Escalators in public places should be lit by slow-flashing strobe lights (the proportion of the population in whom this will trigger epileptic fits is very small). The flashes could be timed so that the escalator has moved exactly one step position between each flash of the strobe, giving the impression of a stationary escalator with people jerkily moving up a step at a time. If you then increase the strobe frequency very slightly, the escalator will appear to move backwards while the people jump forward a step at a time.-- hippo, Nov 08 2010 Background information http://www.epilepsy...tosensitiveepilepsyThere's a suggestion that just looking at a moving escalator is enough to trigger photo-sensitive epilepsy so I'm unsure whether adding a strobe (which makes the escalator appear stationary, but is itself a bright flashing light) will increase or decrease the risk of an epileptic attack. [hippo, Nov 08 2010] I think that an escalator is actually too slow to strobe properly, and the periods of "dark" time between the flashes would therefore be quite long. Too long in fact to create the impression of a continuous motion "held" in a static position.-- xenzag, Nov 08 2010 So speed up the escalator.-- pocmloc, Nov 08 2010 And use a more powerful flash tube so the image stays on your retina longer.-- lurch, Nov 08 2010 I have explained why it won't work. A more powerful light will make no difference. The whole principal of a strobe lies in the ratio of dark spaces between momentary flashes of light.
(again) - The dark spaces would be too long to create the sense of a static motion. It's therefore bad science, but I'm not a scientist (unlike others on this site who might like to comment/correct what I'm saying)-- xenzag, Nov 08 2010 I'm pretty sure most shopping malls already do this. That's what that epileptic scraper at the end of an escalator is for.-- doctorremulac3, Nov 08 2010 The flicker-fusion rate actually *rises* with increasing brightness, so you would need a *less* powerful light.
I think I can conceive of a version of this thing that would work.
First, instead of an escalator, a moving sidewalk ("travelator"), such as is found in many airports. Next, paint transverse stripes on the standing surface: choose a spacing such that, given the speed of movement, and some suitable strobe frequency, the surface appears to stand still. You'll see people moving forward on an apparently stationary surface. Detune the strobe a bit and the travelator appears to go backwards while the passengers move forwards, or to go forwards at a different speed from the passengers.
(One necessary detail is that the railings be transparent, which, for esthetic reasons, they already are in some airports.)-- mouseposture, Nov 09 2010 This reminds me of the "Blink" episode of Dr Who. In this episode, creepy statues try to kill people, but only move when no-one is looking at them. In one scene, a flickering light causes a stroboscopic effect, and you see the statues incrementally move towards the trapped prey.-- xaviergisz, Nov 09 2010 [mouseposture] - the "flicker-fusion" thing is about trying to take discrete, disjoint images and combining them into a perceived continuous seamless image.
However, the escalator *is* moving in a continuous, seamless fashion; and the idea is to attempt to make it appear to be discrete jumps.-- lurch, Nov 09 2010 Yeah, I'm having second thoughts about the relevance of flicker-fusion. And I'm starting to think it *might* work if the aim were an illusion of *discontinuous* motion of passengers and *stationary* steps -- I suspect it would be one of those illusions which can be seen in either of two ways. Would the visual system assume independent motion of passengers and steps, or would it assume a rigid connection between each passenger and the step they were standing on? Not sure about the escalator-moving-backwards idea, though.-- mouseposture, Nov 09 2010 Put the passengers in stagecoaches, so the wheels do that weird backwards thing they do in Westerns.-- infidel, Nov 11 2010 random, halfbakery