is it possible for a 6 week old to sleep through the night?

It is...BUT not all babies do.

possible... sure, anything is possible
probable... no

Mine did but from what I understand most dont.

It's possible, but not the norm. Some babies are great sleepers and some are not!

my second son slept through the night since birth....it was scary to me because my first son was up every two hours so i was up checking on him when i could of been sleeping....my baby would sleep from 8:30 to 5 am....he is now 1 and still sleeps through the night and takes two naps during the day for 2-3 hours my first son who is 4 maybe takes one nap and he still wakes up 1-2 times at night.....

Mine did :) He started at exactly 6 weeks :)

Sure. My 3rd child was sleeping 8-9 hours a night at 5 weeks old.

It is possible. But certainly not the norm. They will do it if they are ready. You can't (and shouldn't try to) make it happen.

Possible and highly unlikely