Physics General Subjects Thread

Another article which properly solves for the point mass problem in GR:

http://inspirehep.net/record/742738?ln=en

Note the discussion at the end about the voodoo physics where by some magic a stress-energy tensor is
not needed to solve systems which have mass and charge. That is just epic BS. The touted black
hole solution does not have any point mass singularity. This homogeneous solution is being grossly
misrepresented and in fact is just a repulsive space-time bubble which squeezes out a flat-space time
into a semi-infinite shell. Actual singular (point mass) solutions do not have an event horizon.

Found this article about crack propagation. I have thought for some time that physical properties of the Earth can predict border formation in countries. By unknown variables of property. Such as altitude or area shared with sea coastline or temperature. Leading to fracture. Can this be simulated and predicted in computer? Like fracture in materials? If you look at small land mass connecting big land mass, then you get lots of small countries. Fractures. Or an island nation near big land mass, creates lots of small country or fractures. Area near sea contain fractures that run parallel to coast....

https://www.google.co.uk/amp/s/phys.org/news/2010-03-physicists-mysteries-formation.amp

nomadski wrote:Found this article about crack propagation. I have thought for some time that physical properties of the Earth can predict border formation in countries. By unknown variables of property. Such as altitude or area shared with sea coastline or temperature. Leading to fracture. Can this be simulated and predicted in computer? Like fracture in materials? If you look at small land mass connecting big land mass, then you get lots of small countries. Fractures. Or an island nation near big land mass, creates lots of small country or fractures. Area near sea contain fractures that run parallel to coast....

https://www.google.co.uk/amp/s/phys.org/news/2010-03-physicists-mysteries-formation.amp

If they have an algorithm (e.g. set of governing equations) for this crack formation/propagation process then it can be implemented in
computer code. But I think there are many empirical parameters in such cases and not some tightly closed set of equations that only need
initial and boundary conditions.

For example, there are no governing equations known for cells and organisms. We know about all sorts of processes but have no
compact representation of them. And it is clear that cells and organisms are dynamical systems.

Einstein personality cult.

Some facts to consider about the "all time genius":

1) His 1905 paper on Special Relativity has zero references. That such a paper was published indicates corruption by the editors.
Poincare published extensively on this very subject, including the Lorentz transform and E=mc2 before Einstein. But Einstein
does not give any credit to Lorentz and to Poincare and others who were covering the same material in a non-trivial way. I am
not talking about hints of similarity, I am talking about core features of the theory. Poincare even included relativity in
the title of his theory and identified the growth of inertia as the speed of light is approached and that the speed of light
was the limit in all inertial frames.

The norm for scientific publications is to do a literature search and that has been true sine well before 1900. Einstein's SR
paper was not publishable since he was ignoring previous research and taking credit for it. Some time later Einstein gave some
credit to Lorentz but kept ignoring Poincare. Some will claim that SR is a deep insight by Einstein. That is BS since SR
naturally pops out of the Maxwell Electro-Magnetic equations since they are invariant under Lorentz transforms. That is,
inertial frames which are governed by Maxwell's equations (forget about gravity and general relativity for now) transform
via the equations of Lorentz. These transforms are substantially different from the Gallilean transforms of Newtonian physics,
and automatically include length contraction, time dilation and failure of simultaneity.

For petty career and ego reasons scientists have been trying to pretend that they discovered SR when it has emerged from
empirical observations. SR does not belong to Einstein.

2) Eddington, staged what amounts to a hoax by claiming to have measured refraction of light around the Sun "proving"
General Relativity during eclipse events in Africa in 1919. This data was totally cherry picked and he was claiming
a measurement accuracy 200 times larger than was possible with his cameras. This farce was popularized in the press and
turned Einstein into a celebrity overnight. The so-called three tests of GR do not prove its validity. There are an
infinite number of theories including quantizable field theories that can reproduce all three tests but do not agree
with GR.

