Wow, @TimB is over 4k in just 25 days? Impressive!

@MonicaCellio thanks for your input on the idea of collaboratively building a world. I started a chat room to discuss this and one of the first things that has occurred to me is that we'd need to be clear about what licence applies. For writing challenges on writers.SE do you use the same licence as SE or do you just avoid posting the submissions to the SE network?

@ivy_lynx are you sure every form of time travel ends with paradoxes?

I feel like I can think of a multiverse version that doesn't end in paradoxes

sketchtoy.com/63310323

is that comprehensible?

@overactor that's the multiple parallel universe hypothesis

@overactor BTTF used the same

Not always, if I remember correctly

@overactor a simple question to be posed there is, why do you go back in the primary timeline-universe when timetraveling from a branched universe, instead of the branched universe's past?

I seem to remember a newspaper changing in doc's hands

because they share the same past

@overactor @overactor that makes no sense if Doc's assumption about splitting timelines is correct

@overactor the simple objection is, if you get parallel universes, where do you go if you time-travel after time traveling once already? the new universe's past? or the old one's?

@ivy_lynx Depends on how far back you go

I tried this years ago and it basically ends with: you can never return to the original universe

no, that's true

you can't

That's problematic

@overactor @overactor but how is that decided? If someone from that universe time travels backwards, do they go back to your universe or theirs?

but not paradoxical

@ivy_lynx sec

sketchtoy.com/63310432

each color represents a universe you can travel in between

when the lines are close together, they are the same universe

@overactor Yeah but don't you see? This means that in any timeline there can only be 1 time travel from it and 1 to it, perhaps one of either - no more

@overactor yeah but now you're making new universes each time - thats a new universe, even if you go back 5 minutes

@ivy_lynx not really, you can always go back to before the first branch

@ivy_lynx yes

@overactor @overactor so you're making universes that have time snipped off?

@ivy_lynx snipped off?

@overactor yeah, as in, before time t, there is no time

@ivy_lynx No there is time

@overactor but noone can ever go to that time - if they go back, they go back to the main universe branch

the past of a branch is identical to the past of the original universe

then they split off there

in one universe, the time traveler appears, in the other, he doesn't

@overactor sec, I remember there was a reason I rejected this, I need a minute

I've gone over it many times, I'm fairly confident it works out

@overactor here it is: the original universe never sees the results of time travel

@ivy_lynx Exactly

well

@overactor so you can't time travel back, save your aunt and your aunt appears in your future

@ivy_lynx well

@overactor you can only wait until then

you can travel forward

I'll draw it up

@overactor but to which universe?

It creates many problems though

but no paradoxes

k lets see

sketchtoy.com/63310511

you and your aunt both disappear from the original timeline

oh wait

I forgot, in the branched timeline

there are two you's

Except for the period in time that you skip

the second you is of course unaware of the time travel and your aunt's death

@overactor but doesn't the other you have to time travel again in the future of the original timeline? Does a universe split again or is it ok because it's already created for this purpose?

sketchtoy.com/63310526

@ivy_lynx The future of the original timeline is already set

There is no more you past the point where you traveled back in time

Every time travel only happens once

@overactor but this irrevocably violates causality

@ivy_lynx I don't see why

@overactor the problem with time travel is the same problem with the warped space in general relativity: you need time to explain time, just like there, you need gravity to explain gravity, it's circular

@overactor well, if the original timeline doesn't happen, your time travel doesn't happen

@overactor but if it does happen, it has to happen infinite times

The original timeline does happen

see, you change the course of the branched timeline

@overactor yeah but if time is like space, another dimension (the only way you could actually travel through it), then doesn't that event have to stay there?

but you can't influence the timeline you came from

It would seem you're also traveling through a 5th dimention

@overactor this can work in one of two ways: everything is predetermined and has happened already - you get infinite universes with all possibilities, eternally static and unchanging OR

