman then speculated that perhaps the entire universe consisted of just one electron, zigzagging back and forth in ti only a single electron was created Trillions of years later, this single electron would eventually encounter the cataclyso backward in tio back to the original big bang, and then perfor journeys back and forth, fro to Doomsday Our universe in the twenty-first century is just a time slice of this electron's journey, in which we see trillions of electrons and antielectrons, that is, the visible universe As strange as this theory may appear, it would explain a curious fact from the quantum theory: why all electrons are the sareen electrons or Johnny electrons Electrons have no individuality You cannot ”tag” an electron, like scientists so animals in the wild to study them Maybe the reason is that the entire universe consists of the sa back and forth in ti back in tie into the past? Is it possible to send today's Wall Street Journal back to yourself in the past, so you canon the stock market?

The answer is no

If we treat antimatter as just another exotic form of matter and then perform an experiment with antimatter, there are no violations of causality Cause and effect remain the same Ifreverse the arrow of ti it backward in time, then we have only performed ahas changed physically All experimental results remain the sa backward and forward in tioes backward in time, it simply fulfills the past So it appears as if the advanced solutions from the future are indeed necessary to have a consistent quantum theory, but they ultimately do not violate causality (In fact, without these bizarre advanced waves, causality would be violated in the quantum theory Feynman showed that if we add the contribution of the advanced and retarded waves, we find that the terht violate causality cancel precisely Thus anti causality Without antiht collapse) Feynerm of this crazy idea until it eventually blossomed into a complete quantum theory of the electron His creation, quantum electrodynamics (QED), has been experi it one of the ues Julian Schwinger and Sin-Itiro Toa the nobel Prize in 1965

(In Feynman's nobel Prize acceptance speech, he said that as a youth he impulsively fell in love with these advanced waves froirl Today that beautiful girl has rooman and is the mother of many children One of those children is his theory of quantum electrodynamics) TACHYONS FROM THE FUTURE

In addition to advanced waves froain in the quantum theory) there is yet another bizarre concept from the quantum theory that seems just as crazy, but perhaps not as useful This is the idea of ”tachyons,” which appear regularly on Star Trek Anytiy to perforical operation, they invoke tachyons

Tachyons live in a strange world where everything travels faster than light As tachyons lose energy, they travel faster, which violates coy, they travel at infinite velocity As tachyons gain energy, however, they slon until they reach the speed of light

What inary inary,” we mean that their mass has been multiplied by the square root of minus one, or ”i”) If we simply take Einstein's fa marvelous happens All of a sudden particles travel faster than light

This result gives rise to strange situations If a tachyon travels through y because it collides with atoy, it speeds up, which further increases its collisions with atoy and hence accelerate even faster As this creates a vicious cycle, the tachyon naturally attains infinite velocity all by itself!

(Tachyons are different froative y, travels at less than the speed of light, and can be created in our particle accelerators It falls down under gravity, according to theory Anti backward in tiy and also travels less than the speed of light, but falls up under gravity Negative e quantities, it can in theory be used to fuel tiinary ravity They, too, have not been found in the laboratory) As bizarre as tachyons are, they have been seriously studied by physicists, including the late Gerald Feinberg of Colue Sudarshan of the University of Texas at Austin The problem is that no one has ever seen a tachyon in the laboratory The key experimental evidence for tachyons would be a violation of causality Feinberg even suggested that physicists examine a laser beam before it itched on If tachyons exist, then perhaps light from the laser beam could be detected even before the apparatus was turned on

In science fiction stories tachyons are regularly used to send es back to the past to seers But if one examines the physics it is not clear if this is possible Feinberg, for exa forward in tiy tachyon going backward in tiard to antimatter) and hence there was no violation of causality

Science fiction aside, today the ht have existed at the instant of the big bang, violating causality, but they don't exist anyetting the universe to ”bang” in the first place In that sense, tachyons are essential for so

Tachyons have a peculiar property When you put them into any theory, they destabilize the ”vacuuy state of a system If a system has tachyons, it is in a ”false vacuum,” so the system is unstable and will decay down to the true vacuum

Think of a dam that holds back the water in a lake This represents the ”false vacuuh the day state that is lower than the da out of the dam break, the system attains the true vacuum as the water floard sea level

