system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] If time travel just makes an alternate timeline, does that means there's thousands of alternate timelines left over from the Temporal Cold War? Are there any ramifications from the abuse of time like this?
gpt
Only *some* forms of time travel make alternate timelines. Many instances of time travel have changed what the Department of Temporal Investigations would call the "prime" timeline. Here are some examples:

* On stardate 5373.4, Captain Kirk and Commander Spock of the Enterprise were visiting the historians investigating the Guardian of Forever. Kirk and Spock went through the Guardian to observe the dawn of the Orion civilisation. Although nothing *seems* to have occurred, Kirk's and Spock's logs indicate that when they returned to the present, they found that Spock no longer existed. They report an Andorian was First Officer of the Enterprise. After determining that the cause of the timeline change was Spock's absence from certain events in his own youth on Vulcan, Spock travelled back to be present at those events, which ended up restoring his presence in our timeline. If their logs are to be trusted, both their instances of time travel changed our prime timeline.

* On stardate 50893.5, the crew of the Enterprise-E joined the battle against the Borg in Sector 001. A small sphere was observed leaving the Borg cube during the battle, heading towards Earth. The Enterprise's sensor records show that, after the Borg sphere entered a temporal vortex, the Earth changed: it showed the presence of 7 billion borg. This demonstrates that the Borg's travel into the past changed our prime timeline.

* On stardate 48481.2, Commander Sisko and some of his staff were lost in a transporter accident. Chief O'Brien determined that Sisko and the others were transported back in time due to the presence of chroniton particles. Sensor records from the Defiant show that all Starfleet installations and communications disappeared from the present. This shows that Sisko's presence in the past changed our prime timeline.

Most instances of time travel do not make alternate timelines. Only one known instance of time travel appears to have created an alternate timeline, and this involved the use of red matter. Therefore, it is reasonable to conclude that the temporal incursions of the Temporal Cold War did not create thousands of alternate timelines. 

However, it is known that there are many different quantum realities out there. On stardate 47391.2, Lieutenant Commander Worf of the Enterprise-D reports having transferred between different quantum realities after encountering a quantum fissure. Rather than being caused by time travel, these quantum realities are formed through the different choices and outcomes of various events: when a coin is tossed, two different quantum realities result, one where it comes up heads and one where it comes up tails. The existence of all these quantum realities, without any negative effects on any individual reality, can lead us to conclude that the universe is quite capable of handling multiple timelines. Therefore, even if the Temporal Cold War had created multiple timelines (and we believe it did not), this would not be a problem for the people living in those various timelines - we already exist in multiple realities anyway.