In the case of GR, Einstein can be given the credit. But he never put his foot down when his theory was abused. It
is actually sad to see his 1939 paper totally ignored while the joke by Schneider and Oppenheimer from 1939 extolled
as proof that GR allows black hole solutions. The latter paper used an unphysical stress-energy tensor which totally
ignored radiation pressure to get their result. If they had accounted for any radiation pressure, they would never
have obtained any solution forming a horizon. The proper stress-energy tensor for a perfect fluid is

(rho + p) U^iU^j - p g^{ij}

(beware a lot of references ignore the minus sign in the second term and are thus engaged in voodoo mathematics).
This stress-energy tensor can be adapted to the "collapsing dust" case of Schneider and Oppenheimer (1939) since
even a tiny radiation pressure from the dust (which is supposed to be like the galaxies in the universe) produces
a strong negative feedback on the metric (g) curvature. As the mass gathers in progression to infinite density,
it starts to form a horizon-like amplification of the radial prefactor, B(r):

g = A(r)dt^2 - B(r)dr^2 - C(r)d(omega)^2

For the black hole solution B(r) is infinity at the horizon radius (r_s). This infinity just does not pop out of
nowhere. It must form. Here is where the radiation pressure comes in. The -p B(r) term in the stress-energy
tensor will start to explode even if p is very small. Since this term acts to damp the formation of infinite density
it is clearly acting to suppress the formation of any event horizon. As long as there is any radiation pressure,
the horizon will fail to form for the dust system of Schneider and Oppenheimer. In the case of a collapsing
star a similar resistance develops, but we are dealing with a compact object and not dispersed dust. For a star
the pressure of the fluid (star material) acts as a positive term in terms of gravity. So it can theoretically
overcome the radiation pressure. But there is a rub in this logic.

In his 1939 paper Einstein identified an ultra-important physical aspect. Any BH collapse with the formation of
a horizon requires matter to travel at the speed of light at the horizon. This means that mass turns into a photon
gas at and inside the horizon. So we really need to know what happens to regular matter as the horizon starts to
emerge. If the matter dissociates into photons before an actual singularity of B(r_s) forms, then we have a
strong negative feedback that suppresses the formation of both infinite density and any event horizon. Although
some state that is almost like a black hole can develop where we have a sphere of enormous density with an outer
thick shell where B(r) is also very large. For all intents and purposes no real black hole forms but a black object
does since any photons leaving this potential well will experience extreme red-shifting.

Modern astrophysics has gone off the rails.

The key detail in this farce is that no amount of post-processing of observational data can create information that you have
not obtained by measurement. In order to "interpolate" a 1250 fold increase in resolution and obtain structure below your
pixel size, you need that much more information in some other form to do it.

For example, suppose I have a 3x2 (or 3x6, whatever) pixel resolution camera and I need to image at 150x90 pixels. Then
I need each pixel to be able to capture extremely small variations in intensity and also to be able to scan the region of interest.
Over thousands of experiments and assuming the image does not change much during my measurement period, I can
actually get enough pieces of information to assemble a 150x90 reconstruction. There is a process to "feel" over the true
shape of the object by repeatedly touching it and recording variations.

So in contrast to the claims of some of the idiot "scientist" posters in the comments below the video, no fancy algorithm
can substitute for actual measurements. The video demonstrates that no such low-res scanning campaign was done to
accumulate thousands of pieces of information to be able to reconstruct the true image. The data is limited to the 3x2 pixels
shown and is thus forever trapped at this resolution.

Also, in this case the argument that you do not need 150x90 pixels to resolve a 150x90 image cannot fly since the details
are all well below the pixel size. If the image looked like the 3x2 pixels to start with, then trivially no higher res sampling is
needed.

Another cherry on top of this fraud turd cake, is that there is no physics model that would allow you to reconstruct sub-pixel
structure based on some set of parameterizations (same thing as equations and algorithms). For earth system modeling we
can have parameterizations of sub-grid scale processes such as convection based on the thermodynamics of water vapour and
assumptions about convective structure based on observations (and these parameterizations do not actually capture convective
plumes, but make statements of their stastical impact in the grid box). The BH image is not subject to some empirical equations
that map the high res image to the low res blotch. Even imposing assumptions about sphericity and light bending bright
halo, there is simply too much degeneracy in the blotch for any reconstruction. The coarse-res blotch image blends
the high-res structure completely.

