Why our universe might exist on a knife-edge | Gian Giudice

Prevoditelj: Katarina Mikjel Recezent: Sanda L

So last year, on the Fourth of July,

Prošle godine na Dan nezavisnosti

experiments at the Large Hadron Collider

pokusima u Velikom hadronskom sudaraču (LHC)

discovered the Higgs boson.

otkriven je Higgsov bozon.

It was a historical day.

Bio je to povijesni dan.

There's no doubt that from now on,

Bez sumnje će se odsad

the Fourth of July will be remembered

četvrti srpnja pamtiti

not as the day of the Declaration of Independence,

ne kao dan Deklaracije o nezavisnosti,

but as the day of the discovery of the Higgs boson.

već kao dan kad je otkriven Higgsov bozon.

Well, at least, here at CERN.

Pa, barem ovdje u CERN-u.

But for me, the biggest surprise of that day

No, za mene je najveće iznenađenje toga dana

was that there was no big surprise.

bilo to da nije bilo velikog iznenađenja.

In the eye of a theoretical physicist,

U očima teorijskog fizičara,

the Higgs boson is a clever explanation

Higgsov bozon domišljato objašnjava

of how some elementary particles gain mass,

kako neke elementarne čestice dobivaju masu,

but it seems a fairly unsatisfactory

no ipak se čini kao prilično nezadovoljavajuće

and incomplete solution.

i nepotpuno rješenje.

Too many questions are left unanswered.

Previše je neodgovorenih pitanja.

The Higgs boson does not share the beauty,

Higgsov bozon nema ljepotu,

the symmetry, the elegance,

simetriju, eleganciju

of the rest of the elementary particle world.

ostalih elementarnih čestica.

For this reason, the majority of theoretical physicists

Zbog toga većina teorijskih fizičara

believe that the Higgs boson could not

smatra da Higgsov bozon

be the full story.

ne može biti cijela priča.

We were expecting new particles and new phenomena

Očekivali smo nove čestice i nove pojave

accompanying the Higgs boson.

uz Higgsov bozon.

Instead, so far, the measurements

Umjesto toga, zasad,

coming from the LHC show no signs of new particles

mjerenja iz LHC-a ne pokazuju postojanje novih čestica

or unexpected phenomena.

ni neočekivanih pojava.

Of course, the verdict is not definitive.

Naravno, taj zaključak nije konačan.

In 2015, the LHC will almost double

U 2015. LHC će gotovo udvostručiti

the energy of the colliding protons,

energiju protona koji se sudaraju

and these more powerful collisions

i ti će nam snažniji sudari

will allow us to explore further the particle world,

omogućiti daljnja istraživanja svijeta čestica

and we will certainly learn much more.

te ćemo sigurno saznati mnogo više.

But for the moment, since we have found

No zasad, budući da nismo pronašli

no evidence for new phenomena, let us suppose

nikakav dokaz novih pojava, pretpostavimo

that the particles that we know today,

da su danas poznate čestice,

including the Higgs boson,

uključujući Higgsov bozon,

are the only elementary particles in nature,

jedine elementarne čestice u prirodi,

even at energies much larger

čak i pri mnogo većim količinama energije

than what we have explored so far.

od onih koje smo dosad istraživali.

Let's see where this hypothesis is going to lead us.

Pogledajmo kamo će nas odvesti ta hipoteza.

We will find a surprising and intriguing result

Doći ćemo do iznenađujućeg i intrigantnog zaključka

about our universe, and to explain my point,

o našem svemiru. Ali kako bih to bolje objasnio,

let me first tell you what the Higgs is about,

prvo ću vam objasniti što je zapravo Higgs,

and to do so, we have to go back

a za to se moramo vratiti unatrag

to one tenth of a billionth of a second

do jedne desetine milijarditog dijela sekunde

after the Big Bang.

nakon Velikog praska.

And according to the Higgs theory,

Prema Higgsovoj teoriji,

at that instant, a dramatic event took place

u tom se trenutku dogodilo nešto dramatično

in the universe.

u svemiru.

Space-time underwent a phase transition.

Prostor-vrijeme pretrpjelo je fazni prijelaz.

