Rumour has it that Albert Einstein spent his last few hours on Earth scribbling something on a piece of paper in a last attempt to formulate a theory of everything. Some 60 years later, another legendary figure in theoretical physics, Stephen Hawking, may have passed away with similar thoughts. We know Hawking thought something called "M-theory" is our best bet for a complete theory of the universe. But what is it?
Since the formulation of Einstein's theory of general relativity in 1915, every theoretical physicist has been dreaming of reconciling our understanding of the infinitely small world of atoms and particles with that of the infinitely large scale of the cosmos. While the latter is effectively described by Einstein's equations, the former is predicted with extraordinary accuracy by the so-called Standard Model of fundamental interactions.
Our current understanding is that the interaction between physical objects is described by four fundamental forces. Two of them – gravity and electromagnetism – are relevant for us on a macroscopic level, we deal with them in our everyday life. The other two, dubbed strong and weak interactions, act on a very small scale and become relevant only when dealing with subatomic processes.
The standard model of fundamental interactions provides a unified framework for three of these forces, but gravity cannot be consistently included in this picture. Despite its accurate description of large scale phenomena such as a planet's orbit or galaxy dynamics, general relativity breaks down at very short distances. According to the standard model, all forces are mediated by specific particles. For gravity, a particle called the graviton does the job. But when trying to calculate how these gravitons interact, nonsensical infinities appear.
A consistent theory of gravity should be valid at any scale and should take into account the quantum nature of fundamental particles. This would accommodate gravity in a unified framework with the other three fundamental interactions, thus providing the celebrated theory of everything. Of course, since Einstein's death in 1955, a lot of progress has been made and nowadays our best candidate goes under the name of M-theory.
String revolution
To understand the basic idea of M-theory, one has to go back to the 1970s when scientists realised that, rather than describing the universe based on point like particles, you could describe it in terms of tiny oscillating strings (tubes of energy). This new way of thinking about the fundamental constituents of nature turned out to solve many theoretical problems. Above all, a particular oscillation of the string could be interpreted as a graviton. And unlike the standard theory of gravity, string theory can describe its interactions mathematically without getting strange infinities. Thus, gravity was finally included in a unified framework.
After this exciting discovery, theoretical physicists devoted a lot of effort to understanding the consequences of this seminal idea. However, as often happens with scientific research, the history of string theory is characterised by ups and downs. At first, people were puzzled because it predicted the existence of a particle which travels faster than the speed of light, dubbed a "tachyon". This prediction was in contrast with all the experimental observations and cast serious doubt on string theory.
Nevertheless, this issue was solved in the early 1980s by the introduction of something called "supersymmetry" in string theory. This predicts that every particle has a superpartner and, by an extraordinary coincidence, the same condition actually eliminates the tachyon. This first success is commonly known as "the first string revolution".
Another striking feature is that string theory requires the existence of ten spacetime dimensions. Currently, we only know of four: depth, height, width and time. Although this might seem a major obstacle, several solutions have been proposed and nowadays it is considered as a notable feature, rather than a problem.
For example, we could somehow be forced to live in a four dimensional world without any access to the extra dimensions. Or the extra dimensions could be "compactified" on such a small scale we wouldn't notice them. However, different compactifications would lead to different values of the physical constants and, therefore, different physics laws. A possible solution is that our universe is just one of many in an infinite "multiverse", governed by different physics laws.
This may seem odd, but a lot of theoretical physicists are coming around to this idea. If you are not convinced you may try to read the novel Flatland: a romance of many dimensions by Edwin Abbott, in which the characters are forced to live in two space dimensions and are unable to realise there is a third one.
M-theory
But there was one remaining pressing issue that was bothering string theorists at the time. A thorough classification showed the existence of five different consistent string theories, and it was unclear why nature would pick one out of five.
This is when M-theory entered the game. During the second string revolution, in 1995, physicists proposed that the five consistent string theories are actually only different faces of a unique theory which lives in eleven spacetime dimensions and is known as M-theory. It includes each of the string theories in different physical contexts, but is still valid for all of them. This extremely fascinating picture has led most theoretical physicists to believe in M-theory as the theory of everything – it is also more mathematically consistent than other candidate theories.
Nevertheless, so far M-theory has struggled in producing predictions that can be tested by experiments. Supersymmetry is currently being tested at the Large Hadron Collider. If scientists do find evidence of superpartners, that would ultimately strengthen M-theory. But it still remains a challenge for current theoretical physicists to produce testable predictions and for experimental physicists to set up experiments to test them.
