Neil deGrasse Tyson’s Guide To Time Travel — StarTalk 101

Summary

This discussion delves into the fascinating concepts of controlled backward time travel, focusing on the implications of wormholes and the nature of observing such travel from a third-person perspective. It explores how wormholes could theoretically allow for travel between different points in space and time, potentially leading to intriguing scenarios where one could enter a wormhole and emerge at another location in a different time. The conversation also touches on the ideas of information, entropy, and the paradoxes associated with time travel, such as the grandfather paradox, while referencing popular culture representations of time travel in movies and theories proposed by scientists like Stephen Hawking.

Takeaways

• 😄 Time travel to the past could be possible through wormholes, where one opening is in the future and the other is in the past, allowing you to travel between the two points in time.
• 🤔 The 'grandfather paradox' poses a significant challenge to the idea of backwards time travel, as preventing your ancestors from meeting could erase your own existence and the ability to travel back in time.
• 🔗 Introducing minor changes to the past, like delaying conception by a few minutes, could result in an entirely different person being born, rather than simply altering your own timeline.
• ⏰ Time travel to the future is theoretically possible by traveling close to the speed of light, where time dilation would cause the traveler to age slower than those on Earth, effectively jumping them forward in time.
• 🕰️ GPS satellites orbiting Earth have their clocks adjusted to account for the effects of time dilation predicted by Einstein's theory of relativity.
• ❓ The absence of time travelers visiting us from the future could be seen as evidence that time travel may never be invented, unless time travelers are deliberately hiding their existence.
• 👥 In higher dimensions beyond our familiar 3D space and one time dimension, our conventional notions of time may not apply, allowing access to an individual's entire timeline simultaneously.
• 🔄 The hypothetical 'tachyon' particle, which could move faster than light, could theoretically send information backwards in time, but may paradoxically cause the very event it was trying to prevent.
• 🎥 Time travel movies often explore different interpretations and implications of time travel, but generally avoid providing explicit scientific explanations for the mechanics involved.
• 🧐 The philosophical and scientific implications of time travel, such as the preservation of cause and effect, and the consistency of the laws of physics, remain highly debated and unresolved.

Q & A

What is the concept of wormholes in relation to time travel?

Wormholes are theoretical tunnels through spacetime that can connect distant points in space and potentially allow travel between different times. If the entrances of a wormhole are moved relative to each other or one is placed near a black hole, it could create a time difference between the two ends, enabling travel to the past or future.

How does the Marvel Universe's portrayal of portals differ from theoretical wormholes in relation to time travel?

In the Marvel Universe, characters like Doctor Strange use portals to move through space, not time. Theoretical wormholes, however, offer the fascinating possibility of not just spatial shortcuts but also tunnels through time, which the Marvel Universe has not explored.

What is the grandfather paradox in the context of time travel?

The grandfather paradox is a theoretical problem that arises when considering the possibility of time travel to the past. It involves a time traveler going back in time and preventing their grandparents from meeting, thus preventing the time traveler's own birth and creating a logical inconsistency or paradox.

How do GPS satellites illustrate Einstein's theory of relativity in practice?

GPS satellites orbit Earth at a high altitude where the effects of Einstein's general theory of relativity are observable. Their clocks tick slightly faster than those on Earth's surface due to being farther from Earth's gravitational pull. This difference is accounted for to ensure the accurate timing necessary for GPS functionality.

What is a tachyon and how does it relate to time travel?

A tachyon is a hypothetical particle that moves faster than the speed of light. According to theoretical physics, if it were possible, crossing the speed of light would result in time moving backward for such a particle. Tachyons have been speculated to enable communication or travel back in time.

Why is traveling forward in time considered possible, while traveling backward presents paradoxes?

Traveling forward in time is possible through the effects of high speeds on time dilation, as predicted by Einstein's theory of relativity. Traveling backward in time, however, introduces logical paradoxes such as the grandfather paradox, challenging the consistency of cause and effect.