@overactor each group of actions has a causality line which is a timeline

well, determinism works with this theory

@overactor the first means there is nothing you can do that hasn't already happened somewhere in a branch, which pre-exists by necessity - the second means that all possible actions after travelling once end with infinite universes

that's not true

@overactor yeah but I don't think causality does - and if it does, time traveling becomes useless

@overactor how?

since you can only travel back in time once form every branch

you can only create one extra branch from each branch

since you end up in a newly created branch, there is no necessity for anyone to travel back in time from that branch

@overactor doesn't that mean that time travel happens once in all of history?

since the existence of that branch only depends on someone traveling back from another branch, one you can never reach again

There is one branch (the original one if you will) where no time traveler will ever arrive

@overactor my point is, that 1. you can never meet a time traveler 2. time travel is only useful to the time traveler

@ivy_lynx point 1 is not true

sketchtoy.com/63310589

Every time a time traveler goes back in time to a point where you are alive, you have a 50% chance of being in the branch where the time traveler arrives

why 50%? because there's two branches?

uhu

the splitting fo branches can also be seen as freak quantum fluctuations

Now here's a toughie

oh man, here we go with quantum again

forget quantum, the point is causality

you need events to happen in a sequence, otherwise, there's never a reason for one thing to lead to another

set up a machine to travel 2 minutes back in time in 3 minutes, and make sure no one can possibly interfere, even you

@overactor that's impossible - you can only get lucky

This creates an infinite amount of branches until it destroys the universe

of course that is even more theorethical

@overactor lets say it doesn't destroy the universe, you still need to reconcile branch targeting - which branch does everything go to? If it ends with infinite universes just because you can travel through time it's a bit of a crappy solution

@overactor cause then you need to explain all sorts of crap: who meets who in what universe, tiny differences and large differences, where you go to out of infinite destinations etc.

@ivy_lynx The thing is, you can't go back to the exactly the same point

There are bound to be things in the second branch that cause miniscule differences in the second branch compared to the original one

so you either end up right before or right after the split

@overactor well that can escalate though, it gets crazy pretty fast

either way, you create a 3rd branch

if you end up right after, there will be 3 machines

eventually sufficient branches will be created right after the last split to cause so much damage that it prevents the next time travel

hmm

if you go back, kill your parents, you create a branch where you never get born or go back in time - this means causality has to be preserved across universes.

@ivy_lynx in that branch, your parents will be dead and you will never have existed, but the you from the original timeline will be there

Traveling back before you were born prevents you from ever being born in that universe anyway

@overactor yeah that's what I mean, that makes your original timeline the source of causality for your existence

(that branch)

@ivy_lynx yop

It just feels useless - if you can't affect the world you're in with time travel and you can never return to it, what's the point?

each individual (or even particle has their own line of causality that can travel between branches

it like this branching thing preserves causality, but makes the effects of time travel nil

@ivy_lynx Well, if you don't travel back to far and either kill second you or convince him to also travel in time

you can end up in a very similar branch to your original one

here's an application though

Make a time machine with money in it

set it up to travel back in time 2 minutes in 3 minutes, unless there is another time machine present

Make sure you can not otherwise influence it

you have one in 2 chance of ending up with no money

but it won't land in your universe

1/2 chance of double money

you're not traveling with it though

that's assuming your 50% chances - if there's infinite branches because you've already done this in the future you never get anything

No, since the machine will only travel if it's in the original branch

@overactor how is that ensured?

otherwise, the other machine will appear before yours travels

and you've programmed the machine to only travel if it's not in the precense of another machine

@overactor you mean the machine has to know if there's another one before it travels?

