TED2005
Brian Greene: Making sense of string theory
Brian Greene om strengteori
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Fysiker Brian Greene forklarer superstrengteori, idéen at meget små energistrenge, der vibrerer i 11 dimensioner, skaber samtlige partikler og kræfter i universet.
Brian Greene - Physicist
Brian Greene is perhaps the best-known proponent of superstring theory, the idea that minuscule strands of energy vibrating in a higher dimensional space-time create every particle and force in the universe. Full bio
Brian Greene is perhaps the best-known proponent of superstring theory, the idea that minuscule strands of energy vibrating in a higher dimensional space-time create every particle and force in the universe. Full bio
Double-click the English transcript below to play the video.
00:13
In the year 1919,
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I året 1919
00:15
a virtually unknown German mathematician, named Theodor Kaluza
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kom en så godt som ukendt tysk matematiker ved navn Theodor Kaluza
00:22
suggested a very bold and, in some ways, a very bizarre idea.
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med en meget dristig og på nogle måder en meget bizar idé.
00:29
He proposed that our universe
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Han foreslog, at vores univers
00:31
might actually have more than the three dimensions
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måske egentlig har flere end de tre dimensioner,
00:34
that we are all aware of.
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som vi alle kender til.
00:37
That is in addition to left, right, back, forth and up, down,
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Det vil sige ud over venstre, højre, frem, tilbage og op, ned,
00:40
Kaluza proposed that there might be additional dimensions of space
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Kaluza foreslog, at der kunne være yderligere rumdimensioner,
00:45
that for some reason we don't yet see.
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som vi af en eller anden årsag ikke ser endnu.
00:48
Now, when someone makes a bold and bizarre idea,
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Nå, når nogen kommer med en dristig og bizar idé,
00:52
sometimes that's all it is -- bold and bizarre,
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er det nogle gange alt, den er -- dristig og bizar,
00:54
but it has nothing to do with the world around us.
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men den har intet at gøre med verden omkring os.
00:57
This particular idea, however --
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Lige præcis denne idé --
00:59
although we don't yet know whether it's right or wrong,
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selvom vi endnu ikke ved, om den er rigtig eller forkert,
01:02
and at the end I'll discuss experiments which, in the next few years,
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og til slut vil jeg diskutere eksperimenter, der i de næste par år
01:05
may tell us whether it's right or wrong --
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måske vil sige os, om den er rigtig eller forkert --
01:07
this idea has had a major impact on physics in the last century
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har denne idé haft en stor indflydelse på fysik i det sidste århundrede
01:11
and continues to inform a lot of cutting-edge research.
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og fortsætter med at præge en masse banebrydende forskning.
01:14
So, I'd like to tell you something about the story of these extra dimensions.
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Så jeg vil fortælle jer noget om disse ekstra dimensioners historie.
01:18
So where do we go?
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Så hvor starter vi?
01:20
To begin we need a little bit of back story. Go to 1907.
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Til at begynde med har vi brug for lidt baggrundshistorie. Tag til 1907.
01:23
This is a year when Einstein is basking in the glow
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Dette er et år, hvor Einstein soler sig i
01:27
of having discovered the special theory of relativity
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at have opdaget den specielle relativitetsteori
01:30
and decides to take on a new project,
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og beslutter sig for at gå i gang med et nyt projekt
01:33
to try to understand fully the grand, pervasive force of gravity.
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for til fulde at prøve at forstå tyngdekraftens prægtige, gennemtrængende kraft.
01:40
And in that moment, there are many people around
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Og i det øjeblik er der mange folk,
01:43
who thought that that project had already been resolved.
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der troede, at det projekt allerede var blevet løst.
01:47
Newton had given the world a theory of gravity in the late 1600s
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Newton havde givet verden en gravitationsteori i slutningen af 1600'erne,
01:50
that works well, describes the motion of planets,
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der virker godt, beskriver planeternes bevægelse,
01:54
the motion of the moon and so forth,
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månens bevægelse og så videre,
01:56
the motion of apocryphal of apples falling from trees,
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bevægelsen af opdigtede æbler, der falder fra træer
01:59
hitting people on the head.
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og rammer folk i hovedet.
02:01
All of that could be described using Newton's work.
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Alt det kunne beskrives ved at benytte Newtons arbejde.
02:03
But Einstein realized that Newton had left something out of the story,
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Men Einstein indså, at Newton havde udeladt noget fra historien,
02:07
because even Newton had written
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for selv Newton havde skrevet,
02:10
that although he understood how to calculate the effect of gravity,
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at selvom han forstod, hvordan man udregnede tyngdekraftens effekt,
02:15
he'd been unable to figure out how it really works.
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havde han været ude af stand til at finde ud af, hvordan den virkelig virker.
02:18
How is it that the Sun, 93 million miles away,
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Hvordan er det, at Solen, 150 millioner km væk,
02:21
[that] somehow it affects the motion of the Earth?
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[at] den på en eller anden måde påvirker Jordens bevægelse?
02:24
How does the Sun reach out across empty inert space and exert influence?
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Hvordan rækker Solen ud over tomt, ubevægeligt rum og udøver påvirkning?
