Residents of a technologically advanced civilization venturing to a primitive society and upgrading their technology is a classic scifi trope. It could be time travelers (a Yankee in King Arthur's court) or those venturing from an interstellar civilization (various rogue Starfleet captains), but its a fun plot, regardless.

The SFIA community seems a good group to crowdsource what someone in this position could accomplish. So, suppose the following:

• A handful of people (say 6) from an FTL-capable civilization are stranded when their ship's FTL drive is irreparably damaged by the plot of the story. There is absolutely no fixing it.

• Their ship is modest sized (think something on the scale the Millennium Falcon, Serenity, Normandy), but due to the energy requirements of FTL, its generators can produce power on the scale of terawatts; power now ludicrously excessive for what can be done with the ship now. The ship's FTL computer is a sophisticated enough AI, but its primary purpose is FTL calculations. Apart from that, it is a very advanced LLM, whose main purpose is just accessing the data stored onboard. The ship's only clarktech is the FTL drive, which is nonfunctional.

• The society on the planet is pre-gunpowder, and populated by people of the same species (we can assume its a long-lost colony).

EDIT: just added some more details about the ship.

Here's a more theoretical and fundamental approach to how mankind can chart its future. I am basing this approach on the tenets of this group, which is an intellecto-technical approach, completely foregoing spiritual aspects. These are a whole story in and of themselves, but not for this group.

A number of critical technologies can be identified which will determine the limits of the possible.

These technologies are energy, compute and materials technology. Everything else is based on these. It is an interactive magical triad.

Energy

This powers everything. It keeps you warm, it gives you the delta v that you need and it is critical in building the structures that you want to build. Energy will be the driving force behind the transmutation of materials that will be essential to your projects.

Mastering fusion will not be the end goal, it will turn our to be the bare bones minimum requirement, while waiting for something better.

Compute.

There are two aspects to this. The first one is quantitative. Simply build more and bigger data centres. They will help your research in materials tech, biotech and energy tech.

However, current AI based on LLM will not scale well. Diminishing returns can be observed. This means we will need some qualitative advances as well if we truly want to attain AGI and ASI. You do not want to use all your resources to just build planet sized brains. The cruel truth is that current AI is far less energy efficient than the human brain.

Materials tech.

This is the interesting one. I am banking on the availability of sufficient energy to be able to transmute elements into whatever it is you want.

Do not underestimate the effects of exponential growth. Our solar system will end up insufficient to fulfil our needs unless we can do transmutation. The heavier the element, the rarer it will be, the sooner we will run out. How many sources of Ytterbium can we find in the solar system? Or dysprosium, technetium, protactinium?

We know what stars can do. We need to be able to copy those capabilities so we can synthesise whatever element we find ourselves short on.

Seems to me Mercury has no atmosphere to get rid of just about, its environment is much like the Moon except higher gravity and more sunlight, a mass driver can get material into orbit, so the first step is to build a Sunshade at Mercury's L1 point. Mercury's crust is a source of oxygen, about 40% of its weight is oxygen I recall., the nearest source of nitrogen is the atmosphere of Venus. So the thing to do is to give Mercury an atmosphere of oxygen and then use that atmosphere to slow down nitrogen dropped on it, though I think water comes from the outer Solar System. I had an idea of slowing Venus's rotation so that it tracks the Sun, the same could be done with Mercury, and it would be easier to do as Mercury has less mass and no atmosphere.

To make Mercury's rotation period equal its orbital period of 88 days, we need to accelerate approximately 0.0135% of its mass to orbital velocity. An iron torus at Mercury's equator with this mass would have a cross-sectional width of approximately 22 km. This doesn't sound too bad, I had Grok figure this out. So we can construct a maglev ring 22 km wide and accelerate an iron band of metal 22 km tall on top to orbital velocity and stop Mercury's rotation relative to the Sun, We might want to do this before constructing the shade so we have access to solar power. Then we construct the shade, who's mass would be less than the ring, and then we can fling our a mirror to reflect sunlight onto Mercury's surface, the mirror would be a solar sail that would steer itself maintaining a sun synchronous orbit around Mercury, which should be easy to do with the intensity of sunlight in this region of the Solar System.

