What is time travel

Amazingly, particle physicists have to take this time dilation into account when they are dealing with particles that decay. In the lab, muon particles typically decay in 2. But fast moving muons, such as those created when cosmic rays strike the upper atmosphere, take 10 times longer to disintegrate.

The next method of time travel is also inspired by Einstein. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves. As you get closer to the centre of the Earth, for example, the strength of gravity increases.

Time runs slower for your feet than your head. Again, this effect has been measured. In , physicists at the US National Institute of Standards and Technology NIST placed two atomic clocks on shelves, one 33 centimetres above the other, and measured the difference in their rate of ticking. The lower one ticked slower because it feels a slightly stronger gravity. To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. Assuming you had the technology to travel the vast distances to reach a black hole the nearest is about 3, light years away , the time dilation through travelling would be far greater than any time dilation through orbiting the black hole itself.

The most mindblowing thing, perhaps, is that GPS systems have to account for time dilation effects due to both the speed of the satellites and gravity they feel in order to work. Another way to time travel to the future may be to slow your perception of time by slowing down, or stopping, your bodily processes and then restarting them later.

Bacterial spores can live for millions of years in a state of suspended animation, until the right conditions of temperature, moisture, food kick start their metabolisms again.

Though completely stopping your metabolism is probably far beyond our current technology, some scientists are working towards achieving inducing a short-term hibernation state lasting at least a few hours. Hawking was skeptical about the feasibility of time travel into the past, not because he had disproved it, but because he was bothered by the logical paradoxes it created.

In his chronology protection conjecture, he surmised that physicists would eventually discover a flaw in the theory of closed timelike curves that made them impossible. In , he came up with an amusing way to test this conjecture. Hawking held a champagne party shown in his Discovery Channel program , but he only advertised it after it had happened.

His reasoning was that, if time machines eventually become practical, someone in the future might read about the party and travel back to attend it. But no one did — Hawking sat through the whole evening on his own.

This doesn't prove time travel is impossible, but it does suggest that it never becomes a commonplace occurrence here on Earth. One of the distinctive things about time is that it has a direction — from past to future. A cup of hot coffee left at room temperature always cools down; it never heats up.

Your cellphone loses battery charge when you use it; it never gains charge. These are examples of entropy , essentially a measure of the amount of "useless" as opposed to "useful" energy. The entropy of a closed system always increases, and it's the key factor determining the arrow of time.

It turns out that entropy is the only thing that makes a distinction between past and future. In other branches of physics, like relativity or quantum theory, time doesn't have a preferred direction. No one knows where time's arrow comes from. It may be that it only applies to large, complex systems, in which case subatomic particles may not experience the arrow of time. When two quantum systems enter into temporary physical interaction, mutually influencing one another through known forces, and then separate, the two systems cannot be described again in the same way as when they were first brought together.

Microstate and macrostate entanglement occurs when an observer measures some physical property, like spin, with some instrumentation. The rule, according to the orthodox or Copenhagen interpretation, is that when observed the state vector the equation describing the entangled system reduces or jumps from a state of superposition to one of the actually observed states. Instead, some no-collapse interpretations claim that all possible outcomes of the superposition of states become real outcomes in one way or another.

In the many-worlds version of this interpretation Everett, , at each such event the universe that involves the entangled state exfoliates into identical copies of the universe, save for the values of the properties included in the formerly entangled state vector.

The many universes are collectively designated as the multiverse. Many natural time travel stories make use of these many-worlds conceptions. A natural time traveler in a many-worlds universe would, upon their return trip, enter a different world history. This possibility has become quite common in Wellsian time travel stories, for example, in Back to the Future and Terminator. These types of stories suggest that through time travel we can change the outcome of historical events in our world.

The idea that the history of the universe can be changed is why many of the inconsistencies with causation and personal identity arise. We now turn to these topics to examine the philosophical implications of time travel stories. Inconsistencies and incoherence in time travel stories often result from spurious applications of causation. Causation describes the connected continuity of events that change.

The nature of this relation between events, for example, whether it is objective or subjective, is a subject of debate in philosophy. But for our purposes, we need only notice that events generally appear to have causes. The distinction made between external and personal time is crucial now for the difficulties of causation in some time travel stories.

Imagine Heloise is a time traveler who travels 80 years in the past to visit Harold. The difficulty arises when we test the consistency of the story in external time, because it involves an earlier event being affected by a later event. The activity of Heloise is causally continuous with respect to her personal time but not with respect to external time assuming that the continuity of her personal identity is not in question, as we shall discuss in the next section.

With respect to external time, this story describes reversed causation, for later events produce changes in earlier events. How does the story change if Heloise is homicidal and encounters her own grandfather 80 years ago?

This is a scenario many think show that time travel into the past is inconsistent and thus impossible. Heloise despises her paternal grandfather.

Heloise is homicidal and has been trained in various lethal combat techniques. Despite her relish at the thought of murdering her grandfather, time has conspired against her, for her grandfather has been dead for 30 years.

