Time travel
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replied to:  realeyes
tBoone
Replied to:  "You do realize that there is no such thing as empty...
Of course that something that's inside a place and comes out has to have been inside in order for it to come out. Why state the obvious though? What are you rambling about?
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replied to:  tBoone
doingnothing
Replied to:  Actually, it's quite right. To answer your question "Who said...
Well then, by taking a given you are reducing the problem to its subset. You merely proved you will never time travel back to B. You didn't prove that time travel is impossible.

Who said you are going to violate causality?
http://en.wikipedia.org/wiki/Novikov_self-consistency_principle.

Negative change? It is used in maths all the time.
What would you denote a change that was undone:
change + (-change).

Your definition of time is not the scientific one.
The time is 0s at the big bang and you can measure others relative to it.
The world was completely different 1 sec ago(call that state A), now it is state B. What is meaningless about shifting everything(including electrons,...) back to state A and replacing some amount of air molecules there with yours?
You can call it state shift if you want. If that is possible, I will be excited. But if I invent it, I will call it time travel.
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replied to:  doingnothing
tBoone
Replied to:  Well then, by taking a given you are reducing the problem...
According to the MWI, I did prove that it is not possible to time travel to B, because once you arrive at B you are no longer in U1 and so you have instead universe traveled and NOT time traveled. It may "appear" as if it were time travel but it most certainly is not. This logic is irrefutable. Furthermore, due to quantum uncertainty, once you arrive at B there is NO guarantee that the universe you are in (whether it's U1 or U2) will evolve in exactly the same way as it did up to point C (whence you departed to the past from!) Matter of fact, it is actually HIGHLY unlikely that it will! Which means you might never leave to the past to begin with! This is why I have no love for MWI.

As far as violating causality, the only way that I see you won't violate it is with the MWI which I have shown isn't really time travel at all. Then there's Novikov: there is SO MUCH more assumption, speculation, & conjecture in that proposition than there is in mine. Basically it says that "the universe just won't let a paradox happen." (my paraphrase.) Never mind free will, quantum uncertainty, and other paradoxes that it may lead to. Using Occam's razor, we can see that it's more likely that time travel to the past is not possible vs Novikov's Consistency Principle.

Negative change (as you describe) is still change. A fraction (a ratio or change) is still a fraction regardless of the sign of the numerator or denominator. Of course I can walk forwards and then backwards but it doesn't mean I can time travel to the past. In both instances time is still going forward because change is occurring and entropy is still increasing. You have change occurring in one direction and then another. Think of it like distance: there is no such thing as negative distance.

My definition of time is most certainly a scientific one. I defy you to prove it wrong scientifically. The fact that you can measure time (Big Bang onward) only proves me right: we measure time by measuring change in cesium atoms (for example.) As far as your example is concerned (state A to state B): it's nice but it only shows forward progression of time. I mean, we can theoretically go back to state A on "paper" (i.e. thought experiment) but not in physical reality. It would violate a score of thermodynamic laws (especially entropy.) You would have to return EVERY quark, atom, photon, & "energy" in the entire Universe to that state without using any energy...What do you think is more likely that or simply that time travel to the past is not possible. Precisely.
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replied to:  tBoone
tBoone
Replied to:  According to the MWI, I did prove that it is not...
"The Novikov self-consistency principle proposes that contradictory causal loops cannot form, but that consistent ones can."

Does nothing for this scenario:

"On your 13th birthday, a familiar looking man of middle age gives you a beautifully crafted pocket watch; what appears to be a priceless antique in pristine condition. He tells you that he is a friend of your father's and he'd want you to have it. So you accept the watch, thank the man and he goes on his way.

You never see him again, but you keep the watch in a cigar box and it goes untouched until 35 years later when you finally complete work on your time machine. With the watch, you go back in time to meet your former teenage self and give yourself the watch."

So...where did the watch come from originally? Thin air?
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replied to:  tBoone
doingnothing
Replied to:  According to the MWI, I did prove that it is not...
You didn't see my point. You didn't prove that time travel is impossible.
After searching everywhere to see whether a copy of you exists, and you find it does not.
So, Given:There is only one of you at B.
So, YOU can't time travel 'back to B', because you know YOU haven't time traveled to B. You haven't proven anything else. For someone who has actually time traveled to B, the given is not possible.(see circular reasoning)

I am not talking about alternate universe travel.

There are no assumptions in Novikov's principle. It goes merely: If time travel is possible, the probability of causing a paradox is zero.(the possibility of causing a paradox is always zero;it is not going to change merely because you traveled to the past)
It doesn't affect free will. You can do whatever you want, but you still won't be able to change the past.
You are the one making the assumption that you can actually change what has already happened(which leads to paradoxes).

You can't apply Occam's razor, as time travel is theoretically possible due to bending of space-time.

Same way a negative number is still a number. Can you give me -5 number of apples? The sign is merely a notation. -5 can be taken a removing +5. Similarly, undoing a change delta(x) is denoted -delta(x).
Time can be compared to distance only if you think it can go only forward(which is what you are trying to prove). Otherwise, you should compare it with displacement. Displacement can be negative.
I didn't say you have to shift everything back to state A(in that case changing the past will actually become possible).
I merely provided you a way to visualize time travel without using negative change(which you think is not possible).Err... I just noticed that describing time travel as negative change is not right(changing past becomes possible)

So my argument becomes very short:
1)There is nothing logically wrong with time travel
(Novikov Principle(what assumptions does it make?))
2)It is theoretically possible
http://en.wikipedia.org/wiki/Time_travel#Time_travel_to_the_past_in_physics
3)You don't cause negative change. You loop back into the past. You are never traveling back in time. You travel to a wormhole(while time progresses normally around you), go through it and come back in time instantaneously.(Yes, I made a mistake before)
4) Due to 2), Occam's Razor(which can't prove anything anyway) is not applicable.
5)Traveling to the future is very simple(atleast theoretically) by traveling very near the speed of light and combing back to the place from where you left at the speed of light. If you travel at 0.99995c and come back taking 1 year for the forward and back journey combined, 100 years would have passed at the starting point.So effectively you have traveled 99yrs into the future.
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replied to:  doingnothing
tBoone
Replied to:  You didn't see my point. You didn't prove that time travel...
"For someone who has actually time traveled to B, the given is not possible." Yes. That's because your premise is false; my given (your conclusion) is only true if your premise is true. In other words, for someone who does the impossible then my given is not possible.

