Laboratori Nazionali di Frascati

ISBN 978-88-86409-95-7 First digital edition: june 2016

Published byIstituto Nazionale di Fisica Nucleare

Laboratori Nazionali di FrascatiVia Enrico Fermi, 40 – 00044 Frascati (Rome) Italy

© 2008 Barbara Sciascia, text© 2008 Agostino Iacurci, illustrations© 2012 Giuseppina Novati, translation

Contributions to the text, Giovanni NucciCoordination and realization Plan.ed servizi editoriali

www.plan-ed.it

Printed in December 2014by Arti Grafiche La Moderna - Roma

For over ten years primary and juniorhigh schools have been visiting theFrascati National Laboratories (LNF) ofthe Italian National Institute of NuclearPhysics (INFN), welcomed by willingsearchers who accompany them toexplore the experimental areas.

From Here to the Big Bang arose from a lec-ture given on the platform in front of theKLOE experiment during the EuropeanResearchers’ Night, on September 28,2007.

The challenge was to write a book thatwould explain “hard science” to childrentrying to satisfy, at least in part, thecuriosity they express in a thousand ques-tions: “But how can scientists see whatyou can’t see?” or “how did scientists

dream up the idea of the Big Bang?”And again, “But what’s the point of allthis research?”

For the first time an English version ofFrom Here to the Big Bang is being print-ed. We hope to please both our youngerand older visitors to Frascati in the com-ing years with a memory of their visit toour laboratories, of their conversationwith the scientists, and, perhaps, as astarting point for further investigation.

Who knows? Someone might return in afew years time, having decided “tobecome a scientist”.

Umberto DosselliLNF Director

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Preface to the first English edition

– How was the universe born?– With the Big Bang,– What’s that?– Just what it sounds like. A big bang.

– So?– In the beginning, there was nothing. Then, there was a bang. And then, there waseverything.– And before the beginning?– I told you: nothing.– Are you sure?– Yes!– Really sure?– Yes ... Well no ... I’m not quite sure.– Ah!– But, I’m sure about the Big Bang.– Why?

– Everyone says.– Everyone who?– Scientists. – Cool! And who are the scientists?

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Who are these scientists? Good question! I have often tried to ask

children this question, and the answerswere usually that scientists are crazy,absent-minded, messy, very bad (or per-haps very good), and often dangerous.They also know everything, but do notthink about the consequences of what theydo; they want to destroy the world (or per-haps to save it). Then, I tried to ask thosechildren what sort of people they imag-ined scientists to be. And it turned outthat they imagined them as being male,and always wearing white coats. Then,there was usually a description of tinker-ing test tubes and glassware, of mixingcolored and perhaps smelly steaming liq-uids. Or they imagined them buildingcomplicated machinery, full of smalllights and switches—so complex that no-one even understands how it can holditself together without falling apart, muchless how it works. It often ends up blow-ing everything up, destroying machinery,glassware, and scientist.

But this is absolutely not true! Let’s start from the coat. In movies and

cartoons, scientists always wear a coat todistinguish themselves from the others, so

that we recognize them. But in reality,only some scientists, chemists or biolo-gists, for example, put on a white coat,and only when they have to do thingswhere they might get dirty. Then, theworld is also full of female scientists, whoare as brave as their male colleagues, if notbraver. Anyway, no scientist, man orwoman, with or without coat, would wantto blow up just for the sake of an experi-ment. Indeed, in general, scientists arevery careful to avoid this. And do youknow why? Because they are normal peo-ple. They have a mom and a dad, they areoften married and have children. They goto the grocery store, and also to the doc-tor’s, when they are sick. When they can,they go to the cinema, and also on vaca-tion to the beach or to the mountains.They sometimes build complicatedmachinery, this is true (things such as tel-escopes, or even worse, particle accelera-tors), but they have good knowledge of it.They know how it works and know everypiece of it. And they do all this onlybecause they want to understand howthings in the world work.

