They are useful to us, but every now and then it's helpful and humbling to remember it's a fiction we assign, rather than fundamental.
Criminal justice or the concept of culpability is one of these areas. I know I've seen material by Robert Sapolsky, a neuroscientist who does not believe in free will, talking about how off the mark criminal justice and punishment for crimes can be.
However I didn't just assume a lack of free will. I also assumed a lack of identity. Do you realize that who you are is socially defined? When you breathe in, the air in the room around you becomes part of you. When you breathe out, you lose certain gases. When you eat your food, similar story. There's a good case to be made that "you" are in the entire room or the entire food chain. That does make causality and culpability hard to assess objectively. When we do so, we do so subjectively.
In that case I dub you a mushroom.
We would do well to remember that every now and then. People who get too into pretending their perspective is objective reality tend to do stupid things.
> like a virus doesn't become part of me -- the immune system acts a biological discriminator between what is part of me, and what is not
But what about symbiotic organisms? What about your microbiome? Or the mitochondria, which began its existence as a separate organism? Or, they say our DNA includes many viruses that our ancestors contracted. A number of these things do stick with us and we sometimes even become totally dependent on them to function.
To pick one possible simple and broad definition from WP, "Identity is the set of qualities, beliefs, personality traits, appearance, or expressions that characterize a person or a group." -- you made it sound like that set is empty, which doesn't make sense to me. My identity is part of "I". Every being has an identity; it's not something you can get rid of?
In any case, I find your comment very interesting. I'm studying quantum computing at the moment, and I've had to read the different interpretations of quantum mechanics, including Everett's many-worlds interpretation. As a non-physicist, I've found the different interpretations fascinating.
The many-worlds one, as far as I understood it, says that all the possible outcomes of a quantum measurement actually "happen" in different worlds. I have the impression that you would be able to give a much better explanation.
In any case, in the joke the gun is shot in the macro world, not in a quantum state. It's possible that it is a quantum gun, but probably not.
Let's say "overruled" then.
Collapse theories, in contrast, state that at specific points in time (the "measurements"), the wave function stops following the Schrödinger equation, and instead collapses to a single slice/branch/world, thus upending the natural proliferation of branches implied by the normal time-evolution of the wave function according to the Schrödinger equation.
Even in many-worlds, however, the wave function doesn't necessarily contain all conceivable worlds. It only contains the worlds, following from some initial quantum state, that follow from the Schrödinger equation. While it's true that all possible outcomes of a quantum measurement become real (because they are all contained in the wave function in superposition), "possible" here means specifically what the equations allow, not any imaginable world.
There may be other universes out there, with their own big bangs, but that has no effect on ours.
Reading this article, I think they are simply disputing the necessity of singularity inside a black hole, and hypothesize a universe which expands from non-singularity black hole, while staying inside its own event-horizon.
That is how I understood it at least, somebody please correct me if I misunderstood it.
But a cycling of a previous universe.
I was a little unclear on the ending, where he says this theory would place our entire universe "inside" a black hole of a parent universe.
All in all, it does seem to tie up some loose ends, and suggest some order to what previously required speculation.
Based on the information we have available about our universe, we can't make predictions or formally model anything prior to a certain point in time, consequently it's convenient to treat this moment as the earliest point in time in which physics as we know it makes any sense. So while there may have been some kind of existence prior to the Big Bang, we have no way to make sense of it even at a conceptual level. Given that, we may as well treat this special point in time as the beginning of the universe as we understand it and can explain it using physics, as opposed to some absolute beginning of all of existence.
So IRL there's no time, there's no need to have a beginning or an end. Whatever happened when all the matter was close together isn't the beginning of anything, just a phase.
There is no time factor in any absolute entropy equation.
Empirically, if you measure the entropy of a closed system at a given time, and you measure the entropy of that same closed system at a different time, then calculate the deltas of each, their signs match so long as the time delta is finite and the system isn't empty. So stated plainly, as time increases, so does entropy.
By combining these first principle formulae with the empirical results on entropy, you arrive at the second law of thermodynamics. However, like I said before, we're not really sure why the signs match and it's considered to be an unsolved problem in physics.
https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...
And from first principles, that's what entropy is, a measure of how energy is dispersed throughout a system. Of course once you have that first principle understanding of entropy then you can come up with more rigorous formalisms to properly quantify what it means for energy to be distributed throughout a system, such as measuring the number of microstates that correspond to a macrostate, and other various formalisms that are more or less equal to each other... but fundamentally they all start from this basic principle.
That said, I personally think such thought experiments are futile and the nature of time has to be understood by its connection to causality and information.
Entropy only statistically tends towards an increase in closed systems and neither your computer or your brain are closed systems. They are both constantly getting energy from an external source of power and in turn dispersing previously consumed energy out into their environment.
And yet you still manage to perceive things just fine... in fact your perception of the world is unlikely to change whether or not the entropy in your brain increases or decreases by some bounded amount (of course too much of either an increase or decrease will destroy your brain).
Your claim about remembering an event, which likely alludes to Laplace's demon [1], requires an overall increase in entropy in the system as a whole, but does not require an increase in entropy in the specific part of the system that is recording the event.
Every time your computer calls a function like memset(dst, 0), or sorts a list, or arranges data into some kind of structured binary tree, your computer is decreasing its own internal entropy by taking a statistically likely arrangement of bits and transforming it into a very unlikely arrangement of bits. The decrease in the internal entropy of your computer is more than offset by an increase in global entropy but that global entropy is radiating way out into the cosmos and has no impact on your computer's ability to register information.
It's useful because its quantifiable.
Is it the same universal every time? If so, see you later alligator.
(I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was.)
> I acknowledge that not everyone involved in science has or wishes to acquire the skills needed to write blog-form content.
They should. If your research is publicly funded you should make it as available to be public as possible. Academics should be able to communicate, and I very much doubt they are unable to acquire the skills
> I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was
Given how bad the measures of impact and the distorted incentives this produces I am not even sure this would even be a bad thing.
If nothing else it improves transparency about what they are doing, again with public money.
So in addition to being:
-professional researchers
-professional teachers
-professional project managers
-professional budget specialists
-professional scientific writers
-a failed idea away from losing it all
They should also become:
-professional PR managers
-professional popular writers
While still being paid (poorly) for a single job of all of these.
I am not suggesting they become PR managers, and the writing skills I am suggesting they acquire is simply that required to do things like blogging. I am not suggesting they achieve the standards a professional writer would have, just the ability to write clearly and make the effort to do so.
Academics should be highly skilled people.
In fact a lot of the problem is not they cannot do it, but of distribution. A lot of universities to have academic blogs and subsites about departments and individuals research. Its not anything like as visible as the journalists write ups about it
However, we live in an imperfect world. When people say "should" in these contexts, they're not describing some ideal way the world works. They're prescribing actions that are realistic based on the current system we live in.
The world sucks. It's more useful to work with the small amount of control one has, than to do nothing because the action doesn't solve a wider systemic problem.
The public can access it by becoming subject matter experts. If the government or the public to which it is responsible requires a popsci treatment they can pay other people with this skill set.
I don't doubt having this skill set is useful I merely disclaim any sort of obligation on the part of the scientific staff to possess or exercise such a skill.
Being able to effectively communicate to different people on your team, outside your team, managers, business people, etc is not optional and more than once I've seen things get stalled or turn into a mess because communication didn't happen.
STEM is often a haven for neurodivergence but I think communication skills are something that is largely learned and not something that comes naturally for everyone. People who are good at communicating spend a fair amount of effort rewriting, trying different wordings, different introductions, getting feedback from people, etc.
FWIW I see things like being able to sell a proposal, managing expenses, planning, etc as optional - these are good to have, but someone else can do them if you can communicate well, but in the end the only person who can communicate what you're thinking is you.
Blog form content in particular, _requires_ proofing, re-editing, and so on and there's a whole skill set which contributes to makes such content sticky and engaging.
You also seem to be confounding your own point. Indeed all work is collaborative, someone who lacks communication skills, will generally team up with other collaborators who can bring those skills to bear.
It still leaves a lot of questions though, especially if you try to marry quantum mechanics to these makroscopic models. Where did the initial black hole come from and should a corresponsing anti matter black hole exist?
https://www.amazon.com/World-Physics-Library-Literature-Anti...
It is indeed "often described" in the media as such. However, that is _not_ the currently accepted theory. "What if there were no space and time before the Big Bang" is just Stephen Hawking's pet theory.
While we don't "know" how gravity works we can explain it and model it much more accurately now than when logos was the explanation. Providing those details is far more useful than a simple "we don't know."
> There is no law of the universe that guarantees that science is capable of answering all questions.
There's a name for a more nuanced version of this "law" and there's a good amount of work being done arguing for and against weaker and stronger versions of it: https://plato.stanford.edu/entries/sufficient-reason/
Various isolated cultures are going to come up with different names for God.
This like saying which Sun? Surya, Ra or Helios?
All are different names of sun. But there is only one sun.
Furthermore, assume God doesn't exist. Lots of cultures might invent god for various reasons and they'd naturally have different names and attributes for them, which in fact seems to be the current state of affairs.
In fact, if we assume God exists and is actively in communication with humans, its actually a bit weird that different human cultures would have different conceptions and names for that being. Why didn't it just give everyone the same name and information?
To answer the question of why humans give name to God. It's to make god more relatable so that they can workshop it. And use devotion to come closer with it. Look up Bhakti Yoga.
Now, you cannot worship consciousness as humans because it's invisible and you can never imagine it. You need a version of consciousness that you can see as well as you can relate to. So cultures invent localized version of God which people can relate to. And of course it will have attributes similar to that of the culture. But the properties kind of still hold. Like all knowing, powerful etc.
I've always thought arguments like these are unnecessarily applying a term loaded with human conceptions and biases in a way that doesn't shed any further light on the thing it's applied to. Like, what do we gain by defining "God" as consciousness? Why can't we just say "consciousness"? And is it worth the added confusion that when we say "God", we now don't mean what most people think "God" is?