02:28
And that is a task to which Einstein set himself --
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Og det er en opgave, til hvilken Einstein dedikerede sig selv --
02:31
to figure out how gravity works.
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at finde ud af, hvordan tyngdekraften virker.
02:34
And let me show you what it is that he found.
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Og lad mig vise jer, hvad det er, han fandt.
02:37
So Einstein found
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Så Einstein fandt ud af,
02:38
that the medium that transmits gravity is space itself.
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at mediet, som tyngdekraften virker gennem, er rummet selv.
02:42
The idea goes like this:
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Idéen går som følger:
02:44
imagine space is a substrate of all there is.
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forestil jer rummer er et substrat af alt, der er.
02:46
Einstein said space is nice and flat, if there's no matter present.
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Einstein sagde, rummet er dejligt fladt, hvis der ikke er noget stof til stede.
02:50
But if there is matter in the environment, such as the Sun,
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Men hvis der er stof i nærheden, som Solen,
02:54
it causes the fabric of space to warp, to curve.
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får det rummets struktur til at forvrides, til at kurve.
02:58
And that communicates the force of gravity.
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Og det kommunikerer tyngdekraftens kraft.
03:00
Even the Earth warps space around it.
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Selv Jorden forvrider rummet omkring sig.
03:03
Now look at the Moon.
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Se nu på Månen.
03:05
The Moon is kept in orbit, according to these ideas,
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Månen bliver holdt i kredsløb ifølge idéerne,
03:08
because it rolls along a valley in the curved environment
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fordi den ruller langs en dal i det kurvede miljø,
03:11
that the Sun and the Moon and the Earth can all create by virtue of their presence.
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som Solen og Månen og Jorden alle kan skabe i kraft af deres tilstedeværelse.
03:16
We go to a full-frame view of this.
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Vi går til et helbillede af dette.
03:19
The Earth itself is kept in orbit
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Jorden selv bliver holdt i kredsløb,
03:21
because it rolls along a valley in the environment that's curved
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fordi den ruller langs en dal i miljøet, der er kurvet
03:25
because of the Sun's presence.
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på grund af Solens tilstedeværelse.
03:27
That is this new idea about how gravity actually works.
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Dette er denne nye idé om, hvordan tyngdekraften egentlig virker.
03:32
Now, this idea was tested in 1919 through astronomical observations.
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Nå, denne idé blev testet i 1919 gennem astronomiske observationer.
03:37
It really works. It describes the data.
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Den virker virkelig. Den beskriver dataene.
03:40
And this gained Einstein prominence around the world.
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Og dette vandt Einstein berømmelse verden over.
03:44
And that is what got Kaluza thinking.
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Og det er det, der fik Kaluza til at tænke.
03:48
He, like Einstein, was in search of what we call a unified theory.
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Han, som Einstein, ledte efter det, vi kalder en forenet teori.
03:52
That's one theory
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Det er én teori,
03:54
that might be able to describe all of nature's forces from one set of ideas,
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der kunne være i stand til at beskrive alle naturens kræfter ud fra ét sæt idéer,
03:58
one set of principles, one master equation, if you will.
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ét sæt principper, én mesterligning, om man vil.
04:02
So Kaluza said to himself,
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Så Kaluza sagde til sig selv,
04:04
Einstein has been able to describe gravity
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Einstein har været i stand til at beskrive tyngdekraften
04:07
in terms of warps and curves in space --
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ud fra forvridninger og kurver i rummet --
04:09
in fact, space and time, to be more precise.
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egentlig rum og tid for at være mere præcis.
04:12
Maybe I can play the same game with the other known force,
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Måske kan jeg spille det samme spil med den anden kendte kraft,
04:17
which was, at that time, known as the electromagnetic force --
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som på det tidspunkt var kendt som den elektromagnetiske kraft --
04:20
we know of others today, but at that time
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vi kender til andre i dag, men på den tid
04:22
that was the only other one people were thinking about.
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var den den eneste anden folk tænkte på.
04:24
You know, the force responsible for electricity
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I ved, kraften, der er skyld i elektricitet
04:26
and magnetic attraction and so forth.
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og magnetisk tiltrækning og så videre.
04:28
So Kaluza says, maybe I can play the same game
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Så Kaluza siger, måske kan jeg spille det samme spil
04:31
and describe electromagnetic force in terms of warps and curves.
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og beskrive elektromagnetisk kraft ud fra forvridninger og kurver.
04:35
That raised a question: warps and curves in what?
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Det rejste et spørgsmål: forvridninger og kurver i hvad?
04:38
Einstein had already used up space and time,
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Einstein havde allerede opbrugt rum og tid,
04:43
warps and curves, to describe gravity.
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forvridninger og kurver, til at beskrive tyngdekraft.
04:45
There didn't seem to be anything else to warp or curve.
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Der lod ikke til at være noget andet at forvride og kurve.
04:48
So Kaluza said, well, maybe there are more dimensions of space.
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Så Kaluza sagde, nå, måske er der flere dimensioner af rum.
04:53
He said, if I want to describe one more force,
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Han sagde, hvis jeg vil beskrive en kraft mere,
04:55
maybe I need one more dimension.
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behøver jeg måske en dimension mere.
