Time travel without paradox

[spacecadet2563]

Time travel is logically possible. IF you moved faster than light or even a little less with time-dilation taking effect you live on another timeline. It is not synchronized with those on Earth.Therefore events that happen on Earth like killing your parents before birth cannot reach you. True?

 

[.Scott]

If your parents were killed before you were conceived, you are going to have a hard time travelling.

Regarding you more general time-travel question:

If you want to get technical, there is the no-cloning theorem. It's hard to imagine sending any quantum information back in time without that resulting in two instances of the same quantum state existing at the same time.

Or this:

Let's say that you successfully sent a message back in time. Of course, such a message cannot change events in the past so dramatically that it stops the message from ever being transmitted. Also, you are now living this alternate time line and so you have no clue what alternate history you just over-wrote.

If there was a purpose in sending that message, then you have a problem. Either the purpose was served - leaving you with less reason to send the message. Or the purpose was not served, leaving you with no evidence that the message was sent.

So, in order to be effective and still be recognizable as a time message, the message would have to describe both potential time lines - the one that you want to avoid and the one that you are hoping for - and suggest the action that needs to be taken or avoided. And when that message is resent, it would have the same information but it would be the time line you believe you avoided, the one that you want to preserve, and how you preserved it.

But what kind of convincing evidence would you have that you succeeded? Perhaps the next lottery winner will claim time-travel as his winning strategy.

 

[Ibix]

This was initially posted in SF&F, which is the place for it, I think.

You can describe spacetimes which include paths where you can meet your younger self. Since such spacetimes are a 4d description of everything, they would necessarily fall into the "cannot change what happened" model. They are probably not physically realisable because they require exotic matter, stuff that violates the energy conditions, and we aren't remotely confident that this is possible.

 

[spacecadet2563]

This was initially posted in SF&F, which is the place for it, I think.

You can describe spacetimes which include paths where you can meet your younger self. Since such spacetimes are a 4d description of everything, they would necessarily fall into the "cannot change what happened" model. They are probably not physically realisable because they require exotic matter, stuff that violates the energy conditions, and we aren't remotely confident that this is possible.

No. There is no meeting a copy of you that would be your younger self. The traveler is moving back & forth along the timeline.

 

[spacecadet2563]

If your parents were killed before you were conceived, you are going to have a hard time travelling.

Regarding you more general time-travel question:

If you want to get technical, there is the no-cloning theorem. It's hard to imagine sending any quantum information back in time without that resulting in two instances of the same quantum state existing at the same time.

Or this:

Let's say that you successfully sent a message back in time. Of course, such a message cannot change events in the past so dramatically that it stops the message from ever being transmitted. Also, you are now living this alternate time line and so you have no clue what alternate history you just over-wrote.

If there was a purpose in sending that message, then you have a problem. Either the purpose was served - leaving you with less reason to send the message. Or the purpose was not served, leaving you with no evidence that the message was sent.

So, in order to be effective and still be recognizable as a time message, the message would have to describe both potential time lines - the one that you want to avoid and the one that you are hoping for - and suggest the action that needs to be taken or avoided. And when that message is resent, it would have the same information but it would be the time line you believe you avoided, the one that you want to preserve, and how you preserved it.

But what kind of convincing evidence would you have that you succeeded? Perhaps the next lottery winner will claim time-travel as his winning strategy.

I am just trying to say things are possible. If you go back in time and make changes that do not affect you than you are safe. If you did your parents in there is the idea of suicide. Physics would allow this. Just an example: if I drop a ball it takes time to hit the ground. Cause &effect. If time stopped after I dropped the ball you would not see it hit the ground. For you the effect does not take place. Point is if you live on a time dilating timeline any changes you bring to another will not reach you.

 

[DaveC426913]

If you go back in time and make changes that do not affect you than you are safe.

What determines whether changes you make affect you?

In principle, anything that happens within your past light cone can affect you. That light cone expands at 186,262m/s in all directions, meaning after just one second, anything your time traveling self does within 186,262 miles of you can affect you, by traveling back only one single second.

If you travel back ten years, your light cone spans 10 light years (59 trillion miles) in every direction. That means any event within ten light years in any direction can affect you.

 

[spacecadet2563]

What determines whether changes you make affect you?

In principle, anything that happens within your past light cone can affect you. That light cone expands at 186,262m/s in all directions, meaning after just one second, anything your time traveling self does within 186,262 miles of you can affect you, by traveling back only one single second.

If you travel back ten years, your light cone spans 10 light years (59 trillion miles) in every direction. That means any event within ten light years in any direction can affect you.

There are many events that take place that are no where near that fast. Also, to make you perfectly immune to any changes or effects if you were traveling faster than light than obviously not an issue. Quick answer.

 

[Dale]

you live on another timeline. It is not synchronized with those on Earth.Therefore events that happen on Earth like killing your parents before birth cannot reach you.

Please review the rules about personal speculation. This thread is closed.