If time travel is possible, then could we change the past?

How would you know that you had changed the past? Presumably upon arrival back in the 'future', all past events would have been just part of the normal flow of time, history in other words. I don't think you would exist 'outside' time, so it would be your reality as well.

I think, as I have said many times before, that the whole idea of timetravel is an idea born out of a misunderstanding of the word time.

The present is all that exists, and everything exists in the present. What we call past is our memories, and future is our hopes and anticipations. Time doesn't pass. We pass.

Assuming it were possible to time-travel
Two points:

1. Reality may be a network of infinite possibilities. If you went back and changed the past, say, prevented the 9/11 incident: you would then be on a different time stream where 9/11 never happened, no less real but totally independent of events in the time stream you came from. The two time streams would be identical prior to 9/11 but become completely separate afterwards. But that means that from that moment you prevented 9/11, you could never return to the same present you left.

2. Changing a specific event may not change the general event from happening. Say you went back in time and killed Hitler as a child. Perhaps social/historical forces would have pushed some other person into a similar role, and eventually have the same or similar result. The rise of fascism and WWII may have been delayed or slightly altered, but might still have happened.

If the timeline was already written, as is required in such a mindgame, who's to say that timetravel actually changed time?

Your example with Hitler. How do we know that your journey back to kill him was not fated, and that it would lead up to the events that brought him to power. You set out to change something and thought your journey was your idea, when, in fact, it was the only way Hitler could have come into power. Your first example is as torn from the eighties movie "back to the future", and there are countless other films that deal with the example I just stated. What all have in common is the twisted idea of what time is.

You could only change the part of time to which you are cognizant. If time is considered a 'dynamic', as implied in 'change' then there would have to be points of 'embarkment' and 'arrival' to realize past and future states. Treated under these conditions it becomes apparent that a third 'time frame' to be considered .... the transitional frame where 'change' might be percieved ... that would be aptly named 'the present'. When you apply these concepts it becomes apparent that to change the past would require presence in the future for knowledge of what is to be changed and implementation of the desired change .... then presence in the 'change' frame is required to undergo the change, remember, cognizance, you have to be aware of it to change it .... then a trip to the past to realize the change/s which requires a subsequent trip into the future to be able to realize the changes brought about by your initial changes.
All this was accomplished when the question was presented ....in other words the past is changed not in the past, but in the future.
Time is infinite, infinity stretches out in both directions ....and the only difference in past and future lies in he area of 'change' and that, we correctly or incorrectly, measure in lifetimes.

bringing this back to the forum you chose to post it in (philosophy);

life is the manipulation of 'time' by an individual; who, by so doing, alters the 'virtual past' of humanity.

[one way of looking at it]

Common mistake. Both directions you say? So direction is within the concept of time? I think not. This notion of yours stems from the belief that time is linear. Whyever would it be that? Infinity is not a size by the way. It is a term used to describe an action that has neither beginning nor end, namely the present.

Sorry, with the given parameter, past, there is only one other parameter that would fit ....with 'change' in the equation there would have to be something to change to .... future into past. As far as linear time, I am of the belief that all that is exist simultaneously in the area you rerfer to as present, I call change. In a 4 dimensional world it would be entirely different if time were the fourth dimension.
Direction .... semantics.

BTW ....infinity is a 'capacity, if you belive Albert. .

I am also of the belief that everything exists simultaneously in the present. Nothing can exist outside the present. If you were to somehow be able to revert the present to it's 1950 state(timetravel) you would only be extending the present to include this "place".

I wonder if This has anything to do with 'present' or 'change'?

As a musician I am well aquainted with the term time as a means of coordinating tones. In some cases, where you're operating with polyrhytmics, you have many different subdivisions of a single timespan.

For example, for those of you who know the song "seven days" by sting, you have maybe noticed how the drums keep two times blending them into one to create a really cool sound. The drums are in 5/4 time, and the hi-hat is in 4/4 time. These different counts coencide every 20th measure.

But no matter how much you divide and subdivide time, you will never escape the fact that we are merely spacing off our experiences so we can sense them in a timely fashion. The question then becomes wether this is done by our nature, or wether we have some control of it.

Maybe when you are having a deja vu then there time is splitting and two separate time lines are forming.The deja-vu is the indicator of a split occuring at that particular moent. Now there are two time lines forming the one where you choose to go and another.As Socratese said weather you can see it or not there is an equal and opposite to what seems to be 3d reality of ourselves and its surrounding.

in all probability the answer to the thread question, and the other two would be 'depends on the level of your awarness of time' which would certainly differ from person to person'.

I'm surprised that no one has yet brought up the matter of the famous paradox: suppose you go back to a time just before you were conceived and kill one, or both, of your parents. Then you would not be born. Therefore you are unable to go back and kill them because you never existed. Comments?

Merry Andrew, that paradox goes to show that the whole idea of timetravel is fantasy.

If you have a key and a drawer with a lock on it, is there any way to lock the drawer from the outside while leaving the key inside the drawer? (No holes in the drawer except the one you locked.)

As soon as the incidents occur almost after one another in time instead of years apart, the paradox suddenly reveals itself to be much clearer. Causality decides.

If time travel is possible then the past, present and future must all be linked to the possibility they can instantly change each other. So the mere possibility of a change in any of the past, present or future must be reflected in the physics of the other two.

This implies at a quantum level reality links all energy, particles and spacetime itself to both the past and future in determining our reality of the moment.

Is it possible to implement or impede a causality in time by not instituting a change?
With time travel as a given you go back in time and delay the instant of your conception by one month, then returned to your original time frame .... would you be returning to the past .... or the future?

This is all great stuff but then how did Nostradamus predict so many seemingly accurate perceptions of the future.Is is possible that the generating karmic landrover will spill out predicable happenings?

To understand it maybe we should look to the implications. To predict an event hundreds of years in the future would require a deggee of rigidity in how 'causality' or'branching' (my prior post) occurs in time, or 'plays out', if you will. Fewer branches .... more predictability to the point of bringing on a condition of 'fate' ... creating destiny.
Be that as it may, the ability to accuratly predict the future would be in all of us .... but, are we examing the right implications? Is there more to Nostradamus and Cayce than meets th eye?