The only reason I can come up with to do this is discomfort at saying, "I don't believe in God."
If the only common factor is a belief that 'something' created 'something', you're really not saying anything worth evaluating.
People hate not knowing the answer to the big questions so much that they'll readily accept whatever answers are served up to them.
> This like saying which Sun? Surya, Ra or Helios?
The difference is that the sun is readily observed. A conveniently invisible god isn't.
> All are different names of sun. But there is only one sun.
And there's only one human nature, which is why it's not surprising that common artefacts of human nature (e.g. religion) emerged universally throughout ancient human cultures.
But ego and names are made up. Separation just thoughts. The more life believes in thoughts it becomes divided.
But the waves and ocean are one.
You can declare Life to mean the complex interplay of every living organism, but I don’t see how you can go as far as to claim our physical and mental separateness is not there at all? After all, we need boundaries between „us“ to not be utterly alone. I like to think even of „my“ body more as a federated system, like Life maybe but on a smaller scale. I have some influence on it but not full control. In fact, one could say the polarities in the physical realm are Nature (towards separation, entropy; Kaos) and Life (actively working towards one, requires energy to keep matter ordered; Order).
If we merge, by definition the „I“ and „you“ have to die; both of us stop existing. The merger creates something new, a „we“. A single entity. We can then use the definition of identity to call this new we „I“. Rinse and repeat until back to being alone/all-one?
Do you really want to be all-one? Omnipotent, full of all potentials/possibilities? I don’t know. I am already overwhelmed with my limited human potential/possibilities/options. And I prefer to not be alone. I prefer to stay separate, and keep my identity.
I believe (lowercase b) in all sorts of stuff, scientific and otherwise, but believing in God typically indicates some kind of act of faith, which is to say, ultimately, to believe in something despite the absence of evidence for it and for some deeper reason than can be furnished by a warrant of some kind. I can believe in the spontaneous generation of the universe in the lowercase b sense of the word without really having anything to do at all with the latter kind of belief, which I think is kind of dumb.
https://www.vatican.va/content/pius-xii/en/encyclicals/docum...
> General relativity also predicts that the initial state of the universe, at the beginning of the Big Bang, was a singularity of infinite density and temperature.[6][obsolete source] However, classical gravitational theories are not expected to be accurate under these conditions, and a quantum description is likely needed[7].
I didn't know but apparently wikipedia treats old sources as obsolete, doesn't matter if there's new information or not that would make it obsolete.
I wonder if any sources supporting the notion that the earth is round must be updated every couple of years with a new source or study.
As an aside, the earth is almost flat, just not nearly as flat as the Universe.
Source? And make sure to update your response every few years.
Thus, anything and everything you've heard about what is there "before the big bang" has always been speculation. I mention this because sometimes people read the science media, which is always reporting on this speculation, and think that the reporting on the speculation constitutes "science" constantly changing its mind, but that's not the case here. Science has consistently not had a justifiable position on this topic, ever. It has always been speculation. It is the press that often fails to make this clear and writes stories in terms of what "science" has "discovered", but any claims of certainty in this area are not the claims of "science".
We went from thinking the Earth was the center of the universe, to the sun being the center of the universe, and the next obvious step is our universe isn't at the center of universes.
If the universe is curved dark energy is still a problem because the expansion is getting faster and overcomes the current curvature bounds.
(the basic idea was fecund universes/cosmological natural selection[1], such that we should expect to find ourselves, if the theory were true, very near to a local maxima of values such that they approximately maximize the number of black holes produced... but most of the book is really taken up with a fascinating look at the history of physics and ideas...)
[0]https://en.wikipedia.org/wiki/The_Life_of_the_Cosmos [1]https://en.wikipedia.org/wiki/Cosmological_natural_selection
* Not a physicist so this is a really uninformed take
Does it also follow that black holes in our universe contain universes internally, beyond their event horizons?! Seems like it should. Mind-blowing.
https://en.wikipedia.org/wiki/White_hole#Big_Bang/Supermassi...
It’s holes all the way down
Not necessarily. It's not clear that any are massive enough to cross the threshold required for the "bounce."
I'd love the idea that we are living inside a black hole, which is inside a black hole, which is inside a ...
There's a reason some of the most famous mathematicians, scientists, engineers, and philosophers of all time believe(d) in God.
The Hebrew name of God, YHWH, literally means "He Who Is." In other words, the Self-Existent One. The father and originator of all things that were, are, and will be, who exists outside of spacetime.
Who Created God? No one? Why does the universe need a creator if God does not?
Where does free will and evil come from if God is "originator of all things that were, are, and will be". For true free will to exist it must have a source of entropy which denotes something outside of Gods control and design otherwise everything is deterministic as set forth by God.
There are countless other religions that believe in a deity who created the universe. These deities either created themselves, or had always existed outside of space and time. To that end, any one of those deities would be on equal footing with YHWH. I don't think that it is appropriate to axiomatically claim that a certain deity exists because only that deity could have caused the universe to exist.
Why Christianity then, over Hinduism? Why any human religion at all?
[無] https://en.wikipedia.org/wiki/Trinitarianism_in_the_Church_F...
I like to think he was referring to computation. There's a reality to the constant pi, its computation, and ourselves and the representation being part of that same universe.
That reason being that for much of Western history if you didn't believe in God the Church would burn your research in a big fire and probably you on top of it.
I definitely didn’t understand whether this is suggesting that expanding universes can be contained within black holes that look like fixed-size finite objects from the outside.
And what happens to the inner universe when the parent black hole evaporates through Hawking radiation?
I've often wondered about this. I don't have any direct physics training, but it's something that felt really plausible after I learned that the mass of a black hole is linearly proportional to its swarzschild radius.
As the size of the black hole goes up, its overall density must decrease. Combined with the other observation that our universe has uniform density at large scales, it seemed really obvious to me that there existed some threshold at which the decreasing density of a very large black hole, and the fixed density of our observed universe.. would cross.
I used to muse about this question with some other tech colleagues that liked talking about physics stuff but never really got a clear answer to this.
On a side note - I'm absolutely fascinated by the implications relating to this. I'll post a follow-up thought I'm hoping somebody else has also thought about:
I've seen discussion of dark energy mostly presented as a surrogate for real energy. That there is some underlying energy "accelerating things away from each other".
I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
The energy loss pervades to the quantum world as well - photons that start off high frequency arrive low-frequency.
It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return. Maybe like a black hole evaporating as observed from the inside?
When I asked this of some people in real life, I was pointed to answers that indicated that the "energy" component in dark energy is normalized into the "tension" of space somehow. As I mentioned before I'm not really studied in physics, but that explanation felt unsatisfactory to me.
I think my estimate came out to less dense than the required threshold but it was a while back now and cobbled together with some queries to wolfram.
But in this story the black hole increases in size as matter falls into the horizon and shrinks as it evaporates, so cosmic expansion would be associated with more energy falling into the black hole than leaving it.
Apparent distance is something that's affected by relative frames of reference and the frames of reference are as different as as can be in this case.
So time in the void between galaxies is moving quicker than time in the galaxies, but on the grand scale of the universe the differences as up a lot.
I quite liked this theory, think is make sense, at least from my very limited understanding of this stuff.
Another layman's thoughts: Isn't the energy theoretically lost by black holes so faint it's currently undetectable? And isn't the amount of dark energy theorized to be the major component of the observable universe? It seems like the numbers wouldn't add up?
I'm gonna pull out my lay understanding again. An evaporating black hole, as it gets smaller, should get more dense and be associated with a higher local spacetime curvature, no? The effect of which would be to slow down apparent time for observers within the system. Maybe that affects observed distance and rates of speed at which things seem to be happening when we look out into the sky?
Sometimes I regret not caring enough about calculus in university.
s/has/had at the time of recombination
It is largely an assumption of LCDM that we can treat the universe as practically homogeneous throughout its entire evolution but potentially not a very well-founded at that [0, 1].
> I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
Your intuition is correct. If the Lambda term in the Einstein field equations is moved over to the side of the energy momentum tensor, it takes on the role of a negative contribution (provided Lambda > 0, as observations seem to indicate).
> In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
Note that there is no global energy conservation in General Relativity[2], only at a local scale[3]. Heck, you'll already struggle to define what the energy is of a given piece of spacetime in a meaningful and generic manner[4, 5]. In other words, violations of energy conservation due to spacetime expanding or contracting (a strictly non-local phenomenon), like in the case of the cosmic redshift, are expected and our intuition from classical mechanics only takes you so far.
> It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return.
Dark energy aka the cosmological constant term in the Einstein field equations is a constant term, as the name suggests. Yes, there can be energy loss due to spacetime expanding (see above) but that doesn't change the gravitational constant.
[0]: https://en.wikipedia.org/wiki/Cosmic_web
[1]: https://en.m.wikipedia.org/wiki/Inhomogeneous_cosmology
[2]: https://en.m.wikipedia.org/wiki/Conservation_of_energy
[3]: https://en.m.wikipedia.org/wiki/Stress%E2%80%93energy_tensor
[4]: https://arxiv.org/abs/1510.02931
[5]: https://en.m.wikipedia.org/wiki/Mass_in_general_relativity
The center of a black hole is infinitely dense. That's why it even exists. The event horizon is not the black hole.
> and the fixed density of our observed universe
Our universe is expanding. It's density is not fixed.
You really want to be thinking about this in terms of entropy and not matter.
Arguing semantics is rather boring when it's obvious you understood the point he was trying to make.
> Our universe is expanding. It's density is not fixed.
None of that precludes uniform density at large scales.
Wouldn't you notice that fairly suddenly everything's getting brighter because all the light/radiation is sucked back in?
For smaller BH, the gravity gradient is higher and it would be detectable.