You say it is circular logic but, then again, time travel to the past IS circular logic.

"There are no assumptions in Novikov's principle." It assumes that the universe will somehow not let a paradox occur.

"It goes merely: If time travel is possible, the probability of causing a paradox is zero." If there is free will then the probability is NOT zero. Because the probability is NOT zero, time travel to the past is not possible.

"It doesn't affect free will." It completely undermines it. Let me explain: you say that there were always 2 of you at point B; but, in order for that to be true it means that the events from B to C (which have not occurred yet from point B) are set in stone. In other words, you are predestined to come back to B. And you think that this allows for free will? Don’t think so.

"You are the one making the assumption that you can actually change what has already happened (which leads to paradoxes)." True, and that’s why time travel to the past is impossible because the probability of a paradox IS zero. What you don’t realize is that at some possible point far enough into the future, everything is the past. How can you have free will?


"You can't apply Occam's razor, as time travel is theoretically possible due to bending of space-time." Of course I can. Furthermore, time travel HAS been shown to be possible…time travel to the future that is; to the past, never.

"Same way a negative number is still a number." Who has ever said it wasn't a number? Not me.

"Can you give me -5 number of apples?" Of course not. That only proves my point. "The sign is merely a notation. -5 can be taken a removing +5." That’s right. It is a direction and the number a magnitude.

"Similarly, undoing a change delta(x) is denoted -delta(x). Time can be compared to distance only if you think it can go only forward(which is what you are trying to prove)." I’m not trying to prove it: it’s the status quo. There is no empirical evidence anywhere that shows that it can flow any other way.

"Otherwise, you should compare it with displacement. Displacement can be negative." I could but that would be a mistake as it does not behave that way and thus it would be a poor comparison.

"1) There is nothing logically wrong with time travel (Novikov Principle(what assumptions does it make?))" There's plenty wrong; see above.

"2) It is theoretically possible http://en.wikipedia.org/wiki/Time_travel#Time_travel_to_the_past_in_physics" Most of the theories border on fiction. The more accepted ones are the MWI; regardless, they are built on what ifs, on top of more what ifs, and more, and more, etc. Incidentally, I have shown how the MWI theories on time travel are not actually time travel.

"3) You don't cause negative change. You loop back into the past. You are never traveling back in time. You travel to a wormhole (while time progresses normally around you), go through it and come back in time instantaneously.(Yes, I made a mistake before.)" Amazing! You travel to the past, but you don’t, but you do. Make up your mind! Anyways, wormholes do not exist and are purely theoretical; they are possible solutions to EFE.

"4) Occam's Razor(which can't prove anything anyway) is not applicable." It isn't proving anything but it is applicable in the sense that I am using it here.

"5)Traveling to the future is very simple(at least theoretically)…" Theoretically? Are you kidding? It's what's happening around us right now! We are traveling into the future at 1 sec/sec.

"…by traveling very near the speed of light and combing back to the place from where you left at the speed of light." You don’t have to return for the time dilation to occur. This has already been shown experimentally.

"If you travel at 0.99995c and come back taking 1 year for the forward and back journey combined, 100 years would have passed at the starting point. So effectively you have traveled 99yrs into the future." That's great but I never said that time travel to the future wasn't possible; but to the past it is.
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replied to:  tBoone
doingnothing
Replied to:  "For someone who has actually time traveled to B, the given...
Your argument is circular logic. You haven't proven anything.
("my given (your conclusion) is only true if your premise is true. In other words, for someone who does the impossible then my given is not possible. ")
Again circular, you are trying to prove time travel is impossible.

Your argument condensed:
Given:Time travel is not possible
("for someone who does the 'impossible(time travel)' then my given is not possible. ")
Conclusion:Time travel is not possible.
So scrap that argument and try another angle.

The universe will never let a paradox happen.(Do you disagree?). If you think it will, then your whole argument against time travel collapse.
So, no assumption, it is tautology. Time travel by itself is not paradoxical. But, you won't be able to kill your own grandfather before you are born even if you went to past. The logic simply goes that you failed at your attempt(s), and that is why you were born. The 'universe' does nothing. It happened in the past i.e. it is predetermined.

Free will? Is this a philosophical discussion?
You have no more or less free will even if time travel to the past is possible.

Just because the choice is already made, it doesn't mean you didn't make it.(The Oracle from Matrix)

Swami Vivekananda:"Therefore we see at once that there cannot be any such thing as free-will; the very words are a contradiction, because will is what we know, and everything that we know is within our universe, and everything within our universe is moulded by conditions of time, space and causality. ... To acquire freedom we have to get beyond the limitations of this universe; it cannot be found here."
http://en.wikipedia.org/wiki/Free_will. You will find the concept of free will is disputed.

I am not arguing for MWI.
Theories predict time travel is possible. If you think that is 'almost' fiction, that is your POV.
About negative change, there is nothing wrong with it, but I have abandoned that angle as the theories are describe them differently.
"Amazing! You travel to the past, but you don’t, but you do. Make up your mind! "
My mind is made up. What I meant was:
While you are on the machine, time is not moving in the backward direction(i.e. no negative change). You loop back into the past through a path created by a traversable wormhole.
"...You don’t have to return for the time dilation to occur..."
I never said that. But wouldn't you like to see what happens to your country after 99yrs.

