Does it mean that we are, potentially, on one of two poles(?) of the observable universe, if we're observing most galaxies around us rotating a certain way?
It would also imply that our whole universe is rotating - the only reason this happens on Earth is because of our planets rotation and the Coriolis effect.
I think there is a men in black scene, where an alien is rotating the universe globe like a toy they are playing.
While we don't believe we're the center of the universe, I believe we're limited by instrumentation to determine its size. Best guess now is 100B LY in diameter.
But the observable universe is a fraction of the whole thing. The "best guess" right now is that the total universe is flat and has no end.
If it's bounded, 100B LY is orders of magnitude below the most conservative lower-bound estimates, which I believe start at around 300-500x that size. (With huge error bars on all sides.)
I think in general it would be unusual if they didn’t rotate. Any large non-uniform mass of gas or rocks when colliding will induce some rotation. What is odd though is that for galaxies we see more of them spinning one way than another.
Would that be same kind of question as “where did the Big Bang come from?”. That’s a lot of energy that came from somewhere as well seemingly for no good reason.
I also wondered immediately about dark matter; could it be that’s where the counter-balance of momentum went? Like most galaxies spin one way and most dark matter would then have to spin the opposite way.
I am not a physicist so this is all random guessing of course.
That seems like an example of "streetlight effect." The streetlight effect, or the drunkard's search principle, is a type of observational bias that occurs when people only search for something where it is easiest to look.
Pardon the cheesy domain name, the content is very relevant.
Maybe there is an 'incentive' for universes to form with physical constants tuned to produce black holes with the available energy in that universe.
You can say the exact same thing about mass. Obviously it came from somewhere. And it could have taken angular momentum with it.
[^]: Ignoring ejections. But black holes also don’t “eject” mass. Or maybe they do? Hawking Radiation is weird.
The important part is that at any given point on the elastic strip, both sides are getting further away. Everything else is getting further away.
You might think if A-B-C-D are points on the tape and A-B are expanding and C-D are expanding, then B and C must be squished together, but the distance between them is also expanding. You have infinite elastic, but you also have infinite room to stretch it (even along the direction it already occupies). You now have A--B--C--D.
It's tempting to think about that stretch from the point of view of the floor/table beneath the elastic, in which case some parts of the elastic move faster than others as they stretch, but if you always think from a point on the elastic, then the speed of the rest of the elastic depends on how far away it is. Stuff twice as far away moves away twice as fast. Stuff infinitely far away moves away infinitely fast. That's true for every point on the elastic. No bunching up.
I never finished the book, but this reminds me of God's Debris by Scott Adams which explores a philosophy of pandeism (where God annihilated itself and became the universe).
In other words, your observable universe is different than mine and that's both spheres we're in the middle of. That suggests the universe itself probably isn't a sphere.
The observable universe is the only true sphere.
The observable universe is expanding into the unobservable universe.
What would be interesting is to run a diff on the cosmic microwave background and the pictures from the James Webb space telescope to figure out where the true centre of the universe is, and derive the poles from there.
But then, what is the universe? One way to think of it is to imagine that every galaxy has at least one intelligent species with their own observable universe. The universe is the sum of all observable universes. The very nature of how to sum them together, what it means to combine multiple sets of thing which include items that don't exist relative to other items in the set, is a question we can't really answer yet. Because of this, even a question like the size of the universe is unknown, and even the question of if more of the universe exists outside of the observable universe isn't simple to answer and gets into the nature of what it means to exist. If someone exists in the universe, but not in the observable universe, it becomes an instance of Russell's Teapot.
https://cds.cern.ch/images/CERN-HOMEWEB-PHO-2022-023-1
Observing the edge is effectively looking back in time, to see the conditions of the universe closer to the time of the Big Bang.
New telescopes keep expanding that edge, and new particle colliders (such as those at CERN or Fermilab) keep "bashing 2 rocks together to make fire" - recreating the conditions of the Big Bang to see what comes off.
What I'm not sure about is whether the speed of light (assumed to be constant) is correlated with the size of the observable universe. Perhaps a physicist could shed some light on that question. Relativity means that galaxies that are moving at the speed of light away from one another (one travelling at c, another travelling at -c) have a relative velocity of higher than the speed of light (|c| + |-c| = 2c).
There's also the theory of the One Electron Universe, which I quite like (though that reveals my bias as an electronic systems engineer). Perhaps what we see is the One photon universe. https://en.wikipedia.org/wiki/One-electron_universe
Hopefully this rambling makes sense to someone!
There are ongoing debates whether the actual Entire Universe is infinite or not.
That said: I'd wait a bit here. This is a single-author paper by a non-astronomer (he's a CS professor). The sample size seems small (N=263), and the measurement coarse (he's just bucketing galaxies into "rotating in the same/different direction as the Milky Way"). And the technique may be too novel for its own good. The gold standard here would be to look at differential redshift, but all he's doing is applying a ML filter to detect the "twirl" direction in the image of the spiral galaxy. Which... might be amazingly effective or might fall on its face because of bugs in the filter.
