First Question is Physic Related

Ahhh … now I remember why I mentioned the cat. I messed up my explanation in this post. So now to erase that from time …

Anyway, here is how it was supposed to go. Alice and Bob are in the present. Alice, puts Bob’s cat [Charlie] into a sealed box. Alice travels back in time and kill’s Bob’s cat while it is a kitten. Bob remains in the present and is staring at the box the entire time this takes place. So what is in the box?

Free-Will (end of the world): Alice is able to kill the cat. This has the side-effect that Bob never had a cat now. Did the experiment ever even take place? Was Bob destroyed as well because his present was destroyed through some aggregious violation of mass/energy conservation?

Free-Will (alternate reality): Alice is able to kill the cat. But she has killed a cat in another dimension of some kind. While she perceives that her "timeline" has a loop (from traveling backwards) she’s actually continuing in a linear time but in an alternate reality.

Fate: Alice cannot kill the cat. The experiment has always taken place. She has always traveled through time with the intent to kill the cat but for whatever reason she cannot. Upon returning to the present, the cat is in the box (and pissed).

Time travel doesn’t violate the energy matter conservation because matter is converted to energy. And the energy was sent back through time. [This is exactly why I don’t believe in time travel.]

I spent a long time thinking about this one, and I don’t yet have it all straight. So, bear with me.

The conservation of energy is inviolate. If you have a system where energy is not conserved, then you are either missing something or this case,deliberately not including something. Neutrinos (and most particles) were discovered in this way, as to explain beta decay Pauli had to theorize that there was an extra particle carrying away energy from the reaction. Additionally, in the case of friction, we deliberatly omit the microscopic interactions that make up a frictional force, so that we may more easily describe the macroscopic motion.

>Such that if an object were to travel through time, it’s energy/mass ceases to exist in time frame N and is added to the sum energy/mass of time frame N+10years or N-10years.
Just by appealing to conservation of energy, you can see quite clearly that this cannot happen. The two key problems are how do you keep the energy of the universe constant when your removing/inserting an object? You can’t, if the universe is a closed system. If the universe is not closed, though, we can do something about it. (I’ll leave proving that the universe is closed/not closed as an excercise to the reader.)

This is where the many-worlds theory comes in. If, as some theorists postulate, there are a multitude of universes, one for each possible outcome, then we may be able to use them to travel in time within our own universe. As it is the energy of the multiverse that is conserved, not the energies of the individual universes because they are no longer closed.

So, as you said, the scope of the universe would have to be questioned in order for time travel to be possible under these conditions.

Incidentally, special relativity is the only means of time travel that is currently "viable". But, it only provides for travelling into the future in less time than normal, not into the past. Future bound time travellers should consider the example found in wikipedia. In this example, a ship is travelling to a star 4.45 light years away at a speed 86.6% the speed of light. The round trip will require 10.28 years in Earth time. But, the ship only experiences 5.14 years. If the ship were going 96.8% the speed of light, it would only experience 2.57 years. 99.5% the speed of light -> 1.028 years. 99.995% the speed of light -> 0.1028 years, or ~1.2 months. If you are willing to expend the energy needed to acheive those speeds, than you can go to any date in the future you want without ageing much.