Occam Razor:"entities must not be multiplied beyond necessity"
You are using it erroneously.
Wikipedia:Occam's razor is not an embargo against the positing of any kind of entity, or a recommendation of the simplest theory come what may[32] (Note that simplest theory is something like "only I exist" or "nothing exists").The other things in question are the evidential support for the theory[33] Therefore, according to the principle, a simpler but less correct theory should not be preferred over a more complex but more correct one.
If you are using Occam Razor using Hawking's argument:
"A time machine will be built someday, but hasn't been built yet, so the tourists from the future can't reach this far back in time." So, we don't have evidence yet.
But I believe in something simpler, humans will never time travel even though it is possible.There is no emprical evidence for time travel, as the concept is beyond our time(no pun intended)

Wormholes are hypothetical as in predicted by theory. Which is what I was saying. Time travel is theoretically possible, but we have no evidence.

There is no evidence for time travel AND there is no evidence against time travel. But since it is theoretically possible, you can't toss the concept aside.
Since, this is not actually a debate, I will end my discussion here.
You have stated your POV and I have stated mine.
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replied to:  tBoone
doingnothing
Replied to:  "For someone who has actually time traveled to B, the given...
I used the negative number argument to show that negative change is as valid as negative numbers.(as you mentioned the negative sign only shows the 'direction')
But, I am not describing time travel as negative change anymore.
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replied to:  doingnothing
painkiller24
Replied to:  Your argument is circular logic. You haven't proven anything. ("my...
I am just now adding in my two cents to this argument so I apologize if I say something that may have already been said. There is a concept called Time Dilation in which time travels slower in a moving frame of reference (say a spaceship) than a stationary frame of reference (say Earth, Earth is moving but the frame is so large to our perception that it is negligible to factor in its movement.) Having said that, the closer to the speed of light you get, the slower time goes. You will asymptotically (not sure if that's a word ha) get ever closer to the speed of light, but never reach it. However, if you were to go beyond that asymptote onto another curve of speed, the faster you go, time reverses itself. HOWEVER, mathematically in order to be on this second curve you must take the square root of a negative number which is imaginary. A negative number multiplied by another negative number, even itself, creates a positive number. So this just simply does not exist. For example, the square root of 25 is obviously 5. Or, the square root of negative 25 is 5i.
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replied to:  painkiller24
doingnothing
Replied to:  I am just now adding in my two cents to this...
Tachyons(hypothetical and not predicted by theory) are unstable particles that can travel faster than speed of light.
And you don't necessarily get imaginary masses or energy.
http://en.wikipedia.org/wiki/Tachyons#Basic_properties
Also getting an imaginary mass for a particle does not imply it doesn't exist, just questions its physical meaning.

However,
By that theory, faster than light information transmission and causality violation with tachyons are impossible on both grounds: they are non-existent in the first place (by tachyon condensation)[4] and even if they existed they wouldn't be able to transmit information (by Feinberg's analysis).(Wikipedia)
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replied to:  doingnothing
tBoone
Replied to:  I used the negative number argument to show that negative change...
"Negative change" is just change in another direction. Again, that's not time travel and I am still correct. I am glad you agree that time travel is not "negative change."
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replied to:  tBoone
doingnothing
Replied to:  "Negative change" is just change in another direction. Again, that's not...
You claimed time is change and that there can be no negative change. You were wrong on that count.
The only reason I agreed that time travel is not negative change, as the term would imply UNDOING everything. That is simply impossible(entropy,...)
I have described time travel to the past properly in my other reply.
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replied to:  doingnothing
doingnothing
Replied to:  You claimed time is change and that there can be no...
Read the post below
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replied to:  doingnothing
doingnothing
Replied to:  Your argument is circular logic. You haven't proven anything. ("my...
On freewill:
You should also note that scientists favoured determinism and were peeved by the results of quantum theory.(most notably Einstein)
Still, most macroscopic observations are deterministic.
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replied to:  doingnothing
painkiller24
Replied to:  Tachyons(hypothetical and not predicted by theory) are unstable particles that can...
I agree with your statement that getting an imaginary mass does not mean that it doesn't exist. It appears to be that mathematically, there is no literal way to travel through time. As in there is no basic or fundemental law like the laws of physics that say this will happen. However, there's also no law in the universe that says it is not possible. Perhaps we need not to break the rules of the speed of light and mass and energy, nor do we need to bend them, but we need to find a way around them. This is often an argument that introduces worm holes and something traveling through one that "appears" to be exceeding the speed of light. I'm sure we're familiar with worm holes to an extent. The shortest distance between two points is a line. Suppose this were on a piece of paper. However, if you folded that paper and made a bridge to link the two points, this would be a much much shorter distance. Exactly what a worm hole is. The space between the points is condensed and whatever travels through appears to greatly exceed speeds thought possible when in reality, it could be moving no faster than we mathematically may prove possible.
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replied to:  doingnothing
tBoone
Replied to:  Your argument is circular logic. You haven't proven anything. ("my...
I don't think that you understand what I am saying. The concept of time travel (other than MWI) is circular logic itself; why would you expect it to be anything else? Your example grossly misrepresents my argument: it is simple & is shown in previous posts. When you are at point B there is only 1 of you but in order to time travel to the past there must be 2. Pretty simple; I don't see what the problem is. You claim that there are 2 of you at point B but then that means that from B to C that the future is FIXED & immutable. You must then be arguing that all things are predestined & there is no free will. But apart from the (as you say) philosophical question, you are implying some kind of new PHYSICAL phenomenon: a type of reverse causation. This is completely illogical.

"The universe will never let a paradox happen (Do you disagree?). Of course, I agree!" That's why time travel to the past cannot occur: it is a paradox! But you say that what I'm calling time travel to the past isn't really correct. Instead, it's possible to time travel to the past it's just that when you get there you cannot do anything that hasn't already happened even though it hasn't happened yet. So your will doesn't matter, quantum uncertainty, etc; everything get's played out according to some master plan. The future is fixed & immutable. Sorry, I don't buy it.