How does the movie 'Contact' portray wormhole travel?

In the movie 'Contact', the protagonist travels through what is presumed to be a wormhole to meet extraterrestrial beings. This travel is depicted not as a complex journey but more like stepping through a portal, highlighting the concept of wormholes as shortcuts through space and potentially time.

Can time travel affect entropy and information?

The script hints at the relationship between time travel, entropy, and information, suggesting that traveling through time could have implications on the universe's entropy and the flow of information. Entropy is a measure of disorder, and time travel could theoretically alter the entropy of a system, affecting the direction and flow of information.

What are closed timelike curves and why are they significant in theoretical physics?

Closed timelike curves are theoretical paths through spacetime that return to the same point in space and time, essentially allowing for time loops. They are significant because they challenge our understanding of cause and effect and the linear progression of time, raising questions about the consistency of events in a universe where time travel is possible.

Why do some scientists and theories suggest that time travel to the past may never be possible?

Some scientists and theories suggest that time travel to the past may never be possible due to the paradoxes it introduces, such as the grandfather paradox, which challenge the consistency of cause and effect. Additionally, Stephen Hawking proposed a time travel conjecture that might mathematically or experimentally prove such travel impossible to avoid these paradoxes.

Outlines

00:00

🌀 Exploring Time Travel: Wormholes and Paradoxes

The conversation begins with an intriguing question about what observable effects would manifest if time travel were possible, focusing on the perspective of an observer witnessing someone else traveling through time. The discussion delves into the theoretical framework of using wormholes for time travel, explaining how these hypothetical tunnels could allow for movement between different points in time and space. By altering the relative positions of a wormhole's openings or placing one end near a black hole, a time differential could be created, facilitating travel to the past or future. This concept is contrasted with fictional portrayals in the Marvel Universe and movies like 'Contact,' aiming to distinguish between moving through space and the more complex notion of navigating through time. The segment wraps up by addressing the relationship between faster-than-light travel, wormholes, and the potential for time travel, setting the stage for deeper exploration of the implications and paradoxes associated with this fascinating topic.

05:01

🔮 The Grandfather Paradox and Time Travel Logic

This segment humorously tackles the famous 'grandfather paradox' associated with time travel, illustrating the complexities and absurdities that arise when considering the ability to alter one's ancestral past. It highlights how even small changes, like delaying a meeting between ancestors, could significantly impact one's existence. The discussion extends beyond the straightforward scenario of preventing one's birth, suggesting more nuanced alterations could produce vastly different outcomes without necessarily eradicating an individual's existence. Through a series of whimsical examples involving characters like Michael B. Jordan and scenarios from movies, the conversation underscores the intricate web of cause and effect that makes time travel a rich subject for speculation and fiction, despite the logical conundrums it presents.

10:03

🔄 Tachyons, Time Loops, and Fictional Time Travel

Delving into the realm of hypothetical particles and science fiction, this section introduces the concept of tachyons, particles that theoretically move faster than light and could facilitate communication or travel backward in time. By exploring hypothetical scenarios where tachyons are used to alter events, the conversation illustrates the paradoxical outcomes that can arise, such as causing the event one seeks to prevent. The segment also reflects on various time travel narratives in movies and television, discussing how these stories grapple with the rules and paradoxes of time travel, including encounters with one's future self. Through examples like 'Looper' and 'Quantum Leap,' it highlights the creative ways fiction addresses the challenges of time travel, while acknowledging the underlying scientific mysteries that remain unresolved.

15:05

🧭 Philosophical and Scientific Constraints on Time Travel

This part of the conversation examines the philosophical and scientific considerations surrounding time travel, especially the potential for paradoxes like the grandfather paradox to challenge the possibility of backward time travel. Stephen Hawking's conjecture that future discoveries could definitively rule out such paradoxes is discussed, alongside the intriguing narrative possibilities these constraints offer to storytellers. The dialogue touches on the physical and logical limits of interacting with one's past selves, as depicted in the movie 'Looper,' and explores the necessity of maintaining a logically consistent timeline to avoid paradoxes that could undermine the fabric of reality. This segment underscores the balance between imaginative storytelling in science fiction and the rigorous demands of scientific consistency.

