Asklemmy

You could set up your own wifi hotspot and become your own free ISP, undercutting any private company seeking to dominate the area. It'd usher in that wonderful wild-west age of the internet

you can guarantee that at least one time travel willeth have ridden a dinosaur at some point

right? walk a mile in the average person's footsteps.

Though I'm now imagining some weird guy bursting into my house in strange garb, just as I'm about to go to work, excitedly pointing at my vacuum cleaner, and the bills on my table, and exclaiming "this is brilliant!"

I think that might be a convenient myth used to gloss over the power imbalance that led to indigenous women being used as such

Oh WW2 London is a fave of mine. I've always wondered what the slums of Deptford looked like. Right now it's an overly gentrified rich person's suburbia, but back then it was the rotted lungs of the shipping industry. It would be also nice to know what it was like hiding out in the tube with a bunch of strangers. Did anyone play music? Was there singing above the praying? Did people trade books and cigarettes?

I mean he disappears for a few days after and seems good afterwards before vanishing forever, so chances are you were there and you intervened

You'd need a translator, and probably a bunch of inoculations first.

Those last two might require some careful planning on where to be to witness those events safely

"what would you do if your basic needs were met?"
"chill the fuck out"

seems like a solid answer to me no joke

Possibly Ghengis Khan too. And a handful of Roman Emperors and European royalty.

Give all the natives AK-47s and tons of ammo

It might just be a bistro

Put on fake ears and paint yourself green

That'd take a long time unless you skip ahead a few years every now and then

No air

Or 1337?

Many Worlds is an incredibly bizarre point of view.

Quantum mechanics has two fundamental postulates, that being the Schrodinger equation and the Born rule. It's impossible to get rid of the Born rule in quantum mechanics as shown by Gleason's Theorem, it's an inevitable consequence of the structure of the theory. But Schrodinger's equation implies that systems can undergo unitary evolution in certain contexts, whereas the Born rule implies systems can undergo non-unitary evolution in other contexts.

If we just take this as true at face value, then it means the wave function is not fundamental because it can only model unitary evolution, hence why you need the measurement update hack to skip over non-unitary transformations. It is only a convenient shorthand for when you are solely dealing with unitary evolution. The density matrix is then more fundamental because it is a complete description which can model both unitary and non-unitary transformations without the need for measurement update, "collapse," and does so continuously and linearly.

However, MWI proponents have a weird unexplained bias against the Born rule and love for unitary evolution, so they insist the Born rule must actually just be due to some error in measurement, and that everything actually evolves unitarily. This is trivially false if you just take quantum mechanics at face value. The mathematics at face value unequivocally tells you that both kinds of evolution can occur under different contexts.

MWI tries to escape this by pointing out that because it's contextual, i.e. "perspectival," you can imagine a kind of universal perspective where everything is unitary. For example, in the Wigner's friend scenario, for his friend, he would describe the particle undergoing non-unitary evolution, but for Wigner, he would describe the system as still unitary from his "outside" perspective. Hence, you can imagine a cosmic, godlike perspective outside of everything, and from it, everything would always remain unitary.

The problem with this is Hilbert space isn't a background space like Minkowski space where you can apply a perspective transformation to something independent of any physical object, which is possible with background spaces because they are defined independently of the relevant objects. Hilbert space is a constructed space which is defined dependently upon the relevant objects. Two different objects described with two different wave functions would be elements of different Hilbert spaces.

That means perspective transformations are only possible to the perspective of other objects within your defined Hilbert space, you cannot adopt a "view from nowhere" like you can with a background space, so there is just nothing in the mathematics of quantum mechanics that could ever allow you to mathematically derive this cosmic perspective of the universal wave function. You could not even define it, because, again, a Hilbert space is defined in terms of the objects it contains, and so a Hilbert space containing the whole universe would require knowing the whole universe to even define it.

The issue is that this "universal wave function" is neither mathematically definable nor derivable, so it only has to be postulated, as well as its mathematical properties postulates, as a matter of fiat. Every single paper on MWI ever just postulates it entirely by fiat and defines by fiat what its mathematical properties are. Because the Born rule is inevitable form the logical structure of quantum theory, these mathematical properties always include something basically just the same as the Born rule but in a more roundabout fashion.

None of this plays any empirical role in the real world. The only point of the universal wave function is so that whenever you perceive non-unitary evolution, you can clasp your hands together and pray, "I know from the viewpoint of the great universal wave function above that is watching over us all, it is still unitary!" If you believe this, it still doesn't play any role in how you would carry out quantum mechanics, because you don't have access to it, so you still have to treat it as if from your perspective it's non-unitary.