It isn't. The problem with a vernacular pronunciation guide is that you need to think about ambiguity.
/a-sim-TO-ti-klee/
is a much better syllable break, but /TO/ is likely to be mispronounced /'tu:/. And /TOH/ could be interpreted as /'toʊ/. So /TOT/ splits the difference between syllable break and pronunciation for (imho) maximum clarity.
I wish people would use the IPA instead of their absurd ad-hoc systems. I learned IPA at school, and it has served me well.
All the pronunciation systems based on some other language are unreliable and idiosyncratic. And English, with its near-absence of reliable pronunciation/spelling rules, is particularly ill-suited.
That's why people use their ad-hoc systems. Because many many many people don't know IPA. It's so far removed from English and uses so many letters that don't occur in English that it's close to being a completely different language.
The word "ɪn·tərˈnæʃ·ə·nəl" may make complete sense to someone who knows IPA but to to the many people who don't, it's complete gibberish.
> That's why people use their ad-hoc systems. Because many many many people don't know IPA.
I was disagreeing with parent's claim that ad-hockery was better than IPA. Nothing more, nothing less.
However if ad-hockery is the best someone can do (I say this without snark), then fine. Certainly better than nothing.
> It's so far removed from English and uses so many letters that don't occur in English that it's close to being a completely different language.
English is far removed from my native language, so either way I have to learn a pronunciation system (and the English one is... special).
While we're at it, do we use pseudo-American or pseudo-British pronunciation in our ad-hockery? Pseudo-US-East-coast or pseudo-Southern-US?
I think ad-hockery provides a trap in that it gives a false sense of security. You think you know to pronounce something, but if you actually try, chances are your native speaker conversation partner will go ¿que?
> The word "ɪn·tərˈnæʃ·ə·nəl" may make complete sense to someone who knows IPA but to to the many people who don't, it's complete gibberish.
I agree that it looks like gibberish to those who don't know IPA. But I'm honestly not sure "intaneshenel" (or "intönäschänäl", or whatever) is better. For me at least, it's equally confusing.
As an aside: making up pronounciation if it's of little relevance to what you're writing is one thing. What really grinds my gears is language books (or, say, the language section of guide books) that make up their funny ways of writing pronunciation. They might use that same amount of effort to teach the basics of IPA, which is about the same amount of effort, and provides the reader with something lastingly useful.
They even write multi-page explanations, complete with examples, on how to interpret funny charecters in their script. I remember the absurd contortions the Lonely Planet Germany guide went through to explain umlaut sounds to people in terms of English words, and then coming up with ways that weren't the IPA to type those sounds.
The aim is communication. When the aim is very precise communication between knowledgeable parties, a technical language is reasonable. Expecting people to learn that language before they're allowed to have even a basic discussion is a recipe for existing in your own irrelevant bubble.
It is human tendency to think that the things that you know should be known by everyone, and the things you don't know are probably not worth knowing.
On IPA specifically, it can often be overspecified, particularly with regard to vowel sounds and vowel position in the mouth. It isn't clear when a vowel position is determined by accent or by the word, or whether a vowel becoming a shewa is idiomatic. By relating to similar sounding lexemes (or obvious parts thereof), vernacular pronunciation guides have fewer problems in that regard. IPA is easy to learn a little of, but it's a deep deep well to throw people down when all they want is a glass of water.
> The aim is communication. When the aim is very precise communication between knowledgeable parties, a technical language is reasonable. Expecting people to learn that language before they're allowed to have even a basic discussion is a recipe for existing in your own irrelevant bubble.
> It is human tendency to think that the things that you know should be known by everyone, and the things you don't know are probably not worth knowing.
You're over-interpreting what I said, and being not nice about it by assuming a hostile or superior stance on my part.
I didn't expect anyone to do anything. Parent stated that pseudo-English was better than IPA, and I disagreed. The end.
Theoretically, yes. Asymptotically is one of those words that you often read about, but rarely hear in speech. There are plenty of words I come across in text that I understand the meaning of, but often am not familiar with the correct pronunciation as nobody I interact with in daily life use them. I can see this one falling into that category quite easily.