"Time travel by itself is not paradoxical." Sure, so long as you don't explain it. Once you explain it, you see that it leads to contradictions. Then you say: "But, you won't be able to kill your own grandfather before you are born even if you went to past. The logic simply goes that you failed at your attempt(s), & that is why you were born." I mean, really. Are we supposed to believe that in this scenario one would, much like Wiley Coyote, comically go about trying to kill grandpa but "somehow" fail all the time. What if we tried to kill ourselves? Same thing I suppose, right? So, we are to disregard an almost infinite number of probable & POSSIBLE scenarios that do NOT violate any known laws of the Universe (other than this new "time paradox" law) & then the Universe somehow prevents them from happening (a more complex & questionably correct theory)...or that (Occam's Razor) time travel to the past isn't possible (a simpler and correct theory)...I think I'll choose the latter instead of Wiley Coyote, thank you.

"The 'universe' does nothing. It happened in the past i.e. it is predetermined." When you are at point B, point C is NOT the past. "Free will? Is this a philosophical discussion?" Of sorts; it is a theoretical physics discussion. "You have no more or less free will even if time travel to the past is possible. Just because the choice is already made, it doesn't mean you didn't make it.(The Oracle from Matrix)" The Matrix is a movie; it's not real. Not to say I didn't like it; I did. But it is fictional, nonetheless. Did you notice the paradoxes in your previous sentences? You speak of the future as if it were the past. That's a paradox & circular reasoning.

"Swami Vivekananda:'Therefore we see at once that there cannot be any such thing as free-will; the very words are a contradiction, because will is what we know, & everything that we know is within our universe, & everything within our universe is moulded by conditions of time, space & causality...To acquire freedom we have to get beyond the limitations of this universe; it cannot be found here.' http://en.wikipedia.org/wiki/Free_will. You will find the concept of free will is disputed." This is a metaphysical argument & does nothing for all the other scientific arguments that I posited. But, for arguments sake: that's neither the definition of the Universe nor free will that I am using or that I believe is even correct. If you begin with a concept of free will that is a contradiction, then what do you expect? It is silly to operate from that perspective. Anyways, the Universe is "all that is," to suggest that there are limitations to the Universe is ludicrous: what else is there other than all that is?

"I am not arguing for MWI." I know that. You said several times already & I never said that you have stated otherwise. I am merely pointing out to you that the MOST plausible form of time travel to the past is through the MWI. This is currently the MOST accepted view.

"Theories predict time travel is possible. If you think that is 'almost' fiction, that is your POV." Yes; mine & most of the scientific community. There are so many physics text books about time travel to the past.

"About negative change, there is nothing wrong with it, but I have abandoned that angle as the theories are describe them differently." Again, negative change is simply change in another direction. This must be abandoned because the way that you have described it has nothing to do with time travel.

"While you are on the machine, time is not moving in the backward direction (i.e. no negative change). You loop back into the past..." What does "loop back to the past mean" other than magic or negative change? "...through a path created by a traversable wormhole." Wormholes do not exist, never mind traversable ones. They are PURELY theoretical. You are grasping at straws. Did you see all of the highly unlikely conditions attached to time travel to the past via a Wormhole? It is speculation, on top of speculation, on top of more...practically ad infinitum.

"You are using Occam's razor erroneously." I am not. There is NO EXPERIMENTAL evidence of time travel to the past. My theory is a simple & more correct so it is preferred. Heck, I'll even concede that it is not more correct: I'll say equally. It still holds.

"Hawking's argument: 'A time machine will be built someday, but hasn't been built yet, so the tourists from the future can't reach this far back in time.'" Hawking's argument is not experimental (empirical) evidence; it is a thought experiment: speculation. But I love the logic of this one too: in other words, you'll be able to travel from anytime in the future back only up until the first time machine was made. & that's because of Hawking's law of cause I said so? Nope. It is speculation.

"So, we don't have evidence yet. But I believe in something simpler, humans will never time travel even though it is possible. There is no empirical evidence for time travel, as the concept is beyond our time (no pun intended)" Good, but I agree for different reasons :0)

"Wormholes are hypothetical as in predicted by theory. Which is what I was saying. Time travel is theoretically possible, but we have no evidence. There is no evidence for time travel & there is no evidence against time travel." As I said before, one thing is prediction by theory & another is a concept derived from theory upon theory upon theory. You don't see the distinction? Also, the evidence against time travel is scientific theory (relativity: the speed of light is invariant) backed by observations & empirical results. Anyways, it makes no sense to try and prove a negative.

"But since it is theoretically possible, you can't toss the concept aside." Yes but the most commonly accepted theory is the MWI form of time travel to the past.

"Since, this is not actually a debate, I will end my discussion here. You have stated your POV & I have stated mine." Very well.
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replied to:  doingnothing
tBoone
Replied to:  On freewill: You should also note that scientists favoured determinism and...
True. As am I...but it is there nonetheless and cannot be ignored. It is even more empirical evidence to show that the future is not fixed; hence to time travel to the past. ;o)
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replied to:  painkiller24
tBoone
Replied to:  I am just now adding in my two cents to this...
Yes. Time Dilation is in the forward direction. In other words, time can go slowly, quickly, or stop, but NOT backwards. Once you reach c, time will stop as you will have consumed all possible time available in the Universe!

One cannot go beyond the c as that is impossible. However, even if one were to, one would only APPEAR to go back in time and not actually do so.

As you know, i is an imaginary number; it is a concept of the imagination.
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replied to:  painkiller24
tBoone
Replied to:  I agree with your statement that getting an imaginary mass does...
Wormholes are completely hypothetical; but, in your example, you are simply covering a large distance in what seems to be faster than c. In actuality you are not exceeding c because you are really just traveling a shorter distance. All this will achieve is the illusion of time travel. To use your example, you leave earth & go to the hypothetical Wormhole 5 minutes away. It's Nov 2009 and you enter the worm hole which leads you to a place 100 light years away from earth. Now you look back at earth with your nifty telescope & what do you see? The earth as it was 100 years ago! Are you in the past? No. just observing the light that left earth 100 years ago.
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replied to:  doingnothing
tBoone
[POST DELETED]
It is simple...it's simply circular logic. The Grandfather Paradox (GFP) is a perfect example. Your reply to the GFP: the universe just won't let you kill your grandfather. Based on what the much forgotten "can't kill grandpa" Law of Thermodynamics? Or maybe it's based on circular logic of: "I am able to come to the past because I won't be able to kill grandpa in the future."

