[paigetheoracle]

How would we know if time travel was possible and being carried out by an external force? Our history on the outside and memory on the inside would be altered each time such a journey was made and the past interfered with but we, in the present, would have no proof this had happened because of the nature of the phenomena and its results upon us and reality.

Likewise, if the future was altered, how would we know because we wouldn't know what was there originally anyway (What to expect)?

[Jay-qu]

I have a theory, it may have many holes, but in the event it worked would proove time travel works!

It goes a little like this, get the exact date and time, write it down, remember it, then tell yourself that if time travel is to become available to yourself during your life time that you will come back to this time, lock yourself in your room and go to sleep, remembering the details of your room. The way I tried it I focused on the orientation of a poster, saying that if I came back I would put the poster upside down, alas it remained right way up, but like I said there are many holes

[Tormod]

Originally Posted by paigetheoracle

Likewise, if the future was altered

Altered from what, exactly?

[infamous]

For one to believe in time travel, they must also believe in determinism. That being true only, if there is just one future lying ahead for us to experience. However, if there is more than one future, possibily an infinite number in fact, the choices we make today may lead us into a future of our own choosing. Einstein conceptualized what he called 'World lines', this was an attempt to construct a rational understanding for the dimension of time. It may be that these lines of time intersect and we are able to change our future with the conscious awareness of our minds. In very simple terms, the conscious mind may have the ability to travel in time. Not in the strictest sense as to move forward or backward but, simply the ability to change future circumstances................................Infy

[Farsight]

I don't "believe" in time travel. I used to, but I don't any more. Let me explain:

If there's only one object in an otherwise empty universe, and it doesn't move, there's no concept of time or space. If it moves you can't tell if it's moving, so there's still no concept of time or space. But if it divides into two and the two portions move apart, now you've got a concept of time, and space. Because you can measure the movement against some other, regular movement that you call a clock, and you can create records. What you're measuring as time relies on a distance moved relative to another distance moved, which is your clock movement. So you've got your concept of time. But it is just a concept, constructed out of space and motion. There is no "other place" that is the past or the future, there's just this place with these things moving. Here. Now. You could wind back the motion so that the now looks like it used to, and kind of recreate the past. But you can't go to another place and find your moving things where they "used" to be. That's just your recordkeeping. They are where they are. There's no time. At least not the way you think there is. And no time travel.

Special relativity is where time starts. But it isn't the time you're used to. It's an attribute of space. Or more properly, spacetime.

IMHO.

[UncleAl]

How would we know if time travel was possible and being carried out by an external force?

Time travel violates causality. The universe does not tolerate contracdiction. No time travel.

Example: The ultimate star drive goes back in time as it goes forward in space. You can thus go anywhere in the universe within seconds by traveling at 2 mph. That is silly - and what happens to reality if two people try it simultaneously?

[KickAssClown]

Uncle AI, though usually right in this case you are only probably right.

Time as an arrow has no reason why is should go foward or backwards or left or right for that matter. I believe that the moment we expierence, is the moment which is consentually created by interacting localities.

Originally Posted by Muddled Time travel stuff which maybe full of holes, you have been warned. by KickAssClown

In theory, if I had the ability to travel bilaterially through time then quite simply any existence that the sum of states experienced would most likely be the actual observation. Keeping in mind that this is a causal universe and that any time event must be with cause that is external, or rather not itself.

This is to say that if I exist in superposition, all places all times, then the positioned me would expeirence the most likely events rather than the least likely.

I have wondered often, if I make a plan now about the future then and then take actions to get the plan to completetion on the future date, then by technicality I am altering a possible future. It boogles my mind to think that action I intend to take could have been (are, or something like that, our language is not built for talking in omniscences) influential on my previous states. That my future plans may be derived from my past plans and my past plans maybe derived from future events, passed subtly up and down the worldline.

What we then have is travel along the line of greatest probability, or the path of least resistence, depending on wheather your taking Quantum or Classical views.

-Esoterically far out... they wish they were geeks in love.
KickAssClown, keeping the world confused since 1986.

[InfiniteNow]

Part of the issue is a clear and concise definition of time, which itself is elusive. I can travel through a town because I have a clear idea of what a town is... how do I travel through time if I don't have a clear idea of what time is?


Living in the moment,

[Jay-qu]

Is it an illusion of our consiousness or an attribute of the universe that time seems to flow? Its like "If a tree falls in the woods and no-one hears it does it make a sound?" in this cast "If there is no-one to experience the flow of time, does time infact flow?"

[CraigD]

Originally Posted by paigetheoracle

How would we know if time travel was possible and being carried out by an external force? Our history on the outside and memory on the inside would be altered each time such a journey was made …

If a time traveler and any of his associates were not striving for secrecy, it would be easy to detect an instance of knowledge of a future event preventing that event - the typical "time travel paradox".

Example:
An airliner crashes with terrible loss of life and property. An investigation concludes that the crash was the result of the unexpected wear and failure of a specific part. Alice has a time machine. She uses it to travel back in time to before the crash, and, aided by specific information about the failed part, prevails on the airline to inspect the part. The unexpected wear is discovered, the part replaced, and the crash is avoided.

Although the future than Alice experienced doesn’t occur, it is clear to anyone with knowledge of the affair that time travel is the only reasonable explanation for her knowledge of the impending crash.

Alice needn’t physically travel into the past to realize this example – being able to communicate backward in time is sufficient.

Time travel/communication may or many not be possible. If it is possible, though, it should be noticeable due to lack of other likely explanation of knowledge of future events.