20:06

🚀 The Realities and Speculations of Time Travel

Focusing on the practical aspects of time travel and its portrayal in popular culture, this section addresses the intriguing question of why the absence of time travelers in our present might suggest that time travel will never be invented. It references cultural touchpoints, such as 'The Big Bang Theory,' to discuss societal fascination with time travel and the logical implications of its potential reality. The conversation briefly entertains whimsical theories about the Titanic's sinking to illustrate the imaginative lengths people go to speculate about time travel's impact on historical events. Additionally, it considers the possibility that time travel into the future might be more feasible and less paradoxical than travel into the past, offering a glimpse into the complexities and ongoing debates surrounding this captivating subject.

25:07

🕰️ Theoretical Foundations and Fictional Explorations of Time Travel

In the final segment, the dialogue turns to the theoretical underpinnings of time travel, particularly the role of higher dimensions and the speculative nature of black holes as gateways to other times. It elucidates how our understanding of space-time dimensions integrates time as a critical component of our reality, yet acknowledges our limited ability to navigate the time dimension compared to spatial dimensions. The conversation speculates on the possibilities of interacting with one's timeline from a higher-dimensional perspective, raising profound questions about causality, identity, and the nature of existence itself. Through references to science fiction and theoretical physics, this part weaves together the imaginative possibilities of time travel with the current limits of our scientific understanding.

Keywords

💡Time Travel

The concept of moving between different points in time, either to the past or the future. In the video, time travel is discussed extensively, with various theories and possibilities explored, such as using wormholes or achieving faster-than-light travel. The grandfather paradox, where altering the past could prevent one's own existence, is a key consideration in time travel narratives.

💡Wormholes

Hypothetical tunnels or shortcuts in the fabric of spacetime that could allow for travel across vast distances or even through time itself. The video suggests that if the two openings of a wormhole are separated by a difference in gravitational potential, one could essentially travel to the past or future by passing through it. Wormholes are a common concept in science fiction for enabling time travel.

💡Grandfather Paradox

A potential logical paradox that arises in the context of time travel to the past. If a person travels back in time and alters events in a way that prevents their own birth or existence, it creates a paradoxical situation where the time traveler should not have been able to travel back in the first place. The video discusses this paradox as a significant challenge to the feasibility of backward time travel.

💡Tachyons

Hypothetical particles that can travel faster than the speed of light. According to relativity, if such particles existed, they could theoretically move backward in time from an external observer's perspective. The video explores the concept of using tachyons to send information or messages back in time, highlighting the potential paradoxes that could arise.

💡Spacetime

The combined concept of three-dimensional space and one-dimensional time into a four-dimensional continuum, as described by Einstein's theory of relativity. The video discusses how our perception of time is linked to our position in spacetime, and how altering one's position or velocity within spacetime could potentially enable time travel or altered experiences of time.

💡Entropy

A measure of disorder or randomness in a system. The video briefly mentions entropy in the context of information and its potential relation to time travel. Increasing entropy is associated with the arrow of time and the idea that time travel to the past could potentially violate the laws of thermodynamics and entropy.

💡Faster-than-light Travel

The concept of achieving velocities greater than the speed of light, which is a key requirement for certain theories of time travel. According to relativity, as an object approaches the speed of light, time dilation effects become more pronounced, potentially allowing for forward time travel. The video suggests that if faster-than-light travel were possible, it could enable backward time travel as well.

💡Paradoxes

Logically contradictory or self-inconsistent situations that can arise when considering the implications of time travel. The grandfather paradox is a famous example, but the video also explores other potential paradoxes, such as causing events that prevent one's own time travel or altering the past in ways that should make the present different. Resolving these paradoxes is a significant challenge in time travel theories.

