PHIL105 - 2008 Time Travel Dan Turton

8/7/2019 PHIL105 - 2008 Time Travel Dan Turton

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Time TravelL1: Introduction toTime and Time Travel


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Apologies

This lecture owes a lot to youtube.com

Visuals are very useful when trying to

understand 4-dimensions


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Afraid of the Dark?

Who remembers trying to race against

light so you could get in bed before it got

dark?

Turned out light was really fast

If only we had a time machine


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Proof of Time Travel

Theoretically, the indeterminacy of sub-

atomic particles could create very strange

effects on our level possibly including effects that could

allow time travel

and heres the proof!


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Einsteins Great Idea

The speed of light is constant(ly very fast)

If we had very fast spaceships, this would

allow us to observe some crazy things For example

The twin paradox

But we dont need a spaceship A regularpassenger jet will do

Or even just a tower! (Visual explanation)


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Backwards Time Travel

Going forward in time is (relatively) easy

Going back is much harder

But Einsteins theory of general relativity

seems to allow it

It depends just how much space-time cancurve


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Making a Worm Hole

Black holes warp space-time a lot because

of their intense mass

Flying a spaceship through one would bepretty risky

And, who knows where it would take you

even if you could make it through

But, there may be a more convenient

way


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Dr Ronald Mallett

Mallett thinks that light can warp space-

time too

Hes currently trying to get funding to see ifhis time machine will work

Previous video

Coffee analogy


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Possibilities for Backwards Time

Travel Malletts light machine

A naturally occurring closed time-like loop

in space-time

A visiting alien race with a time machine

on board their ship


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Being Specific about Time Travel

Actually going to the future orpast

Not just some replica of it

Its all relative

For me to time travel, there would need to

be a difference between the speed timepasses for me and the speed time passes

for someone or everyone else


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What is Forward Time Travel?

Forward time travel: my time goes slower

than yours (like aging slower than

everyone else)

My time goes slower than yours as my

speed increases (relative to yours) and/or

if I am closer to mass than you (and if that

mass increases)


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What is Backwards Time Travel?

What: to me, it seems like yourtime is reversing into our sharedpast

How: space-time (where I am) iswarped so significantly that itcreates a closed time-like loopor wormhole to our shared past

The loop allows me to travel

faster than the speed of light(not absolutely, but relative toourpast as we know it or youwatching me go through it)


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A Closed Time-Like Loop


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This is not a Physics Course

Dont worry if thats

confusing

the exam questionwill be based on the

logical paradoxes of

time travel

Any questions onwhat time travel is?

(Not how to do it on

a student budget!)


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Take-Home Lessons

Time is not like what it seems

If you have an assignment to do, youshould do it on the top floor of the libraryinstead of the bottom because youllwork faster! (As long as you can get thereand back quickly)

To stay young-looking compared to yourfriends, make sure you take more long-haul flights than them!


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Next Time

Read

The Case of Jocasta Jones p207

By Jonathan Harrison

Get ready to discuss

Some logical paradoxes of time travel


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Time TravelL2: The (Easy)

Paradoxes of TimeTravel


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Time Travel is Possible!!!

This might be a hoax, but time travel really

is possible

In fact, many of us have already done it


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What is Time Travel Again?

Actually going to the future orpast

Not just some replica of it

Its all relative

For me to time travel, there would need to

be a difference between the speed timepasses for me and the speed time passes

for someone or everyone else


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What is Forward Time Travel?

Forward time travel: my time goes slower

than yours (like aging slower than

everyone else)

My time goes slower than yours as my

speed increases (relative to yours) and/or

if I am closer to mass than you (and if that

mass increases)


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What is Backwards Time Travel?

What: to me, it seems like yourtime is reversing into our sharedpast

How: space-time (where I am) is

warped so significantly that itcreates a closed time-like loopor wormhole to our shared past

The loop allows me to travel

faster than the speed of light(not absolutely, but relative toourpast as we know it or youwatching me go through it)


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This is not a Physics Course

Dont worry if thats

confusing

the exam question

will be based on the

logical paradoxes of

time travel

Any questions onwhat time travel is?

(Not how to do it on

a student budget!)


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The Case of Jocasta Jones

Follow the story and keep your eye out for:

Weird happenings

Illegal acts


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The Case of

Jocasta Jones

Jocastas 2000

Jocastas 2001Jocastas 2019

Jocastas 1900?Jocastas 1910?


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Fathering Yourself is Impossible

How is it possible for someone to be their

own father??


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Fathering Yourself is Backwards

Causation

To father yourself, you would have to

procreate with your mother, but that

probably requires a few shots and

backwards causation doesnt it?

Surely it would be causing a change in the

past, which is impossible!

The past has already happened, so how can

we change it?


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Backwards Causation

We normally think of effects as followingtheir cause

Study (usually) causes the effect of a goodgrade

The history ofEurope has caused the bordersbetween nations to be recognised as they aretoday

But, if you father yourself then the effect ofthat procreation is also the cause!

Like getting a good grade causing you to havealready studied!


