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Time-travel Paradoxes!


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If you went back in time and visited your granny during her ninth birthday donít kill her! Because if you put a gun to her head and pull the trigger she could not have given birth to your mum. YOU certainly were never bornÖ

Therefore you could not have killed anyone as you never existed. Now this means your granny couldnít have been killed by you. She didnít die nine years old. This permits you to be born. 

If you were born could you go back and kill your granny? No, not your real granny. This general idea has been used in Back to the future. Marty nearly stops himself from being born when he prevents his parents from falling in love.

Solving The Problem
1, You simply canít change history meaning if you go back in time you have no free will(as shown in Twelve Monkeys, Crime Traveler etc. Events will get in your way if you try to kill your granny. YOU CANíT DO IT.

2, When you so-called change history youíre actually moving up a different branch in time into another universe. The previous universe (where you were born) still exists. When you fire the gun youíre really killing another version of your grandmother.

3, Any actions you make in the so-called past has no affects on the present. Itís a different time-line universe.

The laws true solutions donít present real time-travel as you go into another world.

We canít simply use the grandmother paradox to rule out time-travel claiming it causes logical inconsistencies. We need to look at all the possibilities.

How could we build a time machine?
The mathematics of general relativity suggest that under extreme conditions space-time might become so warped it would be possible to travel back in time. There is also the possibility of tunnels in time created by negative mass.

Very long rotating cylinders of matter-proposed by Frank Tipler

Kerrís spinning blackholes-since most stars spin this becomes worth looking (proposed by Roy Kerr).

Cosmic strings-(as Richard Cott suggested)

Travelling faster than light Ė would take us back in time(as suggested by solutions to relativity). Wormholes might allow us to outpace light (if you walk through the short cut quicker than light through convential (normal) space.

Tachyons -are sub-atomic particles which always travel faster than light and therefore move back in time constantly. They have not yet been found and remain hypethical.

Contracting Universe- Time might then be running backwards but since everything else also would itís unsuitable.

Macro-wormholes(Kip Thorne showed how we could use it as a time machine).

time - paradox

Grandfather paradox
Suppose you could go back in time, lets say several decades and found your grandfather when he was two years old. In his house you could grab a knife and stab him to death. He doesn't get the chance to have children with your grandmother. Therefore either your mother or father doesn't get born. Your parents can't give birth to you because one of them don't exist. You could never have been born and don't even exist. But could your grandfather have been killed by someone who doesn't exist? He must have lived through his childhood. This would allow you to exist if this is the case. Seemingly you can go back in time to commit the murder if you are born but then you would never have been born. And so on and so on. This situation is not consistent with itself. It doesn't make sense and can't possibly happen.


1, You simply can't change the past. Time will stop you limiting your freedom while you're in the past from your point of view. This puts the concept of freewill in serious danger especially if you tell people what's going to happen to them in their future. If you believe when you go back in time you are from one possible future from everyone else's point of view they can simply go up any root in time they want. 

According to quantum physics Many Worlds theory there are a huge amount of universes where every possibility occurs between them all. In some you're the opposite sex. In some you won the lottery etc.

You might be heading towards the universe you originally came from before you travelled back in time. Everything will happen the way you remember it. But all the people you meet are free to decide what they want to do and enter a different universe. Since it's not possible for you to be there you disappear from their lives. Meeting a time traveller from your future could therefore be very strange. 

2, A parallel universe might be created when you seem to change the past. Imagine if time itself was just like a tree. The different branches show different ways events could have happened. Every time we decide to do or not to do something time splits. Even if we are not aware we decided something it have affects. Quantum physics reveals a many worlds theory like this.
Since this parallel universe is not really your past (despite it's first appearance) anything you do there does not affect you. You can prevent a version of yourself from being born because you are not really related to anyone there. They just look very like your family and friends. You are not home! You may be somewhere that looks like the place you live but a different universe in quantum physics is a completely different reality.

3, No matter what you do in what is really a parallel universe you will do back to your previous universe which is not affected by your previous actions. A space-time wormhole could lead you back to your original unaffected universe.

What came out of the wormhole if the ball never went into it?