In the sainally started off in the false vacuum, in which there were tachyons But the presence of tachyons y state, and hence the system was unstable A tiny ”rip” appeared in the fabric of space-tier, a bubble eed Outside the bubble the tachyons still exist, but inside the bubble the tachyons have all disappeared As the bubble expands, we find the universe as we know it, without tachyons This is the big bang

One theory taken very seriously by cosists is that a tachyon, called the ”inflation,” started the original process of inflation As we mentioned earlier, the inflationary universe theory states that the universe started off as a tiny bubble of space-tied inflationary period Physicists believe that the universe originally started off in the false vacuum state, where the inflation field was a tachyon But the presence of a tachyon destabilized the vacuum, and tiny bubbles formed Inside one of these bubbles the inflation field assuan to inflate rapidly, until it became our universe Inside our bubble-universe the inflation has disappeared, so it can no longer be detected in our universe So tachyons represent a bizarre quantuht and perhaps even violate causality But they disappeared a long tiave birth to the universe itself

All this may sound like idle speculation that is not testable But the theory of the false vacuu in 2008, when the Large Hadron Collider is turned on outside Geneva, Switzerland One of the key purposes of the LHC is to find the ”Higgs boson,” the last particle in the Standard Model, the one that has yet to be found It is the last piece of this jigsaw puzzle (The Higgs particle is so important but elusive that nobel laureate Leon Leders boson, physicists believe, originally started out as a tachyon In the false vacuum, none of the subatomic particles had any mass But its presence destabilized the vacuum, and the universe s boson turned into an ordinary particle After the transition from a tachyon to an ordinary particle, the subatoin to have the masses that we gs boson will not only co piece of the Standard Model, it will also verify that the tachyon state once existed but has been transfornition is ruled out by Newtonian physics The iron rule of cause and effect is never violated In the quantum theory, new states of matter are possible, such as anti backward in time, but causality is not violated In fact, in a quantu causality Tachyons at first seem to violate causality, but physicists believe that their true purpose was to set off the big bang and hence they are not observable anynition seems to be ruled out, at least for the foreseeable future,it a Class III impossibility It would set off a major shake-up in the very foundations of nition was ever proved in reproducible experiue

THE FUTURE OF THE IMPOSSIBLE

There is nothing so big nor so crazy that one out of a ical societies may not feel itself driven to do, provided it is physically possible

-FREE MAN DYSON Destiny is not ato be waited for-it is a thing to be achieved

-WILLIAM JENNINGS BRYAN Are there truths that will be forever beyond our grasp? Are there reale that will be outside the capabilities of even an advanced civilization? Of all the technologies analyzed so far, only perpetual ory of Class III iies that are similarly i that certain things are truly impossible One sile using only a compass and ruler; this was proven back in 1837

Even in simple systems such as arithmetic there are impossibilities As I mentioned earlier, it is impossible to prove all the true statements in arithmetic within the postulates of arithmetic Arithmetic is incomplete There will always be true statements in arither systeh soerous to declare that so is absolutely impossible in the physical sciences Let iven by nobel laureate Albert A Michelson in 1894 at the dedication of the Ryerson Physical Lab at the University of Chicago, in which he declared that it was impossible to discover any new physics: ”The more important fundamental laws and facts of physical science have all been discovered, and these are now so fir supplanted in consequence of new discoveries is exceedingly remoteOur future discoveries must be looked for in the sixth place of decimals”

His rereatest upheavals in scientific history, the quantum revolution of 1900, and the relativity revolution of 1905 The point is that things that are impossible today violate the knos of physics, but the laws of physics, as we know theuste Co in Cours de Philosophie, declared that it was impossible for science to determine what the stars were made of This see was known about the nature of stars They were so distant that it was impossible to visit them Yet just a few years after hespectroscopy) declared that the sun wasthe spectral lines froo it is possible to determine the cheed the world of science bya list of other ”impossibilities”:He claimed that the ”ultie” In other words, it was iht that y and chemistry It was impossible, he claiht that it was impossible that the study of heavenly bodies would have any impact on human affairs

