ANTIMATTER.doc

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Antimatter

ANTIMATTER INTRODUCTION

Antimatter rockets are what the majority of people think about when

talking of rockets for the future. This is hardly surprising as it is such an

attractive word for the writers of science fiction.

It is, however, not only interesting in the realm of science fiction.

Make no mistake; antimatter is real. mall amounts, in the order of nanograms,

are produced at special facilities every year. It is also the most e!pensive

substance of "arth; in #$$$ the estimated cost for # gram of antimatter was

about %&'.( trillion.

The reason it is so attractive for propulsion is the energy density that

it possesses. )onsider that the ideal energy density for chemical reactions is #

! #*+#*-+ /0kg, for nuclear fission it is 1 ! #* #2#*-#2 /0kg and for nuclear

fusion it is 2 ! #*#3

#*-#3 /0kg, but for the matter4antimatter annihilation it is

$ ! #*#& #*-#& /0kg. This is #*#* #* billion times that of conventional

chemical propellants.

This represents the highest energy release per unit mass of any known

reaction in physics. The reason for this is that the annihilation is the complete

conversion of matter into energy governed by "instein5s famous e6uation

"7mc', rather than just the part conversion that occurs in fission and fusion.

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WHAT IS ANTIMATTER?

Antimatter is e!actly what you might think it is 44 the opposite of

normal matter, of which the majority of our universe is made. 8ntil just

recently, the presence of antimatter in our universe was considered to be only

theoretical. In #$'1, 9ritish physicist Paul A.M. Dirac revised "instein5s

famous e6uation E=mc2. :irac said that "instein didn5t consider that the m

in the e6uation 44 mass 44 could have negative properties as well as positive.

:irac5s e6uation " 7 < or 4 mc' allowed for the e!istence of anti4particles in

our universe. cientists have since proven that several anti4particles e!ist.

These anti4particles are, literally, mirror images of normal matter.

"ach anti4particle has the same mass as its corresponding particle, but the

electrical charges are reversed. =ere are some antimatter discoveries of the

'*th century>

?ositrons 4 "lectrons with a positive instead of negative charge.

:iscovered by )arl Anderson in #$2', positrons were the first evidence

that antimatter e!isted.

Anti4protons 4 ?rotons that have a negative instead of the usual positive

charge. In #$((, researchers at the 9erkeley 9evatron produced an

antiproton.

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Anti4atoms 4 ?airing together positrons and antiprotons, scientists at

)"@, the "uropean BrganiCation for uclear @esearch, created the

first anti4atom. ine anti4hydrogen atoms were created, each lasting

only 3* nanoseconds. As of #$$1, )"@ researchers were pushing the

production of anti4hydrogen atoms to ',*** per hour.

Particle Annihilatin

Dhen antimatter comes into contact with normal matter, these e6ual

but opposite particles collide to produce an e!plosion emitting pure radiation,

which travels out of the point of the e!plosion at the speed of light. 9oth

particles that created the e!plosion are completely annihilated, leaving behind

other subatomic particles. The e!plosion that occurs when antimatter and

matter interact transfers the entire mass of both objects into energy. cientists

believe that this energy is more powerful than any that can be generated by

other propulsion methods.

The problem with developing antimatter propulsion is that there is a

lack of antimatter e!isting in the universe. If there were e6ual amounts of

matter and antimatter, we would likely see these reactions around us. ince

antimatter doesn5t e!ist around us, we don5t see the light that would result from

it colliding with matter.

It is possible that particles outnumbered anti4particles at the time of

the 9ig 9ang. As stated above, the collision of particles and anti4particles

destroys both. And because there may have been more particles in the universe

to start with, those are all that5s left. There may be no naturally4e!isting anti4

particles in our universe today. =owever, scientists discovered a possible

deposit of antimatter near the center of the gala!y in #$++. If that does e!ist, it

would mean that antimatter e!ists naturally, and the need to make our own

antimatter would be eliminated.

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PRODUCTION O! ANTIMATTER

There is technology available to create antimatter through the use of

high4energy particle colliders, also called atom smashers. Atom smashers,

like )"@, are large tunnels lined with powerful super magnets that circle

around to propel atoms at near4light speeds. Dhen an atom is sent through this

accelerator, it slams into a target, creating particles. ome of these particles are

antiparticles that are separated out by the magnetic field. These high4energy

particle accelerators only produce one or two picograms of antiprotons each

year. A picogram is a trillionth of a gram. All of the antiprotons produced at

)"@ in one year would be enough to light a #**4watt electric light bulb for

three seconds.

