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Eternity.
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It's an idea as old as religion.
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Perhaps as old as humankind.
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But what can modern science
tell us about the end of time?
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Will the Universe end
in a cosmic apocalypse?
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Could time keep on
ticking forever...
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Or will eternity end?
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Space, time, life itself.
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The secrets of the cosmos
lie through the wormhole.
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♪ Through the Wormhole 03x09 ♪
Will Eternity End ?
Original Air Date on August 1, 2012
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== sync, corrected by elderman ==
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The Apocalypse.
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It's the day when Muslims,
Christians, and Jews
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believe the world will come
crashing down around us.
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Physicists now have their own
version of Apocalypse.
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In fact,
they have several of them.
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The sun will engulf the earth.
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Our star will fall
into a black hole.
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Our entire galaxy will collide
with another.
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But what if everything
came to an end?
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Destroyed in an Apocalypse
so complete
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that time itself
would disappear.
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I was just a young boy when time
ran out for my grandmother.
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The sun continued to rise
and set each day.
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The seasons cycled on.
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I wondered if time for my
grandmother really had ended,
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time when the Universe
carried on.
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In fact, it seemed impossible
that time itself could ever end.
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The ancient Greeks and Egyptians
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thought of eternity
as a place outside of time.
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They saw time as a giant circle,
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mirroring the passing
of the sun overhead
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and the rotation of the seasons.
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But today, we have rolled out
the circle of time into a line
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stretching from the distant past
to the far future.
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Now we are forced to contemplate
whether this timeline has an end
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or whether it can
stretch on forever.
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But perhaps the riddle
of eternity
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is something we've created
in our heads.
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Anthropologist
Vera da Silva Sinha
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00:03:11,474 --> 00:03:15,042
and linguistic psychologist
Chris Sinha
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spend their time thinking about
how people think about time.
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We have very large-scale,
complex societies.
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We could not make our society
take over
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if we didn't have a calendar
and a clock.
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So we think of time concepts
and ways of measuring time
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as being what we call
a "cognitive technology."
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It's a technology of the mind.
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But Chris and Vera
have discovered
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this organized view of time
is not universal.
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It's an insight they gained
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from studying the language
and culture
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of an indigenous Amazonian tribe
called the Amondawa.
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The Amondawa people
live in Rondonia --
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the state of Brazil.
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They were contacted
by the Brazilian government
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in 1984.
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The Amondawa tribe
does not live by a calendar,
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and they don't use clocks.
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In fact, there isn't even a word
for time in their language.
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If you ask
an Amondawa speaker
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to give a translation
of the word "time,"
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the nearest thing
that they can think of --
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they will say "Sun."
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Or they say
"raining season,"
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or they say "summertime,"
but there is no...
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There's nothing which is
abstracted from that, right?
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To try and understand
the Amondawa's notion of time,
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Chris and Vera had them arrange
a series of paper plates.
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So, we found out
there is two seasons, yeah?
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Rain season
and dry season.
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So, and they would use
the plates
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to symbolize how these seasons
are divided.
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An Amondawa man
organizes the plates
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not according to days or months
but by the natural events
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that occur throughout
their two seasons.
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For each one of these small
subdivisions of a season,
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he'll tell a little story
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about what kind of planting
and harvesting goes on,
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also what fruits
are ripening
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and what's going on in
the forest and in the rivers.
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Is their level of the river
going up or going down?
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This kind of thing.
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Yeah. Yeah.
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It's a way of mapping out time
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that would make sense
to any farmer.
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But in our industrialized
cultures,
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a much more rigid system
has taken over.
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We might arrange plates
in a line of seven --
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one plate for each day
of the week.
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00:05:53,069 --> 00:05:58,239
Or we would divide a day
into hours arranged in a circle.
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But the Amondawa don't arrange
events in any particular shape.
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He's not really worried
about the shape of the events.
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He worry about the contents
of each event.
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They don't think of time
as being analogous
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to a spacial dimension.
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They don't think of time
being a sort of line
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in which there is a future
that you look forward to
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and a past
that you look back to.
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00:06:25,501 --> 00:06:28,736
In English, you can say, "Oh,
I look back to my childhood."
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However, in Amondawa, you don't
look back to your childhood.
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So, in your childhood,
you were there,
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so you don't look
back anymore.
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So
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The Amondawa
don't look back on a line
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that traces their life
from past to present.
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But in Western cultures,
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we can't help but impose
this time geometry on our lives.
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A person's life is like a line
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that stretches
from birth to death,
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and so we imagine
the Universe, too,
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must have a timeline --
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from its birth in the Big Bang,
14 billion years ago
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to some far future date
when it will die.
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There was no time
before the beginning,
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and time will
eventually disappear
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when the Universe meets
its apocalyptic end.
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Theoretical physicist
Fotini Markopoulou,
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like the Amondawa,
rejects this idea.
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Well, if you are to say
that time will end,
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you also have to say
that time began.
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It's like death and birth.
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You really can't have deaths
and no births.
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So now you have to tell me
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where time came from
if there was no time.
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Fotini is trying
to understand
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the fundamental nature of time,
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which in the microscopic world
of subatomic particles
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becomes a tricky concept.
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00:07:58,027 --> 00:08:00,728
The theory of
Quantum Mechanics says
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00:08:00,730 --> 00:08:02,763
that particles don't interact
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as if they are solid,
defined objects,
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but as amorphous clouds.
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A particle can be both there
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and not there at the same time.
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And it's impossible to say
when two particles meet
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or whether they did at all.
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00:08:19,982 --> 00:08:23,818
If you try to apply the laws
of Quantum Mechanics
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00:08:23,820 --> 00:08:27,087
to large objects like people
or planets,
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00:08:27,089 --> 00:08:31,692
you can imagine some
very puzzling possibilities.
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I'm sitting here,
and I'm talking to you.
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Now, if by some accident,
in our Universe,
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there was a huge black hole
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that would suck me inside
the black hole,
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according to Quantum Theory,
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that black hole behind me
should be there and not there.
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And, as a result, you are in
a position of our conversation
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having happened or not happened.
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Many Quantum
physicists argue
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this uncertainty over whether
the events really happened
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00:09:00,790 --> 00:09:03,858
shows that time cannot be
a fundamental thing
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00:09:03,860 --> 00:09:05,059
in the Universe.
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00:09:05,061 --> 00:09:06,994
It's something we've made up.
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00:09:06,996 --> 00:09:10,965
Albert Einstein disagreed
with Quantum Mechanics.
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He believed time is real,
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00:09:13,002 --> 00:09:17,705
that it is woven with space
into the fabric of the Universe.
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And, according to his disciples,
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space and time were born
together in the Big Bang.
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But Fotini thinks both
these views of time are wrong.
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She thinks that time is real
and eternal.
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00:09:33,756 --> 00:09:35,823
But for that to be true,
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we have to reimagine
what space is.
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Okay, so let's say
that this is space --
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the world we live in --
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and the little red strings
are other stuff in our world.
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And the net represents
the distances between us
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in terms of connectivity.
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So that means that,
for instance,
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if we say that this is me
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and this is my friend Oralia
and that's my fried Helmut,
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it takes me --
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one, two, three, four, five,
six steps to get to Oralia.
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00:10:06,055 --> 00:10:09,356
And then I need -- 1, 2, 3, 4,
5, 6, 7, 8, 9, 10,
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00:10:09,358 --> 00:10:13,227
11, 12, 13, 14, 15 steps
to reach Helmut.
