Do We Need a Theory of Everything?
backreaction.blogspot.com
backreaction.blogspot.com
I'm disappointed that she trots out the tired old "zero sum game" rhetoric. I work on small-scale experiments, a field that Sabine portrays as starved of funding because of string theory. But that's not at all how funding actually works. Generally, all of our boats rise or fall together.
String theory is so distant from my field that defunding it and expecting funding for me to rise is like defunding pharmacology and expecting an immediate revolution in palaeontology. Removing funding from one subfield doesn't move it to your favorite field, it just removes it from science in general.
I however think she misses the point by constantly taking string theory as the sole example of bad science..
Disclaimer: I a former string theorist who has worked in many other scientific fields.
When you have a couple million tied up in lab equipment it's easy to divert some to grad students to keep it running but us theory folk were switching projects every couple years just to keep the lights on as it were
Please could you quantify this a bit? The competition for grants seems to be fierce. It's hard to see how such a competitive game is not close to zero-sum.
The question is: As scientists and civilians,
1) how to we model/quantify the opportunity cost of 50 years of String Theory?
2) What was the expected value of String Theory (what promises were made?). What has been the ROI?
Hypotheses: What string theory did, among other things, might have been:
1) crowd out the market for ideas.
The perception was created by the media and within academia,that String Theory was/is the hottest idea available. Arguably humanity's most brilliant theoretical physicists and mathematicians seem to have been seduced/compelled into spending their lives working on it. Perhaps one might quantify how many graduate students ended up not exploring other ideas because of the primacy of string theory.
2) caused a perception that physics research is cheaper than it is, effectively reducing the cost expectation in the market.
If string theory is the best idea, and it is purely mathematical, then a university or institution could easily claim to have a cutting-edge physics department, not by funding infrastructure for expensive experiments, but by hiring a string theorist. This in turn might lead to graduate students who can only be trained in string theory. Other institutions might be induced to reduce their costs to the level of string theory institutions/departments. If String Theory is the best idea, how do I justify spending 100x more money than the String Theory department in order to run experiments or train graduate students to do experiments or even work on their crazy new ideas?
3) Lowered the standards to which Physics is held.
If the hottest field in Physics is not required to have any relation to reality, and requires no physical evidence by which ideas are tested for almost half a century, then one might convince themselves that physics can be done purely abstractly, rather than as physical science. For the entire field of Physics to be led in this way, is terrifying.
If you want to understand something about high energy physics funding, a good starting place is the DoE's HEP budget. https://science.osti.gov/-/media/budget/pdf/sc-budget-reques...
Headline numbers:
* FY 2021 request: $818M
* amount going to all theory /computation: $122M
* amount going to 'Theory': $30M
I think your worries about string theorists leading the physics community astray are rather overblown. If it was going to happen, it would have happened twenty years ago, when string theory was at the apex of its prestige. What you generally saw was that places like Rutgers would go from having half a dozen theorists out of a department of 60 physicists to having a dozen theorists out of a department of 66. But the real physicists weren't corrupted or crowded out. They just went right on doing science.
As for the human capital question, it seems absurd to me to call string theorists the 'most brilliant' and then try to dictate what they should work on.
Funding is relevant. Tenure, graduate students, postdocs etc, all cost money. That money has to come from somewhere. Money is intimately tied to the human labour/capital question because there's a bijection between time and money. One of my main questions was: how do we measure this cost and reason about it in order to understand the past 50 years of dismal results and make reasonable decisions about the next 50 years?
> As for the human capital question, it seems absurd to me to call string theorists the 'most brilliant' and then try to dictate what they should work on
What is absurd is to claim that questioning the results of brilliant men and women is absurd. They are not gods to be worshipped blindly. In a startup, would it be absurd for me to question my co-founder and his team's results even though his IQ is 2 standard deviations beyond mine? Let's look further back for a sloppy analogy: is it absurd to criticise Newton's study of alchemy? Was it absurd for his contemporaries, rarely his intellectual equals, to question the results of such studies?
What I want from this debate, is a rigorous way to account for the past 50 years of string theory in terms of human intellectual labour cost, general opportunity cost, and return on investment.
