Seed Magazine: apuntes para el siglo XXI

8/14/2019 Seed Magazine: apuntes para el siglo XXI

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Cribsheet #2

CLImAtE chAnge

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Seeds Tear-outable tool for living in the 21st centuryThe Key Questionin Climate Science:

clouds

Water vapor

Sea ice

CLIMATE treaty map

How much will the earths

temperature rise as humans

double the amount of carbon

dioxide in the atmosphere

through use of fossil fuels?

Radiation from the sun enters the atmosphere.

Some of it is reflected back into space,

but a good portion is absorbed by the

atmosphere and the earths surface.

The surface, in turn, heats up

and emits infrared radiation.

Greenhouse gas molecules

absorb radiaton from the

sun and earth, heat up,

and emit infrared radiation.

Some infrared radiation is

directed back toward the

earth, contributing to the

warming of the surface.

More carbon dioxide was added

to the atmosphere in the past 200

years than between the last Ice

Age and the Industrial Revolution.

What is the best way to deal with these changes?The issue: soundbiteThe earths average temperature is likely to rise by 2 to 6 C as a result of a projected doubling of the amount of CO

2in the atmosphere from preindustrial

levels, to 560 parts per million by mid-century. The effects could be severe. Sea levels could rise by as much as 6 meters as the icecaps melt; deserts may become

larger, storms more severe, heat waves more common, and snow could turn to rain, reducing our ability to collect water for drinking and irrigation. The Kyoto

Protocol, effective this year, is an agreement by member nations to limit their carbon emissions. The alternative supported by the U.S. and Australia, the

Asia-Pacific Partnership, seeks to incentivize the creation and deployment of green technologies, but doesn't limit carbon emissions and sets no target dates.

As the earth warms, more water evaporates,

creating more clouds. Since clouds are white and

reflective, they bounce a lot of sunlight into

space, which would have warmed the

earth. This is negative feedback. At the

same time, clouds are made up of

concentrated greenhouse gas, and

can also provide positive feedback.

Clouds will play an important role

in climate change, but no one

is sure yet whether they will

ultimately end up warming

or cooling the earth.

Water vapor is a greenhouse gas, and helps to

warm the earth. At higher temperatures, more

water evaporates, putting more water vapor into

the air, which heats the earth even more. This

is another important positive feedback loop.

Ice is reflective. When sun-

light is reflected into space,

it doesnt contribute to the

greenhouse effect. So the ice

caps help to limit warming.

As things heat up, the ice

melts, revealing the darker

ocean beneath, which

absorbs more radiation and

warms, melting more sea ice.

This cycle is a positve

feedback loop.

Feedback loops are self-perpetuating cycles

that enhance or dampen the greenhouse effect.

The ones illustrated here are just a few examples of

the many feedback loops at work on the climate. Without

feedback, humans could double the amount of CO2

in the

atmosphere (which were in the process of doing) and the earthsaverage temperature would rise by about 1.2C. Thats enough to cause

noticeable changes in climate, but probably not catastrophic ones. With

feedback the problem is more complicated. It boils down toclimate

sensitivity: Will negative and positive feedbacks cancel each other out,

or will they cause a catastrophic rise in temperature?

SOLar radiation

What are

FEEDBACK LOOPS?

The Greenhouse effect

Feedback

1

Infrared radiation2

Greenhouse gas3

4

7

6

5

Global Temperature and co2

Year

lobal Temperature Change (5-year mean)

Atmospheric CO2 Concentrations

Kyoto Treaty Members

Asia-Pacific Partnership for CleanDevelopment and Climate Members

Members of both

No action

ppmC

ILLUSTRATION:SILO

Global temperature average

(19501980)

Each point on the temperature line represents

an average taken over five years. The globaltemperature average taken for 1935-1940, forinstance, is just under 0.1C above the baseline.


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The Key Questionin nuclear engineering:

Nuclear reactors are an important

carbon-free source of power. We

are likely to see a surge in their

construction in the next few years.

Why are some people concerned about nuclear power?The issue: soundbiteUranium used in reactors has been enriched to create a higher concentration of U-235 than occurs in nature. Countries with the technology to enrich uranium

for power can expand their capabilities to create highly enriched uranium for weapons. Some reactors use plutonium, another weapons material, or create it as

a waste product. Due to proliferation concerns, the International Atomic Energy Agency keeps close tabs on how and where nuclear materials are used. Even

regular nuclear wastethe radioactive and heavy metals that are the products of fissionis dangerous, making it a concern everywhere nuclear power is used.

Consultants:PerPetersona

ndDanielKammen,Professors,NuclearEngeneeringatU

CBerkeley

MapData:TheNuclearEnergyInstitute/TheInternationalAtomicEnergyAgency(IAEA)

Gra

phData:IAEA

Illustrator:CybuRichli-www.cybu.ch

Writer:JoshuaBraun

How can reactors be designedto work at maximum efficiency,to be safe and self-regulating,and to minimize nuclear waste?

