[quote=Michelle]

but Mickhail knew he had been hit by the electricty, i think if he had died and they had gone back in time and brought a new mickheil to the present would he necessarily know about the fence, would them telling him not just freak him out and liquify his brains in another way, [quote]

Well, Mikhail would know about the sonic fence and his death if the Others who went back in time told him about it. We don't know how long he's been on the island. He could have been telling the truth when he told Kate and Locke that he was the last surviving employee of the Dharma Initiative. He wouldn't freak out if the didn't go so far back in time that he didn't know he could die over and over again. If he does this sort of thing all the time and the Others routinely go back to find the Mikhail of say...only a day before he wouldn't freak out at all.

[QUOTE Michelle]
also witht eh harpoon through the chest, did they have time to know he was dead. the knew he had gone to that hatch, yet they did not know des was there aswell, and so they prob wouldnt realise he got harpooned,[quote]

Well they might not have found out about it for 20 years or even 100 years, but still they could go back in time and fix it so that at that moment it would seem instantaneous. Cool, yesno?