> None of that precludes uniform density at large scales.
According to observation, the universe is expanding. An argument that it's really static at a large scale would require contradicting observational evidence, but none exists. A theory that requires abandoning observational evidence bears a special burden, which this theory lacks.
And whether the density is fixed over time or not doesn't affect the question. Let's take the universe at its current average mass/energy density - whatever the "true" measure of that is.
To the best of our understanding, at large scales the density is uniform. So if we consider a suitably large spherical volume of space within our (presumably infinite) universe.. that volume will have an average mass/energy content greater than the threshold amount for a black hole of that apparent volume (again, using the external event horizon frame).
So that suggested to me that either we live in a finite universe, or we must be on the inside of an event horizon. It seems like an unavoidable conclusion.
> The center of a black hole is infinitely dense. That's why it even exists. The event horizon is not the black hole.
>> and the fixed density of our observed universe
> Our universe is expanding. It's density is not fixed.
These are both correct and germane points. So why was this post downvoted? Physics isn't a popularity contest, it relies on evidence.
The size and density of the Schwarzschild volume is determined only by mass (stationary, non-rotating). It's proportional to the inverse square of mass. Density = 3c⁶/32πG³M².
SMBHs have densities ~0.5 kg/m³ between thin air and water.
Stellar BHs are ~1e19 kg/m³ several orders of magnitude more than a neutron star.
Since we don't have a blackboard in front of us to interact with, I can suggest Alan Guth's lecture notes on Newtonian cosmology. (Guth is credited with discovering cosmic inflation.) https://web.mit.edu/8.286/www/lecn18/ln03-euf18.pdf See around eqn (3.3). You could also borrow a copy of Baumann's textbook <https://www.cambridge.org/highereducation/books/cosmology/53...> which studies the Poisson equation for various spacetimes, however a static spacetime gets most of the focus.
A universe which expands forever, or which expands faster in the later universe, makes a mess of this sort of approach to calculating a gravitational potential energy. So does any apparent recession velocity that's a large fraction of c (inducing significant redshift, whatever the recession (pseudo-)"force" might be).
However, the general idea is that there is a relationship between the kinetic energy a receding galaxy (in a system of coordinates -- a "frame" -- in which these kinematics appear) and a gravitational potential energy still occurs in a non-recollapsing universe. It's just that the potential energy climbs forever, and you get an equivalent to gravitational time dilation between galaxies at different gravitational potentials (i.e., between early-universe galaxies and higher-potential modern-times galaxies).
Accelerometers in galaxies will not show a cosmic acceleration for any galaxy; they're all really close to freely-falling (local galaxy-galaxy interactions are real -- collisions and mergers and close-calls happen -- but wash out over cosmological distances; look up "peculiar velocity" for details). Therefore we can conclude that there's no real force imposing acceleration on the galaxies. However that's also true of a cannonball in a ballistic trajectory, including one on an escape trajectory or one that enters into a stable orbit. Consequently one can draw some practical comparisons between a ballistic launch from Earth into deep space and galaxies spreading out from an initially denser early part of an expanding cosmos.
> Dark energy as energy being extracted out of the universe
No, it's just a way of thinking about whatever is driving the expansion, and that doesn't dilute away with the expansion as ordinary matter and radiation does. It's not even a "real" energy in the sense that it is only an energy in the cosmological frame, and is a frame-dependent scalar quantity, whereas in the fuller theory it's just a multiplier of the metric tensor. So it's the full relativistic metric doing the work but we absorb some of that into cosmological coordinates in the cosmological frame of reference, carving up the metric tensor into a set of vectors including an expansion vector identical at every point in spacetime.
The expansion vector can also be thought of in terms of pressure: in a collapsing cosmological frame, a pressure drives galaxies together into a denser configuration. The inverse of pressure is tension, so in an expanding cosmological frame, it's a tension that pulls galaxies apart into a sparser configuration. (The reason one uses pressure or its inverse is that the matter fields are idealized as a set of perfect fluids at rest in the cosmological frame; each such fluid has an associated density and internal pressure which evolve with the expansion or contraction of the cosmos, generally becoming less positive in the time-direction of expansion (i.e., in the future direction in a universe like ours). Another way of thinking about pressure is as a measure of isotropic inflow of energy-momentum into a point; increasing pressure at a point therefore increases the curvature at that point. Tension is an isotropic outflow, and so positive tension is repulsive as opposed to the attraction from positive pressure.)
> that explanation felt unsatisfactory to me
Hopefully the above helps a bit. Unfortunately there's only so much teaching one might do in a series of HN comments, and ultimately one probably is better served in developing some grounding in the full Einstein Field Equations / Friedmann-Lemaître equations before thinking in quasi-Newtonian ways. Going the other direction tends to lead to misunderstandings and developing false intuitions when running into situations where the quasi-Newtonian picture needs post-Newtonian correction terms.
It's cool that you have all sorts of questions. You could consider signing up for part time / non-business-hours courses in relativity at a nearby community college or the equivalent, depending on where you are, or maybe just bringing a hot lunch to a lecturer there in exchange for a quick informal tutorial. Anything like that is bound to get you to better answers than raising comments on HN threads about astrophysics in the broadest sense, as answers here are often somewhere between non-standard and unreliable.
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.1...
I guessed c once. It would be a constant. Maybe all the constants are spaghettified remains of a superior universe.
In "natural units", we define the units so that the important conversion factors (c, G, h-bar, etc) work out to exactly 1. You can say that c is one light-year per year and then forget about it.
The true parameters of the universe are the dimensionless constants: the fine structure constant, proton-electron mass ratio, 3+1 dimensions, etc.
dont be so sure! there is no way to experimentally know if c is a parameter or not. there are consistent physics formulations which have variable, even anisotropic c. physicists dont usually explore them (e.g. tangherlini relativity) though because the math is considerably harder.
Relativists sometimes like to explore things that make using the Tangherlini transformations rather than the Lorentz transformations look positively benign. (To be clear, the Tangherlini synchronization system is clearly unphysical, requiring infinite speeds. His thesis also proposed using a distinguished global frame, which is not really philosophically different from how the standard cosmological frame is used, and seems OK because the distribution of stress-energy can pick out useful systems of coordinates in standard relativity. Unfortunately his method frustrates and probably outright breaks comparisons between inertial reference frames related by a boost, which the standard cosmology does not, and it's hard to see an alternative method that preserves his central ideas.)
But why even be stuck with 3+1d spacetime like Tangherlini? He was trying to do physics. But an unphysical metric signature with 47 plusses and no minuses is really cool!
In our observed universe, FAPP, c is the same everywhere after recombination, and we get that from spectral lines. You have to play really weird games to preserve the Lyman-alpha forest's apparent isotropy while introducing spacetime (or redshift-space, here) anisotropy. Things like BAOs make the problem even harder.
If we strip away all that pesky radiation and the information its structure encodes, analysing variations of c gets a lot easier. A relatively recent paper (Lewis & Barnes 2021) I enjoyed considered anisotropy in the one-way speed of light in an FLRW cosmology with zero energy density (well, really the convenient Milne model, which is also far from spatially flat). "So far, we have considered two cases, where either the speed of light is isotropic, or the extreme case where the anisotropic speed is 1/2 in one direction, and infinite in the other. The question remains whether this holds true in general case, for an arbitrary κ": https://www.cambridge.org/core/journals/publications-of-the-... (arxiv: <https://arxiv.org/abs/2012.12037>). "For more general cosmological models, where the presence of mass and energy results in curved space-time, the picture is more complicated as there is no simple mapping of the modified Lorentz transformations into the general relativistic picture. We leave this discussion for a future contribution."
Sadly there doesn't seem to be a future contribution yet, at least going by published citations (<https://scholar.google.com/scholar?cites=2012575105829699847...>). (Of those, I've put the Chamberlain paper on my to-read pile; you'd appreciate how it relates to Tangherlini, "credence is given to one-way infinite light-speed inward to each particle in direct comparison against Einstein’s isotropic (c=constant) light-speed").
Of course there's also the excellent Magueigo 2003 VSL overview <https://iopscience.iop.org/article/10.1088/0034-4885/66/11/R...> copy <https://cds.cern.ch/record/618057/files/0305457.pdf> preprint <https://arxiv.org/abs/astro-ph/0305457>.
And even if you can make sense of an f(c) cosmology in the early visible universe, you will get to epochs before recombination and try to make sense of the later universe's chemistry, which of course relates to big bang light nucleosynthesis, baryogenesis and electroweak ssb. How do you abolish Lorentz symmetry in those epochs? Good luck!
(I mean, I think if you are doing physical cosmology you ought not to ignore gauge theory...)
you get pseudo black holes but depending on the extremeness of the deviation from linear, the difference to black holes might not be observable with current tech.
There are a variety of types of variable speed of light. If we foliate to 3+1 the usual picture is that c is constant on all spatial slices. Some VSL theories have the same c at all points on a given slice, but introduce a time variation of c. Other VSL theories introduce spatial variation as well (or instead). These families of theories all have significantly different equations of motion or actions from one another (cf. <https://en.wikipedia.org/wiki/Einstein%E2%80%93Hilbert_actio...>). There's no obvious reason why c couldn't relate in a more complicated way to the stress-energy tensor than the Einstein gravitational constant does, but there's also no obvious reason to think such an alternative theory should produce free-fall trajectories similar to those from GR.
In any case, I think you have to choose your function on c, obtain the field equations, decide which energy conditions and constraint equations you want to impose, set appropriate boundary conditions, choose a curve along which to foliate, and run with enough different initial-value surfaces (each of which must satisfy the constraints initially), that eventually an intuition develops. A Will-like parameterized post-Newtonian formalism approach would also be a good idea (<https://en.wikipedia.org/wiki/Parameterized_post-Newtonian_f...>).
Unfortunately I'm unable to guess your choice of "c(m) formula".