Most great physicists and cosmologists are driven by a passion to find that beautiful, simple description of the world that can explain everything. And although we are not quite there yet, we wouldn't have a chance without the sharp, creative minds of people like Hawking.
Explore further:
Black holes dissolving like aspirin: How Hawking changed physics
novasp9
Einstein always insisted on theories that make predictions and allow the theories to be rigorously tested. He would have been deeply troubled by some of the pseudoscience that has passed for science over the last 40 years. The latest suggestions that we may need to forego empirical
testing in favor of subjective metaphysics would be totally anathema to Einstein.
vlaaing peerd
actually just one physicist, Edward Witten.
grandpa
vlaaing peerd
Current day theoretical physics is at the point that they are trying to unify laws describing black holes, big bangs with laws that describe particles smaller than an atom. There's not much testing and verifiying we can do on those levels.
Einstein's gravity is even more accurate on a larger scale and also there it took some time before his theory could be tested by observation, it was only last year we discovered gravity waves, some 100 years after his discovery.
String theory describes events smaller than QM and bigger than the universe (if any), don't you think it needs time before we find ways of testing it?
Newton made theories based on observations, but Einstein was already theorising ahead of observations. So why not give strings a chance? It does address the gap we have between QM and gravity, that makes it worth checking out.
novasp9
String theory has had over 4 decades to come up with well-defined and rigorous predictions. It has totally failed to do so. All we have so far is hype.
True, it is interesting and useful in the pure math dept., but as physics it remains in the pseudoscience category.
antialias_physorg
I think you misunderstand String Theory. There isn't one 'string theory' but an entire family of theories depending on the parameters you choose. The current state is that these parameters are being constrained (i.e. the family is being narrowed down to few members..mostly within M-theory), but the number of open parameters is still large. Particularly since it's an 11-dimensional theory makes it kinda hard to test (as of yet) in our 4 dimensional spacetime.
Only when the constraint hits the point where it's very narrow will String Theory or M-theory be able to make the kinds of predictions that will lead to tests which could falsify it (in its entirety). Currently it seems the most promsing avenue for unification of gravity and quantum mechanics.
tblakely1357
Hyperfuzzy
luke_w_bradley
There should be infinite things to discover just in basic, classic physics (e.g. complex structures you could build with surprising properties nonetheless consistent w classic physics.) But everyone is clustering into this brutally competitive sector with very low payouts.
Da Schneib
As far as continuing research in M-theory, it's necessary since there is math in it we do not yet understand. Like its progenitor, General Relativity Theory, M-theory is enormously mathematically complex and requires a great deal of research that won't yield much until someone who has the math comes along and figures it out. We're still waiting for that person.
tblakely1357
Remember, we aren't not talking about a few people working on a theory for a few years, we're talking about hundreds of bright people working on string theory for over 30 years and coming up with zip, nada.
Da Schneib
During the 20th century, when physics was absorbing the enormous changes wrought by GRT and quantum theory, many fruitful avenues of research opened up and were easily followed up to amazing technical results. Now, in the 21st century, we are finding that much of this material has been absorbed, and there don't appear to be so many new avenues of research. It may be decades or even centuries before we see any time like the early 20th century again.
eric96
luke_w_bradley
A computer is an engineered object, yet there is a field of study called computer science to discern yet unknown properties about what it does. Many engineered objects have unexpected emergent properties.
Of course, claims about systems at this scale are actually testable and have consequences, not a good place to hide incompetence.
Da Schneib
Computer science is about discovering facts and making theories of computer programming. Most real computer scientists work at universities, not corporations. Programmers work at corporations, though a few computer scientists are generally kept on staff. The corporate environment is not conducive to pure science.
luke_w_bradley
Science is something we do, not something we are. Tenure and peer review don't validate theories, results do. If the wheels aren't hitting the road with a theory while the world has all these other existential threats, maybe it's time to reevaluate the focus.
RobertKarlStonjek
Thus science always built on other science. Scientists occasionally took leaps into new physics during the quantum revolution but the bridge back to established physics quickly followed.
This is not the case for string theory which requires a huge leap of faith to the string, which is not an extension of established physics, has never been observed, never involved in successful experiment or prediction, and for which no explanation of the constituents has even been suggested.
Small leaps are like probes into the unknown but string theory has been a leap of faith on the same scale as God belief which also promised to explain everything yet ultimately explained nothing.
Da Schneib
I don't think you know very much about computers and programming and see little point in continuing this conversation. It's very much like arguing with someone who doesn't know anything about internal combustion engines about diesel locomotive design.
