TEDxCaltech
Sean Carroll: Distant time and the hint of a multiverse
Sean Carroll: Fjern tid og antydningen af et multivers
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Ved TEDxCaltech angriber kosmolog Sean Carroll -- i en underholdende og tankeprovokerende tur gennem tidens og universets natur -- et vildledende simpelt spørgsmål: Hvorfor eksisterer tid overhovedet? De potentielle svar peger på et overraskende syn på universets natur og vores plads i det.
Sean M. Carroll - Physicist, cosmologist
A physicist, cosmologist and gifted science communicator, Sean Carroll is asking himself -- and asking us to consider -- questions that get at the fundamental nature of the universe. Full bio
A physicist, cosmologist and gifted science communicator, Sean Carroll is asking himself -- and asking us to consider -- questions that get at the fundamental nature of the universe. Full bio
Double-click the English transcript below to play the video.
00:15
The universe
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Universet
00:17
is really big.
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er virkelig stort.
00:19
We live in a galaxy, the Milky Way Galaxy.
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Vi lever i en galakse, Mælkevejen.
00:22
There are about a hundred billion stars in the Milky Way Galaxy.
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Der er omkring et hundrede milliarder stjerner i Mælkevejen.
00:25
And if you take a camera
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Og hvis man tager et kamera,
00:27
and you point it at a random part of the sky,
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og man peger det på en tilfældig del af himlen,
00:29
and you just keep the shutter open,
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og man bare holder blænderen åben,
00:31
as long as your camera is attached to the Hubble Space Telescope,
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så længe ens kamera er fæstnet til Hubble-rumteleskopet
00:34
it will see something like this.
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vil det se noget som dette.
00:36
Every one of these little blobs
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Hver eneste af disse små klatter
00:39
is a galaxy roughly the size of our Milky Way --
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er en galakse nogenlunde på størrelse med vores Mælkevej --
00:41
a hundred billion stars in each of those blobs.
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et hundrede milliarder stjerner i hver af de klatter.
00:44
There are approximately a hundred billion galaxies
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Der er omkring et hundrede milliarder galakser
00:47
in the observable universe.
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i det observerbare univers.
00:49
100 billion is the only number you need to know.
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100 milliarder er det eneste tal, man behøver at kende.
00:51
The age of the universe, between now and the Big Bang,
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Universets alder, mellem nu og Big Bang,
00:54
is a hundred billion in dog years.
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er et hundrede milliarder i hundeår.
00:56
(Laughter)
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(Latter)
00:58
Which tells you something about our place in the universe.
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Hvilket fortæller jer noget om vores plads i universet.
01:01
One thing you can do with a picture like this is simply admire it.
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En ting, man kan gøre med et billede som dette, er simpelthen at beundre det.
01:03
It's extremely beautiful.
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Det er ekstremt smukt.
01:05
I've often wondered, what is the evolutionary pressure
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Jeg har ofte undret mig over hvilke evolutionspres,
01:08
that made our ancestors in the Veldt adapt and evolve
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der fik vores forfædre i Velden tilpasse og udvikle sig
01:11
to really enjoy pictures of galaxies
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til virkelig at nyde billeder af galakser,
01:13
when they didn't have any.
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når de ikke havde nogen.
01:15
But we would also like to understand it.
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Men vi kunne også tænke os at forstå det.
01:17
As a cosmologist, I want to ask, why is the universe like this?
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Som kosmolog vil jeg gerne spørge, hvorfor er universet sådan her?
01:21
One big clue we have is that the universe is changing with time.
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Et stort spor, vi har, er, at universet forandrer sig med tiden.
01:24
If you looked at one of these galaxies and measured its velocity,
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Hvis man så på en af disse galakser og målte dens hastighed,
01:27
it would be moving away from you.
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ville den bevæge sig væk fra en.
01:29
And if you look at a galaxy even farther away,
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Og hvis man ser på en galakse endnu længere væk,
01:31
it would be moving away faster.
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ville den bevæge sig endnu hurtigere væk.
01:33
So we say the universe is expanding.
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Så vi siger, universet udvider sig.
01:35
What that means, of course, is that, in the past,
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Hvad det betyder er selvfølgelig, at før i tiden
01:37
things were closer together.
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var ting tættere på hinanden.
01:39
In the past, the universe was more dense,
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Før i tiden var universet tættere,
01:41
and it was also hotter.
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og det var også varmere.
01:43
If you squeeze things together, the temperature goes up.
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Hvis man presser ting sammen, går temperaturen op.
01:45
That kind of makes sense to us.
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Det giver på en måde mening for os.
01:47
The thing that doesn't make sense to us as much
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Det, der ikke giver så meget mening for os,
01:49
is that the universe, at early times, near the Big Bang,
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er, at universet i tidlige tider nær Big Bang
01:52
was also very, very smooth.
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også var meget, meget glat.
01:54
You might think that that's not a surprise.
