How does time travel work in Babylon 5?

Question

I've recently watched Season 3's War Without End, Parts 1 and 2 (spoilers about that episode in this question) and while I enjoyed it, I became confused about how time travel is supposed to work in Babylon 5. Particularly:

• Delenn and others say that they must use the White Star to save Babylon 4 because they "have already done it" (kind of a variation on the predestination paradox)
• At the beginning of War Without End, Part 1, Babylon 5 receives transmissions from 8 days in the future as the station is being destroyed, suggesting that other futures can happen. Also it implies that their timeline is not the first (i.e. if that future had not "happened" already, they would not be doing what they were doing)
• Despite knowing that they have "already done it", the characters strongly believe that they have a free will choice to save Babylon 4 and if they don't, the bad future will come to pass. This is consistent with statements like that of the Centauri seer in Season 1's Signs and Portents who indicated that there are different possible futures and that we have choices to change it.
• Despite knowing both that the Shadows were defeated 1000 years ago and that they will in the future send Babylon 4 back in time, Delenn specifically states that if they don't save Babylon 4, the Shadows will have won the first war in the past.
• Sheridan "slips into" his body in the future in which they have already won the Shadow War and future Delenn has already heard future Sheridan tell her about this meeting. And yet despite knowing that a future Sheridan told her about this very meeting, future Delenn still believes past Sheridan can change things and warns him not to go Zha'ha'dum.
• I seems that Valen only exists because Sinclair knew that Valen existed. There doesn't appear to be an original timeline when Valen doesn't exist and there is no causality. And if Minbari reincarnation is to be believed, this also creates a boostrap paradox with Sinclair's soul: Sinclair was born with a Minbari soul, Sinclair became Valen, and then Valen's soul was reincarnated into Sinclair a thousand years later.

In most time travel movies and novels (the ones that don't take a wibbly-wobbly timey-wimey approach), there are at least some consistent rules and you can generally say "time travel works this way, and you're just not supposed to think about X problem".

However with Babylon 5, it's not clear what those rules are. Sometimes it seems the future (or past!) can be changed, sometimes it does not. Sometimes it seems like they have a free will choice to change the timeline and sometimes it does not. Sometimes it seems like there is an "original timeline" and sometimes it does not.

Suffice to say, I find it fairly confusing. So could someone explain how time travel works in Babylon 5?

Answer 1

Spoiler Warning: There's a lot in this answer that won't be clear until later on in the series. Once you're past the middle of Season 4, you'll be in the clear for all the spoilers in this answer.

---

As I understand it, time in Babylon 5 is a kind-of (TVTropes) RubberBandHistory that additionally has some Schrödinger's cat uncertainty going on. You can alter the timeline as long as it does not change what you know/have experienced. And because of the RubberBandHistory, the further back in the past you go, the more likely you can make large changes.

Until they have acted one way or the other in War Without End, the amount of forces the Shadows have at their disposal is unknown and can change by their actions in that episode - but there is indeed only one single timeline.

---

Why this works with traveling back in time in War Without End:

At the end of Season 3-ish, Sheridan learns the Shadows' stated intentions and why they act the way they do: By antagonizing the younger species and sowing discord among them, only the strong survive. This is why they don't full-on attack until later, and why it doesn't matter how the previous war ended:

In the resulting timeline that we know, they lost the war and were pushed back to Z'ha'dum, where they lay dormant for a thousand years.

In the timeline that didn't happen, they would have voluntarily retreated to Z'ha'dum after that round against the Vorlons was over. Except this time with a lot more forces at their disposal in the present.

Either way, modern events would have been able to play out largely the same way because the Shadows and Vorlons weren't directly interfering anymore. The only alterations that Sinclair/etc's actions to the past could make were to their future, which, for them, had not yet happened.