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– And how do scientists say how thingswork? – They have their own special way—thescientific method.– Scientific method? What’s that?– The first thing that scientists do is tolook around for something intriguing toexplain.– So, are they nosy?– More or less. Scientists are generallyvery curious, and ask themselves a lot ofquestions.– So, if you want to become a scientist,do you need to be curious?– Yes, but after asking yourself questions,you have to look for answers.– How?– You have to make assumptions, that is,you have to come up with ideas thatexplain things. All these new ideas, puttogether, are called a theory. You need tohave a lot of imagination to create newtheories, and you must also study verywell what other scientists have discov-ered before you.– And how can you be sure that your the-ory works?– You have to do appropriate experi-ments, then compare your theory with

the old ones, that is with all the experi-ments, observations and results that havebeen done before.– How?– With math.– What does math have to do with allthis?– For example, to check a theory thatdescribes how the planets move, youmust first measure where they are, anduse math. Then, you calculate where theyshould be according to your theory, andyou use math again. Finally, if your theo-ry works, your measurement results andyour calculations must agree. To showthat they agree, you use math again.– Then?– If it works, then you go and tell yourtheory to other scientists, so they cancheck what you’ve done and maybe findan even better theory.– What if the other scientists realize thatit doesn’t work? Or, if you do an experi-ment, and you notice something thatdoesn’t agree with your theory?– You have to change your theory or ana-lyze it carefully, until it explains whatyou saw in the experiment, or directly innature.

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For example, at school everyone studiesthe universal theory of gravitation, thesame one that implies that the Earth is aplanet revolving around the sun, or thatthe Moon revolves around the Earth. Or,that Jupiter revolves around the Sun andall the moons of Jupiter revolve aroundJupiter: a universe of turning planets.

Today, it all seems very simple, clear,and almost predictable, not least becausemen finally went to the Moon, and sawhow things worked from there. ButNewton, who was British and lived in1600, had no way of going to the Moonto see things. At best, the Moon could beseen from our Earth through a telescope.In his days, scientists used to say that thesun revolved around the Earth. Thatseemed to be a good theory. Too bad itdidn’t work very well. It got some thingswrong.

Newton thought of a theory thatwould work better: universal gravitation.But, first he had to make a series ofassumptions; then, he had to do someexperiments and do all the calculationsand see if his hypotheses were correct.

Now, he knew all about how objects,things like stones or pencils, work—

about how, for example, they end up onthe ground when they are dropped. Well,he came up with the hypothesis that theplanets were like stones, but a little big-ger, and that planets would work in thesame way as stones.

Imagine you are throwing a stone froma high place—for example, a mountain.The harder you throw it, the farther awaythe stone will fall. Newton could calcu-late these things very well. Then, hemade an assumption: he tried to imagineplanets as huge rocks that someone hadthrown with a lot of strength. This is notwhat really happened, of course, but thisidea allowed him to do his calculations,and also experiments, to test whether hisnew hypothesis worked. Indeed, he sawthat with his explanations the new theoryworked much better than the old one.

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Another example is when theChallenger exploded, right after liftoff.The story is a little sad, but it explains alot.

On January 28th, 1986, the shuttleChallenger exploded in the air a few sec-onds after launch, and all of thecrewmembers died. The U.S. govern-ment gathered a group of experts tostudy why the shuttle had exploded.Among the experts there was RichardFeynman, one of the greatest physicists ofthe twentieth century. Feynman foundhimself arguing with politicians, astro-nauts, lawyers, soldiers, engineers, andaviation experts. But, instead of spendingso much time arguing, at some point hedecided that the best thing to do was totalk to the engineers who had built theshuttle, to better understand how eachpiece of the spaceship operated.Eventually Feynman became convincedthat the cause of it all was a defective O-ring. An O-ring is a rubber ring, a gasketsimilar to the one inside a water faucet.The rubber was defective and, when theweather was too cold, it became hard andcould not hold a seal anymore, and so letout the very hot gas produced by the

combustion of the rocket fuel. A similarthing happens when the gasket in thewater fuacet gets too hard—the faucetbegins to leak. This fact was known formany years, but it was not consideredimportant. The day of the tragedy theweather was cold, so one of theChallenger’s O-rings became too hard.Hot gas came out from where it was notmeant to, piercing the hydrogen tank,and everything blew up.

