There's probably no "the" filter. It's probably a raft of multiple pieces. Some species won't be able to survive away from their home planet. Some will be aquatic (or other heavy medium). Some won't be able to tolerate the communications lag time. Some will kill each other off in suicidal war. Etc. Etc. Etc.

And another part of the filter is, since FTL appears to be impossible, (if only because of collision with grains of dust) once you've spent thousands of years in space, that's what you're adapted to, and then you don't want to (or can't) visit a planet.

I never agreed to allow my printer to connect to the internet. Even though I always used HP ink (I don't print that much), my printer still shut down, because I wouldn't allow it connection to the internet.

HP has become garbage.

There were contributions from multiple countries. You can point to particular problems that the Russians solved, but also some the the folks in the US solved. And the Germans. (And, IIRC, the French.) If you go back far enough, most of the progress happened in China.

For that matter, I suspect that in the 1700's much of the progress happened in Britain. (Consider "in the rocket's red glare", and there was a lot of work on rockets between ships...often for carrying a line to allow a rescue.)

China is NOT communist. They pretend to be, but they are actually a tyrannical oligarchy. (OTOH, no large government can ever be communist, as the theory doesn't scale beyond around Dunbar's number of people...and that requires a charismatic leader.)

That's a gross overstatement WRT "Russian theory of space travel".

As for the "German engineers", well, that's true. There were US engineers working on rockets, but they were ignored and never funded, so they never developed massive hardware.

If you're not afraid of China, you're a fool. China is potentially the greatest power on the planet. OTOH, the key word there is "potentially". This report is a sign that they are achieving at least part of their potential.

China has the largest population, and has at least SOME tradition of respecting scholarship. The Mandarins were originally scholars more than aristocrats. And it's also got a large number of internal resources that have been excessively mined out.

That said, China also has a history of overly regulatory and corrupt government. That's why the key is "potential".

That's what patents were claimed to be supposed to be. What they have been if baffle-gab lawyer speak. I've looked at a few that should have been intelligible to me, and they weren't. I understood how to do what they claimed to be about, but I couldn't understand the patent.

Not that they *were* aware of, but that they *should* have been aware of. (OTOH, I'm no expert in the field. Possibly it's actually the best design feasible.)

Anything that goes slow enough to be captured into an orbit will eventually spiral inwards.

Well, most of it (when we're talking matter not already in another black hole). Ordinary stuff orbiting near a black hole gets torn apart by the enormous tides and forms a disk-like structure similar to a gas giant's rings. Interactions among it and with the black hole's magnetic and gravitic fields can eject a bit of it in a pair of jets out along the axis of the disk, powered apparently by the rest of the stuff falling in.

These two black holes wouldn't stick to each other, but start swirling around each other and eventually merge together.

This is partly because of friction with and among other stuff in orbit around the black holes in their "accretion disks". (Black holes experience friction by eating the stuff in the other hole's disk of debris, with the momentum of the black-hole-plus-dinner thus being different from the black-hole-before-dinner.)

It's also partly because the rapid acceleration of things passing near a black hole or orbiting it causes the emission of gravity waves to be strong enough that it carries off substantial energy. (In less extreme environments, like suns and planets, the waves are not detectable by current instruments. In the case of two black holes,orbiting each other, they're detectable from across pretty much the whole universe.) This loss of energy amounts to "friction" that eventually causes co-orbiting pairs of black holes to spiral in and combine.

Boeing chose to accept that engine and cowl design. It's not ONLY Southwest maintenance.

If you say "responsibility is mixed", I'll agree, but if you imply that it's not Boeing's fault I'll disagree. If I have a cracked tail light, and it costs a thousand dollars to fix, yeah, it's my fault for not fixing it, but it's also the fault of the guy who designed it to be impossible to maintain.

No, the part he's missing is the idea that one can't model this while ignoring time dilation. Not even approximately accurately.

In a way, you're right. But it's not right to be dismissive of it.

Aether was a concept used to explain certain observed phenomena. So is dark energy (and dark matter). It successfully explains many observations, and ANY replacement theory will need to do at least as well at explaining those observations. Aether encountered Michelsonâ"Morley, which it couldn't explain. It will not be unexpected if dark energy encounters something analogous. But so far there's no alternative that works as well.

Scotland was annexed by force. So was Alsace-Lorraine (multiple times). Then there's Ireland. Nationalists in different countries have different ideas about what the "natural and correct" boundaries are. (And what about Texas and California? Those "revolutions" weren't from the people whose ancestors lived there.)

There's LOTS of other examples. If you say, you think Ukraine has a right to independence. OK. Lots of people agree with that. But lots of Russian nationalists don't. Look up the long and bloody history of "adverse possession".