04:57
So he imagined that the world had four dimensions of space, not three,
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Så han forestille sig, at verden havde fire rumdimensioner, ikke tre,
05:01
and imagined that electromagnetism was warps and curves
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og forestillede sig, at elektromagnetisme var forvridninger og kurver
05:05
in that fourth dimension. Now here's the thing:
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i denne fjerde dimension. Nå her er det smarte:
05:07
when he wrote down the equations describing warps and curves
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da han nedskrev ligningerne, der beskrev forvridninger og kurver
05:10
in a universe with four space dimensions, not three,
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i et univers med fire rumdimensioner, ikke tre,
05:13
he found the old equations that Einstein had already derived in three dimensions --
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fandt han de gamle ligninger, som Einstein allerede havde udledt i tre dimensioner --
05:17
those were for gravity --
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de var om tyngdekraften --
05:18
but he found one more equation because of the one more dimension.
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men han fandt en ligning mere på grund af den ekstra dimension.
05:22
And when he looked at that equation,
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Og da han så på den ligning,
05:24
it was none other than the equation
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var det ingen anden end ligningen,
05:26
that scientists had long known to describe the electromagnetic force.
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som videnskabsmænd længe havde vidst beskrev den elektromagnetiske kraft.
05:29
Amazing -- it just popped out.
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Fantastisk -- den sprang bare frem.
05:31
He was so excited by this realization
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Han blev så ophidset af denne erkendelse,
05:34
that he ran around his house screaming, "Victory!" --
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at han løb rundt i huset og skreg, "Sejr!" --
05:37
that he had found the unified theory.
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at han havde fundet den forenede teori.
05:40
Now clearly, Kaluza was a man who took theory very seriously.
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Nu var Kaluza tydeligvis en mand, der tog teori meget alvorligt.
05:47
He, in fact --
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Faktisk så --
05:48
there is a story that when he wanted to learn how to swim,
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der er en historie, at da han ville lære at svømme,
05:51
he read a book, a treatise on swimming --
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læste han en bog, en afhandling om svømning --
05:54
(Laughter)
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(Latter)
05:55
-- then dove into the ocean.
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-- så dykkede han i havet.
05:57
This is a man who would risk his life on theory.
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Dette er en mand, der ville risikere sit liv på teori.
06:00
Now, but for those of us who are a little bit more practically minded,
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Nå, men for dem af os, der er et lidt mere praktisk sindelag,
06:04
two questions immediately arise from his observation.
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rejser to spørgsmål sig straks fra hans observation.
06:07
Number one: if there are more dimensions in space, where are they?
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Nummer et: hvis der er flere dimensioner i rummet, hvor er de?
06:11
We don't seem to see them.
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Vi ser dem ikke.
06:13
And number two: does this theory really work in detail,
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Og nummer to: virker denne teori virkelig i detaljerne,
06:17
when you try to apply it to the world around us?
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når man prøver at bruge den på verden omkring os?
06:20
Now, the first question was answered in 1926
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Nå, det første spørgsmål blev besvaret i 1926
06:24
by a fellow named Oskar Klein.
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af en fyr ved navn Oskar Klein.
06:26
He suggested that dimensions might come in two varieties --
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Han foreslog, at dimensioner måske findes i to variationer --
06:30
there might be big, easy-to-see dimensions,
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der kunne være store, lette-at-se dimensioner,
06:33
but there might also be tiny, curled-up dimensions,
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men der kunne også være små, sammenrullede dimensioner.
06:36
curled up so small, even though they're all around us,
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rullet så småt sammen, at selvom de er overalt omkring os,
06:39
that we don't see them.
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ser vi dem ikke.
06:41
Let me show you that one visually.
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Lad mig vise jer den billedligt.
06:43
So, imagine you're looking at something
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Så, forestil jer, I ser på noget,
06:45
like a cable supporting a traffic light.
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som et kabel, der holder et trafiklys.
06:47
It's in Manhattan. You're in Central Park -- it's kind of irrelevant --
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Det er i Manhattan. I er i Central Park -- det er ret irrelevant --
06:50
but the cable looks one-dimensional from a distant viewpoint,
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men kablet ser en-dimensionelt ud fra et fjernt synspunkt,
06:54
but you and I all know that it does have some thickness.
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men vi ved alle, at det har nogen tykkelse.
06:57
It's very hard to see it, though, from far away.
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Det er dog meget svært at se det langt fra.
06:59
But if we zoom in and take the perspective of, say,
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Men hvis vi zoomer ind og indtager perspektivet at, lad os sige,
07:01
a little ant walking around --
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en lille myre, der går rundt --
07:03
little ants are so small that they can access all of the dimensions --
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små myrer er så små, at de har adgang til alle dimensionerne --
07:06
the long dimension,
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den lange dimension,
07:08
but also this clockwise, counter-clockwise direction.
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men også denne retning med og mod uret.
07:11
And I hope you appreciate this.
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Og jeg håber, I værdsætter dette.
07:13
It took so long to get these ants to do this.
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Det tog så lang tid at få disse myrer til at gøre dette.
