Physics General Subjects Thread

https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106

Riddle solved: Why was Roman concrete so durable?

The ancient Romans were masters of engineering, constructing vast networks of roads, aqueducts, ports, and massive buildings, whose remains have survived for two millennia. Many of these structures were built with concrete: Rome’s famed Pantheon, which has the world’s largest unreinforced concrete dome and was dedicated in A.D. 128, is still intact, and some ancient Roman aqueducts still deliver water to Rome today. Meanwhile, many modern concrete structures have crumbled after a few decades.

Researchers have spent decades trying to figure out the secret of this ultradurable ancient construction material, particularly in structures that endured especially harsh conditions, such as docks, sewers, and seawalls, or those constructed in seismically active locations.

Now, a team of investigators from MIT, Harvard University, and laboratories in Italy and Switzerland, has made progress in this field, discovering ancient concrete-manufacturing strategies that incorporated several key self-healing functionalities. The findings are published today in the journal Science Advances, in a paper by MIT professor of civil and environmental engineering Admir Masic, former doctoral student Linda Seymour ’14, PhD ’21, and four others.

For many years, researchers have assumed that the key to the ancient concrete’s durability was based on one ingredient: pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples. This specific kind of ash was even shipped all across the vast Roman empire to be used in construction, and was described as a key ingredient for concrete in accounts by architects and historians at the time.

Under closer examination, these ancient samples also contain small, distinctive, millimeter-scale bright white mineral features, which have been long recognized as a ubiquitous component of Roman concretes. These white chunks, often referred to as “lime clasts,” originate from lime, another key component of the ancient concrete mix. “Ever since I first began working with ancient Roman concrete, I’ve always been fascinated by these features,” says Masic. “These are not found in modern concrete formulations, so why are they present in these ancient materials?”

Previously disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials, the new study suggests that these tiny lime clasts gave the concrete a previously unrecognized self-healing capability. “The idea that the presence of these lime clasts was simply attributed to low quality control always bothered me,” says Masic. “If the Romans put so much effort into making an outstanding construction material, following all of the detailed recipes that had been optimized over the course of many centuries, why would they put so little effort into ensuring the production of a well-mixed final product? There has to be more to this story.”

Upon further characterization of these lime clasts, using high-resolution multiscale imaging and chemical mapping techniques pioneered in Masic’s research lab, the researchers gained new insights into the potential functionality of these lime clasts.

Historically, it had been assumed that when lime was incorporated into Roman concrete, it was first combined with water to form a highly reactive paste-like material, in a process known as slaking. But this process alone could not account for the presence of the lime clasts. Masic wondered: “Was it possible that the Romans might have actually directly used lime in its more reactive form, known as quicklime?”

Studying samples of this ancient concrete, he and his team determined that the white inclusions were, indeed, made out of various forms of calcium carbonate. And spectroscopic examination provided clues that these had been formed at extreme temperatures, as would be expected from the exothermic reaction produced by using quicklime instead of, or in addition to, the slaked lime in the mixture. Hot mixing, the team has now concluded, was actually the key to the super-durable nature.

Impressive.

I think that the line of investigation of this paper is very interesting and this is the sort of research that astrophysics needs. Not
groupthink, circle-jerk big ego affirmation.

But I do not think there is an "either/or" situation here. In my view dark matter is the simple failure to recognize that gravity is nonlinear
and not Newtonian. That is, the gravitational "constant" G is a function of the mass distribution. The MOND correction is basically
the same premise since we have a G(r) which then gives a deviation from the 1/r^2 force law.

The reason for the nonlinearity is that gravitons self-interact. We see this effect in the strong force since gluons self-interact and we
get asymptotic freedom near the force center but increasing attraction away from it (Yang-Mills potential). Gravity does not have the same
dramatic amplification of the force away from masses as quarks have with the strong force. But it is enough to give us the galaxy rotation
curves without appealing to missing mass. This is not to say that there is no mass that we do not see. So a comet halo instead of a dark
matter halo is still possible but the bottom line is that Newtonian theory is only a weak field approximation.

It is funny that galaxy dynamics simulations use Newton's law of gravity. They do not use GR equations and do not even use "retarded" potentials
assuming a speed of light gravity. A weak field approximation of GR should be used for galaxies. But GR is not sufficient since it assumes a
constant G as the whole theory rests on Newton's law. We simply to not have strong field limit understanding of gravity. Black holes are not
examples of such understanding since GR does not have the strong field limit gravity as its base. In other words, black holes are mathematical
constructs from some theory and not reality. GR should be formulated starting from a variable G framework.