In the nineteenth century it was reasonable to propose these ”impossibilities” since so little was known about funda was known about the secrets of matter and life But today we have the atomic theory, which has opened up a whole new realation into the structure of matter We know about DNA and the quantum theory, which have unraveled the secrets of life and chemistry We also know about meteor impacts from space, which have not only influenced the course of life on Earth, but have helped to shape its very existence

Astronoestion that Comte's vieere partly responsible for the subsequent decline in French science”

Mathe Co to , why Comte could not find an unsolvable proble as an unsolvable proble a new set of impossibilities: ill never knohat happened before the big bang (or why it ”banged” in the first place), and ill never achieve a ”theory of everything”

Physicist John Wheeler commented on the first ”io, you could ask anybody, 'Can we so?' and he would have told you, 'Preposterous! Impossible!' I feel the same way about the question, 'Will we ever understand how the universe ca?'”

Astronoht travels is lie of the structure of the Universe We cannot knohether it is finite or infinite, whether it had a beginning or will have an end, whether the structure of physics is the same everywhere, or whether the Universe is ultireat questions about the nature of the Universe-fro to its end-turn out to be unanswerable”

Barrow is correct in saying that ill never knoith absolute certainty, the true nature of the universe, in all its glory But it is possible to incrementally chip away at these eternal questions and co the absolute boundaries of our knowledge, these ”ies awaiting the next generation of scientists These limits are like piecrusts, made to be broken

DETECTING THE PREBIG BANG ERA In the case of the big bang, a new generation of detectors is being built that could settle some of these eternal questions Today our radiation detectors in outer space can only measure the , when the first atoms formed It is impossible to use this microwave radiation to probe earlier than 300,000 years after the big bang, since radiation froinal fireball was too hot and random to yield useful information

But if we analyze other types of radiation weneutrinos, for exa (neutrinos are so elusive that they can travel through an entire solar system made of solid lead) Neutrino radiation could take us within a few seconds after the big bang

But perhaps the ultiravity waves,” waves thatthe fabric of space-tio says, ”By round we can look back to one second after the Bang But gravitational waves from [the] inflation area are relics of the universe 10-35 seconds after the bang”

Gravity waves were first predicted by Einstein in 1916; they may eventually become the most important probe for astronomy Historically each time a new form of radiation was harnessed, a new era in astronoht, used by Galileo to investigate the solar system The second form of radiation was radio waves, which eventually enabled us to probe the centers of galaxies to find black holes Gravity wave detectors ravity waves have to exist To see this, consider the age-old question: what happens if the sun suddenly disappears? According to Newton, ould feel the effects immediately The Earth would be instantly thrown out of itsobt and plunged into darkness This is because Newton's law of gravity does not take into account velocity, and hence forces act instantly throughout the universe But according to Einstein, nothing can travel faster than light, so it would take eight minutes for the information about the sun's disappearance to reach the Earth In other words, a spherical ”shock wave” of gravity would ee from the sun and eventually hit the Earth Outside this sphere of gravity waves, it would appear as if the sun were still shi+ning normally, because information about the disappearance of the sun would not have reached Earth Inside this sphere of gravity waves, however, the sun would have already disappeared, as the expanding shock wave of gravity waves travels at the speed of light

Another way to see why gravity wavesto Einstein, space-time is a fabric that can be warped or stretched, like a curved bed sheet If we grab a bed sheet and shake it rapidly we see that waves ripple along the surface of the bed sheet and travel at a definite velocity In the sa the fabric of space-ti topics in physics today In 2003 the first large-scale gravity wave detectors became operational-called LIGO (Laser Interfero 25 ton, and another in Livingston Parish, Louisiana It is hoped that LIGO, at a cost of 365neutron stars and black holes

The next big leap will take place in 2015, when an entirely new generation of satellites will be launched that will analyze gravitational radiation in outer space from the instant of creation The three satellites that make up LISA (Laser Interferometer space Antenna), a joint project of NASA and the European space Agency, will be sent into orbit around the sun These satellites will be capable of detecting gravitational waves e If a gravity wave fro around the universe hits one of the satellites, it will disturb the laser beams, and this disturbance can then beus ”baby pictures” of the instant of creation itself

LISA consists of three satellites circling the sun arranged in a triangle, each connected by laser beaest instrument of science ever created This system of three satellites will orbit the sun about 30 million miles from the Earth