💡Science Fiction

The genre of fiction that explores imaginative and speculative concepts, often based on scientific principles or technological advancements. Time travel is a prevalent theme in science fiction, with various stories and movies exploring different theories, paradoxes, and possibilities. The video frequently references and draws examples from science fiction narratives involving time travel.

💡Relativity

Albert Einstein's groundbreaking theory that describes the relationship between space, time, and the motion of objects. The concepts of time dilation, length contraction, and the equivalence of energy and mass are key principles of relativity that have implications for the possibility of time travel. The video discusses how relativity provides a theoretical framework for understanding the effects of motion on the perception of time.

Highlights

Controlled backwards time travel involving wormholes as shortcuts through space and time.

The concept of wormholes allowing for travel to the past and future by altering the relative positions of their openings.

Comparison of fictional portals in the Marvel Universe to wormholes in theoretical physics.

The idea of a wormhole's throat having length and its implications for travel through space, rather than a unique journey.

Traveling through a wormhole positioned near a black hole could enable time travel by exploiting time dilation.

The relationship between faster-than-light travel, wormholes, and the possibility of moving backwards in time.

Discussion on the paradoxes of time travel, including the grandfather paradox and its implications.

Creative ways to prevent historical events without resorting to violence, by disrupting ancestral meetings.

The potential for minor changes in historical events to lead to the emergence of different individuals, despite major events possibly unfolding similarly.

Hypothetical communication through time using tachyons and its paradoxical consequences.

The philosophical and practical challenges of encounters with one's future self as depicted in time travel movies.

The implications of the grandfather paradox for the feasibility of backward time travel and its representation in fiction.

The concept of time as a dimension and the human experience of being 'prisoners of the present,' transitioning from past to future.

Speculation on the nature of higher dimensions and their potential to offer access to different points in time as if they were spatial locations.

The philosophical and scientific intrigue surrounding the ability to alter events in one's timeline if it were accessible in its entirety.

Transcripts

[Music]

