ooh, oooh, something i know about!! Yes, the lightsabre would slice straight through excalibur, straight through the person holding excalibur, and straight through you if you're not careful. The blade has no weight and is extremely easy to hurt yourself with (and when talking lightsaber, hurt is a bad thing). The blade can cut through anything, given enough time. It still meets resistence as it passes through materiels. That is why it occasionally bounces off things. And that is also why you would want to hold it in two hands.... It's much more precise.
In episode 5, when vader blocks the blaster bolts, he doesn't use his hand. The hand is more like a motion that helps him summon the force, much like the "Pushes" in episode 1 that throw the droids back. He "casts" what is known as a force sheild, which absorbs the energy of the blaster bolts. It works on pretty big weapons, depending on who's using it. Vader could probably use it to stop an e-web. (kind of like a 20mm cannon). I don't know about lukes lightsabre bouncing off him, i don't remember that bit. Still, remember how easily it took his arm off.
Although vader (then anakin skywalker) had the highest metachlorian count they had ever seen, remember, luke is not born yet, and won't be for a long time. Luke has FAR more natural force ability than vader (hence, far more metachlorians). You can read about this in the books, or just watch the films again. Luke defeats Vader after only being a Jedi for 5-10 years. Vader has been training since he was 10 (and i think he's about 80 in ROTJ, the force prolongs life). Vader is the one who wiped out almost all the jedi, including the jedi council (goodbye Samuel L. Jackson). Then he is beaten by someone who has only just attained the rank of Jedi Knight? By the time Luke is a Jedi master, he is infinetly more powerful than vader ever was or ever could have been. BTW, to anyone who is interested, Vader had a far higher ability with the force than the emporer, don't ask me why he was serving under him. Maybe some of the slave mentality remained and let the emporer rule over him as a slave master would.
The "Batteries" On a lightsaber are good for somewhere around 120 years, i think you'd have time to nip down to the local store and get some more. It uses a small power cell, not difficult to get (in Star wars world). The Lightsabre somehow reflects power back into itself, thereby contunually recharging the battery (a bit like a car really) But again, the more you slice and dice, the quicker it runs out. I *think* that is what was happening to Obi-wan-Kenobi's in Star wars.
Well, that's about it for me.
James
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All knives are created equal, then i get my dirty big hands on them and the real fun begins.