In cosmology, having a variable G gets around the ludicrous, ad hoc "hyperinflation" hack. There are too many such deus ex machina fixes
in astrophysics and cosmology.

Anyway, we are too far away from full understanding of reality regardless of the tone put out by "authorities" in various scientific subjects.

I think the best physical interpretation so far for quantum mechanics is from pilot wave effects. All of the key features of QM can
be captured in classical fluids when a test particle is subjected to the action of its own wake and that of others:

https://news.mit.edu/2014/fluid-systems-quantum-mechanics-0912

Photons and particles are no just passing through a coordinate map, they pass through a material entity called space (time is not a dimension
so space-time is not fundamental). That there would be wave-like effects of the space fabric is manifestly plausible.

BTW, the Copenhagen consensus on the interpretation of QM is total BS. The observer and all other systems are quantum entangled.
The idea of an observer collapsing a wave-function by observation as some sort of deus ex machina entity is ludicrous and not even based
on QM. The observer is part of any quantum system. QM is afflicted with too much philosophizing which somehow forms a groupthink.

This observer-wave-function collapse view is also subjectivist at its core. Somehow the observer creates reality by merely observing.
Obvious nonsense which has been sanctified by collective parroting. So called Einstein-Rosen-Podolsky paradox is really nothing since
no information flows from the observation of the state of one member of an entangled pair of particles (or whatnot) to the other. The
observer does not set the state he only observes it. The double slit experiment does not contradict my point, since the attempt to
measure the location of the photon (or particle) traversing the slits totally disrupts the pilot wave environment. The observer does not
create the state of any system through observation.

This is a show stopper paper in GR, but one which will be ignored:

https://arxiv.org/abs/2101.02012

The above paper demonstrates that the interior solution of a spherical fluid (i.e. mass) shell is not flat like in Newtonian theory.
The derivation cannot be challenged and the authors point out that if you use a potential that deviates from 1/r in Newton's theory
then the gravity does not cancel out in a spherical shell interior either and actually has similar "repulsive" properties near r = 0.

Note figures 2 and 4. The metric time and radius prefactors change sign in the interior just like they do in the classical Schwarzschild
(or more accurately Hilbert) solution, aka static black hole solution.

1) It is routine to claim that spherical mass shells in GR behave just like Newtonian ones and that there is no potential in the interior.
This is pure hackery that is practiced by "authorities" in the field. They are all pathetically sloppy with doing the math. Math is
not optional even in physics. GR is based on a set of equations and not just "intuition". If you can't do boundary conditions right,
then GTFO.

2) It is a dogma that the interior black hole solution has time and radius changing roles. This is patent BS since there is no law or
constraint in solving Einstein's equations that requires the sign of a prefector to stay the same. The thing that matters is the geodesics
that are described by the metric. The BH interior solution gives physical geodesics.

3) The key detail is that motion along static BH geodesics in the exterior solution equals the speed of light at the event horizon. So any
attempt to continue them into the interior violates the speed of light limit. You have attempts to "prove" that these exterior geodesics
cross the horizon and go to r=0. This includes the vaunted Kruskal-Szekeres coordinate transform. This is all BS since such transforms
do not conserve information (they are not diffeomorphisms). This is neither physics nor mathematics. A straightforward analysis of the
interior solution shows geodesics with motion towards the event horizon just as with the exterior geodesics. Similarly they also have
speed of light motion only at the horizon.

The only physical and mathematical inference is that black "holes" are 2D spherical mass shells at the event horizon.

The desire for a point mass singularity is pathological and has resulted in a corruption of GR. Einstein's intuition was right on target and
the clowns that work in his name waited until he died to shove their point mass singularity fetish full bore on the world. They claim that
so-called BH observations prove the existence of a point mass singularity. There is simply no way to infer a point mass singularity from
any astrophysical observation. A black shell can produce the same image.

