文章将质量（mass）与重力作用（weight）区分开，并使用牛顿第二定律的线性形式 F = m·a 及旋转形式 τ = I·α。关键量是转动惯量 I，它依赖于总质量与质量分布。为说明这一点，文中给出同一根长度与质量固定的木棍示例：端点握持时比中心握持更难快速摆动，因为质量离旋转轴更远，I 更大。若 lightsaber 光刃有质量，它的旋转加速会受到真实阻碍，不会像无惯量光束那样轻易转动。
文中以《Return of the Jedi》中的 Luke 与 Darth Vader 决斗为判定场景，特别提到约 2:37 的片段：Vader 抛出 lightsaber 后，若光刃无质量，应绕灯柄中心旋转；若有质量，质心会上移到更靠近刀刃位置并改变自转轨迹。影片呈现的旋转行为更接近后者，因此光刃应有质量，至少不是纯光。结论是：银幕上的 lightsaber 更符合“由内部机制生成的可观测质点结构”（可能为 plasma），而非单纯 laser。
In a May 4, 2026 Wired article by Rhett Allain, the long-standing debate over whether lightsabers have mass is treated as a testable physical question: if the blade were a normal laser, it would be invisible from the side, effectively unbounded in length, and capable of passing through other blades, all of which contradict the way they move on screen, so the inquiry is narrowed to dynamics—whether the blade behaves as massless electromagnetic radiation or as a mass-bearing object.
The analysis separates mass from weight and applies Newton’s second law in linear form, F = m·a, and rotational form, τ = I·α. The decisive quantity is moment of inertia I, which depends on both total mass and where that mass sits. Using a simple bar example with fixed length and mass, rotation is harder when held at one end than at the center because more mass is farther from the pivot and inertia is larger. If a lightsaber blade has mass, it should resist angular acceleration like any physical object rather than move like a massless beam.
The decisive evidence is a scene test in Return of the Jedi, during Luke’s duel with Darth Vader around 2:37: when Vader throws the lightsaber, a massless blade should rotate about the hilt’s center, while a heavy blade would shift the center of mass upward into the blade and alter spin behavior. The observed motion better matches the latter, implying the blade has mass and is not pure light. The article concludes that cinematic lightsabers are consistent with an internal mechanism—possibly plasma-based—driving a physical blade structure.