It was something very similar to the phase transition

Bilo je to nešto vrlo slično faznom prijelazu

that occurs when water turns into ice

do kojega dolazi kad se voda pretvara u led

below zero degrees.

na temperaturi nižoj od nule.

But in our case, the phase transition

No, u našem slučaju, fazni prijelaz

is not a change in the way the molecules

nije promjena rasporeda molekula

are arranged inside the material,

unutar materijala,

but is about a change

već promjena

of the very fabric of space-time.

same strukture prostor-vrijeme.

During this phase transition, empty space

Tijekom tog faznog prijelaza, prazni prostor

became filled with a substance

ispunila je tvar

that we now call Higgs field.

koju danas nazivamo Higgsovim poljem.

And this substance may seem invisible to us,

Ta nam se tvar možda čini nevidljivom,

but it has a physical reality.

no dio je fizičke stvarnosti.

It surrounds us all the time,

Stalno nas okružuje,

just like the air we breathe in this room.

baš kao zrak koji dišemo u ovoj prostoriji.

And some elementary particles interact

Neke su elementarne čestice u interakciji

with this substance, gaining energy in the process.

s tom tvari, pri čemu dobivaju energiju.

And this intrinsic energy is what we call

Tu unutarnju energiju nazivamo

the mass of a particle,

masom čestice,

and by discovering the Higgs boson, the LHC

a otkrićem Higgsova bozona,

LHC je uvjerljivo dokazao postojanje spomenute tvari

has conclusively proved that this substance is real,

because it is the stuff the Higgs bosons are made of.

jer ona tvori Higgsov bozon.

And this, in a nutshell, is the essence of the Higgs story.

I to je, ukratko, suština priče o Higgsu.

But this story is far more interesting than that.

No, priča je mnogo zanimljivija od toga.

By studying the Higgs theory,

Proučavanjem Higgsove teorije

theoretical physicists discovered,

teorijski fizičari otkrili su,

not through an experiment

ne pokusom,

but with the power of mathematics,

već s pomoću matematike,

that the Higgs field does not necessarily exist

da Higgsovo polje ne postoji nužno

only in the form that we observe today.

samo u obliku u kojem ga danas promatramo.

Just like matter can exist as liquid or solid,

Baš kao što materija može postojati u tekućem ili čvrstom stanju,

so the Higgs field, the substance that fills all space-time,

tako bi i Higgsovo polje, tvar koja ispunjava prostor-vrijeme,

could exist in two states.

moglo postojati u dvama stanjima.

Besides the known Higgs state,

Uz već poznato Higgsovo stanje,

there could be a second state in which the Higgs field

moglo bi postojati i drugo stanje u kojemu je Higgsovo polje

is billions and billions times denser

milijarde i milijarde puta gušće

than what we observe today,

nego što trenutačna zapažanja pokazuju.

and the mere existence of another state

I samo postojanje drugog stanja

of the Higgs field poses a potential problem.

Higgsova polja potencijalni je problem.

This is because, according to the laws

To je zbog toga što su, prema zakonima

of quantum mechanics, it is possible

kvantne mehanike, mogući

to have transitions between two states,

prijelazi između dva stanja,

even in the presence of an energy barrier

čak i ako postoji energetska barijera

separating the two states,

koja razdvaja dva stanja,

and the phenomenon is called,

a ta se pojava naziva,

quite appropriately, quantum tunneling.

sasvim prikladno, kvantnim tuneliranjem.

Because of quantum tunneling,

Zahvaljujući kvantnom tuneliranju,

I could disappear from this room

mogao bih nestati iz ove prostorije

and reappear in the next room,

i pojaviti se u susjednoj prostoriji,

practically penetrating the wall.

praktički prolaskom kroza zid.

But don't expect me to actually perform the trick

No, ne očekujte da izvedem taj trik

in front of your eyes, because the probability

pred vama, jer je vjerojatnost

for me to penetrate the wall is ridiculously small.

da prođem kroza zid smiješno mala.

You would have to wait a really long time

Morali biste zaista dugo čekati

before it happens, but believe me,

da se to dogodi, ali vjerujte mi,

quantum tunneling is a real phenomenon,

kvantno tuneliranje stvarna je pojava

and it has been observed in many systems.

i zapažena je u mnogim sustavima.