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But right after the Big Bang,
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the net of space was not
spread out like this.
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00:10:20,169 --> 00:10:22,836
Perhaps, me here...
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was actually just
one step away from Helmut
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00:10:28,544 --> 00:10:30,110
back in the early Universe,
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00:10:30,112 --> 00:10:34,415
and these two guys
were connected,
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until everybody is really
on top of everybody else.
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In the very hot
and dense Big Bang,
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everything is shrunk down
to a single point.
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The idea of space
is meaningless.
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00:10:49,198 --> 00:10:54,201
But time, Fotini is certain,
always exists.
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00:10:54,203 --> 00:10:57,104
If we throw out space,
we get to keep time.
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00:10:57,106 --> 00:11:00,908
Time was always there before.
It will always be there after.
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00:11:02,577 --> 00:11:05,245
If Fotini is right,
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time can indeed tick on forever.
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00:11:07,883 --> 00:11:12,853
But one scientist is deeply
troubled by an eternal Universe.
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00:11:12,855 --> 00:11:16,090
Because if time
never stops ticking,
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00:11:16,092 --> 00:11:20,761
our very existence
could make no sense at all.
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00:11:22,011 --> 00:11:23,978
Eternity.
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00:11:24,502 --> 00:11:28,905
It used to be a word
that only made sense in religion
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00:11:28,907 --> 00:11:30,740
or to people in love.
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00:11:30,742 --> 00:11:35,979
Now some scientists also believe
time really may last forever.
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00:11:35,981 --> 00:11:38,715
But if eternity does exist,
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00:11:38,717 --> 00:11:42,785
some very strange things...
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00:11:42,787 --> 00:11:44,454
could happen.
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00:11:52,029 --> 00:11:54,297
Cosmologist Sean Carroll
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00:11:54,299 --> 00:11:57,467
from the California Institute
of Technology,
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00:11:57,469 --> 00:12:00,870
often takes a drive into
the mountains above Los Angeles
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00:12:00,872 --> 00:12:04,040
to get a better look
at the night sky.
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00:12:04,042 --> 00:12:05,508
And when he does,
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00:12:05,510 --> 00:12:09,812
he can't help but wonder what
that night sky will look like
206
00:12:09,814 --> 00:12:11,881
trillions of years from now.
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00:12:12,130 --> 00:12:16,266
Right now, we live in
a bright, comfortable Universe
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00:12:16,268 --> 00:12:20,069
with stars shining 100 billion
galaxies in the Universe
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00:12:20,071 --> 00:12:22,906
with 100 billion stars
in every galaxy.
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00:12:22,908 --> 00:12:25,141
But those stars
can't shine forever.
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00:12:25,143 --> 00:12:27,911
They burn up fuel.
They have a finite lifetime.
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00:12:27,913 --> 00:12:30,280
So, about 10 to the 15 years
from now,
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00:12:30,282 --> 00:12:32,515
those stars
will all have burnt out.
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00:12:32,517 --> 00:12:35,184
There'll be no more stars
shining in the sky.
215
00:12:35,186 --> 00:12:38,254
A million billion years
from now,
216
00:12:38,256 --> 00:12:42,058
the only celestial object
remaining will be black holes.
217
00:12:42,060 --> 00:12:44,694
You might think,
okay, now we're done.
218
00:12:44,696 --> 00:12:46,262
Black holes and empty space.
219
00:12:46,264 --> 00:12:48,031
But those black holes evaporate.
220
00:12:48,033 --> 00:12:49,399
They give off radiation,
221
00:12:49,401 --> 00:12:51,668
and the black hole itself
shrinks away.
222
00:12:51,670 --> 00:12:54,504
So it will take a long time,
but once that happens,
223
00:12:54,506 --> 00:12:57,373
there's nothing left
but a thin gruel of particles.
224
00:12:57,375 --> 00:12:59,909
And then we're faced
with the question,
225
00:12:59,911 --> 00:13:03,346
well, what happens in that
infinitely long future period
226
00:13:03,348 --> 00:13:05,581
after everything has
emptied out?
227
00:13:05,583 --> 00:13:07,917
What is life like
in empty space?
228
00:13:07,919 --> 00:13:14,090
It turns out that empty
space is not truly empty.
229
00:13:14,092 --> 00:13:16,259
In 1998,
230
00:13:16,261 --> 00:13:19,963
astronomers discovered
a strange cosmic force
231
00:13:19,965 --> 00:13:21,731
called "dark energy,"
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00:13:21,733 --> 00:13:27,270
an expansive pressure
existing everywhere in space.
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00:13:27,272 --> 00:13:30,506
Even an empty universe,
in the far future,
234
00:13:30,508 --> 00:13:33,242
would be filled
with this energy.
235
00:13:33,244 --> 00:13:36,245
And the laws of
Quantum Mechanics say,
236
00:13:36,247 --> 00:13:38,181
wherever there is energy,
237
00:13:38,183 --> 00:13:42,251
particles can spontaneously
appear out of nothingness.
238
00:13:44,021 --> 00:13:47,190
Because that dark energy
is lurking in empty space,
239
00:13:47,192 --> 00:13:48,624
there's a temperature.
240
00:13:48,626 --> 00:13:51,794
The future of the Universe
is not at absolute zero.
241
00:13:51,796 --> 00:13:54,097
There's a tiny
thermal fluctuation,
242
00:13:54,099 --> 00:13:55,465
even in empty space.
243
00:13:55,467 --> 00:13:59,135
If we imagine this oven
represents the whole universe,
244
00:13:59,137 --> 00:14:02,071
we can look inside
and see things appear.
245
00:14:02,073 --> 00:14:06,142
So if we wait a long time,
about 10 to the 10 years --
246
00:14:06,144 --> 00:14:07,677
10 billion years --
247
00:14:07,679 --> 00:14:10,380
we'll see a single,
lonely photon
248
00:14:10,382 --> 00:14:13,082
propagating
through the Universe.
249
00:14:13,084 --> 00:14:16,152
But give
the Universe more time,
250
00:14:16,154 --> 00:14:18,054
and more particles appear.
251
00:14:18,056 --> 00:14:23,726
Eventually, after 10 to the
power 10 to the power 30 years,
252
00:14:23,728 --> 00:14:25,428
something as complex
and unlikely
253
00:14:25,430 --> 00:14:27,897
as a perfectly wired
human brain
254
00:14:27,899 --> 00:14:30,099
could simply pop into existence.
255
00:14:32,169 --> 00:14:34,670
And if you wait even longer
than that,
256
00:14:34,672 --> 00:14:38,074
10 to the 10 to the 120 years,
257
00:14:38,076 --> 00:14:41,244
we'll see an entire
new Big Bang,
258
00:14:41,246 --> 00:14:44,113
an entire universe
fluctuating into existence
259
00:14:44,115 --> 00:14:45,915
out of the surrounding chaos.
260
00:14:45,917 --> 00:14:47,116
For Sean,
261
00:14:47,118 --> 00:14:49,919
these random fluctuations
present a big problem.