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Man kunne tro, at det ikke er en overraskelse.
01:56
The air in this room is very smooth.
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Luften i dette rum er meget glat.
01:58
You might say, "Well, maybe things just smoothed themselves out."
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Man kunne sige, "Jamen, måske glattede ting bare sig selv ud."
02:01
But the conditions near the Big Bang are very, very different
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Men vilkårene nær Big Bang er meget, meget forskellige
02:04
than the conditions of the air in this room.
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fra vilkårene for luften i dette rum.
02:06
In particular, things were a lot denser.
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Især var ting meget tættere.
02:08
The gravitational pull of things
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Tingenes gravitationelle træk
02:10
was a lot stronger near the Big Bang.
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var meget stærkere nær Big Bang.
02:12
What you have to think about
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Det, man er nødt til at tænke på,
02:14
is we have a universe with a hundred billion galaxies,
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er, vi har et univers med et hundrede milliarder galakser,
02:16
a hundred billion stars each.
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et hundrede milliarder stjerner hver.
02:18
At early times, those hundred billion galaxies
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I tidlige tider var de hundrede milliarder galakser
02:21
were squeezed into a region about this big --
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presset ind på et område nogenlunde så stort her --
02:24
literally -- at early times.
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bogstaveligt talt -- i tidlige tider.
02:26
And you have to imagine doing that squeezing
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Og I skal forestille jer, at presse på den måde
02:28
without any imperfections,
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uden nogen ujævnheder,
02:30
without any little spots
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uden nogen små steder,
02:32
where there were a few more atoms than somewhere else.
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hvor der var få flere atomer end nogen andre steder.
02:34
Because if there had been, they would have collapsed under the gravitational pull
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For hvis der havde været det, ville de have kollapset under det gravitationelle træk
02:37
into a huge black hole.
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ind i et stort sort hul.
02:39
Keeping the universe very, very smooth at early times
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At holde universet meget, meget glat i tidlige tider
02:42
is not easy; it's a delicate arrangement.
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er ikke let; det er et skrøbeligt arrangement.
02:44
It's a clue
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Det er et spor om,
02:46
that the early universe is not chosen randomly.
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at det tidlige univers ikke blev valgt tilfældigt.
02:48
There is something that made it that way.
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Der er noget, der lavede det på den måde.
02:50
We would like to know what.
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Vi kunne godt tænke os at vide hvad.
02:52
So part of our understanding of this was given to us by Ludwig Boltzmann,
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Så en del af vores forståelse af dette blev givet til os af Ludwig Boltzmann,
02:55
an Austrian physicist in the 19th century.
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en østrigsk fysiker i det 19. århundrede.
02:58
And Boltzmann's contribution was that he helped us understand entropy.
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Og Boltzmanns bidrag var, at han hjalp os med at forstå entropi.
03:01
You've heard of entropy.
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I har hørt om entropi.
03:03
It's the randomness, the disorder, the chaoticness of some systems.
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Det er tilfældigheden, urodenen, kaosheden i nogle systemer.
03:06
Boltzmann gave us a formula --
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Boltzmann gav os en formel --
03:08
engraved on his tombstone now --
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indgraveret på hans gravsten nu --
03:10
that really quantifies what entropy is.
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som virkelig kvantificerer, hvad entropi er.
03:12
And it's basically just saying
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Og den siger basalt set bare,
03:14
that entropy is the number of ways
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at entropi er antallet af måder,
03:16
we can rearrange the constituents of a system so that you don't notice,
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man kan omarrangere et systems bestanddele, så at man ikke ikke kan se det,
03:19
so that macroscopically it looks the same.
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så at makroskopisk ser ligner det sig selv.
03:21
If you have the air in this room,
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Hvis man tager luften i dette rum,
03:23
you don't notice each individual atom.
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lægger man ikke mærke til hvert enkelt atom.
03:26
A low entropy configuration
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En konfiguration med lav entropi
03:28
is one in which there's only a few arrangements that look that way.
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er en, i hvilken der kun er få arrangementer, der ser ens ud.
03:30
A high entropy arrangement
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Et arrangement med høj entropi
03:32
is one that there are many arrangements that look that way.
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er et, som der er mange arrangementer, der ser ens ud.
03:34
This is a crucially important insight
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Dette er et afgørende vigtigt indblik,
03:36
because it helps us explain
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for det hjælper os med at forklare
03:38
the second law of thermodynamics --
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termodynamikkens anden lov --
03:40
the law that says that entropy increases in the universe,
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den lov, der siger, at entropi stiger i universet
03:43
or in some isolated bit of the universe.
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eller i en isoleret lille del af universet.
03:45
The reason why entropy increases
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Grunden til, at entropi stiger,
03:47
is simply because there are many more ways
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er simpelthen fordi, der er mange flere måder
03:50
to be high entropy than to be low entropy.
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at have høj entropi end at have lav entropi på.