For instance, the tunnel diode,

Primjerice, tunelska dioda,

a component used in electronics,

komponenta koja se koristi u elektronici,

works thanks to the wonders

radi zahvaljujući čudu

of quantum tunneling.

kvantnog tuneliranja.

But let's go back to the Higgs field.

No, vratimo se Higgsovu polju.

If the ultra-dense Higgs state existed,

Ako ultragusto Higgsovo stanje postoji,

then, because of quantum tunneling,

onda bi se, zbog kvantnog tuneliranja,

a bubble of this state could suddenly appear

mjehurić tog stanja mogao iznenada pojaviti

in a certain place of the universe at a certain time,

na određenom mjestu u svemiru u određeno vrijeme.

and it is analogous to what happens when you boil water.

Možemo to usporediti s onim što se događa kad prokuhavate vodu.

Bubbles of vapor form inside the water,

U vodi se stvaraju mjehurići pare,

then they expand, turning liquid into gas.

koji se potom šire, pretvarajući tekućinu u plin.

In the same way, a bubble of the ultra-dense Higgs state

Na isti bi se način mjehurić ultragustog Higgsova stanja

could come into existence because of quantum tunneling.

mogao stvoriti zbog kvantnog tuneliranja.

The bubble would then expand at the speed of light,

Mjehurić bi se zatim širio brzinom svjetlosti,

invading all space, and turning the Higgs field

zauzimajući čitav prostor i pretvarajući Higgsovo polje

from the familiar state into a new state.

iz poznatog stanja u novo stanje.

Is this a problem? Yes, it's a big a problem.

Je li to problem? Da, i to veliki.

We may not realize it in ordinary life,

Možda to ne primjećujemo u svakodnevnom životu,

but the intensity of the Higgs field is critical

ali jačina Higgsova polja ključna je

for the structure of matter.

za strukturu materije.

If the Higgs field were only a few times more intense,

Kad bi Higgsovo polje bilo samo nekoliko puta jače,

we would see atoms shrinking, neutrons decaying

atomi bi se smanjivali, neutroni propadali

inside atomic nuclei, nuclei disintegrating,

unutar atomskih jezgri, jezgre bi se raspadale,

and hydrogen would be

a vodik bi bio

the only possible chemical element in the universe.

jedini mogući kemijski element u svemiru.

And the Higgs field, in the ultra-dense Higgs state,

Higgsovo polje u ultragustom Higgsovu stanju

is not just a few times more intense than today,

nije samo nekoliko puta jače od trenutačnog,

but billions of times,

već čak milijarde puta

and if space-time were filled by this Higgs state,

i kad bi prostor-vrijeme bilo ispunjeno tim Higgsovim stanjem,

all atomic matter would collapse.

urušila bi se čitava atomska materija.

No molecular structures would be possible, no life.

Postojanje molekularnih struktura, kao i života, bilo bi nemoguće.

So, I wonder, is it possible

Stoga se pitam je li moguće

that in the future, the Higgs field

da će u budućnosti Higgsovo polje

will undergo a phase transition and,

doživjeti fazni prijelaz

through quantum tunneling, will be transformed

i kvantnim tuneliranjem preobraziti se

into this nasty, ultra-dense state?

u to gadno, ultragusto stanje.

In other words, I ask myself, what is the fate

Drugim riječima, pitam se koja je sudbina

of the Higgs field in our universe?

Higgsova polja u našem svemiru.

And the crucial ingredient necessary

A presudni element

neophodan za odgovor na to pitanje jest masa Higgsova bozona.

to answer this question is the Higgs boson mass.

And experiments at the LHC found that the mass

Pokusi u LHC-u otkrili su da masa

of the Higgs boson is about 126 GeV.

Higgsova bozona iznosi oko 126 GeV.

This is tiny when expressed in familiar units,

Ona je sićušna izrazimo li je u poznatim jedinicama

because it's equal to something like

jer iznosi otprilike

10 to the minus 22 grams,

10 na -22 grama,

but it is large in particle physics units,

ali je velika u jedinicama fizike čestica

because it is equal to the weight

jer je jednaka težini

of an entire molecule

čitave molekule

of a DNA constituent.

baze DNK.

