Weird Computer Lines

Has anyone ever noticed, when a computer screen is filmed, it shows up with horozontal lines going accross the screen, sometimes moving? I always wondered what this was.
Also has anyone ever hooked up a camcorder to a tv, and then aimed the camcorder to the tv screen. you get a pretty freaky looking feedback effect.
It may be possible that these two subjects are related.

Its just the refresh rate of the monitor.

Same thing can happen at a local television station if they forget to run the on-air without patching through a frame sync.

I have stared at monitors for too long.. wish something interesting would happen with them, besides ruining my retinas.

I thouhgt it had something to do with radiatiion or something with the monitors. Thats what i think i was told a long time ago, although i may have heard wrong

have you ever been to a room that has mirrors on opposite walls? you get the same effect as with a camera. im not sure what the physics behind it might be but it looks like a feedback/loop caused by the same images being displayed to a mirror over and over again which accumulates until there's no more room to see any more.

CRTs usually operate from 60-85Hz. Meaning the image is being writte 60-85times per second. The framerate of the camera is usually half that, so you catch images between writes.

If your refresh rate is set low enough you can, at least I can, look off to the side of the monitor (only on CRTs), and you can see the refreshing.

As for the feedback effect... something similar and cool, depending on your mindset, is to look at your eye in the mirror. You can see a reflection of yourself, in yourself. Get close enough and you can see a reflection of yourself, in yourself, in yourself.

They're right. It's just a pecularity of the monitor. If you see pictures that would be an example of subliminal suggestion (which I don't believe in having tried tapes before)