Atm "ma"her

Anti#rtn Deceleratr $AD%

The Antiproton :ecelerator is a very special machine compared towhat already e!ists at )"@ and other laboratories around the world. o far,

an anti#article &actr' consisted of a chain of several accelerators, each one

performing one of the steps needed to produce antiparticles. The )"@

antiproton comple! is a very good e!ample of this.

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At the end of the +*5s )"@ built an antiproton source called the

Anti#rtn Accumulatr AA. Its task was to produce and accumulate high4

energy antiprotons to feed into the ? in order to transform it into a proton4

antiproton collider. As soon as antiprotons became available, physicists

realiCed how much could be learned by using them at low energy, so )"@

decided to build a new machine> (EAR, the () Ener*' Anti#rtn Rin*.

Antiprotons accumulated in the AAwere e!tracted, decelerated in the PSand

then injected into (EARfor further deceleration. In #$1& a second ring, the

Anti#rtn Cllectr AC, was built around the e!isting AA in order to

improve the antiproton production rate by a factor of #*.

The A) is now being transformed into the AD, which will perform all

the tasks that the A), AA, ? and E"A@ used to do with antiprotons, i.e.

produce, collect, cool, decelerate and eventually e!tract them to the

e!periments.

What +e" the AD cn"i"t &?

The A: ring is an appro!imate circle with a circumference of #11 m.

It consists of a vacuum pipe surrounded by a long se6uence of vacuum pumps,

magnets, radio4fre6uency cavities, high voltage instruments and electronic

circuits. "ach of these pieces has its specific function>

4 Antiprotons circulate inside the vacuum pipe in order to avoid contact with

normal matter like air molecules, and annihilate. The vacuum must be

optimal, therefore several vacuum pumps, which e!tract air, are placed

around the pipe.

4 Magnets as well are placed all around. There are two types of magnets> the

dipoles which have a orth and a outh pole, like the well4known

horseshoe magnet serve to change the direction of movement and make

sure the particles stay within their circular track. They are also called

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bending magnets. Fuadrupoles which have four poles are used as

5lenses5. These focusing magnets make sure that the siCe of the beam is

smaller than the siCe of the vacuum pipe.

4 Magnetic fields can change the direction and siCe of the beam, but not its

energy. To do this you need an electric field> this is provided by radio4

fre6uency cavities that produce high voltages in synchronicity with the

rotation of particles around the ring.

4 everal other instruments are needed to perform more specific tasks> two

cooling systems s6ueeCe the beam in siCe and energy; one injection and

one ejection system let the beam in and out of the machine.

H) +e" the AD )r, ?

Antiparticles have to be created from energy remember> " 7 mc'.

This energy is obtained with protons that have been previously accelerated in

the ?. These protons are smashed into a block of metal, called a target. De

use )opper or Iridium targets mainly because they are easy to cool. Then, theabrupt stopping of such energetic particles releases a huge amount of energy

into a small volume, heating it up to such temperatures that matter4antimatter

particles are spontaneously created. In about one collision out of a million, an

antiproton4proton pair is formed. 9ut given the fact that about #* trillion

protons hit the target about once per minute, this still makes a good #*

million antiprotons heading towards the A:.

The newly created antiprotons behave like a bunch of wild kids; they

are produced almost at the speed of light, but not all of them have e!actly the

same energy this is called energy spread. Moreover, they run randomly in

all directions, also trying to break out 5sideways5 transverse oscillations.

9ending and focusing magnets make sure they stay on the right track, in the

middle of the vacuum pipe, while they begin to race around in the ring.

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At each turn, the strong electric fields inside the radio4fre6uency

cavities begin to decelerate the antiprotons. 8nfortunately, this deceleration

increases the siCe of their transverse oscillations> if nothing is done to cure

that, all antiprotons are lost when they eventually collide with the vacuum

pipe. To avoid that, two methods have been invented> 5stochastic5 and 5electron

cooling5. tochastic or 5random5 cooling works best at high speeds around

the speed of light, c, and electron cooling works better at low speed still fast,

but only #*42* G of c. Their goal is to decrease energy spread and transverse

oscillations of the antiproton beam.

Hinally, when the antiparticles speed is down to about #*G of the

speed of light, the antiprotons s6ueeCed group called a bunch is ready to be

ejected. Bne deceleration cycle is over> it has lasted about one minute.