You seem strangely hostile and defensive. But what I'm looking for is merely for the math to speak for itself so that the debate can be settled once and for all.
I don't have anything at stake here, personally. I am not a string theorist, nor am I dependent on grant funding. But I've worked in and out of academia as a scientist, and it offends me to see you play-acting as a critic of science without even understanding the lay of the land.
That's an assumption on your part, one that is both incorrect and unfortunate. (as far as theoretical physics is concerned.)
Embarrassment, however, is largely irrelevant when trying to understand anything in a systematic way.
> and it offends me to see you play-acting as a critic of science without even understanding the lay of the land.
Offendedness. Well, we simply have different experiences and perspectives within academia. We see the land differently. If that's your threshold for offence then life must be difficult indeed. I don't envy your position. If it will somewhat assuage your being offended I should tell you that, as a mathematician, I champion science above any other human activity. But who I am and what I do should be irrelevant when testing hypotheses.
For anyone who really wants to dig deeper but still get 'noob' explanations, PBS Space Time on youtube[0] is my goto.
Black holes was where I started and boy did I get sucked in.
[0] https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g
At times, I'll think I understand it. Come back 6 months later having a bit more understanding of related topics only to realize I understood absolutely none of the original video and am just beginning to get it =/. Seemingly innocuous sentences carry insane amounts of information (i.e. Do anything to a blackhole and the surface area never decreases except in Hawking Radiation)
The topics do appear jump around a lot, but there's method to the madness. Topics such as Blackhole/Thermodynamic entropy require foundations that appear unrelated at first.
Sure, they have video lists[0] to help but I've rewatched this one so many times.
> they would present string theory more or less as fact
To be fair, they have a why ST is right[1] and wrong[2].
As you can tell, I'm a SpaceTime fanboy.
[0] https://www.youtube.com/playlist?list=PLsPUh22kYmNCHVpiXDJyA... [1] https://www.youtube.com/watch?v=iTTa9YcTe1k&list=PLsPUh22kYm... [2] https://www.youtube.com/watch?v=IhpGdumLRqs&list=PLsPUh22kYm...
I'd much rather have channels like this that welcome actually getting into the details a bit, rather than the hundreds of channels that have broad, surface-level facts of a subject lazily combined with some stock-footage.
We need to unify them because there is obviously a missing link between the two theories (QM and GR), since spacetime is one and the same and there are properties defined in one theory that clearly affect the other one (but we don't know them yet).
But then the author seems to make a point of that a ToE has to be a GUT with gravity in it and that might not be how nature works?
Which I agree with but I would not have used that semantics of ToE. I think most physicists at this point would settle for any logical merging of gravity with the QFTs that is consistent even if it postulates more free parameters and not less :)
Anyway, just a nitpick on the terminology.. just seemed a bit click-baity (but I'm sure that was not the intention).
> There is no reason that nature should actually be described by a theory of everything. While we *do need a theory of quantum gravity to avoid logical inconsistency in the laws of nature, the forces in the standard model do not have to be unified, and they do not have to be unified with gravity. It would be pretty, yes, but it’s unnecessary. The standard model works just fine without unification.
We don't need the theories to be unified for them to be consistent. Putting all our efforts into that unification could actually be leading us astray and postponing the day when we've figured out how they're consistent.
Is this really true? Perhaps we can make this critique of string theory but what about other cases?
On the other hand, I think you could argue that Lagrangian and Hamiltonian mechanics were developed for aesthetic reasons, and these both proved influential for twentieth-century physics.
If you want to analyze the effect of one planet on the time evolution of another planet's orbital parameters, Hamiltonian mechanics is the formalism to work in.
Edit: Wow, fast downvotes! Sorry, I'll add another paragraph: The reason why we cannot use quantum mechanics (QM) or general relativity (GR) alone to explain the color of gold is because we know that the color comes from photons being emitted by electrons, as in QM, but the electron orbitals are distorted as if the electrons were moving at a serious fraction of the speed of light, as in GR. I think that this flatly contradicts her when she says:
> So far, this is a purely theoretical problem because with the experiments that we can currently do, we do not need to use quantum gravity. In all presently possible experiments, we either measure quantum effects, but then the particle masses are so small that we cannot measure their gravitational pull. Or we can observe the gravitational pull of some objects, but then they do not have quantum behavior. So, at the moment we do not need quantum gravity to actually describe any observation.