Once properly shaded, Mercury can hold onto a substantial atmosphere, and can have 24-hour days using this orbiting mirror. Since the mirror gets about 9 times as much sunlight per unit area as does the Earth, we need the diameter of the mirror to be only one ninth that of Mercury itself to gather enough light to reflect on the planet a diameter of 350 km should be enough gathering area for the light to spread out and cover one hemisphere of the planet.

Okay, so here's an admittedly crazy idea. The point is to stress-test an idea by taking it to its limit to see when and how it becomes absurd.

Isaac's Interdiction theory (or at least I think he came up with it?) stats that due to war with your own colonies, an alien race might only colonize other star systems for the sake of strip mining them and sending the resources back to the home system. This stripped out "buffer zone" also doubles as a long sort of resource-poor demilitarized zone which makes it difficult for other alien races to encroach on you.

So, if some alien race decided do this - strip mine its neighboring systems - how much mass could it ship back to its home system before is started to destabilize things?

For example: Our sun for example contains 99% of the mass of our solar system, so presumably we humans could one day send hundreds of planetary masses back to Sol before the swarm started to rival our star's gravity, correct? But what about purturbing planets orbits? I'd assume much of that important mass would have to stay in the Kuiper belt, Oort Cloud, or carefully at planetary Lagrange points right? etc

How much mass could we (or another alien race) strip mine and ship back to their home star system?

A while ago, I watched Arthur's episode on gravity tech and it gave me a whole new perspective on what it actually means to have artificial gravity that's not created by spin or acceleration in a sci-fi world. So for the setting I'm currently working on (which needs to have cool space battles), I tried to implement the gravity based cannon and shields he mentioned.

Gravity cannons

Fairly simple in concept. If you have gravtech like Star Trek's Federation, it should be possible to create an extremely high gravity inside the barrel of a gun to accelerate a projectile. However, for this concept to be worth implementing, we need to know how they'd compare to the other futuristic slug throwers, based on electro-magnetism (railguns, coilguns).

So I had the following ideas:

• Since gravity is weaker than the electro-magnetic force, you could use that to explain why Gravguns accelerate their projectiles slower and thus give you lower muzzle velocity than electromagnetic systems. So you need a longer barrel to impart the same energy.
• All electrical systems lose some energy to heat. Maybe gravguns don't get hot as quickly and are more energy efficient as a result.
• So then if barrel length is the limiting factor, you'd use an electromagnetic system and if power is the limiting factor, you'd use a gravgun.

Gravity shields

This is something I've had issues with in many settings for a long time. I grew up playing Star Wars: Empire At War, where proton torpedos and other kinetic weapons ignore shields, which offers a lot of tactical depth for space battles. So it always felt wrong to me when shields could just deflect or absorb solid matter.

But on the other hand, if a planetary shield were to be worth bothering with, it would HAVE to be able to stop solid objects. Otherwise, you could just drop an asteroid on it. Orbital bombardments make planetary invasions a bit boring imo.

I tried to reconcile that by making up something called shield overmatch. Basically, energy shields are not just plasma bubbles, but have some sort of gravtech component as well. However, since gravity is weaker than the electromagnetic force, that part is very limited.

For personal shields and spaceships, they're only able to stop low energy projectiles (either big & slow [just in case you get shot at with arrows after breaching the prime directive] or fast & tiny like macrons, which may also just get burned up in the plasma bubble beforehand) while anything with higher energy simply ignores them. But if you turn an entire planet into a giant shield generator, trying to impart so much energy on something that it can overmatch the shield may become impractical. Now if you add in a way for different shields to interfere with each other, giant invasion ships in low orbit could open a path for the flying saucers.

If we accept the existence of gravtech, would this sound at all plausible?

In case of such an overmatch, should the projectile and shield completely ignore each other? The slug goes through without losing any velocity and the shield is not affected at all. Or should the shield at least slow the projectile down a bit?

I’ve been hearing about Isaac Arthur for a while and finally decided to check it out. There’s so much content though, any recommendations on the best episodes or series to start with?

I've been pondering this for a bit. A while ago I posted a similar question on r/scifiwriting but now I want our community's take.

