Part 8 (1/2)

-MARK TWAIN

You can recognize a pioneer by the arrows in his back

-BEVERLY RUBIK

In Dan Brown's book Angels and De predecessor to The Da Vinci Code, a small band of extremists, the Illu an antimatter bomb, stolen from CERN, the nuclear laboratory outside Geneva The conspirators know that when matter and antimatter touch each other the result is a en boh an antimatter bomb is pure fiction, antimatter is very real

An atomic bomb, for all its awesome power, is only about 1 percent efficient Only a tiny fraction of the uraniuy But if an antimatter bomb could be constructed, it would convert 100 percent of itsit far more efficient than a nuclear bomb (More precisely, about 50 percent of the matter in an antiy; the rest would be carried away in the form of undetectable particles called neutrinos) Antih an antimatter bomb does not exist, physicists have been able to use their powerful atom smashers to create minute quantities of antimatter for study

PRODUCING ANTI-ATOMS AND ANTI-CHEMISTRY

At the beginning of the twentieth century, physicists realized that the atoed subatoe) circulating around a tiny nucleus (with a positive charge) The nucleus, in turn, consisted of protons (which carried the positive charge) and neutrons (which were electrically neutral)

So it came as quite a shock in the 1930s when physicists realized that for every particle there is a twin, an antiparticle, but with an opposite charge The first antiparticle to be discovered was the antielectron (called the positron), which has a positive charge The positron is identical to the electron in every way, except that it carries the opposite charge It was first discovered in photographs of cosmic rays taken in a cloud chamber (Positron tracks are quite easy to see in a cloud chanetic field, they bend in the opposite direction froraphed such antih school) In 1955 the particle accelerator at the University of California at Berkeley, the Bevatron, produced the first antiproton As expected, it is identical to the proton except that it has a negative charge This means that, in principle, one can create anti-ato around antiprotons) In fact, anti-elements, anti-chemistry, anti-people, anti-Earths, and even anti-universes are theoretically possible

At present the giant particle accelerators at CERN and the Fero have been able to createa bea particle accelerators, thereby creating a shower of subatonets separate out the antiprotons, which are slowed down to very low velocities and then are exposed to the antielectrons that are naturally emitted from sodium-22 When the antielectronsobt around the antiprotons, they create antihydrogen, since hydrogen is made up of one proton and one electron) In a pure vacuuht live forever But because of impurities and collisions with the wall, these anti-atoms eventually strike ordinary atoy

In 1995 CERN made history when it announced that it had created nine antihydrogen ato one hundred ato to prevent us froering cost Producing even a few ounces of anti-atoms would bankrupt any nation The current rate of production of antiraht increase by a factor of three by the year 2020 The economics of antimatter are very poor In 2004 it cost CERN 20 raram of antimatter would cost 100 quadrillion and the antimatter factory would need to run continuously for 100 billion years! This makes antimatter the most precious substance in the world

”If we could assemble all the anti-matter we've ever made at CERN and annihilate it with h energy to light a single electric light bulb for a fewantimatter poses extraordinary problems, since any contact betweenantimatter in an ordinary container would be suicide When the antimatter touched the walls, it would explode So how does one handle antimatter if it is so volatile? One ould be first to ionize the antias of ions, and then to safely confine it in a ”netic field would prevent the anti the walls of the chaine, a steady stream of antimatter would need to be fed into a reaction chamber, where it would be carefully co a controlled explosion, similar to the explosion created by chemical rockets The ions created by this explosion would then be shot out one end of the anti propulsion Because of the antiy, in theory it is one of the ns for future starshi+ps In the Star Trek series, antiines are energized by the controlled collision of matter and antimatter

AN ANTIMATTER ROCKET

One of the main proponents of the antimatter rocket is physicist Gerald Smith of Pennsylvania State University He believes that in the short terrams of positrons would be sufficient to take an antimatter rocket to Mars in just several weeks He notes that the energy packed into antiy packed into ordinary rocket fuel

The first step in creating this fuel would be to create beams of antiprotons, via a particle accelerator, and then store the When built, the Penning trap would weigh 220 pounds (en and liquid heliunetic field (At very low teth of the antiprotons is several tith of the atoms in the container walls, so the antiprotons wouldthe trap should be able to store the antiprotons for about five days (until they finally are annihilated whentrap should be able to store about a billionth of a gra trap that can store up to a h antimatter is thedraram would cost about 625 trillion at today's prices) A new particle injector being built at Fero should be able to increase the production of antirams per year, which should drive down prices However, Harold Gerrish of NASA believes that with further io down to 5,000 per ies in Los Alaoal is to remove antimatter from the far-out realm of science fiction into the commercially exploitable realm for transportation and medical applications”

So far, particle accelerators that can produce antiprotons are not specifically designed to do so, so they are quite inefficient Such particle accelerators are designed primarily to be research tools, not factories for anti a new particle accelerator that will be specifically designed to produce copious quantities of antiprotons to drive down the cost