A strong 5kicker5 magnet is fired in less than a millionth of a second,

and at the ne!t turn, all antiprotons are following a new path, which leads them

into the beam pipes of the e!traction line. There, additional dipole and

6uadrupole magnets steer the beam into one of the three e!periments.

The AD e-#eriment"

Three e!periments are installed in the Antiproton :ecelerator5s

e!perimental hall>

ASACUSAAtomic pectroscopy and )ollisions using low Antiprotons

ATHENAAntihydrogen ?roduction and ?recision "!periments and

ATRAP)old Antihydrogen for ?recise Easer pectroscopy.

AT="A and AT@A?5s goal is to produce antihydrogen in traps, by

combining antiprotons delivered by the A: with positrons emitted by a

radioactive source.

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Antihydrogen atoms were first observed at )"@ in #$$(, and later

#$$+ at Hermilab. In both cases they were produced in flight, that means they

moved at nearly the speed of light, i.e. much too fast to allow precise

measurements on any of their proprieties They made uni6ue electrical signals

in detectors that destroyed them almost immediately after they formed. ow

the idea is to produce slow antihydrogen atoms and store them into traps,

allowing e!tremely accurate comparisons of the properties of hydrogen and

antihydrogen.

AA)8A, on the other hand, will synthesiCe e!otic atoms, in

which an electron is replaced by an antiproton. ?recise laser spectroscopy of

these e!otic atoms is e!pected to reveal lots of information on the behavior of

atomic systems.

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STORA/E

Antiparticles have either a positive or a negative electrical charge, so

they can be stored in what we call a trap which has the appropriate

configuration of electrical and magnetic fields to keep them confined in a

small place. Bf course, this has to be done in good vacuum to avoid collisions

with matter particles. Antiatoms are electrically neutral, but they have

magnetic proprieties that can be used to keep them in magnetic bottles.

Prta0le tra#

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APP(ICATION O! ANTIMATTER

PET Scan

?article physicists regularly use collisions between electrons and their

antiparticles, positrons, to investigate matter and fundamental forces at high

energies. Dhen electron and positron meet, they annihilate, turning into energy

which, at high energies, can rematerialiCe as new particles and antiparticles.

This is what happens at machines such as the Earge "lectron ?ositron E"?

collider at )"@.

At low energies, however, the electron4positron annihilations can be

put to different uses, for e!ample to reveal the workings of the brain in the

techni6ue called P"itrn Emi""in Tm*ra#h' $PET%. In ?"T, the

positrons come from the decay of radioactive nuclei incorporated in a special

fluid injected into the patient. The positrons then annihilate with electrons in

nearby atoms. As the electron and positron are almost at rest when they

annihilate, there is not enough annihilation energy to make even the lightest

particle and antiparticle the electron and the positron, so the energy emerges

as two gamma rays, which shoot off in opposite directions to conserve

momentum.

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!UTURE O! ANTIMATTER

Antimatter a" a #r#ul"in "'"tem

This is not some incredible new technology that will power us

throughout the gala!y. At the most basic level the antimatter rocket is still a

ewtonian rocket, governed by the three laws of motion and it still conforms

to "instein5s theory of special relativity, in other words it cannot e!ceed the

speed of light.

till if we are enable to develop such a propulsion system in the

future it will surely render any other ewtonian rocket obsolete overnight, the

system has the highest predicted efficiency, specific impulse and probably the

highest thrust to weight ratio. There does seem to be a serious amount of

disagreement over this last point, the general feeling seems to be that the thrust

to weight will at least comparable to today5s very powerful chemical rockets.

Dhat this means is that only #** milligrams #0#* gram of antimatter would

be needed to match the total propulsive energy of the pace huttle all those

huge tanks of fuel.This fact has led to the interesting observation that future

advanced spacecraft, such as the antimatter rocket, will not be designed around

their propellant tank like conventional craft. Instead the craft will be designed

around the reactors for nuclear craft or around the systems and chambers to

cause annihilation for antimatter craft. @adiation shielding will also become

a key component of spacecraft design.

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Antimatter #r#ul"in "'"tem"

Bnce we have produced and stored the antimatter we can use it in

propulsion by releasing it into a chamber and allowing it to annihilate with

normal matter which produces its tremendous energy in the form of energetic

sub4atomic particles. There are actually two choices for propulsion. Dell

electron4positron annihilation produces high energy gamma rays which are

impossible to control, hence useless for propulsion, and on top of this are

potentially very dangerous. Dhereas the proton4antiproton annihilation

produces charged particles mostly pions moving at velocities close to that of

light that can be directed with magnetic fields, ma!imiCing propellant mass.