Whether or not the pronunciation is valuable information given that the communication method is again text remains to be seen.
I was amazed by this too. Why focus on how one pronounces it rather than the mathematical properties of asymptotic behaviour (i.e., that one gradually approaches but never reaches something)?
Yeah, this is a little odd. But in the writer's defense, I read a lot more than I speak, and I often comically mispronounce a useful word when I have to use it in speech, so while I'm familiar with this particular word, I do wish writers would do this with words a little more often than they do.
Honestly my brain read it as "asymptomatically" at first... Also why deprive a reader who is not familiar with the term? Does it really hurt you that it is included?
> "In other words, gravity would be asymptotically safe if the theory at high energies remains equally well behaved as the theory at low energies. In and of itself, this is not much of an insight. The insight comes from realizing that this good behavior does not necessarily contradict what we already know about the theory at low energies (from the early works of DeWitt and Feynman)."
But what are the actual expected changes at high energy that would differ from what is seen at low energy?
I kept waiting for her to explain what differences would be observed if this theory is correct, but she never did.
The key feature she never names is known as a "UV fixed point".
UV = UltraViolet, which in this context simply stands for "high energy".
Fixed point... for that you need to know that the effective values of coupling "constants" aren't actually constant in quantum field theory; they depend on the interaction energy (i.e. how hard you bang your particles together). So they are called "running" coupling constants. Yes, it's contradictory.
That dependence on interaction energy is described by differential equations (known as the renormalization group flow equations, which may sound impressive but is actually a misnomer), which you can integrate to see how a coupling measured in the lab at low energy will change when your descendants finally get enough funding for a larger accelerator.
One interesting behavior is the coupling going to zero when you increase the energy towards infinity. That happens in QCD: counterintuitively, the harder you bang quarks together, the less they affect each other (via QCD, that is; they also have other kinds of interactions which behave differently). So QCD is called "asymptotically free": in the limit of infinite interaction energy, as far as QCD is concerned, quarks are free particles, completely unaffected by each other's presence.
In asymptotic safety, as opposed to freedom, the coupling does not go to zero as you increase the energy; instead, the rate at which it changes goes to zero, and it does so at some finite value of interaction energy. So, as you crank up the interaction energy toward that value, the coupling constant "runs" slower and slower, and once you get there, it stops "running" altogether. From there on, you can raise the interaction energy all you want, and the coupling constant stays... constant.
This helps, but doesn't say what the theory says gravity will do at higher energy levels.
To me it seems to imply gravity will get weaker at higher energies? Something about that makes me feel like it violates conservation of energy, so maybe that's not it.
Having the theory behave at all, in the sense that calculations do not result in infinities, is big enough.
But there is a prediction which has been made pretty much since Reuter et al. picked up asymptotic safety again in the mid-2000s, and which is directly related to the way it supposedly tames those infinities: at higher resolution, i.e. when spacetime is probed at higher interaction energies, its dimensionality is reduced, going from 4 at the macro scale to 2 at the microscopic scale [1].
Also begs the question of how that reaction could even take place if gravitons are totally unreactive with anything other than their source - mass. How would you accelerate a graviton. Gravitons always move at C just like light. Do we have any idea what kind of production and annihalation products will give us gravitons?
Just a guess - dark matter/energy might be the only way to create a graviton without associated mass generating it. That is..the pair production of a virtual dark photon and a graviton.
I'm not sure I see any real change in the status of asymptotic safety. It's a hypothesis. Proving it directly is next to impossible. (Except in spacetime dimension <= 3, when the theory is topological, making the assertion a triviality.) Testing it experimentally is unlikely; the constraints it implies are pretty weak. Nonetheless there are some people working on it, and while their ideas have some merit, they haven't yet caused the physics world to pay drastically more attention.
Also, it's unwarranted hype to call asymptotic safety 'an old theory of everything'. It's explicitly not a theory of everything. It's only about gravity. Couple it to the Standard Model, and you still have a theory which breaks down at the hypercharge and Higgs Landau poles.
I'm not a particle physicists by any means, but doesn't any theory of gravity have to deal with 'real' infinities at high energies from the physics we already know?
