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THE HINDU IN SCHOOL I MONDAY I APRIL 13 I 2015

3SCIENCE & TECHWord of the dayPredatory (Adjective): Living by eating other animals/ Exploiting othersUsed in a sentence: The real estate union claimed that their pricingwas not predatorySuggested by: M. Karthik Balaji. Your turn! Pick a word from today’sThe Hindu in School, the meaning of which you do not know and send itto us at school@thehindu.co.in. (Subject: Word of the day)

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When two people discover something si-multaneously, or within weeks of each oth-er, working independently, you expect bothto be rewarded. But if only one of them picksup the Nobel Prize, while the other isn’tgiven the entire credit, it definitely lends fora story. Yes, I’m referring to the discovery ofVitamin C and the two men behind it thatwe looked at last week.

This time around, we are going to see howtwo people worked together to change thecourse of their chosen field. Better still, bothof them were jointly awarded the NobelPrize in Physics in 1951 “for their pioneerwork on the transmutation of atomic nucleiby artificially accelerated atomic particles”.Going over the head? Let's split up and findout…

John Cockcroft was born in 1897 to afamily of cotton manufacturers. A variededucational background that includedmathematics at Manchester University,electrical engineering at the College ofTechnology in Manchester and Mathemat-ical Tripos at St John’s College, Cambridgemeant that he was one of those few theoret-icians who could put together his mathe-matical and engineering skills. These stintsof education were interspersed by theWorld War I and a period when he served asan apprentice with an electrical company.

Ernest Walton was born in 1903 and waseducated in Belfast and Dublin. He excelledin mathematics and science while withTrinity College, Dublin and graduated in1926 with first class honours in mathemat-ics and experimental science.

Cockcroft and Walton came togetherwhile at the Cavendish laboratory underErnest Rutherford. In 1928, George Gamowshowed that particles could tunnel through

potential barriers byapplying the newlyavailable quantum me-chanics. Cockcroft un-derstood theimplications of Ga-mow’s tunnelling the-ory - that a much lesserenergy than earlierthought might be suffi-cient for a proton to

penetrate the nucleus.By 1929, they had built the Cockcroft-

Walton generator, which with a system ofcapacitors and thermionic rectifiers couldreach voltages up to 600,000 volts. It tookthem three more years but on April 14, 1932,the research duo bombarded a layer of lithi-um with hydrogen in a discharge tube thathad been accelerated using their generator.

The result? The lithium broke into twohelium nuclei and shot off in opposite direc-tions - an atom had been split and nucleartransmutation of one element (lithium) toanother (helium) had been achieved for thefirst time under human control.

Cockcroft and Walton also observed aloss in the total mass of the nuclei, whilemeasurements indicated that the total ki-netic energy of the helium nuclei were grea-ter than that of the original hydrogen andlithium nuclei. Even though these initialcomputations had experimental error, itprovided evidence of Einstein’s law (E =mc2) and laid the foundations for furtherscientific work to confirm the equation indetail.

The duo employed the Cockcroft-Waltonmultiplier for most the of their researchthat followed, which eventually led to thembagging the Nobel Prize in Physics in 1951.The Cockcroft-Walton circuit is not onlystill used to supply voltage in large particleaccelerators, but is also employed in every-day high voltage electronic devices like pho-tocopiers and x-ray machines.

When the atom wassplit…

Read on to find out more aboutCockcroft and Walton's NobelPrize-winning experiment

AN EYE FOR AN I

A.S.Ganesh

The history of our Solar Systemprobably started 4.57 billion yearsago when a fragment of a hugecloud of gas and dust started tocontract because of its own grav-ity, somewhere in interstellarspace. While contracting, it be-came denser and denser, until itscore became a star – our Sun. Butnot all the matter went straight tothe Sun...

A rotating diskRotation plays an important

role in the formation of a plane-tary system like our Solar System.In all likelihood, our parent cloudfragment had some rotation, andthis rotation accelerated uponcontraction. Have you ever triedspinning on a rotating chair? Ifyou do so (but be careful!), youcould notice that you would spinfaster when you pull your arms inclose to your chest than when youstretch them out wide. It wouldwork even better if you held some-thing heavy in your hands, but inall cases, the more you would curlup, the faster you would spin. Inthe same way, when our parentcloud fragment curled up, it start-ed to spin faster. As a result, the

increased rotation flattened it intoa disk, centered on the Sun. Such adisk made of gas and dust is knownas a protoplanetary disk, as this iswhere planets can form. All plane-ts and most other celestial bodies

in the Solar System indeed orbitapproximately in the same plane,which corresponds to the plane ofthe former protoplanetary disk.