Or is that too simplified?
--- > | > >> . << < | < ---
The second half is incorrect. Since the time coordinate becomes spacelike in turn you'll still have 3 spatial degrees of freedom. Dimensions can't just vanish if you believe that spacetime is a 4D Lorentzian manifold (as physicists do).
Moreover, the singularity is not a place you can poke with a stick, once you've entered the black hole. It lies in your future, in the same way as your death.
Can we say that one of the spatial dimensions (the radial dimension) and the time dimension combine into a single dimension? After crossing the event horizon aren't they 1:1 correlated?
The swapping of timelike and radial dimensions are a "game" frequently played with families of coordinates, including Schwarzschild coordinates. One can apply any system of coordinates on a physical system without changing the behaviour of the physical system: coordinates are unphysical. Think of navigating around in a neighbourhood: you can talk about going forward a few blocks then turning left, after which you go forward two more blocks; or for the same journey, going "city north" a few blocks then going "city west" two blocks. Here assuming that (initially) "forward" is in the "city north" direction (and "city north" is not necessarily exactly magnetic north nor a section of a meridian of longitude). After the left turn, "forward" is "city west". There's an analogue to the discussion's (ab)use of Schwarzschild coordinates.
In Schwarzschild spacetime, without applying any system of coordinates, just floating in free-fall far from a black hole extremizes your travel in the timelike dimension. (You can do this at home: you stay put at some point on Earth (whether you use GPS latitude/longitude/altitude or some other system of coordinates) but your wristwatch keeps ticking). Inside the black hole horizon, just floating in free-fall extremizes your travel in the direction of the singularity. Far from the black hole, accelerating as strongly as you can in any direction takes travel from the timelike dimension and puts it into one or more spatial dimensions. In particular, you have the freedom to increase the spacetime interval between you and the singularity. Within the horizon, however strongly you accelerate the spacetime interval between you and the singularity shrinks. This behaviour seems to invite the use a different set of coordinates applied to a patch of space around an observer far from the black hole and a patch of space around an observer inside the horizon. It's some human cognition thing, and in the early 20th century it took decades to discover systems of coordinates that work for observers far from the black hole, at the horizon, and inside the horizon. And even today, most people don't seem to try to enhance physical intuitions by swapping among arbitrary systems of coordinates (including no coordinates) on a single physical system like a black hole and a pair of observers (one inside the horizon and one far outside the black hole).
The Schwarzschild black hole interior is still locally Lorentz-invariant everywhere (because the whole Schwarzschild spacetime is a Lorentzian manifold).
The various local interactions of the Standard Model will keep working inside a black hole. In a really tiny patch around every point, everything behaves as if its in Minkowski space (flat 4-d (3 spatial + 1 time) spacetime).
(That's one of the problems of quantum field theory on curved spacetime: the "focusing-pressure" [for experts: this is encoded in the Weyl curvature tensor; my "scare quotes" take a view of this in a Raychaudhuri equation way] gets so high that the unknown ultraviolet behaviour of the Standard Model (a quantum field theory) becomes relevant. The Weyl behaviour in Schwarzschild is that quasispherical objects are strongly prolated with the long axis aligned radially: a soccer ball or basketball starts looking like an American or Canadian or Rugby football ball. The radial stretching "spaghettifies" by ripping apart weaker bonds (like intermolecular ones, and molecular ones, and ionizing atoms), but the tangential squashing ("focusing") must eventually generate more nuclear interactions, probably up to quantum chromodynamics (QCD) energies possibly before the radial stretching starts generating hadronization.
How this works in the Standard Model is just unknown. However simpler "test" quantum field theories (fewer, or even no, interactions; and often no colour-confinement-like processes) raise really difficult questions.
Finally, back to the Standard Model as local theory: how does any allegedly quantum nonlocality behaviour work? Local here in the sence that states can be distinguished by local measurements alone. Related questions: can you entangle particles deep inside a black hole? If an entangled pair fall in together, how does the entanglement evolve? Or obsessing black hole information people, what if you throw in only one half of an entangled pair and locally measure the outside half? Nobody has great answers for these sorts of questions at present, and there's no near-term hope of testing any proposals in laboratories or via astrophysical observation.
What exactly do you mean by "spacetime swap idea"? If you're saying the behavior of Schwarzschild coordinates at the event horizon is not well-understood, then I disagree. There is nothing particularly weird or surprising going on, there's just a trapped surface[0].
Some of the problem is that Schwarzschild coordinates have surprises buried in them, and what \Delta r and \Delta t mean are not what most people tend to think.
Someone should do an ELI12 of Unruh's (ca. 2014) excellent (give or take varying the spelling of Martin Kruskal's surname) Schwarzschild BH global coordinates pedagogic review <http://theory.physics.ubc.ca/530-21/bh-coords2.pdf> and add in a bit on Fermi normal coordinates as a maybe-obvious not-a-chart follow-on to the commenary just above eqn (55). But on "maybe-obvious", Unruh has the choice line: "Since in a large number of cases, the single horizon coordinates were discovered long before Schild’s coordinates, this is an exercise in alternate reality – what could have so easily happened if only the generators of those coordinate systems had recognized what they had."
https://news.ycombinator.com/threads?id=scotty79&next=441240...
Schwarzschild infinity is unphysical, while your notion of t(Earth) is physical because we can associate a worldline with the planet's centre of mass (COM), hold the COM at the spatial origin of a system of spacetime coordinates, and use whatever "timestamps" we like on the time axis. But we could decide that t(Earth)=infinity could be yesterday, or tomorrow, or a billion years ago, or a couple billion years from now; if we count of seconds before or after t(Earth)=infinity, we still have t'(Earth)=infinity, so it's not a very good choice of coordinate.
I think you have a misunderstanding that is probably beyond my ability to help you with, since we can't do interactive blackboard work in HN comments. The root of your problem seems to be mis-identifying the local time at Earth with the Schwarzschild time at infinity in the Schwarzschild solution. We aren't at infinity to any known black hole: between us and the most distant black holes we know of is expanding spacetime not found in Schwarzschild's solution; betwee us and the nearest black holes is substantially and lumpily curved spacetime and plenty of matter unlike Schwarzschild's unique pointlike mass surrounded by non-lumpy matterless vacuum; none of the astrophysical black holes are infinitely old today (whereas Schwarzchild black holes are infinitely old at every time, otherwise the spacetime would not be static); and in general exact solutions of the Einstein Field Equations -- even ones that are not eternal -- do not superpose cleanly with solutions for other black holes (and crucially there are no black hole mergers in Schwarzschild), ordinary stars, galaxies, clusters, and expanding spacetime. As an example: hover just above the apparent horizon of Sagittarius A*. Look at a stellar black hole in our galaxy. What do you make of infallers plunging towards the smaller black hole? What do you make of the evolution of mass of the stellar black hole, from your vantage point hugging an SMBH's horizon?
Short of taking a series of courses or finding an informal short-term tutor to walk you through particular things (you can find either at your local tertiary education school, like a community college or university), there are plenty of good textbooks on General Relativity. You seem to have found Wald's, which is probably the most rigorously and densely mathematical of several popular teaching choices, and it does not seem to have helped you. I'd guess you'd be better off with e.g. Carroll's Spacetime and Geometry or Wheeler's Gravity and Spacetime.
There is also the Israel-Darmois thin shell method, which is technically annoying but lets us cut the central part of an e.g. Schwarzschild solution and paste it into a cosmology populated with other such pasted-in subregions. We can then trace light rays from e.g. a quasar, across early expanding space to a SMBH or elliptical galaxy acting as a gravitational lens, and then across later expanding space to an approximation of our neighbourhood, adapting the rays at each shell boundary. Although there is very definitely a subregion of black hole solution in that kind of approach, the asymptotically flat part of Schwarzschild is cut away along with its distant infinities. One can compare this cutting and pasting to the Hill sphere of influence of Jupiter and those of its satellites, for example, if one were interested in a navigational plan like Juno's or JUICE's.
I guess that's my point. Noting at or inside event horizon (of any kind, not just Schwarzschild solution) is physical. It's pure math, no matter how fun, has nothing to do with reality.
> But we could decide that t(Earth)=infinity could be yesterday, or tomorrow, or a billion years ago, or a couple billion years from now;
No, we cannot. Because as you stated t(Earth), by which I meant time as it passes on Earth, is physical... Now I think I should write t_Earth instead so it looks more like subscript not function application. So t_Earth = Infinity is the moment after all of the time already passed. After every finite moment already occurred. So t_Earth = Infinity doesn't really exist ever. It's purely mathematical concept. Abstract limit of the real thing.
> I think you have a misunderstanding that is probably beyond my ability to help you with, since we can't do interactive blackboard work in HN comments.
That's probably true. Even a blackboard wouldn't help because you seem to be interested mostly in minutia and specifics while my problem lies with general reality (pun intended) of all of this and which part is real and which is just extrapolation to times that don't exist and why physicists usually don't seem to care to differentiate between one part and the other.
> We aren't at infinity to any known black hole
I'm saying exactly opposite. The black hole (its event horizon to be precise) is at infinity (infinite time) to us. Any infalling object at Kruskal diagram crosses the line clearly labeled as t=infinity which in reality can't happen because there's simply isn't infinite amount of time in the universe.
> none of the astrophysical black holes are infinitely old today
To be honest that's another claim I just don't take on faith, especially in the light of the discovery of early developed galaxies and the fact that galaxies developing this early this fast would emit so much light that it would contribute to CMB (even up to 100% of it) which throws off all of our precise math theories of how everything started. I'm more inclined to believe that every astrophysical black hole existed at the the time when CMB was emitted (and before) and had exactly same size (of the event horizon) as it has today.
> and crucially there are no black hole mergers in Schwarzschild
Do you say that because they are mathematically impossible (which I would agree with) or just because Schwarzschild modeled just one black hole so there's nothing to merge with?