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The No Destination Objection

If you havent thought through all of the

implications of 4-D space-time, then you

may still believe:

That the past no longer exists That the future doesnt exist yet

That only the present time exists

If these points are true, then time travel isimpossible because there is no other time to

travel to


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Reply to the No Destination

Objection

4-Dimensional space-time

It only seems like the past and future dont

exist because we are not aware of them We: the event that is our consciousness at this

current time and place in 4-D space-time

4-Dimensional space-time is widely

accepted in physics and

Einstein came up with it


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Time Discrepancy Paradoxes

If you missed the first lecture, you may stillbelieve:

That time or the passage of time is a constant

That time passes the same for everyone andeverything everywhere

That Newtonian or absolute time exists

If these points were true, then time travel is

impossible because it involves differences inhow time passes between the time travellerand everyone else


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Reply to the Time Discrepancy

Paradoxes

4-Dimensional space-time

It turns out that time (and the spatial

dimensions) are relative Time is not fixed or absolute or constant

The speed of light is constant, but time is

relative to speed and proximity to mass

Physicists have proven this and

Einstein came up with it


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The In Two Places at Once Paradox

No one person can whollybe in two places

at once

Wholly is important here

If you believe this, (which you should) then

doesnt that mean time travel is impossible?

(because it would allow you to go and wish

yourself many happy returns at your lastbirthday party)


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Visiting Myself

Me

existing

through

space-

time

My last

birthday

party


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Take-Home Lessons

If you time travel into the past, avoid yourparents at all costs

Newton was very smart, but he was wrong

time is not a constant The past exists and part of us (and parts

ourparents) currently exist in the past

So, assuming yourparents had at least onecool moment in their lives, they are, in a way,still partly cool


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Next Time (+ Exam Tip!!!!)

Read

The Paradoxes ofTime Travelp208

By KenP

erszyk & Nick Smith

Get ready to attempt to solve the logical

paradoxes of time travel, including theGrandfatherParadox which will be very

useful to know for the exam


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Time TravelL3: The (Hard)

Paradoxes of TimeTravel


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Time Travel is Possible!!!

John Titor came from the

future and provided truth

(available on youtube and

at www.johntitor.com)

This might be a hoax, but is backwards

time travel really possible? Physicists say that it is but what about

the logical contradictions that would result?


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The Paradox of Changing the Past

If you could go back in time, you could domore study for the test and get a better mark

But, you already have a mark! You cant

change it its part of history now! P1) If time travel is possible, then you could

change the past

P2) It is neverpossible to change the past C) Therefore, time travel must not be

possible


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Replying to the Paradox of

Changing the Past

Denying P1: Time travel is possible, but itdoes notand cannotchange the past

When you time travel, you create a new alternate

universe So you can change things, but not things from the

past in our universe

When you time travel, you can affect the past

because you already did You dont change history you had already affected

it!

An accurate history book would already have a recordof you being there!


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J t 2000


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The Case of

Jocasta Jones

Jocastas 2000

Jocastas 2001Jocastas 2019

Jocastas 1900?Jocastas 1910?


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Jocastas Son/Husbands Lifeline

1900 1910

1980 2000 2019

JocastaThe guy

The guy dies

The guy is born

Jocasta is born


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The GrandfatherParadox

If you could go back in time, you could kill your grandfatherbefore he could produce any offspring

But, if you did that, then there would have been no you tomake a time machine and go and kill him!

Which means that you cant have killed him


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The GrandfatherParadox (Cont.)

P1) If time travel is possible, then you could

kill your grandfather (before he had kids)

P2) It is impossible for you to have existed ifyou succeed in killing your grandfather

(before he had kids)

C) Therefore, time travel must not be

possible


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Replying to the GrandfatherParadox 1

Denying P1: Time travel is possible, but youdo not and cannotkill your grandfather

When you time travel, you create a new alternate

universe

So you can kill some old guy but its not your

grandfather (not from yourpast)

But does time travelling to an alternate universe

really count? Is it time travel or inter-universal travel?

For time travel to be meaningful does it have to be to

our own past?


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Denying P1: Time travel is possible, but you

do not and cannotkill your grandfather

When you time travel, you can affect the past,

but only because you already did

This works in the Jocasta Jones case, but

This justification doesnt work this time

E.g. If you had already been there and killed your

grandfather then you would never have existed


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DenyingP

1: Time travel is possible, but youdo not and cannotkill your grandfather

When you time travel, you can attempt to kill

your grandfather, but you will never succeed


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OK Fine, but where are the Time

Travellers, then?

P1) If time travel ever becomes possible in

the future, then time travellers would most

likely have visited ourpast already P2) But there is no evidence of time

travellers in ourpast

P

3) It is very unlikely that the time travellerscould have left no evidence

C) Therefore, its very unlikely that time

travel ever becomes possible


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Replying to the No Evidence of Time

Travellers Problem 1

Accept the argument

Its true that there are no time travellers but

only because: Global warming, or

Nuclear war, or

Super-viruses, or

The robotic uprising of the (very) late nineties killed off all of the humans before we got

around to making time machines!


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Denying P2: There is evidence of time travellers!

John Titorwww.johntitor.com

That guy who went under his sink (Hakan Nordkvist)

www.youtube.com/watch?v=E2sp-clMk8s&feature=related That mullet guy


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Denying P1: Only when time travel becomes

possible (by a human creating and turning on

a time machine a closed time-like loop)

would we expect to start seeing things

appear from the future (recall what Dr.

Mallett said)

So, we wont expect to see anythinguntil the firstclosed time-like loop is set up


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Take-Home Lessons

Time travel in movies is usually illogical, but

Time travel is theoretically and logically possible

in real life

But if you have homicidal intentions towardsyour ancestors

then make sure that you look out for banana

skins


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How to Find out More

Want to know more about time, time travel and

how they impact on other topics from this course

(like free will)?

Enroll in the metaphysics course next year (orthe year after): PHIL225/325

Keep up with the latest science news

C.E.R.Ns L.H.C. (Large Hadron Collider)

http://lhc.web.cern.ch/lhc/

Dr. Ronald Mallet (real time machine maker)

http://www.physics.uconn.edu/~mallett/main/main.htm


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PHIL105 - 2008 Time Travel Dan Turton