Da Schneib
ellbeeyoo
ellbeeyoo
Eikka
You're pulling a red herring by asking trivial questions. Whether a person knows how bubble sort works is irrelevant to the question of the difference between engineering and science.
Science is a philosophy, science also literally means knowledge. A bridge engineer is doing science every time they build a bridge, as they are discovering new things about bridges and getting systematically better at it. Making an artifact is always an act of discovery about reality, while "pure" science is an armchair philosophy - an exercise in abstract thinking which in itself does not result in new knowledge. Likewise, a "mere programmer" in a company is necessarily accumulating knowledge - science - of the thing they're working on. They're rarely just "software engineers".
And I've implemented both sort algorithms when I was a kid, but hell if I remember which one did what
Eikka
Quicksort had something to do with splitting the array in half and half again.
Now, googling:
https://en.wikipe...ble_sort
https://en.wikipe...uicksort
Now, the question is, knowing these, what have we proven, DaSchneib?
Absolutely nothing. It was just your chance to flaunt trivial expertise.
Eikka
The main criticism is that String Theory has so many moving parameters that it can be tweaked to produce just about any description of reality. You tweak it a little and out pops new equations that describe a different reality.
So it lacks any predictive power, i.e. it's not science, because it predicts everything. Whatever happens in reality, you can tweak string theory to agree, but to do it the other way around is impossible because string theory doesn't suggest what the parameters should be. It just gives you something like 10 to the power of 500 different realities that might exist and says "yours is one of these. Take a pick. Good luck."
ShotmanMaslo
Wrong, your article is about lack of detected micro black holes but vast majority of string theories do not predict any micro black holes at LHC energies. Even your popsci article explains that it does not rule out ST, cant you read?
guptm
PowerMax
yoatmon
greenonions1
TheGhostofOtto1923
But if you like lots of words, best to use official ones
"Applied science is a discipline of science that applies existing scientific knowledge to develop more practical applications, like technology or inventions. ... This includes a broad range of applied science related fields from engineering, business, medicine to early childhood education."
-rather than trying to make them up yourself. As if you actually know what you're talking about.
Da Schneib
When you do science you don't know what result you're going to get. That's why you're doing science. I don't really want anyone doing science on bridges. Let's stick to engineering for bridges, shall we?
That doesn't mean we always know what's going to happen; it just means we have a pretty good idea it's not going to just fall down. We're not always going to be right but we have a better chance than if we just wing it.
Da Schneib
Maybe you should learn some about string physics if you're going to blather about it, lest you look like another idiot who is bloviating about something they know nothing about.
Mark Thomas
https://en.m.wiki...M-theory
Under M-theory you might infer our universe is a 5 dimensional memBrane on an 11 dimensional bulk. We have 3 dimensions of space plus 1 dimension of time plus 1 other dimension. Being a Star Trek fan I will call the other dimension "subspace." :-)
Da Schneib
Da Schneib
Da Schneib
Hyperfuzzy
greenonions1
Hyperfuzzy
Really, most had elementary mechanics for a BS! Stupid construction!
Hyperfuzzy
Why doesn't anyone state a proper Theory with Axioms and Logic that cannot be challenged. I do. Comments?
Hyperfuzzy
Hyperfuzzy
Huh? Explain, Logically? Did you mean falsify with or without acceptable logic, i.e. proof! So now we're questioning Proof as "must be" falsifiable which is defined by an acceptable truth, Axiomatic Structure? Sounds like a denial of any Modus Ponems? Then we have nothing but conversational logic, even if undeniable! Maybe this is why so many consider Einstein a Genius. Logic without a provable axiom, only accepted without logic. Or named objects without realize-ability. Anyway, we must avoid nonsense when applying the obvious!
Hyperfuzzy
TheGhostofOtto1923
That bridge span was obviously designed to support itself while the rest of the structure was erected, or else they wouldn't have been allowed to install it that way.
It sounds like either the post tension cables were not properly anchored, someone forgot to anchor them, the concretre mix was off (hence the cracks) or similar.
Bad design and/or construction aside, the engr who left the voicemail about the cracks and failed to scream and wail until it was resolved, should be dismembered.
Hyperfuzzy
So a mistake was made, evidence: Not to plan! Here let's stick with what can be learned in the class room and ignore the day dreamer as c is Lambda Nu a constant, everywhere, not speed! speed emitted wavelength divided by measured period, high school algebra! Forget the obvious failure, not a matter of debate. Method?
eric96
Reg Mundy
Regrettably, like most of his contemporaries, SH failed to grasp the intrinsic nature of the Universe.
EVERYTHING in the universe is expanding, and that expansion gives us what we experience as TIME. The phenomenon we call gravity is a consequence of this expansion, and gravity DOES NOT EXIST as a force.