I think that clearly proves it.
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replied to:  tBoone
painkiller24
Replied to:  Wormholes are completely hypothetical; but, in your example, you are simply...
Yes, worm holes are just shortening the distance and making something seem to be faster than the speed of light. Thats exactly what I said before...
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replied to:  tBoone
doingnothing
Replied to:  I don't think that you understand what I am saying. The...
A concept cannot be circular. Only arguments can be circular. Your argument is definitely circular.

"Your example"
That wasn't an example
Your Given:There is only one of you at B
Me:But that would only mean you didn't travel back to B
You:("for someone who does the impossible(time travel) then my given is not possible. ")
So Your Given is EQUIVALENT to Time travel is impossible.

You are overestimating your capability to change anything.
Suppose if you went back before titanic even left the shore, and warned them about the disaster, you would have been thought as a fool and no one would've listened. With guards around, you wouldn't be able to resort to any other means either.
(Cassandra Complex)
Your grandfather isn't going to be alone. Even a professional will have trouble to assasinate anyone. In a time where he doesn't belong, he will have further trouble blending in.
In a one person system, you will be able to change anything. But with millions of people, you won't be able to affect it.
Time travel is no different than space travel. You put an apple in a some secret place, when you go back to that place the apple is going to be there. Similarly, something happened in

You fail to understand Novikov Principle

The only solutions to the laws of physics that can occur locally in the real Universe are those which are globally self-consistent.
Novikov Principle follows directly from the above statement. If time travel is possible, the solutions of 'your actions' cannot be inconsistent.

(about oracle)Just because the statement came in a movie it doesn't make it invalid. The statement wasn't specific to the movie. In fact I wrote the statement first, and then wondered where I got it from.

"Just because a choice is already made, it doesn't mean you didn't make it"
If you are going to ask a girl who loves you to marry you, you know she is going to say yes. But, you didn't make her choice-she did. So, going to the past you know who your father is going to marry. But, neither you nor anyone else other than your father(and mother) made that choice. You merely observed a chain of causaly related events which would nevertheless happen even if you did go the past.
The past was a result of you(if you go the past) and everyone else there. Obviously, the result cannot be such that you won't go to the past.

Also, you fail to realise that if time travel was ever shown to be logically flawed(by scientists or anyone else), no one would be discussing this in the first place(especially not scientists).
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replied to:  tBoone
doingnothing
Replied to:  True. As am I...but it is there nonetheless and cannot be...
Quantum uncertainty is almost entirely limited to microscopic behaviour.

The only entity on the other side is the unfortunate Schordinger's cat.

Since such an apparatus has never been created, nor does any natural phenomena is analogous to the experiment, quantum uncertainty doesn't come into picture describing any human or animal behaviour.
The world is deterministic.
Even the other side of the argument doesn't claim that the world is not deterministic, but rather that not everything is deterministic.

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replied to:  tBoone
doingnothing
Replied to:  It is simple...it's simply circular logic. The Grandfather Paradox (GFP) is...
I will state the argument properly:

0)Assume time travel is possible
1)You know your grandfather was not killed before your father were born.
2)You go to the past, and try to kill him.
3)But he wasn't killed before your father was born.
4)EITHER 0) is false OR you won't be able to kill him.

So, the grandfather paradox doesn't prove that time travel is impossible.

It follows,
5) IF time travel is possible:
5.1)You won't be able to kill your grandfather.

The numbering will help you find any logical flaws. (There isn't any)
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replied to:  doingnothing
doingnothing
Replied to:  I will state the argument properly: 0)Assume time travel is...
I will further clarify that Novikov principle is not a proof for time travel. But, rather aims to merely prove that time travel(if possible) will not lead to logical paradox and that time travel is not a paradox.

This is my last reply. Honest.
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replied to:  doingnothing
doingnothing
Replied to:  Quantum uncertainty is almost entirely limited to microscopic behaviour....
Also, MWI is NOT the favoured explanation for time travel.
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replied to:  tBoone
doingnothing
Replied to:  Wormholes are completely hypothetical; but, in your example, you are simply...
No. You are in the past. That is why you are able to observe the light from 100 years ago. A person looking at you from the earth would see you even though you were not born yet. And you can travel back to the earth.(Be sure to choose a nearby wormhole)
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replied to:  doingnothing
doingnothing
Replied to:  I will further clarify that Novikov principle is not a proof...
You didn't understand my position at all.
I did not claim that there is some traversable wormhole somewhere and we can travel to the past.
I understand that they are wormholes are purely hypothetical and a traversable one needs to satisfy additional number of conditions.

I state that time travel is not impossible but only unlikely.
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replied to:  tBoone
doingnothing
Replied to:  Yes. Time Dilation is in the forward direction. In other words,...
'Consumed all possible time'? You know that sounds weird.

It is mathematically possible to go beyond speed c.
An object of zero mass(photons) or imaginary mass can travel faster than c. So, you can transmit information(via photons) to the past.

One of the basic postulates of general relativity is that there is no preferred frame.
So, the fact that you appear to go back in time from a particular frame implies that you did, infact, go back in time.
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replied to:  doingnothing
doingnothing
Replied to:  Quantum uncertainty is almost entirely limited to microscopic behaviour....
Even for the cat, if you already know(from signals sent from the future) that it is going to die, it will die.
(Information from the future is beyond determinism, you have actually determined what is going to happen)

Think quantum entanglement.
Once you determine the state of one object, the state of the other(which may be killometres away) is automatically determined.
(Information traveling at speed above c which is essentially information from future)
Unfortunately, quantum entanglement cannot be used for transmitting real information.
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replied to:  doingnothing
doingnothing
Replied to:  No. You are in the past. That is why you are...
Hmmm...Didn't read your post properly. Wormholes can also be used to travel to the past. But the wormhole should have already been existence in the past.
What you described is not time travel.
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replied to:  doingnothing
tBoone
Replied to:  I will state the argument properly: 0)Assume time travel is...
0)Assume time travel is possible.
1)You know your grandfather was not killed before your father were born.
2)You go to the past, and try to kill him.
3)But he wasn't killed before your father was born. 4)EITHER 0 is false OR you won't be able to kill him.\*

Let's set aside a flaw in the logic above, which I'll explain later; the key is in #4. One is a possibility (i.e. time travel is impossible) the other is an absurdity. Again, what law of physics prevents you from killing grandpa? The Universe somehow "knows" that you went to the past and "knows" that you can't change anything & will stop you if you try? Don't you see how ludicrous that is?

