When Eli stuck his hand in the gate

[garhkal]

Agreed. he just left his hand in it.

[Major Tyler]

When jack did it on sg-1 he went through the gate and probably just left his hand in the wormhole when he came through.

This is the "best" answer that is most consistent with the "science" of the Stargate that we've seen come after that. They establish in later episodes that when they want to keep the gate open, they just transmit a constant radio signal (Lost City, Pt. 1) called a "hold signal" to do it. There was no reason for Jack to keep his hand in the event horizon.

I suspect this is one of the few things that TPTB wish they never did because it doesn't really match how they later "decided" to make the gate work.

[geewillie86]

Since these gates are prototypes with limited ranges (according to TPTB in This interview: http://www.moviehole.net/200920241-m...-universe-cast), it might very well be that their wormholes can't last as long as the MW and PEG gates.

[Tuvok]

Actually I assumed that the shacking and rattling going on during the end of the countdown. Was the ship trying to leave and the safety procedure keeping it in place. So maybe it isn't something they can do all the time. Cause one day the Ships auto-pilot might win out.