262
00:14:49,921 --> 00:14:52,388
If the Universe lasts forever,
263
00:14:52,390 --> 00:14:54,590
an infinite amount of time
264
00:14:54,592 --> 00:14:58,161
means an infinite amount
of possibilities,
265
00:14:58,163 --> 00:15:02,231
which means everything you could
possibly imagine
266
00:15:02,233 --> 00:15:04,067
will indeed appear --
267
00:15:04,069 --> 00:15:06,602
including
another version of you,
268
00:15:06,604 --> 00:15:08,671
who thinks he got here first.
269
00:15:08,673 --> 00:15:12,141
Many, many copies of me
will fluctuate into existence,
270
00:15:12,143 --> 00:15:15,711
many of them with exactly
the same memories that I have.
271
00:15:15,713 --> 00:15:19,715
There will be another version of
me that thinks the same as I do
272
00:15:19,717 --> 00:15:22,685
and has the same set of memories
that I have.
273
00:15:22,687 --> 00:15:26,589
But for most of
those versions of me,
274
00:15:26,591 --> 00:15:29,292
they won't actually be embedded
in a sensible universe
275
00:15:29,294 --> 00:15:31,194
with a big bang
and other galaxies.
276
00:15:31,196 --> 00:15:33,863
Each one of these Seans
277
00:15:33,865 --> 00:15:37,500
assumes that he is the first
version of himself.
278
00:15:37,502 --> 00:15:40,903
They each think they grew up
in Pennsylvania,
279
00:15:40,905 --> 00:15:44,474
studied at Harvard,
and wrote books on physics.
280
00:15:44,476 --> 00:15:47,777
But they are really just
random fluctuations
281
00:15:47,779 --> 00:15:50,046
that have popped into existence,
282
00:15:50,048 --> 00:15:53,783
future imposters that
actually live in empty space.
283
00:15:55,486 --> 00:15:57,987
The scenario that the Universe
just lasts forever
284
00:15:57,989 --> 00:15:59,822
and there's all
these fluctuations
285
00:15:59,824 --> 00:16:01,791
into everything we can
possibly imagine
286
00:16:01,793 --> 00:16:04,894
means that we have no right to
accept and believe our memories.
287
00:16:04,896 --> 00:16:07,330
If people and galaxies
and universes
288
00:16:07,332 --> 00:16:09,866
can randomly fluctuate
into existence,
289
00:16:09,868 --> 00:16:12,301
the conclusion is
that this can't be
290
00:16:12,303 --> 00:16:14,637
the right picture
of the Universe.
291
00:16:16,740 --> 00:16:21,244
If dark energy
keeps on expanding our cosmos,
292
00:16:21,246 --> 00:16:25,381
countless versions of all of us
will eventually come to be,
293
00:16:25,383 --> 00:16:29,018
stretching from here
to eternity.
294
00:16:29,020 --> 00:16:31,020
There's only one thing
295
00:16:31,022 --> 00:16:35,291
that could prevent
such a preposterous universe...
296
00:16:35,293 --> 00:16:38,895
A truly cosmic apocalypse.
297
00:16:43,395 --> 00:16:48,099
What does the word
"Universe" mean?
298
00:16:48,101 --> 00:16:50,868
It used to mean "everything."
299
00:16:50,870 --> 00:16:56,040
But now some scientists imagine
there is more to creation
300
00:16:56,042 --> 00:17:01,279
than all the stars and galaxies
we could ever hope to see.
301
00:17:01,281 --> 00:17:06,517
We might be just one tiny patch
of something much larger,
302
00:17:06,519 --> 00:17:08,686
a multiverse,
303
00:17:08,688 --> 00:17:11,489
a place that lasts forever,
304
00:17:11,491 --> 00:17:15,526
and where a little Universe
like ours
305
00:17:15,528 --> 00:17:19,664
comes and goes in the blink
of an eye.
306
00:17:21,433 --> 00:17:26,404
Raphael Bousso is one of a new
generation of cosmologists
307
00:17:26,406 --> 00:17:31,142
who grew up with the idea
that our Universe may not be
308
00:17:31,144 --> 00:17:34,545
the be all and end all
of existence.
309
00:17:34,547 --> 00:17:39,450
For him, other universes pop
into existence all the time
310
00:17:39,452 --> 00:17:43,387
and exist inside
a colossal multiverse.
311
00:17:43,389 --> 00:17:46,924
The multiverse is made out
of many different regions.
312
00:17:46,926 --> 00:17:49,560
These individual regions
can be so large that,
313
00:17:49,562 --> 00:17:51,062
if you live in them,
314
00:17:51,064 --> 00:17:54,165
you're really like a fish in an
extremely large tank of water.
315
00:17:54,167 --> 00:17:57,201
You might think that there is
nothing else whatsoever.
316
00:17:57,203 --> 00:18:03,140
Imagine the Universe
we live in is like a balloon.
317
00:18:03,142 --> 00:18:04,775
In the beginning,
318
00:18:04,777 --> 00:18:08,546
it was just a miniscule piece
of compact space.
319
00:18:08,548 --> 00:18:09,980
At the Big Bang,
320
00:18:09,982 --> 00:18:13,517
a powerful force called
inflation took over,
321
00:18:13,519 --> 00:18:15,953
expanding it in a split second.
322
00:18:15,955 --> 00:18:18,222
14 billion years later,
323
00:18:18,224 --> 00:18:21,959
we all live deep inside
its inflated walls,
324
00:18:21,961 --> 00:18:24,061
blind to what's outside.
325
00:18:25,997 --> 00:18:29,600
But Raphael believes inflation
is still at work
326
00:18:29,602 --> 00:18:32,670
outside of our balloon.
327
00:18:32,672 --> 00:18:37,975
It constantly takes tiny pieces
of space and expands them.
328
00:18:37,977 --> 00:18:40,544
So, this room
is what we can think of
329
00:18:40,546 --> 00:18:42,580
as the multiverse looking like,
330
00:18:42,582 --> 00:18:48,619
where every one of these
balloons is a single universe,
331
00:18:48,621 --> 00:18:52,022
and all these universes are here
because of inflation.
332
00:18:52,024 --> 00:18:55,192
Raphael's understanding
of inflation
333
00:18:55,194 --> 00:18:58,796
stems from the view of reality
called "String theory,"
334
00:18:58,798 --> 00:19:02,700
which holds that there are not
three dimensions of space...
335
00:19:02,702 --> 00:19:05,603
but nine.
336
00:19:05,605 --> 00:19:07,304
In our Universe,
337
00:19:07,306 --> 00:19:12,977
six of the dimensions are curled
up billions of times smaller
338
00:19:12,979 --> 00:19:15,579
than the smallest particle.
339
00:19:15,581 --> 00:19:16,914
There might be some places
340
00:19:16,916 --> 00:19:19,316
where all nine spatial
dimensions have become large.
341
00:19:19,318 --> 00:19:20,584
There might be other places
342
00:19:20,586 --> 00:19:22,620
where fewer than three
have become large.
343
00:19:22,622 --> 00:19:28,058
So inflation stretches some,
but not necessarily all,
344
00:19:28,060 --> 00:19:29,693
of the dimensions of space.
345
00:19:29,695 --> 00:19:33,330
Just like an inflated balloon,
346
00:19:33,332 --> 00:19:35,800
inflated dimensions of space
347
00:19:35,802 --> 00:19:40,104
are intrinsically unstable
and will eventually...
348
00:19:40,106 --> 00:19:42,239
re-collapse.
349
00:19:42,241 --> 00:19:43,841
As I'm walking around this room,
350
00:19:43,843 --> 00:19:46,243
you can see that these balloons
are popping...
