<b>New Model 'Permits Time Travel'</b><br /><br />LINK<br /><br />If you went back in time and met your teenage parents, you could not split them up and prevent your birth - even if you wanted to, a new quantum model has stated. <br /><br />Researchers speculate that time travel can occur within a kind of feedback loop where backwards movement is possible, but only in a way that is "complementary" to the present. <br /><br />In other words, you can pop back in time and have a look around, but you cannot do anything that will alter the present you left behind. <br /><br />The new model, which uses the laws of quantum mechanics, gets rid of the famous paradox surrounding time travel. <br /><br />Paradox explained <br /><br />Although the laws of physics seem to permit temporal gymnastics, the concept is laden with uncomfortable contradictions. <br /><br />The main headache stems from the idea that if you went back in time you could, theoretically, do something to change the present; and that possibility messes up the whole theory of time travel. <br /><br />Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious. <br /><br />So either time travel is not possible, or something is actually acting to prevent any backward movement from changing the present. <br /><br />For most of us, the former option might seem most likely, but Einstein's general theory of relativity leads some physicists to suspect the latter. <br /><br />According to Einstein, space-time can curve back on itself, theoretically allowing travellers to double back and meet younger versions of themselves. <br /><br />And now a team of physicists from the US and Austria says this situation can only be the case if there are physical constraints acting to protect the present from changes in the past. <br /><br />Weird laws <</safety_wrapper>
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"If we don't know your father is alive right now - if there is only a 90% chance that he is alive right now, then there is a chance that you can go back and kill him. <br /><br />Are they saying that so long as 'sombody' knows he is alive in the present, i.e. he has been observed in the present, then he can't be dead in the past. <br /><br /><br />"But if you know he is alive, there is no chance you can kill him."<br />Here then they say 'you', just wondering if the theory allows for you travelling back with uncertainty regarding the fathers current state even though his state has been observed by someone else but not conveyed to you.<br /><br />Does this make a difference or am I over complicating it.<br />Cool article though. Thanks
I read a fictional book long ago, and perhaps someone else remembers it.<br /><br />A man discovered a creature made of neg matter (not antimatter, a white hole would be an example of a stellar neg matter object)<br /><br />he discovered a way, using neg matter, to send and recieve trasmissions. he was able to watch a person he was talking to leave in one screen, then finish talking to him and watch him leave on the other screen.<br /><br />he discovered that he could change things, but only if he didnt know the outcome, even though others did.<br /><br />For example, he had someone send him a message stating an attack happened to his family on a certain day, but not told the outcome. he was able to get a message back using standard comms, and though the attack happened, no one was hurt.<br /><br />That is an interesting thought. Your universe is created when you observe it. if you dont observe something, even though your brother did, you could techically still change it. as long as yoru brother didnt tell you.<br /><br />hmm... no one exists unless observed? quick, dont tell me about Siberia!
creepy. I thought about the same thing a while ago, but then figured out it was too far fetched-I mean how can the Universe 'know' how to stop you? anyways, I'd like to read a more technical explanation, that article is for laymen. If anybody knows a better link, post it here. I'm gonna try livesciece.com . <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
<font color="yellow">"If we don't know your father is alive right now - if there is only a 90% chance that he is alive right now, then there is a chance that you can go back and kill him. " </font><br /><br />Here's another loose end. I am 100% certain that my father is dead but I am 100% certain he lived because I exist.<br /><br />The article makes it sound like I can go back in time and kill him because he is not alive TODAY. But if I kill him before I was born then I would not exist. So I guess you could say that even if I am not 100% certain that my father is alive, I am 100% that I am alive so I cannot go back and kill my father because then I would not be born. However, while I am in the past then nobody in the present can be certain that I am alive. <br /><br />In terms of the articles point of view, I think the only possibility is that you cannot go back and alter the past, EVER. Once something exists in the present, (or existed in the past), then there is a 100% chance that it exists, (or existed), so there is no chance of going back and preventing that specific thing from existing.
