I'm confused what this means. Are patterns of light and shadow not also light, and bound by the speed of light (on the upper end)? How can patterns consisting of light (or the absence of it) move faster than light?
In other words, speed of a projection of light from 3d space to 2d space may be higher than the original speed in 3d. (Because one dimension gets squished to 0, so movement in this dimension is perceived to be instant.)
It's like a diagonal of a cube 1x1x1 has length sqrt(3), but if you apply orthogonal projection onto R^2, its image will be a diagonal of a square and it will have length sqrt(2). Shorter distance -> shorter time to travel.
> It's like a diagonal of a cube 1x1x1 has length sqrt(3), but if you apply orthogonal projection onto R^2, its image will be a diagonal of a square and it will have length sqrt(2). Shorter distance -> shorter time to travel.
This example doesn't make sense to me. In that analogy, wouldn't anything on that diagonal appear to move more slowly in 2D than the same thing moving along the diagonal of a face? The cube diagonal would make it move farther than it does in 2D space.
I remember seeing a simulator in my optics class that combined multiple wavelengths of light. The interference pattern moved faster than the speed of light, but that was fine because information wasn't moving faster. That was just the result of adding them together.
But when you move the laser emitter in your hand you're controlling the speed in that 2d space, not in 3d. You don't ever affect the position of photons in the Z dimension. So you’re not constrained by speed in 3d which would later be slowed down after being projected. So you move your laser emitter along the diagonal of a face with velocity v. And the perceived light which would get projected onto a plane needs to match the position of the emitter on the face. Which creates the illusion that light travelled along the 3d longer diagonal faster than at v (in order to match the projection which describes how you/camera sensor see the light). But in reality the light never travelled along this longer diagonal. It’s only an illusion. And it is this illusion that we’re measuring the speed of. Photons on this diagonal arrived straight from the emitter, i.e. each of them appeared in only one point of the diagonal throughout its entire history. In other words, the photon at the beginning of the perceived movement is a different photon than at the end. They travelled along different paths. And when some photons were at the diagonal, some others were on their way there.
Shine a laser into space and the image of your laser can be much faster than the speed of light. Nothing actually moved faster than the speed of light though.
Stand a meter away from a wall and wave a laser pointer such that the spot travels back and forth between two points a meter apart in one second. Move two meters away, but keep your movement exactly the same; the spot now moves two meters in one second.
Move two light-seconds away and do the same movement. The spot now moves two light-seconds in one second: twice the speed of light. Of course it takes two seconds from when you turn the laser on to when an observer at the wall would see it, and four seconds before you see the spot on the wall, but the spot itself moves faster than light.
Ah, so for the sake of capturing conceptual / perceived "objects", the global shutter, at least, can do a better job at what would be perceived during a short period of time that the shutter opens and captures each pixel.
A rolling shutter might capture points along the way but leave gaps in comparison. In the laser pointer example, you'd probably want a longer exposure, but the global shutter would still give you uniform capture better matching what your eyes / brain perceived.