if controlled backwards time travel was

possible today where do you think your

matter or information would travel and

no I'm not talking about what time do

you want to travel though the answers

are but rather if you were in a third

position third person position observing

someone traveled back in time what do

you think is would look like so the time

travel itself if you were the Observer

what would you see if you were able to

observe the timeline itself so I like

that but also just slipped in there

Brian was some mention about information

yes and and that links to entropy I

presume so if you can tackle both of

those in the next 90 seconds before yeah

so so look I think the only the only

real way to answer that question is to

commit to a version of time travel to

the past and the version that I find

most convincing involves

wormholes and the idea of a wormhole I

think many people know this idea it's a

tunnel from one location in space to

another location pays a kind of shortcut

and if you move those openings relative

to each other or you put one near a

black hole again there'll be a time

difference between the two openings so

now one opening is ahead one opening is

behind so you go through the tunnel One

Direction you go to the Future you go

through the tunnel the other direction

you go to the past so what would going

to the Past look like somebody would

enter the opening of a wormhole and they

would disappear and they pop out the

other opening of the Wormhole at a

different place at a different time and

so in the Marvel in the Marvel Universe

where you have Doctor Strange opening

these portals he's only moving through

space he's not actually moving through

time so that's a that's a lost

storytelling element there that they

could totally do interesting things with

it seems to me yeah yeah I mean the

richness of wormholes really arises when

you have a time difference between the

two openings I mean it's fun to have a

tunnel through space but it is

mind-blowing to have a tunnel through

time yeah and also I would add that I

think I can add correctly Brian that as

portrayed in the movie uh contact where

jod Foster goes through this we presume

is a wormhole to get to to visit the

aliens and then she returns we like the

idea that it's like a water slide you

know you're in this tunel you're in this

tube and you're you're sliding and there

but it's really just a simple hole you

step through it right it's not some

Journey isn't that correct because

they're in they're they're basically in

the same place uh they can be but you

can also have situations where the

throat of the Wormhole has some length

to it and then again it would just be

traveling through space it wouldn't be

some kind of like you say water slide or

some kind of weird thing that was

happening but uh but you're right okay

so all right so if you're going to do

this at least and report on it you if

you're in a wormhole and it's propped up

nicely and it's safe for you then you

you're just moving through space

backwards in time if the opening of that

Wormhole is near a black hole where time

is ticking more slowly than where you

came from or if it was there for a while

once you set the time difference between

two openings you can then move away from

the black hole because the time

difference will then

persist wow

Jesus oh yeah so what a wormhole enables

by the way if you manage to travel

someplace faster than light you have the

capacity to move backwards in time

that's we've got that one established as

well we just don't have any easy way to

travel faster than light but one one way

that's been celebrated in science

fiction and you can write it out on

paper legitimately is a wormhole a

wormhole I'm over here and I want to get

over there and I want to get there

quickly I want to get there before the

end of the commercial break okay so you

can travel through a wormhole that

changes the effective distance between

where you are and where you're going and

then you sort

of look around when you get there and

you find oh my gosh I've traveled

100,000 light years in a matter of a

moment okay when you do that you have

the capacity to move backwards in time

relative to when you left now you don't

get to visit yourself you're in a sort

of a different uh SpaceTime trajectory

so you can't shake hands with yourself

before you left that so if that's what

you're thinking of doing no and by the

way there's a huge there's a huge

Paradox that people worry about and and

many people including Stephen Hawking

the late Stephen Hawking worried whether

this paradox would

prevent backwards time travel completely

because if you go back in time and

prevent your parents from meeting one

another then they wouldn't have ever

given birth to you to go back in time to

prevent them from meeting one another

first of all let me just say I stopped

listening when you said I can't shake

hands with

[Laughter]

