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  • "The Elegant Universe", hosted by Brian Greene.

  • Based on "The Elegant Universe" by Brian Greene.

  • Welcome to the 11th dimension

  • Imagine that we were able to control space

  • Or control time.

  • The kinds of things that we'd be able to do

  • Would be amazing.

  • I might be able to go from here...

  • To here...

  • To here...

  • To here...

  • And over to here in only an instant.

  • Now,we all think that this kind of trip

  • Would be impossible.

  • And it probably is.

  • But in the last few years,

  • Our ideas about the true nature of space and time

  • Have been going through some changes.

  • And things that used to seem like science fiction

  • Are looking not-so-far-fetched.

  • It's all thanks to a revolution in physics

  • Called "string theory,"

  • Which is offering a whole new perspective

  • On the inner workings of the universe.

  • String theory holds out the promise that

  • We can really understand questions of

  • Why the universe is the way it is

  • At the most fundamental level.

  • String theory is really the wild west of physics.

  • This is an area of theoretical physics

  • Which is so radically different from

  • Anything that's been before.

  • This radical new theory starts with the simple premiss

  • That everything in the universe,

  • The earth,these buildings,

  • Even forces like gravity and electricity,

  • Are made up of incredibly tiny,

  • Vibrating strands of energy called "strings."

  • And small as they are,

  • Strings are changing everything

  • We thought we knew about the universe,

  • Especially our ideas about the nature of space.

  • To see how,let's first shrink all of space

  • To a more manageable size.

  • Imagine that the whole universe consisted of nothing

  • More than my hometown,manhattan.

  • So now,just one borough of new york city

  • Makes up the entire fabric of space.

  • And just for kicks,

  • Let's also imagine that I'm the ceo of a large corporation

  • With offices on wall street.

  • And because time is money,

  • I need to find the quickest route from my apartment,

  • Here in upper manhattan to my offices in lower manhattan.

  • Now,we all know that the shortest distance

  • Between two points is a straight line,

  • But even if there's no traffic

  • -A bit of a stretch even in our imaginary manhattan-

  • It'll still take us some amount of time to get there.

  • By going faster and faster,

  • We can reduce the travel time.

  • But because nothing can go faster than the speed of light,

  • There is a definite limit to how much time

  • We can cut from our journey.

  • This manhattan universe fits with an old,

  • Classical vision of space,

  • Basically a flat grid that's static and unchanging.

  • But when Albert Einstein looked at the fabric of space,

  • He saw something completely different.

  • He said that space wasn't static;

  • It could warp and stretch.

  • And there could even be unusual structures of space

  • Called "wormholes."

  • A wormhole is a bridge or tunnel

  • That can link distant regions of space,

  • In effect,a cosmic shortcut.

  • In this kind of universe,

  • My commute would be a new yorker's dream.

  • But there is a hitch, to create a wormhole,

  • You've got to rip or tear a hole in the fabric of space.

  • But can the fabric of space really rip?

  • Can this first step toward

  • Forming a wormhole actually happen?

  • Well,you can't answer these questions

  • On an empty stomach.

  • Turns out that by looking at my breakfast

  • --coffee and a doughnut--

  • We can get a pretty good sense of

  • What string theory says

  • About whether the fabric of space can tear.

  • Imagine that space is shaped like this doughnut.

  • You might think that it would be very different

  • From a region of space shaped like this coffee cup.

  • But there's a precise sense

  • In which the shape of the doughnut

  • And the coffee cup are actually the same,

  • Just a little disguised.

  • You see,they both have one hole.

  • In the doughnut it's in the middle

  • And in the coffee cup it's in the handle.

  • That means we can change the doughnut

  • Into the shape of a coffee cup and back again

  • Without having to rip or tear the dough at all.

  • Okay,but suppose you want to change the shape

  • Of this doughnut into a very different shape,

  • A shape with no holes.

  • The only way to do that is to tear the doughnut like this

  • And then re-shape it.

  • Unfortunately,according to Einstein's laws,

  • This is impossible.

  • They say that space can stretch and warp,

  • But it cannot rip.

  • Wormholes might exist somewhere fully formed,

  • But you could not rip space to create a new one,

  • Over manhattan or anywhere else.

  • In other words,I can't take a wormhole to work.

  • But now string theory is giving us

  • A whole new perspective on space,

  • And it's showing us that Einstein wasn't always right.

  • To see how,

  • Let's take a much closer look at the spatial fabric.

  • If we could shrink down

  • To about a millionth of a billionth of our normal size,

  • We'd enter the world of quantum mechanics,

  • The laws that control how atoms behave.

  • It's the world of light and electricity and everything else

  • That operates at the smallest of scales.

  • Here,the fabric of space is random and chaotic.

  • Rips and tears might be commonplace.

  • But if they were,

  • What would stop a rip in the fabric of space

  • From creating a cosmic catastrophe?