Another common example of a paradox is a ball that goes through a wormhole connected with a moment in the past. Therefore it comes out of the other space-time wormhole mouth actually before it went in! Then what might happen? If the ball then hits it's younger self out of the way of the mouth then it never goes in. But if the ball never did go in the wormhole then how can it ever come out. The existence of the older version of the ball is destroyed i.e. it never falls back in time. But then this version certainly can't hit the younger version out of the way. So it must go into the wormhole as a collision with it's older self is evidently the only force that could and did stop the ball from entering the wormhole. This of course is unexplainable and is logically inconsistent.

But the situation could happen differently to allow it to become self consistent.

1, What if after the ball comes out of the wormhole at an earlier time it does hit it's previous self but this collision is what makes the ball fall into the mouth in the first place! It hits the other version into the mouth. This would imply that the past or present is affected by the future. In fact in this case the past is dependant on the future.

2, The ball might simply hit it's other self only slightly so the direction of the ball is not altered enough to cause a paradox.

3, The ball might just miss it's younger self.

Nature might protect time and prevent paradoxes. From theories and many stories it's clear that paradoxes cannot happen in the real world.

Other types of paradoxes
In the terminator movies John had something important to tell Sarah. Thank her for her help through the hell. Tell her not to give up or he will never exist.
Who wrote the speech?
John certainly didn't write it. He was told it since he was a kid from Sarah who could remember it. Sarah just recalls what Kyle told her in 1984. Kyle just remembered what John told him to say.  
No one wrote it. It exists somehow but not by John, Kyle or Sarah being creative. No one had to write it because it was created by the affect the future on the past had on each other.

If I in 2000 study the history of work done in a private factory and learn about the development of a time machine! Their scientists worked from designs and plans noted in a book (never published)they used. They had no idea how to achieve such technology until they read it.
Then to experiment with temporal(time) paradoxes I am sent back to 1983. The entire building has not even been built as I arrive. Later accidentally I meet one of the scientists and talk to him. When I hear how excited he is I hand him that book which he uses future success. The answers! He is more than willing to read and use the book.

But who came up with the idea of how the time machine is built?
Not any of the scientists as they just followed instructions in that book.
Not me as all I did was hand a scientist a book. Noone actually wrote the book and no one had to work it out.

Is this allowed by physical laws?
Noone really knows...

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There is no grandfather paradox in the multiverse scenario. In a multiverse, your grandfather's multiple histories included many in which he was not murdered and many in which he was murdered.

Those many histories in which he was murdered included some involving different male or female murderers who killed him. It's possible that you were one of those murderers in one of your previous lifetimes or incarnations.

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Paradox can't hold a candle to "twinadox". Thats when you time travel back and MARRY your gradndmother and become your own grandpaw. What if you had a twin brother and the THREE of you all show up one day, wich one is the other you? How do you know that there shouldn't be four of you and somebodys missing? Cheesh man!! I'm going to get some sleep, and try not to read this thread next time...er wait a minute, on the other hand.........the me in a paralell reality may infulence me to change my mind.............

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Let's get away from travelling to the past for a moment. Let's look at what was made popular in Back to the Future pt 2, where Marty sees his son, or his girlfriend sees herself.

It cannot happen! If you left time, you would be considered 'missing', or dead. The truth is, you don't exist from the point in which you lept forward in time. You therefore cannot see yourself, or your son, because you stopped existing at that point in the past where you left.

Is this a proper paradox? Is there any reasoning I am missing that says you can see your future self?

Look forward to responses.

1.21 Jiga-watts

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True. If you leave this time, you will not be here until you return. But, if you are aive in the future as you were alive in the past, then you could visit yourself because you are there. Your present self is different from your past or future self. This definitely applies to the past because you know you lived in the past and if you can go there, then you can visit yourself.

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I think there is two ways to look at this Jiga Watts. The first one is where you can actually change the past so it effects the future. If you were presumed dead in the future, then you could go back to the time right after you left and nothing would have been changed. However if you leave again, it will just be the same as before.

The second one is where you can't change the past, and you'll only be creating a parallel universe. What used to be your future is now your present, and since what used to be your present is now your past, you can't change the past, so you'll still be presumed dead at when you left off. And so you can still go back in the past and live there as usual, you won't be changing the future.

I think that's how those theories go.

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It is very interesting what would happen if you left the present and reached the future. In The Time Machine the time travelers asks about himself and people claim he went missing when he left on his journey through time.