@ivy_lynx well, it has to know there's no other one

sec

This is where it gets interesting though

set up the machine so it will travel 2 minutes back if no other machine is present

1 minute back if 1 other is present

not at all if 2 others are present

this creates 3 timelines

one with no money

one with the original amount of money

(since one arrives and one leaves)

and one with 3 times the original amount of money

(since 2 arrive and none leaves)

I'll draw it out

no I think I get it

I'm thinking about the chances thing, if it works out

sketchtoy.com/63310716

That's 4 times the amount of money for 3 timelines

That's a bet I'll take any day

Increase the amount of machines you'll tolerate to still do a time travel, your odds get better

Can you repeat how the 50% chances work in your model? I'm confused on the details

like when do you have 50% chances to land on a branch

@ivy_lynx Well in the future of your branch, there will be a time traveler

(this might be you, or even just a machine)

due to causality, this is already fixed

so the branched universe this will create already exists ina sense

when you get to this branch

there need to be 2 versions of you

one in the original branch where the time travel will happen

and one for the branch where the time traveler arrives

So you have a 50% chance of being in either branch

So if you time travel to the future, where you time travel again, you can either land on the branch your future self is time traveling from or the one they went to?

you can land on one of two branches, if you time travel to a future point where someone else has just time traveled?

@ivy_lynx yes

why aren't you just creating a new branch when you travel, in which the future traveler just disappears into a branch of that one?

@ivy_lynx Well that's another interpretation

but it works without that

but doesn't this mean the branches are fixed and unchanging?

@ivy_lynx Through causality, yes

the whole tree is fixed from the start because of causality

hmm...

You can have new branches when you travel forward in time if you want to

for symmetry purposes

but than time travel becomes even more yuck

isn't that an absolute necessity? you're altering that timeline by being there

and yours by time traveling

but there's no reason there should be one where you never arrive

sketchtoy.com/63310818

what I mean is, when you time travel to the future, there's a branch because you've altered the time of your universe by traveling

This causes no problems

@ivy_lynx But that was always going to happen

due to causality

then why have branches when you go back? if it was always going to happen, it should already have happened in your universe as well

That's because the causality loops

hence the branched universe

I'll show you the version where forward travel also creates a branch

be warned, the fun stops here

sketchtoy.com/63310837

ok so, so far, this means you can only meet time travelers who have traveled forwards already (and only forwards).

Hey, could I get some movie recs? I'm looking for film or TV where the idea of "spacecraft travelling near the Sun" is examined in some depth (so, not just slingshotting around it as a device to further the plot, but where being near the Sun is somehow important in itself).

@BESW I'm of no help there, sorry

@BESW in the plot sense or the physics sense?

The 2007 film Sunshine is the only one that's really come to mind so far.

@ivy_lynx No no, remember, whenever someone travels back in time, you ahve a 50% chance of being in the branch where he arrives

@ivy_lynx Either/or. I'm looking for background material to get my brain jumpstarted in designing an RPG campaign on the theme.

There's that star trek tng episode with metaphasic shields :P

@overactor I have trouble reconciling causality, time travel and chances

@ivy_lynx branches have no causality on their own

But the tree as a whole does

I think there's a crap c-movie where they make a craft that travels into the sun or some shit

Well, they have causality, but time travel breaks it in part

The whole tree preserves causality though

@ivy_lynx If you can track down a name...

We need the chance-to-land-on-a-branch thing to reconcile meeting time travelers right?

We're doing a game set in the Atomic Robo universe where they have to travel to an object on a collision course with the Sun, analyse it, and decide if they should let it hit the Sun.

@BESW I'd be as good as googling "movie sun craft center travel" and it's very likely it was the center of the earth instead because I have vague memories of that as well, just not sure if it was the same movie

Fair enough.

@ivy_lynx yup, but it's also a logical consequence of branching timelines

there's two yous, one in the branched timeline and one in the original

@overactor for forwards time travelers - with backwards you need chances

or you never meet them ever

@ivy_lynx uhu

there will always be one of you that's in the branched timeline though

You just have a 50% chance of being that person

If you want to see what the forward time travel creating branches too leads to:

sketchtoy.com/63310872

chances violate causality in this case though - what's the cause of you being in one branch or the other? (not the cause of you being in either, but the cause of being in a specific one)

I think forward time travel can happen without branching, it seems consistent enough

@ivy_lynx That's the minor problem with no branching when going forward

But look at it like this

If I clone a self aware computer program

tell one I love it

the other one I hate it

The computer program has a 50% chance of me loving it, right?

