A quote from the Quanta article:
It's important to know that topologists regard a circle as a one dimensional sphere and the usual sphere as a two dimensional sphere.
A three dimensional sphere is a two dimensional sphere, but one dimension up!
Note that geometers regard a circle as a two dimensional sphere and the usual sphere as a three dimensional sphere so be careful when consulting different sources on the internet. I've fallen foul of this distinction in past topological posts.
Regardless of the choice of convention the term "sphere" refers to the surface only. https://mathworld.wolfram.com/Hypersphere.html
Sorry for living ....I have a particular dislike of folks posting time-consuming links without saying why we should be interested. Sorry. Maybe just me, but it right gives me the weed! (Which is to say a state of excited and uncontrolled rage, which is unlike my usual state of serene and copacetic calmness...)
The issue of 8.2 eV laser excitation (Ultraviolet photons I would think) of Thorium 229 should first be considered by its position in the Periodic Table of Chemistry:
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Aha! We are looking at Thorium 90, an Actinide, along with all its disreputable fellow fissile elements, including U235 and Pt239. Thorium is 4 times more common than Uranium, which makes it of interest in things Nuclear.
https://en.wikipedia.org/wiki/Isotopes_of_thorium
Th232 is considered a precursor for weapons and reactors, having a conveniently small fissile mass of about 5kg (with suitable neutron reflectors) when converted to U233 by neutron capture and subsequent beta decay.
https://en.wikipedia.org/wiki/Uranium-233
These foolish Americans thought they were watching some sort of firework show, codenamed "Operation Teapot":
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Just wait for the shock wave to hit, along with a particularly nasty grade of sunburn! Sort of thing that gets atomic physics a bad name.
Personally, I suggest you do not try this at home. Accidents involving such materials can harm your health, as with the famous "Demon Core" of Pt239 with Tungsten Carbide reflectors:
https://en.wikipedia.org/wiki/Demon_core
This Thorium229 experiment has many of the elements of the famous and precise Mossbauer effect, which I have performed in the physics lab. Including using a large crystal to reduce momentum recoil effects.
Here at more respectable system7 labs, we are fixing a GIANT bicycle to save the planet:
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I have ordered new 3x7 Shimano gearshifters, along with frame-mounted reflectors, which are as rare as hens' teeth but an essential safety feature along with lights.
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Because I defy you to fix old rusty ones. These things are the work of the Devil, IMO.
Also further investigating my new Nikon D60 DSLR camera settings. Apparently saving images in RAW format is another GOOD THING for astronomy. Avoids compression an' all that.
It is important to read the manual, IMO.
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Yes, Patrick Moore's old Observer's book of Astronomy is still useful for Nova hunters.
Best, Steve.
Maybe you're actually quite reactive & temperamental ???
I can't agree on this. If all theoretical thinking points to a certain working but at the same time it is realised that it will never be possible to prove - will we then reject it? Can't be.
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Whilst Mathematicians can imagine any possible Universe whatsoever, Physicists are constrained by experiment to the World or Universe we actually live in.
This is why String Theory is bunk. A child of ten can see that our Universe has 4 dimensions of Spacetime, not ten! And a happy place it is for it.
Apropros my investigations into Novae and Supernovae, I find them extremely interesting. They provide the standard candles that confirm our increasingly expanding Universe in the last 5.5 Bn years:
https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe
I prefer such serious investigations to any of Lex Fridman's mind-numbing musings about Artificial Intelligence, whether we live in a Simulation, or the existence of Aliens.
The only takeaway from String Theory is the CFT/aDS correspondence, which essentially relates the properties of the volume of a hypershere to its lower dimensional surface.
I was out in the field last night, and found no sign of T Corona Borealis Nova blazing yet:
I therefore considered where Arcturus was in the sky when the greatest Mathematician of antiquity, Archimedes of Syracuse was pondering things:
https://en.wikipedia.org/wiki/Archimedes#
It has moved three full moon's width in that time elapsed!