Even though the rest of the committeedid not agree, Feynman wanted to showeveryone how the hardened O-ringscould break, because of the cold. So, dur-ing a meeting with journalists, he dippedone of these O-rings in a glass of icewater, right in front of everybody. The O-ring became brittle and broke. Nobodyat the meeting could believe that some-thing so small could have been over-looked, causing such a great disaster.Feynman used to say that, for a technolo-gy to be successful, “reality must takeprecedence over public relations, forNature cannot be fooled.”

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– To study Nature, scientists likeNewton, or like Feynman, use instru-ments. Sometimes, they even inventthem. In any case, they trust the instru-ments they use.– What do you mean by "trusting instru-ments"?– Take for example a pair of glasses. Weare so used to wearing them that we don’teven notice them. We no longer wonderif what we see through our glasses is trueor not. We use them, that’s all.– Are glasses instruments?– Of course. Your cell is an instrument,too. When we are on the phone, we donot wonder if we are really talking tomom or dad, or if a microscopic dwarflives in our cell, imitating their voices.– Then, our cell is an instrument too, andcan we trust it?– Both for glasses and mobile phones,there are scientists, usually engineers,who study and check to make sure thesetools work properly. For example, thatwhat you see through your glasses looksthe way it does in real life. The same istrue for your cell. As a result, we can useour glasses and mobile phones withoutthinking.

– All right, but what does this have to dowith scientists?– Scientists need increasingly sophisti-cated and complicated instruments tomeasure things in nature.– What things?– I don’t know: things like galaxies in theuniverse, or atoms, or even things thatare smaller than atoms.– And, do they measure them withinstruments? Like you measure tempera-ture with a thermometer?– Yes, only that much more complicatednumbers may come out.

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To understand how big the universe is,physicists have made some measurementsusing their instruments. The best meas-urement they that have managed toobtain is that the universe is a hundredmillion billion billion meters across.

That’s a very large number. It should bewritten with the digit 1 followed by 26zeroes. Just like a thousand is written with1 followed by three zeroes (1,000) and onemillion is written 1 followed by six zeroes(1,000,000). Only writing twenty-sixzeroes can become rather boring:

100000000000000000000000000.

So, mathematicians have invented atrick, a mathematical trick. Instead of 26zeroes after the 1, they write:

1026

(pronounced “ten to the twenty-sixth”).

That is, they write 10 and, above the10, in small digits, they put the numberof zeroes following the 1, in this case 26.It’s as if a baby koala were clinging to itsmother’s back. This way, you can writevery large numbers in a small space, andit is easier to do operations.

Now, the smallest distance that manhas ever measured is a tenth of a billionthof a billionth of a meter. This number iswritten with a 1 at the nineteenth placeafter the decimal point:

0.0000000000000000001

Here too, instead of writing all thosezeros, we write:

10-19

(pronounced “ten to the minus nineteenth”),

where the minus indicates that I haveto count the places after the decimalpoint, and 19 tells me in which place the1 goes, in this case the nineteenth.

Well, now that we know how to writevery large numbers and very small num-bers, we can also try to imagine them.

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Being able to imagine big or smallnumbers also tells us how much manunderstands about science.

Let’s start with the big ones: 1026. It’shard to imagine such a big number. Solet’s start by considering something thatis closer to us: a hundred meters. Weknow this number (we can also write102). If we take a one-meter ruler, wehave to move it a hundred times to coverone hundred meters. So far, it’s a piece ofcake. To cover a thousand meters (103),we need to repeat 10 times what we didto cover one hundred meters. And tocover ten thousand meters, (104 meters),we have to repeat ten times what we didto cover a thousand meters, and a hun-dred times what we did to cover one hun-dred meters. Now try to imagine a hun-dred million billion billion meters (1026):the distance across the universe.