One of the origins of the point mass fetish stems from the point charge solution in EM. The homogeneous Poisson equation (no charge)
gives a solution for the point charge. The reason is that the point charge is basically all vacuum so the vacuum system has to have the
exterior field as one of the solutions. The other is just a no field solution. This thinking was extended to GR and it was assumed that
there would be a point mass solution as well. But this was a desire and not impartial science. The reality is that there is no point
mass solution in GR with this approach (i.e. solving the homogeneous system). There is only a 2D mass shell solution. A point mass
solution requires cranking through the full system of equations with a source term (stress-energy tensor). No free lunch is available.

For me it is clear that spacetime in GR is an elastic, conservative fabric. So what we see in the mass shell solution is the stretching of
space near the mass (shell) and compression in the interior. (Note that time acts in the opposite way to the radial space component.)
In the exterior solution the stretching can spread into an infinite volume. But in the interior it is trapped in a finite volume so it results
in a compression away from the shell interior surface. There is no cancellation effect which you see in linear Newtonian theory. It is
singular even for mass shells well beyond the Schwarzshild radius because spacetime deformation has a roughly 1/r dependence. If it
was 1/r^c where c > 1, then there would be no singularity (in spacetime curvature) at r=0. (This may require c to be big enough and
for sure c=2 would not produce a divergence).

But it has been forgotten for unjustified reasons. Science is not about the wants and needs of some personalities.

This reminds me of all the covid "studies" that are trotted out to claim that vaccines are necessary and that other options are dangerous.

Comment:

In this experiment, a single photon is aimed at the double-slit. If it passes through the left slit, it will hit a crystal placed behind the slit on the
left side of the crystal; if through the right slit, it will hit the crystal on the right side. We will not actually be measuring the interference vel non
of the incoming photon, but of the subsequently generated photons.

When the incoming photon hits the crystal, it is destroyed and a pair of entangled photons is generated by the crystal at the spot where it hit.

Because of entanglement, the properties of the two entangled photons will forever be correlated. Therefore, if we can later identify one of the
entangled photons as having come from, say, the left side of the crystal, we will thereby know, retroactively, that its twin also came from the left
side of the crystal, so that we will then know where both entangled photons came from.

This is not the same as a double slit experiment. Interaction with the crystals is not a conceptual triviality. The two crystals are entangled
quantum systems added to the double slit with which any photon or electron is entangled as well.

None of the claims of proof studies for the double slit experiment even start to consider the pilot wave view. There is no way in which to
measure the "true path" without interfering with the wave function of both the traversing particle and the double slits. The slits may be
considered classical and an implicit linearization invoked where they are not considered as part of the QM system, but that is just an
approximation.

Anyway, the idea that a magical observer creates reality by observing is infantile nonsense. It seems there is a lot of effort to stuff this
subjectivist garbage down everyone's throat for over 100 years now.

Solution for a point mass in GR:

http://www.m-hikari.com/astp/astp2007/astp1-4-2007/castroASTP1-4-2007.pdf

(ignore the stupid warning about downloading, the Vixara link is down).

I guess we now know what super-secret submarine propellers are like. It is one of these ideas that seems so obvious in hindsight.
Typical propellers based on little wing sections are a primitive first attempt.

Also, what do you think about the movie "The birth of the Universe" (recent Russian movie that includes the Sky Scholar guy and pushes the Aether theory...though Sky Scholar was not involved in pushing aether)? One logical contradiction of the whole aether thing seems to be that they say that it's denser further up in the atmosphere and so it "displaces" the air molecules downwards, explaining the accumulation of air at the surface (since they seem to want to derive gravity from aether density), but then they say that all atoms are actually made of aether, which would include air molecules...seems it's just rank speculation and the whole movie reeks of pantheistic and syncretistic undertones. wrote:

I have not seen this movie.

I think aether is a failed attempt to ascribe fluid properties to space. Gravity is supposedly then an aether flow.

That space is material is a fact. It has volume and if GR is to be believed it can also be deformed. Abstracting it as a coordinate
system does not remove the need for a material medium. The mistake is to try to paint this medium with understanding
derived from our every day experience such as solids and fluids. The latter are collections of atoms whereas space(-time) seems
to be some sort of quantum "foam" with granularity at the Planck length scale. The full set of features of this medium are unknown
and it may have large scale quantum mechanical properties in the sense that the organization is not confined to the Planck scale.
We have theoretical attempts such as holography (https://en.wikipedia.org/wiki/Holographic_principle).