It seems like an BTTF2 Marty was taken away in 1985 so his kids and everything couldn't exist in 2015...

But the existance of his kids might just be evidence that they will later return to 1985 to do all those things! This would imply that everything they are going to do have already been decided!

It became clear the the future is NOT set as Doc claimed the future hasn't been written yet. So how could they travel into what does not exist? Even when Marty went to 1955 he must have been from the future from some people's point of view?

The future they travelled to might just have been one possible future! In the quantum many worlds theory there are an infinite amount of futures where every possibility occurs...

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In response to 1.21 jiga-watts. If you go into the future and see yourself, then by rights you will succeed in whatever you are doing in the future, and make it back to the present. If you don't see yourself, then one could asume that you never made it back to your own time in the present.

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In some probabilities, you traveled to the future and made it back, in others you did not make it back. In some probabilities you are alive in a future time and in others you are not alive. A multiverse contains all possibilities and all combinations of possibilities.

If you can travel to the future, you can meet a future self or not, depending on which probable future you go to.

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Thank you all for your responses. It's a fascinating discussion, to be sure, and one that seemingly has endless possibilities.

I'm pretty set on the paradox I raised, however. It just doesn't seem possible that you can see your future self.

I'll check in every now and then. Continue in your hypothesizing!

1.21 Jiga-Watts

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Wow! Paul is right on the money. I was just about to give up hope on anyone knowing who Tipler or Kerr was on this worldline.

By the way, #2 is the correct answer and the basics for time travel start at CERN in about a year and end in 2034 with the first "time machine" built by GE. Too bad we can't post pictures or I'de show it to you.

No Problem!!......."Wherever you go, there you are, and I'll be waiting."

SRC="C:\Visioneer Documents\PT5.jpg" HSPACE="0" VSPACE="0" cellpadding=3

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Guess what? You can put pictures on Doc's board... we would like to see it.
here is the URL: http://pub2.ezboard.com/bmagisystems
Im sure he would be more than happy to post the picture for you. He is the moderator for the montauk section on this web site.
Look forward to seeing your picture!

[This message has been edited by pamela (edited 02 November 2000).]

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Time travel_0-
Iam registered on Doc's site.
you can send it to me and I will post it for you.and if you want you can always set up a new e-mail account and only use it once.
There may be a site where you could post the picture with no info but I personally don't know of any. because of what people would put up with no accountability.
any other info you give will remain confidential . besides your IP address is already logged on this forum when you post. I'll help you out if you want.or you could just e-mail Doc yourself Im sure he would put it up for you without registering.just explain the situation to him. I feel he is very trustworthy. Actually he posted someone elses picture annonymously that claimed he built a time machine. his name was "director". thats it.

[email protected]

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Questions for timetravel_0 with permission to post.

by the way can you tell me what it feels like to time travel? when you are
in the process of doing it what does it feel like and what do you see and
hear. you made mention that you had to get use to the fields. Do you see a
bright flash of light?

Interesting first question. The unit has a ramp up time after the
destination coordinates are fed into the computers. An audible alarm and a
small light start a short countdown at which point you should be secured in
a seat. The gravity field generated by the unit overtakes you very quickly.
You feel a tug toward the unit similar to rising quickly in an elevator and
it continues to rise based on the power setting the unit is working under.
At 100% power, the constant pull of gravity can be as high as 2 Gs or more
depending on how close you are to the unit. There are no serious side
effects but I try to avoid eating before a flight.

No bright flash of light is seen. Outside, the vehicle appears to
accelerate as the light is bent around it. We have to wear sunglasses or
close our eyes as this happens due to a short burst of ultraviolet
radiation. Personally I think it looks like your driving under a rainbow.
After that, it appears to fade to black and remains totally black until the
unit is turned off. We are advised to keep the windows closed as a great
deal of heat builds up outside the car. The gravity field also traps a
small air pocket around the car that acts as your only O2 supply unless you
bring compressed air with you. This pocket will only last for a short
period and a carbon sensor tells us when it's too dangerous. The C204 unit
is accurate from 50 to 60 years a jump and travels at about 10 years an hour
at 100% power.

You do hear a slight hum as the unit operates and when the power changes or
the unit turns off. There is a great deal of electrical crackling noise
from static electricity.

