PS3 Clarification

I have heard people say that the PS3 cannot play ps2 games or ps1 games. But someelse has said that only the 60gb model could play ps2 and ps1 games but now the 40gb version cannot.

Whats what??? Can all PS3's play PS1 and PS2 games?? or only certain models??

60gig plays 100% of ps1 and ps2 games

80gig plays all ps1 games and 85%+ of ps2 games

40gig plays all ps1 game and ZERO ps2 games (as of right now, rumor of possible update to play ps2 games)

What?? why is this?? why can the 60gb ps3 play all the ps2 but the 40 cannot. It makes no sense.

Nintendo Wii managed to backplay smaller gamecube disks and normal sized disks, too me that seems more of a challenge to what playstation has done. Dosent the game you play depend on the lazer and programing, if true what has been changed in the 40gb from that of the 60

60gig plays 100% of ps1 and ps2 games

80gig plays all ps1 games and 85%+ of ps2 games

40gig plays all ps1 game and ZERO ps2 games (as of right now, rumor of possible update to play ps2 games)

winner-ps3