The fact that there is this mass left over after the annihilation means that the

full conversion of mass to energy has not occurred as it does in the electron4

positron annihilation, therefore slightly less energy has been produced.

This energy, however, still far e!ceeds any other method and theresulting particles allow this energy to be harnessed by directing it with

magnetic forces. In other words the perfect reaction does not produce perfect

propulsive result. Another important advantage for antimatter rockets over

nuclear rockets is that heavy reactors are not re6uired, the reaction is

spontaneous. There are four main designs for an antimatter rocket, they are

listed here in increasing specific impulse>

Solid Core 4 Annihilation occurs inside a solid4core heat e!changer, the

reaction superheats hydrogen propellant that is e!pelled through a noCCle.

=igh efficiency and high thrust, but due to the materials the specific

impulse is only #***secs at best.

Gas Core4 Annihilation occurs in the hydrogen propellant. The charged

pions are controlled in magnetic fields and superheat the hydrogen; there

is some loss in the form of gamma rays that cannot be controlled. specific

impulse of '(**secs.

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Plasma Core 4 Annihilation of larger

amounts of antimatter in hydrogen

to produce a hot plasma. ?lasma

contained in magnetic fields, again

some loss in form of gamma

radiation, the plasma is e!pelled to

produce thrust. There are no material constraints here so higher

specific impulse is possible anywhere from (,*** to #**,***secs.

Beam Core4 :irect one to one annihilation, magnetic fields focus the

energetic charged pions that are used directly as the e!hausted

propellant mass. These pions travel close to speed of light so the

specific impulse could be greater than #*,***,***secs.

The spacecraft will have to be designed to be very long as the

annihilation products travel close to the speed of light.

1urne' time

"stimates for travel times to Mars for an advanced antimatter rocket

using the beam core approach are anywhere from '3 hours to ' weeks, it is

probable that it will be somewhere in between. )ompare this to the space

shuttle using its conventional chemical propulsion when a trip to Mars would

take between # and ' years.

Antimatter S#acecra&t

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ANTIMATTER DETONATION

Bver $$.$G of the mass of neutral antimatter is accounted for by

antiprotons and antineutrons. Their annihilation with protons and neutrons is a

complicated process. A proton4antiproton pair can annihilate into a number of

charged and neutral relativistic pions. eutral pions, in turn, decay almost

immediately into gamma rays; charged pions travel a few tens of meters and

then decay further into muons and neutrinos. Hinally, the muons decay into

electrons and more neutrinos. Most of the energy about &*G is thus carried

away by neutrinos, which have almost no interaction with matter and thus

escape into outer space.

The overall structure of energy output from an antimatter bomb is

highly dependent on the amount of regular matter in the area surrounding the

bomb. If the bomb is shielded by sufficient amounts of matter, the gamma rays

are absorbed and the pions slow down before decaying. ?art of the kinetic

energy is thus transferred to the surrounding atoms, which heat up. In the event

of an antimatter detonation in the open atmosphere, most of the energy will

ultimately be carried away by the neutrinos, and the remainder by #*4#** MeJ

gamma rays. The neutrinos would pass through the earth without being

attenuated, while gamma rays are relatively weakly absorbed by matter> they

lose roughly half of their energy per (**4#*** m of air, compared to only

'* cm of concrete. The e!plosion would not cause much physical damage

because its energy would be evenly dispersed over large area, although the

gamma rays may harm people standing nearby. Thus even if the impossible

problem of producing enough antimatter were solved, the antimatter bomb

would not be as practical or destructive as a conventional nuclear weapon.

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ANTIMATTER IN NATURE

About #( billion years ago, matter and antimatter were created in a

gigantic 9ig 9ang in e6ual amounts, at least according to today5s best theory. It

is therefore surprising that our "arth, the solar system, and our gala!y the

Milky Day do not contain any antimatter.

To e!plain this absence, scientists have come out with two

possibilities> either antimatter completely disappeared during the history of

universe, or matter and antimatter have been separated from each other to form

different regions of the universe.

In the second case, we would be located in a region where only

matter e!ists or rather what we call 5matter5, but some antimatter coming

from an 5anti5 region outside our gala!y could still have a chance to reach us.

This antimatter would be in the form of anti4nuclei like anti4=elium, anti4

)arbon, etc.. as opposed to lighter antiparticles such as antiprotons which

are also created in high energy collisions between ordinary matter. To search

for this e!tragalactic antimatter, the best way is to place a particle detector in

space.