Cribsheet #5

Seeds Tear-outable tool for living in the 21st century

Nuclear Fission

self regulation

Modern reactors are designed to be safe and self-regulating.

In the same way that an airplane is designed to level out

naturally after being jostled, reactors are engineered to

maintain safe levels of chain reaction under any circumstances.

the nuclear reaction

Superheated steam forces its way out of

the steam generator. It cranks a

turbine, which produces

electricity. As the water in the

steam generator boils, it also

siphons heat away from the water

in the pipe flowing to the reactor

vessel. This helps to cool the reactor. In

another type of nuclear plant, called a

boiling water reactor, the steam powering the

turbine comes directly from the reactor vessel.

steam generation

electricity

generation

Nuclear fission occurs when a neutron strikes the nucleus of

an atom and splits it apart. Most of the nucleus of the

original atom goes to form new, smaller atoms. In

addition, several neutrons may split off from

the original atom during fission. But the

mass of all these neutrons and fission

products does not add up to the mass

of the original atom. Thats because

when the atom splits, some of its mass

is converted directly into energy.

Nuclear reactors and warheads can

employ the uranium isotope U-235.

When the U-235 atom splits, it frees

two or three neutrons, which then

fly off and split other U-235

atoms in close proximity,

starting a chain reaction.

In warheads, the chain reaction multiplies exponentially,

giving off a huge amount of energy at once in a nuclear

explosion. In nuclear reactors, a chain reaction must be

controlled to create a safe, harvestable source of energy.

In the reactor vessel, cylindrical uranium pellets are stacked

into long fuel rods. It is within bundles of these rods that

the chain reaction occurs. Together they are called the

reactor. To keep the reaction under control:

Low concentrations of U-235 are used in the reactor, so

not every neutron will strike a nucleus.

Retractable control rods, made of a material that absorbs

neutrons, can be lowered into the reactor to siphon off

neutrons that would otherwise multiply the chain reaction.

3

4

1

2

3

2

Much of the energy released by the chain reaction is

manifested as heat. The fuel rods are placed inside a

pressurized chamber full of water. Because this reactor

vessel is kept at high pressure, the water will reach

temperatures much greater than 100 C.

steam condensation4

After the steam cranks the turbine, it is condensed back

into a liquid as it runs over a pipe filled with cold water

flowing from the cooling tower. It is then recycled into the

steam generator. The water from the cooling tower heats

up during this process and some of it is released as steam.

It is then replaced from a nearby body of water.

This superheated water is pumped through a pipe that runs,

like a heating element, through a second chamber called

the steam generator. The steam generator is partially filled

with clean water, which is boiled by the

heated pipe running from the reactor

vessel. The steam generator is also

kept at high pressure (though its

lower than that of the reactor vessel).

1

power needs supplied by nuclear plants

200

350

250

400

450Nuclear

Hydro

1-20

20-40

40-60

60-80

Biomass

Gases

world energy consumption by source

300 Solids

Liquids

control rods condenser

cooling tower

reactor

generator

steam generator

turbine

reactor vessel

pump

BASIC PRINCIPLE

Heat flows from one part of the powerplant to the next. As one part warms up,heat flows out of the previous one,allowing it to cool, so s afe operatingtemperatures are maintained.

50

Year

1970 1975 1980 1985 1990 1995 2000 2004

100

150

0

6.34%2.22%6.75%

23.04%

26.08%

35.09%

This graph shows the steady increase in globalenergy consumption since 1970. Combustibleliquid and solid fuels, like gasoline and coal,remain our dominant sources of energy.

Percentby country

1018JOULES

(EQUIVALENTTO

23.9

MEGATONNESOFOIL)


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ILLUSTRATION NOTE

The sample biome includes a river, an ocean, a volcano,

and a glacier. Geometric shapes such as spheres, cones, and

icosahedrons indicate different species, and deceased

organisms are darkened.


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FeSi

OC

HeH

He

H

C

Ne

H

CH

e

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OC

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He

He

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Light is electromagnetic radiation

that moves through space at 300,000

kilometers per second and acts

as both a wave and a particle.

Harnessing LightTHE ISSUE: SOUNDBITE

Many of the past centurys major scientific and technological advances came from studying the physics of light, and this trend is certain to extend

well into the future. Our understanding of light has allowed us to study the universe on the smallest and largest of scales. It has given us applications

like radio, television, radar, medical x-rays, microwave ovens, and wireless computer networking, to name but a few. Now, emerging technologies

like quantum computing, efficient solar power, and light-based spacecraft propulsion are poised to further transform science and our society.