Now, the flaw in logic: (2)you go to the past & decide to kill grandpa. You are currently in the past: the future has NOT happened yet; you have never experienced going to the past before. Then there is reverse causality (3)But he isn't going to be killed before your father will be born." This is an error in logic: an effect cannot precede its cause.

In order for this logical proof to function you must dismiss logic at some point or another. Anyways, logic alone can tell us nothing new about the real world. The same goes for mathematics, as Albert Einstein observed: "Insofar as mathematics is exact, it does not apply to reality; and insofar as mathematics applies to reality, it is not exact."
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replied to:  doingnothing
tBoone
Replied to:  You didn't understand my position at all. I did not claim...
I understand you perfectly your position; heck, I even believed in it at one point or another in my life. However, even using that definition of time, time travel to the past via Wormhole in VERY VERY HIGHLY unlikely.

As I am sure that you are aware of, most of this depends on the definition of time. Using some of the acceptable definitions out there, there may be a possibility for time travel to the past; however, there are perfectly acceptable definitions of time (like the one that I am using here) that would make such a thing impossible.

The reason is that when using said definition, time travel to the past is itself a paradox; it is a paradox by definition. Consequently, the Novikov principle would fail because it would be assuming a false premise. As you may have guessed, I prefer my definition of time: it is quite elegant in its simplicity and neatly solves all these issues of time time travel.
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replied to:  doingnothing
tBoone
Replied to:  A concept cannot be circular. Only arguments can be circular. Your...
"A concept cannot be circular. Only arguments can be circular." You're kidding, right? You're going to play semantics? You're grasping at straws. Try again.

"Your argument is definitely circular..." What followed after that was completely unintelligible. Anyways, I already explained to you that given my definition of time, time travel to the past is a paradox in and of itself. End of story. If time travel to the past is a contradiction to begin with, then none of what you have mentioned will change that. I have already agreed that if you were to use another definition of time, then your contentions hold. I can't see what's so hard to understand about that?

"You are overestimating your capability to change anything." Not at all: this is extremely simple, why are you complicating it? You keep insisting that somehow change in reverse is undoing what has been done. This is incorrect. Just because you walk forward and then walk backwards doesn't mean that you have time traveled to the past: they are BOTH change, just in different directions. Perhaps if I state it differently: Change in ANY direction is the forward progression of time. Did that help? I still don't understand why you're hung up on direction, but anyways.

"Suppose if you went back before titanic even left the shore...Even a professional will have trouble to assassinate anyone." Are you joking? How many more excuses can you come up with? I mean, really.

"In a one person system, you will be able to change anything. But with millions of people, you won't be able to affect it." You think that it's just "one person" that's a big deal? Have you ever heard of Chaos Theory? Just 1 atom, 1 quark, 1 Plank energy state of a difference in the ENTIRE Universe can have an ENORMOUS effect in the system as time progresses. Never mind an entire person! This coupled with quantum uncertainty is a formula for the practical guarantee that things will NEVER happen in exactly the same way. This is yet another reason why the MWI is the preferred time travel mechanism; again, not that I agree with it.

"Time travel is no different than space travel." Sure, if you are traveling forwards in time, otherwise it is a bit different. It is called space-time after all.

"You fail to understand Novikov Principle." Do you think that something will become true if you keep repeating it? I understand it perfectly; it's you who doesn't comprehend that NP depends on the definition of time & consequently time travel.

"If time travel is possible, the solutions of 'your actions' cannot be inconsistent." Yes. But you did notice the first word in that sentence, right? IF. Now, suppose a definition of time/travel is such that it is a paradox to travel to the past, then NP is useless.

"Also, you fail to realize that if time travel was ever shown to be logically flawed (by scientists or anyone else), no one would be discussing this in the first place (especially not scientists)." It has been shown to be flawed many times. Look at your own sources, man. As I said before, there are many definitions of time, time travel, etc. Depending upon the one that you choose, this will change whether or not time travel is possible and how it might be implemented.
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replied to:  doingnothing
tBoone
Replied to:  You claimed time is change and that there can be no...
"You claimed time is change and that there can be no negative change. You were wrong on that count." No. I was right.

"The only reason I agreed that time travel is not negative change, as the term would imply UNDOING everything. That is simply impossible(entropy,...)" Exactly. And that's why time travel to the past is impossible. See how easy that was?
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replied to:  doingnothing
tBoone
Replied to:  Quantum uncertainty is almost entirely limited to microscopic behaviour....
"Quantum uncertainty is almost entirely limited to microscopic behavior." Key words: almost entirely. There have been many experiments that show quantum uncertainty at the macroscopic level! This is exciting stuff.

See>> http://www.sciencedaily.com/releases/2009/11/091104140812.htm

Also, there are those that believe that quantum mechanics is applies to the macroscopic level as well, and interpret it as such.

Anyways, this is all fun stuff but the micro/macro has absolutely NOTHING to do with this discussion. I am going to guess at what you are trying to get at: you may be thinking that a person (macroscopic) going back in time will not experience any quantum uncertainty effects. However, a person is made up of atoms, atoms of leptons & nucleons, and those quarks, etc. There might be 7x10^27 atoms in a human body: now let's throw in chaos theory and mix it with a little quantum uncertainty and you are pretty much GUARANTEED NOT to have the same outcomes.
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replied to:  doingnothing
tBoone
Replied to:  Also, MWI is NOT the favoured explanation for time travel.
Yes it is. It is in physics and it is in Hollywood as well.
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replied to:  doingnothing
tBoone
Replied to:  Even for the cat, if you already know(from signals sent from...
Information cannot exceed c. Entanglement can and is used to transmit information: it just cannot be used to transmit information faster than c.