But the signal seems strong, though (158 vs. 105 galaxies in each direction).
Basically, I'd wait a bit for someone to try to replicate with more data and more conventional measurements.
The question starts to become very philosophical if there is a backup system for this universe. Everything being saved, for eternity, in infinite time. It would require very advanced computational power and storage, but it would probably work in binary (but that's just the kind of thing a computer engineer would say).
Maybe, though, the observable universe is rotating clockwise around a centre that is in the unobservable universe, and time is just a measure of how many rotations have been made since the Big Bang.
The equation is on Wikipedia. https://en.wikipedia.org/wiki/Lorentz_factor
The terms are: v is the relative velocity between inertial reference frames, c is the speed of light in vacuum, β is the ratio of v to c, t is coordinate time, τ is the proper time for an observer (measuring time intervals in the observer's own frame).
If we could compare the time as we know it (based on the SI unit of seconds using an atomic clock) against the time at the singularity at the centre of the universe, we could figure out whether we're in a black hole, whether we're at the event horizon, or whether we're outside.
But we would have to assume space is a vacuum, which isn't entirely true.
Trying to see beyond the edge would be like trying to peer out of a black hole. It would probably look blue, like Cherenkov radiation. (but I'm biased, due to having blue eyes).
If the Entire Universe is infinite, then it's eternal in time. And then we get philosophical again.
While I agree with your correction and this always bugs me, the common usage of the phrase "begs the question" seems to have become synonymous with "raises the question", as opposed to what I understand to be its former — and perhaps original — meaning which was associated with the informal logical fallacy by the same name.
And yes, I'm familiar with Dawkins' famous retort when someone asked how magnets repel things.
I don't think the universe is considered to have any significant rotation, however. Is this due to scale for us to measure, and/or having nothing external to compare against?
But there is no reason to think that the universe has a net rotation. It could have one; you don't need a frame of reference to detect rotation. (The same way you feel centrifugal force.)
It would be huge if it were shown to have a net rotation. So huge that I take this claim with skepticism until heavily confirmed.
But what could possibly happen other than they act like all other physical objects do? It boggles the mind to think how broken physics would have to be to accommodate a second correspondence principle for the big-but-not-too-big scale...
I feel like maybe I'm misunderstanding your sentiment, because this seems like a basic shared fact: a clock anywhere in the universe is still a clock.
So it’s a similar question. Where does this asymmetry come from.
"We conclude that the hemispherical power asymmetry still remains as a challenge to the standard model." [1]
The density makes the scale recursion less mysterious.
The visible universe is redshifted and galaxies are getting further and further away. So jumping straight to “we are in a black hole” is weird
It is far more plausible that there is some coriolis like spinning effect in a higher dimension, even if the universe is flat it could have similar effects to how the earth’s spin makes cyclones all spin in the same direction.
Problem solved. Next?
Just because something is untestable today doesn’t mean it will be for all time. However, the untestability problem has started to creep much more deeply into cosmology and high particle physics in particular - our technology and models aren’t staying enough ahead to provide a lot of fertile testable ground.
Similarly, the dynamical spacetime around a black hole not near any other black hole can couple with quantum fields -- even fields in a no-particle "vacuum" state as measured by an observer, for example one in orbit around the black hole -- with the result that Hawking radiation is produced.
Both gravitational radiation and Hawking radiation carry away energy (in the sense of ability to do work, per the "sticky bead" argument) from the environment immediately around a black hole. This in turn means that the horizon radius will be less than it could be.
So as a Hawking-radiating isolated black hole will tend to shrink (if it's not fed by hotter cosmic microwave background radiation, for example), the mass of a post-merger binary black hole will be less than the sum of the unmerged binary.
Just because things can't cross from the inside of a black hole horizon to the outside doesn't mean the horizon is always the same -- the horizon can grow and shrink dynamically when interacting with other self-gravitating bodies, with matter like dust or starlight, or with "the quantum vacuum".
I'm not. I was unable to substantiate that anyone named Dawkins, Richard or otherwise, made or is popularly associated with a comment about magnets. What was the retort?
We can say that any particle inside the horizon is inevitably headed to the center. (That's why we can't say any more: no other information can escape.) That does lead to a problem in that all of the mass would be concentrated at a single point at the center, whose density is division-by-zero.
But I wouldn't put too much weight on that. We already know from quantum mechanics that there isn't really any such thing as a "point". The math is still a problem, but the solution almost certainly lies in that direction.
This is generally true, but such ideas are kept outside the realm of science until they are. In this case specifically, all our knowledge points to this remaining untestable as it would require FTL travel which is on par with violating conservation of energy or time travel. It even allows solving the halting problem (Turing machine in timeloop until it halts, you outside of the timeloop can then check if the Turing machine in the timeloop ever left it).