The color of gold, the liquidity of mercury, and even the ability of lead-acid batteries to turn over car starters are all everyday observations which need both QM and GR to explain. But, as she correctly notes, we can't put QM and GR together yet! So we do need some sort of quantum gravity.
[0] https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry
> Physicists would much rather have all these forces unified to one, which means that they would all come from the same mathematical structure. [...] At the energies that we have tested it so far, the symmetry would have to be broken, which gives rise to the standard model. This unification of the forces of the standard model is called a “grand unification” or a “grand unified theory,” GUT for short.
> What physicists mean by a theory of everything is then a theory from which all the four fundamental interactions derive. This means it is both a grand unified theory and a theory of quantum gravity.
I don't quite agree with Wikipedia [0] on this; they say:
> Unifying gravity with the electronuclear interaction would provide a theory of everything (TOE) rather than a GUT. GUTs are often seen as an intermediate step towards a TOE.
We all have different opinions on this terminology, it seems!
Special relativity and general relativity are two very different things. Don’t conflate them.
http://backreaction.blogspot.com/2020/07/do-we-need-theory-o...
Theory: When humans fix one problem they are likely creating another problem.
I came up with my theory when I read about Norman Borlaug and how he developed GMO semi-dwarf wheat which is purported to have saved a billion lives from starvation.
But people now blame GMO crops for all manner of problems like unhealthy gut, Autism Spectrum Disorders, gluten sensitivity, etc.
In sum, we're just trying to do the best we can, and we can't see all the possible consequences of our actions.
This is the main reason why humanity at large does not have perfect knowledge of things such as universal forces, exact nature of universe, ability to predict random events and so on.
Though, if a very long lived human were to become an expert in many different fields, that could also be conducive to innovation.
I have strong objections to this theory/thought.
You'll have to describe to me how this mechanism works in greater detail because even within my personal lifetime, I do not have perfect anything for anything and I have no clue on how living longer helps that particular problem.
Let's say I throw a rock in a parabolic curve in a plain field. Humans can predict exactly where it will fall. This is because humans know everything about gravity, mass, etc.
However, we cannot predict when and where exactly will a random meteor fall. This is because we do not know exactly everything about the universe and the various forces of universe.
My thought is that a lot of humans might have understood more about those forces in the past but were unable to effectively pass that information for the next generation to build upon. This could be simply because the cognitive prime of the two generation overlaps for a relatively short period of time.
Now had the humans lived long enough to cross some threshold of effective communication and longer overlap of cognitive peak between generations, they could have better able to pass their intuition, experience, thoughts, ideas to the next generation. In other words, there would be less loss of information/knowledge which would be just enough to fill the critical gaps to know everything about the universe.
Knowing everything about the universe would enable them to predict everything precisely just as in the example of a parabolic throw of a rock on earth's surface.
> I throw a rock in a parabolic curve in a plain field. Humans can predict exactly where it will fall
No, we can predict this within a margin of error. That margin of error might be small for simple cases but if you add some gusty wind, some rain etc. it can increase quite rapidly.
> However, we cannot predict when and where exactly will a random meteor fall
We can also predict it within a margin of error just like with the rock in the plain field. But you are comparing an event that last a few seconds (from the throw to the landing) to an event that may last years or more depending on what kind of meteor you are talking about. So of course over the span of years, even a very small imprecision turns out to have very big consequences.
If you could throw the rock hard enough so that it orbits earth for some years before coming back, it would be as hard to predict where it would land.
> Knowing everything about the universe
How could you possibly know everything about the universe when some events are purely random?
> In other words, there would be less loss of information/knowledge which would be just enough to fill the critical gaps to know everything about the universe.
So you are saying we happen to live at the exact time, where, had we not this knowledge transfer issue, we would know everything? This is quite self-centered. Which also simply mean that in a relative close we will now everything, which seems quite ludicrous.
