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Astronomers posit that we live in an area with below average density
- ryandvm 3y agoWe should call it "space"
- ranting-moth 3y agoThe management called. It's too long. They'd like to shorten it to " " to keep it cool with the kids.
- bozhark 3y agoCan _ be copyrighted or trademarked?
- askiiart 3y agoIANAL, but I think you can trademark letters, and that similarly to colors, given the letter is known to correspond to your business in a particular market segment, and with the caveat that the trademark would only apply in that market segment. Theoretically a space/" " is just another character, so maybe. But practically speaking, it would probably be legally filed as "space", and the company's trademark would be on either them naming their company "space", or on them stylizing it as a " ". That's my best guess, at least.
- layer8 3y agoSpace does not imply low(er)-density, void does.
- dylan604 3y agoIt depends on if you are looking at the return type of the object, or what chars it is full of
- gryfft 3y agoDon't say that too loud or somebody will show up and say we should call it "tab."
- LightHugger 3y agotab is less keypresses after all
- adammichaelc 3y agoWhy would distance from earth influence the speed of expansion of a distant galaxy? Does that suggest that our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment?
- deleted 3y ago[deleted]
- 317070 3y ago> our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment In the double slit experiment, the awareness is not influencing the outcome. The act of measuring is. Pretty sure the act of measuring the galactic bodies has no impact on them in any meaningful way.
- I_Am_Nous 3y agoNo, but there is a cool blending of the two concepts when light is bent by large gravity wells so that it actually shows the same star multiple times. When we observe which copied star "produced" a certain photon, it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago.
- rightbyte 3y ago> it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago There is no way to verify that. Big parts of quantum physics is more or less pseudoscience.
- I_Am_Nous 3y agoPerhaps it could be verified using time delayed lensing experiments[1]? 1. https://www.nature.com/articles/s41550-021-01450-9 https://www.nature.com/articles/s41550-021-01450-9
- verisimi 3y agoWithout twerking the laws of gravity, I posit I do not live in a giant void. Am I right?
- NoMoreNicksLeft 3y agoPlease tweak the laws of gravity, but never twerk them.
- asmnzxklopqw 3y ago[flagged]
- TheBlight 3y agoNot an astrophysicist but something like MOND makes sense to me. It seems like it's much more probable that our model is slightly broken vs. there being a massive amount of... well, mass that we can't find no matter how hard we look. Is there something about the idea that's really damning and nonsensical that a lay person may not notice?
- ninkendo 3y agoThe Bullet Cluster is typically touted as the biggest evidence that dark matter is right and MOND is wrong: https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to_dark_matter https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to... Basically, the center of mass in the cluster, and the center of the matter we can see, are way far apart from one another, in a way that ends up being super clear to observe. We can infer the center of mass by the surveying the gravitational lensing we observe, and we can observe the center of the baryonic matter by looking at the x-ray sources. The offset in distance here ends up being pretty clear evidence that most of the mass exists as stuff we can't see (in any wavelength, only via the lensing.)
- ianburrell 3y agoThere are two problems with MOND. One is that it exchanges fine arbitrary parameters of dark matter with the arbitrary parameters of MOND. There isn’t a theory the explains MOND or the parameters. It is just as much of bodge as dark matter. Second is that MOND doesn’t explain all the observations. There are galaxies that have too much or too little gravity. Either MOND varies exactly as we neeed it, or need MOND and dark matter. That isn’t any simpler. It might work if there was theory that explained smaller amount of dark matter and MOND could handle the rest.
- ddellacosta 3y agoThis is a bit of an indirect answer, but I watched this not too long ago and it made it seem clear that MOND doesn't work so well, if not in general at least in the case discussed, which seems pretty damning regardless: https://youtu.be/HlNSvrYygRc?si=6on0pD9_jsed9Dlm https://youtu.be/HlNSvrYygRc?si=6on0pD9_jsed9Dlm I've also heard the bullet cluster pointed out as a strong counterpoint to MOND--I'll let you read the wikipedia page rather than attempting to explain this, poorly: https://en.wikipedia.org/wiki/Bullet_Cluster https://en.wikipedia.org/wiki/Bullet_Cluster As a layman who watches tons of astronomy and physics videos, my general sense is that dark matter is more or less simply a placeholder, such that everything else around it is pretty consistent, but it just represents this unknown matter that we can clearly observe interacting _gravitationally_ with galaxies and other objects in the universe, but otherwise doesn't seem to interact. Whereas my impression of MOND is that it's a set of heuristics that requires a lot of tweaking to work, whereas GR is quite simple and very strongly experimentally verified. But, again, layman
- ranulo 3y agoInteresting solution. I have a theory in my head for years now. It is probably wrong, but here it comes: In an infinite universe the total amount of gravity that affect us in one point in space is defined by the event horizon if we assume that gravity travels with light speed. Every atom in the universe has a very small influence on us. But this event horizon expands with light speed all the time. I wonder if this could lead to very small but permanent increasing gravitational pull from all directions at once. In other words, and increasing inflation.