It is entirely possible that there are things which are true which science cannot verify because of the underlying philosophy by which science operates. Things that exist outside of the observable universe, if FTL travel is truly impossible, would fall outside the realm of science.
>The mere fact that two observers have different observable universes indicates it is indeed an illusory artifact.
Do they? The nature of the observable universe is that, if you can communicate with someone else, any information they can receive and pass on to you is part of your observable universe as all information travels at the speed of light or slower. If they can receive information and cannot pass it on to you, they are not part of your observable universe any longer and no longer exist (exception if FTL interactions are discovered). Thus the only observers that exist in a way you can interact with, can make any testable hypothesis concerning, and thus can be considered by science, are observers in your observable universe.
The observable universe is defined as natural light reaching us. It says nothing about repeaters. If someone id at the edge of your observable universe they could still send you a message. They’re observable universe would necessarily include light that wouldn’t reach you due to expansion. Of course, it is possible we’re within a black hole or some other weird space time geometry in which the universe folds in on itself in which case it is possible the observable universe is the universe. I’m not saying that’s impossible since we don’t know. I’m simply stating my Bayesian priors based on my understanding of the evidence collected so far about the CMB and what it and the theoretical models we have suggest. It doesn’t make other theories less valid, it just means where I’d make a wager if I had to. As you say, right now it’s not capable of being a scientific theory and it’s a stretch to even be called a hypothesis.
Still, this is just a reversion to our natural state where we have philosophical ideas grounded in the best knowledge we have trying to find ways to unlock the secrets, not unlike ancient Greeks. We might succeed or we might not but I still think it’s a scientific pursuit grounded in the scientific method in some way. For example, we have no way of really confirming whether our models are correct about estimating the distance to stars. Still, we think it’s true enough because it works locally. Science is and always has been a fuzzy endeavor of truth seeking and only local models of simple interactions have a “nonexistent” amount of error.
If you were inside a black hole you wouldn't be able to see light from "deeper" because it wouldn't be able to travel towards you.
This is not what we see within the universe, so I don't think we can be inside a black hole
I don't think it does once accounting fully for relativity (and assuming perfect sensors, so the idea of information being too redshifted to be detected isn't a factor until that information no longer exists within the universe, and immortality of participants, and near light speed travel).
Say Alice and Bob can communicate X years apart at near C speed. At any time, Alice can jump on a spaceship and reach Bob in ~X years. Therefore, anything in Bob's observable universe at that time counts as also being in Alice's observable universe.
If the distance is so far apart that one day space will expand too fast, then there is a moment where Alice stops being able to travel to see Bob ever again. At that moment, Bob's observable universe is now distinct for Alice's, but they also can no longer communicate.
Bob could get on a spaceship going near C away from Alice and access information that is outside of Alice's observable universe, but Bob only crosses that barrier when he moves far enough away from Alice that he exits her observable universe. (Technically I think you get some sort of infinite sphegettification of Bob leaving as he crosses Alice's observable universe's event horizon, where he never fully leaves and sends back photos that become more and more red shifted until their wavelength equals the diameter of the observable universe.)
So Bob has an observable universe that is different from Alice's, but it is predicated on him exiting from Alice's observable universe to access it. Either he accesses it and stops existing to Alice, or he doesn't access it and eventually it falls out of what he can possible access. The only part he can access and still communicate back to Alice is the part within Alice's universe. It is a bit like a superpower to turn invisible only when no one is looking... sorta kinda...
Given enough time, Alice and Bob either drift together until they clearly share the same observable universe, or eventually drift apart to the point expansion of space shifts them into two separate unrelated observable universes and they stop existing relative to each other.
I’m willing to concede I don’t know enough about the actual math of cosmology and relativity to say. How certain are you in your reasoning? I’m willing to admit either case could be possible and neither is a testable prediction at this time but maybe my first principles reasoning is outright flawed?
There is also the matter of possible verses actual light cones. Assuming we had a ship that could go near C, imagine Alice doing three things. Alice v1 stays home. Alice v2 goes racing off near C to the left. Alice v3 goes racing off near C to the right. Each of these will have different light cones, but Alice v0 who hasn't made a decision could make any one of these decisions and thus all three light cones are in her possible light cones if she chooses to pick each action. Eventually each Alice will be so far away from each other that expansion of space splits their light cones into entirely separate ones from that point on.
>How certain are you in your reasoning?
Not at all. This is just based on my understanding of the very basics. The reason I'm sticking to it like I am is because, if I'm wrong and someone can point out where, it becomes a really good learning opportunity for me. And if I'm not wrong (at least given the layman level of detail of the conversation), the better I can explain my reasoning the better someone else might gain new ideas from it.