The idea that astronomers had stumbled on such a structure triggered headlines round the globe – though not for long. Subsequent research has now undermined the idea. “We have found that light of different wavelengths is blocked in different amounts: exactly what you would expect from starlight passing through a dust cloud,” said Lintott.
It's not just some dust
There's no way it's just some dust
It was just some dustI think people are misled by all the SF stories with galactic empires that somehow left Earth alone for billions of years, not realizing stories are there to entertain, not reflect what could be real.
We could not get to the nearest star with today's rockets (or eq.), materials, or lifetimes. There's no incremental engineering there.
A star-spanning civilization would have far more than enough energy to propel interstellar vehicles, for example by laser beaming.
I said that implication was false, it's clear how we might build large orbital structures but not clear how we might to interstellar travel. As a counter example.
The barrier to interstellar travel is largely economic(*). The resources needed to construct star-spanning structures are many orders of magnitude greater than needed to construct and launch a starship (or a laser with an aperture capable of projecting a beam to interstellar distances).
(*) https://galileo.phys.virginia.edu/classes/109.jvn.spring00/n...
There's a lot of questions that need to be answered before we can truly answer the question "what does it take to make interstellar travel", and the fact that many boosters for space exploration are glibly ignoring those questions is perhaps the biggest barrier of all.
But materials are improving at a rapid pace. So many orders of scale to co-optimize meta materials. Materials in the future will be magic compared to the limits we have now.
Materials won’t be a barrier to interstellar travel
We are only decades away from being able to do it, for very low mass ships/probes with AI. Long before we will be able to create mega structures
The only reason we don't actually reach out for those technologies right now is that many of us have a religious fear of anything nuclear.
Nuclear rocket engines were already being developed during the cold war.
Both suffer from the irrationality that the more useful they are capable of being, the more they can be misconstrued as orbital weapons.
We could build a 1% c starship using hydrogen bombs. But it wouldn't make much sense to build it, since in the time it would take to get to even the nearest star we'd likely have something much faster.
Sure it's only a difference of a couple of decades at worst between the two but in the context of a human lifetime, that's significant.
If we sent a nuclear craft today, a future laser or other propulsion craft will still get there much sooner.
Worse, we don’t actually have a nuclear craft design. By the time we worked out a design and built it, the other tech will already be ready.
That is because other tech will require less mass, which will “massively” simplify and reduce cost of the venture.
Given the time the trip will take, it will actually be decades at least, before the optimal time to design and send a ship - even if we had an unlimited budget with the only objective of getting there the soonest we can
The energetics of interstellar dust, radiation, the long timelines of travel. It's not clear at all.
One would need to shield against galactic cosmic radiation, but this really isn't much more of a problem than shielding a vehicle in the solar system.
If necessary, parts of this system could be replaced during the journey.
Star spanning structures requires the ability to move mass at scale which requires enormous but diffused in time and space amounts of controlled energy.
Moving between stars requires immense energy focused on a single thing. The amount of acceleration required to any meaningful mass to speed necessary to travel between stars and maintain a coherent civilization is extraordinary and implies many things about the mass being accelerated as well. Most things would simply be crushed instantly, including any organism. The speed of light is also a major impediment as is time dilation, as is the need to decelerate, which require equal and opposite energy away from the destination. Ok - accelerate with large lasers based at home - how do you then stop? You first need to build large lasers both at home and destination. The problems expand, and this only helps for very local travel between close stars.
It’s difficult but plausible with today’s technology scales up to build star spanning structures because they’re built incrementally and the need for near light speed travel doesn’t exist. Further the existence of a star spanning structure might enable interstellar travel, but not intergalactic.
I’d also note that SF is meant to entertain with a story that is possible given some assumptions of progress or hidden nature of reality or small modifications to what is. It’s not meant to be built on magic and other absurdities (not meant as a pejorative!). Many science fiction stories become true and many more will. Often science fiction inspires us to achieve what doesn’t exist today but could. To couch it in something that’s dismissible as say Gandalf the Wizard fighting a Balrog is to greatly underestimate what science fiction is. It’s a roadmap to the future that helps us understand what to avoid on the road.
If you are saying this civilization does its work over very extended periods of time, you're saying they're comfortable with efforts that take centuries or millenia or even longer. That alone makes interstellar travel and colonization much easier; the energy needed scales as the inverse square of the travel time (assuming Isp optimized for the travel time chosen and assuming non-relativistic travel).
We (or they) do not need close to light speed travel for interstellar colonization.
That's like a family from the 1500's committing for their children and 19 following generations to live on a shitty rocket. They'd have just arrived.
I wonder what 500 years of food, water, and oxygen looks like for a civilization-founding crew. What's the backup plan if the target planet isn't livable? Cyanide tablets?
Food and air would be manufactured during the trip. All that's needed is a source of energy. At 1% c, that probably means a nuclear source (or beamed power), but at higher speeds they could simply exploit the energy being deposited by interstellar matter. At 1 proton/cm^3 and .1 c, the power is 22 W/m^2.
Even if this were a robotic terraforming mission, it's hard to see humans committing to the expense of such an endeavor with no payoff for generations to come. Heck, we're reluctant to act to save the planet our lives depend on right now.
- exploration and curiosity
- scarcity at home
- building species level resilience
- interactions with some other species
- escape from local political or other turmoil
All of these are human except for scarcity. The others don’t require sending more than a small vessel. But if you can build stellar scale structures, maybe the value of interstellar travel once the novelty wears off is pretty minimal. And perhaps while your local star neighborhood is only 5 LY away, the next advanced civilization may be thousands away. Without superluminal communications and travel, or at least very close to the speed of light travel, maybe there’s really no such thing as populating the entire galaxy in the time a species is advanced enough to even consider it. Maybe 500 years to travel isn’t extreme (although for humans it feels like an impossibly long time over which to reliably keep social cohesion and purpose), but 10,000 of 100,000 is just absurd.
More likely it's just the Moon than an advance alien space station though.