well if by computer program you mean both at the same time, yes

consider the odds of the computer program before I cloned it

There's only one there

love is undefined at that point

it's an error :P

@ivy_lynx Now you're being silly

here's what traveling forward in time creating branches too leads to eventually btw:

sketchtoy.com/63310891

@overactor I'm serious, you haven't told it about how you feel yet - what chances could exist for something that doesnt exist

@ivy_lynx causality states that what you'll say is already fixed though

do you mean, you tell it you love it -> clone it -> tell the clone you hate it?

no

Tell the program you'll tell him you love or hate him soon -> clone it -> tell one version you love it, tell the other you hate it

You can ask the program before the cloning if it thinks it's going to be loved or hated

wouldn't the chances of it thinking you love it be 50% at any point? both before and after?

there's no way of knowing

until you tell it of course

true

but after the cloning, it's fixed

the individual programms don't know it

you might not know it

that means cloning it has no effect on the chances though - so you have a 50% chance of landing on a branch if time travel is just possible at that point

but one of those programms is going to be loved and one hated

@ivy_lynx well, the cloning creates the chances

since if you don't clone the programm and 'randomly' pick love or hate

there was never really a probability

@overactor but then we go back to what I was saying, if cloning creates the chances, the odds have no meaning before cloning

because of causality

but causality states the the cloning has to happen

so it does

causality only breaks at the exact origin of the new branch

so, in your model, all branches are already there on all timelines

yes

because causality holds when you view the tree as a whole

doesn't this mean the 50% chances don't exist and are illusiory? you've already landed on a branch in the future

the 5th dimension if you will

It means consience is an illusion

Your consience will get split

but do the chances exist? is there a random chance in the actual 5-d universe or isn't there? if it's fixed, chances make no sense

and tries to figure out in advance in which branch it will end up

Which is a silly question, since you end up in neither

you only exist in an instant

you are the 'replaced' by something that resembles you the next isntant

The odds don't really exist if you view the tree as a whole

but they're a viable model if you want to see what happens form the persepective of 3d entities

this works great in a fictional setting, however, to model this strictly, you'd need to explain how a branch is chosen, if there are no real chances

although, really, that's only necessary if you want time travelers meeting other travelers

It's like a character in a choose your own adventure book wondering which ending it's going to get

i'd just say they don't because of branching and it's done

Well, you can meet other travelers

I'll show that too

sketchtoy.com/63311027

plenty of overlap

it does get messy soon

that makes sense i think

this is what I'm thinking: sketchtoy.com/63311048

gtg lunch, brb l8tr

bk

:P

Ah, the blue guy once again has a 50% chance of ending up in either

From his point of view

In reality, he ends up in both

@overactor @ivy_lynx just been reading your conversation and all the timeline diagrams.

Have you seen Primer?

Also for many worlds theory fiction I recommend Greg Egan's "Axiomatic"

hey guys, check worldbuilding.stackexchange.com/questions/2486/…

@AmitJoki why? because it's a question you asked?

@ivy_lynx of course yes.

TimB said to ask if the question is off-topic or not. I expected a reply whether it was on-topic here or not but there was no one in the room

@AmitJoki You being funny? I don't think @TimB asked you to do anything. I also think that when you expect something, you should ask for that thing specifically, not expect people to smell their own fingers and figure it out - "hey guys check this out" means nothing - it's advertising.

@ivy_lynx chat.stackexchange.com/transcript/message/17975469#17975469 I had asked everyone out there to help me out, I really expected them to be there and never expected you. Also, its another question on worldbuilding, I never expect you to go through the link, it appears on the feed, and there is "share" button on every question meant to reach wider audience. If you see the context which my transcript shows, how I was chatting. I didn't expect you to respond. Go through my transcript

Also... check out chat.stackexchange.com/faq#about

I don't need to explain you all this, but it was quite funny how you took things given the rooms I've been and how those users behaved and how you behaved

@AmitJoki I don't care if you like it - there's no reason to expect only people you like will be in a chat room - also, there's a list of those present to the right. The first transcript you posted doesn't point to a post that demonstrates TimB recommending you to come here. I am under no obligation to spend time trying to figure out where the post is, just as I have no obligation to figure out what you mean if you decide to not explain.