07:15
(Laughter)
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(Latter)
07:16
But this illustrates the fact that dimensions can be of two sorts:
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Men dette illustrerer, at dimensionerne kan være at to slags:
07:19
big and small. And the idea that maybe the big dimensions around us
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store og små. Og den idé, at måske er de store dimensioner omkring os
07:23
are the ones that we can easily see,
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dem, som vi let ser,
07:25
but there might be additional dimensions curled up,
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men der kunne være yderligere dimensioner krøllet sammen,
07:28
sort of like the circular part of that cable,
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lidt som den runde del af det kabel,
07:30
so small that they have so far remained invisible.
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så småt, at de indtil videre er forblevet usynlige.
07:34
Let me show you what that would look like.
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Lad mig vise jer, hvordan det ville se ud.
07:36
So, if we take a look, say, at space itself --
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Så, hvis vi tager et kig, lad os sige, på rummet selv --
07:39
I can only show, of course, two dimensions on a screen.
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jeg kan selvfølgelig kun vise jer to dimensioner på en skærm.
07:43
Some of you guys will fix that one day,
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Nogle af jer vil klare den en skønne dag,
07:45
but anything that's not flat on a screen is a new dimension,
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men alt det, der ikke er fladt på en skærm, er en ny dimenison,
07:47
goes smaller, smaller, smaller,
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bliver mindre, mindre, mindre,
07:49
and way down in the microscopic depths of space itself,
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og dybt nede i de mikroskopiske dybder af rummet selv,
07:53
this is the idea,
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er det idéen,
07:54
you could have additional curled up dimensions --
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man kunne have yderligere sammenkrøllede dimensioner --
07:56
here is a little shape of a circle -- so small that we don't see them.
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her er en lille form af en cirkel -- så lille, at vi ikke ser dem.
07:59
But if you were a little ultra microscopic ant walking around,
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Men hvis man var en lille ultramikroskopisk myre, der gik rundt,
08:03
you could walk in the big dimensions that we all know about --
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kunne man gå i de store dimensioner, som vi alle kender til --
08:05
that's like the grid part --
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det er gitter-delen --
08:07
but you could also access the tiny curled-up dimension
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men man kunne også komme ind i den lille sammenkrøllede dimension,
08:10
that's so small that we can't see it with the naked eye
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der er så lille, at vi ikke kan se den med det blotte øje
08:12
or even with any of our most refined equipment.
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eller endda men noget af vores fineste udstyr.
08:15
But deeply tucked into the fabric of space itself,
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Men dybt stukket ind i rummets indre struktur,
08:18
the idea is there could be more dimensions, as we see there.
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er idéen, der kunne være flere dimensioner, som vi ser der.
08:22
Now that's an explanation
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Nå, det er en forklaring
08:26
about how the universe could have more dimensions than the ones that we see.
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på, hvordan universet kunne have flere dimensioner end dem, som vi ser.
08:30
But what about the second question that I asked:
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Men hvad men det andet spørgsmål, som jeg stillede:
08:33
does the theory actually work
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virker teorien egentlig,
08:35
when you try to apply it to the real world?
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når man forsøger at bruge den på den virkelige verden?
08:37
Well, it turns out that Einstein and Kaluza and many others
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Altså, det viser sig, at Einstein og Kaluza og mange andre
08:40
worked on trying to refine this framework
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arbejdede på at prøve at forfine denne ramme
08:45
and apply it to the physics of the universe
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og bruge den på det af universets fysik,
08:48
as was understood at the time, and, in detail, it didn't work.
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som man forstod på den tid, og i detaljer virkede den ikke.
08:52
In detail, for instance,
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I detaljer, for eksempel
08:53
they couldn't get the mass of the electron
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kunne de ikke få elektronens masse
08:55
to work out correctly in this theory.
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til at hænge rigtigt sammen i denne teori.
08:57
So many people worked on it, but by the '40s, certainly by the '50s,
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Så mange arbejdede på den, men i 40'erne, helt sikkert i 50'erne,
09:02
this strange but very compelling idea
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var denne underlige, men meget overbevisende, idé,
09:06
of how to unify the laws of physics had gone away.
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om hvordan man kunne samle fysikkens love forsvundet.
09:09
Until something wonderful happened in our age.
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Indtil noget fantastisk skete i vores tidsalder.
09:13
In our era, a new approach to unify the laws of physics
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I vores æra bliver en ny tilgang til at forene fysikkens love
09:17
is being pursued by physicists such as myself,
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fulgt af fysikere som jeg selv,
09:19
many others around the world,
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mange andre verden over,
09:21
it's called superstring theory, as you were indicating.
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den hedder superstrengteori, som I indikerede.
09:24
And the wonderful thing is that superstring theory
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Og den fantastiske ting er, at superstrengteori
09:28
has nothing to do at first sight with this idea of extra dimensions,
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intet har at gøre med ved første øjekast med denne idé om ekstra dimensioner,
09:32
but when we study superstring theory,
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men når man studerer superstrengteori,
09:35
we find that it resurrects the idea in a sparkling, new form.
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opdager man, at den genopliver idéen i en glitrende, ny form.
09:38
So, let me just tell you how that goes.
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Så, lad mig lige fortælle jer, hvordan det går an.
09:40
Superstring theory -- what is it?