I think the speed of light limit is a manifest demonstration of material properties of space. Why the value of "c" that we have
and not anything else? Why not infinity as in Newtonian theory? The cosmological models that appear more physically plausible
(e.g. no deus ex machina hyperinflation) are variable "c" theories. It would make sense for the transmission properties of
the space medium to change with time if there is indeed some sort of Big Bang expansion. But I have some skepticism for
the Big Bang since it smells like a creation epic. If we had this "initial singularity" then how did we get out of it and what
if there is an ongoing cycle of Big Bangs at some vast number of points throughout a vastly bigger universe?

People have a hard time with special relativity because it is corrupted by a subjectivist interpretation. SR flows from
the Lorentz equations which happen to leave Maxwell's EM equations invariant. Attribution of these properties to Einstein
and Lorentz is pure wankery. Poincare had the correct interpretation of the Lorentz equations. They are absolute with
the true rest frame being the medium frame where the photons live. There is no contradiction. The contradiction is in
Einstein's "relativity" where an implicit "renormalization" is done for every moving observer. This sets up nonsensical
physical inferences such as the twin's "paradox". The reality is that any moving observer has a Lorentz distorted frame
even if they can't tell that they are in one. The universe cares about objective reality and all observers and not subjective
perceptions of some observer. Moving inertial frames do not all have the same geometry as the v=0 frame. They have
the geometry of v /= 0 frames. Setting v = 0 for every moving observer is BS. With the "absolutivity" interpretation of the
Lorentz transform there are no more paradoxes (aka logical contradictions).

GR happens to break relativity. It is a non relational theory and Einstein's attempt to get around this was to fixate on general
covariance where "no coordinate system is special". But coordinate freedom has nothing to do with relativity. The solution is
for a global space-time which does not change depending on how fast some observer moves. General covariance is clearly valid
but it has allowed scum to introduce backdoor nonsense. Only diffeomorphic transformations make physical sense since they
preserve information. (No points being mapped to lines and planes to lines, etc.) But you will see routine use of non-diffeomorphic
transforms in GR to "prove" various claims. No coordinate system may be special, but that is not equivalent to "any coordinate
transform is allowed".

http://hps.org/publicinformation/ate/q13412.html

You need neutron radiation to damage metals.

https://en.wikipedia.org/wiki/Neutron_embrittlement


The beam idea would have to be an aperture leak of some sort where high energy neutrons or nuclei are still able to induce fusion.
Trying to induce fusion in a particle beam far from the source is not realistic since there is no confinement in the beam. You are
really looking at using fusion in some chamber to generate a high energy beam of daughter particles. The problem with all particle
beams is that they disperse too fast. People have been trained by sci-fi movies and TV to think that they are practical and better
than lasers. Using coherent projectiles (rail gun launched if needed) is vastly superior to using a dissipating particle beam.

Nice video going against the groupthink.

There is another absurdity in modern physics that shows the corruption.    Anything traveling at the speed of light cannot have any
dimensional extent along the axis of travel.    So if we ignore the detail that mass cannot travel at the speed of light, a rod of any
length aligned parallel to its axis of travel will appear to have zero length if its speed is that of light.   So how can a photon have a
spatially extended wavelength?   Even if it actually is a localized wave to us it would appear to have no spatial extent along its axis
of motion.   Just apply the Lorentz transform to any wave packet to see this.

A sane explanation would be that photon "waves" are intrinsic and do not transform like objects composed of atoms via the Lorentz
equations.   These quantized waves are a demonstration of the existence of a space medium.   Much like water waves exist because
there is a body of water to sustain them.   Of course, the EM waves are not subject to the same equations as the water waves.  

So there is no "irregular" photon frame which is a good indication that the concept of frames for moving objects is BS.   There is only
one frame and all objects with any motion and EM waves exist in this frame.   The frame of the universe and ultimately the absolute
rest frame.   Photons and EM waves propagate in this frame supported by the material entity known as space.   There is no partition
of reality into different physical realms based on relative motion.   No BS paradoxes are possible since any Lorentz deformation of moving
objects is intrinsic and relative to the absolute rest frame and not relative to each other.

If you move with v increasing to c, you would still see light moving at the speed of light.   That is the nature of reality as reflected in
the Lorentz transform (a conservation property of Maxwell's equations).   Moving observers are distorted in manner that "hides" their
motion from themselves.  They cannot measure their own Lorentz distortion.   All they can perceive is differences in the Lorentz distortion
of other objects.