Pamela: 1. what are some of your memories of 2036?

Timetravel_0: I remember 2036 very clearly. It is difficult to describe 2036 in detail
without spending a great deal of time explaining why things are so
different. In 2036, I live in central Florida with my family and I'm
currently stationed at an Army base in Tampa. A world war in 2015 killed
nearly three billion people. The people that survived grew closer together.
Life is centered around the family and then the community. I can not
imagine living even a few hundred miles away from my parents. There is no
large industrial complex creating masses of useless food and recreational
items. Food and livestock is grown and sold locally. People spend much more
time reading and talking together face to face. Religion is taken seriously
and everyone can multiple and divide in the heads.

Pamela: 2. can you send me more of the manual?

Timetravel_0: I will considering it but I do not expect they are worth anything to most
people except as a curiosity.

Pamela: 3.what would happen if you would meet yourself on another world line?

Timetravel_0: It has always surprised me why that concept is so hard for people to imagine
and accept. Nothing would happen. The universe would not end and there are
no paradox problems that threaten existence. Temporal space-time is made up
of every possible quantum state. The Everett Wheeler model is correct. I
have met and/or seen myself twice on different world lines. The first was a
training mission and the second is now. I was born in 1998 so the other
"me" is 2 on this world line. There is a saying where I come from....Every
possible thing that can happen or will happen has already happened

Pamela: 4.How is this world line different from your own?

Timetravel_0: For starters....the fact that I'm here makes it different. I've also
noticed little things like news events that happen at different times,
football games won by other teams...things like that. I would guess the
temporal divergence between this world line and my original is about 1 or 2
percent. Of course, the longer I am here, the larger that divergence
becomes from my point of view.

Pamela: 5.Is the vehicle a jeep?

Timetravel_0: No...its a 1967 Chevrolet..

Pamela: 6.Are you having normal dreams right now? any out of body experiences?
drawing you to different times? Do you dream you wake up in other places
and other times?

TimeTravel_0: No strange dreams or other experiences. Everything is pretty much the way I
expected it.

Pamela: 7.are you able to control where you go or is it random?

Timetravel_0: Yes, it can be controlled. However, the distortion unit has operational
limits. Imagine your path through time is through a cone. The farther away
from the center of the cone, the more differences you will see in the world
line. The C204 begins to "break away" at about 60 years. This means the
level of confidence drops rapidly after 60 years of travel and the world
line divergence increases. In other words, if I wanted to go back 2000
years and meet Christ, there is a better than average chance I would end up
on a world line where he was never born. The computer units and gravity
sensors "record" your trip and you are quite easily able to return to your
point of origin. I am aware that research is being done on faster units
with more accurate clocks. I imagine that they will be able to go back
farther with a higher degree of divergence confidence.

Pamela: 8. are you feeling drawn back to your own time or are you stable in this

Timetravel_0: I'm not sure what you mean by stable. If you mean mentally...there are many
things that bother me here but being with my parents right now is important
to me. Physically, the only thing really wrong is the number of colds I

Pamela: 9.Are you able to go back to your own world line?

Timetravel_0: Yes.

Pamela: 10.how are you protecting yourself from radiation? it alters DNA if you

Timetravel_0: I'm not sure what radiation you mean. If you mean from the unit, you can
see it vents X-rays and Gamma radiation out of the rear. As long as you
stay away from that, you should be okay. I keep a radiation detector with
me to check my environment and make sure the unit isn't "leaking".

Pamela: 11.How long would you say that ultraviolet radiation lasts? about 10
and when you are in that light can you see anything around you or does the
light kind of "fill up" everything and that is all you can see at the

Timetravel_0: The light bending only lasts a second. Its like driving under a tunnel and
being in total black.

Pamela: 12.Do your people know where you are right now? Can you communicate with
do you have a biological implant?

Timetravel_0: No. They do not know where I am and I can not communicate with them.
Interesting idea though. From their point of view, I will return almost
exactly at the same moment I left. From their viewpoint, I will only have
aged more than expected.

Pamela: 13. after the flash of light is gone are you then in another time? what
does it look like as the new time unfolds? Is it just there? or does it
slowly come into view? does it fade in and out for a time?