  • Well,this is where the power of strings comes in.

  • Strings calm the chaos.

  • And as a single string dances through space,

  • It sweeps out a tube.

  • The tube can act like a bubble that surrounds the tear,

  • A protective shield with profound implications.

  • Strings actually make it possible for space to rip.

  • Which means that space is far more dynamic

  • And changeable than even Albert Einstein thought.

  • So does that mean that wormholes are possible?

  • Will I ever be able to take a stroll on Everest,

  • Grab a baguette in Paris

  • And still make it back to new york in time

  • For my morning meeting?

  • It would be kind of cool,

  • Though it's still a very distant possibility.

  • But one thing that is certain

  • Is that string theory is already showing us

  • That the universe may be a lot stranger

  • Than any of us ever imagined.

  • For example,string theory says we're surrounded

  • By hidden dimensions,

  • Mysterious places beyond the familiar

  • Three-dimensional space we know.

  • People who've said that

  • There were extra dimensions of space,

  • Have been labeled as,you know,crackpots

  • Or people who are bananas.

  • I mean,what,do you think there are extra dimensions?

  • Well,string theory really predicts it.

  • What we think of as our universe

  • Could just be one small part of something much bigger.

  • Perhaps we live on a membrane,

  • A three-dimensional membrane

  • That floats inside higher dimensional space.

  • There could be entire worlds right next to us,

  • But completely invisible.

  • These other worlds would,in a very literal sense,

  • Be,be parallel universes.

  • This isn't a particularly exotic or,or strange notion.

  • No wonder physics students are lining up

  • To explore the strange world of string theory.

  • String theory is very active.

  • Things are happening. there are a lot of people doing it.

  • Most of the young kids,given the choice,

  • At a ratio of something like ten to one,

  • They will go into string theory.

  • But strings weren't always this popular.

  • The pioneers of string theory struggled for years,

  • Working alone on an idea that nobody else believed in.

  • Here is generalized, For decades,

  • Physicists believed that the tiniest bits inside an atom

  • Were point particles.

  • Flying around the outside were the electrons,

  • And inside were protons and neutrons

  • Which were made up of quarks.

  • But string theory says that what we thought

  • Were indivisible particles are actually tiny,

  • Vibrating strings.

  • It's nothing really mystical. it's a really tiny string.

  • It either closes in to its little circle or it has end points

  • But it's just a little string.

  • In the 1980s,the idea caught on,

  • And people started jumping on the string bandwagon.

  • Well,the fact that

  • Suddenly all these other people were working in the field

  • Had its advantages and its disadvantages.

  • It was wonderful to see

  • How rapidly the subject could develop now,

  • Because so many people were working on it.

  • One of the great attractions of strings is their versatility.

  • Just as the strings on a cello can vibrate

  • At different frequencies,

  • Making all the individual musical notes,

  • In the same way,

  • The tiny strings of string theory

  • Vibrate and dance in different patterns,

  • Creating all the fundamental particles of nature.

  • If this view is right,then put them all together

  • And we get the grand and beautiful symphony

  • That is our universe.

  • What's really exciting about this

  • Is that it offers an amazing possibility.

  • If we could only master the rhythms of strings,

  • Then we'd stand a good chance of explaining all the matter

  • And all the forces of nature,

  • From the tiniest subatomic particles

  • To the galaxies of outer space.

  • This is the potential of string theory,

  • To be a unified "theory of everything."

  • But,at first sight,in our enthusiasm for this idea,

  • We seem to have gone too far.

  • Because we didn't produce just one string theory,

  • Or even two

  • We somehow managed to come up with five.

  • Five different string theories,

  • Each competing for the title of the theory of everything.

  • And if there's going to be a

  • "the fundamental theory of nature,"

  • There ought to be one of them.

  • I suppose a number of string theorists thought,

  • "ah,that's fantastic. that's wonderful."

  • And maybe one of these will end up being the right theory

  • Of the world." and yet,

  • There must have been a little nagging voice

  • At the back of the head that said,

  • "well,why are there five?"

  • With five competing players,

  • The stage of string theory was looking a little crowded.

  • The five theories had many things in common.

  • For example,they all involved vibrating strings,

  • But their mathematical details appeared

  • To be quite different.

  • Frankly,it was embarrassing.

  • How could this unified theory of everything

  • Come in five different flavors?

  • This was a case where more was definitely less.

  • But then something remarkable happened.

  • This is Ed Witten.

  • He's widely regarded as one of

  • The world's greatest living physicists,

  • Perhaps even Einstein's successor.

  • Ed Witten is a very special person in the field.

  • He clearly has a grasp,

  • Particularly of the underlying mathematical principles,

  • Which is far greater than most other people.

  • Well,you know,we all think we're very smart;

  • He's so much smarter than the rest of us.