Like the sound of a passing siren that rises and then falls in pitch as it approaches and recedes, light waves from a source

moving in relation to an observer exhibit similar shifts. As a light source approaches an observer its light is compressedto shorter wavelengths this is ablueshift. As a light source recedes, its light is stretched this is a redshift. Theredshifts and blueshifts for most slow-moving, earthbound objects are too small to be easily noticed. But on astronomicalscales, we can measure the motions of planets, stars, and galaxies using this effect.

In theory, lights shortest possible wavelength is trillions of times smaller than the diameter of a proton, and light may have

no upper limit on its wavelength. In practice, we can detect light with wavelengths ranging from thousands of kilometersdown to less than the size of an atomic nucleus. The electromagnetic spectrum is the continuum of wavelengths betweenthese extremes. Our eyes can only see light between 400 and 700 nanometers in wavelengtha miniscule portion of theentire electromagnetic spectrum.

The Electromagnetic Spectrum Redshift/ Blueshift

LIGHT aND MaTTEREach kind of atom in a substanceabsorbs characteristic wavelengthsof light; all other wavelengthsare reflected back or transmittedthrough. Different mixtures ofatoms reflect different wave-lengths, creating the diversity ofcolors we perceive in the worldaround us.

Because light can originate from theexcitation of electrons in atoms, andeach element of the periodic tablehas a unique atomic configurationof electrons, the elementalcomposition of any substance canbe discovered through observingthe spectrum it produces when itselectrons are energized. Forinstance, burning a sample ofhydrogen gas creates light. Runningthat light through a prism producesa distinct emission spectrum .Conversely, light passing througha cool cloud of hydrogen gas andthen a prism produces a uniqueabsorption spectrum . Bystudying spectra like these, we canmeasure the chemical compositionof practically anything on Earth,as well as the atmospheres of otherplanets, the Sun, and even thedistant stars.

Lower energy / Longer wavelength Higher energy / Shorter wavelength

Wavelength

WaVE-PaRTICLE DUaLITYLight usually behaves like a continuous wave, but it can also act as if it iscomposed of discrete particles of energy called photons.

Lights wave-like nature can be revealed when light diffracts through two slitsand shines onto another surface. Light passing through the slits acts as twowaves that disrupt and interfere with each other. Where the waves peaksand troughs overlap, they combine to produce a characteristic interferencepattern of light and dark bands.

But when light of different wavelengths shines on a metal surface,the existence of individual photons becomes clear. If an electron in themetal absorbs more than a threshold amount of energy, it breaks freeand zips away. Since shorter wavelengths contain more energy, a verybright but long-wavelength light will have no effect on the metal,while a very dim but short-wavelength light will release electrons.The energy of ejected electrons increases not with greater amounts oflight, but with more energetic wavelengths. This means each electronejection depends on the energy of an individual photon.

Light is energy that travels as a wave through space. Most of the light we encounter in everyday life is produced by nuclear fusion in stars or theenergetic excitation of electrons in atoms. A wave of light actually has two components: an electric field, and a magnetic field. Consequentlylight is also called electromagnetic radiation. Electricity and magnetism are interdependent: One can produce the other. Similar to how passinga magnet over a coil of copper wire briefly generates electricity, or how a constant electric current can magnetize iron, a light waves oscillatingelectric and magnetic fields reinforce each other and propagate through empty space at nearly 300,000 kilometers per second. This value isknown as the speed of light, and appears to be the universes ultimate speed limitnothing travels through space faster.

All forms of lightradio waves, microwaves, infrared, visible, ultraviolet, x-rays,and gamma raysare identical except for their wavelength. Lights wavelengthdetermines its energy; the shorter wavelengths have higher energy. Light from mostnatural sources contains multiple wavelengths. White light contains all visible wave-lengths. Refracting it through a prism separates them into a continuous spectrum .

light

Wavelength

Electric field

Magnetic field

Interferencepattern

Light source

High intensity,low energy

light

Low intensity,high energy

light

Ejectedelectron

Radio waves

10km 1km 100m 10m 1m 10cm 1cm 1mm 100m 10m 1m 100nm 10nm 1nm 100pm 10pm 1pm 100fm 10fm 1fm

Microwaves Infrared

Visible

Ultraviolet X-rays Gamma rays

What is light and wheredoes it come from?How can light be usedto investigate the worldaround us?

CriBsheet#13

Reference:Universe,

RobertDinwiddieetal.,

DKPublishingInc.,2

005

Illustrator:CybuRichliwww.cybu.c

h

Wr

iter:LeeBillings

1

2

2

3

3

Metal plate


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SOUNDBITE

We have found nearly 300 exoplanets

using radial velocity, transits, and

microlensing, and are likely to find an

Earth-mass exoplanet in the near future.

discovering haBitaBle worldsTHE ISSUE:Astronomers using radial velocity, transit, or microlensing searches are racing to discover the first Earthlike exoplanet. New telescopes, improved

data analysis, and the realization that red dwarf stars are excellent planet-hunting targets imply that the first Earth-mass exoplanet in a habitable

zone will be found in the next few years. If that planet transits its star, we may be able to analyze its atmosphere. If its atmosphere contains water,

oxygen, carbon dioxide, and methane, well have found more than a habitable worldwell have discovered the first credible signature of alien life.