He was a great one for summing Infinite Series, as am I:
My own favourite series is the Euler Zeta(2) function:
It's uncanny relationship to the Prime Numbers has led to the great unsolved problem in Mathematics, the more general Riemann Zeta Function.
I am always looking for a Physics interpretation of this, and have spent a lot of time on it.
So far, putting on my Physics hat, I interpret it as the sum of the electric or gravitational force near a row of spheres, considering a charge constrained by two flat and earthed flat conducting plates, by the method of images.
This may convey my notion if you think of the black spheres obeying inverse square:
Cue the fascinating Orrery at Ryde, a painting rather than a mirror ball, which makes a statement about Conformal Field Theory (CFT) which preserves right angles:
More Conformal field stuff, which is close to the method of images:
A long post, but interesting, one hopes.
This is why String Theory is bunk. A child of ten can see that our Universe has 4 dimensions of Spacetime, not ten! And a happy place it is for it.
Apropros my investigations into Novae and Supernovae, I find them extremely interesting. They provide the standard candles that confirm our increasingly expanding Universe in the last 5.5 Bn years:
https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe
I prefer such serious investigations to any of Lex Fridman's mind-numbing musings about Artificial Intelligence, whether we live in a Simulation, or the existence of Aliens.
The only takeaway from String Theory is the CFT/aDS correspondence, which essentially relates the properties of the volume of a hypershere to its lower dimensional surface.
I was out in the field last night, and found no sign of T Corona Borealis Nova blazing yet:
I therefore considered where Arcturus was in the sky when the greatest Mathematician of antiquity, Archimedes of Syracuse was pondering things:
https://en.wikipedia.org/wiki/Archimedes#
It has moved three full moon's width in that time elapsed!
He was a great one for summing Infinite Series, as am I:
My own favourite series is the Euler Zeta(2) function:
It's uncanny relationship to the Prime Numbers has led to the great unsolved problem in Mathematics, the more general Riemann Zeta Function.
I am always looking for a Physics interpretation of this, and have spent a lot of time on it.
So far, putting on my Physics hat, I interpret it as the sum of the electric or gravitational force near a row of spheres, considering a charge constrained by two flat and earthed flat conducting plates, by the method of images.
This may convey my notion if you think of the black spheres obeying inverse square:
Cue the fascinating Orrery at Ryde, a painting rather than a mirror ball, which makes a statement about Conformal Field Theory (CFT) which preserves right angles:
More Conformal field stuff, which is close to the method of images:
A long post, but interesting, one hopes.
We have discussed the opinion that a good theory should furnish predictions that are testable. Pass the relevant tests and we have an accepted theory.
The speculative nature of string theory makes it less testable than other theories. However, that is not to say that its adherents don't continually come up with areas in which they think it is testable.
We see claims like: "String theory is testable, even supertestable", "Physicists finally find a way to test superstring theory", "South pole neutrino detector could yield evidence for string theory", "A cosmic scale test for string theory", "Scientists devise test for string theory" etc. etc.
So note that, although it may never be possible to prove string theory, the theoretical thinking has not yet been rejected.
I read that AdS/CFT correspondence may lead to a string theory dual to QCD (quantum chromodynamics).
The idea is highly testable in the sense of an equivalence between the two theories, not an experimental test.
Apparently, AdS/CFT may be used to make qualitative predictions about phenomena in heavy-ion collisions, where accurate QCD predictions are not available.
More here: https://en.wikipedia.org/wiki/AdS/Q...,field theory is not a conformal field theory.
I suppose if a theory has been tested successfully it turns into knowledge/facts and its not a theory anymore ;-)
I think we should also accept a situation that we could have bunch of testable theories that didn't pan out and one that is very plausible but not testable.... forever... this might be the situation we could end up in. And if so, we cant take promote one of the testable just because of that.
Basic is that a theory has a defined a test. Then to see if the test is possible to conduct.