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Superstrengteori -- hvad er det?
09:42
Well, it's a theory that tries to answer the question:
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Altså, det er en teori, der forsøger at besvare spørgsmålet:
09:44
what are the basic, fundamental, indivisible, uncuttable constituents
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hvad er de basale, fundamentale, udelelige, uskærlige bestanddele,
09:49
making up everything in the world around us?
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som alt i verden omkring os består af?
09:53
The idea is like this.
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Idéen er som følger.
09:55
So, imagine we look at a familiar object, just a candle in a holder,
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Så, forestil jer, vi ser på et kendt objekt, bare et lys i en stage,
10:00
and imagine that we want to figure out what it is made of.
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og forestil jer, at vi vil finde ud af, hvad det er lavet af.
10:03
So we go on a journey deep inside the object and examine the constituents.
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Så vi tager på en rejse dybt ind i objektet og undersøger bestanddelene.
10:07
So deep inside -- we all know, you go sufficiently far down, you have atoms.
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Så dybt inde -- vi ved alle, går man langt nok ned, har man atomer.
10:11
We also all know that atoms are not the end of the story.
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Vi ved også, at atomer ikke er enden på historien.
10:14
They have little electrons that swarm around a central nucleus
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De har små elektroner, der sværmer omkring en kerne i midten
10:18
with neutrons and protons.
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med neutroner og protoner.
10:19
Even the neutrons and protons have smaller particles inside of them known as quarks.
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Selv neutroner og protoner har mindre partikler inden i dem kendt som kvarker.
10:24
That is where conventional ideas stop.
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Det er her, koncentionelle idéer stopper.
10:27
Here is the new idea of string theory.
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Her er strengteoriens nye idé.
10:29
Deep inside any of these particles, there is something else.
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Dybt inde i enhver af disse partikler, er der noget andet.
10:34
This something else is this dancing filament of energy.
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Dette noget andet er dette dansende fiber af energi.
10:37
It looks like a vibrating string --
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Det ligner en vibrerende streng --
10:39
that's where the idea, string theory comes from.
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det er her, idéen superstrengteori kommer fra.
10:41
And just like the vibrating strings that you just saw in a cello
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Og ligesom de vibrerende strenge, som I lige så i en cello,
10:44
can vibrate in different patterns,
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kan vibrere i forskellige mønstre,
10:46
these can also vibrate in different patterns.
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kan disse også vibrere i forskellige mønstre.
10:48
They don't produce different musical notes.
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De producerer ikke forskellige musikalske toner.
10:50
Rather, they produce the different particles making up the world around us.
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I stedet producerer de de forskellige partikler, som verden omkring os er opbygget af.
10:54
So if these ideas are correct,
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Så hvis disse idéer er korrekte,
10:55
this is what the ultra-microscopic landscape of the universe looks like.
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er det sådan her, universets ultramikroskopiske landskab ser ud.
11:00
It's built up of a huge number
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Det er opbygget af et enormt antal
11:02
of these little tiny filaments of vibrating energy,
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af disse bittesmå fibre af vibrerende energi,
11:06
vibrating in different frequencies.
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der vibrerer med forskellige frekvenser.
11:08
The different frequencies produce the different particles.
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De forskellige frekvenser producerer de forskellige partikler.
11:11
The different particles are responsible
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De forskellige partikler er ansvarlige
11:14
for all the richness in the world around us.
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for mangfoldigheden i verden omkring os.
11:17
And there you see unification,
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Og der ser I samlingen,
11:19
because matter particles, electrons and quarks,
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for stofpartikler, elektroner og kvarker,
11:22
radiation particles, photons, gravitons, are all built up from one entity.
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strålingspartikler, fotoner, gravitoner, er alle opbygget af denne ene størrelse.
11:28
So matter and the forces of nature all are put together
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Så stof og naturens kræfter bliver alle sat sammen
11:32
under the rubric of vibrating strings.
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under overskriften vibrerende strenge.
11:34
And that's what we mean by a unified theory.
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Og det er det, vi mener med en samlet teori.
11:38
Now here is the catch.
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Nå, her er hagen.
11:40
When you study the mathematics of string theory,
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Når man studerer strengteoriens matematik,
11:43
you find that it doesn't work
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opdager man, at den ikke virker
11:45
in a universe that just has three dimensions of space.
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i et univers, der kun har tre rumdimensioner.
11:48
It doesn't work in a universe with four dimensions of space, nor five, nor six.
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Den virker ikke i et univers med fire rumdimensioner, eller fem, eller seks.
11:52
Finally, you can study the equations, and show that it works
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Endelig kan man studere ligningerne og vise, at den virker
11:56
only in a universe that has 10 dimensions of space
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kun i et univers, der har 10 rumdimensioner
12:00
and one dimension of time.
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og en tidsdimension.
12:02
It leads us right back to this idea of Kaluza and Klein --
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Det leder os lige tilbage til Kaluzas og Kleins idé --
12:07
that our world, when appropriately described,
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at vores verden, når ordnetligt beskrevet,
12:10
has more dimensions than the ones that we see.
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har flere dimensioner end dem, vi ser.