351
00:19:46,245 --> 00:19:48,813
ever so slowly,
one after the other.
352
00:19:48,815 --> 00:19:50,381
There are a lot of balloons,
353
00:19:50,383 --> 00:19:52,716
but if you train your eye
on one balloon,
354
00:19:52,718 --> 00:19:55,052
that balloon eventually
is going to pop.
355
00:19:55,054 --> 00:19:56,320
And just like that,
356
00:19:56,322 --> 00:19:58,856
our piece of space eventually
is going to decay.
357
00:19:58,858 --> 00:20:01,292
By studying how inflation
358
00:20:01,294 --> 00:20:04,094
mutates the curled-up dimensions
of space,
359
00:20:04,096 --> 00:20:06,464
Raphael has been able
to calculate
360
00:20:06,466 --> 00:20:09,533
that the rate of creation
of inflated universes
361
00:20:09,535 --> 00:20:12,236
is much higher
than their rate of decay.
362
00:20:12,238 --> 00:20:16,307
So, even though universes
are going...all the time,
363
00:20:16,309 --> 00:20:19,276
many more are always
being created.
364
00:20:19,278 --> 00:20:23,981
So the multiverse keeps on
growing and will last forever.
365
00:20:23,983 --> 00:20:27,618
This pattern is called
"eternal inflating multiverse."
366
00:20:27,620 --> 00:20:30,621
If you were watching this room
from the outside,
367
00:20:30,623 --> 00:20:32,022
time would be eternal.
368
00:20:32,024 --> 00:20:33,757
This would continue forever.
369
00:20:33,759 --> 00:20:37,061
This multiverse may be eternal,
370
00:20:37,063 --> 00:20:41,298
but it's an eternity no one
can ever hope to experience
371
00:20:41,300 --> 00:20:44,735
because no one can ever escape
the universe
372
00:20:44,737 --> 00:20:46,437
they were created in.
373
00:20:46,439 --> 00:20:48,405
You don't get the benefit
of seeing this eternity
374
00:20:48,407 --> 00:20:50,574
of more and more inflation
and more and more balloons.
375
00:20:50,576 --> 00:20:51,842
The speed-of-light limit
376
00:20:51,844 --> 00:20:54,512
prevents you from seeing
all these other balloons.
377
00:20:54,514 --> 00:20:56,380
You sit around
in this one balloon,
378
00:20:56,382 --> 00:20:58,449
and sooner or later
it's going to go "pop."
379
00:20:59,886 --> 00:21:03,687
If you live in a
universe, like everything must,
380
00:21:03,689 --> 00:21:08,626
then Raphael believes your time
is definitely going to end.
381
00:21:10,162 --> 00:21:13,731
And all of the problems
of an eternal universe
382
00:21:13,733 --> 00:21:15,666
that worry Sean Carroll
383
00:21:15,668 --> 00:21:19,436
are problems our Universe
will never live to see.
384
00:21:19,438 --> 00:21:23,274
We can calculate how rapidly
space will decay.
385
00:21:23,276 --> 00:21:26,343
As long as that decay of
our Universe happens faster
386
00:21:26,345 --> 00:21:29,813
than these unbelievably unlikely
events are going to happen,
387
00:21:29,815 --> 00:21:32,516
then we know that
we don't have to worry about
388
00:21:32,518 --> 00:21:34,885
copies of ourselves
coming into being.
389
00:21:34,887 --> 00:21:38,322
When our Universe decays,
time really does end there.
390
00:21:40,293 --> 00:21:45,696
Is our universe destined to die
in a cosmic cataclysm?
391
00:21:45,698 --> 00:21:48,132
Perhaps not.
392
00:21:48,134 --> 00:21:52,069
Because time may not be
what we think it is,
393
00:21:52,071 --> 00:21:56,631
and all of eternity
might already exist.
394
00:22:00,028 --> 00:22:03,931
Physicists tell us that time
is the fourth dimension.
395
00:22:05,131 --> 00:22:09,133
But it's not like the other
three that we move around in.
396
00:22:09,135 --> 00:22:10,868
In space,
397
00:22:10,870 --> 00:22:13,838
I could walk from here...
398
00:22:13,840 --> 00:22:16,140
to here...
399
00:22:16,142 --> 00:22:20,011
and then turn around
and go back again.
400
00:22:20,013 --> 00:22:23,281
Time's dimension
seems different.
401
00:22:23,283 --> 00:22:27,185
We only move through it
in one direction.
402
00:22:27,187 --> 00:22:31,522
But there may be a way to grasp
all of eternity
403
00:22:31,524 --> 00:22:35,827
if we stop thinking about
time as a dimension
404
00:22:35,829 --> 00:22:40,131
and start thinking about time
as a projection
405
00:22:40,133 --> 00:22:41,966
from the future...
406
00:22:41,968 --> 00:22:44,869
to the past.
407
00:22:47,606 --> 00:22:51,042
For Harvard
physicist Andy Strominger,
408
00:22:51,044 --> 00:22:53,511
the difference between
the future and the past
409
00:22:53,513 --> 00:22:55,246
is a deep puzzle.
410
00:22:55,248 --> 00:22:58,216
Because, according to
the known laws of physics,
411
00:22:58,218 --> 00:23:01,252
they should be exactly the same.
412
00:23:01,254 --> 00:23:04,055
There's a very basic principle
of physics
413
00:23:04,057 --> 00:23:05,656
which begin with Newton.
414
00:23:05,658 --> 00:23:08,459
The past determines the future,
415
00:23:08,461 --> 00:23:13,564
and the laws of physics can be
run forward or backwards.
416
00:23:13,566 --> 00:23:18,302
So, if I take this motion
of this pendulum
417
00:23:18,304 --> 00:23:20,204
hanging from the pencil
418
00:23:20,206 --> 00:23:24,408
and you run the movie forward
or backwards,
419
00:23:24,410 --> 00:23:26,577
it looks exactly the same.
420
00:23:28,280 --> 00:23:33,284
But there's a huge white
elephant in the room of physics,
421
00:23:33,286 --> 00:23:36,087
and that's the Big Bang.
422
00:23:36,089 --> 00:23:38,956
So, the cartoon picture
of the Big Bang
423
00:23:38,958 --> 00:23:40,792
is that there was nothing.
424
00:23:40,794 --> 00:23:42,627
Somebody flipped a switch,
425
00:23:42,629 --> 00:23:44,162
and, all of a sudden,
426
00:23:44,164 --> 00:23:47,398
all the something that
we know of was present.
427
00:23:47,400 --> 00:23:49,600
So, the past of our Universe
428
00:23:49,602 --> 00:23:54,238
and the future of our Universe
look fundamentally different.
429
00:23:55,941 --> 00:23:58,843
To resolve this paradox,
430
00:23:58,845 --> 00:24:02,346
Andy began to imagine
the dimension of time
431
00:24:02,348 --> 00:24:04,248
a radical new way --
432
00:24:04,250 --> 00:24:07,185
as a hologram.
433
00:24:07,187 --> 00:24:10,354
Holograms are
two-dimensional plates
434
00:24:10,356 --> 00:24:14,926
from which a third dimension
of space appears to emerge.
435
00:24:14,928 --> 00:24:18,095
Andy wondered if he could
apply this idea
436
00:24:18,097 --> 00:24:21,098
not to space but to time.