Life as we know it requires liquid water. If a planet orbits its star too closely, any water evaporates into steam; too far away,

and water freezes into ice. The sweet spot between these extremes is the " habitable zone" (HZ). A star's mass determinesits HZ; the more massive a star is, the brighter it shines, pushing the HZ further out. Astronomers now believe the firstEarth-mass exoplanet within an HZ will be found around a red dwarf, the smallest, dimmest, most numerous type of star inour galaxy: Planets in a red dwarf's HZ orbit so closely that they should be detectable with radial velocity or transit searches.

The vast majority of detected exoplanets have been gas giants like Jupiter and Saturn that closely orbit their stars. But as

observational data accumulate and new search projects come online, scientists have begun discerning the telltale signaturesof smaller, terrestrial exoplanets several times the Earth's mass. This graph plots the diminishing size of the smallest knownexoplanets: In little more than a decade, the record has dropped over an order of magnitude. Extrapolating from this trend,astronomers should begin detecting Earth-mass exoplanets around 2011 or 2012, though this may happen much sooner.

refining the search haBitaBle zones

2

1

0.5

0 0.1 1 10 40

MarsEarth

VenusMercury

Habitable Zone

Radius of orbit relativeto EarthsNot to scale

Massofstarrelative

toSun

NeptuneUranus

SaturnJupiter

20001995 2005 2010 2015

1

0.1

0.01

0.001

PlanetaryMass(1=Jupiter)

planetary transits

The transit method finds planets by looking at the total amount of light from a star over time.If a planet passes in front of its star as viewed from Earth, the star's light slightly dims duringthe planet's transit . Measuring how much the starlight diminishes reveals the planets diameter.Many exoplanets can be studied with both radial velocity and transits. The combined data canallow astronomers to estimate not only a planet's size, mass, and orbit, but also its density,temperature, and atmospheric composition.

Both radial velocity and transit methods overwhelmingly favor detecting Jupiter-mass planets thatorbit their stars at a fraction of the distance between Mercury and our Sun.

In 1543, Polish astronomer Nicolaus Copernicus published On theRevolutions of the Heavenly Spheres, showing that the Earth, far frombeing the privileged center of the universe, is just another planet orbitingthe Sun. Since then, the discovery that our Sun is a typical star among thebillions in the Milky Way, which in turn is but one of the billions ofgalaxies we observe in all directions, has strengthened the notion thatour place in the universe is merely ordinary. This assumption of ourcosmic mediocrity is called the Copernican principle.

exoplanets

Do planets form aroundother stars? How canwe detect and studythem? Are there otherplanets like Earth?

CriBsheet#14

Illustrator:Southsouthwestwww.southsouthwest.com.au

Writer:LeeBillingsConsultant:GregLa

ughlin,ProfessorofAstronomyandAstrophysics,UniversityofCalifornia,SantaCruz.HabitableZone:Derivedfrom

animagecreatedbyGabrielRodriguezAlberich,viewab

leathttp://en.wikipedia.org/wiki/Image:Habitable_zone-e

n.svg.

ThisHabitableZoneimageisusedandreleasedunderthetermsoftheGFDL(http://en.wikipedia.org/wiki/GNU_Free_Documentation_L

icense).LowestExoplane

tMasses:JeanSchneider'sExtrasolarPlanetsEncyclopedia

,http://exoplanet.eu/

microlensingGravitational microlensing is anewer technique to find exoplanetsthat uses effects predicted byEinstein's theory of generalrelativity. Just as a magnifying glasscan enlarge an image, a star'sgravitational field can bendspace and magnify light in aprocess called microlensing. Whena distant bright star aligns with adimmer lensing star that is closer to

Earth, the distant stars lightbrightens . If planets orbiting thelensing star are perfectly aligned,they too will magnify the distantstar's light, allowing astronomers toestimate their mass and orbitaldistance . Microlensing worksbest for planets orbiting their starsat Earth-Sun distances or greater.Since each chance alignment onlyoccurs once, microlensing can't beused to closely study individualplanetary systems, but rather

provides a statistical sample ofexoplanet populations.

But perhaps the Copernican principle is wrong. Compared to other terrestrialplanets in our solar system, the Earth seems special. It alone has oceans ofwater, plate tectonics, and a large moon. As far as we know, it alone hostslife. Since the first detections of planets orbiting other stars in the mid-1990s,we've discovered hundreds of exoplanets, but none resembles the Earth.Could we and our world be unique? In the near future, this question will beanswered by one of three detection methods: stellar radial velocity,planetary transits, and gravitational microlensing.

