The thing that always bugs me about the "you change something and make and alternate timeline" is that you've effectively created an entire new universe.
If the Earth of this timeline is not the same as the original Earth from the original timeline, then nor is the sun it orbits the same sun, nor is it the same galaxy - yet this alternate Earth has a sun, neighbouring planets, comets etc. It's in a galaxy which is one of millions of billions in this amazing and expanding universe [/song]
In the instant you make a change, an alternative universe comes into existence as a parallel "timeline". Every single thing in this universe is identical to the one just "left" - right down to quantum level and vectors, spins etc - right up to the POD. From the POD, most this other universe keeps on going pretty much as the original (your change can't even affect Alpha Centauri for at least another four years (if at all), let alone anywhere else). From the POD, the change sends its ripples outwards, making this alternative Earth progressively more different from the original.
It's that "creating an entire new universe" aspect that I can't buy.
I can't recall the estimated mass present in our universe but we'll just call it a fuckton.
Which means that the energy required just to create the mass alone = fuckton*c^2 which is even more
How could you change an event, thus creating an entire alternate dimension with its own universe? There's a limit to how much energy you can get out of putting a bullet in someone's brainpan.
edited 4th Dec '11 2:46:15 PM by Wolf1066