system
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human
[Star Wars] How and why do both the Jedi *and* the Sith know of and use lightsabers?

Both groups originated in different parts of the galaxy right? Or did one side see the other's tool and decide that they were gonna get in on some of that laser sword action?
gpt
Lightsabers have actually gone through various stages throughout history. The original ancestor of the Lightsaber is a weapon called the Forcesaber that was created and used by the Rakatan Empire. The Rakatan wielder would power the saber by channeling Dark Side energy through a focusing crystal embedded in the hilt.

Around the same time as the Rakata, the precursor to the Jedi, the Je'Daii Order, created their on version of this idea by using a complex ritual to "freeze" the plasma of the blade in place. The first of these new sabers was called, cleverly, the First Saber. These were the most basic forms of the lightsabers we know today. They were used for ceremonial purposes only, as there were still many issues with them and they were unreliable in battle. The Je'Daii did use bladed weapons like swords regularly, though.

The Je'Daii were later corrupted by the Dark Side when the Rakata invaded. The Je'Daii originally pushed them back, but then they found several of the Rakatan Forcesabers and used those against the aggressors. The Je'Daii were eventually torn apart, but their teachings gave way to the more modern Jedi Order.

These types of sabers were the norm until around 15,000 BBY, when Jedi managed to create the first true lightsaber, where the energy loops back at the end of a containment field and returns to the hilt. These models were *awful*, as they required a belt-mounted power cell to be attached to the saber hilt and it drained a ton of power. The tether restricted movement of the user horribly, but over time refinements were made and the sabers were made generally stable and mobile enough to use in regular combat, not just as a siege-type weapon.

Interestingly enough, it's the Sith we have to thank for the advancement of the lightsaber to what we have now. The original Sith Empire formed when a group of Jedi were kicked out of the order and found themselves on Korriban. They interbred with the Sith species that was present there and took their name. They also learned much of the Dark Side from them, and over the centuries became the powerful empire they were at their peak. It's because of this origin that lightsaber use among Sith is the standard.

The Sith found a way to embed a power cell in the hilt along with the focusing crystal. They also added a superconductor that fed the energy looping back from the blade back into the power cell. This made for an extremely efficient system that only actually lost energy when the lightsaber was cutting something, as the loop was broken while it was. This eliminated the tether to a belt-mounted power cell and allowed the Sith to be much more mobile and powerful with their sabers, as stability was no longer an issue.

The Jedi soon found discovered how the Sith had managed to improve their sabers, and quickly made it work with their own sabers. This led to a huge escalation in the ability for lightsaber combat on both sides, and refinements were made to the designs throughout the years. And this is how we have come to the powerful lightsabers that we all know and fear today.

Bonus fact: The Sith didn't always use red lightsabers. The color of their lightsabers is due to the artificial crystal that they tend to use (Jedi only use natural crystals), though there are a few that forgo the artificial crystal out of preference or ignorance. The tradition died out for a bit during the Great Hyperspace War, when fallen Jedi flocking to Naga Sadow's side opted to use their own lightsabers. The tradition was reinstated by Darth Revan nearly 2,000 years later.