Time

Brightness

3

radial velocityA planet orbiting a star causes the

star to wobble back and forth.The radial velocity method detectsthis wobble by examining the colorof starlight: As the star movestoward an observer, its lightbecomesbluer ; as it moves away,its light becomes redder . Byanalyzing these color shifts overtime, the presence of planets, alongwith their masses and orbits, canbe inferred. So far most exoplanetshave been found using radialvelocity measurements.

2

51 Peg b

HD 75289 b

HD 49674 b

OGLE-05-390L b

HD 16141 b

55 Cnc e

Gl 581 c

BackgroundStar

LensingStar

Planet

Telescope

Lensed

Image

Lightcurve

1 2 3 4

Lightcurve

Time

Brightness

1 2

Absorption Spectrum

3

A

B

A B

Earth


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Intel coounder Gordon Moore amously observed nearly hal a centuryago that the number o transistors economically crammed into a singlecomputer chip was doubling every two years. This trend toward miniatur-ization is seen throughout the history o modern computing. Today ele-ments o microchips are only tens o nanometers in size, and i miniaturiza-tion continues, microchip components will eventually reach atomic scales,where their properties will be dictated by quantum mechanics.

Miniaturization may ultimately lead to quantum computers, which usequantum eects to perorm calculations. Quantum computers could, inprinciple, solve certain problems exponentially aster than the best knownclassical methods with ar-reaching consequences or cryptography andthe simulation o quantum physics. Simple quantum computers have al-ready been built, but most experts believe robust and powerul systemsremain many years away.

Both classical and quantum computersperorm calculations by manipulatinginormation. Classical computersrepresent inormation as binary digits,

or bits, which can have values oeither 0 or 1. Quantum computersrepresent inormation as quantumbits, or qubits. Many dierentphysical objects can be used as qubits,such as atoms, photons, or electrons.Paradoxically, a qubit can represent0 and 1, as well as other possiblevalues, at the same time, in what iscalled a quantum superposition.This allows a qubit to simultaneouslyuse many more inormationalstates or computation and isresponsible or quantum computings

advantages over classical computing.In the illustration above, an atomicspin represents a qubit. An upspin corresponds to 0; a downspinequates to 1. A quantum superpositionencompasses 0, 1 and all possiblevalues in between.

QUANTUM COMPUTING

CriBsheet #15

Seeds Tear-outable tool for living in the 21st centurythe Key Questions ofQuantum computing:

What is a quantum

computer, and how doesit dier rom moderncomputers? How can weuse quantum computing?

Computer scientists classiy a problems difculty by the number o computational steps an algorithm requires to solve it.Problems that a classical computer can quickly solve are called P (polynomial time) problems. In P problems, as the problemsize n increases, the number o steps to solve it grows polynomially, or instance by n2. Determining whether a number isprime is an example o a P problem. NP (nondeterministic polynomial time) problems consist o all problems or which theanswers are easy to check, even though fnding those answers may take an exponential number o computational steps,

such as2n. Every P problem is also an NP problem, but computer scientists believe that not all NP problems are P problems.BQP (bounded-error, quantumpolynomial time) problems are the class o problems that quantum computers can ef-ciently solve. Factoring the product o two large prime numbers is an example o a problem that is both an NP and a BQPproblem. Though no one knows or certain, it appears that BQP does not include most NP problems. This means that ormost NP problems, quantum computers may oer no signifcant advantages over classical computers.

Quantum computers could theoreti-cally revolutionize our ability to solvecertain kinds o computational prob-lems, but frst we must discover howbest to build and use them.

THE ISSUE:can we Build a sophisticated quantum computer?A company called D-Wave Systems has exhibited what it controversially calls the worlds frst commercial quantum computer, but most expertstreat these claims with considerable skepticism. Some o the best minds in physics today are struggling to build simple quantum computers, andcomputer scientists are still seeking their ideal applications. It seems that even i practical, powerul quantum computing existed today, we prob-ably wouldnt know how to best use it. Ironically, i building sophisticated quantum computers turns out to be impossible in principle, this maybe the biggest breakthrough o all, as it would imply that our undamental understanding o the quantum world is incorrect.

What ProBlems Can a Quantum Computer Solve?

quantum computing 101

interference patterns

The latent possibilities within asuperposition can actually interere

with each other, constructivelyreinorcing or destructivelycanceling each other toorm the nal denitestate. The programmero a quantum computermust choreograph thecalculation in such a waythat computational pathsleading to a wrong answerwill destructively interere witheach other, canceling eachother out and leavingonly the right

answers to beobserved.

