The first part in dissecting a Lightsaber is to establish what exactly the burning-cut-off-your-hands part is (IE the blade).
There are several different possibilities you could look at with this. It could be either a laser, beam of plasma, stream of electrons or protons, or some sort of energy beam which only works above a specific energy level.
Laser:
A laser is a beam of light in which all the photons are going in the same direction at the same frequency. It doesn't tend to disperse over distance and it is very good for cutting things. The problems with a laser are many. A laser can not be blocked by another laser. It also
can
not be seen unless it is the light
reflecting off of something else.
Finally, the only way to make a laser shine out to a particular
distance and simply stop would be to put a mirror out there.
Which would not be a Lightsaber so much as it would be a laser
chainsaw, or Beam Katana.
Plasma:
Plasma is very hot. It can also be seen fairly well. It can also be directed using electro-magnets. The problem with using plasma is that it tends to dissipate very easily and diffuse even more quickly. This would render the Lightsaber into more of a stick with an extremely hot ball of plasma on the end. The fact that plasma can be radioactive would also be a deterrent for the users of Lightsabers.
A Stream of Electrons or Protons:
This is actually a fairly probable idea. A beam of electrons can be directed by magnetic or electric forces, it would glow since it ionizes air, and it has the ability to cut objects. For those of you who either know physics or like to pretend you know physics I have worked out some simple calculations and written some long scientific sounding words. For everyone else: trust me, it wouldn't work.
A Beam of Energy:
This seems to be the most likely scenario. It could ionize the air it touches, which would allow it to cut through objects and to glow. The only problem is that it would have to be a very specific type of energy. Since it would have to be able to travel through several crystals (like light). So if it were a beam with characteristics similar to light, this would be possible but sadly enough we do not know of any beams like this (to my knowledge.
A laser is a beam of light in which all the photons are going in the same direction at the same frequency. It doesn't tend to disperse over distance and it is very good for cutting things. The problems with a laser are many. A laser can not be blocked by another laser. It also
can
not be seen unless it is the light
reflecting off of something else.
Finally, the only way to make a laser shine out to a particular
distance and simply stop would be to put a mirror out there.
Which would not be a Lightsaber so much as it would be a laser
chainsaw, or Beam Katana.Plasma:
Plasma is very hot. It can also be seen fairly well. It can also be directed using electro-magnets. The problem with using plasma is that it tends to dissipate very easily and diffuse even more quickly. This would render the Lightsaber into more of a stick with an extremely hot ball of plasma on the end. The fact that plasma can be radioactive would also be a deterrent for the users of Lightsabers.
A Stream of Electrons or Protons:
This is actually a fairly probable idea. A beam of electrons can be directed by magnetic or electric forces, it would glow since it ionizes air, and it has the ability to cut objects. For those of you who either know physics or like to pretend you know physics I have worked out some simple calculations and written some long scientific sounding words. For everyone else: trust me, it wouldn't work.
A Beam of Energy:
This seems to be the most likely scenario. It could ionize the air it touches, which would allow it to cut through objects and to glow. The only problem is that it would have to be a very specific type of energy. Since it would have to be able to travel through several crystals (like light). So if it were a beam with characteristics similar to light, this would be possible but sadly enough we do not know of any beams like this (to my knowledge.