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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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Replying to the GrandfatherParadox 2
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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Replying to the GrandfatherParadox 3
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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Replying to the No Evidence of Time
Travellers Problem 2
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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Replying to the No Evidence of Time
Travellers Problem 3
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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Next Week