So armed with this information from the LHC,

Naoružani tim informacijama iz LHC-a,

together with some colleagues here at CERN,

zajedno s još nekim kolegama ovdje u CERN-u,

we computed the probability

izračunali smo vjerojatnost

that our universe could quantum tunnel

prelaska našeg svemira kvantnim tuneliranjem

into the ultra-dense Higgs state,

u ultragusto Higgsovo stanje

and we found a very intriguing result.

i dobili vrlo zanimljiv rezultat.

Our calculations showed

Naši su izračuni pokazali

that the measured value of the Higgs boson mass

da je izmjerena vrijednost mase Higgsova bozona

is very special.

vrlo posebna.

It has just the right value

Ona je upravo tolika

to keep the universe hanging

da održava svemir

in an unstable situation.

u nestabilnom stanju.

The Higgs field is in a wobbly configuration

Higgsovo polje ima klimavu konfiguraciju

that has lasted so far

koja je izdržala dosad,

but that will eventually collapse.

ali će se s vremenom urušiti.

So according to these calculations,

Prema tim izračunima

we are like campers

mi smo kao kampisti

who accidentally set their tent

koji su slučajno postavili svoj šator

at the edge of a cliff.

na rub litice.

And eventually, the Higgs field

Naposljetku će Higgsovo polje

will undergo a phase transition

doživjeti fazni prijelaz

and matter will collapse into itself.

i materija će se urušiti sama u sebe.

So is this how humanity is going to disappear?

I zar će čovječanstvo tako nestati?

I don't think so.

Ne bih rekao.

Our calculation shows that quantum tunneling

Naš izračun pokazuje da kvantno tuneliranje

of the Higgs field is not likely to occur

Higgsova polja nije vjerojatno

in the next 10 to the 100 years,

u sljedećih 10 na 100 godina,

and this is a very long time.

a to je vrlo dugo razdoblje.

It's even longer than

Čak i duže nego što je

the time it takes for Italy to form a stable government.

Italiji potrebno da formira stabilnu vladu.

(Laughter)

(Smijeh)

Even so, we will be long gone by then.

Bez obzira, dotad nas već odavno neće biti.

In about five billion years,

Za oko 5 milijardi godina

our sun will become a red giant,

naše će Sunce postati crveni div

as large as the Earth's orbit,

veličine Zemljine orbite

and our Earth will be kaput,

i to će biti kraj naše Zemlje,

and in a thousand billion years,

a za tisuću milijardi godina,

if dark energy keeps on fueling

ako tamna energija nastavi ubrzavati

space expansion at the present rate,

širenje svemira trenutačnim tempom,

you will not even be able to see as far as your toes,

nećete biti u stanju vidjeti dalje od svojih nogu

because everything around you

jer će se sve oko vas

expands at a rate faster than the speed of light.

širiti tempom bržim od brzine svjetlosti.

So it is really unlikely

Tako da stvarno nije vjerojatno

that we will be around to see the Higgs field collapse.

da će nas još uvijek biti da svjedočimo urušavanju Higgsova polja.

But the reason why I am interested

No, razlog zbog kojeg mene zanima

in the transition of the Higgs field

prijelaz Higgsova polja

is because I want to address the question,

jest taj što želim odgovoriti na pitanje

why is the Higgs boson mass so special?

zašto je masa Higgsova bozona tako posebna.

Why is it just right to keep the universe

Zašto je upravo tolika da održava svemir

at the edge of a phase transition?

na rubu faznog prijelaza?

Theoretical physicists always ask "why" questions.

Teorijski fizičari uvijek pitaju „zašto”.

More than how a phenomenon works,

Više nego kako dolazi do neke pojave,

theoretical physicists are always interested in

teorijske fizičare zanima

why a phenomenon works in the way it works.

zašto se ona odvija onako kako se odvija.

We think that this these "why" questions

Smatramo da nam pitanja „zašto”

can give us clues

mogu dati indicije

about the fundamental principles of nature.

o osnovnim načelima prirode.

And indeed, a possible answer to my question

I zaista, mogući odgovor na moje pitanje

opens up new universes, literally.

doslovno otvara nove svemire.