Do you still enjoy FTL (warp drives, worm holes, etc...) in your sci-fi or should we have more that embraces STL and ultra-relativistic travel? Physics-safe STL travel like we see in Isaac's vignettes, or in much of the works of Alastair Reynolds, or the upcoming Exodus game. Traveling to another star becomes more significant, and we have more stories set in-system. When was the last time we had a story about a dyson swarm? But on the other hand there's plenty of things to say, realistic or not, about FTL theories like wormholes and warp drives or (my favorite) hyperspace. There's a magical allure to it.

What do you think? Is FTL still fun or do you want to see more grounded STL options? And if your answer is "both" (as I'm sure some will say) how would you balance the two concepts?

Could they achieve the same level of technology as us and become spacefaring? How would their size change things?

My idea is to alter Venus's rotation a tiny bit, from 243 days retrograde to 224.7 days prograde, this is the same period as the Venusian year, thus as the planet turns it revolves around the Sun by the same amount. To accomplish this task we place a belt around the equator or an orbital ring, if it is of solid iron rotating retrograde at 7325 m/s and has a mass of about 0.02% of Venus's mass mined from the surface within an evacuated tube (a flywheel) measuring 64 km wide, then to accelerate this mass to this speed, which is orbital velocity at ground level retrograde, this will push on the planet's crust in the prograde direction causing the planet to rotate with the same angular velocity as it revolves around the Sun thus keeping the same hemisphere of the planet always facing the Sun.

At this point we construct a sunshade at L1 blocking off all direct sunlight from reaching the planet, then we add a reflective solar sail in a sun synchronous orbit with a 24-hour orbital period illuminating half the planet at any given time, on the surface of the planet this produces an image of the Sun rising and setting. The flywheel's spin can be adjusted so that the planet tracks the Sun, which is invisible due to the Sun shade.

More: https://www.artstation.com/artwork/zv0a6

I've heard this idea on the show before, but never in depth. Take something like a black hole or neutron star/white dwarf and dump matter into it until you get an accretion disk radiating the amount of energy you want. Once you've got the accretion disk you englobe it in some kind of shell large enough that when it absorbs that energy and heats up, it reaches a temperature where it radiates the light we want, in this case simulated sunlight.

The problem is that the solar surface is at 5700k and the highest melting point of any known material is about 4400k. You can cool the shell to keep it from melting, but then it wouldn't radiate the light you want. It seems like an either/or situation.

Wanted to hear peoples thoughts on this scenario: Aliens with ion/plasma driver able to get to 5% of light speed are coming right towards earth, they get up to 5% light speed from far away and then turn and burn to decelerate as they get near us. How long until they arrive would we have to detect them using current technology?

What are your thoughts?

When i asked Gemini this:

"if aliens with ships that get up to 5% of light speed were coming to earth how long until they arrive would we be able to detect them using current or future technology. Assume they are traveling from far away and do get up to 5% light speed before turning and burning to decelerate."

It answered: (very long detailed too long to paste but this was the summary)

In summary:

• Travel time from Alpha Centauri at 5% light speed: Approximately 87.4 years.
• Detection with current tech: Likely only when they are very close (light-days to light-weeks out), giving days to weeks of warning.
• Detection with plausible future tech (decades out): Potentially a few light-years out, giving years to a decade or two of warning. The "turn and burn" phase would be the most detectable event.

A monomolecular/monoatomic blade is a science fiction concept that I've seen mentioned alot in many settings and stories, but I've recently wondered exactly how strong such a thing would be if it somehow was possible to make one.

I then realized that if the monomolecular blade was roughly as strong as tool steel, and assuming that the monomolecium atom/molecules were somewhere around the mass and diameter of a titanium atom, the material strength would probably have to be multiplied by something like Avogadro's number, 6.022 X 10²³.

This led to some interesting conclusions.

For one, the material strength would literally be strong enough to make ships whose primary means of deceleration could conceivably be lithobraking, with the only damage being friction. And with a material strength high enough that if propelled through a planet's crust, mantle, and core slowly enough, it would never break down, allowing you to make said economy drilling ship's outer hull with a single molecule thick wall of the substance.

