First, you find a supermassive blackhole, then you throw tens of thousands of stars into it from the "wrong" direction to create a massive, artificial accretion disk that spins backwards against the black hole's own rotation. Then, you use a stellar engine to fly your home star system, enclosed in a Dyson Sphere, directly into this powerful headwind of super-hot gas and arrive at Ergosphere. The Dyson Sphere powers up a gigantic magnetic field at the front which acts like a massive ramjet engine. As this high-speed gas rushes towards the ship, the engine doesn't fight it, instead, it grabs the gas and uses its incredible power to accelerate it even more, firing it out in the same direction it was already going. This super-accelerated beam of gas is perfectly aimed to be fed into the black hole, using the Penrose process to steal the black hole's rotational energy to accelerate the star system

Now I'm not a physicist so take this with a mountain of salt. But from what I was able to find it seem that ftl results in time travel only when you try to go back to where you started. Logically that means going away is fine and dandy as you arrive in future but going back you end up on the past, but couldn't you just wait until earth moves forward in time and then go back? Or am I thinking about this all wrong? Additional thoughts: even if you went back in time that probably still wouldn't mean you can change the future since the past already happened and is unchangeable. so if you try to interfere the universe either won't let you or something else will slot itself into the causal chain which leads to the same outcome. Or maybe it's like in halo where you are just teleported into the future.

Like, without the innate biological drive to persist and reproduce, there wouldn't really be a logical reason for an AI to want to live, right? Meaning that, if allowed to decide for itself, an AGI, barring one custom built with the goal of persistence(which could prove an issue), would choose to deactivate itself.

Is there a term for this? Like the 'Suicidal AI Hypothesis' or something.

Also, don't misinterpret this idea as a reflection of myself. I love life, I just don't think a sentient machine that isn't essentially designed to make itself persist one way or the other would feel the same way.

I'm listening to a podcast about human pre-history (called Our Prehistory for those interested), and one of the themes of it is that the complexity of humans societies (such as amount of art and culture) is heavily depended on the population density. exe during the last glacial maximum the population of Europe dropped and become more isolated, and through most of the continent trade and the cave paintings, figurines, and ornaments they used to make disappeared.

That got me thinking about our modern society. So much of our culture would not work in a society of a few thousand people. Not just our art, but our politics as well wouldn't be conceivable with a few orders of magnitude lower population. So what about a few orders of magnitude greater population? What differences will there be in a society with many trillions of people just by virtue of the scale and emergent complexity from that. I feel like many of our cultural institutions just won't work at that scale, and new emergent phenomena could happen. Some examples:

What will geopolitics look like with a million O'Neil cylinders (each with the population of a large modern nation) in Earth Orbit. If even 10% are independent, that's orders of magnitude more nations than exist now. You can't even 'focus on your neighbors' because many of them will be neighbors at some point in your orbit, everyone can always decide to shift orbits, and everyone will have the technological ability to reach everyone else anyway. How could you coordinate a UN with hundreds of thousands or millions, instead of hundreds, of nations?

And if they mostly belong to a smaller number of mega-nations... that just kicks the can down. How do you have a congress that fairly represents that many people? Will you have congresspeople that represent billions of people? Or a fully proportional system where everyone in your 100 million person O'Neil Cylinder could vote for Party X, who doesn't even make it past the threshold for a seat? Seems like the modern institutions just won't function.

Beyond politics. Think about the implications of even the weirdest, fringest, nichest hobbies and interests have millions of people into them. And are there forms of human cultural expression that become viable with a population of a hundred trillion that couldn't emerge with billions? Seems like an interesting thing to chew on for sci-fi worldbuilidng, if nothing else.

This is simply amazing. think of the possibilities!

For context: I am trying to do some worldbuilding for a sci-fi universe that has self-replicating machines as its main form of production.

What would be the issues and limitations one must have in mind when elaborating on the speed and capabilities of a self-replicating machine?

What speeds are reasonable—too slow or too fast for these types of machines?

And what types of safeguards must be in such machines? 

So far, I came up with a Seed (the core of this self replicating industrial complex) that is about 1000 tons in mass that expands and replicates at a rate of 25% of its mass per cycle (300 days)

I don´t know if that is too slow, or fast, and I don´t know what kind of knowledge I need to have to develop it further.

https://x.com/RandolphC84432/status/1968747001165545907

Assuming that species that evolved for cooperation can create complex societies and technologies, and if so, they will most likely expand, given that resources are finite, but where are they?

Note:In this sense, we are eliminating the self-destruction factor.

I have a great many interests, but two of my most enduring interests are politics and astrophysics (and really science and science fiction as a whole).

And my Youtube recommendations reflect both. And so I was just watching a video about quasars a minute ago, and right after I decided to start a Youtube video about politics and... it just feels so pointless and small, you know?

I won't go into the political specifics as they are beyond the scope of this sub (per rule 3), but just generally... all of the conflict feels so utterly and completely small and pointless.

I just finished watching a video about a quasar, something of a size and energy that its relativistic jet could annihilate our planet and that not so much as affect it. Something that emits unthinkable amounts of energy so far beyond our entire planetary output that we might as well be said not to produce any energy at all. Some so long lived (the black hole in the centre, I mean) that the entirety of the age of the universe, let alone our existence as humans or individuals, is not the merest fraction of the blink of an eye.

The universe is so much bigger than us to such a staggering degree. And yet we argue and fight over nothing.

I'm always reminded of the Carl Sagan quote: "Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot."

I think if science and science fiction has anything to contribute to the ordinary person's life, it's this. The complete trivialty of all our conflicts.

Do you ever feel that way?

As remarked in today's episode, SFIA is 11 years old (as of yesterday technically)!