Timetravel_0: While the machine is on. Everything is black. When the machine is turned
off, it is the reverse affect. It appears you are driving out from a
bridge. To tell you the truth, I'm usually sleeping when the unit turns off
but yes...it does appear that the world fades in from black.

Pamela: 14. what happens if the device messes up?
Do you end up in space? if it goes offline and shifts ? does a hole open

Timetravel_0: Good question!!! That one almost never comes up. The hard part of
traveling through time is not the bending of gravity but the plotting of
your course and holding to the basic "position" in your environment. This
is done through a system called VGL (variable gravity lock). Basically, the
unit takes a reading of the local gravity and samples it during the "trip"
in pulses. If the gravity is too far off, the unit stops or reverses itself
to the last sample period where the readings were correct. If there is some
sort of failure, the unit shuts down and drops out to where ever you may be.

Pamela: 15. what affects are caused on the immediate area where the gravity has
been distorted after you leave it and when you arrive? are there permanent
effects left on the land such as electromagnetic disturbances in that

Timetravel_0: Another good question!!! The only real physical trace is a large chunk of
ground missing from the point of origin and a large pile of dirt at the
destination. The gravity field surrounds a small portion of the earth under
you and takes it along for the ride. There is really no way around this.

Please feel free to post these if you wish.

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Pam, did you ask about going forward in time? Do you need an invite from a future traveler? Where did MR. 0 get the '67 chevy?

Bringing chunks of ground along with you as you casually rewrite the history of entire worlds? I guess thats why Docs' Delorian was fitted with levitation equipment, to make a fast get away from angry property owners having to fill and grade every time he time jumps.

TimeLine 2015; STOP THE PRESSES!! 3 Billion Killed!!! Oh the presses are already stopped? Now if he time traveled *before* the planet was pulverized it would be a bit more believable.

Does Mr. 0 work for GE? Maybe he owns some GE stock. Speaking of stocks we could all use a hot tip from the guy that already knows who's going to be the next Cisco, Coke or Microsoft.

Most importantly why would Mr. 0 want to talk the likes of us?

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That's a very interesting experience you are describing!! I have one question for you, and that is in regards to the climactic of the earth in 2034, had the polar ice caps melted, as they are now doing at an accelorated rate in this current time.

Sincerely, Draco

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In response to Shadow:

Perhaps it’s a bit easier to understand why time travelers do not revel themselves.

Yes, you can travel forward in time. No, you do not need an “invite” from the future. I first saw the car in 2036. The idea was to find a vehicle that would not draw too much attention for the time period. Unfortunately, there were not very many suitable vehicles around in 2036 and I sold the car when I arrived in 2000.

You do not rewrite history. I can only affect what happens here just as easily as you can. Why do people in this time period worry so much about time traveler’s destroying their world line when they have no problem doing it themselves every day?

My goal is not to be believed. Most people do not take news of the war very well but I find that everyone believes it’s inevitable. Even in your own history, are not great inventions and discoveries made during a time of war in your effort to kill and main in new and more efficient ways?

No, I do not work for GE or any other company. Are “stock tips” really the first thing you want to know about in the future? As a representative of your time period, do you realize what that says about you? You should probably know that this time is not remembered for its selflessness, charity or ability to work together.

Why would I want to talk to you? Why don’t you believe you have something interesting or worthwhile to say to someone in the future?

Mr. “O”

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Hey TimeTravel_0!!!

So then what you're saying is that our current computer models are wrong about Glacial and Polar Ice Cap melting, even though they are going by our current emmisions rate and projected emmisions of the growth of fossil fuels consumption?? While Global Warming is factually happening and even if we stopped burning fossil fuels today and stopped destroying the rain forests today, the impact that is already altered our planetary climate would not stop today as the ball is already rolling. The toxins in the ozone layer and the earths lessening inability to creat oxygen, due to the catastrophic daily destruction of the rain forests that give us most of our oxygen, would take longer than beyond the year 2036 to repair itself, even with our help. I find it amazing that if you throw a WWIII into the equation, one devistating enough to cause the death of 3 Billion people, would not add to the excelloration of Global Warming and raise the sea level to the point where in 2036 most of Florida will be underwater. Help me understand what reversed this impending climatic catastrophy..

Sincerely, Draco

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