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Is Time Travel Possible? | Episode 206 | Closer To Truth

Is Time Travel Possible? | Episode 206 | Closer To Truth
science fiction loves

time

travel

so many stories can be told but suppose

time

travel

were real who would i meet what would i do would i try to kill hitler as a baby change history and save millions of lives would i help my grandmother when as a child she suffered in europe but what about those famous paradoxes suppose a

time

travel

er would kill his grandmother before she conceived his mother no mother no him but then how could he have gone back in

time

in the first place some scientists take

time

travel

seriously not to make machines but to explore the nature and limits of reality is

time

travel

possible

i'm robert lawrence kuhn and

closer

to

truth

is my journey to find out

time

travel

seems im

possible

so i begin in new york with the author of physics of the im

possible

a professor at the city university of new york michio kaku he likes pushing boundaries let's start with isaac newton isaac newton believed that

time

was like an arrow once you fired it it went in a straight direction one second on the earth was one second on mars was one second on jupiter it never reversed directions along comes einstein who says not so fast not so fast

time

is like a river old man river that meanders around stars speeds up and slows down the new wrinkle in all this which is causing all the excitement and the dismay of philosophers is that this river of

time

can fork into two rivers or perhaps the river of

time

can have whirlpools and

time

can go in on itself in that case

time

...
is time travel possible episode 206 closer to truth

travel

is something you have to take very seriously because einstein's equations do allow for

time

travel

and their blueprints blueprints for different kinds of

time

travel

design that are compatible with einstein's theory for example gigantic spinning cylinders you go around the cylinder and you come back before you left colliding cosmic strings you wind around these cosmic strings and you come back before you left and the key element is that in einstein's theory it allows this under certain solutions that's right

time

and space are like a fabric like rubber like a trampoline net however if you stretch the trampoline net so much it can rip perhaps and perhaps you can turn this trampoline net into a pretzel and allow yourself to go backwards in

time

now of course there's a catch there's always a catch in these things the energy the gasoline necessary to do this is fabulous even an atomic bomb does not have enough energy to drive a

time

machine for a

time

machine you need the energy of an exploding star how about all the logical paradoxes that one would come across in

time

travel

going back to the past killing your grandmother and all of those kinds of issues or meeting your teenage mother when she's a teenager and she falls in love with you so how can you be born if your teenage mother just fell in love with you there are two ways to resolve these paradoxes the first is self-consistency that if you want to shoot your parents before you're born...
is time travel possible episode 206 closer to truth
there's something preventing you from pulling that trigger maybe there's a hidden law of physics that says you cannot create a

time

paradox i don't believe that yeah that seems so far out as far out i believe that the river of

time

forks into two rivers if you saw back to the future part two very carefully doc brown this einstein figure goes to the blackboard and draws the

time

line from the 50s to the 80s and then he draws a separate line that splits off from the main

time

line the river of

time

forks into two rivers is this getting to the so-called many world interpretation of quantum mechanics would that be that is the simplest way to resolve all these paradoxes that never seem very simple to me well it's the simplest in the sense that you don't have to add any other assumptions other than quantum mechanics so if you go backwards in

time

and say abraham lincoln from being assassinated in in the ford's theater you saved somebody else's abraham lincoln who's genetically equivalent to your abraham lincoln but you've entered another universe if you shoot your parents before you're born you've shot somebody else's parents before you're born who's genetically equivalent to your parents so you can go backwards in

time

continually monkey with your own past however you're monkeying with in some sense a parallel past right now maybe creating a parallel creating a whole new universe that's right and stephen hawking even...
is time travel possible episode 206 closer to truth
said there's got to be a laws of physics preventing this thing from happening well we've tried and tried and tried and failed we cannot find any law of physics preventing you from going backwards in

time

it seems to be consistent with the known laws of physics the trick is you have to have this energy on the scale of a star you'd have to be a very advanced civilization so these tourists from the future are just not a hundred years into the future these tourists from the future would be perhaps millions of years in the future the ability to control the output of a star we physicists or hot rodders of physics we push the equations until they break down so stephen hawking assumed that they would break down well we were shocked they didn't break down the laws of physics seem to be compatible with

time

machines this is very unsettling because it means that perhaps just perhaps

time

travel

is

possible

for advanced civilizations cannot be ruled out so the key for

time

travel

is einstein's theory of special relativity which seems easy to describe but hard to believe i need more einstein so i go to princeton to meet j richard gott professor of astrophysics who likes to explain how

time

travel

might work richard how can we begin to look at the physics of

time

travel

well in his theory of special relativity in 1905 einstein showed that

time

travel

to the future is

possible

he showed that moving clocks tick slowly so if you want to visit the earth in the year 3000...
all you need is a fast spaceship so you just go at 99.995 percent the speed of light out to a star 500 light years away turn around and come back at the same speed and when you get back the earth will be in the year 3000 thousand years later but you will have only aged 10 years so this is how you can visit the future and indeed our greatest