437
00:24:21,100 --> 00:24:26,470
Perhaps a dimension of time is
just a holographic projection.
438
00:24:26,472 --> 00:24:28,706
Time is a kind of illusion.
439
00:24:28,708 --> 00:24:32,210
And the whole universe
is written at a hologram
440
00:24:32,212 --> 00:24:35,246
that is sitting there
at the end of time
441
00:24:35,248 --> 00:24:39,217
and projected backwards
through our present era
442
00:24:39,219 --> 00:24:41,085
back to the Big Bang.
443
00:24:44,122 --> 00:24:48,593
The hologram that contains
everything the universe ever was
444
00:24:48,595 --> 00:24:52,797
and ever will be is like
this intricate ice crystal.
445
00:24:52,799 --> 00:24:54,432
According to Andy,
446
00:24:54,434 --> 00:24:56,534
it sits in the far future
447
00:24:56,536 --> 00:25:00,271
and projects information
back into the past.
448
00:25:00,273 --> 00:25:05,643
So, this sculpture represents
the holographic plate,
449
00:25:05,645 --> 00:25:07,511
which contains all
the information
450
00:25:07,513 --> 00:25:09,714
about the entire lifetime
of the Universe.
451
00:25:09,716 --> 00:25:14,919
As I look at this very closely,
I can see more and more detail.
452
00:25:14,921 --> 00:25:18,055
From far away,
or more accurately,
453
00:25:18,057 --> 00:25:20,358
from further back in time,
454
00:25:20,360 --> 00:25:23,661
there would be
less and less detail,
455
00:25:23,663 --> 00:25:28,532
less and less information
present in the universe itself.
456
00:25:28,534 --> 00:25:32,403
The further you get
from a holographic plate,
457
00:25:32,405 --> 00:25:35,206
the less information
you can read on it.
458
00:25:35,208 --> 00:25:38,976
So, as we travel back in time
from our present day,
459
00:25:38,978 --> 00:25:43,214
in a highly complex universe
of planets, stars, and galaxies,
460
00:25:43,216 --> 00:25:45,416
we move to a simpler past,
461
00:25:45,418 --> 00:25:49,687
to a universe the way it was
billions of years ago,
462
00:25:49,689 --> 00:25:53,457
filled with nothing more
than clouds of gas.
463
00:25:53,459 --> 00:25:55,426
And, eventually,
464
00:25:55,428 --> 00:25:57,762
if you go far enough
back in time,
465
00:25:57,764 --> 00:25:59,497
before the Big Bang,
466
00:25:59,499 --> 00:26:02,667
there is simply nothing there
at all.
467
00:26:02,669 --> 00:26:06,203
Holographic time
is the only theory
468
00:26:06,205 --> 00:26:10,708
that logically explains how
our Universe began from nothing.
469
00:26:10,710 --> 00:26:15,212
Once you get too far back in
time from the holographic plate,
470
00:26:15,214 --> 00:26:18,582
it cannot project back
any more information.
471
00:26:18,584 --> 00:26:23,054
Before the Big Bang, there is
no information in the universe.
472
00:26:23,056 --> 00:26:26,490
In a holographically-emergent
universe,
473
00:26:26,492 --> 00:26:28,693
we don't have a Big Bang.
474
00:26:28,695 --> 00:26:32,296
There isn't a special moment
when, all at once,
475
00:26:32,298 --> 00:26:35,132
everything in the universe
came into being.
476
00:26:35,134 --> 00:26:38,903
Rather, we have
an ongoing continual bang,
477
00:26:38,905 --> 00:26:40,871
which started from nothing
478
00:26:40,873 --> 00:26:44,342
and kept banging and banging
onto the future.
479
00:26:44,344 --> 00:26:46,377
In the past, there was nothing.
480
00:26:46,379 --> 00:26:48,879
In the future,
there is everything.
481
00:26:48,881 --> 00:26:52,450
The mathematics
behind Andy's theory
482
00:26:52,452 --> 00:26:54,018
are highly complex.
483
00:26:54,020 --> 00:26:58,389
Holographic time is not laid out
like any normal dimension.
484
00:26:58,391 --> 00:27:01,926
As you go further and further
into the future,
485
00:27:01,928 --> 00:27:06,564
the same increment of time moves
you less and less far forward.
486
00:27:06,566 --> 00:27:10,001
So it would take an infinite
amount of time
487
00:27:10,003 --> 00:27:13,471
to actually arrive
at the holographic plate.
488
00:27:13,473 --> 00:27:15,673
In this picture,
489
00:27:15,675 --> 00:27:19,176
our Universe goes on forever
into the future
490
00:27:19,178 --> 00:27:21,245
and gets bigger and bigger
491
00:27:21,247 --> 00:27:24,749
and keeps growing
and creating new elements.
492
00:27:24,751 --> 00:27:29,220
So we don't know that
it describes our universe.
493
00:27:29,222 --> 00:27:31,522
We're very far from that.
494
00:27:31,524 --> 00:27:36,861
But we do know that it is
something which can be discussed
495
00:27:36,863 --> 00:27:41,499
with some mathematical precision
and consistency.
496
00:27:41,501 --> 00:27:44,268
And so that's a starting point.
497
00:27:46,838 --> 00:27:51,008
Will our Universe
survive for an eternity?
498
00:27:51,010 --> 00:27:53,110
It depends on who you ask.
499
00:27:53,112 --> 00:27:56,147
Some say time
will go on forever.
500
00:27:56,149 --> 00:27:58,549
Others are sure it must end.
501
00:27:58,551 --> 00:28:01,218
But now another physicist thinks
502
00:28:01,220 --> 00:28:04,755
we might be able to decide
who is right,
503
00:28:04,757 --> 00:28:07,224
because the future
of the universe
504
00:28:07,226 --> 00:28:11,495
may be traveling back in time
to meet us.
505
00:28:13,831 --> 00:28:17,867
Is all eternity
already out there?
506
00:28:18,151 --> 00:28:22,620
Could the present and the past
be echoes of the future,
507
00:28:22,622 --> 00:28:24,522
rippling back in time?
508
00:28:24,524 --> 00:28:26,224
If that's the case,
509
00:28:26,226 --> 00:28:30,562
why is it you don't know
what I'm going to say next?
510
00:28:30,564 --> 00:28:31,629
The fact is,
511
00:28:31,631 --> 00:28:34,632
scientists think
they found evidence
512
00:28:34,634 --> 00:28:38,036
the future really does affect
the present.
513
00:28:38,038 --> 00:28:41,606
And knowledge about the fate
of the Universe
514
00:28:41,608 --> 00:28:44,609
may already be
right in front of us.
515
00:28:47,346 --> 00:28:51,883
Physicist Jeff Tollaksen
from Chapman University
516
00:28:51,885 --> 00:28:57,055
thinks the future is very much
connected to the present.
517
00:28:57,057 --> 00:29:02,193
The notions of time, eternity,
the end of time --
518
00:29:02,195 --> 00:29:05,763
these are some of the most
profound questions
519
00:29:05,765 --> 00:29:08,600
that we deal with
as human beings.
520
00:29:08,602 --> 00:29:10,702
But you have to listen
very carefully
521
00:29:10,704 --> 00:29:12,737
to what nature's
trying to tell you
522
00:29:12,739 --> 00:29:14,339
to discover fundamental truth.
