The Compleat Billy Chronicles (thanks to Zenpatista)

[altered]

There's a variation on time travel that's only doable in standard, Everett-Wheeler many-worlds. In that, conservation of energy isn't violated because it's summed over the set of all quantum worlds, so you can conceivably travel to the past, sorta. It also solves paradoxes, because the paradoxes happen to a different "world" -- travel back in time and kill yourself, you aren't REALLY killing yourself, just a different being exactly like an earlier iteration of yourself. Like I said, /sorta/ travelling to the past.

But as a result, stable time loops are impossible -- there's two different "spaces" involved.

Also, there's reason to believe that travelling "close to home" (to worlds we would recognize as remotely like our own) would take mass energy equal to the observable universe, and that you could create what I can only describe as an "extraversal" black hole if you shifted too much mass to a single world (which would manifest as all the nearby worlds having all of their time-like lines end in that world, where they smash into each other and everything ends terribly). So, you know, just hope that we don't live in an Everett-Wheeler cosmology, lest capitalism start collecting bullshit from other worlds and cause ours to collapse into a black hole bigger than the universe.

There's a reason that I'm not a huge fan of Everett-Wheeler outside of worldbuilding and shitposting. Bohmian mechanics is more interesting, still makes all superpositions literally real, and closes all of those awful little holes. (It also opens a far cooler hole of a Platonic/Tegmarkian mathematical universe containing our own, which is the only good and sane form of quantum immortality.)

[Cain]

Everywhere you go, there's always a dumbass.

https://www.independent.co.uk/life-style/gadgets-and-tech/time-travel-possible-grandfather-paradox-free-will-b713939.html?utm_content=Echobox&utm_medium=Social&utm_source=Facebook&fbclid=IwAR2ijBsdVdNXEPDHxb_-Yolv2GXQde_r8rIkrNG7qzuwF1E0-amedh0IUxw#Echobox=1601468055

Is that the best clickbait that a million kangaroos randomly typing can come up with?

Well, yeah.  Which is surprising, coming from the independent.  They're basically saying time travel (to the past) isn't impossible if the universe can forgive a paradox.

It's pure rubbish.  The past is fixed, and you can only change it if you can violate conservation of energy.  Which you can't.  ANY intrusion on the past violates conservation of energy.

The Indy's gotten quite clickbaity over the past few years I'm afraid. Still some solid correspondents and columnists, but they're paying for it on the Buzzfeed model of "shovel as much clickbait as posisble".

[Doktor Howl]

There's a variation on time travel that's only doable in standard, Everett-Wheeler many-worlds. In that, conservation of energy isn't violated because it's summed over the set of all quantum worlds, so you can conceivably travel to the past, sorta. It also solves paradoxes, because the paradoxes happen to a different "world" -- travel back in time and kill yourself, you aren't REALLY killing yourself, just a different being exactly like an earlier iteration of yourself. Like I said, /sorta/ travelling to the past.

But as a result, stable time loops are impossible -- there's two different "spaces" involved.

Also, there's reason to believe that travelling "close to home" (to worlds we would recognize as remotely like our own) would take mass energy equal to the observable universe, and that you could create what I can only describe as an "extraversal" black hole if you shifted too much mass to a single world (which would manifest as all the nearby worlds having all of their time-like lines end in that world, where they smash into each other and everything ends terribly). So, you know, just hope that we don't live in an Everett-Wheeler cosmology, lest capitalism start collecting bullshit from other worlds and cause ours to collapse into a black hole bigger than the universe.

There's a reason that I'm not a huge fan of Everett-Wheeler outside of worldbuilding and shitposting. Bohmian mechanics is more interesting, still makes all superpositions literally real, and closes all of those awful little holes. (It also opens a far cooler hole of a Platonic/Tegmarkian mathematical universe containing our own, which is the only good and sane form of quantum immortality.)

Yeah, that requires that the universe divide.  So if you go back in time, the universe splits, you're stuck there (your original universe is no longer real to you), and your original universe is unaffected.

[Doktor Howl]

Fire Inspector:  "What's that thing?"

Me:  "That's a vacuum chamber."

FI:  "That's a big Goddamn vacuum chamber."

Me:  "Well, it needs to be.  No vacuum is 100%, and if we make expended matter, we want the least possible normal matter to interfere with it."

FI:  "What's expended matter?"

Me:  "Think of it as bad information.  Like prion, but for reality as a whole."

FI:  "Wait.  It would infect reality and make the universe go bad?"

Me:  "The universe is already bad."

FI:  "No, seriously, what could this stuff do?"

Me:  "Medium case, it would start swiping bits out of all nearby electrons."

FI:  "Like a nuclear waste or something?"

Me:  "No, this would be the exact opposite of nuclear waste."

FI:  "Well, that's good."

Me:  "No, it's not good.  It's far worse than nuclear waste.  In any event, we keep it way the hell down in vacuum until it evaporates."

FI:  "How long does that take?"

Me:  "We're a bit murky about that.  Somewhere between 5 femtoseconds and a few hundred thousand years.  But once that time period is up, it's perfectly safe."