12:13
Now you might think about that and say, well,
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Nu kan man tænke over det og sige, altså,
12:16
OK, you know, if you have extra dimensions, and they're really tightly curled up,
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OK, jamen, hvis man har ekstra dimensioner, og de er virkelig sammenkrøllede,
12:19
yeah, perhaps we won't see them, if they're small enough.
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jah, ser vi dem måske ikke, hvis de er små nok.
12:23
But if there's a little tiny civilization of green people walking around down there,
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Men hvis der er en lillebitte civilisation af grønne folk, der går rundt dernede,
12:26
and you make them small enough, and we won't see them either. That is true.
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og man gør dem små nok, og man heller ikke kan se dem. Det er sandt.
12:31
One of the other predictions of string theory --
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En af strengteoriens andre forudsigelser --
12:34
no, that's not one of the other predictions of string theory.
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nej, det er ikke en af de andre af strengteoriens forudsigelser.
12:37
(Laughter)
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(Latter)
12:38
But it raises the question:
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Men det rejser spørgsmålet:
12:40
are we just trying to hide away these extra dimensions,
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forsøger vi bare at skjule disse ekstra dimensioner,
12:42
or do they tell us something about the world?
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eller fortæller de os noget om verden?
12:45
In the remaining time, I'd like to tell you two features of them.
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I den resterende tid vil jeg gerne fortælle jer om to egenskaber ved dem.
12:49
First is, many of us believe that these extra dimensions
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Den første er, mange af os tror, at disse ekstra dimensioner
12:53
hold the answer to what perhaps is the deepest question
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holder på svaret på, hvad måske er det dybeste spørgsmål
12:57
in theoretical physics, theoretical science.
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i teoretisk fysik, teoretisk videnskab.
13:00
And that question is this: when we look around the world,
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Og det spørgsmål er dette: når vi ser rundt i verden,
13:04
as scientists have done for the last hundred years,
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som videnskabsmænd har gjort i de sidste hundrede år,
13:06
there appear to be about 20 numbers that really describe our universe.
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lader der til at være omkring 20 tal, der virkelig beskriver vores univers.
13:10
These are numbers like the mass of the particles,
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Disse er tal som massen af partiklerne,
13:13
like electrons and quarks, the strength of gravity,
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som elektroner og kvarker, tyngdekraftens styrker,
13:15
the strength of the electromagnetic force --
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den elektromagnetiske krafts styrke --
13:17
a list of about 20 numbers
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en liste med omkring 20 tal,
13:19
that have been measured with incredible precision,
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der er blevet målt med utrolig præcision,
13:22
but nobody has an explanation
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men ingen har en forklaring
13:24
for why the numbers have the particular values that they do.
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på, hvorfor tallene lige præcis har de værdier, de har.
13:28
Now, does string theory offer an answer?
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Nå, tilbyder strengteori et svar?
13:31
Not yet.
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Ikke endnu.
13:32
But we believe the answer for why those numbers have the values they do
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Men vi tror, svaret på, hvorfor de tal har de værdier, de har,
13:36
may rely on the form of the extra dimensions.
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kan være afhængig af de ekstra dimensioners form.
13:39
And the wonderful thing is, if those numbers
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Og den vidunderlige ting er, hvis de tal
13:41
had any other values than the known ones,
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havde andre værdier end de kendte,
13:44
the universe, as we know it, wouldn't exist.
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ville universet, som vi kender det, ikke eksistere.
13:47
This is a deep question.
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Dette er et dybt spørgsmål.
13:48
Why are those numbers so finely tuned
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Hvorfor er de tal så fint tilpassede
13:50
to allow stars to shine and planets to form,
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til at tillade stjerner at skinne og planeter at formes,
13:52
when we recognize that if you fiddle with those numbers --
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når vi indser, at hvad man roder med de tal --
13:55
if I had 20 dials up here
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hvis jeg havde 20 knapper heroppe,
13:57
and I let you come up and fiddle with those numbers,
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og hvis jeg lod jer komme op og rode med de tal,
13:59
almost any fiddling makes the universe disappear.
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ville næsten enhver roden få universet til at forsvinde.
14:03
So can we explain those 20 numbers?
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Så kan vi forklare de 20 tal?
14:06
And string theory suggests that those 20 numbers
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Og strengteorien foreslår, at de 20 tal
14:08
have to do with the extra dimensions.
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har noget at gøre med de ekstra dimensioner.
14:10
Let me show you how.
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Lad mig vise jer hvordan.
14:12
So when we talk about the extra dimensions in string theory,
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Så når man taler om strengteoriens ekstra dimensioner,
14:16
it's not one extra dimension,
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er det ikke én ekstra dimension
14:18
as in the older ideas of Kaluza and Klein.
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som i Kaluzas og Kleins gamle idéer.
14:22
This is what string theory says about the extra dimensions.
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Det er det, strengteori siger om de ekstra dimensioner.
14:25
They have a very rich, intertwined geometry.
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De har en meget rig, sammenflettet geometri.
14:28
This is an example of something known as a Calabi-Yau shape --
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Dette er et eksempel på noget kendt som en Calabi-Yau form --
14:32
name isn't all that important.
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navnet er ikke så vigtigt.
