Why do people says it violates conservation of momentum?
If you input some energy, and get more, it doesn't mean you broke the laws of physics, it just mean you got more energy, somehow. Could well be that something somewhere else is providing its energy into the experiment. It might look like energy came out of nowhere, but for all we know it just comes from somewhere we didn't know existed, or something outside the experiment.
If it is possible to have two particles that are far away from one another behave as if they were next to each other, then it's possible that in a controlled experiment, you would only see the increased energy without seeing the decrease wherever else it's happening, somewhere. In a computer program, you could easily represent this by coding it so that two physical objects interact with one another as if they were as close to one another as possible, in the physics' calculation, even if in the rendering code you render both in much different positions. The idea that in our universe, our perception of space negates the ability of particles to interact with one another beyond their relative distance, is pretty limited I think, especially with things like entanglement.
I think it should be noted thst conservation of momentum and conservation of energy are two completely different topics. While this device does not violate the conservation of energy it does violate the conservation of momentum.
To see why, let's first look at the conservation of energy. Simply put, it states that
Energy in = Energy out. If you were to add up all the different forms of energy, say potential energy, kinetic enrgy, and thermal energy, they would have to equal out on both sides of the equation, hence the equal sign. This device does this without problem. The energy is simply stored in a battery, or pulled from a power source elsewhere.
The problem comes in when you start talking about the conservation of momentum. There are many ways to express this property; classically it is
(mass x velocity) in = (mass x velocity) out. Thinking about the equation, it is obvious where the problem comes from. The mass of the object is not decreasing, as it would be in conventional rockets, but the velocity is increasing! This is a problem, that gets worse when you consider Newtons second law of motion.
Often stated as
Force = mass * acceleration, it is actually better stated as
Force = change in momentum/change in time. Obviously this can't happen if the momentum doesn't change. Remember, I said the initial momentum has to equal the final momentum. If so, how does momentum change ever? The trick to this is to consider momentum locally. Globally, momentum cannot change, locally, it can by expending mass. Rockets move by ejecting mass out behind them.
This leads to an inescapable conclusion; an object with no external forces applied, and no change in mass can never accelerate. It doesn't matter how much you bounce radio signals around the cavity, the internal forces will always cancel; in fact the have to.
I hope that helped with regards to why scientists by in large are super skeptical of this machine right now. One scientific paper isn't going to change that. Shit, multiple scientific papers would only start to change opinnions. Right now, this device needs far more experimental evidence, to begin to assess whether the device truly works or not.