To me, the biggest argument against time travel is that we don't observe any time travelers.<br /><br />For example, I am positive that I will never time travel in my lifetime. Otherwise, I would have come back already and told my brother not to begin dating his ex-wife!<br /><br />But what if interaction is not possible between the time traveler and the past? Maybe the traveler exists as a shadow, as a ghost?<br /><br />It's an interesting hypothesis, could make a good novel. Ghosts are time travelers that exist just outside of our perception. Some people can pick up on them unconsciously.<br />
what if somebody ahs a heart attack because he's seen a ghost. that means time traveller has affected the past! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
<blockquote><font class="small">In reply to:</font><hr /><p>To me, the biggest argument against time travel is that we don't observe any time travellers<p><hr /></p></p></blockquote> <br /><br />Perhaps that is because you need a transmitter and a receiver, so as soon as someone builds a receiver time travellers will start walking out of it <img src="/images/icons/smile.gif" />
if we would see a timetraveller i would tell everyone i saw one, ppl say i'm nuts and will kill me for it in a future law system, so i wont have any childeren<br /><br /><br />its a stupid story, but you know what i mean?
After thinking about it I have concluded that it's not possible to time travel.<br /><br /> I base that conclusion on these 2 assumptions.<br />(1) To get to the past (or future) from the present you have to be able to start at the present so you must have the ability to pin down the "present" in a very precise manner.<br />(2) However, time is continuous so it is not possible to identify the precise instant that is now, or the "present".<br /><br />Suppose you have a "quantum camera" with a shutter speed equal to the speed of light and you want to take a picture of "now", (obviously it would not be "now" by the time you look at the picture but bear with me.)<br /><br />However, the picture of "now" would not measure a precise instant. Rather it would measure the passage of time from the time the shutter opened to the time the shutter closed. So the picture of "now" would measure an interval that could be divided into smaller units of now. Each of those units could be divided and so on.<br /><br />QT'ers might claim that the picture represents the smallest discrete unit of time so that the picture would represent a discrete piece of reality that could be called "now". However there are probably as many logical arguements for time being continuous as there are for time being discrete.<br /><br />The way I see it, time is a measure of change. Change requires the passage of time. If time is continuous then you can never pinpoint "now". If you can't identify now, the present, with certainty, then you cannot travel from the "present" to the past.
Something else to think about it time dialation.<br /><br />THe faster you go, the slower time moves for you. You can travel for 1 year your time, and 4 years passed on earth.<br /><br />Future time travel is therefore possible by simply having the person accelerated to a good portion of the speed of light, and spend a year or so before returning to earth. you technically went foward into the future.<br /><br />if this is the case, then at the speed of light, you would look to be stopped in time to the outside world. <br /><br />Theories are that a person can reach such speed falling into a super massive black hole. One can pass the event horizon and still fall in before being ripped apart as long as the pull of gravity isnt that much different between the head and feet. They woould reach the speed of light (or a significant fraction thereof) at the event horizon. Outside will see them frozen in time (the light after that cant get out, and what iws left is slowly stretched to infinity)<br /><br />If somehow you were to speed them up to above the speed of light. the outside world would actually view them getting younger!<br /><br />So... time travel to the past must require not speeding up a person, that sends them to the future. you must slow them down. completly, every atom moving slower. At absolute 0, the atoms themselves will freeze in place, unmoving. To that observer, the world will look to slow down. 1 year to the outside world would be like 4 years to you At absolute 0, time would to you seem to stop.<br /><br />go slower than that, and the world will seem to begin going back in time.<br /><br /><br />SO.. Time travel to the future is possible. just need speed.<br /><br />Time travel to the past is possible.. if speeds under 0 can exist<br /><br />I suppose if you can get every atom in the body to vibrate the opposite way, spin the opposite way you can do it. They would measure with negative energy, and negative mass.<br /><br />This is called negative matter by the way 
time itself does not exist. It's all part of a space-time continuum. You can travel back in time if at the same time you travel so far way as not to be able to influence events from your own time-that is light would take longer to get from where you end up to where you started from than the amount of time you travelled back in the past. <br /><br /><br />I call it the Spacefire continuum potential limit <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
Continuity screws up everything for time travel. For the sake of arguement let's say you could travel to the past or the future. How would you get back to the present if time or spacetime is continuous and you can never identify the precise instant that is the present?<br /><br />In order to arrive back at the "correct" present you need to know the precise instant in time that is "now", or the precise point in space time that corresponds to "here and now". Continuity means that you can always divide something into ever smaller pieces. As a result it is impossible to identify a unique piece of time or spacetime as the "present".<br /><br />If there is even a tiny amount of error in your calculation you will end up missing "here" and/or "now". You will end up slightly in the past or slightly in the future. <br /><br />In other words, the people who are waiting for you to return from your time traveling would think that you never returned because you would no longer occupy their "here" and their "now".