14:34
But, as you can see,
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Men som I kan se,
14:36
the extra dimensions fold in on themselves
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folder de ekstra dimensioner sammen om hinanden
14:39
and intertwine in a very interesting shape, interesting structure.
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og snor sig sammen i en meget interessant form, interessant struktur.
14:43
And the idea is that if this is what the extra dimensions look like,
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Og idéen er, at hvis det er sådan, de ekstra dimensioner ser ud,
14:48
then the microscopic landscape of our universe all around us
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så ville vores univers' mikroskopiske landskab omkring os
14:52
would look like this on the tiniest of scales.
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se sådan ud på allermindste skala.
14:54
When you swing your hand,
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Når man svinger sin hånd,
14:55
you'd be moving around these extra dimensions over and over again,
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vil man bevæge sig om disse ekstra dimensioner igen og igen,
14:58
but they're so small that we wouldn't know it.
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men de er så små, at man ikke ville opdage det.
15:00
So what is the physical implication, though, relevant to those 20 numbers?
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Så hvad er den fysiske implikation med hensyn til de 20 tal?
15:03
Consider this. If you look at the instrument, a French horn,
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Overvej dette. Hvis I ser på instrumentet, et valdhorn,
15:06
notice that the vibrations of the airstreams
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bemærk, at luftstrømmenes vibrationer
15:09
are affected by the shape of the instrument.
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bliver påvirket af instrumentets form.
15:11
Now in string theory,
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I strengteori
15:13
all the numbers are reflections of the way strings can vibrate.
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afspejler alle tallene måderne, hvorpå strenge kan vibrere.
15:16
So just as those airstreams
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Så ligesom de luftstrømme
15:18
are affected by the twists and turns in the instrument,
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bliver påvirket af snoningerne og drejningerne i instrumentet,
15:21
strings themselves will be affected
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vil strenge selv blive påvirket
15:23
by the vibrational patterns in the geometry within which they are moving.
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af geometriens vibrationsmønstre, i hvilke de bevæger sig.
15:27
So let me bring some strings into the story.
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Så lad mig bringe nogle strenge ind i historien.
15:29
And if you watch these little fellows vibrating around --
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Og hvis I ser på disse små fyre, der vibrerer rundt --
15:32
they'll be there in a second -- right there,
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de er der om et sekund -- lige der,
15:34
notice that they way they vibrate is affected
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bemærk, at den måde, de vibrerer bliver påvirket
15:36
by the geometry of the extra dimensions.
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af de ekstra dimensioners geometri.
15:38
So, if we knew exactly what the extra dimensions look like --
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Så, hvis vi præcist vidste, hvordan de ekstra dimensioner ser ud --
15:41
we don't yet, but if we did --
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det gør vi ikke endnu, men hvis nu --
15:43
we should be able to calculate the allowed notes,
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burde vi være i stand til at beregne de tilladte toner,
15:46
the allowed vibrational patterns.
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de tilladte vibrationsmønstre.
15:48
And if we could calculate the allowed vibrational patterns,
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Og hvis vi kunne beregne de tilladte vibrationsmønstre,
15:51
we should be able to calculate those 20 numbers.
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burde vi være i stand til at beregne de 20 tal.
15:54
And if the answer that we get from our calculations
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Og hvis svaret, som vi får fra vores beregninger,
15:58
agrees with the values of those numbers
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stemmer overens med de tals værdier,
16:00
that have been determined
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der er blevet fastslået
16:02
through detailed and precise experimentation,
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gennem detaljerede og præcise eksperimenter,
16:05
this in many ways would be the first fundamental explanation
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ville dette på mange måder være den første fundamentale forklaring
16:10
for why the structure of the universe is the way it is.
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på, hvorfor universets struktur er, som den er.
16:15
Now, the second issue that I want to finish up with is:
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Nå, det andet, som jeg gerne vil afslutte med, er dette:
16:18
how might we test for these extra dimensions more directly?
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hvordan kan vi teste for disse ekstra dimensioner mere direkte?
16:23
Is this just an interesting mathematical structure
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Er dette bare en interessant matematisk struktur,
16:26
that might be able to explain
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der måske kunne forklare
16:28
some previously unexplained features of the world,
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nogle tidligere uforklarede egenskaber ved verden,
16:33
or can we actually test for these extra dimensions?
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eller kan vi faktisk teste for disse ekstra dimensioner?
16:36
And we think -- and this is, I think, very exciting --
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Og vi tror -- og dette er, synes jeg, meget spændende --
16:38
that in the next five years or so we may be able to test
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at i de næste fem år cirka bliver vi måske i stand til at teste
16:42
for the existence of these extra dimensions.
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for disse ekstra dimensioners eksistens.
16:45
Here's how it goes. In CERN, Geneva, Switzerland,
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Sådan her bliver det. Ved CERN, Geneve, Schweiz,
16:49
a machine is being built called the Large Hadron Collider.
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bliver en maskine bygget ved navn Large Hadron Collider.
16:53
It's a machine that will send particles around a tunnel,
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Den er en maskine, der vil sende partikler rundt i en tunnel,
16:56
opposite directions, near the speed of light.
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modsatte retninger, nær lysets hastighed.