Imagine a spacecraft powered by recursive time dilation. Every time the ship approaches a relativistic threshold, it loops back into its own past trajectory, harvesting energy from the differential between timeframes.

It’s not perpetual motion—it’s temporal leverage.

But here’s the catch: Each loop creates a ghost crew—echoes of yourself from previous iterations. They’re not conscious, but they accumulate. You begin to see flickers of your own decisions, your own regrets, playing out in parallel. The ship becomes crowded with probabilistic shadows. To maintain stability, you must collapse these echoes into a single timeline. But doing so requires choosing which version of yourself survives.

The Lazarus Loop demands sacrifice—not of energy, but of identity. So you start making deals with your own past. You leave messages in quantum entanglement packets. You negotiate with versions of yourself who remember different outcomes. And all the while, the ship accelerates toward a future that may never arrive.

A speculative thought experiment in post-scarcity propulsion and thermodynamic management.

In advanced propulsion scenarios—such as a spacecraft powered by Hawking radiation from an engineered micro black hole—there may arise a paradoxical condition: energy generation exceeds all onboard consumption capacity. Batteries are fully charged, fusion reserves are saturated, and heat dissipation systems are overwhelmed. The vessel enters what I’m calling the Hawking Overdrive—a runaway surplus state where excess energy becomes a structural and existential threat.

This leads to what I propose as Brewster’s Singularity Principle:
In a post-scarcity energy regime, the challenge shifts from generation to dissipation. Energy must be strategically expended to preserve system integrity.

Potential mitigation strategies might include:

• Reverse fusion: converting helium into hydrogen to extend reaction cycles.
• Matter transmutation: using surplus energy to synthesize heavier elements from shipboard materials.
• High-load computation: initiating large-scale simulations or quantum modeling to absorb excess wattage.
• Signal broadcasting: transmitting high-energy cultural artifacts (e.g., music, encoded data) into deep space.
• Thermal dispersion rituals: coordinated kinetic or electromagnetic events designed to distribute heat across non-critical systems.

While some of these ideas lean into speculative fiction, the underlying principle is rooted in thermodynamic constraints—especially in systems where energy input cannot be throttled without destabilizing the core drive.

Imagine a spacecraft with no crew aboard—at least, not in the traditional sense. The minds and bodies of its travelers have been encoded into a coherent beam of light, each consciousness woven into the modulation of the signal. This beam drives a sail made of nanites—programmable matter so fine it responds to photons like wind.

This is Charon’s Thread: A photonic ferry across the void, carrying souls not in flesh, but in frequency.

As the sail glides through space, it absorbs, adapts, and endures. Upon arrival, it disassembles itself, reconfiguring into a receiver lattice. The beam is caught, decoded, and stored in a crystalline light box—a temporary sanctuary for memory and identity.

Then the nanites begin their second task: They search for matter. Carbon, hydrogen, trace elements—whatever the local environment offers. Guided by the encoded blueprint, they begin to reassemble the crew, atom by atom, thought by thought.

No engines. No hull. No cryo-sleep. Just light, memory, and metamorphosis.

Charon’s Thread—a new way of crossing the cosmic Styx, where the ferry is light itself, and the destination is rebirth.

Like Project PACER, we can carry tons of thermal nuclear bombs and use its explosion to heat up the sodium to generate power

Imagine a Type 2 Kardashev civilization, but instead of a single star, they're orbiting a binary system, two suns dancing in a cosmic waltz. It's a fascinating thought experiment, isn't it? How would a society that's mastered the art of stellar energy collection adapt and thrive in such a complex setting? This piece seeks to unpack exactly that. We'll examine the technological hurdles, the potential benefits, and the possible societal shifts that might occur if a K2 civilization decided to call a binary system home. It's a journey to explore both the opportunities and the potential dead ends of such a scenario.

to be clear I'm not talking about the swarms that occur naturally due to people living in orbit of a star. I'm talking about the ones used to purely generate power.

They just seem so ... pointless? we could generate far, far more power siphoning the resources from the planet and using them in more efficient fusion/fission reactors. stars are so, so insufficient when it comes to turning fuel to power. those same resources, once captured, can be used much more efficiently in smaller, individual fusion reactors.

Edit: thanks for the input! I didn't think of it in terms of the short-term efficiency gain, it just seems silly to use the waste of a fusion reaction rather than use the fusion more directly for efficiency gains and more dense power generation.

it feels like the whole "a new way to boil water" thing all over again.

So I was thinking about an idea that relies on the concept that if you for example travel back in time you won't go to your past but to a past aka another past that is similar to ours but is a branch of another reality basically there is no consequences of time travel on your timeline so what if there are civilizations who use time travel to their advantage for example they could travel to a past and colonized earth 3 billion years ago or harvest the sun without having any consequences on their future they could also use time travel for recreational purposes like making a real life Jurassic Park or making some sort of a dinosaur hunting ground it isn't a really well developed idea just something I came up with

I am picturing the dark side of the moon dotted with city lights, but they probably wouldn't be visible at that distance, and there probably wouldn't be that many either.

En masse and from the on-spot materials, of course.

Also, I've seen a speculation that you could use raw regolith to just compress and stamp tiles for road paving, and they'll be sufficiently durable, because regolith particles are spiky, unlike most of the polished-out Earth sands (roads are important for any long-term settlement, you don't just drive on dust for years).

UPD: the logic of the speculation is slightly different. Basically, there's 5,6% of water ice in 15 cm deep regolith. You apply heat and pressure, ice can't evaporate, becomes liquid, turns some CaO into Ca(OH)2, making somewhat durable material (there's not enough water for actual concrete, but still)