To imagine small numbers is evenmore difficult than to imagine big ones.At first, it seems easy. A hundredth of ameter (10-2) is a centimeter, as everybodyknows. And you also know a thousandthof a meter (10-3): a millimeter.

Now, a cell in the human body is ahundredth of a millimeter across (10-5).

What happens if you take a ruler anddivide the smallest notch (one millime-ter) into one hundred parts? Althoughnot visible to the naked eye, an objectthis size can still be seen through an opti-cal microscope. One of those viruses thatgive you a common cold is a tenth of amillionth of a meter across (10-7), andyou can no longer see it even through anoptical microscope. But scientists haveinvented another instrument, the elec-tron microscope, to see things that are assmall as one billionth of a meter across(10-9 m). Whenever the instruments theyhave already invented are not enough tosatisfy their curiosity and understand theworld around them, scientists invent newones. To study things that are a tenth ofa billionth of a billionth of a meter in size(10-19 meters), physicists invented andbuilt very large instruments, sometimeseven larger than a football stadium, andcalled them particle accelerators.

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– Ok, but how does the Big Bang comeinto it?– It does, because now that we know howto write very large or very small num-bers, and we have more or less an idea ofhow large a large number is, and howsmall a small number is, we are able toknow what we are talking about.– The Big Bang?– Of course. The "Big Bang" is the besttheory scientists have come up with so farto answer the question "How was theuniverse born?" The theory says that theuniverse began 13 billion 800 millionyears ago (which we can also write 13.8 x109 years). It also says that, at that time,the universe was very small and very hot.– How small and how hot?– Smaller than anything we can measure,and hotter than anything we can thinkof, even the Sun.– Then?– With time, the universe became biggerand bigger and colder and colder.– And how big is it now?– As we said before, 1026 meters. Tomeasure how big the universe is today,we use increasingly powerful telescopes.– And can you measure how small the

universe was in the beginning, when itwas smaller than the smallest dot you canimagine? Smaller than 10-19 meters?– That’s something that physicistsaround the world are trying to deter-mine. They invented particle accelera-tors, because, at some point, it occurredto them that the universe could havebeen small before getting so big.

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OK, so now we’ve gotten to the idea that thesize of the universe is changing. This idea wasoriginally from Edwin Hubble, an Americanastronomer. When he was young he was unde-cided about whether he wanted to become alawyer or an astronomer, but luckily he choseastronomy. Between 1920 and 1930, he spentmany nights watching the sky through the tel-escope on Mount Wilson. Those nights turnedout to be very useful, because he discovered alot of things. The first one is that our galaxy isnot the only galaxy in the universe: manypoints of light that looked like stars to thenaked eye appeared as groups of billions of starsif seen through the telescope. They were so faraway that they looked like a single star. As hewas measuring the light coming from differentgalaxies, Hubble realized that it was a little dif-ferent from what was predicted by scientists’theories about stars. A few years before, scien-tist Henrietta Leavitt had discovered a methodto measure how far away stars are. The methodused a special type of star called “Cepheids.”Now, the galaxies that Hubble discovered alsohad Cepheid stars in them, so he was able tomeasure how far away they were. What he dis-covered was that the more distant they were,the more the light they gave out was differentfrom the kind of light scientists expected. The

only explanation he could think of to accountfor these differences was that all these galaxieswere moving away from us—and in fact, thateverything moves away from everything else.It’s not really easy to explain, but to under-stand better, you can do a little experimentwith a balloon. You have to inflate it a little,and draw dots on it with a marker. Say eachdot represents a galaxy. Then, if you inflatethe balloon even more, you can see that everydot has moved away from all the others. Forthe universe, it’s a little bit more complicat-ed, but the idea is the same.OK, then, if each galaxy is moving awayfrom the others, they all must have beencloser together a long time ago, as if theywere coming from the same point in space.The idea that the universe was born from asingle point was called the “Big Bang” byphysicist Fred Hoyle. In the beginning, itseemed like a strange idea, but other scien-tists made other measurements and becameconvinced that the Big Bang was the besttheory that could explain the universe.Hubble’s discovery is so important that hisname was given to a very powerful tele-scope mounted on a satellite, with whichsome of the most important studies of theBig Bang were made.