As a crime investigator might say, she has motive and means, but lacks the opportunity; that is, until she fortuitously comes into the possession of a time machine. Now Heloise has the opportunity to fulfill her desire. She makes the necessary settings on the machine and plunges back into time 80 years.

She emerges from the machine and begins to stalk her grandfather. He suspects nothing. She waits for the perfect moment and place to strike so that she can enjoy the full satisfaction of her hatred. And that means that Heloise will not be born.

But if she never comes into existence, then how is she able to return…? If so, then we avoid the paradox. So the paradox of causal continuity in external time does not arise; causation presumably connects events in the different universes without any inconsistency. But as we shall see in the next section this quantum interpretation trades-off a causation paradox for a personal identity paradox. Can Heloise murder her grandfather?

The sense in which she can murder her grandfather refers to her ability, her willingness, and her opportunity to do so.

But the sense in which she cannot murder her grandfather trumps the sense in which she can. In fact, she does not murder her grandfather because the moments of external time that have already passed are no longer separable. Assuming that events 80 years ago did not include Heloise murdering her grandfather, she cannot create another moment 80 years ago that does. A set of facts is arranged such that it is perfectly appropriate to say that, in one sense, Heloise can murder her grandfather.

However, this set of facts is enclosed by the larger set of facts that include the survival of her grandfather. Were Heloise to actually succeed in carrying out her murderous desire, this larger set of facts would contain a contradiction that her grandfather both is murdered and is not murdered 80 years ago , which is impossible.

History remains consistent. According to his so-called Chronology Protection Conjecture, he claims that the laws of physics conspire to prevent macroscopic inconsistencies like the grandfather paradox. If Hawking is right and many-worlds quantum interpretations are not available, then is time travel to the past still possible? A causal loop is a chain of causes that closes back on itself.

This sequence of events is exploited in some natural and Wellsian time travel stories. It is a point of debate whether all time travel stories involving travel to the past include causal loops.

As we have seen, causal loops can occur when extraordinary cosmic structures curve spacetime in a negative direction. Wellsian time travel stories with causal loops describe scenarios like the following one by Keller and Nelson Jennifer, a young teenager, is visited by an old woman who materializes in her bedroom.

The old woman describes intimate details that only Jennifer would know and thus convinces Jennifer to pursue a professional tennis career. Jennifer does exactly as the old woman suggested and eventually retires, successful and happy.

One day she comes into the possession of a time machine and decides to use it to travel back in time so that she might try to make her teenage years happier. Jennifer travels back into the past and stands before a person she recognizes as her younger self.

Jennifer begins to talk to the teenager about her hidden talents and the bright future before her as a tennis professional. At the end of their conversation, Jennifer activates the time machine and returns to her original time. The story contained within in the causal loop is presented on the left side. At event C, the story splits, with the causal loop continuing along C1, and the exit from the loop beginning at C2.

At C2, the worldline of Jennifer continues outside the causal loop events. What is the problem with the story? Each moment of the causal sequence is explicable in terms of the prior events. But where or when did the crucial information that Jennifer would have a successful tennis career come from originally? While each part of the causal sequence makes sense, the causal loop as a whole is surprising because it includes information ex nihilo.

It is controversial whether such uncaused causes are possible. Some philosophers for example, Mellor, think that causal loop time travel stories are impossible because causal loops are themselves impossible. They argue that time and causality must progress in the same direction. Still other philosophers for example, Lewis think that causal loops are possible because at least some events, like the Big Bang, appear to be events without causes, introducing information ex nihilo. According to Hawking, causal loop stories that employ CTCs are like grandfather paradox stories.

While backwards causation might be logically possible, it is not physically possible. The laws of physics conspire such that natural time travel into the past thwarts backwards or reverse causation. In closed spacetime, the Cauchy horizon of a CTC acts as an impenetrable barrier to a timelike worldline for objects.

If a time traveler could travel to the past, whether or not that past included their younger self, they are prevented from interacting with the events of the past. If causal loops are possible, then the objects may interact with the events of the past, but only in a consistent way, that is, only in a way that preserves the already established events of the past.

Causal loops, like any other aporia of uncaused causes, occupy the inexplicable perimeter of philosophical thought about causation. Nevertheless, causal loop stories like that of Jennifer raise another issue: personal identity. The old Jennifer travels back in time to talk with her younger self. Are there two Jennifers or just one Jennifer at event A? At the same moment in external time, a young Jennifer and an old Jennifer are separated by a distance of a few feet. At that moment, is there one person or two?

Identity theory involves the relationships between the mind and the body that attempts to show the connection between mental states and physical states see the entry Personal Identity.

It tries, for example, to describe and explain the connection if any between mind and the brain. Our cognitions change according to the requirement of causal continuity. These mental states occur in personal time. For everyday purposes, we can ignore the distinction between personal time and external time; personal time and external time coincide. In the case of Jennifer, it is therefore proper to say that at event A in her life, there is only one person, even though it is also true to say from an external perspective, that she has two different bodies present at event A.

