Vsauce, I’m Jake and if you could go back in time and stop yourself from being born,
would you?
Or should I say...can you?
Because if you went back in time and made it so you weren’t born then you wouldn’t
be alive to go back in time to stop your birth.
It’s the Retrosuicide Paradox.
If you went back in time to do this, it is something you can do but it isn’t something
you can complete.
I can go to the store to buy an avocado but it doesn’t mean I’ll leave the store with
one.
For time travel, the timeline self corrects in a way.
But...actually...I’m getting ahead of myself.
Let’s travel back to the beginning.
Vsauce, I’m Jake and time travel is a paradox itself which means that any paradox created
by the idea of time travel is paradox in a paradox, it’s The Paradox Paradox.
Allow me to explain.
With the Retrosuicide Paradox the idea is that things that have happened in the past
are fixed points.
They can not be changed because changing them would change all of time coming after that
past event.
And since you going back in time needs to happen there would be no way to follow through
with killing your younger self.
But that’s only if we assume time is one straight line where past dictates the present
and, if time travel were possible, the present would also dictate the past...it’s a self
fulfilling cycle.
We can travel in any direction of space but can we travel in any direction in time?
Australia and China both exist even though they don’t exist right here with me in this
location.
So one could argue that yesterday and tomorrow exist even though they don’t exist right
here...right now.
But the fact is, yesterday and tomorrow don’t exist.
I can’t revisit yesterday and I can’t skip forward into tomorrow.
Changing the hands on a clock changes your personal time but not external time.
External time is the rate at which time moves which is a constant, consistent rate.
When it comes to time being relative, that is personal time.
If you slowed down the rate of your body to such a degree that every function of your
being were affected, from your perspective people would be whizzing by but from everyone
else's perspective you would look frozen.
However, external time is still moving at the same rate.
It’s just your perception that feels different.
It is the Time Discrepancy Paradox, where there has to be a difference between time
and time...which we know there isn’t.
In most time travel stories it works like this:
Subject A leaves Point A and immediately, instantaneously, goes back in time to Point
B. Then after doing what they need to do, they come back to Point A. But this is where
another and more sinister paradox is created.
If we go back to this timeline, when Subject A goes back in time only they go back.
The version of them in the past, Subject A2 is still moving towards Point A when they
go back in time which means they have created a closed time loop in a way.
If Subject A travels back to right when they left Point A, Subject A2 will already be going
back to Point B. That instance will occur forever.
So everytime you travel through time you will always be creating a loop no matter if you
go into the past or the future because you right now are time travelling but you a day
ago, you a year ago, isn’t.
That you is still moving up on the timeline to that fixed point you created, Point A.
So it also begs the question, does that mean that if you left that timeline at Point A
and went to the past would you not exist in the present and moving forward or in the future?
Time doesn’t stop just because you aren’t there.
So instead of continuing on your timeline you have now imprisoned yourself or yourselves
into a loop.
Yes, you could come back to right after you left Point A the first time and continue forward
but now Subject A2, the other version of you, would do the same thing.
It creates an infinite amount of you that resets every time you hit Point A. Because
you take you in that moment in time.
So it creates another paradox, the double-occupancy paradox, which is how can there be more than
one of your current self?
We think of ourselves as oneself.
Also, side note:
This brings up an additional paradox which is the paradox of freedom.
Let’s say like in our scenario above, you, Subject A, travels back in time from Point
A thus creating a closed time loop where a version of you will always go back in time
once they reach Point A. You think that you were the one to choose to go back in time
at that specific moment...but were you?
If it is a closed time loop then you might not be subject A, but more statistically possible
is that you are Subject A20 or A5000.
So even though you felt like you had the freedom to choose that decision, it had already been
decided for you.
Ok, let’s go back to that timeline and imagine something different.
The most likely scenario is that only the present exists.
The past is gone and the future has yet to be written.
But as I mentioned earlier the past has been written so it could be that the past and present
exist but not the future.
In this scenario you could go back in time since the past did, by all accounts, happen,
you just wouldn’t be able to change it but if that were true than so would the third
scenario which is most commonly thought of when thinking about time travel.
That the past, present and future all exist and you can travel to them.
That would mean that all 3 - past, present, future - are happening concurrently.
The past and future aren’t being saved on a harddrive for us to revisit so think of
it as three timelines running on top of one another.
So when you go forward in time, it isn’t on your timeline.
It is on the timeline above you.
Important to note that if you left the present to go into the future you are now gone.
So if you spend a week in the future, there is a week in the present where you just don’t
exist anymore.
One of my favorite thought experiments about time travel is this.
If time travel were to exist then it has always existed as the physical machine can exist
at all points in time.
So even if it were invented 100 years from now it still exists now.
And since the beginning of time.
And it is important to remember, even in the 3 timelines theory, even if you went back
in time you can see the past but you can’t interact with it.
You can’t change it because it would still disrupt the present and future timelines.
However, there is another theory that allows time travel to not be a paradox and by doing
so would also make it so no time travel paradox would be paradoxical.
In this theory, if we revisit the first paradox we talked about, the retrosuicide paradox,
you’d go back in time and you could in fact kill your younger self and you would no longer
exist...on that timeline...but by doing that act the timeline splits.
So what was timeline 1 creates a timeline 2.
Timeline 1 has you go back in time and commit retrosuicide while timeline 2 continues as
normal.
Time has still self corrected itself by making a new copy of events as they were supposed
to be, timeline 2, not as you made them, timeline 1.
If this were true, we could be living on anyone of these timelines.
A fracture from the time we knew to one we think we know.
But we’d have no idea either way.
That means there are multiple timelines...an analogy in a sense for the multiverse theory,
that there are parallel universes and each time we travel through time we aren’t actually
moving through three concurrent timelines or new timelines are being created but actually
we are travelling to a different universe that’s similar to our own.
And if that’s the case...I need to keep traveling until I find
the right one.
And, as always, thanks for watching.