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– But if there was the Big Bang, it musthave left some traces.– Of course. After Hubble’s measurements,many people, like the Russian scientistGeorge Gamow and the American scientistRobert Dicke, thought that if the universewas indeed born with the Big Bang, weshould still be able to find traces of it.– Which traces?– It’s a bit as if you drop a stone into aquiet lake and the wave caused by thestone continues to be seen much later andmuch farther away. Maybe it will be verysmall, but we can still see it.– Can we see the waves in the sky?– Not with the naked eye: the leftovers ofthe Big Bang are radio waves. We needinstruments that are similar to a TV satel-lite dish, but larger and more complicated.The funny thing is that this signal, predict-ed by scientists, was discovered by chance.– By chance?– In 1963, the American telephone com-pany AT&T asked two of its scientists,Arno Penzias and Robert Wilson, tounderstand why its satellite dishes weremaking an annoying background noise ...crzzz ... like a untuned radio. The twobegan to check everything they could

think of, really everything. Whetherthere were radio stations nearby thatcould cause interference. Whether thenoise was changing with time. They evenended up climbing up the antennas toremove nests and pigeon droppings.– Pigeon droppings?– Yes, but it was useless. The noise con-tinued. They tried to point the antennain all different directions, but nothingchanged. The only explanation was thatthe noise was coming from far away. Veryfar away—from outside our galaxy. So,they went and talked to Dicke. Together,they made calculations and realized thatit was the signal that Gamow and Dickethought the Big Bang might have left.– Did they also calculate how long agothe Big Bang occurred?– More or less ... they were able to calculatethat that kind of noise would correspond toa Big Bang that happened between 10 and20 billion years ago. Later, they built betterinstruments and the best theory now saysthat the universe began 13.8 billion yearsago, from something small and hot. Verysmall and very hot.– How small? 10-7 like the cold virus?– No, much smaller!

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So, the early universe was very small, andwas made of very small particles. Too smallto be seen even with the most powerfulmicroscope. But in any case, most of theparticles that were part of the early universeno longer exist. To understand a little betterhow the universe worked when it was sosmall, scientists have built particle accelera-tors. Particle accelerators are very compli-cated machines. They were invented morethan eighty years ago, and today there areseveral types. Some are useful for veryimportant things, like treating some typesof cancer. Others, like the LHC acceleratorin Geneva or the Dafne accelerator inFrascati, allow scientists to study the tinyparticles themselves (the ones that can’t beseen) and to recreate the types of particlesthat were present at the beginning of theuniverse.

A “particle accelerator” accelerates par-ticles and then makes them collide withone another. When two particles collide,new particles are created, different fromthe ones involved in the collision. Theproduction of new particles is difficult toexplain; to really understand it you needto study hard and learn a lot of math. Butproducing these particles is a little bit

like going back in time: it’s possible toproduce particles that were around a longtime ago but which are not there any-more. Depending on how fast the parti-cles go inside the accelerator, we can pro-duce different types of new particles afterthe collision. For example, the acceleratorDafne can produce some kinds of parti-cles that were present when the universewas only 4 millionths of a second old (4x 10-6 seconds), at which time it wasalready a hundred thousand billionmeters across (1014 meters). But to get tothe very beginning of the universe, wemust go back even further. Up to now,with the help of LHC, scientists havebeen able to study the universe when itwas only a tenth of a billionth of a secondold (10-10 seconds), but they still haven’treached the very beginning. But the factis, by studying the particles produced ataccelerators, we can better understandthe Big Bang. Besides, it wouldn’t evenbe possible to recreate the whole BigBang in the laboratory. So, at each accel-erator, we try to reproduce a particularmoment of time after the Big Bang, sothat we can study the particular particlesthat were present at that time.