We have some idea that black holes are a type of singularity (something that could possibly called an infinity). With E=MC2 we have an idea that if you apply enough energy to a particle it can become massive enough that it becomes a singularity itself.
A singularity popping out of the math is almost always an indication that something else is going on.
According to general relativity, at the center of a black hole there might be some kind of "singularity" - but in reality what that means is GR is probably inadequate, when used alone, to describe the center of a BH.
"Singularity" really means "your math broke and you need to fix it" by bringing in another theory that can fill in the gaps - or, rather, extending the current theory in a way that eliminates the division by zero.
The issue is not only about mass. Any mass could form a black hole, the main point is about mass density, and that's not trivial to obtain.
That aside, real infinities is a vague concept. What's important is that any theory of gravity has to deal with the fact that the current understanding of classical gravity and quantum field theory make (when you combine them) a theory that has problems at the Planck scale. Those are problems that any theory of quantum gravity or every theory of everything have to deal with.
But it doesn't mean that those potential theories would have any infinities. Such a theory, though, has been very elusive.
With the exception of string theory, which is the leading theory in terms of its success, most theories tend to have fundamental problems. String theory research is certainly not complete, but it's in my opinion currently the best shot we have. Online, and in academia, you can find lots of very opinionated discussions about it, which include aspects of testability, predictivity, etc. which means that some people really dislike string theory and prefer other approaches.
No, not really. A singularity in a quantized theory would simply be a place where gravity is strong enough that you can't move more than a Plank distance away from it.
I think the author completely glosses over the fact that Loop Quantum Gravity actually does make predictions, and could provide the explanation for fast radio bursts.
Also, the theory is so intuitive and follows such a straightforward logical path from Quantum Mechanics and Relativity, that I would be incredibly surprised if it wasn't the theory closest to actual reality.
Has anyone (sane) ever theorized that the ripples in spacetime in some cases may have existed before the masses of particles (ie. planets / stars) arrived at those locations?
Gravity is measurement of the distortion of space, caused by mass. It is an emergent property. The more massive something is, the more its gravity will distort the space around it.
So, a small piece of rock that you can hold in your hand, will cause a gravitational ripple in the space surrounding it. This is similar to how the Earth causes a gravitational ripple in the space around it, and it keeps us grounded to the ground. But, the Earth causes a much bigger gravitational ripple, than a small rock.
And we as humans, are grounded to the Earth, as if we are at the bottom of this massive and invisible whirlpool. We cannot see it, but this whirlpool is rotating all around us, and we cannot get out. It is easy for us to move around horizontally, but it is very difficult for us to move vertically. Unless we can move horizontally so fast, that we can reach escape velocity, and then, we orbit the Earth.
That said. What is gravity? Why does mass cause a ripple in the space around it?
I wonder if gravity is just some type of neutral electro-magnetic force. Kind of like the magnetic field lines that you see with the North pole and South pole. But instead of being magnetically charged, it is neutrally charged, and it affects everything around it equally.
Or, instead of being magnetically charged like the North or South pole, it is gravitationally-charged, and the direction points in only one way, into the center of your massive object. And unless you are moving faster than that massive object's escape velocity, then you will always be stuck in that object's gravitational ripple.
If we can truly understand what is gravity, then I wonder if we can create a counter gravity. Like, in your spaceship, if you can create a negative mass above you, then it would cause your spaceship to act buoyant in the planet's atmosphere. And you can use thrusters to move around vertically, as easy as you can move around horizontally.
Or, maybe you can create a temporary blackhole above your spaceship, and instead of your spaceship falling into the gravitational ripple caused by the Earth, then it becomes attracted to the gravitational ripple caused by your blackhole. And this causes your spaceship to rise, and defy the Earth's gravity.
Anyways. I'm not a gravitational physicist. Maybe I should take this idea, and write a novel. There has been much worse Sci-Fi ideas created, like Time Travel, or the ridiculous many-worlds-interpretation theory of quantum mechanics.
From a physics perspective, the many-world, as ridiculous as it sounds, is a more sound theory (believed to be correct by some top physicists) than negative gravity.
The explanation of why gravity is only positive is a complex one, but physicists believe it's almost axiomatic.