FI:  "So let me get this straight:  If you wind up forming this stuff, you will need to keep that vacuum intact for maybe a few hundred thousand years?"

Me:  "That would be advisable."

FI:  "You know we can't keep anything funded for 5 straight years, though?"

Me:  "Well, this has a built-in motivator to keep not only funding attached, but civilization capable of the keeping the power on.  Maybe we could shoot it into space.  But we'd need a very smooth acceleration."

FI:  "I am half-tempted to shut this down."

Me:  "Your mandate includes fires, explosions, releases, and occupational safety.  This is instead a potential galactic extinction event, which is outside of your purview."

FI:  "So who regulates this?"

Me:  "I feel as if nobody thought there would ever be a need for this sort of regulation.  It's one of those black swan things.  An out of context problem."

FI:  "What are the chances that this will actually be a thing?"

Me:  "Somewhere around a hundred-thousandths of a percent.  This isn't about expended matter, it's about expended money.  Money that's gone bad and threatens other money. You are under a million times *this* threat simply by having nuclear weapons kicking around.  That was a boondoggle that worked.  This is a boondoggle that won't."

FI:  "You guys are nuts."

Me:  "What's really sad is that there would be no progress at all if it weren't for people like us."

[Doktor Howl]

Text string today at work:

Dan:  "Any luck with the reaction?"

Hamish:  "I am proud to say we've had success!  It's a great day for the empire!  God save the Queen!"

Dan:  "WTF?"

Hamish:  "Things seem a little sideways, there may have been some localized errors, but it's no bother.  Chin up."

Dan:  "You're fucking with me."

Hamish:  "What was  your first clue?"

[Fujikoma]

I worry what the good doctor may be cooking up in his evil science facility, I come here to get my news, I want to know a little bit ahead of time if the universe is going to undergo a dramatic and nonsensical implosion.

EDIT: I don't want the universe to end while I have money in my pocket, if it must end I want to run out and buy a sandwich.

[Doktor Howl]

Hi folks, my name is still Hamish Howl, and I still beat up electrons for money.

Well, for the moment, anyway.  The Client had a call from a congressman, who wanted to know why federal grant money is being used to fund a potential universe-ender.  It appears that either we or The Client have a rat.  I mentioned to the client that if there are aliens out there, one of them is probably doing what we're doing, or already has, and everything goes down the shitter anyway...So we may as well do it first.

The Client did not seem to realize the potential pitfalls of this project, even though I spelled it out in big block letters in each and every single report.  Which means he DID get it, and just didn't worry about it until the heat came down. 

I tried to reason with him.  A congressman can't give you grief if you already shut the universe off.  He pointed out that the universe-ending bit wasn't what the project was about, but just a side effect.

NEWS FLASH:  If you cause vacuum collapse, it doesn't *matter* what the main objectives were.

So I am guessing that the gravy train on this particular steaming pile of boondoggle is coming to an end.  Which sucks, really, because the theory could very well be sound, and it's just that we're cave men trying to build a space shuttle, accumulated knowledge-wise.

[LMNO]

Once it's all over, will you be able do discuss the details more?

[Doktor Howl]

Once it's all over, will you be able do discuss the details more?

Yeah, but actual technical details don't belong to me, so I can only talk in generalities.

[Doktor Howl]

This twerp is partially responsible.

https://arxiv.org/abs/1712.07962

[Doktor Howl]

The project is officially dead.  Like Nancy Spungeon dead.  Details tomorrow.

[Faust]

I'm sorry for you loss, also that is a huge relief

[Brother Flight Risk]

Reality is safe...for now.

[LMNO]

I have found that reality is rarely safe.

[chaotic neutral observer]

This twerp is partially responsible.

https://arxiv.org/abs/1712.07962

One of the more bizarre properties of negative mass is that
which occurs in positive–negative mass particle pairs. If both
masses have equal magnitude, then the particles undergo a process
of runaway motion. The net mass of the particle pair is equal to
zero. Consequently, the pair can eventually accelerate to a speed
equal to the speed of light, c.

This is where this guy lost me.[/quote]

Let's say we have a positive mass and negative mass particle (same magnitude, different signs) approaching each other (for them both to start out at rest seems unlikely).  Let's also assume they're not on a collision course.  As they get closer, the gravitational forces increase, and they begin accelerating in a direction corresponding to their relative position.

Since the particles are experiencing the same acceleration, their relative motion remains unchanged, and, since they're not on a collision course, they'll eventually start moving apart again.  But, at this point, the relative positions of the two have been reversed, and the acceleration will be in the opposite direction, which will cancel out the original acceleration, eventually restoring them to their original speed.

Post fly-by, the particles are going to have moved quite some distance away from their original location (given all the acceleration involved), and their trajectories will probably have deflected, but they aren't going to be moving any faster than they were at the beginning.  So, I don't see how you can get them up to c.  (Unless, perhaps, they start out their existence at exactly zero relative velocity, which would be a neat trick).

Maybe someone who actually understands physics can correct me.

(edit:  Hit modify instead of reply - Howl)