If prices for antimatter can be lowered even further by technical improvements and mass production, Smith envisions a time when the antimatter rocket could become a workhorse for interplanetary and possibly interstellar travel Until then, however, anti boards

NATURALLY OCCURRING ANTIMATTER

If antiht one find antimatter more easily in outer space? Unfortunately, searches for antimatter in the universe have turned up very little, which is rather surprising to physicists The fact that our universe is made up mainly of matter, rather than antiht naively have assu of the universe, there were equal, symmetrical quantities of

The most likely solution was first proposed by Andrei Sakharov, the en bomb for the Soviet Union in the 1950s Sakharov theorized that at the beginning of the universe there was a slight asy This tiny sy is called ”CP violation” This phenoorous research In effect, Sakharov theorized that all the atoms in the universe today are left over from a near perfect cancellation betweencaused a cosmic cancellation between the two The tiny leftover matter created a residue that forms the visible universe of today All the atoms in our bodies are leftovers from this titanic collision of matter and antimatter

This theory leaves open the possibility that small a that source would drastically reduce the cost of producing antiines In principle, deposits of naturally occurring antimatter should be easy to detect When an electron and an antielectron y of 102the universe for gaerprint” for naturally occurring antimatter

In fact, ”fountains” of antialaxy, not far froalactic center, by Dr William Purcell of Northwestern University Apparently a streaamma radiation at 102 as If this pluht be possible that other pockets of antimatter exist in the universe that were not destroyed in the big bang

To look for naturally occurring antimatter more systematically, the PAMELA (Payload for Antiht-Nuclei Astrophysics) satellite was launched into orbit in 2006 It is a collaborative effort between Russia, Italy, Gerned to search for pockets of anti for antih-altitude balloons and the space Shuttle, so the data was collected for no more than a week or so PAMELA, by contrast, will stay in orbit for at least three years ”It is the best detector ever constructed and ill use it for a long period,” declares teaio Picozza of the University of Roned to detect cosmic rays from ordinary sources, such as supernovae, but also from unusual ones, such as stars made entirely of antinature of anti-heliuht be produced in the interiors of anti-stars Althoughresulted in a near perfect cancellation between matter and antimatter, as Sakharov believed, PAMELA is based on a different assuions of antio that cancellation and hence exist today in the form of anti-stars

If antimatter exists in ht be possible to ”harvest” some of that antimatter to use to propel a starshi+p NASA's Institute for Advanced Concepts takes the idea of harvesting antih that it recently funded a pilot prograenerate a net, just like you're fishi+ng,” says Gerald Jackson of Hbar Technologies, one of the organizations spearheading the project

The antimatter harvester is based on three concentric spheres, each made out of a lattice wire network The outermost sphere would be 16 kiloed, so that it would repel any protons, which are positively charged, but attract antiprotons, which are negatively charged The antiprotons would be collected by the outer sphere, then slon as they passed through the second sphere and would finally stop when they reached the innermost sphere, which would be 100 netic bottle and coen

Jackson estimates that controlled matter-antimatter reactions inside a spacecraft could fuel a solar sail to Pluto using just 30 rah to fuel a starshi+p to Alpha Centauri Jackson clairaht be harvested by the space probe Given the coe antimatter collector, however, it probably won't be realized until the end of this century, or beyond

So anti in outer space (The Flash Gordon co in space, which could create a terrifying explosion if it ca antimatter is not found in space, ill have to wait decades or even centuries before we can produce significantly large quantities of anti that the technical proble antimatter can be solved, this leaves open the possibility that one day antimatter rockets may take us to the stars

Given e know of antiy, I would classify an antimatter rocket shi+p as a Class I impossibility

FOUNDER OF ANTIMATTER

What is antie that nature would double the nuood reason Nature is usually quite sparing, but now that we know about antimatter, nature seems to be supremely redundant and wasteful And if antimatter exists, can anti-universes also exist?

To answer these questions, one has to investigate the origin of antimatter itself The discovery of anti work of Paul Dirac, one of the most brilliant physicists of the twentieth century He held the Lucasian Chair at Cae University, the same chair held by Newton, and the chair currently held by Stephen Hawking Dirac, born in 1902, was a tall, wiry man as in his early twenties when the quantu electrical engineering at that time, he was suddenly swept up in the tidal wave of interest unleashed by the quantum theory

The quantum theory was based on the idea that particles like electrons could be described not as pointlike particles but as a wave of soer's celebrated wave equation (The wave represents the probability of finding the particle at that point) But Dirac realized that there was a defect with Schrodinger's equation It described only electrons her velocities, the equation failed because it did not obey the laws of objects h velocities, that is, the laws of relativity found by Albert Einstein