It has been speculated that our universe

Nagađa se da je naš svemir

is only a bubble in a soapy multiverse

samo mjehurić u sapuničastom multisvemiru

made out of a multitude of bubbles,

koji tvori mnoštvo mjehurića,

and each bubble is a different universe

a svaki je od njih zaseban svemir

with different fundamental constants

s različitim osnovnim konstantama

and different physical laws.

i različitim zakonima fizike.

And in this context, you can only talk about

U tom kontekstu možemo razgovarati

the probability of finding a certain value of the Higgs mass.

tek o vjerojatnosti pronalaska određene vrijednosti Higgsove mase.

Then the key to the mystery

U tom se slučaju ključ za rješavanje misterija

could lie in the statistical properties

možda nalazi u statističkim svojstvima

of the multiverse.

multisvemira.

It would be something like what happens

Možemo to usporediti

with sand dunes on a beach.

s pješčanim dinama na plaži.

In principle, you could imagine to find sand dunes

U načelu, pješčane dine na plaži

of any slope angle in a beach,

mogle bi biti bilo kojeg kuta nagiba,

and yet, the slope angles of sand dunes

pa ipak, kutovi nagiba pješčanih dina

are typically around 30, 35 degrees.

obično iznose oko 30-35 stupnjeva.

And the reason is simple:

A razlog je jednostavan:

because wind builds up the sand, gravity makes it fall.

vjetar nanosi pijesak, koji zbog gravitacije pada.

As a result, the vast majority of sand dunes

Posljedica toga je da velika većina pješčanih dina

have slope angles around the critical value,

ima kut nagiba blizu kritične vrijednosti,

near to collapse.

na granici rušenja.

And something similar could happen

Nešto slično moglo bi se dogoditi

for the Higgs boson mass in the multiverse.

masi Higgsova bozona u multisvemiru.

In the majority of bubble universes,

U većini mjehurića svemira

the Higgs mass could be around the critical value,

Higgsova bi masa mogla biti oko kritične vrijednosti,

near to a cosmic collapse of the Higgs field,

blizu kozmičkog kolapsa Higgsova polja

because of two competing effects,

zbog dva međusobno suprotstavljena efekta,

just as in the case of sand.

baš kao u primjeru s pijeskom.

My story does not have an end,

Moja priča nema kraj

because we still don't know the end of the story.

jer još uvijek ne znamo kako će sve završiti.

This is science in progress,

Istraživanja su u tijeku,

and to solve the mystery, we need more data,

a za rješavanje tog misterija, potrebno je još podataka

and hopefully, the LHC will soon add new clues

i LHC će, nadajmo se, uskoro otkriti nove detalje

to this story.

te priče.

Just one number, the Higgs boson mass,

Samo jedan broj, masa Higgsova bozona,

and yet, out of this number we learn so much.

a možemo toliko toga saznati iz njega.

I started from a hypothesis, that the known particles

Započeo sam hipotezom da su dosad poznate čestice

are all there is in the universe,

sve što se nalazi u svemiru,

even beyond the domain explored so far.

čak i izvan dosad istraženog područja.

From this, we discovered that the Higgs field

Iz toga smo otkrili da Higgsovo polje,

that permeates space-time may be standing

koje prožima prostor-vrijeme,

možda visi o niti, spremno za kozmički kolaps

on a knife edge, ready for cosmic collapse,

and we discovered that this may be a hint

i otkrili smo da bi to mogla biti naznaka

that our universe is only a grain of sand

da je naš svemir samo zrnce pijeska

in a giant beach, the multiverse.

na golemoj plaži – multisvemiru.

But I don't know if my hypothesis is right.

No, ne znam je li moja hipoteza točna.

That's how physics works: A single measurement

Tako je to s fizikom: jedno mjerenje

can put us on the road to a new understanding

može nas odvesti do novog shvaćanja

of the universe

svemira

or it can send us down a blind alley.

ili nas može dovesti u slijepu ulicu.

But whichever it turns out to be,

No, kako god bilo,

there is one thing I'm sure of:

u jedno sam siguran:

The journey will be full of surprises.

putovanje će biti puno iznenađenja.

Thank you.

Hvala vam!

(Applause)

(Pljesak)