- I_Am_Nous 3y agoSort of like a pair of ice climbers, where one climbing up and securing themselves allows the other climber to safely climb higher. Eventually we can't see the ice climbers anymore, but that doesn't mean they aren't still helping each other climb higher.
- _boffin_ 3y agoit grow. we grow?
- jprete 3y agoIncreasing gravitational force would result in a contracting universe, not an expanding one, I think.
- pdonis 3y ago"Gravitational force" doesn't work for describing the dynamics of the universe as a whole. What would result in a contracting universe is a large enough density of matter (about a factor of 20 larger than the actual density in our universe if we just look at ordinary visible matter). But this does not mean "increasing gravitational force". As I have pointed out in other posts upthread, the "gravitational force" on a given piece of matter due to the rest of the matter in the universe (if we leave out local influences, like our solar system or galaxy for us here on Earth) is zero. This is true regardless of the current state of expansion or contraction.
- yodon 3y ago
- gumballindie 3y agoI dont know why but my mind enters an endless loop when thinking about the vastness of space and where that space exists. Almost as if it reaches the end of human imagination. I can imagine the multiverse, but i cant imagine the “nothingness” in which they exist. I cant imagine where everything came from and where it goes. It makes no sense. I understand the explanation of physics and time, the big bang, expansion, but where the heck does it all exist in? The void of what? What are they expanding into? I understand matter existing in the universe, but where is the universe expanding in? What are the laws of that “in”? That void exists in something but what does the something exist in? It’s almost as weird as if nothing ever existed yet it exists.
- tux3 3y agoIt is not expanding inside of something. The picture I've been given is living on the surface of a balloon. Draw a few dots on the surface, blow in the balloon. Every points expands away from every other point. Of course with a balloon there is always an outside, but the point is that it isn't expanding like if it were pushing against an external wall. It's expanding everywhere. It's expanding in the space between your fingers. If you look there, it's not pushing against any outside. There is just more space per space, the longer you let it age.
- ninkendo 3y ago> It's expanding in the space between your fingers That's not the case (at least not yet [0].) Anything that's bound together by local forces such as gravity or electromagnetism isn't affected by the universe's expansion. You have to get to the scale of the space between galaxies (and even then, galaxies which aren't orbiting/colliding with one another) before the expansion has any effect. [0] One of the hypotheses (of many: https://en.wikipedia.org/wiki/Future_of_an_expanding_universe https://en.wikipedia.org/wiki/Future_of_an_expanding_univers...) of the future of the expanding universe predicts that the expansion rate will increase indefinitely, do the point where the expansion energy (dark energy) actually does become enough to expand the space between stars, planets, and even matter (and eventually the atoms in your body), but we don't really have any proof of this. This theory is known as the "big rip": https://en.wikipedia.org/wiki/Big_Rip https://en.wikipedia.org/wiki/Big_Rip
- PcChip 3y agoFYI their definition of “void” is “slightly below average density”
- nuz 3y ago"Slightly" can mean such gigantic numbers still on this scale. Still interesting if this is the case
- 1270018080 3y agoBut then back to human scale it's only a few less hydrogen atoms per cubic meter.
- dang 3y agoThanks—I've replaced the void with that in the title above.
- hprotagonist 3y agoBut apparently we don’t live in a void, we live in a big glob of higher density galaxies, the Laniakea supercluster. https://arxiv.org/pdf/2311.00215.pdf https://arxiv.org/pdf/2311.00215.pdf MOND hasn’t been having the rosiest of time lately. https://academic.oup.com/mnras/article/527/3/4573/7342478?login=false https://academic.oup.com/mnras/article/527/3/4573/7342478?lo...