This sounds incredibly unlikely. When do you imagine that these people lived? What data were they using to derive their scientific theories? What technology were they using to generate that data?
You can't hope to explain the universe without observing it first, and humans are quite bad at observation without the aide of technology.
A good chunk of valuable information disappears all the time from Internet. Many thoughts expressed in personal blogs usually go away within a few years. See, for example, demise of Geocities and Yahoo Groups. While only a small part of this disappeared information is valuable, some of it incredibly useful and important.
That argument fails on the above point - you picture generations as discontinuous (or nearly so), whereas in the normal, non-technical sense - as here - they are simply a useful picture of an aggregation over a continuum of ages in the population as a whole.
Working and academic environments - beyond a certain level of competence - are populated by individuals of varying ages and experience which are more likely to be demarked by managerial levels and career choices than individual knowledge and aptitude.
Because new humans have to learn what the prior generation learned from scratch, it gives them a fresh canvas to eliminate flaws and purify knowledge from the prior generation.
It's like taking a wrong turn on a roadtrip. You've driven so far and convinced yourself that you're on the right path. But in reality you need to step back and check all the assumptions and choices you've made to get on this path.
People coming in and out of existence facilitates sanity checks on current acquired knowledge.
k[i] = (1 - c1) * k[i - 1] + c2
where i is the generation number, k is the amount of knowledge we have, c1 is the loss factor (amount of knowledge lost from one generation to another, 0 ≤ c1 ≤ 1), and c2 is the (constant) amount of new knowledge created by generation i.
In this model, it's easy to show that after long periods of time the amount of knowledge will plateau. In fact, the plateau is
k[∞] = c2 / c1
The basic point of this is to highlight that both knowledge creation and loss are factors, and the loss means that knowledge may not keep increasing indefinitely. Of course, any number of the approximations and assumptions involved in this derivation may not be valid, but I think the possibility that knowledge loss can cause problems is worth considering.
There were certainly cavemen born with Einstein-level intelligence from time to time, but without a foundation to build on, peers to collaborate with, or written language to preserve their knowledge, they would both create and pass on significantly less knowledge than someone in modern times. One generation might lose a large portion of all the knowledge built up for millenia prior during a civilization's collapse; while another generation may stumble upon a discovery which ushers in a short but extremely productive era of knowledge production. If nothing else, if you have 4 billion people in one generation and 8 billion in another then all else being equal the latter generation has twice as many brains with which to store and create knowledge.
As you've indicated, heterogeneity in various parts of the problem make this sort of modeling questionable. It's a crude model not meant to make precise predictions, just show that knowledge loss can be a major factor at long times.
Human ability to close this “linked chain” of generations will always have a “missing link”?
An asteroid or... great filter due to environmental collapse!
To me it always felt intuitively like being able to have perfect knowledge of all wave function collapses, all the states of every particle ever scale of a problem.
There’s entropy too; no more information to pull from the universe sounds a lot like heat death to me.
Are we chasing a biochemical feedback loop? There’s a lot of “unproven” math, to be casual Sunday night from a legal weed state about it ;)
How much potential is there all of this boils down to our ability to so thoroughly convince ourselves of something’s correctness and it turns out there’s no Gods on top of that mountain?
The overlap is perfect and zero at the same time as "generations" are a descriptive simplification rather than a reflection of reality. Every year people are born whose overlap with the people the year before is off by just one year (more or less). A new PhD student learns from his peers a year further along as well as from the post-doc 5 years ahead and the professor 10 years ahead.
Talking about "generations" is a bit like talking about signs of Zodiac. Are you a millennial? Or are you Capricorn?
Edit in response to downvote: This is an effort to model the whole universe using graph theory. I found it amazing not because how possible it might be the true answer, but because it provides an insight that clicks: a computational world, where any limited space can store only a limited amount of information. At least it is a beautiful mental model.
"Do we need a ToE" is indeed an important question. But if some theory has been proposed and it "looks like" a good candidate of Theory of Everything, then many of us can just skip such questions.