As TIME is an effect of the state of all matter in the universe, a collision of black holes converting matter to radiation causes a disturbance in our experience of TIME which we perceive as a wave and mis-call it a gravity wave, when actually it should be called a TIME-QUAKE or something similar.
No amount of effort put into M-Theory or similar will ever account for a force called gravity, as it doesn't exist, and the graviton will never be found.
betterexists
Here is the Link: https://www.youtu..._ng8X_6w
I tried hard to find an old one: http://serveveda.org/?p=650
I haven't read it, because I am NOT interested.
betterexists
betterexists
humy
As so often is the case, in this case, the scientific theory comes first before a practical way to test it is worked out.
Just because we don't yet have a way to test a theory, doesn't necessarily mean we never would thus you shouldn't dismiss (like you did) a theory as being "pseudoscience" just merely because we CURRENTLY haven't worked out a practical way to test it; What if we then later find a way to test it?
"pseudoscience" is what was never scientific in the first place, not necessarily what we cannot YET test.
You speak of Einstein but are you aware that even his theory wasn't immediately testable because when he initially formulated it, no one had worked out a practical way of testing it? -that came later.
So would you have at that time dismissed his theory (relativity) as "pseudoscience" before someone had a chance to work out a way to test it?
betterexists
humy
That is just because it is harder to find a practical way to test the theory (by deducing a testable prediction), not that a practical way to test the theory will never be found.
It is creditable that someone working with string theory (or some variant of it) could come up with a practical way to test the theory in the next few decades.
Why is the "over 4 decades" figure relevant? Is there an official time limit to this? What if it takes a whole century before someone comes up with a practical way to test the theory and then it is tested and proven correct; would you still dismiss it as "pseudoscience" because nobody worked out a practical way to test it in a totally arbitrary and illogical time limit of, say, "4 decades", chosen by you? There is no definable time limit to this.
Some proven scientific theories did take over "4 decades" to test.
betterexists
I did Google search using key words, Dr. Sivaram Babu hawking (Then, I followed up with Custom Range of 2009-2011)
https://www.googl...amp;tbm=
humy
I am afraid you are exposing your ignorance yet again. This problem was solved long ago so you are out-of-date. Nobody "ignored" it and, in fact, M-theory was at least in part formulated as a solution to it.
As this article says;
"...physicists proposed that the five consistent string theories are actually only different faces of a unique theory which lives in eleven spacetime dimensions and is known as M-theory. It includes each of the string theories in different physical contexts, but is still valid for all of them. This ... has led most theoretical physicists to believe in M-theory as the theory of everything – it is also more mathematically consistent than other candidate theories...."
You really should study the science before rubbishing it.
And the people that came up with is are NOT "crackpots"
.
humy
Misspelling. And that should have been;
"And the people that came up with it are NOT, as you claim, "crackpots", but rather smarter than you and I.
If you still persist in calling them "crackpots", why don't you can come up with a better theory of everything and collect you Nobel prize? -answer, because you are less smart than them.
betterexists
Hyperfuzzy
Hyperfuzzy
https://en.wikipe.../Hypatia
ShotmanMaslo
Not true at all.
String theory cannot predict them yet. However, it may also turn out that they largely cannot be predicted. Does a theory of gravity predict exactly what planets orbit in our system? No, as planet creation process is mostly random. It can only predict their motion after their masses and positions are postulated. Same could very well be true for many physical constants, if we live in a multiverse. Maybe many different string vacua are real and we merely live in one of them. Certainly string theory landscape and eternal inflation point towards this direction.
Da Schneib
It's either through a misunderstanding of how hadron masses are predicted, or a misunderstanding of the meaning of "elementary particle" to include hadrons.
Hadrons are composed of quarks and gluons, and quantum chromodynamics (QCD) allows us to predict the masses of expected combinations of quarks and gluons. But the masses of the fundamental particles, like quarks and gluons, and leptons (neutrinos and electrons and muons and tauons) are free parameters in the Standard Model of particle physics. If string physics turns out to be correct, it should allow us to make postdictions of these masses based on the resonance modes of the strings on the Calabi-Yau space that comprises the geometry of our universe.
[contd]
Da Schneib
In fact, this is another attraction of string physics; if we can identify the correct Calabi-Yau geometry for our universe, we will be able to cut the number of free parameters from 26 to about 13. In addition to that, it will also explain the strengths of the four forces, which reduces the free parameters to nine. The CKM and PMNS matrix mixing angles may also turn out to be determined by this, reducing the free parameters to three, and I haven't thought about it enough to see if the others might yield as well. This would be an enormous simplification of particle physics, and comes along with a quantum gravity theory for free. You can see why physicists and mathematicians are so interested in string physics from this.
