Biggest void in space is 1B light years across (2007)
newscientist.com
newscientist.com
One direction, nothing whatsoever.
The other direction, billions upon billions of galaxies.
Would be neat!
Paints a bleak picture of a civilization in this situation. Great book though.
Thanks !
[0] https://en.wikipedia.org/wiki/Giant_Void
https://www.zmescience.com/space/the-local-void-mapped-04322...
https://en.wikipedia.org/wiki/NGC_6503
Two tiny dwarf galaxies are in the process of leaving the Local Void due to the attraction of the galaxies surrounding it:
https://www.space.com/33748-dwarf-galaxies-escape-cosmic-voi...
The universe will expand so much that civilizations into the VERY distant future will not be able to see other stars and galaxies, and will have no way to know that there's more out there.
It's quite sad actually.
https://en.wikipedia.org/wiki/Local_Void
* 1 megaparsec = 3.26 million light years
As a universe arrangement scheme (both narratively and literally), it is a clean solution to providing a new race incubator and preventing "Why don't the First Ones rule everyone?" endgames.
Really though, a Dyson’s swarm isn’t that efficient long term. It’s likely better to dismantle large stars and use fusion reactors with heat sinks at close to 2.73 Kelvin as possible.
Yeah, you might occasionally leave one in place for historical reasons, but otherwise they are just too useless not to make use of their mass for something better. Not to mention traffic management headaches given that normal planets usually stubbornly refuse to do any orbit corrections when needed.
Would like a referral to science fiction that talks about this.
Also used in many places in Orions Arm: https://www.orionsarm.com/eg-article/47897e8b1947c
Whole star system optimized into a giant computing cluster with projected sun energy output for computing available for next 14 trillion years: https://orionsarm.com/eg-article/49125f5d1c049 (Or 100000 sun output for 140 milion years.)
Himmelsschmiede - a full star system converted to useful heavy elements using a deep well industrial zone (basically an artificial black hole accreation disk): https://www.orionsarm.com/eg-article/46709da5de6be
Any space-faring culture will have mastered controlled fusion long ago, and have entirely left behind any material dependence on stars. The best places to live, then, are out in the Kuiper belts and beyond, where unlimited room and cold are available for free, and valuable gases are lying about, frozen. Inner planets are for extreme primitives. If aliens got here, they would find Triton much more interesting than Earth, except maybe as a curiosity.
Expanding menace civilizations will run up against overwhelmingly more advanced stable cultures before long and be contained or destroyed, so odds are none could get here before that happens.
Kuiper belt distances are inconvenient only when you are in a hurry and have limited speeds. Given fusion propulsion, nothing inside a solar system is especially far from anything else. But a large volume to operate in, which grows as r^3, is valuable, and an unlimited sink of cold, moreso.
If you need more mass, Neptune is right there.
Or, maybe you are robots, and can take 100G. Then the Oort cloud is your playground.
This seems like an interesting thought experiment care to expand on that?
When an expanding menace tries to absorb the ancient stable culture, it has key disadvantages. Its attention is spread over activities on a large periphery, and its stores of knowledge and weaponry are limited. The ancient culture has been found by many menaces before, and survived them all. It knows of other old, stable societies, and they may even have evolved a common plan for dealing with menaces.
It is conceivable that the expanding menace would try to flow around the old stable societies, like a river around rocks, without threatening them enough to provoke a backlash, but that runs against the logic of expansion.
So, odds are any expanding menace will encounter one of them, or more than one, if needed, before it gets to us. Each such encounter will be an existential challenge at bad odds, which multiply out increasingly close to zero.
Thus, the stable condition of a galaxy is a sparsely occupied archipelago of deeply ancient, unassailable cultures not interested in expansion, so not visiting, e.g., us, with the occasional rash of menace, dealt with firmly.
As you adjust down you could trivially and likely have tens of light years between cultures or even hundreds on average if intelligent cultures are short lived or particularly rare. Expanding menaces could be automated and self replicating and designed to create an expanding zone of safety for an old stable society in a way that isn't easily traceable to the old stable society.
It's young because it's expanding. To first order, divide the radius by the rate of expansion and you get when it started. The society that bides its time for millions of years and then turns menace does not pass the smell test. Every year they go without menacing, the less likely they ever will.