523
00:29:17,343 --> 00:29:20,078
Jeff believes most physicists
524
00:29:20,080 --> 00:29:23,414
have failed to fully understand
the nature of time
525
00:29:23,416 --> 00:29:26,317
because of the way they insist
on doing experiments --
526
00:29:26,319 --> 00:29:30,321
smashing particles together
in giant accelerators.
527
00:29:30,323 --> 00:29:34,025
Maybe, instead of smashing
particles to bits,
528
00:29:34,027 --> 00:29:37,362
we just need to give them
a little push.
529
00:29:39,698 --> 00:29:45,937
What if more physicists took up
the gentle sport of curling?
530
00:29:45,939 --> 00:29:47,739
As you can see
531
00:29:47,741 --> 00:29:50,241
what our athletes
are doing here,
532
00:29:50,243 --> 00:29:53,911
they set the stone going
and they sweep a little bit
533
00:29:53,913 --> 00:29:56,514
to try to direct the stone
going somewhere.
534
00:29:56,516 --> 00:29:57,982
In a sense,
535
00:29:57,984 --> 00:30:01,052
this sweeping is kind of like
a very gentle interaction.
536
00:30:01,054 --> 00:30:03,421
You're not actually
touching the stone.
537
00:30:03,423 --> 00:30:06,391
You're kind of making the ice
a little bit smoother
538
00:30:06,393 --> 00:30:07,792
or melting a little bit
539
00:30:07,794 --> 00:30:11,329
so it would tend to go
in one direction.
540
00:30:11,331 --> 00:30:15,366
Jeff believes
you can understand everything
541
00:30:15,368 --> 00:30:18,336
about the way time really works
in the universe
542
00:30:18,338 --> 00:30:20,305
by watching curling.
543
00:30:20,307 --> 00:30:22,907
And you can begin
at the beginning,
544
00:30:22,909 --> 00:30:26,544
with the idea of time
Isaac Newton had.
545
00:30:26,546 --> 00:30:28,546
So, the stone starts
546
00:30:28,548 --> 00:30:30,415
from some definite place
in the past,
547
00:30:30,417 --> 00:30:33,351
it goes to some definite place
in the present,
548
00:30:33,353 --> 00:30:35,953
and it goes to a definite place
in the future.
549
00:30:35,955 --> 00:30:39,257
So, from that perspective
of classical physics,
550
00:30:39,259 --> 00:30:41,826
the universe looks like
it's a big machine,
551
00:30:41,828 --> 00:30:45,663
like a big,
very perfectly tuned clock.
552
00:30:45,665 --> 00:30:48,800
But then,
about a century ago,
553
00:30:48,802 --> 00:30:51,002
along came Quantum Mechanics.
554
00:30:51,004 --> 00:30:54,138
It took away all that certainty
from the universe
555
00:30:54,140 --> 00:30:57,342
by unmasking
the subatomic world.
556
00:30:57,344 --> 00:31:00,144
If these curling stones
were atoms,
557
00:31:00,146 --> 00:31:03,748
the rules of the game
would change dramatically.
558
00:31:03,750 --> 00:31:07,285
So, the quantum world
is different.
559
00:31:07,287 --> 00:31:08,953
It makes different predictions
560
00:31:08,955 --> 00:31:11,022
from the classical view
of things.
561
00:31:11,024 --> 00:31:12,724
In Quantum Mechanics,
562
00:31:12,726 --> 00:31:15,727
you could start these stones
the same
563
00:31:15,729 --> 00:31:20,231
and you notice that, incredibly,
one stone goes to the left
564
00:31:20,233 --> 00:31:23,334
and the other stone
goes to the right.
565
00:31:23,336 --> 00:31:26,504
In the microscopic
world of atoms,
566
00:31:26,506 --> 00:31:28,339
nothing is known for sure.
567
00:31:28,341 --> 00:31:31,075
Atoms are not solid,
defined objects.
568
00:31:31,077 --> 00:31:35,313
They are waves of probabilities
that tell you where,
569
00:31:35,315 --> 00:31:40,151
when you look for a particle,
you are most likely to find it.
570
00:31:40,153 --> 00:31:45,456
But in the 1960s,
quantum guru Yakir Aharonov
571
00:31:45,458 --> 00:31:49,260
dared to ask why atoms
are so unpredictable,
572
00:31:49,262 --> 00:31:51,629
why it's so hard to pin down
573
00:31:51,631 --> 00:31:55,099
what they're doing
at any given moment.
574
00:31:55,101 --> 00:31:57,235
And the answer, he discovered,
575
00:31:57,237 --> 00:32:01,105
was because the future
and the past are both involved
576
00:32:01,107 --> 00:32:03,141
in creating the present.
577
00:32:03,143 --> 00:32:09,313
Yakir showed that he could
reformulate Quantum Mechanics
578
00:32:09,315 --> 00:32:11,883
in a way that dealt
with the past
579
00:32:11,885 --> 00:32:14,852
and the future
on exactly equal footing.
580
00:32:14,854 --> 00:32:18,689
Future information, which is
impossible to know now,
581
00:32:18,691 --> 00:32:20,024
in principle,
582
00:32:20,026 --> 00:32:23,327
maybe that's already relevant
to the present moment.
583
00:32:23,329 --> 00:32:27,432
Jeff and Yakir
have searched for evidence
584
00:32:27,434 --> 00:32:31,602
of this revolutionary idea
for the past two decades.
585
00:32:31,604 --> 00:32:35,673
They've learned to be very
gentle in their measurements.
586
00:32:35,675 --> 00:32:38,943
A subatomic particle
will move or disappear
587
00:32:38,945 --> 00:32:40,912
if it's observed directly.
588
00:32:40,914 --> 00:32:44,482
It's as if they have to put
a particle in a box,
589
00:32:44,484 --> 00:32:48,119
not look at it, and allow it
to carry on existing
590
00:32:48,121 --> 00:32:51,255
as they spread out
a wave of probability.
591
00:32:51,257 --> 00:32:52,690
When they do that,
592
00:32:52,692 --> 00:32:57,161
they can begin to see the effect
of the future on the present.
593
00:32:57,163 --> 00:33:00,631
So, we have the red boxes
that are going forward in time.
594
00:33:00,633 --> 00:33:06,404
And now you have to think about
the backward evolving state.
595
00:33:06,406 --> 00:33:10,341
So we're gonna represent that
by blue boxes.
596
00:33:10,343 --> 00:33:12,844
Same particle, right?
We have one particle.
597
00:33:12,846 --> 00:33:15,847
But coming from the future,
we're saying the present
598
00:33:15,849 --> 00:33:17,982
is created out of a combination
599
00:33:17,984 --> 00:33:21,519
of the forward evolving
and the backward evolving.
600
00:33:23,755 --> 00:33:26,324
As radical as it sounds,
601
00:33:26,326 --> 00:33:28,826
Jeff, Yakir,
and their colleagues
602
00:33:28,828 --> 00:33:31,596
have now tested this idea
in the lab.
603
00:33:31,598 --> 00:33:35,766
They give a series of
very gentle magnetic nudges
604
00:33:35,768 --> 00:33:37,802
to subatomic particles.
605
00:33:37,804 --> 00:33:41,372
They measure them at 2:00...
606
00:33:41,374 --> 00:33:43,674
and then at 2:30.
607
00:33:43,676 --> 00:33:47,712
They do this
over and over again.