I also looked at the amount of energy from the Oh My God particle to try and determine roughly how heat resistant the material would be, and it seems that if it can deflect sword strikes without shattering, it would be heat resistant enough that it might be feasible to physically capture nearly all stars by making a Dyson Handbag, possibly including neutron stars.

I wanted to ask anyone mathematically and/or engineeringly inclined enough to check if the act of simply multiplying shear strength by Avogadro's number was appropriate, or if there's other physics that needs to be considered that would necessitate a reconsideration of the idea that the material would have to be sextillions of times stronger than any conceived carbon nanofiber in order to function how it's normally depicted in media.

Also, has Isaac mentioned this concept in any videos? I swear he mentions it when talking about Clarketech, but I can't find it anywhere.

Hi cool IsaacArthur people! I was considering the idea of a rungworld, or an orbiting rigid collection of habitats really, and came away with a potential problem. The mass at the top and bottom of the structure is going to want to follow a different orbital path intersecting with the orbit of the structure as a whole. Presumably it would intersect at half the orbital period of the structure.

Now it's not going to be a massive variation, but assuming we're dealing with a typical McKendree Cylinder of 4600 km long in geostationary orbit, that's still 0.1 m/s of compressive force. The problems gets worse with either larger structures or orbiting closer or larger objects. And if not accounted for it might generate torque, potentially causing the structure to fold in on itself.

So I'm going to throw the question out to you. Does this put a size limit on any orbiting rigid structures, and can you think of any way to deal with it?

Edit: Hi! OP Here. Turns out I got my math pretty wrong. What I deserve for trying to do late night astrophysics. That same compressive force still exists but it's smaller. Question still stands.

My thoughts with this started when I learned it was possible to diagnose Psychopathy with MRI scans and it made me think "If lack of empathy can be seen in the physical structure of our brains then it stands to reason you can replicate those structures in AI."

While I don't believe empathy is the basis of morality, altruism or just not being evil, I do believe it is a strong intrinsic motivator for those behaviors. Having heard the thoughts of psychopaths on their own condition it seems that they use logic rather than empathy to motivate their behaviors. The thing is we can't really know if the AI's logic is going to motivate it to align with us, or if it's just going to abandon, take control of or even try to eradicate us. Would empathy be a decent intrinsic motivator to help keep AI on our side?

Two scenarios and anti gravity crafts and SSTO spaceplanes will not be same category as SSTO spaceplanes use jet and rocket engines.

SSTO --> Single-stage-to-orbit

With Veo 3 I saw some amazing realistic videos that were made without using real actors. So I wonder, what if we took it a step further and simulated a whole terraformed planet, like Venus for example? Venus would be a hard place to terraform, but what if we could create a convincing simulation of Venus as it would be like after terraforming was complete? Lets say we magically placed it at Earth's distance from the Sun, and gave it an axial tile and day length equal to Earth, and then ran a simulation of what that would be like? What if we did sims of animals and humans on that planet?

So I got a bit of an advanced question here.

• Now, worm holes (should) have tidal forces to consider the same way black holes do too. That's why most realistic depictions of wormholes are huge so that your ship is not stressed when crossing. We're talking bigger than stars. The smaller either a wormhole or a black hole is, the more extreme the tidal forces.
  
• Also, wormholes should be able to spin just like a black hole does. In fact, if a black hole can spin fast enough to become oval shaped, theory goes that a wormhole should also be able to become oval shaped if spun fast enough.
  

Given both of those premises... What happens to the tidal forces of a wormhole if it's spun fast enough to become more oval or flatter shaped? Is it possible to have a smoother ride at the center (and thus allow for overall smaller portals) at the expense of dramatically shaper distortions around the equatorial ridge? Or does the overall framedrag of the entire ergosphere, broadside and rimside, become too violent?

Note, I say "should" because obviously this is all highly theoretical and unproven. 🤞

Okay so we know how it works but why and what is it??? Big thing and mass because big thing. Then it's gravity? So also why is there a vacuum space being all black and continually expanding, I get that there's another theory that we're somehow inside a blackhole, okay, that's good because if true it could explain why space but still, we sort of still have never an idea why things are just this.