How do the discs spin in the drives?

[kibescorp]

I was thinking about this the other day. When I place a blu-ray disc into my PS3, about halfway through it "sucks/draws" it in automatically (like when you put a CD into the disc changer in your car). What exactly is the "force" that pulls it in? Is it some sort of mechanical tool, and can it damage your discs?

Also, I have always been confused as to exactly HOW discs spin inside the drives. I know some drives, you "lock" the disc in (the small, round thing in the middle that locks the disc in also spins it). However, in others, a tray ejects and you place the disc onto the tray. Well, the disc goes in, and you cannot see what happens to it from that point on ...

How do discs spin in those kinds of drives? And how are they "locked in?" I mean, don't they have to be "locked" in order to spin without wobbling? But if you simply place it onto a tray, how can the drive "lock" the disc in and spin it automatically? I just wish I could see it happening inside the drive for myself ...

I'm always afraid my blu-ray discs will get damaged somehow (not scratches, but CRACKS) inside the PS3, because I always leave them inside the console after I finish playing (I usually spend 2-3 weeks on a game, so it would not be practical to eject the game every day), and once you "send" the disc into the PS3, there's no telling what is happening to it on the inside.

Thanks!

[MilesAhead]

Don't know about the other questions but I found playing CDs in my car that the spongy material above and below the slot can trap grit. Even when not going over bumps I found my CDs could be scratched by playing in the car. The only possible cause was dust or grit in that spongy stuff. My automobile CD player could play .wma files. I only used .wma data discs in the car. Never original audio discs.

I don't know what grabbed the CD to pull it into the slot in my car's CD player. But I know it didn't work well on slick shiny CD blanks. I had to use either the white latex coated ones or the metallic brushed surface type. Often the slick surface blanks would play but they wouldn't eject. Had to pry 'em out manually.