You know how sometimes you make a choice, and you can't help but wonder 'what if?' What if you'd taken that other road, said yes instead of no, or even just tripped over that one loose paving stone? Well, in the grander scheme of things, that 'what if' can actually create a whole new reality. That's essentially what an alternate timeline is.
Think of it like a river. The 'true' or 'natural' timeline is the main course, flowing steadily along. But then, something happens – a time traveler nudges a pebble, a cosmic anomaly causes a ripple – and suddenly, a new stream branches off. This new stream is the alternate timeline. It's not just a parallel universe sitting neatly beside the original; the reference material suggests it's more like the new stream diverges from the old, and in some cases, can even overwrite it. It's described as an 'interstitial spillage of time,' which sounds rather dramatic, doesn't it?
How do these divergences happen? Well, it seems to require a significant push. We're talking about beings with immense power, like Sutekh or Rassilon, or even the Doctor or the Master, who have the knowledge and the inclination to mess with the fabric of time. They can adjust the 'timeflow' and overcome something called 'temporal inertia.' It's not something a single planet could manage; it takes a cosmic-level effort. And when this happens, it doesn't just affect the new timeline; it can cause chaos throughout the entire universe, potentially even releasing enough energy to destroy the new timeline and snap history back to its intended course. Imagine the energy released when two TARDISes collide – that kind of power could do it.
What's fascinating is that even when a timeline is erased, memories of it can linger. Sometimes it's a subconscious echo, surfacing in dreams. Other times, like with Ruby Sunday, it's a more profound, instinctive memory, allowing her to recall events that even the Doctor couldn't remember after a timeline shift. It’s as if a part of her experienced that erased reality, leaving an indelible mark.
These alternate realities aren't always about grand, universe-altering events. From a more philosophical standpoint, some theories suggest that alternate timelines are constantly winking in and out of existence with every single decision we make. Every choice, every fork in the road, could theoretically spawn a new reality that quickly fades if not sustained. It's a bit mind-boggling to think that the universe might be a constant flux of potential realities, with time travelers acting as particularly potent catalysts for these divergences.
It's important to distinguish these from parallel universes. While the terms are sometimes used interchangeably, alternate timelines usually stem from a single point of divergence, whereas parallel universes might have multiple differences from our own. It's a subtle but important distinction when we're talking about the intricate dance of causality and reality.