The above video fits into this thread because pilots are not taught enough about atmospheric dynamics to safely fly small planes
or large planes. You can blame pilot cockiness, but in the above case I see the influence of turbulence. The pilot made the
mistake of flying way too low to the ground. He was in the lower shear-turbulence driven atmospheric boundary layer which
is typically the first 300 meters when the boundary layer height is 1000 meters. You can ask how is he supposed to take off
and land without going through this layer. Well, he takes his chances and this layer is not always lethal to small planes. But
when the conditions are right for turbulent structures to emerge, he is f*cked.

From the flight data recorder information shown graphically in the video you can see a clear wavelength to the pilots's near
surface skimming (almost hitting the water at one stage). He was being trapped by intense surface vortex rolls which confused
him and caused him to jack up his attitude which caused him to lose control since the type of plane he was flying was not a jet
and was not able to handle the sharp vertical ascent. It also appears that in addition to any instability due to his
reaction to the initial two vertical displacements, a near surface vortex tube facilitated his crash directly by exerting
downward thrust that the ultra-light plane could not handle.

The horizontal vortex tubes are organized turbulence rolls produced by wind near the surface. They are related to Kelvin-Helmholtz
instability but also coupling with surface heating and shear induced by surface drag. Notice how the most unstable
part of a typical aircraft journey is near the ground on take off and landing. Big airlines can handle this turbulence (except for
microbursts and extreme wind driven shear such as the Smolensk disaster). Small planes just get tossed around like garbage.

John Denver, the singer, disappeared in the Rockies in his light plane more than likely because he got caught in a "mountain wave" or
inertia-gravity wave generated by flow over topography if not by near surface turbulence which can be easily induced in
a rough terrain or even flat terrain.

The Sukhoi Superjet 100 crash in Indonesia during a demonstration flight was an example of a cocky and ignorant pilot getting
into a situation which he could not handle. The uneducated pilot thought that his flying skills are enough to overcome
atmospheric conditions. He could not have been more wrong and the volcanic ridge inertia-gravity
wave which he encountered with his low altitude stunt dropped the planes altitude enough for him to crash into the ridge.
No amount of skill could have prevented the altitude loss since the wave associated circulation governed the lift and not
the wing shape, angle and speed of the aircraft.

Gimmick, zero science for the masses in Hollywood movie trash (and anime).

One obvious fail of a double bladed (non-staff) sword is that one actually reduces the cutting force for each blade
by 50%. The more blades you add regardless of their separation, the less force transferred from the
arms to each blade. For two blades there will be sufficient damage for this gimmick to be not a total fail, but
for enough blades there will be no deep cuts at all. In fact with enough closely spaced blades one can walk
with bare feet on their edges and not get mutilated. The force of gravity pulling the blade walker down is not
exerted on a single blade but divided among contacts with many blades. To get the same cutting effect from
each blade the downward force needs to be increased accordingly.

Actually now the real evil of the light sabre is Disney... you will notice in the new Disney Star Wars universe a light sabre cannot sever limbs any more... now it is pathetic and only cuts parts off drones... pathetic...

dino00 wrote:

GarryB wrote:Actually now the real evil of the light sabre is Disney... you will notice in the new Disney Star Wars universe a light sabre cannot sever limbs any more... now it is pathetic and only cuts parts off drones... pathetic...

3 awful movies

The objective is to dumb everything down. Anything that stimulates thought, such as a good movie plot, is being systematically removed.
One may say "don't attribute malice to what is a case of incompetence" but that would not explain the secular drift in the whole industry.

I recall them talking about 9 movies back in the 1980s. So it looked like they had scripts for a long time and it would have been better if
they used them. But it looks like they did not have any scripts and we got a progression towards zero over 40 years.

kvs wrote:

dino00 wrote:

GarryB wrote:Actually now the real evil of the light sabre is Disney... you will notice in the new Disney Star Wars universe a light sabre cannot sever limbs any more... now it is pathetic and only cuts parts off drones... pathetic...

3 awful movies

The objective is to dumb everything down.   Anything that stimulates thought, such as a good movie plot, is being systematically removed.
One may say "don't attribute malice to what is a case of incompetence" but that would not explain the secular drift in the whole industry.

I recall them talking about 9 movies back in the 1980s.   So it looked like they had scripts for a long time and it would have been better if
they used them.   But it looks like they did not have any scripts and we got a progression towards zero over 40 years.

