Does Starfleet know their kind of time-travel?

Question

Time Travel in Science Fiction has multiple variants to cope with its paradoxes such as the Grandfather Paradox, the most famous of them being

• the closed time loop, where anything that seems to modify the past turns out to already have been part of the past
• the parallel universe theory, where there basically is no paradox since the time travelling creates a new timeline existing in parallel with the original one
• the Back To The Future vanishing act, where the time travellers are basically slowly replaced by the new futures travellers, should they still be existing and travelling back in time, otherwise simply vanishing (this sentence should actually require some new grammar to better express the "will have would happening"-ish stuff)

To my knowledge, Star Trek's time travel usually obeys the multiverse theory, and another question's answer lists some post-TOS episodes where the conservation/loss of memories is treated. But my question concerns the Temporal Prime Directive (TPD):

When the TPD was established, were there any precedence cases known where the past was modified, and therefore, is the (pre-2009) star-trek universe a future that only came to be due to some time travelling?

Answer 1

Yes, for example in Star Trek IV: The Voyage Home Mr Scott gives a 20th century scientist the formula for transparent aluminium, which history in the main Star Trek time stream does say was invented by that scientist.

Answer 2

For a less-ambiguous example, in the first half of the Voyager two-parter Future's End, Janeway and Chakotay come to the conclusion you're asking about:

(Both reading from a Chronowerx Industries computer)

Janeway: Starling's computer designs were inspired by technology from the timeship. He introduced the very first isograted circuit in 1969. Two years after Braxton's ship crash-landed.

Chakotay: And every few years, there's been an equally revolutionary advance in computers, all from Chronowerx Industries, all based on Starling's crude understanding of 29th-century technology.

Janeway: Are you thinking what I'm thinking, Chakotay?

Chakotay: I wish I weren't.

Janeway: The computer age of the late 20th century-

Chakotay: -shouldn't have happened.

Janeway: But it did, and it's part of our history. All because of that time ship.

The point where the timeline was modified happened long before the Temporal Prime Directive was established, but the ship that went back in time (to Voyager's period, and then accidentally sent both even further back) was from centuries after it was established.

Answer 3

If you have multiple timelines, you have therefore multiple Starfleets (one per timeline) and is quite possible that each Starfleet might have a different knowledge of the other Starfleets; for example one Starfleet might know that they have one type of time-travel while another would have been unable to answer that question.

Futhermore, the Grandfather Paradox is not really a paradox. When you do time travel in the past, you use energy to travel back in time and the paradox can then simply be seen as a way of converting energy into a particular form matter using information provided by the time-travel machine.

Think of it like a teleporter where you would make a second copy of someone (or a changed copy if you manipule the information) by re-using the information used for the first transfert.; therefore creating a new person from "nothing" by converting energy into mass. Of course, you can argue that this can be possible or not depending on the way that the teleporter is working but in the case of time-travelling, all you need to know is that you are injecting energy into the time-travel machine each time you use it.

Each "present" will be different but this simply would reflect the loss of mass that had to be converted into energy for each time travel into the past (or the futur). The grandfather paradox exists only if your time-travel machine only need a little amount of energy to work and because this machine could use its own supply of matter as a source of energy, the total amount doesn't necessarily equate the amount of direct energy that you are putting into it.