From dust grains to planetsOur protoplanetary disk prob-

ably lasted “only” a few millionyears before being absorbed orblown away by the Sun, but mostof the planet formation could becompleted during that time. Ourparent cloud was mostly made ofgaseous hydrogen and helium,which are the main constituentsof the Universe, but also includedsmall dust grains. These grains aremade of elements originatingfrom stars and are ten to hundredtimes smaller than the dust parti-cles you can find in your home. Asthese solids collided with eachother, they grew until millimetersizes and settled at the midplaneof the disk. There, they could

coagulate further to form aste-roids (a kilometre to hundreds ofkilometres in size), which in turncould merge in planet-sized ob-jects, helped by their own grav-itational attraction.

Temperatures varied across thedisk, being higher closer to theSun than further out. While waterwas gaseous in the inner regions, itwas solid ice beyond a certain ra-dius called the “snow line”. Be-yond this radius, the presence ofice with the stony material en-hanced the growth of planets:planets formed below the snowline never exceeded the mass ofthe Earth, whereas outer planetsreached ten times more, at whichstage they even started to retainthe ambient gas. This led to theformation of giant gas planets,among which Jupiter is the large-st.

Although we still observe aclean separation between stone-dominated planets close to theSun (Mercury, Venus, Earth,Mars) and giant planets furtherout (Jupiter, Saturn, Uranus, Nep-tune), some astrophysicists havehypothesized that the orbits of thegiant planets changed significant-ly at different epochs in the histo-ry of the Solar System.

This would have had dramaticconsequences, notably on the fluxof asteroids near the inner plane-ts. But nowadays, the planets arefortunately on rather stable or-bits!

Emmanuel Jacquet is assistantprofessor at the French NationalMuseum of Natural History in Pa-ris, working on meteorites and theformation of the Solar System. Jo-nathan Freundlich is a PhD stu-dent at the Paris Observatory, inFrance, working on star formationand galaxy evolution. The authorscan be reached atjonathan.freundlich@obspm.fr.

A glimpse at the formation ofour Solar System

IT ALL STARTED HERE Solar system in formation: the HL Tauriprotoplanetary disk as seen by the ALMA telescope. PHOTO: ALMA (ESO/NAOJ/NRAO)

ALL ABOUT ALMA

● HL Tauri is 450 light-years from Earth and the staris less than a million years old, which makes itpretty young by astronomical standards. The darkrings on the ALMA image may indicate the positionsof planets under formation.

● ALMA is an array of telescopes located in theAtacama desert of Chile at 5000 metres altitudewhich observes the radio waves emitted byastrophysical objects such as stars and gas clouds.Each of its telescopes looks like a big satellite dish.

● The bigger a telescope is, the sharper its imagesare. ALMA dishes can be moved over distances upto 16 kilometres, making it one of the sharpesttelescopes ever built.

The remarkable story of how the Sun, the planets and other celestialobjects that make up the solar system came to beEmmanuel Jacquet & Jonathan Freundlich ASTROPHYSICAL SERIES

WASHINGTON: Palaeontolo-gists are restoring the goodname of Brontosaurus morethan a century after it wasdeemed scientifically inval-id and the famous dinosaurwas reclassified as anothergenus called Apatosaurus.

They unveiled on Tues-day an exhaustive analysisof Brontosaurus remains,first unearthed in the 1870s,and those of closely relateddinosaurs, determining thatthe immense, long-neckedplant-eater was not an Apa-tosaurus and deserved itsold name back.

Paleontologist EmanuelTschopp of Portugal's Uni-versidade Nova de Lisboacited important anatom-ical differences includingApatosaurus possessing awider neck than Brontosau-rus and being even moremassively built.

"The differences betweenApatosaurus and Bronto-saurus are numerousenough to revive Bronto-saurus as a separate genusfrom Apatosaurus,"Tschopp said.

Brontosaurus, whichlived in North Americaaround 150 million yearsago in the Jurassic Period,

was about 72 feet (22 me-ters) long and weighedabout 40 tons.

“Brontosaurus and T. rexare the two most popular di-nosaur names ever,” saidUniversidade Nova de Lis-boa paleontologist OctàvioMateus.

"Even 112 years after pa-leontologists considered itinvalid, the name Bronto-saurus still echoes in thepopular culture. It was in-deed a very cool dinosaurname."

"This will be like recover-ing Pluto as a planet again,"Mateus added, referring toastronomers' 2006 decisionto downgrade Pluto from afull-fledged planet to adwarf planet.How the confusion came about

After his team excavatedfossils of two huge long-necked dinosaurs, prolific19th century paleontologistOthniel Charles Marshnamed the first one Apato-saurus ("deceptive lizard")in 1877 and the second one

Brontosaurus ("thunder liz-ard") in 1879.