AMS

A worldwide collaboration of physicists, lead by obel priCe laureate

?rof. amuel Ting of MIT, decided to build the 5Al#ha Ma*netic

S#ectrmeter5, or AM. AM is a high4energy particle detector, which will try

to detect the passage of such very small amounts of antimatter, while orbiting

at an altitude of a few hundred kilometers above the atmosphere.

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ome of the main challenges of the project are very technical> having

to be carried on the S#ace Shuttle, each component of the apparatus has to be

miniaturiCed as much as possible to keep the total volume to a ma!imum of #*

cubic meters and the weight to a ma!imum of 2 tons a typical high energy

apparatus at E"? with the similar detecting principles is about #*** cubic

meters in volume and #** tons in weight. "ven more important is the power

consumption> AM should not need more than ' kD kilowatts of electricity,

provided by the solar panels of the pace tation. And 'kD is less than what a

kitchen oven needs

AMS34

A first simpler version of the e!periment, AMS34, traveled on the

pace huttle :iscovery for a ten4day mission in #$$1. The apparatus

consisted of a &4layer 5silicon microstrip track detector5 surrounded by a

permanent magnet and a few other systems.

Silicn micr"tri#"can localiCe the passage of charged particles with

a precision of a few hundredth of a millimeter less than a human hair. The

magnet produced a magnetic field where incoming particles were deflected in

opposite directions. uclei are thus identified by measuring both their mass

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and charge. :uring the #* days that AM was in space, not a single

antinucleus was seen among the 2 million nuclei that traversed the e!periment.

In '**3, a new version of the e!periment, called AMS32, will be installed on

the Internatinal S#ace Statin. AM4*' will again be searching for any

e!tragalactic antimatter, but this time with more sensitivity, over a longer time

period and in a wider energy range.

The new apparatus will be e6uipped with a superconducting magnet,

providing a much higher magnetic field, and an enhanced silicon tracker, able

to record billions of tracks of matter and antimatterK particles. Bther

detectors have also been added to the design to better identify and measure

incoming particles and nuclei. AM4*' will be installed on the long arm of the

I and e!posed to cosmic rays for three years.

This very moment, a few modules of I are already orbiting over

our heads. Dith the e!perimental data collected during this second mission,

AM hopes to find the last traces of big4bang antimatter, if there are any left

AMS32

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PRO5(EMS

Pr0lem" in Pr+uctin

De would need at leastseveral milligrams of antimatter to fuel a

beam core antimatter engine in local operations and several kilograms for

interstellar travel to Alpha )enturi. Liven that currently #4#* nanograms of

antiprotons are produced a year at Hermilab )hicago and )"@ Leneva, a

beamed core engine is not feasible in the near future.

Pr0lem" in Stra*e

The ?enning trap has been developed, it is a portable antiproton trap

which is capable of storing #*#*#*-#* antiprotons for one week using the

superposition of electric and magnetic fields. The ne!t stage is an

improvement to #*#'

#*-#' antiproton storage. Hor complete antimatter

propulsion it is thought that #*'*#*-'* anti4protons will need to be stored.

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!A67S A5OUT ANTIMATTER

8 What can antimatter 0e u"e+ &r?

There are several different uses for antimatter, the main one being for

medical diagnostics where positrons are used to help identify different diseases

with the ?ositron "mission Tomography or ?"T scan. Hor other uses, we are

still in the first phases of development and it5s difficult to foresee what will

happen in the ne!t ten years.

8 Can )e u"e antimatter t #r#el a car r a "#ace"hi#?

In principle, yes, but in practice it is very difficult. ou all know that

the tar Trek paceship "nterprise flies around powered by antimatter. 9ut in

reality, making antimatter is so difficult that it is hard to foresee it ever being

used as a propellant fuel. In order to propel a matter spacecraft weighing

several tons up to the speed of light, you would need an e6ual amount of

antimatter and, using the present technology, it would take millions and

millions of years to produce a sufficient amount. =owever, if you had a gram

of antimatter, you could drive your car for about #**.*** years.

8 What +e" antimatter l, li,e?

Matter and antimatter are identical. Eooking at an object means

seeing the photons coming from that object; however, photons come from both

matter and antimatter. If there were a distant gala!y made out of antimatter,

you couldn5t distinguish it from a matter gala!y just by seeing the light from it.

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8 H) can 'u 0e " "ure there i" nt antimatter arun+?