A propos of this, does anyone know if loop quantum gravity (LQG) offers these simplifications?
sirdumpalot
An accurate idea arises in relation to experiment and observation. The further the distance between observation and idea, the more ideological it is. String theory has no experiment, no observation.
"Quantum mechanics is a theory about the physical description of physical systems relative to other systems, and this is a complete description of the world." Rovelli
No need for preserving even an ounce of the metaphysics of realism in a scientific theory. The scientific method establishes truth - say 5 sigma or something - through hypothesis and observer verification. Only inference is not enough.
Da Schneib
Da Schneib
Experiment at the LHC is ongoing. Do pay attention.
Meanwhile it's been pointed out that it's worthless to pretend ongoing fruitful research is not useful because it violates your assumptions. Predictions of GRT made nearly 100 years ago have first been confirmed within the last couple of years. Hate to tell you but sometimes it takes a long time. First thing you learn is, you always gotta wait.
Hyperfuzzy
Da Schneib
Your first reference only shows that, quote, end quote, is even affected by the lack of micro black holes at the LHC, and I'm not even sure I believe that much.
Stop lying, @macurinetherapy.
tblakely1357
Reg Mundy
Interesting to see someone remembers Ockham's Razor after all. Why does M-Theory with its multiple assumptions and vague validity attract so many adherents, while Expansion Theory, which is straightforward and logical (and explains all phenomena such as gravity, rotation pattern of galaxies, etc.), attracts only opprobium? Does no-one bother THINKING anymore?
eric96
Hyperfuzzy
MRBlizzard
ShotmanMaslo
Only extra dimensions of certain relatively large length lead to production of black holes in LHC. Most string theories use far smaller dimensions and do not predict such black holes.
someone11235813
Hyperfuzzy
The universe is not expanding, we are within an accelerating Galaxy stream, Red Shift. Light speed is from 0 to infinity, i.e. original_wavelength/measured_period, i.e. Einstein false,. The center of the charge's field is charge not a particle, a point, i.e standard model as nonsense, The field is everywhere therefor do the summation it equals Gravity. Light is caused by repetitive motion of the center. Charge always comply s, there is nothing else, Modern Physics is a delusion!
andyf
Yup! We're waiting for the man...
SillyOldGit
You are not the man.
andyf
Here he comes, he's all dressed in black
Beat up shoes and a big straw hat
He's never early, he's always late
First thing you learn is that you always gotta wait
I'm waiting for my man, ah work it now
The Velvet Underground & Nico 1967
milnik
milnik
Discard all of what I will state and then you will be much closer to finding out the true causes of the phenomenon in the universe, such as:
milnik
milnik
You are discussing and inventing various theories and now it is on the order of M-theory, and where you have buried all the previous theories. It seems that you own a black hole in which all the scientific disagreements end up in that hole.
Da Schneib
milnik
Hyperfuzzy
as the Nonsense continues unabated
milnik
Hyperfuzzy
Bull! Actually; as a 2 dimensional being; how do I adjust my camera? Well, I guess you could be a leaf in the wind; or, really paying attention in class. Why to a class you do not conceive conceptually, why go?
From where I sit it all come's down to the centers of these diametrical spherical fields. it's entire presence at any point in time, and nothing but its field at every point in space at that point in time; I can still see the Velocity Vector!
Hyperfuzzy
Hyperfuzzy
We would be able to see in all directions; well you could polarize the points on the line, a plane.. Ohh I get it, we've been looking at it the whole time; got centers moving about, well maybe; however, I suspect potential!.
RealityCheck
Consider some of that garbage:
1) the 'strings' are "tubes of energy", but what that energy ACTUALLY IS is still NOT explained!
2) the hypothesized Supersymmetric entities that supposedly 'saved' M-theory is NOW ITSELF being proven via LHC experiments/observations NOT to exist!
3) a 'particular vibration' of such string(s) supposedly "providing the graviton" (so as to 'include Gravity' in M-theory) is UN-physical BUNKUM.
4) at NO STAGE does M-theory (and associated hypotheses) provide an actual PHYSICALLY REAL EFFECTIVE MECHANISM to 'manifest' OR 'explain' all these claimed wondrous properties for M-theory 'entities and interactions' in observed phenmena from infinitesimal to infinite.
*sigh*
Reg Mundy
Despite our past exchanges, I am sorry to say that I agree with you.
rrrander