Anyway, whoever's (1) inside the perimeter, (2) is a bad trading partner, and (3) not burnt is a pretty good bet for who's responsible. If there are two plausible candidates, they are better both dealt with.
It's also true that they don't last long because of conflict, but that's secondary.
A sorcerer's apprentice scenario is conceivable only in the short term. To maintain expansion demands adaptation to an increasing variety of new challenges, whose variety and strength increase as the fourth power of expansion radius. (Three dimensions for space, one for age of opponent.)
One can invent myriad obscure scenarios, of decreasing likelihood. It's a big universe, rashes happen, but it's a big universe, so they mostly happen somewhere else.
Stable societies that stick to their own region while prioritizing research ('growing tall' is the name for the strategy) tend to win out in battles against those that 'grow wide', grabbing all resources and expanding into them with little regard to research and personal affairs.
Those that 'grow wide' tend to win the games through simple attrition on a long time-span at the end-game phase. Simple resource volume tends to be able to win against vastly superior forces, much like a StarCraft 'zerg-rush', and the superior force usually loses in a 'death by a thousand cuts' fashion -- but individual battles before this phase of the end-game are almost exclusively won by small civilizations that 'grow tall', much like the 'stable culture' of your example.
The 'Growing Tall' strategy tends to be the one chosen by players who like to end games early and play aggressively against the other players -- contrary to the sedentary and passive method of play that the strategy facilitates.
It seems like being equipped to, say, cause a solar flare to sterilize an offending planet would tend to discourage an aggressor before their ships got used up. Probably a flare wiping out a neighboring planet (e.g. one like Venus) first would convey the message adequately.
Stars provide in abundance and for free, energy, mass (even for heavier elements they far outstrip that available on planets, asteroids, and comets), a star system spanning magnetosphere for protection from the interstellar medium, and a massive gravity well which can be used to anchor planets and mega structures alike
While it's true that we won't strictly "need" them once we have working fusion, they are likely to be the hotspots of civilisation for a long time to come, probably as long as the stellar epoch of the universe is in play (so 100+ billion years).
For most high-civilization activities, heat is pollution, something that must be extracted and shed, in volume. Out in the Kuiper belt, cold is abundant and free.
For most high-civilization activities, a gravity well is an anchor chain. Out in the Kuiper belt, material resources, including frozen fusible gases, are abundantly accessible with very little annoying gravitation.
For many high-civiliation activities, proximity of other entities that could be put at risk, or that might put you at risk, creates hazards. Out in the Kuiper belt, room enough for anything is abundant and free.
Extreme primitives like us and bacteria, who don't have abundant private energy sources, welcome the low-intensity energy influx from a nearby star. For anybody even mildly sophisticated, the energy is uselessly diffuse. At the same time, it keeps everything at a noisily high temperature that interferes with signal integrity and fine-grained processing.
* It is possible to export or even host consciousness onto a digital medium - we still have no evidence for this
* All or most civilisations ultimately will want to transition entirely into a digital existence - the "entirely" part is important. If even 1% of a K-2 civilisation decided to stay organic, that would still lead to a Dyson swarm with a population approaching trillions.
* Civilisations of this tech level would do a cost benefit analysis and decide that the several orders of magnitude more resources on a star is outweighed by the inconvenience of a gravity well - I don't think orbital rings are that mass or energy intensive to build and run for this to make any sense
* There will be no future use of waste heat or method of disposal that goes beyond simple dispersal - the jury is still out on that, it may be possible to dispose of waste heat directly onto a black hole. If this turns out to be correct, the energy of a star is more than enough to power a sufficiently powerful laser array to create many in the gigatonne range.
There’s galaxies and things in there.
/s (just in case)
This one, for instance, I’ll admit I haven’t clicked through to the article. I’ve long been interested in these voids so I didn’t figure the article would relay any information I wasn’t aware of so I clicked through to see what people here had to say.
Perhaps Dang could get analytics on how many people viewed the comments and how many people clicked through to the article to answer your question.
"an immense, comparatively empty region of space...proposed to be roughly spherical, approximately 2 billion light-years in diameter. As other voids, it is not completely empty but contains the Milky Way, the Local Group, and a larger part of the Laniakea Supercluster. The Milky Way is within a few hundred million light-years of the void's center."