To the young Dirac, the challenge was to reforer equation to accommodate the theory of relativity In 1928 Dirac proposed a radical er equation that fully obeyed Einstein's relativity theory The world of physics was stunned Dirac found his famous relativistic equation for the electron purely by her mathematical objects, called spinors Aa centerpiece for the entire universe (Unlike reat breakthroughs in physics be firrounded in experiy To hiuide to great breakthroughs He wrote, ”It is more important to have beauty in one's equations than to have the fro beauty in one's equations, and if one has a really sound insight, one is on a sure line of progress”) In developing his new equation for the electron, Dirac realized that Einstein's celebrated equation, E = h it is splattered over Madison Avenue ads, children's T-shi+rts, cartoons, and even the costumes of superheroes, Einstein's equation is only partially correct The correct equation is actually E = n arises because we have to take the square root of a certain quantity Taking the square root of a quantity always introduces a plus or y There is an axiom of physics that states that objects always tend to the state of lowest energy (this is the reason that water always seeks the lowest level, sea level) Since y state, the prospect of negative energy was potentially disastrous It meant that all electrons would eventually tuy, hence Dirac's theory would be unstable So Dirac invented the concept of the ”Dirac sea” He envisioned that all negative energy states were already filled up, and hence an electron could not tuy Hence the universe was stable Also a ga in a negative energy state and kick it up into a state of positive energy We would then see the gamma ray turn into an electron and a ”hole” develop in the Dirac sea This hole would act like a bubble in the vacuue and the sainal electron In other words, the hole would behave like an antielectron So in this picture antimatter consists of ”bubbles” in the Dirac sea

Just a few years after Diracprediction, Carl Anderson actually discovered the antielectron (for which Dirac won the nobel Prize in 1933)

In other words, antimatter exists because the Dirac equation has two types of solutions, one for matter, and one for antimatter (And this in turn is the outcome of special relativity) Not only did the Dirac equation predict the existence of antimatter; it also predicted the ”spin” of the electron Subato top The spin of the electron, in turn, is crucial to understanding the flow of electrons in transistors and semiconductors, which forrets that Dirac did not patent his equation He writes, ”Dirac would have made a fortune if he had patented the Dirac equation He would have had a royalty on every television, Walkame and computer”

Today Dirac's celebrated equation is etched in the stone of Westminster Abbey, not far from the tomb of Isaac Newton In the entire world, it is perhaps the only equation given this distinctive honor

DIRAC AND NEWTON

Historians of science seeking to understand the origins of how Dirac came up with his revolutionary equation and the concept of antiely, Newton and Dirac share a number of similarities Both were in their twenties when they did their see University, both were masters of mathematics, and both shared another stark characteristic: a total lack of social skills, to the point of pathology Both were notorious for their inability to engage in sraces Painfully shy, Dirac would never say anything unless asked directly, and then he would reply ”yes,” or ”no,” or ”I don't know”

Dirac was also extremely modest and detested publicity When he arded the nobel Prize in Physics, he seriously considered turning it down because of the notoriety and trouble that it would generate But when it was pointed out to hienerate even more publicity he decided to accept it

Volumes have been written about Newton's peculiar personality, with hypotheses ranging fro to mental illness But recently a new theory has been proposed by Caht explain both Newton's and Dirac's strange personalities Baron-Cohen claier's syndrome, which is akin to autism, like the idiot savant in the er's are notoriously reticent, socially aard, and sometimes blessed with enormous calculational ability, but unlike autistic individuals they are functional in society and can hold productive jobs If this theory is true, then perhaps the miraculous calculational power of Newton and Dirac ca socially apart from the rest of hu Dirac's theory, we can noer a host of questions: What is the antiravity? Do anti-universes exist?

As we discussed, antiparticles have the opposite charge of ordinary e at all (such as the photon, a particle of light, or the graviton, which is a particle of gravity) can be their own antiparticle We see that gravitation is its own antiravity are the saravity, not up (This is universally believed by physicists, but it has actually never been demonstrated in the laboratory) Dirac's theory also answers the deep questions: Why does nature allow for antimatter? Does that mean anti-universes exist?

In soonist discovers a new Earth-like planet in outer space In fact, the new planet see is made of antimatter We have antimatter twins on this planet, with anti-children, who live in anti-cities Since the laws of anti-chees are reversed, people living in such a world would never know they were e-reversed or C-reversed universe, since all charges are reversed in this anti-universe, but everything else remains the same) In other science fiction stories scientists discover a twin of the Earth in outer space, except that it is a Looking Glass universe, where everything is left-right reversed Everyone's heart is on the right side and most people are left-handed They live out their lives never knowing that they live in a left-right reversed Looking Glass universe (Physicists call such a Looking Glass universe a parity-reversed or P-reversed universe) Can such antimatter and parity-reversed universes really exist? Physicists take questions about twin universes very seriously, since Newton's and Einstein's equations rees on all our subatoht orientation Hence, C-reversed and P-reversed universes are in principle possible