Can a "lightsaber" be scientifically possible? Can a lightsaber be made in real life?
If yes, how can you make it?
If no, why is it impossible to make it?
I know there is another question on it, but I feel like I need better answers  :)
 A: I would say the lightsaber (or lightsabre if you prefer) is not such a far-out idea that we can rule it out completely based on fundamental principles of physics. So maybe there could be such a thing. It looks a bit like a very powerful laser beam that somehow is prevented from propagating very far. Or maybe it is some sort of cylindrical plasma.
The obvious difficulty with the laser beam concept is how to stop or reflect the beam after a metre or so. For a mirror you normally need some sort of solid object. I have not thought of a way to do it which would survive the kind of uses to which a light sabre is put.
For a plasma the problem is one of confinement. This seems to me a little more feasible---some sort of electromagnetic field confinement. I wonder whether there are any examples of something similar to this in astrophysics, but on a much larger scale? I mean a long filament of plasma in otherwise empty space, supported by fields and coming to an abrupt end. Maybe others will know.
A: 
why is it impossible to make it?

I don't think that question has an answer unless you can be more specific about what "it" actually is supposed to be. I think I've read somewhere that the canonical explanation, agreed upon by Star Wars fans, is that it's some sort of a plasma thingy, maybe confined by some kind of a force-field thingy. But, that leaves a lot unsaid.
If somebody wants to draw up detailed plans for a light saber, then maybe somebody else could be bothered to study them and explain why this bit won't do what you think it would do, why that bit can't be made, why this part seems too hand-wavy and needs to be filled in before we can go any further, etc. But, if all you have is the vague idea of "that thing from the movies," then I'd say that the reason it is impossible to make one is that nobody knows what to make.
A: There is the related issue of the force field, which is also a solid-like region. There are plasma windows, where a plasma held in a two-dimensional region can prevent the passage of matter through it. It can even hold a pressurized gas away from a vacuum. This relies upon the increased viscosity of plasma at high temperature. This makes the passage of matter through it less probable. This has only been done for windows at most $1000cm^2$ in area. It of course also requires a “frame” around the window to generate and contain this plasma by magnetism.
http://www.techbriefs.com/content/view/1834/32/
The light saber is a similar idea. There is a rod of plasma, which presumably due to its high temperature is viscous enough to act as a solid rod. How this is “capped off” is a bit unclear. How a magnetic confinement works is not clear unless there is some complex relationships with the plasma and the magnetic field. However, such systems are notoriously unstable.
A: A light beam that propagates a certain distance, then stops, is not possible.  However, as with most things, there is a way to achieve essentially the same effect by a different method.
The beam from a light saber only needs to burn material along a straight path from its end out to a fixed distance, say one meter.  Anything beyond that distance should not be affected.  So, if the light saber includes a range finder, which only turns the beam ON when there is something along that straight path nearer than one meter, and turns it OFF otherwise, it will work almost like the Star Wars light saber.  A big difference is that the beam will only be present when it's actively burning something; and another big difference is that the beams from two sabers will not interact with each other as if they were solid.