> hover just above the apparent horizon of Sagittarius A*. Look at a stellar black hole in our galaxy. What do you make of infallers plunging towards the smaller black hole?
Let's assume your trajectories are parallel to skip issues of special relativity. If he's closer to his event horizon than you are he's slowed down in time for you as he is for the rest of the universe outside (just slightly less). If he's farther away he lives at a pace accelerated relative to you, in the same manner that the outside world is accelerated for you. The specific math of how both of you tend to infinite time dilationas you approach your respective event horizons should show if relative time dilation between you tends to some ratio (or 1) or infinity. I don't know which is the case.
> There is also the Israel-Darmois thin shell method, which is technically annoying but lets us cut the central part of an e.g. Schwarzschild solution and paste it into a cosmology populated with other such pasted-in subregions.
I'm not that interested in pasting them statically far away. I'd really love to see what shape two Schwarzschild blackholes (and by that I mean their event horizons because, I don't believe anything beyond them is real to us) hitting each other could look like. Maybe (|)
Thanks for recommendations for further reading.
Black hole mergers are studied using post-Newtonian methods and numerical methods because there is no general analytical approach known. SXS, Simulating eXtreme Spacetimes, and the black hole perturbation toolkit both have web presences, you could start there. There is also an academic literature on matching the waveforms in both regimes. These are checked against results from multimessenger astronomy.
> I'd really love to see what shape two Schwarzschild blackholes (and by that I mean their event horizons because, I don't believe anything beyond them is real to us) hitting each other could look like
This is well into the numerical relativity regime.
ETA: I'd pick <https://www.youtube.com/watch?v=jkpfXByQHxA> (SXS collab, "Event horizon for equal mass inspiral BBH in two coordinate systems") and the zoom-in at <https://www.youtube.com/watch?v=p4MTsCDtHMM> from a quickie cruise through some visualizations. There are links in the video description. Do beware that there are several types of horizon involved here, and they will not match your intuitions from Schwarzschild (see the point made in the zoom-in video description) which I would wager are built on the presence of a static Killing field which becomes null at the horizon, but the entire Killing field doesn't exist in these BH merger spacetimes. Roughly, though, if anything is in an orange region, it stays in an orange region. That includes a lot of gravitational radiation moving inwards in the purple region. [ETA again: the related Phys. Rev. D paper <https://arxiv.org/abs/1606.00436> has some nice details about the "duck bill" topology, too, and offers further detail on the purple region.]
https://www.youtube.com/@mpi_grav has several videos particularly in their NR playlist <https://www.youtube.com/watch?v=acHmN2MlJQQ&list=PLSYkic-Csf...>. Look for distortions in the BH horizons (whether it's an apparent horizon or some comparable surface gets into metaphysics; apparent horizons are at least locally observable), particularly the so-called "duck bill". Bear in mind the these are data visualizations principally of the waveforms, and the choices in intensities and hues are probably not going to be aligned with your intuition.
SXS has several videos too https://www.youtube.com/@SXSCollaboration - last month there was a major catalogue reorganization by the SXS collab so it may be that some internal links and semi-recent videos have issues.
And see for example https://www.black-holes.org/2024/10/02/BBH-mergers-with-spec...
Generally such simulations allow one to trace lightlike geodesics as a local probe of the lightlike horizon surfaces.
> I don't know which is the case
Exactly. That honest self-admission must be made near the start of any research programme.
Do check out Lemaître and Gullstrand-Painlevé coordinates for the Schwarzschild black hole.
I would like the article to acknowledge a bit more though that blackhole universe theories and speculation are quite old now, not radical and a striking alternative, as it is natural to think about it once you learn of the concept of event horizons. What differentiates this though is the analytical solution.
You'd see EVERYTHING that EVER crossed the event horizon. But critically, you'd see it EXACTLY as it was at the monent it crossed.
Sounds a bit crowded to me. Sounds a bit like I'd expect the big bang to look.
Outside though, you'd see everything start to blue-shift. Things below you would blue shift back to normal, and the universe above you would blue-shift and speed up until you'd see the heat death of the universe. Anything falling in after you would red-shift again as it approached to match your "normal" rate of time. Critically this would include any light or other particles, so it might be very hard to survive.
No matter how fast you go or how weird the space time you are in, your local clock should still tick steadily to you, and you wouldn't notice anything weird.
If you went in feet-first, you'd perhaps find it quite odd that your feet never seemed to cross the horizon, as they would have red-shifted so dramatically.
> you wouldn't notice anything weird.
Maybe you wouldn't notice that you never saw your feet cross, since you wouldn't have much time to ponder it before your head crossed as well, but at that point, you surely you would notice that everything below you is black, since all light (and everything else) is now destined for the singularity. That's the very definition of the event horizon. There wouldn't be any reflected light.
There’s of course a line between simply coming up with ideas that are quickly provably wrong or inconsistent vs generating ideas that are consistent and not quickly falsified. It’s especially valuable the ideas are falsifiable and it seems like this is the case here.
As such, theory finds patterns in existing knowns, makes some leaps and tries to connect them. Then empirical evidence can help solidify or falsify those ideas. But we tend not to just connect dots of empirical data without attempting to know the casual relationship, otherwise the connections can be rather nonsensical or may have weak predictive power.
With all that said I didn’t read the paper in detail nor am I qualified in this domain to say if it’s quackery or a reasonable shot a developing some new theory. It is peer reviewed and published in APS so I suspect it’s not complete quackery: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.1...
If each black hole in our universe contained a pocket universe with very slightly different laws of physics (to each other and to us), but the same amount of mass-energy on the inside as our universe had when it started, then (1) those pocket universes able to create stars and black holes would also go on to create black holes with pocket universes, but also (2) those pocket universes not able to create black holes, would not create more pocket universes.
I have never seen a reason to think that this could happen, nor why such pocket universes might have more mass on the inside than they appear to have on the outside, but that's the argument.
- direct collapse after the big bang. Those supermassive black holes now from the center of galaxies and are the earliest and simplest form of how universes reproduced
- stellar collapse, requires the formation of stars, but those can be much more plentyfull than previous supermassive direct collapse black holes, so many more universes will have those
- black holes created by technology. Since black holes are incredibly efficient at converting mass to energy, in a universe that has the capability to form intelligent life, this life will eventually find a way to harness black holes as an energy source. In doing so they would create even more tiny black holes (maybe to power spaceships?), so such universes would form the most offspring.
- Earl Sweatshirt
At the time I couldn't understand why my dad laughed about that particular phone call from the principal.
Scientist still can show their theories and search papers and i can't understand a shit but i don't believe in any theory that proves how the universe got created.
Maybe the problem isn’t complexity, but that science gets arrogant when it drifts into realms where its claims can’t be falsified ;-)
It most certainly is. Each of those 340 million citizens is a unique person, with unique circumstances. You can't fit an equation to that.
>science gets arrogant where its claims can't be falsified
This article proposes testable predictions?
You might still lose, and so you might choose to also believe it will land on tail this time, but the rationale for choosing tail was not based on a belief system, but the going information and where it points too.
I stumbled upon this paper [1, 2] last night that challenges the CMB, and thus the underpinning of much of our understanding about the age and evolution of the universe. As a layperson, I don't know the impact factor of the "Nuclear Physics B" journal - if this is just junk or if this is a claim that will pan out.
My point is that it feels like we're building on a lot of observations that are all super indirect. I know I'm just a layperson, but that feels weird when reading assertions about these things.
Our understanding of the universe is relatively new. We don't have a lot of energy or resolution in our observations. The fact that we can sniff the molecular spectra of exoplanets is so amazing and that part feels totally concrete and rock-solid. But I get skeptical when I see claims that we know how the universe began or how it will end. Is our evidence that good? Are our models? Are we basing everything on assumptions?
Absolutely, but you are interpreting it in the rewritten headline money making attention grabbing version.
The original version of the claims always say that from some observation, experiments, and projection from known models it derives that the universe likely began this way, or will end that way, etc.
That means, of all the going hypothesis, this might be the one with the best chances of being true, or close to the truth. It's not an absolute, but its the one that has the most chances due to the evidence behind it.
The assumption is, you never really know, but if the model in which the theory says X, is able to predict something in the future or some experiment for Y, than that model appears to better approximate reality. Or is that knowledge and model allowing us to now do something we could not before, etc.
Over time, it course corrects to improve its knowledge and models in ways that show better results for prediction or invention.
It can be, but generally the concept of 'belief' isn't attributed to ground truths; it's just 'the truth', you rarely hear the phrase "I believe 2 and 2 is 4." , it's just '2 and 2 is 4.' -- I think that's important.
In fact, a lot of people insert the word 'believe' to insert a concept of self-doubt. "What was our last test results passing rate?" "I believe it was around 95 percent.."
But semantics aside here's the real question : Why do you have some kind of notion that you should 'believe' anything without being able to understand it? Just trust in the world and those around you?
We haven't figured origin yet, so let's get off that, but when a scientist of some sort makes a discovery, they release evidence and methods , and you decide to believe the conclusions without an understanding of the work -- well that's just a display of faith. Faith in the scientist themselves, the system they work within, and the society you're in.
Which leads me to say this : If you make an effort to begin to understand the frameworks and systems which lead to scientific conclusions you can largely remove the faith and belief elements up until you hit the very highest spectrums of each field where speculation comes back into play.
tl;dr : if you 'cant understand a shit', you don't put any leg-work in and make an effort to speak the language, you'll probably end back up in beliefs rather than an ever increasing codex of knowledge -- regardless of the field. That's okay -- but it doesn't offer the same benefits as knowledge -- it just lets one say things like "I don't believe in any theory..."
Opinions:
A) I love all the scifi book recommendations that cone up on HN
B) i wish you’d all stop recommending great and amazing books. My queue is so backlogged and jammed I'm never going to catch up.