FINDING aN aNSWER

The ability o quantum objects to simultaneously holdmultiple, seemingly conficting values is at the heart o

quantum computing. This state is called a quantumsuperposition (at right). Superpositions occurall the time at the quantum level. In act, any

isolated quantum object like an atom or aphoton is in a superposition. But as soon

as the object interacts with some-thing else, such as another atom

or photon, the superposition isliable to collapse. The collapse

o a superposition is calleddecoherence. Decoher-ence is essentially an acto measurement, whereall possible states in the

superposition collapseinto the one ultimately

observed. I the quantumcomputers qubits suer too

much decoherence beore thecalculation is completed, the in-

ormation will be irretrievablylost and the probability o

producing a correctanswer becomesessentially zero.

Perorm a measurement, collapsing the qubits superposition. By repeating these steps and combining the results, we can reliably obtain the actors o a very large number.

Hundreds or thousands o qubits would be neededto actor very large numbers. For convenience, here weveillustrated only our.

Choreographquantum

intererence to allowpaths to correct

answers to reinorceeach other.

Easily solvedby quantum

computers

Computationaltime

Easily solvedby classicalcomputers

Factoringa verylargenumber

Testing ia number isprime

0 1 2 3 4 5Problem size (bits)

6 7 8 9

n

n2

2n

Illustrator:ThomasPorostocky

www.porostocky.com

Writer:LeeBillingsConsultant:Scott

Aaronson,

AssistantProfessorofElectricalEngineeringandComputerScience,

MassachusettsInstituteofTechnology

Place thequbits in a superposition

over all o theirpossible confgurations

in preparationor initiating a

quantum intererencepattern.

The encryption vital or modern secure communications as-sumes that actoring large numbers in a reasonable amounto time is beyond the capabilities o todays commercialcomputers. In 1994 computer scientist Peter Shor devised analgorithm allowing a quantum computer to quickly actorlarge numbers. Thus, a powerul quantum computer couldbreak the worlds dominant encryption schemes, resultingin the need or new security methods. For perspective, to-days quantum computers are scarcely powerul enough toactor a number like 15. At right, a schematic illustrationoutlining how Shors algorithm works:

BQP

NP

0

1

P

Seeds Tear-outable tool for living in the 21st century the Key Question ofSYNTHETIC BIOLOGY


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Life, even at its most minuscule, can elicit incredible change on a planetary

scale. Consider the oxygen youre breathing. Its presence in Earthsatmosphere is a biochemical accident, a waste product of photosynthesizingorganisms. Together, organisms cycle essential nutrients like carbon andnitrogen around the planet; even on its own, an organism can fabricateuseful materials, and eachthanks to its cellular machineryis capable ofprocessing the information found in its genetic code.

After biologists learned to decode genes, they soon learned to redirect

the power of life by manipulating DNA. Scientists have developednumerous techniques to read and modify DNA; those techniques form thebasis of genetic engineering, but many are inefficient. Synthetic biology isan effort to develop better tools and technologies for engineering biologicalsystems, with the overarching goal of creating new biological functionsand enhancing those that already exist.

SynThetic biologyCriBsheet #16

Seed s Tear outable tool for living in the 21st centurySYNTHETIC BIOLOGY:

Can we learn toprogram DNA and livingorganisms as well as orbetter than we currentlyprogram computers?

As costs plummet, the largest barrier against more individuals taking advantage of DNA synthesis is the inherent complex-ity of biological systems. Just as software developers used to painstakingly program in binary machine language but nowrely on software compilers and sophisticated programming languages, synthetic biologists today await powerful comput-er-aided abstraction tools that simplify biologys complexity into easier formats. Many need to be developed.

Since BioBrick parts are open source and in the public domain, anyone can use or modify existing BioBrick sequences freeof charge and also submit new ones to online databases. This openness has driven significant growth in the number ofBioBrick parts, as well as the creation of academic contests like the annual international Genetically Engineered Machine(iGEM) competition. As more BioBrick sequences accumulate, the collective power of synthetic biology increases.

THE ISSUE:the democratization of BiotechnologyIf synthetic biologists continue crafting tools that simplify genetic engineering, it will become much easier for anyone, regardless of training,to construct novel biological systems. Synthetic biology techniques are dual use: The same methods that could lead to a cancer-fighting bac-terium might also make deadly biological weapons; the same methods that promote ecologically unsound crop monocultures could also causebeneficial flowerings of engineered biological diversity. Ultimately, governments, large corporations, and international regulatory bodies bythemselves may not be able to control whether synthetic biology is wisely usedthat choice will also be up to each of us.