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– What I don’t understand is how youcan study particles that you can’t see.With a new instrument?– That’s right. That’s why scientistsinvented “particle detectors.” The namesays it all. They’re used to detect wherethe particles go.– Do they really work?– Of course! It’s just like what we saidabout eyeglasses and cell phones.Scientists have invented and refinedmore and more sophisticated particledetectors for over 100 years now. Thefirst ones were simple and small enoughto fit on a table. But as scientists want-ed to study smaller and smaller things,they built bigger and more complicateddetectors.– How big?– It depends. For example, KLOE, thedetector used to see the particles pro-duced by Dafne, is like a big tin canmade of iron and cables, 6 meters highand 6 meters long, weighing more than1,000 tons. That’s more or less as muchas 100 trucks. But in Switzerland, wehave another detector used to see the par-ticles produced by LHC: ATLAS, whichis 25 meters high and 46 meters long, as

big as an 8-floor building! It weighsmore than 7,000 tons.– Ok, but how do they work?– It’s like with aircraft. When a plane ishigh up in the sky, can you see it?– Yes, I guess. It depends. Typically, youonly see its trail. Sometimes, however,you only hear its noise.– Particle detectors work in the sameway. A particle cannot be seen, but if weget it to leave a trail—a track—we cansee if it moved, and what kind of particleit was. In the first detectors, the ones thatwere smaller than a box, you could seethe particle tracks with the naked eye.– What about the big ones, like KLOEand ATLAS?– KLOE and ATLAS are more complicat-ed, with a number of detectors inside oneanother, so that when the particle passesthrough, it leaves several tracks and canbe studied much better from variouspoints of view. In these large and com-plex detectors, the tracks are transformedinto electrical signals that you can studyon the computer.– So, is this how we found out how theuniverse started and how it is made?

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– Well, it’s not exactly everything.– Ah.– There are many questions scientistsjust cannot answer.– Which ones?– For example, what was there before theBig Bang.– Why?– Don’t you remember? Science starts fromobservation, followed by measurements.And there’s nothing from before the BigBang that we can observe or measure, and soscience can’t really tell us anything about it.– Ah, and do we know everything aboutthe universe after the Big Bang?

– No, no. Science has allowed us tounderstand many things in the worldaround us, but there are still many moreto understand and study. Apart from thequestion of when and where the universewas born, we have to study animal behav-ior, how stars work, how you can healfrom cancer and other diseases…– So, there’s still much more to be done?– Yes, there is.– And can I be a scientist too?– Of course! If you are curious and will-ing to study, why not?

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For the curious

For you: You can take a wonderful trip through large andsmall numbers in the film http://www.power-sof10.com/film, or in the book by Philip andPhylis Morrison (1982, revised 1994), Powers ofTen: A Book About the Relative Size of Things in theUniverse and the Effect of Adding another Zero.Scientific American Library. Richard Feynman tells many episodes that areboth amusing (he used to crack his colleagues’safes) and interesting (he participated in the build-ing of the first atomic bomb) in his book: Surely,You’re Joking, Mr. Feynman! by Ri chard P.Feynman, W. W. Norton & Company, 1997.At the web site:http://en.wikipedia.org/wiki/Space_Shuttle_program, you can find a lot of interestin infor-mation about the shuttle. You can also read:http://www.nasa.gov/.

For your parents or your teachers: The FirstThree Minutes: A Modern View of the Origin of theUniverse (1977) by Steven Weinberg, BantamBooks, presents a slightly dated but very clearintroduction to the basic ideas of the Big Bangtheory.

Acknowledgements

“I’m just a curious man,” Einstein used to say.It was actually thanks to the curiosity of themany children I got to meet during the morethan 10 years of my activity in science commu-nication that I found the drive to find the nec-essary time and energy to reconcile my researchwork with scientific popularization. I wouldlike to thank these children (and their teachers)who, with their so many questions (often con-fusing, sometimes difficult or just plain impos-sible) but also with their unexpected sugges-tions, have shown me one way to explain sci-ence without cheating, without saying it’s alleasy, or magic.

B.S.

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