I see your point. And if you add space travel to that- you get a whole mess. <br />My theory is based on the fact that time and space travel are connected-just like the spacetime continuum, then- if you want to come back to the present you will have to travel a certain distance in space(maybe back from the direction you originally came from) as well.<br />basically you can't exist in the past anywhere near where you exist in the present, and this avoids time paradoxes. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
Here is another something to toss into the mix.<br /><br />any theoretical time travel will have to also include a 100% understanding of the motion of the earth, the sun, the galaxy, the local group, the supergroup, ect ect.<br /><br />Realize.. that if you were to stay in the same place in Space, and move through time... the poor solar system would wiz away from you so fast you would think you were on star trek. Everything is moving through space.<br /><br />so.. time travel will only be theoretcially possible once we have a 100% knowledge of everything in the solar system, how they affect eachother, and add it into a spacial-temporal equation that also includes quantum mathematics.<br /><br />but then, by that time we will know if it is still possible in theory.<br /><br />Lets work on finding the grand unified theory first before worrying about time travel
"Lets work on finding the grand unified theory first before worrying about time travel "<br /><br />I say....lets find a grand unified FACT - too many theories around already <img src="/images/icons/wink.gif" />
If every action truly does have an opposite and equal re-action, then ANY time travel would alter the course of history, whether we can kill our grandfathers or NOT.<br /><br />But , who is to say that yesterday I didn't have 6 brothers and today I only have three because 3 were removed by time travelers.<br />
I think you're all being misled by the implications of this theory.<br /><br />In physics, because something is "possible" doesn't mean that you'll ever actually see it. What this theory says is that time travel is not <b>precluded</b>, but that doen't mean it can actually ever be utilized. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis: </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
"What this theory says is that time travel is not precluded, but that doen't mean it can actually ever be utilized."<br /><br />If it is not precluded then it is possible, if it is possible, it will be done. <br /><br />Is it not possible that we (Earth) are the most advanced civilization in the universe? Or at least close to the most advanced civilization in which case we have have not seen any time travelers because the technology has not yet been perfected?
Lewcos, there are numerous paradigms in Physics that show something is possible, but thoroughly unlikely. Recollect Tipler's time-travel method of using a vast, rotating cylinder of hyper-dense material? Or how time travel might be possible, presuming there was a toroidal-shaped singularity?<br /><br />Neither of which would be possible even for a type II civilization. And possibly not even a type III.<br /><br />Two classic examples of "possible, but virtually unlikely." <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis: </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
Is it not possible that we (Earth) are the most advanced civilization in the universe? Or at least close to the most advanced civilization in which case we have have not seen any time travelers because the technology has not yet been perfected?
In other words, <br /><br />If my model omits the details that preclude time travel then my model does not preclude time travel.<br /><br />Sounds like a weak paper.
Odd, as I'm certain I neither said that or implied that.<br /><br />Btw, "Weak paper?" Compared to the topic of this thread, and the complete lack of understanding of physical theory I've read?<br /><br />Another example of something possible, but that we'll never see:<br /><br />If we can achieve sufficient energy levels, we can recreate in microcosm the Big Bang. It's not even remotely precluded by physical theory.<br /><br />With the possible exception of the fact that achieve the energy levels needed would require re-creating the Big Bang. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis: </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
"Or at least close to the most advanced civilization in which case we have have not seen any time travelers because the technology has not yet been perfected?" <br /><br />You are missing the point when you say "because the tecnology has not yet been perfected." Perfected, WHEN? Next year, 1000 years, 1 million years, 1 billion years. If time travel worked, it wouldn't matter how far in the future it was perfected because people could then come back. I doubt there is time travel, and if there is, whatever the person from the future did, has already happened. For example, if 20 years from now, you went back to your parent's wedding that happened 20 years ago, and posed in the group picture, if you looked at the group picture today, YOU WOULD BE IN IT! The problem with this theory is that it implies a steady state universe, i.e., everything that has ever happened or will ever happen, is happening right now. It is difficult, if not impossible to reconsile this with the expanding universe and evidence of the big bang that we see.<br />
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