03:52
That's a wonderful insight,
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Det er et vidunderligt indblik,
03:54
but it leaves something out.
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men det udelader noget.
03:56
This insight that entropy increases, by the way,
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Dette indblik, at entropi stiger er forresten
03:58
is what's behind what we call the arrow of time,
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det, der er bag det, vi kalder tidens pil,
04:01
the difference between the past and the future.
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forskellen mellem fortiden og fremtiden.
04:03
Every difference that there is
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Hver forskel, som der er
04:05
between the past and the future
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mellem fortiden og fremtiden,
04:07
is because entropy is increasing --
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er, fordi entropi stiger --
04:09
the fact that you can remember the past, but not the future.
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det faktum, at man kan huske fortiden, men ikke fremtiden.
04:12
The fact that you are born, and then you live, and then you die,
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Det faktum, at man bliver født, og så lever man, og så dør man,
04:15
always in that order,
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altid i den rækkefølge,
04:17
that's because entropy is increasing.
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det er fordi, entropi stiger.
04:19
Boltzmann explained that if you start with low entropy,
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Boltzmann forklarede, at hvis man starter med lav entropi,
04:21
it's very natural for it to increase
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er det meget naturligt for den at stige,
04:23
because there's more ways to be high entropy.
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fordi der er flere måder at få høj entropi på.
04:26
What he didn't explain
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Det, han ikke forklarede,
04:28
was why the entropy was ever low in the first place.
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var, hvorfor entropien nogensinde var lav i første omgang.
04:31
The fact that the entropy of the universe was low
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Det faktum, at universets entropi var lav,
04:33
was a reflection of the fact
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var en refleksion over det faktum,
04:35
that the early universe was very, very smooth.
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at det tidlige univers var meget, meget glat.
04:37
We'd like to understand that.
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Vi kunne godt tænke os at forstå det.
04:39
That's our job as cosmologists.
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Det er vores job som kosmologer.
04:41
Unfortunately, it's actually not a problem
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Desværre er det faktisk ikke et problem,
04:43
that we've been giving enough attention to.
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som vi har givet nok opmærksomhed.
04:45
It's not one of the first things people would say,
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Det er ikke en af de første ting, folk ville sige,
04:47
if you asked a modern cosmologist,
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hvis man spurgte en moderne kosmolog,
04:49
"What are the problems we're trying to address?"
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"Hvilke problemer forsøger vi at besvare?"
04:51
One of the people who did understand that this was a problem
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En af de folk, der forstod, at dette var et problem,
04:53
was Richard Feynman.
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var Richard Feynman.
04:55
50 years ago, he gave a series of a bunch of different lectures.
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For 50 år siden gav han en serie af en bunke forskellige foredrag.
04:57
He gave the popular lectures
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Han gav de populære foredrag,
04:59
that became "The Character of Physical Law."
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der blev til "The Character of Physical Law."
05:01
He gave lectures to Caltech undergrads
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Han gav foredrag til Caltech førsteårsstuderende,
05:03
that became "The Feynman Lectures on Physics."
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som blev til "The Feynman Lectures on Physics."
05:05
He gave lectures to Caltech graduate students
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Han gav foredrag til Caltech kandidatstuderende,
05:07
that became "The Feynman Lectures on Gravitation."
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der blev til "The Feynman Lectures on Gravitation."
05:09
In every one of these books, every one of these sets of lectures,
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I hver eneste af disse bøger, hver eneste af disse foredragssæt
05:12
he emphasized this puzzle:
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understregede han denne gåde:
05:14
Why did the early universe have such a small entropy?
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Hvorfor havde det tidlige univers så lav en entropi?
05:17
So he says -- I'm not going to do the accent --
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Så han siger -- jeg vil ikke gengive accenten --
05:19
he says, "For some reason, the universe, at one time,
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han siger, "Af en eller anden grund havde universet på et tidspunkt
05:22
had a very low entropy for its energy content,
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en meget lav entropi i forhold til dets energiindhold,
05:25
and since then the entropy has increased.
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og siden da er entropien steget.
05:27
The arrow of time cannot be completely understood
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Tidspilen kan ikke blive fuldstændigt forstået
05:30
until the mystery of the beginnings of the history of the universe
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før mysteriet om universets histories begyndelse
05:33
are reduced still further
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bliver reduceret endnu mere
05:35
from speculation to understanding."
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fra spekulation til forståelse."
05:37
So that's our job.
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Så det er vores job.
05:39
We want to know -- this is 50 years ago, "Surely," you're thinking,
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Vi vil gerne vide -- dette er for 50 år siden, "Jamen," tænker I,
05:41
"we've figured it out by now."
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"vi har vel fundet ud af det nu."
05:43
It's not true that we've figured it out by now.
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Det er ikke sandt, at vi har fundet ud af det nu.
