Maybe Henry remembered the scientists dying but chose to act out the mystery of it like it was happening for the first time for him, so as to avoid causing any big ripples?

We don't know how long it took Henry to figure out how to change the past right?

When Jack goes back in time to stop Henry he's not stopping Henry from the 2010 timeline but from a different time line where Kim died.

Correct?

Holy crap, is that right? I think it is!

The Henry that got to live a life with Kim for four years didn't send his mind back, he ceased to exist. The Henry we have now technically only went so many weeks/months into the future sans Kim before he could send himself back to fix things.

Quick, tell the writers!

Sucks for Henry even moreso now.

I'm thinking Henry has lived through 3 timelines of these events.

Timeline A - Kim dies in the explosion and at some point Henry starts to try and change the past. In this timeline the scientists and Stark may have died but Henry didn't care because he was so wrapped up in his grief/plans. At some point he figures out how to change the past and does so retaining his memories of this time line. But we don't know how long it took him (I don't think Henry ever says how long it took him to figure out how to change the past), it could have been 6 months or it could have been 6 years, but maybe not that long. Maybe it took him 3 years. So he starts

Timeline B with his memories from Timeline A but Kim doesn't die (it makes sense that if both Jack and Henry can remember the changes then Henry can remember the changes as well) Because Kim doesn't die neither do the scientists. Timeline B lasts for 4 years until things start to go wonky and Jack has to stop TimelineA!Henry from preventing the accident which leads to

Timeline C, the current timeline. Where Henry and Jack both remembered everything that happened, but with Henry also remembering Timeline A and Jack not understanding this. Until Henry erased Jack's memories. And now he's starting over to try and save Kim with his memories from his first attempt.

Jack is thinking of Timeline B as the "original" one, but it Timeline A could be the original timeline and in that the scientists exploded but Henry didn't care or Jack never figured out what caused it because he didn't have Timeline C!Jacks' memories.

Except the current Henry does seem to have lived those four years. Hm. I'm trying to find a way for both those things to be true.

Okay. 2006-Henry lived for a while without Kim, then went back in time to the critical moment, stopped the experiment and lived four years of bliss, with the memories of the "erased" timeline. Bad things start to happen; Jack's going back to stop him. Henry must know that if Jack succeeds, 2010-Henry with the memories of bliss will cease to exist, and the only Henry will be the one who only knows he failed, and knows nothing of the four years. This is unacceptable. He wants to remember, and to try again, hopefully without screwing up the fabric yadayada this time around. His only choice then is - to go back in time again, to the critical moment, arriving before HIMSELF. This moment has Jack in it, so it's already a different moment than the one he went back to before. So he arrives before he arrived last time, thus wiping out the first timeline in which he went back, tries again to stop the experiment (because what's he gonna do, stand there? and Jack would have been suspicious), and fails. But he has his memories of both previous timelines, he knows what's worked and what hasn't, so he can try again. And he knows Jack isn't savvy enough to realize immediately (who did?) that the Henry he stopped and is now living with shouldn't be remembering the same timeline he does. And now he's wiped Jack's memory, so now there's no chance he'll figure it out later.

This requires something to be true of Henry that wasn't mentioned in the show, but it's the only way I can think of to make it work out. And I've been typing this for an hour so someone else has probably already said something even better.

Time travel makes my head hurt.

"Time travel. That takes me back. Or is it forward?"

Pardon me as I butcher an old Who quote. There are some lovely ones from 2005 Who s3 too. "timey-wimey" (not plot-spoilery) comes immediately to mind, from Blink.

At first I thought askeye was right about how things are supposed to be, but Zenkitty makes a good point. For some reason, Henry seems to remember more of Timeline B than he should.

Henry should definitely remember Timeline A. Henry should remember the attempt at Timeline B. However, after Carter interferes, he should only remember up until the point that Carter stops him from saving Kim, generating Timeline C.

On the other hand, Henry knows that he was successful in saving Kim, but the universe began to unravel, requiring Carter to go back in time to stop Henry from saving Kim. And considering that supposedly they're best friends, maybe they've talked about what happened in the other timeline... a month did elapse. (Maybe this is the explanation?)

Then again... it could be an inconsistency. Wouldn't be the first time that a scifi show got it wrong.

Eureka. How I missed you!

I wonder if he will somehow keep that savvy, maybe subconsciously, or if he lost it with his memories?

It will be interesting to see if little bits come back from time to time.

Does Henry only blame Jack? Jack couldn't have gotten back to that timeline without other people's help, and presumably if there were no Jack, Stark or someone would have done it. Maybe going to work for General Dynamics is a plan to get all of them.

Perhaps the combined effect of all the things that happen by random chance perhaps not happening that way again would lead to fairly significant changes in short order?

That's a pretty common assumption in time-travel fiction, such as Ray Bradbury's "Sound of Thunder." Allyson being head of General Dynamics and the boy absorbing something from the Artifact are already big changes.