Word has it that George Lucas first wife was the real reason for the original triad of movies success, and George cribbed too heavily from the Monomyth.

magnumcromagnon wrote:

kvs wrote:

dino00 wrote:

GarryB wrote:Actually now the real evil of the light sabre is Disney... you will notice in the new Disney Star Wars universe a light sabre cannot sever limbs any more... now it is pathetic and only cuts parts off drones... pathetic...

3 awful movies

The objective is to dumb everything down.   Anything that stimulates thought, such as a good movie plot, is being systematically removed.
One may say "don't attribute malice to what is a case of incompetence" but that would not explain the secular drift in the whole industry.

I recall them talking about 9 movies back in the 1980s.   So it looked like they had scripts for a long time and it would have been better if
they used them.   But it looks like they did not have any scripts and we got a progression towards zero over 40 years.

Word has it that George Lucas first wife was the real reason for the original triad of movies success, and George cribbed too heavily from the Monomyth.

I know that Lucas exploited Dune and other fantasy works but I did not know he was pulling an Einstein like in the case of the photoelectric
effect paper where he never acknowledged that it was work mostly done by his Serb wife. She also contributed to his other science
efforts. Einstein was generally abusive to his wife and she was not just some gold digging whore.

I will concede that the originals are overhyped. And I find a lot of the negative reviews on youtube to be contrived. No
movie is ever going to have a physics monograph for a script. The 1999-2005 trilogy was definitely better than the Disney
batch.

kvs wrote:

magnumcromagnon wrote:

kvs wrote:

dino00 wrote:

GarryB wrote:Actually now the real evil of the light sabre is Disney... you will notice in the new Disney Star Wars universe a light sabre cannot sever limbs any more... now it is pathetic and only cuts parts off drones... pathetic...

3 awful movies

The objective is to dumb everything down.   Anything that stimulates thought, such as a good movie plot, is being systematically removed.
One may say "don't attribute malice to what is a case of incompetence" but that would not explain the secular drift in the whole industry.

I recall them talking about 9 movies back in the 1980s.   So it looked like they had scripts for a long time and it would have been better if
they used them.   But it looks like they did not have any scripts and we got a progression towards zero over 40 years.

Word has it that George Lucas first wife was the real reason for the original triad of movies success, and George cribbed too heavily from the Monomyth.

I know that Lucas exploited Dune and other fantasy works but I did not know he was pulling an Einstein like in the case of the photoelectric
effect paper where he never acknowledged that it was work mostly done by his Serb wife.   She also contributed to his other science
efforts.   Einstein was generally abusive to his wife and she was not just some gold digging whore.  

Nostalgia aside - Star Wars was really shit and simplistic universe. Science was watered down and characters were two dimensional. As you mentioned Dune.. it's literally a bible for any self respecting Sci-fi fan, even if it's even less "technical".

At the time they were ground breaking... the budget special effects were convincing... but ultimately the fundamental problem with Star Wars is that when you break it down it is a kids movie... Lucas was interested in the kids market so to get a PG13 rating it couldn't be realistic or deep.

A comparison of the time was Alien... the focus was an alien species and its fight to survive and the humans fighting to survive to avoid becoming victims of the Alien and its reproductive cycle... but Alien as a movie had a genuine female lead that wasn't bullshit, with solid acting and a good storyline if limited... ie survive and take the enemy out at all costs to save your species.

She wasn't the ship commander or some show off woman pretending to be a butch man... she was a woman in a shit situation that used her brain to survive.

These days if they made a new reboot of the Alien movie she would have been the commander on a space ship of all black and asian women which means they all would have needed to survive because women are strong.

Star Wars only had a hand full of women in that part of the galaxy... what it really needed was a female bad guy... and the one they used was a female stormtrooper and honestly I didn't actually notice she was a woman till she was interviewed on Graham Norton and she was the same big woman as the one in Game of Thrones...

I think she should have lost the mask earlier and Kylo Ren should have kept his on... he wasn't scary at all... just a lill boy.

https://www.bbc.com/news/science-environment-52663694

No free lunch with chemicals.

Maybe the solution is being proactive... a large electric powered airship lifting thousands of bottles of O3 to be released directly into the ozone layer to boost its size and shape and density...