time

travel

er so far is sergey krikalov who has

travel

ed 1 48th of a second to the future by or his numerous orbital missions around the earth now obviously this has to be enormously faster a very very high fraction of the speed of light but we accelerate particles to that speed today you know we have we have protons going this fast it's just a matter of money in engineering and i said take note it's expensive but

possible

in principle we know for sure okay now what about

time

travel

to the past that sounds much more complicated that sounds more difficult um there's a poem there was a young lady named bright she

travel

ed far faster than light she left one day in a relative way but returned the previous night so if you could go faster than the speed of light from special relativity we know that theoretically you could go back in

time

however einstein showed that you couldn't build a rocket that would go faster than the speed of light you could build one that would go very close to the speed of light but not faster but in 1915 his theory of general relativity showed that there was curved space

time

this explained gravity and...
in curved space

time

you can have a shortcut where you can beat a light beam to a destination and this opens the door to having

time

travel

to the past so what's occurring here is that if this is space-

time

and this is

time

going this way space this way your your path through

time

like this this is your world line your path through

time

you're going toward the future always but what can happen here is that the space

time

is sufficiently twisted so that you while going toward the future all the

time

yet circle back and visit an event in your own past and so the

time

travel

er circling the cosmic strings is going toward the future toward the future toward the future but yet comes back and visits an event and this will be caused by the curvature of space

time

yes and how far back can you go theoretically think spaghetti and o's so if you're not lucky enough to find two cosmo infinite cosmic strings passing each other at the right speed you can always take a loop of cosmic string that you find manipulate it by flying massive spaceships around it so you cause it to contract by a large factor and the sides of the strings will pass each other at a speed fast enough to make a

time

machine close slower than the speed of light but still fast enough to make a

time

machine and then i showed that this would be sufficiently compact that the

time

travel

region would be likely hidden inside a black hole if you were lucky you could do the

time

travel

inside the black hole but...
you're never getting back out to brag to your friends never telling anybody about it so the laws of physics as we understand them today seem to allow

time

travel

solutions and the question we're asking ourselves is will we discover new laws of physics in the future that'll somehow stop it so we're we're probing the boundaries of the laws of physics under extreme situations which may give us clues as to how they work

time

travel

is theoretically

possible

but practically not likely still worth the effort surely diving deeply into the ocean of reality

time

travel

is all about the flexing and twisting of space and

time

it's called warping which includes wormholes those theoretical tunnels that connect one part of the universe to another no one is more knowledgeable about the warping of space-

time

than kip thorne the feynman professor of theoretical physics at caltech we meet in kipp's lab a prototype gravity wave detector kip i'm interested in the use of

time

travel

wormholes theoretically to probe the nature of reality we would like to probe the laws of physics through a combination of experiment and theory but there are areas where the experiment is so challenging we can't do it with the human technology in this century and wormholes and some aspects of the nature of space are in that domain predictions about them and so thought experiments einstein taught us are a powerful tool for probing the nature of physics you just ask could in...
principle and our infinitely advanced civilization could such a civilization build a wormhole to

travel

from here to another galaxy and when you ask that kind of a question you then go into the laws of physics and you probe it mathematically geometrically in the laws of physics and it teaches you a lot about the nature of space and

time

how might that work conceptually from the laws of physics the the warping of space in a wormhole is so intense it's it's like the warping of space in a stretched uh rubber membrane uh it wants to shrink and the wormhole wants to shrink and pinch off so when you try to

travel

through you die and so can can they be held open how do you hold them open and so we then in this way discovered intimate relationship between the nature of energy and tensions on one hand and the nature of warping of space on another hand now how does that relate to

time

and the possibility of

time

travel

in either direction to the future or to the past if you have wormholes then if you move the mouth of one wormhole down near the surface of a black hole

time

flows very slowly there compared to the rate of flow of

time

back here on earth and so the two mouths get out of sync mouth of the wormhole sits down near the surface of the black hole and it sits there with only a few hours passing while up here on earth a billion years pass and so we on earth can then go down through the wormhole and can come out near the surface of the black hole a billion years earlier we...
can then come out and go back up into the external universe a billion years earlier than we went down so if you have wormholes there's a natural way to make

time

machine so this was wonderful when when my students and i discovered this i was very excited uh but then probing more deeply and talking with other colleagues i was forced to realize that there's a uniform mechanism that when you're trying to turn a wormhole into a

time

machine in this way a universal mechanism that always creates a violent explosion that very likely destroys the wormhole right at the moment when it begins to make

time

travel

possible

and so

time

machines if you try to create them appear to self-destruct we simply do not have the understanding of the laws of physics to be able to speculate about that quantitatively yet we have to have a much deeper understanding of quantum gravity to get the answer whether that's

possible

warping wormholes exotic stuff

time

travel

involves the most mysterious matter in the universe but is there anything about

time

travel

beyond science fred alan wolff a physicist by training sees far out meaning in quantum theory his views are controversial appealing more to mystics than to scientists fred is undeterred fred from your work in quantum mechanics is there any real possibility to