05:45
The reason the problem has gotten worse,
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Grunden til, at problemet er blevet værre
05:47
rather than better,
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i stedet for bedre
05:49
is because in 1998
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er, at i 1998
05:51
we learned something crucial about the universe that we didn't know before.
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lærte vi noget meget vigtigt om universet, som vi ikke vidste før.
05:54
We learned that it's accelerating.
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Vi lærte, at det accelererer.
05:56
The universe is not only expanding.
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Universet udvider sig ikke kun.
05:58
If you look at the galaxy, it's moving away.
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Hvis man ser på galaksen, bevæger den sig væk.
06:00
If you come back a billion years later and look at it again,
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Hvis man kommer tilbage en milliard år senere og ser på den igen,
06:02
it will be moving away faster.
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vil den bevæge sig hurtigere væk.
06:05
Individual galaxies are speeding away from us faster and faster
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Individuelle galakser styrter væk fra os hurtigere og hurtigere,
06:08
so we say the universe is accelerating.
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så vi siger, universet accelererer.
06:10
Unlike the low entropy of the early universe,
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I modsætningen til det tidlige univers' lave entropi,
06:12
even though we don't know the answer for this,
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selvom vi ikke kender svaret på dette,
06:14
we at least have a good theory that can explain it,
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har vi i det mindste en god teori, der kan forklare det,
06:16
if that theory is right,
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hvis den teori er korrekt,
06:18
and that's the theory of dark energy.
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og det er teorien om mørk energi.
06:20
It's just the idea that empty space itself has energy.
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Det er bare idéen, at tomt rum i sig selv har energi.
06:23
In every little cubic centimeter of space,
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I hver lille kubikcentimeter rum,
06:26
whether or not there's stuff,
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uanset om der er noget eller ej,
06:28
whether or not there's particles, matter, radiation or whatever,
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uanset om der er partikler, stof, stråling eller andet eller ej,
06:30
there's still energy, even in the space itself.
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er der stadig energi, selv i rummet selv.
06:33
And this energy, according to Einstein,
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Og denne energi udøver ifølge Einstein
06:35
exerts a push on the universe.
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et skub på universet.
06:38
It is a perpetual impulse
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Det er en uophørlig impuls,
06:40
that pushes galaxies apart from each other.
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der skubber galakser væk fra hinanden.
06:42
Because dark energy, unlike matter or radiation,
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For mørk energi, i modsætningen til stof eller stråling,
06:45
does not dilute away as the universe expands.
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tynder ikke ud som universet udvider sig.
06:48
The amount of energy in each cubic centimeter
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Mængden af energi i hver kubikcentimeter
06:50
remains the same,
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forbliver den samme,
06:52
even as the universe gets bigger and bigger.
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selv som universet bliver større og større.
06:54
This has crucial implications
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Dette har meget vigtige implikationer
06:57
for what the universe is going to do in the future.
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for, hvad universet vil gøre i fremtiden.
07:00
For one thing, the universe will expand forever.
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For det første vil universet udvide sig for evigt.
07:02
Back when I was your age,
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Dengang da jeg var på jeres alder,
07:04
we didn't know what the universe was going to do.
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vidste vi ikke, hvad universet ville gøre.
07:06
Some people thought that the universe would recollapse in the future.
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Nogle folk troede, at universet ville falde sammen igen i fremtiden.
07:09
Einstein was fond of this idea.
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Einstein var tilhænger af denne idé.
07:11
But if there's dark energy, and the dark energy does not go away,
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Men hvis der er mørk energi, og den mørke energi ikke forsvinder,
07:14
the universe is just going to keep expanding forever and ever and ever.
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vil universet bare fortsætte med at udvide sig for evigt og altid og altid.
07:17
14 billion years in the past,
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14 milliarder år i fortiden,
07:19
100 billion dog years,
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100 milliarder hundeår,
07:21
but an infinite number of years into the future.
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men et uendeligt antal år i fremtiden.
07:24
Meanwhile, for all intents and purposes,
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Imens, til alle hensigter og formål,
07:27
space looks finite to us.
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ser rummet endeligt ud for os.
07:29
Space may be finite or infinite,
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Rummet kan være endeligt eller uendeligt,
07:31
but because the universe is accelerating,
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men fordi universet accelererer,
07:33
there are parts of it we cannot see
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er der dele af det vi ikke kan se
07:35
and never will see.
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og aldrig vil se.
07:37
There's a finite region of space that we have access to,
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Der er en endelig del af rummet, som vi har adgang til,
07:39
surrounded by a horizon.
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omringet af en horisont.
07:41
So even though time goes on forever,
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Så selv om tiden fortsætter for evigt,
07:43
space is limited to us.
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er rummet begrænset for os.
07:45
Finally, empty space has a temperature.
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Endelig har rum en temperatur.