In 1903, paleontologistElmer Riggs declared thatBrontosaurus and Apato-saurus were too similar foreach to be considered a sep-arate genus. Because Apato-saurus was named first,under the rules of scientificnaming it supplantedBrontosaurus.

But the name was so pop-ular it survived its burial,with "Brontosaurus" andthings like "Bronto Burgers"appearing in numerousbooks, cartoons, movies andelsewhere.

Brontosaurus belongedto a group of dinosaurs withlong necks and tails and pil-lar-like legs called sauro-pods that included Earth'slargest land animals ever.

This study, published inthe scientific journal PeerJ,focused on the anatomy andrelationships among a cate-gory of sauropods called di-plodocids, which includesBrontosaurus, Apatosaurus,Diplodocus and others.Reuters

Brontosaurus is back!Deemed scientifically invalid Brontosaurus was reclassified under another genusApatosaurus. A century later, scientists have now clarified that the long-neckedplant-eater deserved its old name back

THE MAIN DIFFERENCEAn artist's rendering ofa Brontosaurus asresearchers see it today.Apatosaurus possess awider neck and have abuilt more massive thanBrontosaurus. PHOTO: REUTERS

● Brontosaurus,which lived inNorth Americaaround 150million years agoin the JurassicPeriod, wasabout 72 feet(22 meters) longand weighedabout 40 tons.

● Brontosaurusbelonged to agroup ofdinosaurs withlong necks andtails and pillar-like legs calledsauropods thatincluded Earth'slargest landanimals ever.

Alien life could be found by 2025: NASARecent discoveries suggest that the solar system and broader MilkyWay galaxy teem with environments that could support lifeWASHINGTON: If one is to believe in NASA, humanity is likely to witness the first signs of alien life in thenext 10 years or so.

Addressing a panel discussion last week on the space agency’s search for habitable worlds andalien life, NASA chief scientist Ellen Stofan said: “I think we are going to have strong indications oflife beyond Earth within a decade, and I think we are going to have definitive evidence within 20 to30 years.”

“We know where to look. We know how to look. In most cases, we have the technology, and we areon a path to implementing it. And so I think we’re definitely on the road,” he told the gathering.

The prospectusRecent discoveries suggest that the solar system and broader Milky Way galaxy teem with

environments that could support life as we know it.For example, oceans of liquid water slosh beneath the icy shells of the Jupiter moons Europa and

Ganymede, as well as that of the Saturn satellite Enceladus.“Oceans covered much of Mars in the ancient past, and seasonal dark streaks observed on the Red

Planet’s surface today may be caused by salty flowing water,” Stofan added.NASA’s Curiosity rover has found carbon-containing organic molecules and “fixed” nitrogen,

basic ingredients necessary for Earth-like life on the Martian surface, Space.com reported.NASA’s Kepler space telescope suggest that nearly every star in the sky hosts planets — and many

of these worlds may be habitable. IANS

WASHINGTON: NASA hasawarded a grant of US dol-lar 10 million to a Texas-based company to developa revolutionary engine thatcould send humans to Marsin just 39 days.

The Ad Astra Rocketcompany from Websterwill develop the Vasimr en-gine which uses plasma, anelectrically charged gas, asa propellant.

"This is like no otherrocket that you may haveseen in the past. It is a plas-ma rocket. The Vasimrrocket is not used forlaunching things. It is usedfor things already there,

which we call 'in space pro-pulsion,'" said the compa-ny's CEO, FranklinChang-Diaz, who is a for-mer astronaut and flew onseven space shuttlemissions.

The Vasimr engineworks by heating plasma toextreme temperatures us-

ing radio waves. Strongmagnetic fields then funnelthis plasma out of the backof the engine.

This in turn createsthrust, helping to propelthe engine at extremespeeds.

NASA willconsider em-ploying the propulsion sys-tem on future excursions toMars.

The company is alsothinking about other pro-jects for its Vasimr engine,such as asteroid retrieval,which would bring thespace rocks closer to Earth,allowing them to be mined.PTI

Trip to Mars in 39 days?Revolutionary engine, that could achieve this feat, to useplasma, an electrically charged gas, as propellant

● Interstellar:occurringbetween stars

● Ambient: immediatesurroundings ofsomething

● Epoch: Period/era

● Flux: instability

● Anatomy: Bodyframework

● Propel: drive orpush somethingforward

● Retrieval:Recovery

● Slosh: Spill

GLOSSARY

A Cockcroft-Walton generator