An old theory of quantized gravity is gaining new life
quantamagazine.org
quantamagazine.org
Would a person interested in an article about quantum gravity not be familiar with the term asymptotically?
/a-sim-TOT-i-klee/
I feel exactly the opposite way.
<Rant>
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.
</Rant>
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.
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.
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.
> 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.
/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.
Whether or not the pronunciation is valuable information given that the communication method is again text remains to be seen.
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.
And that is a UV fixed point.
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.
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.
In that case what are our options?
So there may be issues trying to use a particle theory to describe something that may be more fundamental than the other fields.
But IANAP, so this could be completely wrong.
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, 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.
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.
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.
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.
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.
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.
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).
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.
BTW: Stress on ax-iomatic, as in axis?!
No, because if it was then there would not be negative electric charge, and there is.
Won't it cause the surrounding atmosphere to cave in to the negative-gravity source as well?
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.)
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.
1] https://en.wikipedia.org/wiki/Le_Sage%27s_theory_of_gravitat...
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!
Be careful.
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.
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.
However, gravitational waves do carry energy.
Gravitons, whatever they are, must be some very tricky things.
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).
So to answer your question: the same way they would normally.