I was eating a carrot and looked up at my alarm clock and noticed that the numbers seemed to float around in the display. It was really weird. I’ve noticed this on occasion also with a computer screen. Anyone know why the little LED numbers seem to float like that?
Your alarm clock is probably a liquid crystal display, not LED, which is a light-emitting diode. They seem to move because your head is moving up and down. What is probably happening is that the numbers are appearing stationary, as your frame of reference, the clock face, moves up and down in your vision.
Part of it has to do with the fact that LED clocks very often don’t just light the LED, they flash it on and off at a very high rate of speed. The reason for this is that you can make an LED appear to be brighter to your brain without driving more overall current through it (your vision system somehow acts more like a peak detector than a signal averager).
Computer screens are also not a constant display. An electron beam lights up part of the screen starting at the top left corner, then going across the screen, then down row by row. As long as it happens fast enough, your brain blends the whole thing into what you think is a solid image.
I don’t know exactly why chewing mucks with your vision system, but it does, and it’s most noticable in things that flicker, like LEDs, computer screens, and such.
you 2 have it if you just put it together - your head is moving and you are looking at a flashing ‘target’. When you look at the LED it flashes on and off but even after it’s off you still ‘see’ the image. While you chew your head moves and you see the clock in a diffrent spot but the numbers stay right where they are - so they seem to float.
I have a feeling that it might be also that the action of chewing sends tiny shock waves through the eyeballs, minutely distorting the retina and lens in so doing.
Or…it’s all part of the Trilateral Commission/Bilderburger Global conspiracy!!!
What? Why are you staring…
You’re one of Them aren’t you? :eek:
For fun, try reading your computer screen as you brush your teeth with an electric toothbrush. Very trippy!
At a computer show I was once shown to test the quality of monitors by chattering my teeth as I looked at them. Those with very high scan rate would still have good image but with the lower quality ones the image would jitter.
If the LED’s in the clock radio were run on DC, you would not notice this at all.
They are blinking quickly. Most likely at 120hz (double the 60 you get from the wall in the US, if you live somewhere else double your AC frequency).
You eyes and attendant neural hookup have a limited time resolution. Anything that blinks faster than 20 or 30 times a second looks steady.
When you chew, the vibration is making each blink show up at a slightly different position on your retina and you can see that.
You can get the same affect by moving your eyes to look back and forth between spaces a couple feet on each side of the clock. You will see a blinky pattern left across your vision if you do it right.
The make displays that are just a pattern of vertical LED’s that you can only see what is being displayed by looking back and forth across them quickly.
The replies relating to blinking LEDs are on the right track, but in clocks the LEDs blink neither to appear brighter on less electricity nor due to the rectification of 60 Hz alternating curent.
LED displays driven by microprocessors, including those in clocks, are flashed on and off to save wiring and power control transistors and take advantage of the appearance of being continually on that our eyes perceive.
Typically, each digit in the display is driven by one wire (say the negative wire is driven for the tens of minutes digit)while all the similar segments are driven by the other (say the positive wire is driven for all the upper left hand verticle segments). This way, to drive four digits with seven segments each only requires controlling eleven wires. Actually, they wouldn’t look like wires, but would probably be circuit board traces. But you get the idea.
If you swing the clock around in the dark and stare straight ahead past it, you can see this strobing action at work.
Cecil touches on this at the bottom of this column:
I’ve noticed that after you sneeze, computer screens “wobble” for a few seconds - I assume this is somehow related? The “vibration in the eyes” theory posited above could explain it, I guess; but your head is not moving anymore after the sneeze stops, and that’s when the wobble happens.
I bet the wobbling television is caused by this sort of interaction with the motion of sneezing. You can see something startling like this if you clamp a plastic utensil between your teeth and pluck it, for example.
Whether your eyes and head are still moving a moment after sneezing may be harder to figure out than you think. Eyes have all sorts of amazing motions. For example after rapidly reorienting your head they may twitch with nystagmus (if you watch someone’s eyes when they are dizzy you may see this, or if not come and watch my crosseyed Siamese cat). Eyes even rotate about the axis of vision (ie of course they can go up/down, and swing left/right, but they can also twist like a screwdriver, albeit not very far). If you don’t believe me, watch your own in the mirror as you slowly lean your head left and right. Creepy…