- due-rr 3y agoDr. Becky has a nice explainer video of the first paper. https://youtu.be/-kTe0xRAU1w https://youtu.be/-kTe0xRAU1w
- OnACoffeeBreak 3y agoDoesn't sound like the paper's (the one you linked) authors don't necessarily agree with your summary. From the discussion on page 16: These results seemingly worsen the recently established tension between the inferred value of H0 from early and late times Universe probes, which has been argued to potentially be the sign of new cosmological physics (see for example Refs. [78–83]). This might appear to be in contradiction with the possibility, explored for example in Refs. [74, 84– 93], that local gravitational physics could alleviate the Hubble tension. Amongst these, a class of models achieve a lowering of H0 under the assumption that we live in an underdense region, whose inner expansion rate is on average larger than the background one. Some results in the literature, see for example refs. [94–96], seem to corroborate the latter assumption finding evidence of local voids which averaged on spheres of r ≳ 100Mpc have density contrasts of δ ≤ −0.1, unexpected within the ΛCDM model. Computing the average density contrast of a sphere centered in Laniakea with radius r ≈ 110 Mpc (i.e. the average distance of the boundary of the ellipsoid from the center) using the CF4 reconstruction we found δ ∼ −0.06, within the prediction of the concordance model (see for example Fig. 6 of Ref. [55]). However, this sphere is not centered in the Milky Way, which might explain why the result differs from the aforementioned ones. Indeed, overdensities such as Laniakea are surrounded by voids (from which they have collected matter), and therefore any sufficiently spherical average will include these under-dense regions. On the other hand, Refs. [55, 79, 97] also found no evidence of any large void or overdensity, thus disfavoring a local resolution of the Hubble tension. Our analysis corroborates these results, suggesting instead that the tension is likely to be (slightly) worsened by Laniakea’s backreaction. An important caveat, however, is that our analysis does not exclude the possibility that large voids in the annular region between 110 − 400 Mpc outside Laniakea could balance and overcome the backreaction from Laniakea, like a rather picturesque Matryoshka doll. Alternative modelling choices accounting for the impact of these voids are therefore required to fully understand the impact our cosmic environment’s gravitational backreaction, which will be the focus of forthcoming studies.
- snoopsnopp 3y ago[dead]
- ReptileMan 3y agoQuestion - what are the conditions in the denser parts of the universe for earth style life?
- layer8 3y agoAt the mentioned 25% higher density, probably no significant difference.
- jacobwilliamroy 3y agoSometimes I think about how everything Ive ever known is a tiny invisible spot on a little wet rock hurtling through an empty nightmare abyss.
- ptsneves 3y agoI read that sentence as poetry. Beautiful.
- d0mine 3y ago"Pale Blue Dot" https://youtu.be/nl5dlbCh8lY https://youtu.be/nl5dlbCh8lY
- wholinator2 3y agoI do disagree with nightmare, but it's all in perspective. More like an infinitely deep well of incomprehensible potential to me. Deep water is scary but a well is life giving. It's a little bit of both
- mojomark 3y agoWhile we're all throwing out our whacky idea laundry in front of people I presume actually know what they're talking about: I've wondered for many years if our universe isn't like a supersaturated (SS) solution (1), where mass/energy and the fabric of space-time itself can eventually combine and settle into a balanced but very precarious state, like an SS solution comprised of Mass-Energy-Space-Time [MEST] as a single "fabric" (which perhaps was the state of the universe prior to the big bang, and will be again after the universe' heat death). Say this large swath of peaceful-yet-highly unstable MEST fabric is perturbed slightly (like dropping a seed crystal in a SS solution) - then matter, energy space and time precipitate outward in a rapidly evolving chain reaction. The horizon of this chain reaction would be a place where matter and energy particles are continually being generated (liberated) from the serene METS fabric, which generates a gravitational pull in all directions. So, all of the mass in our universe is actually being pulled outward, and because this precipitation horizon is expanding (growing in surface area), it generates an increasing amount of matter and hence an increasing amount of gravity that ultimately pulls matter within this horizon outward - at an accelerated rate. Perhaps the big bang was really, instead, a 'big fizz' - chain reaction of precipitated matter and energy from an initial supersaturated MEST fabric. Or maybe I'm just full of silly nonsense. Either way, would love to hear an actual astrophysicist 's take on that idea. Maybe gently tear it to shreds:) 1. https://youtu.be/G8nHu-IOpTg?feature=shared https://youtu.be/G8nHu-IOpTg?feature=shared
- ganzuul 3y agoSeems like you are picking up on the intuition of cosmic inflation of quark gluon plasma. The degenerate matter state is like a partial order of time. https://en.wikipedia.org/wiki/Causal_sets https://en.wikipedia.org/wiki/Causal_sets
- wiml 3y agoThe first part of your idea sounds a lot like a false vacuum decay which is metaphorically a lot like a supersaturated solution.
- Finnucane 3y agoBecause of galactic-scale NIMBY zoning.
- immersible 3y agoThis article starts from an infinity of axioms that all have to be true for that single statement of the title to have even a small chance of making sense. It is a purely speculative article.
- ngcc_hk 3y agoI listen to this before seeing this post: https://www.youtube.com/watch?v=-kTe0xRAU1w https://www.youtube.com/watch?v=-kTe0xRAU1w Seems more concerns about the issue of cosmological constant and its disagreement with observation and current model.