608
00:33:47,714 --> 00:33:50,781
Some but not all
of the particles
609
00:33:50,783 --> 00:33:53,451
are also measured again at 3:00.
610
00:33:53,453 --> 00:33:58,456
And what they found is that
taking their measurement at 3:00
611
00:33:58,458 --> 00:34:01,759
seemed to influence
the apparently random readings
612
00:34:01,761 --> 00:34:04,362
they got at 2:30.
613
00:34:04,364 --> 00:34:07,965
The future seemed to affect
the present,
614
00:34:07,967 --> 00:34:11,202
even though
it hadn't happened yet.
615
00:34:11,204 --> 00:34:13,304
If you're trying to
understand the present moment,
616
00:34:13,306 --> 00:34:16,440
the past is relevant,
as we knew before,
617
00:34:16,442 --> 00:34:20,144
but the future is just
as relevant to the present
618
00:34:20,146 --> 00:34:21,245
as the past.
619
00:34:21,247 --> 00:34:22,513
So far,
620
00:34:22,515 --> 00:34:25,583
these experiments have only
been carried out
621
00:34:25,585 --> 00:34:27,318
on the microscopic level,
622
00:34:27,320 --> 00:34:31,389
and the effects of the future
on the present are very subtle.
623
00:34:31,391 --> 00:34:35,059
But to Jeff, it suggests
that buried somewhere
624
00:34:35,061 --> 00:34:38,329
in the apparently random motion
of all the particles
625
00:34:38,331 --> 00:34:43,501
in the Universe there is
such a thing as cosmic destiny.
626
00:34:43,503 --> 00:34:45,269
There's an ocean flowing here.
627
00:34:45,271 --> 00:34:46,470
There's a current flowing
628
00:34:46,472 --> 00:34:49,540
from past to future
and from future to past.
629
00:34:51,376 --> 00:34:55,846
The Universe
may already have a destiny.
630
00:34:55,848 --> 00:34:58,816
But can we mere mortals
ever know it?
631
00:34:58,818 --> 00:35:01,752
One scientist thinks
he's discovered
632
00:35:01,754 --> 00:35:04,889
the mathematical limit
of human knowledge.
633
00:35:10,044 --> 00:35:13,178
Scientists have spent
3,000 years
634
00:35:13,478 --> 00:35:17,980
trying to learn as much as they
can about the world we live in.
635
00:35:17,982 --> 00:35:20,550
We've done pretty well.
636
00:35:20,552 --> 00:35:25,354
We understand how planets,
stars, and galaxies work.
637
00:35:25,356 --> 00:35:29,425
But to know the fate
of the entire universe,
638
00:35:29,427 --> 00:35:33,362
just imagine how much more
there is to know.
639
00:35:33,364 --> 00:35:38,501
So perhaps it's time to ask
ourselves an important question.
640
00:35:38,503 --> 00:35:43,105
Are there some things we just
aren't meant to understand?
641
00:35:46,844 --> 00:35:50,379
Theoretical physicist Tom Banks
642
00:35:50,381 --> 00:35:53,249
believes the best way
to understand eternity
643
00:35:53,251 --> 00:35:56,786
is to calculate how much
we can ever know.
644
00:35:56,788 --> 00:36:00,823
And what we can know
is what we can measure.
645
00:36:00,825 --> 00:36:04,827
So, you can see the Pacific
Ocean is here behind me,
646
00:36:04,829 --> 00:36:07,129
and the Pacific Ocean is huge.
647
00:36:07,131 --> 00:36:10,266
We couldn't possibly
measure it with rulers,
648
00:36:10,268 --> 00:36:13,069
so we measure it
by using trigonometry,
649
00:36:13,071 --> 00:36:14,437
all kinds of math.
650
00:36:18,575 --> 00:36:21,944
The Pacific Ocean
may be massive,
651
00:36:21,946 --> 00:36:25,214
but we've traversed its length
and breadth
652
00:36:25,216 --> 00:36:29,018
and mapped out all of
its 64 million square miles.
653
00:36:29,020 --> 00:36:31,287
However, it isn't even a speck
654
00:36:31,289 --> 00:36:34,056
compared with
the entire universe.
655
00:36:34,058 --> 00:36:37,360
It is much too big for us
to physically measure.
656
00:36:37,362 --> 00:36:40,796
Our Universe -- we can't even
get out there to most of it.
657
00:36:40,798 --> 00:36:43,599
And we measure it by receiving
light from it,
658
00:36:43,601 --> 00:36:45,067
sending light out to it,
659
00:36:45,069 --> 00:36:47,236
and getting all kinds
of signals.
660
00:36:47,238 --> 00:36:49,472
And we figure out
where things are,
661
00:36:49,474 --> 00:36:50,907
how far away they are.
662
00:36:50,909 --> 00:36:55,945
But the Universe does
not just stretch out over space.
663
00:36:55,947 --> 00:36:58,147
It also extends over time,
664
00:36:58,149 --> 00:37:01,183
from its beginning
in the Big Bang
665
00:37:01,185 --> 00:37:02,818
to the far future.
666
00:37:02,820 --> 00:37:06,088
What would it take
to know everything
667
00:37:06,090 --> 00:37:08,157
about such a vast place?
668
00:37:08,159 --> 00:37:12,528
Tom thinks he can calculate
the answer to that question
669
00:37:12,530 --> 00:37:17,033
using something he calls
"the theory of causal diamonds."
670
00:37:17,035 --> 00:37:21,203
I'm drawing
a schematic diagram,
671
00:37:21,205 --> 00:37:23,906
showing a causal diamond.
672
00:37:23,908 --> 00:37:27,109
This is my past.
This is my future.
673
00:37:27,111 --> 00:37:28,778
And this diamond represents
674
00:37:28,780 --> 00:37:31,380
everything I could've done
experiments on
675
00:37:31,382 --> 00:37:34,784
during that whole history
from the beginning to the end.
676
00:37:34,786 --> 00:37:38,054
That region in space-time,
677
00:37:38,056 --> 00:37:39,488
it forms a diamond shape
678
00:37:39,490 --> 00:37:42,425
because light goes out
in sort of a cone like this,
679
00:37:42,427 --> 00:37:45,061
and then if I look back
from the latest time,
680
00:37:45,063 --> 00:37:46,662
it goes backwards in a cone.
681
00:37:46,664 --> 00:37:48,731
You put those two
cones together,
682
00:37:48,733 --> 00:37:50,933
and they're sort of
a diamond shape.
683
00:37:53,504 --> 00:37:56,205
A causal diamond
marks the limit
684
00:37:56,207 --> 00:37:59,175
of how much of the Universe
a measuring device
685
00:37:59,177 --> 00:38:00,810
could ever hope to reach.
686
00:38:00,812 --> 00:38:03,913
When that device sends out
a light beam,
687
00:38:03,915 --> 00:38:06,182
it heads out into the Universe,
688
00:38:06,184 --> 00:38:08,918
bounces off
some distant galaxies,
689
00:38:08,920 --> 00:38:13,155
and finally returns to the
device billions of years later.
690
00:38:13,157 --> 00:38:15,391
Tom has been able to calculate
691
00:38:15,393 --> 00:38:19,695
that the amount of information
existing inside that diamond
692
00:38:19,697 --> 00:38:22,064
is related to the area
of a sphere
693
00:38:22,066 --> 00:38:26,569
that just fits around it
at its widest point,
694
00:38:26,571 --> 00:38:30,272
a sphere he calls
"the holographic screen."
