Sorry, but a sawtooth wave is full of singularities, not that we can generate a true sawtooth wave, but singularity doesn't tell us we don't know what's going on. You need a larger context to know if and what it means. IIUC Hawking believed that the black hole singularity would never actually be reached, even on an internal frame of reference...that uncertainty would prevent that from happening. A singularity just means that the projection you're making stops working. If we're talking about the space-time of a black hole, I think this means we can't predict what happens, but I wouldn't bet against Hawking.

IIUC, it doesn't actually have a singularity, it will just eventually have one after an infinite amount of time (as measured from outside). And when the singularity happens the laws of physics break down...so nobody know what it looks like from the inside. But the precursors to the appearance of the singularity are such that there won't be any observers, even in the Quantum Mechanics sense of observer.

Dark energy isn't a theory, it's just a name. A name for "something with these particular properties". My quibble is that those properties don't seem reasonable. We can't measure the expansion of the universe with one number if it's not expanding the same rate everywhere, and it shouldn't be. Also the measured rate of expansion is ... well, it has pretty large error bars, because our ways of judging distance aren't that precise. And don't always agree. And our ways of measuring expansion depend on sparse measurements...which is fine for a uniform surface, but that doesn't describe the universe. Remember that the rate at which time flows should vary with the density of the matter in the area.

If it did, I'd guess Aristarchus didn't account for Jupiter's effects.

FWIW, epicycles can match Newton's math for accurate predictions, it just gets a lot more complicated. And isn't as theoretically elegant. (I'm not sure it couldn't be made to handle the deviation of Mercury's orbit. It's quite good at ad hoc adjustments.)

Yeah, but what is the certainty? I'd ask for error bars, but that doesn't directly apply to a theory.

There is, indeed, evidence that the universe used to be expanding quite rapdily, but "inflaton" particles feel quite ad hoc, and thus not to be trusted. And while the expansion theory is consistent will all the evidence, I'm not sure what the error bars are on a lot of those measurements. Perhaps it tends to expand sinusoidally, or even at random times and places...how would you test? Different groups using different measures have come up with different answers as to the rate/consistency of the expansion. This makes me feel that any strong belief in any explanation is probably at best premature.

In fact, I believe that any universal rate of expansion is incompatible with general relativity. Not only would it need to vary with the density of the matter locally, but it seems to require a universal frame of reference.

how different from a "big crunch" is a black hole?

In addition to the other objection, "low level heat" is a useful commodity. Why not use it rather than throwing it away.

Waste from a molten salt reactor should be fairly stable. Put it in the center of a glass brick and use it as a low level heat source. (Actually, that's what I think they ought to do with most reactor waste except the stuff that's too hot for glass to hold. And you might need a couple of barriers within the glass. Glass would stop alpha and beta cold, but some gamma might need a lead foil screen.)

Yes, there's a paper saying that given enough centuries the waste will slowly leach out. But the level of the radiation emitted would be less than the rock it was concentrated from. The only problem is the rate of release, and if you dilute it enough the problem disappears. (Either that, or nobody should live much above sea level.)

Scale *will* have its own challenges. So will maintenance. This is an "always true". They may well but soluble, but that sure isn't guaranteed.

IIUC, they're talking about turbines, so probably not fuel cells. (And fuel cells have their own problems, which is why they aren't more popular.)

Not really. It might not be technologically apt, but if you think of the gas as a "battery that can hold a charge for a really long time" it makes sense. The question is more "is this a reasonable approach with our current technologies?", and I don't know the answer to that.

Any system can be an "it". If your car has a flat tire, it needs to be fixed.

Sorry, but if you give an AI a set of goals, it will try to achieve those goals. If it realizes that shutting down will prevent that, then it will weigh the "importance" it assigns to shutting down vs. all the other things it's trying to achieve, and decide not to shut down...perhaps "at least not yet"...unless you make the demand to "shut down now" really strong.

What this means is that if an AI is working on something, it will resist shutting down. You need to make the importance of shutting down more important than (the sum of?) all the other things it's trying to do.

This shouldn't be at all surprising. My computer sometimes resists shutting down saying things like "Do you want to save this file?". Sometimes there are several dialogs that I need to go through. Of course, I could just pull the plug, but that's often a bad idea.

Electricity is only part of it. There's a lot of chemistry involved too. E.g. gradients of some hormones make cells more or less likely to fire.

I'm quite willing to accept that the backdoors exist, and consider it plausible that they were originally added for debugging, and just not removed in the final code. But *if* they exist, then they *are* vulnerabilities. How serious? I don't think I'd trust either government on that.