And then finding refrigerants that do break down that are safer...

Seeding the ozone layer could give us more time and more leeway to find a more permanent solution.

Obviously more research into what makes up the various layers of the atmosphere and their effects on conditions on the surface of earth would be a good thing... we don't want to fix something only to find it breaks something else...

GarryB wrote:Maybe the solution is being proactive... a large electric powered airship lifting thousands of bottles of O3 to be released directly into the ozone layer to boost its size and shape and density...

And then finding refrigerants that do break down that are safer...

Seeding the ozone layer could give us more time and more leeway to find a more permanent solution.

Obviously more research into what makes up the various layers of the atmosphere and their effects on conditions on the surface of earth would be a good thing... we don't want to fix something only to find it breaks something else...

A lot of people after watching TV and Movie treatment of science have no idea how difficult it can be. Throwing some time and money
at science problems is not guaranteed to result in a linear progression to solutions and advances. In the above case we have a refrigerant
that does not destroy the ozone layer but exposes life to long lived decay products that are more than likely carcinogenic. It is like
whack a mole. Solving one problem can and often does create new problems. Industrial pollution is an example of this. Lots of
production line functionality comes at the expense of a toxic legacy.

To some extent it is a matter of research investment. It jut so happens that ammonia (NH3) is a good refrigerant and does not
destroy the ozone layer since it is chemically destroyed in the troposphere. CFCs and other more stable compounds last longer and
get chemically destroyed by photolysis in the upper stratosphere. NH3 has been known for a long time but there is a phobia of it
being toxic and able to cause blindness. That dates back to those old fridges where people would use ice picks to get rid of the
freezer ice and puncture the coolant tubes. Obviously this a non-issue today. In the case of cars even there is a car wreak where
the ammonia coolant escapes it is not going to kill the occupants of the car since it is venting into the atmosphere and not into
their eyeballs. NH3 is rather volatile so it lofts rapidly away from the surface. Like H2. People are full of ridiculous phobias resulting
from ignorance and misinformation.

I suspect the use of custom chemicals instead of widely available NH3 is a racket. Somebody is making lots of money selling a boutique
item (the specialized refrigerant) instead of the cheaper ammonia.

More evidence that modern science has gone off the rails into the realm of Voodoo.   This is especially true for fields such as
astrophysics and cosmology because the ratio of speculation to empirical observation is very high.   Some of the vaunted
papers alleging to confirm GR in all of its ignorant glory actually use GR to make meaning of the observations.   No, this is
not using the observations to validate the theory, this is literally using the theory itself to then validate the theory.  That is
a stupid tail chasing circularity exercise.  

In the above there is lots of talk about "experimental proof".   This is unmitigated BS no mater how it is worded.   This whole
exercise is an application of a speculative theory to "prove" something that is not provable without real world experimental
validation.

As I posted up-thread, the analysis of black holes and such in astrophysics pretends that a six pixel observation can be interpolated
by some fancy technique to an over 100 x 100 pixel image.   Also, how does one measure absence of radiation?  All we have
in astrophysics is spectral measurement of emissions.   We have no deep space probes doing gravimetric observations.  The cherry
on top of this obnoxiously arrogant turd cake is that we do not even know all the states of matter.   What, for example,
is a quark condensate in terms of interaction with photons.   We can't just assume it that our scale regime applies to all
physical scales.  There is no evidence for such behaviour of physics.  

For all we know, these so-called GR black holes could be super compact states of matter (which may include dark matter) that
radiate massive photons and not regular massless ones.    The massive photons may decompose en-route giving a dispersed
background far infrared or microwave field of regular photons.  

There is way too much speculation being passed off as established universal truth.   This may advance the careers of
scientists but is not science.

More fun from the same Youtube source. But he is actually spreading the official physics line so cannot be dismissed as a crank.

In the above video we have supposedly an optical illusion due to the black hole jet being at 15 degrees from the line of sight to its
source. But visual tracking is done over several years of the BH jet clumps. Their angle of travel is irrelevant since they are the
emission source being tracked. The alleged optical illusion is nonsensical since somehow the isotropic emission from the jet clump(s)
is arriving at our location in a differential way. Unless it is being refracted or gravitationally lensed somehow this is not possible.
The direction of travel of the clumps does not change the fact that it is their isotropic emissions that are being used to identify
their position. There is no weird hall of mirrors effect where the true position is not being determined. They are exactly where they
are (accounting for the finite speed of light time lag to reach us).