A void has by "working definition" "less than one tenth of the average density of matter abundance that is considered typical for the observable universe."
Tracing out how the very earliest structures in the CMB compare with much more recent galaxy filaments (and the voids between the dense filaments) is an interesting area of research, and there will be open questions for many years to come as galaxy surveys at different redshifts produce observational data.
(All the galaxies will be at a lower redshift than the CMB cold spot, and it is a good guess that the CMB cold spot reflects an arrangement of matter much closer to the hot big bang or cosmic inflation than that. Perhaps one day our descendants will be able to examine the cosmic neutrino background to see if it too has a comparable cold spot, and the same with primordial gravitational radiation; alternatively perhaps they will discover that later-time physics distorted the CMB very slightly. The latter hypotheses are in practice much easier to test with observational data, and of course one can exploit the many unknowns in the dark matter and dark energy sectors without colliding with constraints from known physics.)
How do they know or believe that it doesn't contain dark matter?
Roughly, hot spots have more matter, get hotter as that matter collapses into stars, hot gasses, and eventually black holes; cold spots have less matter, and because of the expansion they get colder, sparser, much bigger, and eventually become practically empty.
Early pockets of dark matter overdensity, similarly roughly, helps turn on the heat very early, and keeps the heat turned on longer than otherwise. Early pockets of dark matter underdensity makes it much harder for stars to light up in the first place.
Generally one simulates the introduction of non-uniformities in this distribution during Cosmic Inflation, and then the overdense areas collapse while the underdense areas experience the cosmological constant. At the time the universe has expanded enough that photons can free-stream (this marks the beginning of the CMB, see [1]) the density-differences in one part of the universe to another are very small, but over billions of years the collapsing dense regions become ever denser (and form stars and galaxies) while sparser regions simply become colder. (Both become emptier, relatively; collapsing a diffuse cloud into a dense cloud leaves behind a lot of space emptier than when the diffuse cloud was populating it).
Dark matter plays a crucial role here, because it collapses more slowly than visible matter by forming haloes and other structures, essentially suspending visible matter (gas) above the cores of galaxy clusters (where in later times you find really gargantuan black holes). It is also important that its underdensities and overdensities after Cosmic Inflation were roughly the same as that of what became the particles of the standard model, and it is this feature that appears to be crucial to structure formation : https://map.gsfc.nasa.gov/universe/bb_cosmo_struct.html
However, once the CMB has formed, those photons no longer interact appreciably with the dark matter of the universe -- the gravitational interaction is weak and gets weaker with the expansion of the universe.
So it is the early distribution of dark matter (before atoms, before protons) that is important in creating CMB cold and hot spots.
It would be odd to have a hot spot become anything but a matter structure (galaxy cluster) because of gravitational collapse. Likewise, it would be odd to have a VERY cold spot become anything but filled with a very sparse gas (e.g. hydrogen + photons + neutrinos). The WMAP Cold Spot is not THAT cold and so could have structures like galaxy clusters in it, but fewer of them than than in the filamentary structures. Indeed, we may live in someone else's cold spot. Galaxy surveys are trying to gather up evidence one way or another for the densities of galaxies and their ages along various lines of sight from here, which will help us determine how well WMAP cold and hot spots line up with galaxies. ALL galaxies are much more recent than the CMB.
Several ideas about how the WMAP Cold Spot could have been a WMAP Average Spot at the time the CMB was formed, but that (mostly new physics) events in the more modern universe present us with a relative cold spot. Some of these have the virtue that these more modern events are more amenable to study with our current level of technology than the distribution of gravitational waves after cosmic inflation and the detailed study of the cosmic neutrino background (which is similar to the cosmic microwave background, and so should have similar small temperature fluctuations; but measuring ultracold neutrinos is not something we can do today, nor can we yet look at the frequencies and amplitudes of primordial gravitational waves, however there may be indirect probes of both available before our descendants are able to observe them directly).
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The https://en.wikipedia.org/wiki/Axis_of_evil_(cosmology) is a pretty curious thing, but I think the safest bet is a combination of randomness and https://en.wikipedia.org/wiki/Pareidolia .