Example: You and I are 2 light years apart & we share a pair of entangled photons. You check your photon and now know it's state as well as mine BUT I don't know the state or that you even measured it. You still need a classical channel (sub-luminal or luminal) to alert me of your findings.

This is still very useful because it can be used to have totally secure communications between us. If anyone where to eavesdrop 2 things would happen: (1) they would be unable to decipher the signal and (2) the signal would be changed and thus we would be alerted to this.
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replied to:  doingnothing
tBoone
Replied to:  'Consumed all possible time'? You know that sounds weird. It...
"You know that sounds weird." I know. Did you know that c can be thought of as the speed of time? You see, a photon travels at c and from its perspective, it has consumed all of the time available to it in the universe. To a photon (or anything traveling @ c) there is no more time left.

"It is mathematically possible to go beyond speed c. An object of zero mass(photons) or imaginary mass can travel faster than c." Yup. But as my good friend once said, "Insofar as mathematics is exact, it does not apply to reality; and insofar as mathematics applies to reality, it is not exact."

"So, you can transmit information (via photons) to the past." Absolutely not. Even according to SR, you would need a super-luminal channel and we know that's not possible.

"So, the fact that you appear to go back in time from a particular frame implies that you did, in fact, go back in time." No it doesn't; that's ludicrous! By that rationale, every time we look at the sky or through a telescope we are really traveling through time. Rubbish.

When we look through a telescope at an object 100 light years away we are seeing what that object looked like 100 years ago: it "appears" as if we have gone back in time but we really have not.
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replied to:  doingnothing
tBoone
Replied to:  No. You are in the past. That is why you are...
"No. You are in the past." No. You are not.

"That is why you are able to observe the light from 100 years ago." No. We observe light from 100 years ago all the time whenever we look at objects in the sky that are 100 light years away. Are you implying that looking up at the sky is time travel? Didn't think so.

"A person looking at you from the earth would see you even though you were not born yet." Uh, no. No one from earth would see you for another 100 years as it would take the light (i.e. the light of you being there) 100 years to get to earth.
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replied to:  tBoone
doingnothing
Replied to:  I understand you perfectly your position; heck, I even believed in...
The nuances of the definition cannot prove or disprove anything. If your definition is time, we will take our definition as timee and say time travel is not possible but timee travel is possible.
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replied to:  tBoone
doingnothing
Replied to:  0)Assume time travel is possible. 1)You know your grandfather was not...
The grandfather paradox is used as thought experiment against time travel. I merely pointed out the grandfather paradox is impossible even if time travel is possible.

I didn't say that the paradox proved time travel is possible.(that would be stupid)

The other is not an absurdity.
You are overestimating your ability to change anything
Also see Cassandra complex.
See my previous replies commenting why the statement is not absurd.

Your whole arguments clings on your ability to affect the past. Accounting the fact there are millions of other persons, millions of external factors which would affect your action of trying to affect an action, it isn't absurd to claim you will fail.
Further, the fact that you know you will fail will discourage you to go the past in the first place.

Suppose you go the past, let the change you caused be x

Past + x = Present

The present you observed was the result of your actions + the actions of everyone else in the past.

The equation as you see is very simple. The equation also makes it absurd to go to the past to change anything.

Infact this is the basis for Hawking's argument against time travel.(the argument was only against humans time traveling)

Mathematics is used to MODEL reality. The challenge for physicists is to make the model as accurate as necessary. The equations of physics is not maths. It models reality, and as such is applicable. Since, wormholes are possible by the relativity theory-which has been proven right time and again-it is reality.
Ofcourse,the fact that wormholes can exist doesn't mean it exists.

About causality
The chain of events
Your grandfather->(you try to kill him)->gives birth to your father->your father irritates you->you want to kill him->you go back to the past to try to kill him

So, you claim the effect happens(you trying to kill him) before the cause(your father irritates you)
But rather, you are not part of that time. For you everything has already happened. You have already experienced it. The chain of events and effects leading to your father being an irritating person will still occur and the younger-you will go back to the past. Also, this isn't a cycle. You will go into the future older than you should have been.

You can argue semantics till the world ends.

Also, note that causality is not a necessary condition.
It has merely been observed that all events follow causality and in the face of new science, it would need to be abandoned.

Logic can prove something to be impossible, if it is self-contradicting.
"logic alone can tell us nothing new about the real world."
Thank you for finally accepting that time travel is not logically impossible. Goodbye.
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replied to:  tBoone
doingnothing
Replied to:  "No. You are in the past." No. You are not....
Read below post and see its date. I didn't read your previous post properly. I corrected my statement promptly.
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replied to:  tBoone
doingnothing
Replied to:  "You know that sounds weird." I know. Did you know that...
See http://arxiv.org/abs/gr-qc/0107091 for a PHYSICS paper on faster than c signals.

The time slows as we approach c, stops at c, and goes backwards at c.
There is no reason,other than mathematical one of the requirement for zero mass, for faster than c speed to be impossible.
Using your approach to 'argument':What does the universe do to prevent you from exceeding speed c?
Before 'your friend's' theory, would you have said that traveling faster than the speed of light is impossible?
But even his theory only says that objects of non-zero and real mass cannot travel faster than the speed of light.

"Did you know that c can be thought of as the speed of time?"

Exactly, so you 'merely' need to transmit signals faster than c to send it to the past

"that's ludicrous!"

No. It is the main postulate of general relativity. No frame is preferred.
You: "You appear to go back in time from a frame". Since, no frame is given preference you did travel back in time.

Your telescope argument is wrong. You don't apply relativity like that. Study the basics atleast.
From the reference frame of the earth, the star IS as old as it appears.
No reference frame is preferred for measuring the stars' age(including its own).

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replied to:  tBoone
doingnothing
Replied to:  I understand you perfectly your position; heck, I even believed in...
Novikov principle is not on the premise of time travel.
It holds if time travel is possible, the Novikov priciple is followed.