So yeah, if the timeline is close enough to what happened before, events are likely to converge back towards the "real" timeline, leaving your past unchanged. So while these were later pointed out as production mistakes, on-screen they provide evidence towards RubberBandHistory:

• Zathras did not appear in the middle of a conference room as stated in Babylon Squared, but was caught rummaging through supplies
• Delenn's dress changed colors
• The reason Babylon 4 stopped during Babylon Squared changed (letting people off / accidental time-travel), although this may have been a white lie by Zathras.

---

Using the White Star wasn't so much predestination paradox as plain necessity. They had to take out the Shadow ships that were manoeuvring the bomb into place, and could not risk being recognized.

---

The reason for Delenn's warning happens at the start of Season 4:

I think this was just wishful thinking on her part. The jump forward in time was near the end of Sheridan's life, and if events at the end of Season 3/beginning of Season 4 at Z'ha'dum did not happen, there was a very good chance he would have lived a much longer life.

Because Delenn would have been directly affecting her own past, I don't think she could have convinced him not to go to Z'ha'dum. Whether or not she could, the possibility probably still existed in her mind because:

Some of what was stated by the characters can't be taken at face value because the Minbari only have the most rudimentary understanding of it at the point the series takes place:

Do the Minbari have time travel?
They've played with some research in this area, but they aren't anywhere near the tech required to actually do anything with time.

Answer 2

I've watched the whole series a few times (though not the movies, I admit), and I don't think time travel is ever addressed outside of the episodes where it occurs. I don't recall any other scenes where the characters tried to puzzle out the meanings and implications of time travel, so all we have is the events themselves. All we can do is speculate. Here's my speculation, which is full of spoilers so read at your own risk.

Some key points:

1. A victory by the Shadows in the past wouldn't mean the end of civilization. It would just mean more of the same - cycles of growth and destruction.

2. The Great Machine didn't just sit and wait. The caretaker and the attendants were keeping a close eye on everything going on in the civilized universe.

3. Kosh-1 and Lorien have both been around a really long time. They were around the last time the Shadows came out to kick over the ant-hills.

4. So were the Minbari.

5. Outside of the closed circle caused by sending B-4 and Sinclair (and Zathrus) back, nobody knew for sure what would happen. Would B-4 be enough to defeat the Shadows? Would there ever be an end to the cycles? Nobody knew - not even Lorien or Kosh-1.

There was an original time-line. In that time-line, a thousand years ago, there was no B-4 and the Shadows were free to do what they'd done who-knows-how-many times before - tear down civilization, weed out what they judged "weak" species and force the survivors to rebuild "better", then retire back to Z'ha'dum to wait 'til the next cycle. I think their plan worked this time, in a way they didn't anticipate. Some of the survivors must have figured out what the Shadows were doing, and built the Great Machine. Why? How? I don't know. I doubt that the Vorlons as a whole were involved, although Kosh-1 and/or Lorien may have been involved. (they may have felt that if the younger races had started to figure out what the Shadows and Vorlons were doing, it was time for the cycles to end). I like to think the Great Machine was built in a blind hope that, sometime in the future there would be a way to defeat the Shadows that the attendants of the Machine could send back to the earlier war. The Caretaker and his attendants (Zathras's) saw the construction of B-4 and the strength of the Minbari as that hope. That's why they sent B-4 back to the previous war.

Some of the religious caste of the Minbari, probably a very small inner sect, knew they were holding messages from the past but resisted the temptation to open them until the proper time, after the disappearance of B-4. Sinclair/Valen also kept the secret in the past, leaving only a few critical sealed messages to the future.

There was really only one time-loop, one Circle that had to BE closed, by Sinclair, for the plan to work. The circle could have been broken, leading to B-4 either not being built, built but not sent back, or built and sent back but destroyed in the past by the Shadows. Which would have led to the Shadows being much more powerful in the present time and destroying B-5, and a continuation of the increasingly pointless Shadow/Vorlon cycles.

Delenn's warning to Sheridan was simply an attempt to save the one she loved. Remember, outside of the B-4 closed-circle nothing was known for sure, so she had to try.