Regardless, in her personal time, the causal continuity of her perception and thus mental states is consistent. In the sense of external time, from the perspective of their surrounding world, there are two Jennifers at event A. DO NOT change the future. One wrong person to ruin it for the rest of us. On the point of time reversal, it is evidently impossible. The Uncertainty Principle prohibits spacetime reversal. The Universe is unable to remember its past as a consequence of the Uncertainty Principle , therefore the Universe cannot reorganise itself.

Can I have to go on my past with another time travel it is a possible when just tell me about one thing that can I have to go in my past one year. All you really need is a crystal diode with 16 sides, a large pain of glass, and a frequency transmitter near a bathtub full of ice cold water….

The Magnetosphere kills 2 birds with one stone- it protects earth and it records human time:. Mystery solved and I will explain, I was in a coma 3 months and I experienced things, I traveled time forward and backward, it is not a one way ticket.

Movies and songs are recorded on magnetic tape in a VCR tape Cartridge or Cassette tape, Magnetic tape recording works by converting electrical signals into magnetic energy, which imprints a record of the signal onto a moving tape covered in magnetic particles.

Revolution and Rotation is the motor VCR. When a person dies, their Spirit- MIND Thoughts, Feelings, Urges Physical and mental personality breaks out of human body- a stopped heart is what releases the spirit from the human body. Then the Soul Life with the memory of your existence in it breaks out of spirit and goes back to your birthday with a erased memory, meanwhile your spirit goes back in time to when you were a teenager starting the mental puberty, maturity from that adult spirit you died with in last life.

Mr Snow, I believe you as I have seen it too. As humans we have deep knowledge of things we cannot rationally explain but you have done a great job here. I thought that Analogy would be a better and easier way to explain, or in a picture of the earth from far out in space with the atmosphere around it looks like a DVD disk and the earth being the center sticker but is in 3D.

Actually you are on to several things here. I have also had the infusion of knowledge that also had to do with comparing life to recorded movies and music. I know you were using it to explain your theory, but I do think there is something there, I always have. When you watch a movie you are seeing the past. Access to a Quantum Computer Network on the web would be a good start.

A series of ChatBots and webhook sites strategically placed in not only space, but in time. A series of algorithms and I think information can be transferred backwards to ones self….

We all travel into the future daily. When we look at the stars now it is what they looked like years ago so what if we go to the stars and look down? You cant go to the stars. It will just take billions and billions of years to go even to the next nearest star than our Sun- proxima centuri.

Sorry to say, but do you think that you will be alive all those years?? You can do that without going to the stars… our planet reflects light as well thus making it visible from other parts of the universe….

Contact me on my hangout I will help you dareosuolale gmail. Please help me to time travel, can I see myself when I go back in time like Harmaini sees herself in Harry potter?? Or can I send messages to myself I know the particular date when to send. I want to go back in time to save my wife. Please help me. We have to lose something the past to gain something the future in time travel. Time cannot be played with. Am I correct.

I would rather die to bring those moments back…. The fact that no one has time travelled to the past is the proof that time travelling will NEVER exist.

Others have. Portals open most of the time. Example: Miami Fl. Magnetic Material gets bombarded by the sun.

Which fractures and formed portals within that area. Ley lines can lead to the portals of travel within miami for just to start. One can laugh or wonder if. In my experience jumping for the better the word of it Movie Jumper can be done. You can either Teleport or Time Travel. Our sun open these portals everyday. The best time when Sun spots start to emerge. All that electrons traveling at light speed is enough to rupture our magnetic fields on Earth.

You will return of course. Like water on a lake or an ocean time will corrects itself. Your inner clock is your ticket back home. With a little math,fourth dimensional thinking,a magnetic meter, the right location,history research and luck. You may get to expirence it. First clue…. You need a bag of hyperlink modules to start, then nuclear beepbeep gatangas, when you have that come back here and I will tell you what you need next.

You need high voltage beepbeep gatangas and a large broonasic magnet of about Gauss, come back here when you have these and I will tell you the rest. If you rotate the center of the earth in the opposite direction, then the whole earth can be moved back in time, on the other hand, if you move the center of the earth and change its position by separating it from the part of the earth, then you will be able to time correctly.

Yes it becomes a history but my life also in the past changes and the present also with it. I was forced, not given any option, my father and brother gave me wrong information and had no concerns for me.

It was just survival for me. I repent for not killing myself when I had time, but now if I have a chance why not. I heard from a guy in Idaho that time travel is possible. I think u need a black-hole-proof spaceship, go to the centre, escape the black hole and viola! You are now in the past.

Believe me you time travel! If not physically then you do mentally,like you through dreams. So what if time travel is the reason that we now believe there are other realities in our own world. Time in the future it is faster then now. The past is slower so you can travel. It is up to you. One way is to meditate. You can travel and see any body you want right now. You can fly faster then light. That is one way.