• Lovable Sidekick@lemmy.world
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    4 days ago

    Very eloquent explanation. The one glitch I must point out is that the shadow (or absence of light) can’t move faster than light, because the shadow is information and information can’t travel faster than light. If it could, you could use a sequence of shadows, coded by length and spacing, for FTL communication.

    • dondelelcaro@lemmy.world
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      4 days ago

      The shadow moving is more akin to bandwidth of transmission rather than speed of transmission. You still have to wait for the photons (so speed of light) for the information to arrive, even if the “speed” of the shadow appears FTL.

      • Lovable Sidekick@lemmy.world
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        3 days ago

        Ok I watched the video and I get that no information is travelling FTL. “Speed of darkness” is misleading tho, because the light at the shadow’s edge has the same “speed” as the shadow.

        • ryannathans@aussie.zone
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          3 days ago

          The edge of the shadow can move across the surface of an object an essentially infinite speed. That’s the speed of dark

          • Lovable Sidekick@lemmy.world
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            2 days ago

            Yeah I get it. Do you get that the light around the shadow, that isn’t part of the shadow, is moving at the same “speed” - so it’s not the speed of “dark”. It could be dark, it could be red light, blue light, full white, any color or lack of color.

          • Robust Mirror@aussie.zone
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            2 days ago

            And the edge of a ball of light created by a powerful spotlight could do exactly the same thing. That video is nothing but sleight of hand style tricks dressed up as the speed of dark. You can recreate every scenario using light to argue light is faster than the speed of light. What you’re doing isn’t movement at all, period.

            Imagine earth has a ring around it the distance of the moon. You have a powerful laser pointer and rotate 360 degrees while pointing at it. The dot of light “travels” around it at insane speeds. This is what the video argues “dark” or the shadow is doing. But if you think about it for a moment you realise each “dot”, whether it’s the shadow or the laser pointer, is actually a unique thing, and nothing is actually “moving” at all. Shadows don’t move. Ever. They aren’t even something. They are just light being blocked.