If there was antimatter here, around us, it would annihilate with

matter and we would see light coming out. 9ut we don5t...About the possibility

of antimatter in space antistars or antigala!ies, theorist have reasons to

believe that the 8niverse is all made of matter. 9ut we are not #**G sure, and

that5s way there are e!periments, like AM, which are going to look for it.

8 I& the nl' +i&&erence 0et)een a #article an+ it" anti#article i" the

char*e9 h) + 'u +i"tin*ui"h a neutrn &rm an antineutrn ?

eutrons are made of 6uarks, and antineutrons are made of

anti6uarks. Fuarks and anti6uarks have opposite charges, even though they

sum up to Cero in both cases. And a very good way to recogniCe them is to put

a neutron close to an antineutron and see how they immediately annihilate.

8 What a0ut anti#htn"?

?hotons have Cero charge and do not contain inside objects that are

charged, so a photon can not be distinguished from an antiphoton. ?hoton and

antiphotons are the same thing, i.e. the photon is its own antiparticle.

8 H) + "un+ )a:e" #r#a*ate in antimatter?

If there is a difference between matter and antimatter, it is very very

tiny, that5s why we are doing e!periments here at )"@ to investigate it. They

are so similar that sound waves, that are vibrations of matter or antimatter,

would be identical. An antimatter piano would sound e!actly as a matter one.

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8 H) +e" the *ra:itatinal &iel+ act n antimatter?

The gravitational force depends from the energy of an object, and

since matter and antimatter have both positive energy, gravitation acts on them

in the same way. This means that an object made of matter and one made of

antimatter would both stand on the floor, the latter one not flying off the sky.

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CONC(USION

:ue to the highest energy release per unit mass of any known reaction

,we can say that antimatter will be a future energy source but first need a

reliable method of producing large amount of it.

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/(OSSAR;

Clin*9y analogy with the kinetic theory of gases where heat is e6uivalent

to disorder, the term NcoolingO designates the reduction of beamPs transverse

dimensions and energy spread. :ifferent techni6ues can be used to this effect.

"lectron cooling, more effective at low energy, uses an electron beam merged

with the antiproton beam, and acts as a heat e!changer between the two beams.

In the case of stochastic cooling, an error signal generated in a monitor is fed

back, via a collector, to the beam sample which created it, eventually centering

the samplePs characteristics towards the average value, after a large number of

passages through the apparatus.

Munan elementary particle having a mass '*$ times that of the electron, a

negative electric charge, and mean lifetime of '.'#*4& seconds.

NeutrinAn electrically neutral particle that is often emitted in the process of

radioactive decay of nuclei. eutrinos are difficult to detect, and their

e!istence was postulated twenty years before the first one was actually

discovered in the laboratory. Millions of neutrinos produces by nuclear

reactions in the sun pass through your body every second without disturbing

any atom.

Pinit is produced either in a neutral form with a mass '&3 times that of an

electron and a mean lifetime of 1.3#*4+ seconds or in a positively or

negatively charged form with a mass '+2 times that of an electron and a mean

life time of '.*41seconds.

6uar,"ubatomic particles which possess a fractional electric charge, and of

which protons, neutrons etc. are believed to be composed.

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Ra+i!re


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RE!ERENCE

Hundamentals of )ompressible Hlow with Aircraft Q @ocket

propulsion by . M. ahiya

http>00livefromcern.web.cern.ch

http>00public.web.cern.ch

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Antimatter

A5STRACT

Antimatter is e!actly what you might think it is 44 the opposite of

normal matter, of which the majority of our universe is made. 8ntil just

recently, the presence of antimatter in our universe was considered to be only

theoretical. In #$'1, 9ritish physicist Paul A.M. Dirac revised "instein5s

famous e6uation E=mc2. :irac said that "instein didn5t consider that the m

in the e6uation 44 mass 44 could have negative properties as well as positive.

:irac5s e6uation " 7 < or 4 mc' allowed for the e!istence of anti4particles in

our universe. cientists have since proven that several anti4particles e!ist.

Dhen antimatter comes into contact with normal matter, these e6ual

but opposite particles collide to produce an e!plosion emitting pure radiation,

which travels out of the point of the e!plosion at the speed of light. 9oth

particles that created the e!plosion are completely annihilated, leaving behindother subatomic particles. The e!plosion that occurs when antimatter and

matter interact transfers the entire mass of both objects into energy. cientists

believe that this energy is more powerful than any that can be generated by

other propulsion methods.

'&


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Antimatter

CONTENTS

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Antimatter

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