Several comments and sci-fi series later, and I’m currently reading about spacefaring sentient spiders.
Only joking, I'm remiss anyways.
Anyone else think this is what happened?
https://www.pbs.org/video/could-the-universe-be-inside-a-bla...
Love PBS space time !
Consciousness has the property to render infinite universes and theories.
But we have no clue how universe creates consciousness.
It's like persons inside GTA talking about measuring the Samsung monitor. It makes no sense cause they can never see the monitor or locate it. They appear in the monitor.
Conversely, in your definition, is consciousness the only "thing" that you would describe as not being able to measure various aspects about it? Are there any other objects or concepts which you also cannot measure various aspects about? If yes, what differentiates those things from consciousness?
There's no reason to think that consciousness is an important question in the objective sense; it just matters to people. (and rightfully so) People wondering about consciousness in the universe might be akin to dogs wondering what the big bang smelled like.
I don't follow GP's sort of solipsist (?) take, but would say question of whether big bang took place in a black hole is pointless compared to life/experience and how they arise.
I am not interested in that.
I am interested in the thing in which all the made up stuff appears. And the thoughts and mind appears. Even I appear in that.
In that sense black holes are areas where our universe has reverted from it's low entropy state all the way back to the initial nearly infinite entropy state.
So e.g. I have hunches that there's no way there is a God that's in any way as religions might think it is, and I do have a hunch that we somehow happened from probably deterministic chain reactions, but it's a hunch, it's hard to call it a belief, or it's hard to think that I believe there is no God. It's more like a hunch or a thought. Because for all I know we could be some Alien's schoolwork project, but I don't think we are.
In any case as a human I feel like I have evolutionary drive to hold someone responsible, so again I demand whoever is behind all of that to give us those answers. But that is my evolutionary drive, not that I think there's actually someone like that. It's the conflict of evolutionary brain vs the logical thoughts brain.
These different parts in the brain can also agree to many different things, which can ultimately make me much more agreeable person, if I decide to pick one of those opinions.
But I can be very disagreeable too, because I think Big Five said it can lead to success?
As an atheist myself, I find your type of agnosticism to be overly generous to the religious theories. Do you also think that Russell's Teapot might exist or do you have a limit of unlikeliness that you draw the line at?
Saying that you know for certain that there is no god(s) is exactly the same as saying you know for sure that there is a god(s). Being agnostic is the realization that you can't be sure one way or the other. We are not omniscient and our reasoning abilities are not flawless. You might have your strong suspicions one way or the other about whether there is a god, but if you aren't certain (as many people are) I consider that as agnostic.
I considered myself an atheist for most of my life. As I got older and learned more, this shifted. These days I consider myself agnostic.
If atheism was defined as believing a specific kind of god (e.g. the “father god in the sky that created all things in 6 days”) does not exist, I’d still consider myself an atheist.
But my agnosticism comes from an acknowledgment of our fundamentally limited understanding of certain aspects of existence, and the implications of that specific lack of understanding.
It’s not as if I believe “well maybe the god of Abraham could be real after all but I don’t know” (it seems far more likely that if there’s a god, he/she/it/they are closer to being the stuff of existence than some standalone entity). It’s more that I withhold belief entirely and don’t make absolute claims that are philosophically untenable.
If we figure out how consciousness works or achieve breakthroughs in physics, I could imagine calling myself an atheist again. Until then, agnosticism seems like the most intellectually honest position.
> In practice, atheists are people who think they know there is no god.
This is generally labeled “gnostic atheism” or “strong atheism”, and only a teeny tiny fraction of people who identify as atheists take this view.
The way the vast majority of atheists use the term is as the complement set to theism. Theists believe in god(s). Atheists lack belief in gods. We don’t claim to know for certain, we just haven’t seen evidence that leads us to believe. (As you say, certainty level regarding any particular god varies depending on which one is in question.)
>Gnosticism is a collection of religious ideas and systems that coalesced in the late 1st century AD among early Christian sects. These diverse groups emphasized personal spiritual knowledge above the teachings, traditions, and authority of religious institutions.
Many atheists find a verdict of "not guilty" on the charge "that god exists". It's the equivalent of saying "I don't believe you." That's about it.
Saying "god does not exist" is a claim that itself has a burden of proof. Most people agree there is no need to provide proof that fairies and unicorns don't exist. If you think they do: show your evidence. The default position is to think they don't exist.
As for where I came from, I gotta admit I feel curious about that too, but mostly I’m just happy to be here. Real excited to see what you do next.
I do agree that it makes sense, but not because of what quantum mechanics says.
See also: https://en.wikipedia.org/wiki/Many-worlds_interpretation
And a video: https://www.youtube.com/watch?v=dzKWfw68M5U&list=PLsPUh22kYm...
Also implies that all singularities of the same mass are identical. I think this should be less bold of a statement. Let’s speculate that the more mass in the singularity would correspond to higher iterations in something like the Mandelbrot set. More of a resolution enhancement.
More if a scifi prompt than anything else to be fair.
Can you explain why you hope everything is deterministic?
But also it would be super trippy and interesting. Knowing just the mass of the universe you’d be able to peer into any time, past or present, and see exactly what happened. But then what happens around areas where people look into the local time? This happens in the show Devs. So not at all a new idea in scifi.
https://en.wikipedia.org/wiki/Cosmological_natural_selection
I don’t think it has a hypothesis for the origin, though
building on ten years of earlier research for a book on cosmological natural selection
I loved this overview on our current approaches to measure the expansion: https://youtu.be/WNyY1ZYSzoU
I really like this analogy for "what is outside of our universe", thank you
It’d be like asking why is there a North Pole? Why is there an Earth to give meaning to a North Pole? Why is there a universe for the Earth to exist? And so on until you inevitably reach why is there something instead of nothing?
> One sometimes hears the claim that the Big Bang was the beginning of both time and space; that to ask about spacetime “before the Big Bang” is like asking about land “north of the North Pole.”
Source: https://www.preposterousuniverse.com/writings/dtung/
I'm a regular listener of his Mindscape podcast, and that's where I got this phrase. I can highly recommend his podcast: https://www.preposterousuniverse.com/podcast/
- Gravity "slows" the time down, gravitational singularity should bring the time to a halt
- Suppose there is a quantum process that makes the true singularity impossible, so all black holes immediately expand right back
- Looking at it from our time scales, even if the singularity existed for a moment, it would appear that "infinite" time has passed while from the black hole's perspective, the expansion was instantaneous.
- From earth's perspective, if the singularity ever existed in a black hole, it stands to reason that when the time "resumes" from a black hole expansion, it won't fall into any of our known timelines since infinite time would have passed.
Assuming our universe eventually collapses into a few black holes, perhaps the spawn of a new universe is simply all the matter and energy of our universe arriving at a new point in... time? an infinite amount of time in the future.
Also, really mind bending to think the universe may just be an infinite series of black hole explosions with no beginning. It is because it always was.
> And we show that this rule prevents the particles in the collapsing matter from being squeezed indefinitely. As a result, the collapse halts and reverses. The bounce is not only possible – it’s inevitable under the right conditions.
Then how comes the neutron stars collapse into black holes despite obeying the exclusion principle?
One of the ways to overcome one of the levels of this degeneracy pressure is electron capture which is the opposite of a kind of beta decay. Squeeze hard enough and a proton combines with an electron to form a neutron and a neutrino.
But there are several proposed levels of degenerate matter in neutron stars, the idea being that one (final?) level of this degenerate matter is dense enough to make an object smaller than its schwarzschild radius. Uncertainty is high because we have no current methods to observe any of this kind of matter.
What goes on inside the schwarzschild radius is another mystery we don't have answers from, but there are lots of ideas with various levels of legitimacy.
Quantum physics in and around singularities or things we think are singularities is not understood.
Different exclusion principle. For neutron stars, it is the Pauli exclusion principle (IIRC) which creates neutron degeneracy pressure. Enough mass and gravity can overcome it forming a black hole. The article is talking about quantum exclusion which happens at a much smaller scale. I don't know much about it because that exceeds the limits of my degree.
There are many many reasons why this is a dumb idea and it's just as much of a paradox as any other naturalistic creation theory.
"This is not just a technical glitch; it’s a deep theoretical problem that suggests we don’t really understand the beginning at all."
"The bounce is not only possible – it’s inevitable under the right conditions."
ugh
What is preventing the collapse in this case and results in a bounce?
I can hear Sean Carrol saying, though, that:
1. We know general relativity isn’t complete, because it doesn’t take quantum mechanics into account.
2. We can’t say whether this is right because we don’t know the quantum theory of gravity.
But I don’t actually know what I’m talking about.
What specifically is meant by interior? Does this mean “within the event horizon” or something else?
1. You can have black holes inside black holes.
2. Potentially each black hole is a universe - although some are much smaller and less interesting than others.
Edit: I hasten to add that I'm not asking to undermine the research. Seems the more the merrier, there. Genuinely curious on what some of this could lead to.
What the paper actually proposes is that the Big Bang may have been a gravitational bounce inside a black hole formed in a higher-dimensional parent universe. Quantum degeneracy pressure stops the collapse before a singularity forms. From the outside, it looks like a black hole. From the inside, it evolves as a 13.8 billion year expansion. That is general relativity applied across frames.
Simply put this is a relativistic collapse model with quantum corrections that avoids singularities and produces testable predictions, including small negative curvature and a natural inflation-like phase.
It's incredible how big a 4-D universe would have to be to contain our own, even crazier if there are more levels; but our own universe could contain easily uncountable planar universes.
[0]: https://observablehq.com/@tophtucker/theres-plenty-of-room-i...
(Emphasis mine)
I haven't read the paper yet, but this sounds like a (good) summary of exactly what the article is saying. It makes me wonder what, if anything, you feel is different from the way you put it and the way it is explained in the article? As a layman they seem the same to me.