Cost of Commercial Gene Synthesis Cumulative size of BioBrick dataBase

constructing dna

DNA sequencing allows researchersto read genetic material, convertinginformation encoded within DNAmolecules into sequence data. DNA

synthesis allows biologists to writegenetic material from scratch, usingsequence data to assemble DNAmolecules 1. Researchers are workingto improve the power of DNA synthesistechnology, but the bigger challenge is toinvent new languages and grammarsthat enable the writing of many newgenetic programs, each coding foruseful behaviors, such as the productionof fuels, foods, or medicines.

genetic programs

To make programming DNA easier,synthetic biologists are creating banks ofstandardized DNA sequences, or parts,that each perform a specific function. Forexample, the BioBricks Foundation, anopen-source initiative from MIT, Harvard,and the University of California, SanFrancisco, is doing this by developingBioBrick parts, functional sequencesof DNA with uniform prefix and suffixsequences. This structural standardallows BioBrick sequences to link togetherand act as interchangeable parts.

An efficient genetic machine also requires a communications standard.For example, one type of BioBrick part acts as a receiver for extracellularsignals (conveyed via a modified sugar molecule, 3OC

6HSL ) and produces

an intracellular signal that other BioBrick parts can respond to. BioBrickparts communicate using RNA polymerase ; the more sugar fed toa receiver, the more polymerase it will emit each second 2. There is adirect analogy to electricity: Just as an ampere is the unit that describeshow many electrons flow past any given point on a wire each second,polymerase per second, or PoPS, describes the rate at which polymerase

molecules flow down a DNA strand. The strength of the PoPS currentcontrols how strongly a plugged in BioBrick part will respond. A BioBricksequence recently developed by college students produces bubbles ofprotein, called vesicles , inside a cell. Plugging the bubble BioBrick part

into the PoPS current from a BioBrick receiver creates a new geneticprogram 3 that can alter the number of vesicles created within a cell;more sugar means more PoPS, which in turn produces more vesicles and amore buoyant cell 4. This is but one example of a genetic program madepossible by standardized synthetic biological parts.

Sequence data

Raw materials (bases)

Illustrator:ThomasPorostockywww.porostocky.com

Writers:LeeBillingsandDrewEndyConsultant:DrewEndy,AssistantProfessorofBiologicalEngineerin

g,

MassachusettsInstituteofTechnology

Powerful new tools and technologieswill ultimately give individuals theability to design and modify customgenomes and construct artificial liv-ing organisms from scratch.

Biotechnology Basics

Genetic information is encoded byfour nucleotides, or bases, that arepart of DNAs molecular structure.To obtain this information, scientistsread these bases in a processcalled DNA sequencing 11. Once asequence is known, it can be isolatedby restriction enzymes, proteinsthat sever DNA strands at specificsequences 22. A genetic engineercan insert such snippets of DNA intoother DNA strands 33. Snippets ofDNA can also be amplified (copiedmany times) by the polymerase chainreaction (PCR), making them easierto work with 44. Polymerases aremolecules that travel along a strandof DNA to perform various tasks.Researchers also use PCR to selectivelymutate small portions of genes.These methods enable researchers tomanually edit DNA, which can thenbe incorporated into living organismsvia several techniques collectively

called DNA transformation.

...GATTACAG...

...GATTACAGATTA...

1

2

3

ublic domain, anyone can use or modify existing BioBrick sequences freeatabases. This openness has driven significant growth in the number ofc contests like the annual international Genetically Engineered Machineaccumulate, the collective power of synthetic biology increases.

of training,fighting bac-ld also causery bodies by

oBrick dataBase

current. A BioBric

bbles oBrick partw genetic

n a cell;esicles and aram made

owerful new tools and technologieswill ultimately give individuals theability to design and modify custom

enomes and construct artificial liv-ng organisms from scratch.

2

3

4

1

2

3 4

($ per base pair) # of Standard Parts

20020

2

4

6

8

10

12

14

16

18

20

2003 2004 2005 2006 2007 2008

$4-8

$2-4 $2

$1-2 $0.75-1.25

$1-1.50$10-16

20020

200

400

600

800

1000

1200

1400

1600

1800

2000

2003 2004 2005 2006 2007 2008

12 60 100

400

2000

1100200

+ =

SyntheticDNA

Extracellularsignaling molecule

RNA polymerase

BioBrick receiver


17/18

Seeds Tear-outable tool for living in the 21st centuryTHE KEY QUESTIONSOF BIOFUELS:


18/18

biofuelsCriBsheet #18

OF BIOFUELS:

Are biofuels a viablereplacement for fossilfuels? How are they made,and can their productionbe improved?

THE ISSUE:THE NEXT GENERATION OF BIOFUELSThe frst generation o modern biouels was made rom ood crops like corn because processing these plants is relatively easy, but their energyyields are low and their negative eects are many. Second generation biouels like cellulosic ethanol are made rom inedible materials likeagricultural waste and wood chips, but their production has yet to be perected, and the amount o energy they could deliver is unlikely to ulfllthe entirety o our growing energy needs. Viable biouels await us in the third generation or beyond, when highly energy-efcient productiono uel rom algae or genetically modifed microorganisms could become a reality.

out o rying pan,into freUsing the same crop as a sourceor both ood and energyincreases demand or it, whichcan cause rapid increases in oodprices. When using corn, onlythe kernels are used and energystored in other parts o the plantgoes to waste. Fortunately,a more complex process can

create ethanol rom cellulose,the main component o plantstems and leaves; this process isless disruptive to the ood supplyand uses material that wouldotherwise be wasted.