@AmitJoki How about you see what kind of votes your question is getting, before you attempt to present me as treating you unfairly

Well, downvotes @ivy_lynx

do you guys have any privilege like seeing deleted posts after 10k in SO?

@AmitJoki a number of aspects of your posting in both chat and main have things in common with spam. If that is just coincidence it will be cleared up soon, so you don't need to defend yourself. It just needs to be looked at as a standard process because of the warning signs. There is no need for hostility, and everyone is welcome here.

@githubphagocyte sorry, looks like I just missed you last night. For the weekly writing challenges (which are short works), people post wherever they want and link in chat. Sometimes people write directly in chat and that's covered by the CC-SA license, but some deliberately post off-site to avoid getting mixed up in that.

We use chat to coordinate, and try to compile links on meta (though coverage has been erratice).

@githubphagocyte yeah! Of course, I know these kind of things exist in SE..(I'm a regular in SO) I'm in the process of creating a meta post. And please do flag that user, for I know nothing about him.

There's a scheduled chat in our main room every Tuesday at 17:00 UTC, BTW -- feel free to drop in. Somebody throws out a topic and people write for 10 minutes on it, then share and discuss.

I haven't caught up on the shared WB project yet, but since it's a collaborative work people would need to agree on a license anyway -- but it needn't be SE's.

@MonicaCellio Thanks for this info. I've asked for feedback on what kind of licence people want for this, since it will be collaborative and sharing a single licence. We'll see what response there is in the new chat room when we're back into weekdays...

@AmitJoki yes I will flag otherwise they will make it look like you are involved - probably worth you flagging too to emphasise that you are not connected.

97 rep enough? @githubphagocyte

@githubphagocyte where to flag him? He hasn't answered anything nor has asked anything

@githubphagocyte heh -- I just dug that link out of the transcript right before you repeated it. Thanks for anticipating my question, even if there turned out to be a little lag.. :-)

@MonicaCellio Sorry to be just too late... I think you should see it in the starred posts list too (for now at least)

@AmitJoki yes you should always be able to flag. You can flag a comment if you consider it to be spam.

@AmitJoki It wouldn't be appropriate to flag anything other than the problem comment. Other questions or answers that are not causing problems should not be flagged as that will just cause confusion.

@githubphagocyte no need to apologize. I shouldn't have been so hasty. :-)

Ah yes, and there it is in the starwall.

@githubphagocyte flagged as - "This comment is making me look as a spammer as it points to my blog which I'd linked in my question. Now I've removed that too, as it is considered to be spam"

in others

@MonicaCellio It was one of those "sorry to hear it" sorries rather than worried I'd done anything wrong - I guess similar to your sorry for just missing my question yesterday. Unless that really was an apology, in which case there was no need to...

@AmitJoki yes I used others too, as I wasn't sure it would be clear without extra wording

@AmitJoki are you implying I'm the one who downvoted you? I'm not - it's interesting to complain about it considering your question has been flagged, has multiple issues and has been downvoted by more than 1 person. Perhaps I should downvote so that it becomes deletable.

@ivy_lynx when the hell did I even imply closer to that?

@AmitJoki I asked you if you did - if you're not implying that, what does "Well, downvotes @ivy_lynx" mean?

@ivy_lynx Well, again I ain't a native English speaker and I had no other wording to tell what's going on. What would you explain in your English when I ask "how is the question is fairing?" I don't know of any other wordings I'm afraid

@MonicaCellio Thanks Monica, I just answered a few questions :)

Whoah, I can't leave you kids alone for a minute - what's with all the drama? :p

@AmitJoki Unfortunately the question you posted is just asking people to brainstorm ideas for them in an insufficiently constrained option space - it's not a good fit for this site and it would have been closed pretty fast even if you hadn't deleted it.

@TimB looks like I stepped out at just the wrong time. :-( @ivy_lynx, @AmitJoki, I think you're misunderstanding each other.