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I feel string theory and the multiverse and vacuum energy all a bit distracting when we can’t explain dark energy, dark matter or precisely how EM propagates through a vacuum. Or what gravity is (without going off in the deep end), or the arrow of time etc. To me, these are the problems that have to be solved first. YMMV.
F
Fair enough. But, after 40 yrs ST has not been able to produce anything of substance, other than some fantastic math that may be applicable to other areas of science. Even Ed Witten in the video I posted earlier has admitted as much. If I look at Einstein, he started off with some things that were not fully explainable, and out of that came special relativity. That then provided a springboard to GR which answered another whole bunch of questions that up until 1915 had been unexplained. With ST, strings at Planck scales appear to be quite a random construct upon which to build a theory. You aren’t starting from something you can observe and then explaining what the underlying cause is or what your observations might lead to, but are constructing something upon something that is and will remain unobservable afaik for ever. Now, maybe you can argue Einstein could not observe a gravity field, or a light quanta so he in some sense also took a leap into the dark, but his theories provide stunning conformance with reality. Unfortunately, the same cannot be said for ST, ‘ephemeral fermions’ or vacuum energy.
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Knot theory is quite fascinating!
I've learned that the fascination with knot theory started when Scottish physicist Lord Kelvin hypothesised that each element is just a distinct knot in the fabric of the ether. When the true model of the atom was discovered interest from physicists died off, but mathematicians continued their investigations just for the sake of discovery.
For those interested in why mathematicians study knots: https://www.quantamagazine.org/why-mathematicians-study-knots-20221031/
Wikipedia has a good explanation of the difference between a theory and a fact, in science. There is no progression from one to the other.
"A scientific theory is an explanation of an aspect of the natural world and universe that can be (or a fortiori, that has been) repeatedly tested and corroborated in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation of results.
Where possible, some theories are tested under controlled conditions in an experiment.[1][2] In circumstances not amenable to experimental testing, theories are evaluated through principles of abductive reasoning. Established scientific theories have withstood rigorous scrutiny and embody scientific knowledge.
A scientific theory differs from a scientific fact or scientific law in that a theory explains "why" or "how": a fact is a simple, basic observation, whereas a law is a statement (often a mathematical equation) about a relationship between facts and/or other laws."
Not so sure I liked it actually A theory could be anything stupid really?
When/will GR be upgraded to a fact or law? Maybe it i but still called a theory... quite confusing :-/
Again, I have no problems with all this really - just struck me that the words used and semantics where a bit "odd"...
Theory: "why" or "how" (vague!)
Fact: simple, basic observation.
The wiki text is as I see it a bit of a logical mess.
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A theory could be anything stupid really?When/will GR be upgraded to a fact or law? Maybe it i but still called a theory... quite confusing :-/
Again, I have no problems with all this really - just struck me that the words used and semantics where a bit "odd"...
Theory: "why" or "how" (vague!)
Fact: simple, basic observation.
The wiki text is as I see it a bit of a logical mess.
//
I like this simple explanation:
"In the scientific process, theories are developed to explain facts, and new facts can lead to the refinement or reassessment of existing theories."
To illustrate: In the photoelectric effect, the observed fact was that low frequency light could not eject electrons from a negatively charged zinc plate no matter how intense, while high frequency light of low intensity could.
The explanatory theory was that light consists of discreet bundles, each carrying energy proportional to the frequency of the light. A single bundle of low frequency light does not carry sufficient energy to eject a single electron, whereas a single bundle of high frequency light does.
"In the scientific process, theories are developed to explain facts, and new facts can lead to the refinement or reassessment of existing theories."
To illustrate: In the photoelectric effect, the observed fact was that low frequency light could not eject electrons from a negatively charged zinc plate no matter how intense, while high frequency light of low intensity could.
The explanatory theory was that light consists of discreet bundles, each carrying energy proportional to the frequency of the light. A single bundle of low frequency light does not carry sufficient energy to eject a single electron, whereas a single bundle of high frequency light does.
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