Though in theory ethanolcan be carbon-neutral, inpractice growing and harvestingcorn or cellulose uses substantialamounts o ossil uels. This

ermentation anddistillationOnce the sugar is extracted rom thecornstarch or cellulose, it is mixed withyeast or other microbes6. The microbes

erment the sugar into alcohol, releasingcarbon dioxide as a byproduct and leav-ing behind an unermented mass calledstillage, which can be recovered andused as a eed supplement or livestock.When ermentation is complete, themixture is distilled and treated withchemicals to remove water, resultingin uel-grade ethanol that can then beblended with gasoline and transportedto pumping stations or distribution 7.

pretreatment andextractionAter harvest, neither corn nor celluloseis immediately convertible to ethanol,which is a direct product o the sugarthats extracted and ermented. Severaldierent processes can extract sugarrom corn and cellulose, but eachrequires pretreatment o the sourcematerial to make extraction easier. Forcorn, the kernels are milled to producecornstarch 1, a mixture o two largemolecules comprising chains o the sug-

ar glucose; an enzyme called amylasethen breaks down the mixture into glu-cose2. Getting glucose rom cellulose-rich plant material is more difcult. Thematerial is pretreated with acids, steam,or ammonia to ree the cellulose romplant-cell walls3. Like starch, celluloseis made o chains o glucose molecules,but its molecules have ar more bondsbetween them. And so, celluloserequires multiple enzymes to break upinto glucose4. Lignin, another com-ponent o plants, must be separated

rom the glucose-rich mixture beoreermentation 5. Consequently, cellulosicethanol production currently lags arbehind ethanol production rom corn,sugarcane, and other ood crops.

making ethanolProducing ethanol rom either corn or celluloserequires our basic steps: growth and harvest,pretreatment and extraction o sugars, ermen-tation, and distillation.

reliance on ossil uelsdecreases the ratio o

energy provided by theethanol versus the energyspent in growing its sourcecrop. While corn is easierthan cellulose to convert intoethanol, it requires more resourcesto grow than many other cellulosesources. In general, using agricultural crops or biouelposes problems o environmental degradation and re-source depletion similar to those that occur in other ormso industrial agriculture.

Illustrator:BryanChristiewww.bryanchrist

iedesign.com

Writer:LeeBillingsGraphdata:AnnualEnergyOutlook2008,

USDepartmentofEnergy,EnergyInformationAdministration.

/AFarrelletal.(2006)EthanolCanContributetoEnergyandEnvironmentalGoals.

Scie

nce311:506-508

Though promising as alternative energysources, biofuels can have social, envi-ronmental, and energy costs rivalingthose of fossil fuels. Future generationsof biofuels may solve these problems.

ENZYME (AMYLASE)

YEAST

GLUCOSE

CELLULOSE

GLUCOSEENZYMES

GLUCOSE

STARCH

As US biouel production ramps up, more ethanol will be mixed with the gasoline supply. Evenby 2030, however, ossil uels are projected to remain the primary constituents o gasoline.

Today both ethanol and gasoline production rely on energy rom ossil uels. Producing ethanolrom cellulose rather than crops like corn will almost certainly require much less ossil-uel energy.

Biouel Content o U.S. Gasoline Supply ossil uels or Biouels

RISING ENERGY COSTS and con-cerns over climate change romemissions o CO

2have renewed

interest in moving beyond ossiluels. This is especially true wheretransportation is concerned, asit accounts or 70 percent ooil burned in the United States.Biouelsuels made romliving thingsare one potentialreplacement. Biouels come inmany orms, such as wood, ma-nure, and animal and vegetable

oils. Unlike ossil uels, biouelsare renewable and potentiallycarbon-neutral: Burning a plantreleases no more carbon than itabsorbed while growing. In theUS todays predominant biouel isethanol. Typically produced romcorn, American ethanol worksas an alternative to gasoline inmost cars and trucks. But corn-based ethanol may cause moreproblems than it solves.

150

100

50

2006

BILLION

GALLONS

2015 2030

MEGAJOULES OF FOSSILENERGY NEEDED TO PRODUCEEACH MEGAJOULE OF FUEL

Cellulosic Ethanol

Ethanol Today

Gasoline

Biouel content

Fossil Fuel content

PRETREATMENT &

EXTRACTION

GROWTH &

HARVEST

FERMENTATION

DISTILLATION

0.10

0.774

1.19

1

2

3

5

4

6

7

Seed Magazine: apuntes para el siglo XXI

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