07:48
In the 1970s, Stephen Hawking told us
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I 1970'erne fortalte Stephen Hawking os,
07:50
that a black hole, even though you think it's black,
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at et sort hul, selvom man tror det er sort,
07:52
it actually emits radiation
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faktisk afgiver stråling,
07:54
when you take into account quantum mechanics.
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når man tager kvantemekanik med i overvejelserne.
07:56
The curvature of space-time around the black hole
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Krumningen af rumtiden omkring det sorte hul
07:59
brings to life the quantum mechanical fluctuation,
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bringer de kvantemekaniske fluktuationer til live,
08:02
and the black hole radiates.
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og det sorte hul stråler.
08:04
A precisely similar calculation by Hawking and Gary Gibbons
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En præcist lignende udregning af Hawking og Gary Gibbons
08:07
showed that if you have dark energy in empty space,
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viste, at hvis man har mørk energi i tomt rum,
08:10
then the whole universe radiates.
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så stråler hele universet.
08:13
The energy of empty space
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Det tomme rums energi
08:15
brings to life quantum fluctuations.
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bringer kvantefluktuationer til live.
08:17
And so even though the universe will last forever,
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Og derfor, selvom universet vil vare for evigt,
08:19
and ordinary matter and radiation will dilute away,
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og normalt stof og stråling vil blive udvandet til det forsvinder,
08:22
there will always be some radiation,
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vil der altid være noget stråling,
08:24
some thermal fluctuations,
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nogle termiske fluktuationer,
08:26
even in empty space.
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selv i tomt rum.
08:28
So what this means
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Så det, det her betyder,
08:30
is that the universe is like a box of gas
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er, at universet er som en kasse med gas,
08:32
that lasts forever.
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der varer evigt.
08:34
Well what is the implication of that?
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Nå, hvad er implikationen af det?
08:36
That implication was studied by Boltzmann back in the 19th century.
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Den implikation blev studeret af Boltzmann tilbage i det 19. århundrede.
08:39
He said, well, entropy increases
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Han sagde, altså, entropi stiger,
08:42
because there are many, many more ways
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fordi der er mange, mange flere måder
08:44
for the universe to be high entropy, rather than low entropy.
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for universet at have høj entropi end at have lav entropi.
08:47
But that's a probabilistic statement.
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Men det er en probabilistisk udtalelse.
08:50
It will probably increase,
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Den vil sandsynligvis stige,
08:52
and the probability is enormously huge.
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og sandsynligheden er enormt stor.
08:54
It's not something you have to worry about --
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Det er ikke noget, man skal bekymre sig om --
08:56
the air in this room all gathering over one part of the room and suffocating us.
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at luften i dette rum alt sammen skulle samle sig ovre i én del af rummet og kvæle os.
09:00
It's very, very unlikely.
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Det er meget, meget usandsynligt.
09:02
Except if they locked the doors
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Bortset fra hvis de låste dørene
09:04
and kept us here literally forever,
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og holdt os her bogstaveligt talt for evigt,
09:06
that would happen.
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ville det ske.
09:08
Everything that is allowed,
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Alt, der er tilladt,
09:10
every configuration that is allowed to be obtained by the molecules in this room,
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enhver konfiguration, det er tilladt for molekylerne at opnå i dette rum,
09:13
would eventually be obtained.
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ville eventuelt blive opnået.
09:15
So Boltzmann says, look, you could start with a universe
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Så Boltzmann siger, altså, man kunne starte med et univers,
09:18
that was in thermal equilibrium.
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der var i termisk ligevægt.
09:20
He didn't know about the Big Bang. He didn't know about the expansion of the universe.
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Han kendte ikke til Big Bang. Han kendte ikke til universets udvidelse.
09:23
He thought that space and time were explained by Isaac Newton --
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Han troede, at rum og tid blev forklaret af Isaac Newton --
09:26
they were absolute; they just stuck there forever.
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de var absolutte; de sad der bare for evigt.
09:28
So his idea of a natural universe
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Så hans opfattelse af et naturligt univers
09:30
was one in which the air molecules were just spread out evenly everywhere --
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var en, hvori luftmolekylerne bare var spredt jævnt ud overalt --
09:33
the everything molecules.
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alt-molekylerne.
09:35
But if you're Boltzmann, you know that if you wait long enough,
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Men hvis man er Boltzmann, ved man, at hvis man venter længe nok,
09:38
the random fluctuations of those molecules
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vil de molekylers tilfældige fluktuationer
09:41
will occasionally bring them
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af og til bringe dem
09:43
into lower entropy configurations.
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ind i konfigurationer med lavere entropi.
09:45
And then, of course, in the natural course of things,
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Og så, selvfølgelig, efter tingenes naturlige rækkefølge,
09:47
they will expand back.
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vil de udvide sig tilbage.
09:49
So it's not that entropy must always increase --
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Så det er ikke fordi, entropi altid skal stige --
09:51
you can get fluctuations into lower entropy,
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man kan få fluktuationer til lavere entropi,
09:54
more organized situations.