time

travel

wormholes all that exotic stuff well it's always

possible

to

time

travel

if you can find a wormhole and if you can find some exotic matter which has negative...
pressure which will keep the darn thing open long enough for you to slip through yes of course i believe that the mind that the mind the sub space-

time

realm out of which i believe matter comes into being according to my understanding of quantum physics that that realm is a spaceless

time

less realm which means that it's like in a sense a place where closed

time

-like paths can emerge so it seems to me that the mind itself has something in its nature which is

time

-

travel

ly i don't know how to quite find the language to describe it what i think is going on is that the mind is constructing our temporal experience we have an objective sense of

time

certainly the sun rises the sun sets we all agree about that we have an idea of what that means but subjective

time

which is very much like objective

time

but is it really no it's not if you're on a hot date i mean one hour can feel like five minutes it ain't enough

time

and if you're on a horrible date one minute can feel like five hours i mean so there's a relativity there's a about

time

now there are good psychological reasons why that occurs in our normal life but can you infer from that that there is a a

time

dimension to a deeper consciousness that has a different reality i think so i believe that every

time

there's a conscious experience we're creating a sequence so that the next conscious experience and the one following for a personal conscious experience that that sequence implies what i...
would call normal

time

order if it goes from more probable to less probable but if it goes from less probable to more probable it's actually going backwards in

time

okay i can't prove this but in my speculative thinking this is what we do when we practice for example yoga or when we learn something new or when we forget something in order to do something new we have to use this process of going backwards and forwards in

time

not so not objective

time

i'm not talking about changing the world

time

talking about the internal clock your subjective

time

sense that that's where this is but that's an internal psychological process i'm talking about is there a deeper uh reality as you see consciousness being more fundamental that can access objective

time

in different ways well objective

time

is a

time

that we agree as objective

time

relativity theory tells us that it's not absolute for one thing which objective

time

am i trying to get to so to speak there is no such thing i think the thing to do is to look at the fundamental way in which we construct

time

that sequences can be ordered why should we try to worry about changing objective

time

because objective

time

for us is only our point of view i agree that according to einstein objective

time

does not exist but does that mean that human subjective

time

is a meaningful description of the reality of

time

wouldn't that suppose a central role for consciousness in the cosmos i need to get back to...
hardcore physics seth lloyd believes that the universe fundamentally is a computer and that reality fundamentally is information does this help with

time

travel

seth is professor of mechanical engineering at mit we meet in his quantum computing lab seth how do you look at the possibility of

time

travel

and these strange ways of skipping through space well we're

travel

ing through

time

right now we just happen to be

travel

ing forward through

time

and nobody seems to think this is remarkable right strikes me is already rather remarkable that we're

travel

ing forward through

time

in fact there are very specific models in which

time

travel

or going backwards in

time

can in fact happen um based on ideas from quantum information theory there's a famous problem about black holes which is a black hole you know something that's so massive that light itself can't escape so anything that goes in can't come out they're the roche motels of the cosmos bits check in but they don't check out but yet at the same

time

they can evaporate so hawking taught us that black holes are radiating a big black hole radiates very very slowly but nonetheless there's radiation coming out the radiation looks completely random and hawking thought that all the information about what had gone into the black hole was completely destroyed two physicists gary horowitz and juan maldasena came up with an alternative suggestion for how black holes might evaporate and in their model...
it's quite

possible

for information to go into the black hole the black hole evaporates and then the information escapes so what's the implication of that it means in order to to have information escape from a black hole that's equivalent to being able to go backwards in

time

if you're going if you can go faster than the speed of light effectively faster than the speed of light then you can

travel

backward in

time

right this is the problem with going faster than those people that gives rise to all sorts of paradoxes so the relationship to

time

travel

is black hole evaporation and

time

travel

are intimately related to each other so that's one thing that's the first part now the other implication of course which is dear to my heart is it means you could use black holes as some kind of computers right because you send this information in something horrible happens to it in the singularity of the center of the black hole but radiation comes out and actually what is this radiation but the information that went in in processed form so the black hole is effectively computing so as you look at this total picture of all these weird ideas of

time

travel

wormholes quantum teleportation do you think there's some practical implication of this in the future well you know when i was in a graduate student at cambridge i my grandmother was 90 years old came over to visit and she said so seth what are you working on could it have any implications and i said well...
maybe the only implication would be building a

time

machine and she said better hurry up and i think i i think that uh if your

time

machine involves untested speculative theories and the way to

travel

backwards in

time

is first you have to jump into this black hole well i think we may take a while before we find taker certainly i wouldn't be the first one to do it even if it were my own theory and i believed in it implicitly

time

and its passage feel to be absolute and unchanging the most basic part of our world the stage on which the play of existence is presented the feeling is deceiving and

time

travel

explains why as einstein showed

time

is unified with space and

time

is relative there is no absolute standard of

time

and all points in

time

somehow coexist although

time

can seem to run in either direction forward or backward other factors must prevent kill your grandmother paradoxes not even god could make something that did exist never exist in considering existence it's

time

to get

closer

to

truth

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