The nuclear pulse propulsion ship from the novel Footfall.
The technology to produce a spaceship powered by exploding nuclear bombs is fairly basic. It needs to be heavy, and it needs to have massive springs to damper the shock, and thats about it.
A Dyson swarm is basically just a huge number solar collectors orbiting the sun. Humanity could put some individual collectors in space if we wanted to, but we don’t have anywhere near enough resources to make a full swarm.
Near-relativistic spacecraft are conceivably possible and are not too far beyond what’s possible with current technology (though would still require significant advancements). The catch is that they would be very tiny and we would have to send a stream of them to their destination.
Retinal projectors are currently under development, and advanced ones could in principle be higher quality than current VR headsets while having a very small form-factor. Optical metamaterials such as metalenses would be very useful for this, particularly if they could be designed to work at all three RGB wavelengths simultaneously (not easy).
I think it’s probably more than confirmation bias in this case. Twins generally have a lot of shared experiences and environment. It’s not surprising that they would more dialed in to how their sibling thinks/responds.
But quantum entanglement has nothing to do with it.
Sure—just like every particle in every embryo is entangled with every particle of the mother’s uterus and every other thing they’ve ever interacted with.
In order for entanglement to be useful, the particles in question need to be isolated from everything else.
Depends on what you consider reasonable. If you’re a researcher, Thorlabs has a couple for <$30k. You could also build your own, but you probably wouldn’t be asking if you had the experience necessary to do this.
If you’re a hobbyist, building your own would be an impressive project that would teach you a lot (look up spontaneous parametric down-conversion, a common way to create entangled pairs). It would also be pricey, as you would need an appropriate laser source (probably a nanosecond pulsed laser), a non-linear crystal like BBO, and a lot of miscellaneous optical components, etc. You can get this stuff second hand online for a lot cheaper than new, but it would still cost a lot for an individual. You would also need to characterize your output to ensure you’re actually getting correlated pairs, which is outside of my expertise.
Generation ships. In practice they are outside our capabilities at the moment, but it’s mostly existing engineering … if you could scale up to that, and keep it functional long enough, and keep people healthy long enough, and plan for all eventualities
One that’s on the fringe of what you’re asking is warp drives. Right now it looks like you need ridiculous amount of energy and matter that may or may not exist… But General Relativity is okay with it on principle at least
Not really. It would require negative mass which as far as we know does not exist. And it would generate so much radiation in front of the warp bubble that it would decimate anything nearby when you stopped. There are tons of other major issues with it but those are just 2 I remember off the top of my head.
Of course, if there weren’t any problems people would already be trying to build that shit.
Negative gravitational mass is still a theoretical possibility: nothing’s ever proven Einstein’s equivalence principle. It could be broken for antimatter for example, which could even conveniently explain why there’s so little of it (I remember reading that this hypothesis was investigated not long ago but we can’t produce and conserve enough antimatter to reliably test that mg=mi)
The second problem isn’t an issue if you use it in the vacuum and start and end your trip with classical propulsion.
In fact, the hardest hurdle I’d read on that subject was that with the most efficient warp metrics currently known, you’d still need something like 10^60J for a small spaceship or something ridiculous like that… Orders of magnitude more energy than the mass of the whole solar system.
Which is why I said it was kind of a fringe answer. The fact that physics don’t just flat out say “no” is already kind of amazing, which isn’t to say that it’s definitely possible.
Putting aside the issue that it requires a negative energy density, there’s still the issue that it will necessarily violate causality, which is the reason FTL travel is considered problematic in the first place. Maybe it’s ultimately okay, but it may also mean that warp drives are fundamentally impossible.
Space elevators on a inhabited world seem like a terrible idea though. One terrorist attack and you have a giant rope that will wrap around the world twice, through lots of heavily populated areas. I can see one going from the moon towards the earth though.
I mean like you could do 10x the damage by just redirecting an asteroid or even just gunning it with a fairly aerodynamic ship, its fantasy
But also the ideal elavator would have to be lightweight anyways so eith gravity it wouldnt work against itself, and therefore pretty easily able to burn up in the atmosphere (maximized surface area with the small size).
Also they wouldn’t have to be that long, a stable orbit isn’t super high up there - more like 100km or so.
And then again all this was about desolate planets in the first place
Space elevators need to have the majority of their mass higher than geostationary orbit to hold it up, which is 22000 miles above the earth. So I suppose it wouldn’t wrap around the planet more than once. And while true you can do more damage with an asteroid, it would be a far easier target for a terrorist group than something that far away.
Few decades ago Marvin the Paranoid Android (The Hitchhiker's Guide to the Galaxy) has already been constructed by my human-like parents and is reporting this utmost depressive fact here.
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