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mere organiserede situationer.
09:56
Well if that's true,
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Jamen hvis det er sandt,
09:58
Boltzmann then goes onto invent
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går Boltzmann så videre til at opfinde
10:00
two very modern-sounding ideas --
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to idéer, der lyder meget moderne --
10:02
the multiverse and the anthropic principle.
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multiverset og det antropiske princip.
10:05
He says, the problem with thermal equilibrium
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Han siger, problemet med termisk ligevægt
10:07
is that we can't live there.
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er, at vi ikke kan leve der.
10:09
Remember, life itself depends on the arrow of time.
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Husk, livet selv afhænger af tidens pilen.
10:12
We would not be able to process information,
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Vi ville ikke være i stand til at bearbejde information,
10:14
metabolize, walk and talk,
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fordøje, gå og tale,
10:16
if we lived in thermal equilibrium.
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hvis vi levede i termisk ligevægt.
10:18
So if you imagine a very, very big universe,
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Så hvis man forestiller sig et meget, meget stort univers,
10:20
an infinitely big universe,
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et uendeligt stort univers
10:22
with randomly bumping into each other particles,
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med partikler, der tilfældigt støder ind i hinanden,
10:24
there will occasionally be small fluctuations in the lower entropy states,
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vil der af og til være små fluktuationer til tilstande med lavere entropi,
10:27
and then they relax back.
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og så falder de tilbage igen.
10:29
But there will also be large fluctuations.
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Men der vil også være store fluktuationer.
10:31
Occasionally, you will make a planet
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Af og til vil man lave en planet
10:33
or a star or a galaxy
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eller en stjerne eller en galakse
10:35
or a hundred billion galaxies.
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eller et hundrede milliarder galakser.
10:37
So Boltzmann says,
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Så Boltzmann siger,
10:39
we will only live in the part of the multiverse,
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vi kun vil leve i den del af multiverset,
10:42
in the part of this infinitely big set of fluctuating particles,
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i den del af dette uendeligt store sæt af fluktuerende partikler,
10:45
where life is possible.
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hvor liv er muligt.
10:47
That's the region where entropy is low.
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Det er den region, hvor entropi er lav.
10:49
Maybe our universe is just one of those things
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Måske er vores univers bare en af disse ting,
10:52
that happens from time to time.
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der sker fra tid til anden.
10:54
Now your homework assignment
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Nå jeres hjemmeopgave
10:56
is to really think about this, to contemplate what it means.
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er virkelig at tænke over dette, at overveje hvad det betyder.
10:58
Carl Sagan once famously said
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Carl Sagan sagde som bekendt engang,
11:00
that "in order to make an apple pie,
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at "for at lave en æbletærte,
11:02
you must first invent the universe."
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må man først opfinde universet."
11:05
But he was not right.
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Men han tog fejl.
11:07
In Boltzmann's scenario, if you want to make an apple pie,
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I Boltzmanns scenarie hvis man vil lave en æbletærte,
11:10
you just wait for the random motion of atoms
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venter man bare på, at atomernes tilfældige bevægelser
11:13
to make you an apple pie.
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laver en æbletærte til en.
11:15
That will happen much more frequently
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Det vil ske meget oftere,
11:17
than the random motions of atoms
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end at atomernes tilfældige bevægelser
11:19
making you an apple orchard
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laver en æbleplantage til en
11:21
and some sugar and an oven,
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og så noget sukker og en ovn,
11:23
and then making you an apple pie.
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og så laver en æbletærte til en.
11:25
So this scenario makes predictions.
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Så dette scenario laver forudsigelser.
11:28
And the predictions are
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Og forudsigelserne er,
11:30
that the fluctuations that make us are minimal.
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at fluktuationerne, der laver os, er minimale.
11:33
Even if you imagine that this room we are in now
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Selv hvis man forestiller sig, dette rum, vi er i nu,
11:36
exists and is real and here we are,
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eksisterer og er virkeligt, og her er vi,
11:38
and we have, not only our memories,
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og vi har ikke bare vores minder,
11:40
but our impression that outside there's something
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men vores indtryk, at udenfor er der noget,
11:42
called Caltech and the United States and the Milky Way Galaxy,
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der hedder Caltech og USA og Mælkevejen,
11:46
it's much easier for all those impressions to randomly fluctuate into your brain
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er det meget lettere for alle disse indtryk tilfældigt at fluktuere inde i ens hjerne,
11:49
than for them actually to randomly fluctuate
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end at de rent faktisk tilfældigt fluktuerer
11:51
into Caltech, the United States and the galaxy.
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til Caltech, USA og galaksen.
11:54
The good news is that,
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De gode nyheder er, at
11:56
therefore, this scenario does not work; it is not right.
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derfor virker dette scenario ikke; det er ikke rigtigt.
11:59
This scenario predicts that we should be a minimal fluctuation.
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Dette scenario forudser, at vi skulle være en minimal fluktuation.