myself so if there were a rule book of

time travel

um the number

one

item would be you cannot go back in time

and prevent your parents from meeting

each

other because then you would have never

been born to have gone back in time to

have prevented your parents from meeting

each other this is the fundamental

Paradox of time travel and so that if

there were a rule book that'd be number

one rule so here's the thing so yes you

wouldn't have a Terminator movie if the

terminator's sole job was to prevent

Sarah Connor from becoming

pregnant okay that's a different movie

from killing systematically every Sarah

Connor in the phone book right so and he

wouldn't have to do that he could go one

generation earlier and prevent the

grandparents from eating or prevent the

great-grandparents from eating or the

Great great great parents mean anywhere

in that genetic chain if you disrupt it

then you are not born and so could

introduced the great great grandmother

to a much better looking

guy and you just have a better looking

time traveler going there go like I'm

considered Michael B

Jordan he's very

attractive

that's a different Terminator movie

right

exactly so so I'm just saying these

people think they're on some locktite

theme when the theme is way broader than

that in fact uh forgive me for not

remembering which movie this was it'll

come to me in a moment where they

realized that if two

people if if two people had sex 10

minutes later

than they otherwise did then a different

sperm fertilizes likely the same egg and

that's but it's nonetheless a completely

different person wow so even if you

don't disrupt the sex just delay it make

the train come a little later make the

you know uh have the the cup of coffee

be extra delicious so they get a second

cup before they or or the wine whatever

is the Romantic forces operating that

evening or just make sure they have

other kids cuz that will stop you from

ever being able to do it

again five other kids running around

house all you got to do you know it's

just like I mean that's what I found out

during the pandemic you know you you in

the house you be L man we've been here

for a while what are we going to

do every time you try to disappear they

show right up knocking on the door what

are you guys doing what's going on in

there okay so that's a time traveling

movie Never Never conceived see what I

did there very ni see what you did there

it's you trying to prevent the parents

from having sex they're not having not

having it anyway that's it because they

got five kids running up and down

bouncing off the walls got the other

kids just like no in popular pars it's

called the grandfather Paradox but it's

a paradox to any one of your ancestry

because disrupting that chain will

prevent you from being born someone else

could be born now now you can you can

get you can introduce a more interesting

idea that

maybe the forces of the

timeline care about major

events even in spite of you changing

minor events that'd be an interesting

fact right I I I I don't really agree

with that idea but it' be an interesting

sci-fi so is that kind of like

inevitability so it's like even you

change these minor things the inevitable

will still happen correct so it could be

that you know you killed the the some

ancestor of yours so you don't

exist but somebody else arises in the

life of the other partner because you

just have to kill one of the partners

right that creates some other person who

basically does exactly what you were

going to do in your life right so so

it's not you but the larger scale events

still unfold and my favorite example of

this which involves no killing at all is

if you could communicate backwards

through time we have a hypothetical

particle that does that you know what

it's called you ever hear no it's called

the tachon oh tachon okay tachon and

it's I think it's from the Greek tacos

meaning fast tachometer that's the same

route a tachometer which gives you the

the the the speed of your engine uh if

you still have an engine car yeah yeah

the RPMs that's a tachometer so we have

this hypothetical part it's never been

observed but we sort of introduce it

it's called a

tachon it exists moving faster than the

speed of light and as you may remember

Chuck as you go faster and faster and

faster your time slows down relative to

everybody else right at the speed of

light time stops but what happens if you

cross the speed of light then time goes

backwards according to the equations so

we are imagining if you could ever

accomplish this time would go backwards

for you so we introduced this particle

it's called tach on so now you have a

tachon texting smartphone okay and your

buddy's walking down the

corridor and you see your buddy slip on

a banana peel and fall and you say I

don't want my buddy to slip on a banana

peel and fall so you pull out your tach

on text message service and you say

watch out for the banana peel you send

it to them after this event has already

happened but they receive the text

before it happens right okay you got

this because it moved backwards in time

right okay so then what happens is

they're walking down the

corridor and then the text

alert happens okay so they pull out

their smartphone and start reading the

smartphone and it says watch out for the

banana peel but the very fact of having

pulled out the smartphone and looked at

it meant they weren't looking down in

that moment and they slip on the banana

peel and they slip on the peel so you

caused the very event that you thought

that you were avoid uh preventing

correct

correct um let's start out with with

Looper so let me just give the plot line

you are an assassin who kills bad guys

who was sent into the past thereby

disappearing from the future and then

you kill them and dispose of their body

so they're basically wiped off the face

of the Earth as anyone in the future

would know or concern and then you

confront yourself as someone you're

supposed to kill brilliantly played by

Bruce Willis and then there's an issue

there about whether you kill your future

self or not and that's all I'll say

about in case anyone hasn't seen it but

my point is is you have an encounter

with your future self and this seems to

break some some time travel uh rules I'm

