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Biggest void in space is 1B light years across (2007)
- generalizations 6y agoPosted it because it reminds me of an hypothesis I once saw, that we might be able to detect alien civilizations based on blank spots in the sky where they've managed to divert all the energy from their environment.
- agentwiggles 6y agoI'm reminded of the Three Body Problem series, where there's this concept of a Black Domain - an area of space in which the speed of light has been reduced drastically. Some civilizations in the setting have reason to deliberately construct these areas of space. (The reasoning behind this might be considered a spoiler, so I'll leave it off.)
- ethbr0 6y agoYou mean like in Vernor Vinge's 1992 A Fire Upon the Deep?
- harshreality 6y agoSounds similar (I still need to read Liu), but in Vinge, it wasn't light speed being reduced, it was a variety of limitations on superluminal physics, computation/intelligence, and maybe even physical properties. (variations in quantum physics, perhaps)
- elihu 6y agoSort of. In Vinge's world, the slow zone is just a natural phenomenon, not something artificially created. And in the slow zone you're basically limited to nearly-speed-of-light travel consistent with our contemporary understanding of relativistic physics (which is unbearably slow to anyone who can travel much faster than that outside the slow zone). Whereas in Liu Cixin's books, if I remember correctly, they actually change the speed of light itself to be even slower.
- dnhz 6y agoIf I remember correctly, there's some ambiguity whether the slow zone was created by some power or naturally occurring (or a bit of both) although a bit of both is perhaps the natural answer.
- elihu 6y agoYou may be right; it's been a long time since I read A Fire upon the Deep or A Deepness in the Sky.
- ethbr0 6y agoI remember some insinuations to that effect, but from an unreliable narrator given Vinge's penchant for strictly in-character exposition, and what would child races know of progenitor's motives? 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.
- klingon78 6y agoIt might not be as empty as it looks. Maybe it’s just got a really big dark sheet over it. Astronomers don’t consider the possibility of ginormous dark sheets in space.
- wideareanetwork 6y agoProbably more in the domain of god - if you believe in that sort of thing - than aliens.
- edgyquant 6y agoAt that level what’s the difference?
- nynx 6y agoI've heard this idea in the context of Dyson spheres/swarms. The issue is that, while they'd be invisible or dim to the eye, the areas would be very bright in infrared.
- Retric 6y agoDepends on how large the swarm is. Using our sun as the example a 1AU swarm would be very warm, but at 100 AU it would be extremely cold and much harder to detect. 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.
- vermilingua 6y agoFossil fuels vs solar, it’s a sustainability question. Plus, dismantling a sun isn’t much help to the planets orbiting it, and then you need to find a way to efficiently get that energy to another system to be used.
- m4rtink 6y agoPlanets ? Who cares about planets when building a Dyson swarm - other the possibly as a bootstrap cache of materials to get thing going. 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.
- Retric 6y agoThe amount of fuel is fixed either way so it’s an efficiency question. Normal stars only burn a small percentage of their fuel. Maximum energy is captured by turning hydrogen into lead. After that, dumping lead into a deep gravity well is the final option.
- Konohamaru 6y ago> 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. Would like a referral to science fiction that talks about this.
- suifbwish 6y agoWhy would we presume they would not think to generate a cloaked for this if they had the ability to divert all energy from their environment? Seems an obvious first order of business to avoid looking like an anomaly if you are not actively trying to be found.
- edgyquant 6y agoHow would you cloak waste heat?
- suifbwish 6y agoWhat makes us so sure waste heat is something that is absolutely unavoidable. It’s possible heat maybe be disposable through some quantum means we have not uncovered yet. Ultimately everything in existence has heat potential so theoretically heat is able to covert back to everything else . Using no heat as proof the room is empty is equivalent of a person who cannot avoid making a mess when they enter a house concluding that no one else has been there because there is no mess (except the one they made) all they can conclude is that no one who makes a mess has been there.
- wideareanetwork 6y agoVoids aren’t empty they just have less stuff in them. There’s galaxies and things in there.
- galacticaactual 6y agoSometimes I wonder about the percentage of HN commenters who actually read the article. Literally a few paragraphs in: “The lack of radio sources means that there are no galaxies or clusters in that volume.”
- 6gvONxR4sf7o 6y agoThis morning, on an article about 'fuck-you money' there was a discussion about where the term comes from. The 1990s? The 2000s? The first paragraph of the article dated it back to at least the 1920s.
- JoBrad 6y agoSee, I was prepared to downvote the comment. But then you commented, and someone else did, too. So, they actually did spark conversation. Now I have to upvote, I guess. /s (just in case)
- mensetmanusman 6y agoI think it’s pretty low, but that’s because the comments are usually more interesting.
- edgyquant 6y agoI usually click on the comments, if an article seems interesting I’ll see if the comments say it’s bad etc before clicking but even articles I’m not interested in but have an interesting topic I’ll click through to read the comments. 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.
- wrwatson 6y ago
- mmazing 6y agoImagine being a civilization on the edge of a galaxy on the edge of the void. One direction, nothing whatsoever. The other direction, billions upon billions of galaxies. Would be neat!
- dencodev 6y agoI would be curious to hear if the odds of life existing on the edges of the universe were lower.
- animal531 6y agoIt should be the other way around. When everything is packed closer together you are far more likely to fall victim to supernovas, more asteroids and so on that can end life on your planet.
- phaedrus 6y agoImagine being a civilization alone in the void, and not even a generation ship could make contact with anyone else, even if they knew which direction to send it.
- sharkweek 6y agoSounds like you have a sci-fi novel to write!
- Covzire 6y ago> The void, which is nearly a billion light years across, is empty of both normal matter and dark matter. The finding challenges theories of large-scale structure formation in the universe. How do they know or believe that it doesn't contain dark matter?
- sicher 6y ago”The lack of radio sources means that there are no galaxies or clusters in that volume, and the fact that the CMB is cold there suggests the region lacks dark matter, too.”
- Covzire 6y agoInteresting inference, to make it we have to hypothesize that dark matter has an effect on the CMB in the first place, is that at least somewhat backed up by any observations?
- raattgift 6y agoThe small fluctuations in the CMB that WMAP detected (the 2007 article being about the "WMAP Cold Spot") are sensitive to the distribution of all matter -- including dark matter -- in the early universe. 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 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). - -- [1] https://en.wikipedia.org/wiki/Decoupling_(cosmology) https://en.wikipedia.org/wiki/Decoupling_(cosmology)
- junippor 6y ago2007 was already 14 years ago. We don't even know if this is still there.