In other words:
Time travel is not paradoxical. It would follow Novikov principle.

Novikov principle DOESN'T ASSUME ANYTHING.

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replied to:  tBoone
doingnothing
Replied to:  I understand you perfectly your position; heck, I even believed in...
Your belief that you have 'disproved' time travel when no scientist has, is audacious to say the least.
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replied to:  doingnothing
doingnothing
Replied to:  The nuances of the definition cannot prove or disprove anything. If...
I know that sounded childish, but it is still true.

Definition is for grammar freaks.
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replied to:  doingnothing
tBoone
Replied to:  The grandfather paradox is used as thought experiment against time travel....
"The grandfather paradox is used as thought experiment against time travel. I merely pointed out the grandfather paradox is impossible even if time travel is possible." Again, the Novikov Principle is a tautology. Paradoxes can never happen as they are contradictions and are not physically real. Consequently, whether time travel to the past (or anything for that matter) is possible or not will have zero effect on the fact that paradoxes do not exist physically. The NP does nothing for the Grand Father paradox.

"I didn't say that the paradox proved time travel is possible.(that would be stupid)" And also makes no sense.

"The other is not an absurdity." have you ever watched the Roadrunner cartoon? Wile E. Coyote tries to kill the Roadrunner in so many different ways but always fails as he is destined to do. This is how someone trying to kill their grandpa in the past, would fail. And you don't think that that's absurd?

"You are overestimating your ability to change anything...Also see Cassandra complex." What does this have to do with anything? I think I might know what the problem is. You might think that I'm referring to some personal form of change like a person's actions or something like that. While this is also change it is by no means the only change that I am referring to.

My definition is: "change" is the forward progression of time. I am talking about its most simplest form: motion, temperature, etc. Here are some more examples: an atom moving or shaking; an electron "orbit"; molecules moving about; water falling down the side of a mountain; me typing this. This is all change. So you see, you can have more or less or none but you can't have anti-change or negative change. Do you understand now?

"Your whole arguments clings on your ability to affect the past..." No. My argument clings on my ability to affect the present. Once you time travel to the past, the past becomes the present to you. So time travel to the past is like making past = present...wait a second...isn't that whatcha call a paradox? Oh yeah!

As far as trying to kill grandpa is concerned, I guess walking up to him and putting a couple of bullets in his head wouldn't work, right? I guess it'll be like Wile E. Coyote and the Roadrunner. Yup. That's an accurate depiction of reality and it isn't absurd at all. Or maybe not.

"Suppose you go the past, let the change you caused be x..." I guess you mean that a made change x in order to go to the past. OK, I'll bite.

"...Past + x = Present..." Not sure if I'd agree on the equation. How about Present - x = Past? Anyways, even if I agree with your equation you still executed change which is of course the forward progression of time and all you did was go forward in time again. Think of time as an operand (+ - / x exponentiation, any action); no matter which operand you choose it's still the forward progression of time.

"The present you observed was the result of your actions + the actions of everyone else in the past." It should read the present you observe not observed as that would make it past tense and thus not the present but the past. Anyways, there are an almost unlimited number things other than people that affect the way time progresses.

"The equation as you see is very simple. The equation also makes it absurd to go to the past to change anything. Infact this is the basis for Hawking's argument against time travel.(the argument was only against humans time traveling)" Actually, I think it makes it absurd to go to the past.


"Mathematics is used to MODEL reality. The challenge for physicists is to make the model as accurate as necessary. The equations of physics is not maths." You couldn't be more hopelessly wrong: physics IS math. I Think what you might be trying to express is that all physics is math but not all math is physics. That I would agree with.

"It models reality, and as such is applicable. Since, wormholes are possible by the relativity theory-which has been proven right time and again-it is reality." You couldn't be more hopelessly wrong, again. SR might be a very good approximation of some aspects of reality, but it is not perfect. Furthermore, Wormholes are solutions to the math of SR but that doesn't mean that it has an equivalent in real life. Not all solutions to math reveal a real life equivalent.

"Of course,the fact that wormholes can exist doesn't mean it exists. About causality The chain of events Your grandfather->(you try to kill him)->gives birth to your father->your father irritates you->you want to kill him->you go back to the past to try to kill him So, you claim the effect happens(you trying to kill him) before the cause(your father irritates you) But rather, you are not part of that time." Agreed. You aren't part of that time because you are in the present and time travel to the past is impossible. If it were possible, then you would be part of that time by being simply there.

"For you everything has already happened. You have already experienced it." Lol! If you go to the past in your time machine (having never done so before) how can you say anything already happened if you've never time traveled to the past before? That's ridiculous and circular reasoning.

"The chain of events and effects leading to your father being an irritating person will still occur and the younger-you will go back to the past. Also, this isn't a cycle." Oh no. Not a cycle at all...Actually, I don't think it can get more circular than that!

"You will go into the future older than you should have been. You can argue semantics till the world ends. Also, note that causality is not a necessary condition. It has merely been observed that all events follow causality and in the face of new science, it would need to be abandoned." Cause & effect is the root of logic as well as science: abandon that and what do you have left? Nonsense.

"Logic can prove something to be impossible, if it is self-contradicting. "logic alone can tell us nothing new about the real world." I said that logic can't prove a negative unless the Universe of discourse is extremely small. The Universe is practically infinite so proving a negative there is not possible.

"Thank you for finally accepting that time travel is not logically impossible." It is if you use my definition of time.
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replied to:  doingnothing
tBoone
Replied to:  I know that sounded childish, but it is still true....
Right. Physics doesn't use definitions. Why didn't I realize that? Physics is just a bunch of good sci fi movie plots put together. Or maybe not. Definitions matter, especially in physics. I hope you realize that.
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replied to:  crazyman2
scholar12
Replied to:  Is time travel possible?
I have no scientific proof to say not, although many scientists have tried and failed America never thought it would be possible to fly, then the Wright brothers came along and invented the plane in 1905 that could fly half an hour or more at a time. "The law is reason free from passion-" Aristotle... this applies to science too for the scientific law.
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