12:02
Even if you left our galaxy out,
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Selv hvis man fjernede vores galakse,
12:04
you would not get a hundred billion other galaxies.
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ville man ikke få hundrede milliarder andre galakser.
12:06
And Feynman also understood this.
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Og Feynman forstod også dette.
12:08
Feynman says, "From the hypothesis that the world is a fluctuation,
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Feynman siger, "Fra hypotesen, at verden er en fluktuation,
12:12
all the predictions are that
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er alle forudsigelserne, at
12:14
if we look at a part of the world we've never seen before,
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hvis vi ser på en del af verden, vi aldrig har set før,
12:16
we will find it mixed up, and not like the piece we've just looked at --
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vil vi se den som blandet, og ikke som delen vi lige så på --
12:18
high entropy.
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høj entropi.
12:20
If our order were due to a fluctuation,
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Hvis vores orden skyldtes en fluktuation,
12:22
we would not expect order anywhere but where we have just noticed it.
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ville vi ikke forvente orden nogen andre steder end der, vi lige har bemærket det.
12:24
We therefore conclude the universe is not a fluctuation."
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Vi konkluderer derfor, at universet ikke er en fluktuation."
12:28
So that's good. The question is then what is the right answer?
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Så det er godt. Spørgsmålet er så, hvad er det rigtige svar?
12:31
If the universe is not a fluctuation,
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Hvis universet ikke er en fluktuation,
12:33
why did the early universe have a low entropy?
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hvorfor havde det tidlige univers lav entropi?
12:36
And I would love to tell you the answer, but I'm running out of time.
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Og jeg ville elske at give jer svaret, men jeg er ved at løbe tør for tid.
12:39
(Laughter)
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(Latter)
12:41
Here is the universe that we tell you about,
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Her er universet, som vi fortæller jer om,
12:43
versus the universe that really exists.
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versus universet, der virkelig eksisterer.
12:45
I just showed you this picture.
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Jeg har lige vist jer dette billede.
12:47
The universe is expanding for the last 10 billion years or so.
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Universet har udvidet sig i de sidste 10 milliarder år sådan ca.
12:49
It's cooling off.
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Det køler af.
12:51
But we now know enough about the future of the universe
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Men vi ved nu nok om universets fremtid
12:53
to say a lot more.
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til at sige meget mere.
12:55
If the dark energy remains around,
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Hvis mørk energi fortsætter med at være tilstede,
12:57
the stars around us will use up their nuclear fuel, they will stop burning.
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vil stjernerne omkring os opbruge deres kernebrændsel, de vil stoppe med at brænde.
13:00
They will fall into black holes.
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De vil falde sammen til sorte huller.
13:02
We will live in a universe
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Vi vil leve i et univers
13:04
with nothing in it but black holes.
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med intet i sig ud over sorte huller.
13:06
That universe will last 10 to the 100 years --
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Det univers vil vare 10 opløftet i 100 år --
13:10
a lot longer than our little universe has lived.
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meget længere end vores lille univers har levet.
13:12
The future is much longer than the past.
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Fremtiden er meget længere end fortiden.
13:14
But even black holes don't last forever.
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Men selv sorte huller varer ikke evigt.
13:16
They will evaporate,
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De vil fordampe,
13:18
and we will be left with nothing but empty space.
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og vi vil blive tilbage med intet ud over tomt rum.
13:20
That empty space lasts essentially forever.
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Det tomme rum varer grundlæggende set evigt.
13:24
However, you notice, since empty space gives off radiation,
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Men I bemærker, eftersom tomt rum afgiver stråling,
13:27
there's actually thermal fluctuations,
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er der faktisk termiske fluktuationer,
13:29
and it cycles around
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og det kører i ring
13:31
all the different possible combinations
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alle de forskellige mulige kombinationer
13:33
of the degrees of freedom that exist in empty space.
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af grader af frihed, der eksisterer i tomt rum.
13:36
So even though the universe lasts forever,
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Så selvom universet varer evigt,
13:38
there's only a finite number of things
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er der kun et endeligt antal af ting,
13:40
that can possibly happen in the universe.
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der kan lade sig gøre i universet.
13:42
They all happen over a period of time
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De sker allesammen over en tidsperiode
13:44
equal to 10 to the 10 to the 120 years.
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på 10 opløftet i 120 år.
13:47
So here's two questions for you.
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Så her er to spørgsmål til jer.
13:49
Number one: If the universe lasts for 10 to the 10 to the 120 years,
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Nummer et: Hvis universet varer i 10 opløftet i 10 opløftet i 120 år,
13:52
why are we born
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hvorfor er vi født
13:54
in the first 14 billion years of it,
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i de første 14 milliarder år af den tid
13:57
in the warm, comfortable afterglow of the Big Bang?
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i Big Bangs varme, behagelige efterglød?
14:00
Why aren't we in empty space?