695
00:38:30,274 --> 00:38:32,475
So now we can ask
the question,
696
00:38:32,477 --> 00:38:35,144
suppose there was some machine
that lived forever
697
00:38:35,146 --> 00:38:37,713
from the beginning of
the Universe to the end?
698
00:38:37,715 --> 00:38:41,083
How big does the holographic
screen of the causal diamond
699
00:38:41,085 --> 00:38:43,986
of that infinitely long-lived
detector ever get?
700
00:38:43,988 --> 00:38:45,454
And it's very important,
701
00:38:45,456 --> 00:38:48,157
because that determines
how much information
702
00:38:48,159 --> 00:38:49,859
there could've possibly been
703
00:38:49,861 --> 00:38:51,994
in this region
of space and time.
704
00:38:51,996 --> 00:38:56,298
Knowing absolutely
everything there is to know
705
00:38:56,300 --> 00:39:00,803
about every atom and every
subatomic particle in existence
706
00:39:00,805 --> 00:39:05,274
would mean collecting a truly
mind-blowing amount of data.
707
00:39:05,276 --> 00:39:09,445
This number is 10
to the 10 to the 123.
708
00:39:09,447 --> 00:39:13,282
It's a 1 with 10
to the 123 zeros after it.
709
00:39:13,284 --> 00:39:17,620
That number is so huge
that it's hard to imagine it.
710
00:39:17,622 --> 00:39:21,457
If I started trying to write
that number down
711
00:39:21,459 --> 00:39:24,093
and I wrote a zero every second,
712
00:39:24,095 --> 00:39:26,095
I would run out of time
713
00:39:26,097 --> 00:39:29,999
long before the whole history
of the Universe,
714
00:39:30,001 --> 00:39:32,501
and I would never get
to the end of it.
715
00:39:32,503 --> 00:39:35,805
But could
an advanced civilization
716
00:39:35,807 --> 00:39:38,040
actually collect this much data
717
00:39:38,042 --> 00:39:40,943
and know everything
about the Universe
718
00:39:40,945 --> 00:39:42,745
and thus learn its fate?
719
00:39:42,747 --> 00:39:44,680
The answer, Tom believes,
720
00:39:44,682 --> 00:39:49,585
is contained
in this tiny cup of water.
721
00:39:49,587 --> 00:39:53,522
So, in this little bit of water
I just got out of the Pacific,
722
00:39:53,524 --> 00:39:55,291
there are sextillion atoms.
723
00:39:55,293 --> 00:39:57,226
That's trillions of trillions.
724
00:39:57,228 --> 00:39:59,829
If we wanted to measure
all those atoms,
725
00:39:59,831 --> 00:40:02,364
we'd have to have
a really big machine.
726
00:40:02,366 --> 00:40:06,435
We'd need a device that was
larger than the United States.
727
00:40:06,437 --> 00:40:10,272
But collecting data
on the entire Universe
728
00:40:10,274 --> 00:40:13,275
is not just a monumental
engineering challenge.
729
00:40:13,277 --> 00:40:17,713
The laws of physics actually
prevent us from doing it.
730
00:40:17,715 --> 00:40:20,983
If we tried to measure
every atom in existence,
731
00:40:20,985 --> 00:40:23,786
we would end up
using so much equipment
732
00:40:23,788 --> 00:40:27,723
that we'd fill space with more
stuff than it could handle,
733
00:40:27,725 --> 00:40:31,694
and the entire experiment would
collapse into a black hole,
734
00:40:31,696 --> 00:40:34,563
destroying all that information
with it.
735
00:40:34,565 --> 00:40:36,232
Whoa!
736
00:40:38,268 --> 00:40:41,837
Tom has calculated
that we can measure no more
737
00:40:41,839 --> 00:40:45,441
than 10 to the 10 to the 90 bits
of information
738
00:40:45,443 --> 00:40:49,044
before we cause the entire
Universe to collapse
739
00:40:49,046 --> 00:40:50,546
into a black hole.
740
00:40:50,548 --> 00:40:53,182
This may seem like
a gigantic number,
741
00:40:53,184 --> 00:40:55,918
but it is actually just
a tiny fraction
742
00:40:55,920 --> 00:40:58,654
of 10 to the 10 to the 123,
743
00:40:58,656 --> 00:41:02,758
which is all that
there is to know.
744
00:41:02,760 --> 00:41:06,395
That number is so incredibly
smaller than this number,
745
00:41:06,397 --> 00:41:09,365
that there's no hope
that any civilization,
746
00:41:09,367 --> 00:41:11,267
no matter how sophisticated,
747
00:41:11,269 --> 00:41:14,370
could possibly measure all
of the information
748
00:41:14,372 --> 00:41:18,340
that there is in the Universe
throughout its entire history.
749
00:41:18,342 --> 00:41:22,344
All we can ever learn
about the Universe
750
00:41:22,346 --> 00:41:26,315
is an impossibly tiny morsel
of what's out there.
751
00:41:26,317 --> 00:41:27,750
And Tom argues,
752
00:41:27,752 --> 00:41:32,221
trying to predict the future
based on such scant knowledge
753
00:41:32,223 --> 00:41:33,789
is utterly futile.
754
00:41:33,791 --> 00:41:39,261
So, perhaps we should quit
worrying about the end of time
755
00:41:39,263 --> 00:41:42,164
and learn to live for the now.
756
00:41:42,166 --> 00:41:45,668
It's natural for us
to want to know everything.
757
00:41:45,670 --> 00:41:50,139
And we like to make up stories
about everything.
758
00:41:50,141 --> 00:41:52,942
And those stories
are often wrong.
759
00:41:52,944 --> 00:41:55,110
So people...are people.
760
00:41:55,112 --> 00:41:58,080
We're finite.
We're not Gods.
761
00:41:58,082 --> 00:42:00,583
We're -- we don't own
the Universe.
762
00:42:00,585 --> 00:42:03,352
We're a very tiny portion
of the Universe.
763
00:42:03,354 --> 00:42:07,156
And we've now discovered that
we're a much tinier portion
764
00:42:07,158 --> 00:42:09,325
than we might've thought before.
765
00:42:09,327 --> 00:42:12,094
We don't have the right,
in some sense,
766
00:42:12,096 --> 00:42:15,564
to expect to know everything
that there is to know.
767
00:42:20,036 --> 00:42:23,472
Will the Universe last forever?
768
00:42:23,474 --> 00:42:25,975
Is eternity already out there,
769
00:42:25,977 --> 00:42:30,512
projecting the present back
to us from the far future?
770
00:42:30,514 --> 00:42:34,483
Or will a cosmic apocalypse
destroy everything
771
00:42:34,485 --> 00:42:36,485
in the blink of an eye?
772
00:42:36,487 --> 00:42:40,256
We don't know,
and we probably never will,
773
00:42:40,258 --> 00:42:44,260
because some questions
require more knowledge
774
00:42:44,262 --> 00:42:46,195
than we can ever get.
775
00:42:46,197 --> 00:42:49,531
And maybe that's not so bad.
776
00:42:49,533 --> 00:42:53,769
After all,
what fun would life be
777
00:42:53,771 --> 00:42:57,406
if we already knew
how it was going to end?
778
00:42:57,431 --> 00:43:01,431
== sync, corrected by elderman ==