This doesn't mean that you can't have repulsive type of effects, similar to one of the contributions that's believed to make the universe expand more quickly than with the simple 4 fources (often called fifth force, maybe related to dark energy, and to the rate of the universe expansion acceleration).
PS.
There are a number of Sci-Fi stories that use this idea, including a famous one from Asimov, in which if I recall correctly the normal gravitational force was working negatively when traveling in FTL speed. Obviously that seemed fishy but the book was cool (Nemesis).
> The explanation of why gravity is only positive is a complex one, but physicists believe it's almost axiomatic
Isn't that a consequence of relativity, the speed of light being constant by definition? I'm not sure that makes any sense, though, what is the physical unit of gravity N? Jf you mean classical mechanics, than there has to be a negative counterforce by the three axioms of newtonian mechanics and it's just a question of frame of reference.
The trouble with this is that an electric field causes exactly the same observed effects on an oppositely charged particle.
Why would an electric field cause this by one mechanism, and gravity by another, when the observed effect is identical?
> then I wonder if we can create a counter gravity
You can not create counter gravity any more than you can create counter electric field. What you can do is move two charges apart.
To do that with gravity you would have to find a way to make double the gravity in one place, and negative gravity in the other, and then separate them.
(Creating counter/negative gravity directly would violate conservation of energy.)
I think it is relevant to consider gravity from a more abstract standpoint as well by looking at Le Sage's theory and particularly Hyugens' comments. [1]
Whether gravity is mediated by a graviton, and the intricacies that QM brings to bear, one interesting idea I took from the above hundreds of years of thought on the subject -- gravity may be a pushing force mediated by constant spherical wave emission (quantized as the graviton if necessary) from all mass/energy. Since every bit of mass-energy is releasing gravitons, the whole of space is rather isometrically filled with gravitons. The reason two objects would then appear to attract via Newton's inverse-square law is one of a shadowing effect. The graviton would apply a pushing force normally to any mass-energy it interacts with, and therefore any blockage/shadowing of one object by another, would end up looking like attraction.
Le Sage's theory is more exacting and supposes gravitons are of similar substance to regular matter. I don't agree with most of these notions but what I said above is what I gained.
This is one of the many kinetic theories of gravity. It's very old. No scientist nowadays believes that kinetic theories could really work in this realm. This is mostly of historic interest only.
I'm aware of that-- but no one is sure about how the graviton operates. So though the kinetic part might not be very realistic or all that relevant anymore, the other parts still are.
Just as there is a huge difference between Maxwell's laws and QED -- the same gap lies with relativity and the graviton. Knowing the gravitational field as full fidelity partial differential equations based on the stress energy tensors is a great achievement. But it alone does not tell the full story as to how that field is mediated. Just as EM is mediated via virtual photons, we wish to know more..
I just want to point out that, in my experience, "alternate theories of gravity" and especially those derived from a kinetic basis, tend to be a field that's extremely ripe with crackpots and pseudo-scientists. This is because what tends to happen is - people take some simple math, low-level enough that they can comprehend it, and apply it to this very intricate reality, hoping to strike gold somehow. The kinetic model is simple enough, and understood well enough that you could use math that's accessible even to those who are not actual scientists. Of course, it's never worked. It's a very, very common scenario.
Not that i understood much of what you just said, but you're the first person I've seen say gravity is a push force, so i have a question.
Does it me any sense to say mass repels spacetime? So imagine a spring on the surface of a massive sphere. Imagine that you compress the spring and release it. The spring would compress outwards, the sphere not moving (especially if an another antipodean spring was set up with a compression release cycle occurring at the same time).
What if spacetime was like that spring, constantly being 'pushed' away or repelled from mass as it tries to return to an uncompressed state . The local effects would seemingly be the same, objects would travel the same curved paths through spacetime around the sphere as they would if mass was attractivly warping spacetime. Or perhaps we xould set up the conditions so that was so.