16:58
Every so often those particles will be aimed at each other,
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Med jævne mellemrun bliver de partikler rettet mod hinanden,
17:02
so there's a head-on collision.
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så der sker en frontalkollision.
17:04
The hope is that if the collision has enough energy,
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Håbet er, at hvis kollisionen har energi nok,
17:08
it may eject some of the debris from the collision
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vil den slynge nogle af stumperne fra kollisionen
17:11
from our dimensions, forcing it to enter into the other dimensions.
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fra vores dimension og tvinge dem ind i de andre dimensioner.
17:16
How would we know it?
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Hvordan ville vi vide det?
17:18
Well, we'll measure the amount of energy after the collision,
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Altså vi vil måle mængden af energi efter kollisionen,
17:21
compare it to the amount of energy before,
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sammenligne den med mængden af energi før,
17:23
and if there's less energy after the collision than before,
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og hvis der er mindre energi efter kollisionen end før,
17:27
this will be evidence that the energy has drifted away.
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vil dette være bevis for, at energien er drevet væk.
17:29
And if it drifts away in the right pattern that we can calculate,
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Og hvis den driver væk i det rigtige mønster, som vi kan beregne,
17:32
this will be evidence that the extra dimensions are there.
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vil dette være bevis for, at de ekstra dimensioner er der.
17:35
Let me show you that idea visually.
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Lad mig vise jer den idé visuelt.
17:37
So, imagine we have a certain kind of particle called a graviton --
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Så, forestil jer, vi har en bestemt type partikel kaldet en graviton --
17:40
that's the kind of debris we expect to be ejected out,
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det er den slags stumper, vi forventer vil blive slynget ud,
17:44
if the extra dimensions are real.
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hvis de ekstra dimensioner er virkelige.
17:46
But here's how the experiment will go.
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Men her er, hvordan eksperimentet vil forløbe.
17:47
You take these particles. You slam them together.
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Man tager disse partikler. Man slår dem sammen.
17:50
You slam them together, and if we are right,
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Man slår dem sammen, og hvis vi har ret,
17:52
some of the energy of that collision
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vil noget af den kollisions energi
17:54
will go into debris that flies off into these extra dimensions.
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blive slået i stumper, der flyver ud i disse ekstra dimensioner.
17:58
So this is the kind of experiment
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Så dette er den type eksperiment,
18:00
that we'll be looking at in the next five, seven to 10 years or so.
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som vi vil se på i de næste fem, syv til 10 år cirka.
18:04
And if this experiment bears fruit,
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Og hvis dette eksperiment bærer frugt,
18:07
if we see that kind of particle ejected
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hvis vi ser den type partikel blive slynget ud
18:10
by noticing that there's less energy in our dimensions
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ved at bemærke, at der er mindre energi i vores dimensioner,
18:13
than when we began,
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end da vi begyndte,
18:15
this will show that the extra dimensions are real.
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vil dette vise, at de ekstra dimensioner findes.
18:18
And to me this is a really remarkable story,
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Og for mig er dette en virkelig usædvanlig historie
18:21
and a remarkable opportunity. Going back to Newton with absolute space --
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og en usædvanlig mulighed. Tilbage til Newton med absolut rum --
18:25
didn't provide anything but an arena, a stage
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gav ikke andet end en arena, en scene,
18:27
in which the events of the universe take place.
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på hvilken universets begivenheder finder sted.
18:29
Einstein comes along and says,
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Einstein kommer forbi og siger,
18:31
well, space and time can warp and curve -- that's what gravity is.
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altså, rum og tid kan forvride sig og kurve, det er det, der er tyngdekraften.
18:34
And now string theory comes along and says,
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Og nu kommer strengteori forbi og siger,
18:38
yes, gravity, quantum mechanics, electromagnetism,
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ja, tyngdekraften, kvantemekanik, elektromagnetisme --
18:41
all together in one package,
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alt sammen i én pakke,
18:43
but only if the universe has more dimensions than the ones that we see.
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men kun hvis universet har flere dimensioner end dem, som vi ser.
18:47
And this is an experiment that may test for them in our lifetime.
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Og dette er et eksperiment, som kan teste for dem i vores livstid.
18:52
Amazing possibility.
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Utrolig mulighed.
18:54
Thank you very much.
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Mange tak.
18:56
(Applause)
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(Bifald)
ABOUT THE SPEAKER
Brian Greene - PhysicistBrian Greene is perhaps the best-known proponent of superstring theory, the idea that minuscule strands of energy vibrating in a higher dimensional space-time create every particle and force in the universe.
Why you should listen
Greene, a professor of physics and mathematics at Columbia University, has focused on unified theories for more than 25 years, and has written several best-selling and non-technical books on the subject including The Elegant Universe, a Pulitzer finalist, and The Fabric of the Cosmos — each of which has been adapted into a NOVA mini-series. His latest book, The Hidden Reality, explores the possibility that our universe is not the only universe.
Greene believes science must be brought to general audiences in new and compelling ways, such as his live stage odyssey, Icarus at the Edge of Time, with original orchestral score by Philip Glass, and the annual World Science Festival, which he co-founded in 2008 with journalist Tracy Day.
Brian Greene | Speaker | TED.com