However, the comment was worded as if it meant to highlight some difference between how the article summarized the paper and what the paper is actually saying. Since I couldn't see a difference between the above poster's summary and that in the article, I was curious what I was missing.
> Penrose proved that under very general conditions, gravitational collapse must lead to a singularity..... we show that gravitational collapse does not have to end in a singularity. We find an exact analytical solution – a mathematical result with no approximations
That's incorrect: The parent universe is not higher-dimensional, it's the same good old 3+1 as our universe.
What they propose is: Let's take our good old GR, and start with a (large, dilute) compactly supported spherically collapsing collapsing cloud of matter. During that, you get an event horizon; afterwards, this looks like a normal black hole outside, and you never see the internal evolution again ("frozen star", it's an event horizon). Inside, you have the matter cloud, then a large shell of vacuum, then the event horizon.
Quantum mechanics suggests that degeneracy pressure gives you an equation of state that looks like "dilute = dust" first, and at some point "oh no, incompressible".
They figure out that under various assumptions (and I think approximations), they get a solution where the inside bounces due to the degeneracy pressure. Viewed from inside, they identify that there should be an apparent cosmological constant, with the cosmological horizon somehow (?) corresponding to the BH horizon as viewed from the outside.
All along the article, they plug in various rough numbers, and they claim that our observed universe (with its scale, mass, age, apparent cosmological constant, etc) is compatible with this mechanism, even hand-waving at pertubations and CMB an-isotropies.
This would be super cool if it worked!
But I'm not convinced that the model truly works (internally) yet, too much hand-waving. And the matching to our real observed universe is also not yet convincing (to me). That being said, I'm out of the cosmology game for some years, and I'm a mathematician, not a physicist, so take my view with a generous helping of salt.
(I'm commenting from "reading" the arxiv preprint, but from not following all computations and references)
PS. I think that they also don't comment on stability near the bounce. But I think that regime is known to have BKL-style anisotropic instability. Now it may be that with the right parameters, the bounce occurs before these can rear their heads, and it might even be that I missed that they or one of their references argue that this is the case if you plug in numbers matched to our observed universe.
But the model would still be amazing if it all worked out, even if it was unstable.
That’s not mentioned in the summary. After inflation the event horizon would not exist.
This identification happens in equations 31-34 on page 7f subsection "Cosmic Acceleration" in https://arxiv.org/abs/2505.23877
The justification looks super sketchy and hand-wavy to me, though, which I summarized as "somehow (?)".
"After inflation the event horizon would not exist."
Apparent cosmological constant viewed from the bouncing inside induces a cosmological horizon, which they identify with the black hole horizon viewed from the outside. Super elegant idea, but I don't buy that this is supposed to be true.
There will never be observational evidence on what happens on the other side of any event horizon, you'd have to cross over to the other side to see it for yourself (but you won't be able to report back your findings). There's a fun greg egan short story about that ;)
If the Big Bang was just a moment in someone else’s universe, then maybe everything we know is just one chapter in a book far larger than we can imagine.
It is the same for 'multiverse' where that is used to explain literally anything 'it's like that in this universe but not the others'.
Sure, we can get creative and explain the Anthropic Principle by mentioning the multiverse.
But none of this answers how something comes from nothing.
Not the vacuum of space and its 'quantum foam' where particles jump in from nowhere.
Because that's not 'nothing'.
One of these nothings ... such as level 9. No possibilities.
https://closertotruth.com/news/levels-of-nothing-by-robert-l...
Why do you assume there was nothing?
Is this OnlyFans ?
The title's use of the word "research," and the paper's content, suggest the idea resembles science more than speculation. But in fact, the paper has no observational evidence, nor a proposal for acquiring evidence, to distinguish it from other similar speculations.
To put it simply, at the center of a black hole is a singularity, a domain where existing theories can offer no guidance. So a new idea about singularities -- about black holes -- should suggest a testable property, to distinguish it from other similar ideas.
I say "idea" here to avoid use of the term "theory," which in science requires observational evidence to move past the realm of speculation.
Don't get me wrong -- speculations have an important role to play in science. But tendentious phrases like "research suggests" wrongly imply the presence of something more than speculation.
Recently I saw also a theory that black hole might not, in fact, exist as we thought, and may be instead something called 'gravastars', where large stars do not collapse in an infinite point but instead the mass reaches a maximum density and hardness and become sorts of empty bubbles.
Now this. It's not exactly a new idea, I remember reading about black hole cosmology 10 years ago.
Sooo... My uneducated, pop-sci fueled imagination now sees the universe as a mathematical function of a fractal looking like a shell with patterns on it, and those patterns interact or 'fold' in a way where the patterns themselves can be thought of as shells with patterns on them, and each shell creates something that, from the inside, looks like a new dimension of space or time, and what we think of as black holes are the next fold. Does that make sense?
I don't have the Ph.D physics/maths skills to work out the plausibility of any of that (or variations on that) but I've always felt I've been good at coming up with ideas.
Any physicist wants to work with me, I'm https://purpleidea.com/contact/
> And we show that this rule prevents the particles in the collapsing matter from being squeezed indefinitely. As a result, the collapse halts and reverses. The bounce is not only possible – it’s inevitable under the right conditions.
Do I understand right, that this would mean that every formation of a black hole would result in a bounce?
TARS is a new theoretical framework that fundamentally reimagines the foundations of physics. Instead of assuming that reality is made of pre-existing entities (particles, fields, or spacetime itself), TARS posits that everything that exists is, at root, a relation. In this view, the universe is a dynamic network of coherence relations, and what we perceive as space, time, matter, and even physical laws, are emergent phenomena arising from this underlying relational web.
1. Motivation: The Crisis in Fundamental Physics
Modern physics, despite its immense successes, faces deep unresolved problems:
The incompatibility between General Relativity (GR) and Quantum Field Theory (QFT)—the so-called "quantum gravity problem."
The mystery of singularities (in black holes and at the Big Bang), the nature of time, and the unexplained phenomena of dark matter and dark energy.
The lack of a unifying principle that can reconcile the fragmented domains of current theories.
TARS responds to these challenges by proposing a radical ontological shift: relations, not entities, are fundamental. This shift is not just a new model, but a new grammar for describing reality.
2. Ontological Foundations: Radical Relationalism
Core Postulate:
"All that exists is relation."
There are no absolute, isolated objects. The very identity of any "entity" (particle, field, law) is defined by its pattern of relations with all others.
The universe is fundamentally non-separable: no part can be fully understood in isolation.
This principle generalizes quantum entanglement to a universal ontological status.
Realism and Symbiosis
Symbiotic Realism: Entities and their properties are co-constituted through mutual relations. There are no intrinsic properties, only extrinsic, dynamically co-created ones.
The observer is not external, but an active node in the relational web. Knowledge itself is a process of coherent participation in this network.
3. Mathematical Formalism
3.1. From Discrete Relations to Emergent Fields
At the most fundamental level, reality consists of discrete coherence relations, denoted ξ_{ij} (or quantum operators ξ̂_{ij}), between abstract nodes.
At emergent scales, these relations manifest as a continuous coherence field ϕ_{μν}(x), a symmetric tensor field encoding the density and structure of relational coherence at each emergent spacetime point.
The emergent metric is given by: g_{μν}(ϕ) = e^{2αϕ} η_{μν}
The Symbiotic Action is:
S[ϕ]=∫d4x−g(ϕ)[12gμν(ϕ)(∂μϕ)(∂νϕ)−V(ϕ)]S[ϕ]=∫d4x−g(ϕ)[21gμν(ϕ)(∂μϕ)(∂νϕ)−V(ϕ)]
where V(ϕ) is the relational potential.
3.2. Dynamics: Coherence, Dissonance, and Self-Organization
Local coherence (ξ_l) and global coherence (ξ_c) quantify the degree of relational compatibility.
The difference Δξ = |ξ_c − ξ_l| acts as a "relational tension," driving the system toward higher global coherence.
When Δξ exceeds a threshold, critical reorganizations occur (mediated by an operator F₀), leading to emergent order, the arrow of time, and the formation of physical laws.
3.3. Quantization and Emergence
TARS aspires to a quantum theory of relational fields, where quantization applies to the relations themselves, not to fields on a pre-existing spacetime.
The challenge is to mathematically derive how spacetime, matter, and interactions emerge from the dynamics of ξ̂_{ij}.
4. Phenomenological Implications
TARS provides new perspectives and solutions to major physical puzzles:
Singularity Resolution: The regularization of black hole and cosmological singularities emerges naturally from the relational dynamics.
Dark Matter/Energy: Gravitational anomalies are interpreted as regions of relational coherence deficit, not as unseen particles.
Inflation and Cosmology: The early universe's rapid expansion is modeled as a phase transition in the global coherence field.
Black Hole Evaporation: Predicts a slower, non-singular evaporation process, leaving stable remnants.
Consciousness and Life: Interpreted as high-order reflexivity in relational networks—consciousness is a self-referential coherence loop.
5. Scientific Achievements to Date
Full mathematical formalism: Action, field equations, emergent metric, and relational potentials.
Analytical derivations: For black hole interiors, dark matter effects, and cosmic inflation.
Numerical simulations: Demonstrating the propagation of coherence fronts and self-organization.
Distinct predictions: Such as black hole evaporation profiles and singularity avoidance, differentiating TARS from standard models.
White paper and technical documentation: Comprehensive and available for peer review.
6. Meta-Theoretical and Interdisciplinary Reach
TARS is not just a new physical theory; it is a meta-framework for understanding emergence, organization, and knowledge itself. Its principles can be applied to biology, neuroscience, social systems, and artificial intelligence, wherever complex relational networks give rise to emergent phenomena.
7. Conclusion
TARS offers a radical, mathematically grounded, and phenomenologically rich alternative to current foundational physics. By shifting the focus from entities to relations, it provides a unified language for the emergence of space, time, matter, and law. Its predictions are testable, its formalism is rigorous, and its implications reach far beyond physics, offering a new way to organize scientific and philosophical knowledge.