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Hvorfor lever vi ikke i tomt rum?
14:02
You might say, "Well there's nothing there to be living,"
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I kunne sige, "Jamen, der er ingenting til at leve,"
14:04
but that's not right.
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men det er ikke rigtigt.
14:06
You could be a random fluctuation out of the nothingness.
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I kunne være en tilfældig fluktuation ud af intetheden.
14:08
Why aren't you?
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Hvorfor er I ikke?
14:10
More homework assignment for you.
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Mere hjemmearbejde til jer.
14:13
So like I said, I don't actually know the answer.
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Så som jeg sagde, kender jeg faktisk ikke svaret.
14:15
I'm going to give you my favorite scenario.
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Jeg vil give jer mit yndlingsscenario.
14:17
Either it's just like that. There is no explanation.
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Enten er det bare sådan. Der er ingen forklaring.
14:20
This is a brute fact about the universe
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Dette er et hårdt faktum om universet,
14:22
that you should learn to accept and stop asking questions.
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som man bør lære at acceptere og stoppe med at stille spørgsmål.
14:26
Or maybe the Big Bang
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Eller måske er Big Bang
14:28
is not the beginning of the universe.
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ikke universets begyndelse.
14:30
An egg, an unbroken egg, is a low entropy configuration,
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Et æg, et ubrudt æg, er en konfiguration med lav entropi,
14:33
and yet, when we open our refrigerator,
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og når vi alligevel åbner vores køleskab,
14:35
we do not go, "Hah, how surprising to find
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siger vi ikke, "Hah, hvor overraskende at finde
14:37
this low entropy configuration in our refrigerator."
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denne konfiguration med lav entropi i vores køleskab."
14:39
That's because an egg is not a closed system;
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Det er fordi et æg ikke er et lukket system;
14:42
it comes out of a chicken.
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det kommer fra en høne.
14:44
Maybe the universe comes out of a universal chicken.
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Måske kommer universet fra en universal høne.
14:48
Maybe there is something that naturally,
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Måske er der noget, der helt naturligt,
14:50
through the growth of the laws of physics,
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ved vækst fra fysikkens love,
14:53
gives rise to universe like ours
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giver anledning til et univers som vores
14:55
in low entropy configurations.
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med konfigurationer med lav entropi.
14:57
If that's true, it would happen more than once;
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Hvis det er sandt, ville det ske mere end én gang;
14:59
we would be part of a much bigger multiverse.
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vi ville være del af et meget større multivers.
15:02
That's my favorite scenario.
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Det er mit yndlingsscenario.
15:04
So the organizers asked me to end with a bold speculation.
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Så arrangørerne bad mig om at slutte med en dristig spekulation.
15:07
My bold speculation
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Min dristige spekulation
15:09
is that I will be absolutely vindicated by history.
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er, at jeg bliver fuldstændigt bekræftet engang.
15:12
And 50 years from now,
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Og om 50 år fra nu
15:14
all of my current wild ideas will be accepted as truths
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bliver alle mine lige nu vilde idéer accepteret som sandheder
15:17
by the scientific and external communities.
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af de videnskabelige og eksterne samfund.
15:20
We will all believe that our little universe
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Vi vil alle tro på, at vores lille univers
15:22
is just a small part of a much larger multiverse.
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bare er en lille del af et meget større multivers.
15:25
And even better, we will understand what happened at the Big Bang
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Og endnu bedre vil vi forstå det, der skete ved Big Bang
15:28
in terms of a theory
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med en teori,
15:30
that we will be able to compare to observations.
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som vi vil være i stand til at sammenligne med observationer.
15:32
This is a prediction. I might be wrong.
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Dette er en forudsigelse. Jeg kunne tage fejl.
15:34
But we've been thinking as a human race
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Men vi har tænkt som menneskerace
15:36
about what the universe was like,
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over, hvordan universet var,
15:38
why it came to be in the way it did for many, many years.
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hvorfor det blev på den måde, det blev i mange, mange år.
15:41
It's exciting to think we may finally know the answer someday.
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Det er spændende at tænke på, vi måske endelig kommer til at kende svaret engang.
15:44
Thank you.
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Tak.
15:46
(Applause)
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(Bifald)
ABOUT THE SPEAKER
Sean M. Carroll - Physicist, cosmologistA physicist, cosmologist and gifted science communicator, Sean Carroll is asking himself -- and asking us to consider -- questions that get at the fundamental nature of the universe.
Why you should listen
Sean Carroll is a theoretical physicist at Caltech in Pasadena, California, where he researches theoretical aspects of cosmology, field theory and gravitation -- exploring the nature of fundamental physics by studying the structure and evolution of the universe.
His book on cosmology and the arrow of time, From Eternity to Here: The Quest for the Ultimate Theory of Time, was published in 2010. He keeps a regular blog at Cosmic Variance.
Sean M. Carroll | Speaker | TED.com