I'm thinking to myself are there time

travel rules though

I'm you got

me Joe I thought I could pass that

through you but I

couldn't no but I'm actually I'm curious

to ask you cuz I'm a fan of time travel

movies so you know like I mentioned Back

to the Future or you know what want to

talk about Quantum Leap I was in an

episode of Quantum Leap when I was 10

years old the

old um but time wait a minute wait wait

wait and weren't you forgive me I

weren't you in in Third Rock yeah yeah

yeah oh my God this that's right

speaking of a cosmic perspective right

you were a kid third walk from the Sun

with oh just just remember that right

it's not in my notes here so I I I just

remembered that so you've been at this

for a while oh I've been doing this a

long time feeling good about this okay

so so uh I don't know if there's a rule

we'll have to ask some of our time

travel would would that kind of thing be

possible I mean is there any any

indication in any serious science to say

that a human could travel from one place

on the time continuum and end up in a

different place intact with their same

human body and brain and yeah I think

there's not that itself is not the

problem the the problem comes about with

as they say the grandfather Paradox

right where you go back and you prevent

your grandfather from meeting your

grandmother or in a Terminator version

of that you kill your grandfather so

that you're never born to be sent back

in time yeah to meet your grandfather

okay or or some so there's a paradoxical

Loop problem yes that uh that Steph

Hawking thinks there was not there is no

solution to it at all that we will

discover a new time travel conjecture

that will prevent backwards time travel

in that way and there a couple of

scenarios and there's another one wait

when you say a conjecture you mean that

there'll be some kind of evidence or

kind of mathematically

backed uh statement that says this is

actually impossible it'll never happen

Stephen Hawking believed that we would

one day derive either mathematically or

experimentally that conjecture just so

as to prevent the grand father Paradox

from unfolding right and so but what was

what's what intrigues me in loer you met

your future self 30 years hence yes and

and had conversations with that person

and that's just I don't I don't know if

that's allowed that's all I'm saying

yeah and I don't know what to say yeah I

mean I think it's definitely not allowed

and look at that we did it anyway okay

we got no but I mean there's there there

was actually there was a scene there's a

great scene one of my favorite scenes in

the movie where my character and Bruce

Willis's character who like you're

saying are supposed to be the same man

just younger and older version of the

same man they sit down at a diner

together and talk and there was a

version of the script where the older

man explains some of the mechanics of

the time travel oh

probably in a you know in in terms that

Stephen Hawking would deem serious but

at least in terms that felt necessary to

the story in that draft of the

script but later Ryan in what I think is

a wise move decided to cut all of that

out and there's just a line now where

Bruce Willis kind of gets prickly and

angry and says we're not going to talk

about time travel oh okay

so all right so you leave it more to us

to try to think about

it you don't want to have loops in space

and time in which you can't have cause

and effect be logically consistent right

so we're all used to things in the past

affecting things in the future but if

time loops around then the future

actually can affect the past so the

danger in ether and one of the

Diagnostics we use to see if e theory is

healthy is to make sure it doesn't have

any of these closed Tim likee Curves in

which cause and effect would be muddled

up by the structure of SpaceTime this is

a philosophical bias you are

implementing on the universe itself it's

a little bit more than philosophical

because you want the unfolding of events

to be internally consistent you're

saying you want something to be true in

the universe that sounds like you're

begging for let me just say God needs it

to be that way right because if the laws

of physics yield inconsistent results

then everything falls apart everything

no we just live in an inconsistent

Universe problem with that no no what it

means is our understanding is messed up

clearly the world makes sense no I used

to believe that I take it back now do

you think one day we'll have a machine

that'll just send us forward in time we

know it's possible but why don't why

aren't we doing it active well I think

we do have a machine in principle right

we just can't go very far forward in

time because every time you go into a

vehicle and you undertake a round trip

Journey you are traveling into the

future by some calculable amount yeah

now at ordinary speeds you're only going

you know a billionth of a billionth of a

second or something like that into the

future into the future but if you found

yourself in a ship that was going near

the speed of light you go out for 6

months you turn around you come back for

six months you get off that ship you

will have aged one year but depending on

how close to the speed of light you got

when you step off the ship Earth will be

10,000 years or a million years into the

future you will have jumped into Earth's

future and that is what we mean by time

travel the faster you go to the speed of

light the slower time moves correct so

somebody on a spaceship would age slower

than somebody on Earth they'd come back

one year later and the people on earth

have aged 10 years 100 years something

like that that's the basic idea that's

the idea and and let me add just to

close out this segment our GPS

satellites orbit high enough so that

there's a measurable and important

difference in its rate of time that it

keeps compared to us here on the surface

of the Earth they're farther away from

the source of gravity Earth so their

time ticks faster than our clock time on

the surface and we know this it's

Einstein's general theory of relativity

so they calculated how much faster their

clocks would tick and they back correct

for that before it sends us the time

that ends up on our

[Music]