1. Motivation: The Crisis in Fundamental Physics
Modern physics, despite its immense successes, faces deep unresolved problems:
The incompatibility between General Relativity (GR) and Quantum Field Theory (QFT)—the so-called "quantum gravity problem."
The mystery of singularities (in black holes and at the Big Bang), the nature of time, and the unexplained phenomena of dark matter and dark energy.
The lack of a unifying principle that can reconcile the fragmented domains of current theories.
TARS responds to these challenges by proposing a radical ontological shift: relations, not entities, are fundamental. This shift is not just a new model, but a new grammar for describing reality.
2. Ontological Foundations: Radical Relationalism
Core Postulate:
"All that exists is relation."
There are no absolute, isolated objects. The very identity of any "entity" (particle, field, law) is defined by its pattern of relations with all others.
The universe is fundamentally non-separable: no part can be fully understood in isolation.
This principle generalizes quantum entanglement to a universal ontological status.
Realism and Symbiosis
Symbiotic Realism: Entities and their properties are co-constituted through mutual relations. There are no intrinsic properties, only extrinsic, dynamically co-created ones.
The observer is not external, but an active node in the relational web. Knowledge itself is a process of coherent participation in this network.
3. Mathematical Formalism
3.1. From Discrete Relations to Emergent Fields
At the most fundamental level, reality consists of discrete coherence relations, denoted ξ_{ij} (or quantum operators ξ̂_{ij}), between abstract nodes.
At emergent scales, these relations manifest as a continuous coherence field ϕ_{μν}(x), a symmetric tensor field encoding the density and structure of relational coherence at each emergent spacetime point.
The emergent metric is given by: g_{μν}(ϕ) = e^{2αϕ} η_{μν}
The Symbiotic Action is:
S[ϕ]=∫d4x−g(ϕ)[12gμν(ϕ)(∂μϕ)(∂νϕ)−V(ϕ)]S[ϕ]=∫d4x−g(ϕ)[21gμν(ϕ)(∂μϕ)(∂νϕ)−V(ϕ)]
where V(ϕ) is the relational potential.
3.2. Dynamics: Coherence, Dissonance, and Self-Organization
Local coherence (ξ_l) and global coherence (ξ_c) quantify the degree of relational compatibility.
The difference Δξ = |ξ_c − ξ_l| acts as a "relational tension," driving the system toward higher global coherence.
When Δξ exceeds a threshold, critical reorganizations occur (mediated by an operator F₀), leading to emergent order, the arrow of time, and the formation of physical laws.
3.3. Quantization and Emergence
TARS aspires to a quantum theory of relational fields, where quantization applies to the relations themselves, not to fields on a pre-existing spacetime.
The challenge is to mathematically derive how spacetime, matter, and interactions emerge from the dynamics of ξ̂_{ij}.
4. Phenomenological Implications
TARS provides new perspectives and solutions to major physical puzzles:
Singularity Resolution: The regularization of black hole and cosmological singularities emerges naturally from the relational dynamics.
Dark Matter/Energy: Gravitational anomalies are interpreted as regions of relational coherence deficit, not as unseen particles.
Inflation and Cosmology: The early universe's rapid expansion is modeled as a phase transition in the global coherence field.
Black Hole Evaporation: Predicts a slower, non-singular evaporation process, leaving stable remnants.
Consciousness and Life: Interpreted as high-order reflexivity in relational networks—consciousness is a self-referential coherence loop.
5. Scientific Achievements to Date
Full mathematical formalism: Action, field equations, emergent metric, and relational potentials.
Analytical derivations: For black hole interiors, dark matter effects, and cosmic inflation.
Numerical simulations: Demonstrating the propagation of coherence fronts and self-organization.
Distinct predictions: Such as black hole evaporation profiles and singularity avoidance, differentiating TARS from standard models.
White paper and technical documentation: Comprehensive and available for peer review.
6. Meta-Theoretical and Interdisciplinary Reach
TARS is not just a new physical theory; it is a meta-framework for understanding emergence, organization, and knowledge itself. Its principles can be applied to biology, neuroscience, social systems, and artificial intelligence, wherever complex relational networks give rise to emergent phenomena.
7. Conclusion
TARS offers a radical, mathematically grounded, and phenomenologically rich alternative to current foundational physics. By shifting the focus from entities to relations, it provides a unified language for the emergence of space, time, matter, and law. Its predictions are testable, its formalism is rigorous, and its implications reach far beyond physics, offering a new way to organize scientific and philosophical knowledge.
Well, at least it does make for interesting conversations. Someone will surely milk it for Youtube content.
1. This theory requires a parent universe that can't have been formed inside a black hole. This means there must a be second "universe creation" mechanism that we can / may never know about from our child universe. For me, this doesn't really answer the true question: "How did our universe begin?" Yeah, it may the "unknown field with strange properties" but instead we get an unknown parent universe with strange properties.
2. The black hole in the parent universe must be much much bigger than anything we see in ours since it has to contain all the matter that we see. How is a black hole supposed to form that is 750 billion times bigger than the largest black hole we know about?
> requires a parent universe
Does that repeat forever? Does it lose energy in the bounce? If so, to where and how?
> The black hole in the parent universe must be much much bigger than anything we see in ours
Most importantly, you don't need everything all figured out at once to publish. Then no one would always publish. There'd be nothing to improve on. Only one publication that says everything. Till then, everything does have criticisms and is incomplete. It's good to have criticisms! They lead you to the next work!
>> Yes and no. You're not thinking about contraction. With relativity >> we can fit a 100ft ladder inside a 10ft barn.
I believe the OP was talking about mass, not linear dimension. (And if he wasn't, I am.) Unless somehow mass inside a black hole is not constant? (ignoring accretion)
Remember, mathematically, a blackhole is mass in an infinitely small point. You are dividing by 0. I don't know the answer, but if someone is saying that from the outside the apparent mass is different than from the inside, that doesn't set off any alarm bells. We literally are talking about Dr Who style "it's bigger on the inside". Even the ladder example should make you think about mass. Without relativistic effects the mass inside the barn is only part of the ladder. With relativity, the whole ladder, and thus mass, is inside. So yeah, weird things happen.
Things don't get more mass, they just take more energy to accelerate which looks a lot like more mass.
It doesn't imply for example, a high speed mass would cause more gravitational attraction than a slow one.
If that was the case, a black hole would be even worse as it accelerates matter towards itself and it gains "bonus mass"
Unless the theory also breaks mass and information conservation, the star that gave birth to our black hole must have been as massive as our entire universe.
I doubt we have any theory how a star that size can have formed.
2. We don’t know whether our universe is big or small compared with other universes. We don’t know whether, or how, it makes sense to compare sizes between universes.
Big Bang is arguably the biggest speculation in modern science.
There are many models of black holes, such as the Schwarzchild solution, that have an area of "asymptotically flat spacetime" which is, from the viewpoint of our universe, part of the black hole. That something happens around the singularity that creates this new universe doesn't sound that crazy.
If our universe is a child of another universe and that is a child of another universe and so forth it fits into the kind of "multiverse" model that addresses issues such as "why does the universe have the parameters it does?" Either there are a huge amount of universes such that we're lucky to be in one we can live in, or there is some kind of natural selection such that universes that create more black holes have more children.
As for the relative size of the parent black hole, conservation of energy doesn't have to hold for universes in the normal sense. One idea is that the gravitational binding energy of the universe is equal to the opposite of all the mass in the universe such that it all adds up to zero so we could have more or less of it without violating anything.
To those who say "oh but if this parameter was slightly off, that thing I subjectively decided to pick wouldn't have happened!":
How would you know that this universe could exist in any other way? Wouldn't things just stabilize into certain frequencies and lengths after some time?
To me "fine tuning" isn't really a conundrum, it is just question begging and you don't need to wish it away with multiverses.
Nitpick: We couldn't be anywhere else, except nonexistent.
To me it's prima facie a hollow explanation. I get that some models, like eternal inflation or certain cyclic cosmologies, entertain the idea of an infinite past or blur the standard arrow of time... but how does pushing the origin question back indefinitely actually resolve anything?
- We have a parent universe we will never be able to observe.
could be a true statement.
The "infinite sequence" part is just a likely implication, it isn't necessarily true. We would need information we can't access to find out.
I agree with you, though - causal explanations are compelling and confer a sense of certainty and humans seem to like that, but it doesn't make them necessary.
If it's expanding, then it was smaller earlier. Asking about the far past is a natural reaction, and the Big Bang theory is a pretty good attempt at explaining that.
{..insert here a statement...} maybe yes but also maybe not {...clickbait things here...}
In my view, there is one universe. We are in it. It cycles from maximum to minimum condition endlessly. This cycle is much longer than any entity lifespan and for any entity, the current state is THE state for them, and all they will know and become.
What does it expand into?
Nothing. Space itself just gets bigger and smaller over time.
No beginning, no end. It all just is.
Yes, it produces a testable prediction, but seemingly based on a mathematical assumption derived from our observed cosmic radiation background.
> This lower bound follows from the requirement of χk≥χ∗≃15.9 Gpc to address the cosmic microwave background low quadrupole anomaly
As a lay reader, can I assume that no scientist would publish a theory with mathematical circularity (at the heart of the prediction)? I sure can't verify it myself.
Wow - like this anti-humanist prejudice is totally 1993. And not in a good way.
two-photon collision experiment has permitted humans to hypothesize a simpler explanation to the beginning of the creation of more electromagnetic forces, which obviously behave differently than how are bodies were designed to receive them i.e. evolutionary biological bandwidth...
Glad to hear that. I'm looking forward to any theories how to convert time to space (and back) ..with orthogonal universes/singularities ?
It was featured on Event Horizon (john Michael godier)?
thrill•8mo ago