Maybe ive misunderstood, but in most depictions of gravity its a point like a bottom of a well that's sort of stretched the 'rubber sheet' of spacetime. I know it's just an analogy but almost all layman explanations show spacetime elongating as it moves closer to the mass, the elongation depicting the 'warping' of spacetime. It's possible the real maths tells a more accurate story, but to me the more correct mental picture would be to think of circles around the mass spaced at distances where crossing between them takes time=1. For the outside observer it seems time slows as you draw nearer the mass, that would suggest the circles become 'closer' or you'd cross more space per unit time. It would also suggest the outside observer would see you eventually slow to a stop but locally you continue to accelerate along the curved spacetime, so it doesn't seem to violate special relativity.
I'm not sure if mathematically space and time are treated separately, but if they're the same then thinking of mass as repelling spacetime 'outwards' from the surface of the mass seems to still work but might explain on larger scales where some of the expansion of space comes from - i.e. mass repels spacetime but the curvature this creates causes other mass to follow paths through spacetime that appear to make the two masses attract each other.
I get that im no doubt wrong but ive not seen anyone adress this possibility (probably because it wrong!) but id be interested to hear where it breaks down, as i dont see it!
There's no particular need for a special explanation of how particle exchange could produce an attractive force: as unlikely as it seems in classicical physics, it's how the forces (electromagnetic) arise in QED. The exchange of virtual photons can transport momentum any way you like.
'Exchange of virtual photons' is a metaphorical expression used to describe artifacts of perturbation theory, it is not necessarily a real process. There is no widely accepted model of what really happens on microscopic scales, we only have equations and those are often replaced by simpler perturbation scheme. So, explanations of attractive force are welcome, Le Sage - type models including.
>There is no widely accepted model of what really happens on microscopic scales,
There's no experimental reason to come up with one - virtual photons work, which means anything else is at this point a matter of philosophy. That's not to cast off philosophy, of course.
Virtual photons work in a very limited way (metaphorical language describing perturbation theory). Physics outside of applicability of perturbation QED (bound systems of charged particles, gravity) is not a matter of philosophy.
A graviton would have to be both massless and energyless. Thus it would be unaffected by gravity.
It also means it can not have a "frequency" like light does (because lacking any energy there is no frequency to change).
It must also always move at the speed of light, and could not exist at any slower speed. (Because to slow down, would imply a change in its energy, which it can not do.)
But that means it can't interact in a way that is detectable, other than gravity.
Because you can not give it energy, you can also never create it artificially. If you did, you would be creating gravitational force out of nothing, which is impossible because it violates conservation of energy, and you can not pay for that violation because you can not give it energy.
It's pretty much the ultimate impossible to study particle.
This comment is almost completely wrong. It muddles together classical and quantum reasoning in any incoherent way.
Gravitons are best understood as the quanta of the effective qft governed by the Einstein Hilbert action. This mathematical model is the universal low energy approximation to any quantum theory that reduces to general relativity.
Gravitons need to be massless. They need not be zero energy. They can indeed be associated with frequency. They do couple to gravitational backgrounds and to other gravitons. You can crate them just like any other field quanta. The barrier to studying gravitons the way we do photons is that they couple very weakly to other systems.
How would that work exactly? First of all it means they could not escape a black hole, since they would be carrying energy out of it. It also means they would not travel in straight lines, since by carrying energy, they are subject to gravitational force, and boy of boy what a mess that would make of things if the gravity carrier was affected by its own gravity (or even the gravity of the neighbors).
Second when the graviton "landed" it would have to transfer energy. If they only act via gravity, how would you transfer energy to or from them?
And then if they carry energy, then what, energy is constantly streaming out of every particle in the universe? Or are you proposing two kinds of gravitons, those that carry energy and those that don't?
> They can indeed be associated with frequency.
Really? So how would their measured effects vary as their frequency varied?
Are you confusing gravitational waves with gravitons? The two are not the same.
> You can crate them just like any other field quanta.
No you could not because if you did you would be creating gravitational force out of nothing, which is impossible (violates a whole bunch on conservation laws).
Its very likely that gravitons are not affected by other gravitons -- just as photons generally do not affect other photons unless at very high energies. This is the case for typical bosons.
So to answer your question: the same way they would normally.
Would a person interested in an article about quantum gravity not be familiar with the term asymptotically?