smartphones oh yeah so this this one

this next one is from uh Google Plus

like even better I never met Google Plus

even better than Google just a little

bit better so Mr plus ask a little more

charged a little more charged um this

question comes from Frasier Kane of the

website Universe today and it's a

question I've also wondered many times

doesn't the fact that there are no time

travelers now prove that time travel

will never be invented in the

future yeah that's an excellent point

and I've always thought about that

because I said to myself in fact if you

watch the TV the CBS sitcom The Big Bang

Theory uh in the roommate contract

of I know you got to be totally

uh in the roommate contract that

stipulated that

if if I'm getting the details of it

wrong the sense of it is right if

they'll still be very excited if any one

of them invents a time machine in the

future they have to go back to that

moment that they're reading that phrase

in the roommate contract to show up in

the room and so so they're going through

the

contract and then they pause for a

moment no okay we have you know you're

not the one who invents the time machine

in the future that's the ultimate like

let agree to me back here 10 years from

now but it's at the same time it's

awesome exactly and so I think that's a

that's a pretty good argument and I

don't have a rebuttal to that but know

what if people are hiding it what if

people have come back but are not

telling people for some reason because

they don't want to give something away

there's a quote I think it was from R

doll but others perhaps have said it

that the only secret that can be kept

between two people is when one of them

is

dead so I'm pretty sure that if a Time

were out there people would have figured

that one out it's been rumored that the

the reason why the Titanic sank is

because in the future they invented a

time machine and everyone wanted to go

back to the Titanic to see the iceberg

when it hits and then it overloaded the

Titanic and it sank right oh well now

I'm convinced so there's the evidence

you're looking for evidence go that's

hard hardcore evidence so uh that's a

pretty good one yeah and it may it might

be that your time travel machine can

only take you into the future and then

you don't have these paradoxes of

killing your grandmother and then you're

never born to go back to the future

stuff yeah yeah exactly because there's

a movie too coming out called Looper or

Loopers that with Joseph Gordon L and

Bruce Willis and he goes back in time

he's like an assassin that goes back in

time and he goes back and he's scheduled

to kill himself so he has to like figure

out what to do about it you know what's

interesting all these TV shows they have

people going back and killing people all

you have to do but all you have to do is

pick a time where two of your ancestors

who mated produced one of your ancestors

and all you have to do is prevent them

from mating you don't have to kill

anybody just just just your great great

great great great grandparents prevent

him from meeting you would have never

been born that's

all in interstellar they had Matthew

mccon interacting with his timeline so

the premise was you go into a black hole

and you have access to these higher

Dimensions but starting back in ordinary

life we have three dimensions that we're

familiar with on a grid you might think

of it as what street in New York what

street what Avenue and what floor in a

building that you might meet someone

these are three coordinates that you

would give remember however that anytime

you've ever made an appointment to see

someone not give a time without a place

nor would you give a place without a

time so the actual coordinates to meet

someone require four numbers basically

four coordinates three space coordinates

and one time coordinate you never said

to your friend I'll meet you at 10:00

tomorrow

where you never say I'll meet you at the

corner 33rd and

third

when we know intuitively that we need a

space and a Time coordinate combined in

order to have life unfold in any

meaningful way so the idea that we live

in four dimensions should not be

surprising to people we take it for

granted actually actually but the

difference is that we are not prisoners

of our three-dimensional space I can

walk left and right I can jump up and

down I can walk forwards and backwards

and I can repeat that I can access all

points of my three-dimensional space yet

I am a

prisoner in the

present forever transitioning from the

past into the future I have no access to

the past I have no access to the

Future and so

if you go to a higher Dimension it's not

unrealistic to think that you step out

of the time

Dimension and now you look at time as

though we look at space so very

questions that we have very statements

that we make about our lives make no

sense in that higher coordinate

system you can ask when was I born well

you always born when did I go to college

you're always going to college when did

I die you're you're always dying and so

if your whole timeline is laid out in

front of you then you have access to it

and you can jump in at any point relive

it uh we don't know yet if you can

interfere with events that quote have

already happened if your whole timeline

is just already there what does it mean

to jump into it and then change

something if it's already there so these

are fascinating questions that make

great fodder for science fiction stories

and we don't know what's in a black hole

so take it and run with it

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