So the real problem here is that the distances which are being claimed for the travel of the jet clumps are wrong. And this is, by far,
the most likely case since the errors of location of stars and black holes produced by astronomers can be large. For example, the super-giant
star UY Scuti was supposed to have been the largest in the known universe. Now it is not even in the top 10 since its location was
wrongly determined.

An example of the tunnel vision in modern science. Since the iridium layer happens to occur near the end of the pink limestone sequence, it must be responsible for the mass extinction event. Always obsessed with a silver bullet "explanation". In this case we have an epic case of BS.

1) In order for the thick layer of pink limestone to form (idiotically labelled as "dinosaurs" present), the oceans must have been in a
reducing state. That is, they were anoxic preventing the oxidation of iron and giving the pink tint to the limestone. Limestone forms
by precipitation of calcium carbonate. The carbonate dissolved in sea water is huge so even under anoxic conditions it does not disappear.
Such pink limestone layers are exclusively associated with major warming events. Events of the type that lead to mass extinctions.

2) The iridium layer is clearly not causally related to the pink limestone since it comes almost right at the end of its formation. Here we
have more hand waving plausibility arguments. Even very thin layers of rock cannot be dated down to the year. So the iridium layer
can have formed from the meteor impact any time from a few centuries to thousands of years before the end of the warming period
and the return of normal upper ocean oxygen levels.

3) Even if the meteor could result in enough aerosol loading to stop photosynthesis for a couple of years (aerosols are flushed out in under two years no matter the amount since they sediment and are removed by cloud formation and rain) it would not explain the mass extinction in the oceans. Even in the upper layer, oceans have much longer mixing timescales compared to the atmosphere. So stopping photosynthesis would not result in instant die off.

The role assigned to the meteor impact in driving the extinction is exaggerated. The mass extinction was already in progress and this
event was a contributing factor. But presenting it this way does not make it sexy enough for science careers to be made.

Finally more reality is seeping into astrophysics. Before running around claiming that every "dark object" is a black hole, first make sure it is not
a condensed state of matter. Just because it does not occur naturally on Earth, does not mean it does not exist elsewhere. Especially in
extreme gravitational wells.

There is still too much BS about black hole "observations". Like the recent claim to have imaged M87. The actual measurement data is
only a few pixels, yet through interpolation and voodoo chicken sacrifices we get a "reconstruction" consisting of thousands of pixels.
And the reconstruction looks like what any star would look like if you gamma shifted the image. The bright halo is the effect of
tangential view at the light emission source. More photons reach the telescope from the grazing angles than from the center of
the star's disk because the integrated emission path is smaller. This is like the opposite of the effect you see when you look at our
Sun on the horizon and at mid-day. The colour shift is because there is more attenuation and scattering of the shorter wavelengths
due to a longer path through the atmosphere. Stars don't have a discontinuous surface with nothing above it, they have a thin
fuzzy outer layer that will shine in every direction, a sort of "atmosphere" which is volumetrically emitting light.

Claims that astrophysicists can measure the event horizon are a pure lie. No black hole is close enough to enable our passive
detection systems to measure with this sort of resolution. That is why we have BS like the M87 "image" which is literally something
from next to nothing.

kvs wrote:
Since the iridium layer happens to occur near the end of the pink limestone sequence, it must be responsible for the mass extinction event….

The impact theory would be falsified by unreworked dinosaur (or mosasaur etc) remains stratigraphically above the impact signature. To my knowledge none have been found.

That is, they were anoxic preventing the oxidation of iron and giving the pink tint to the limestone.

Benton's When Life Nearly Died left me with the impression red(dish) coloration indicates oxygenated conditions and darker strata anoxic.

Such pink limestone layers are exclusively associated with major warming events.   Events of the type that lead to mass extinctions.

Was there a mass extinction during the Paleocene-Eocene Thermal Maximum? Not to my knowledge.

3) Even if the meteor could result in enough aerosol loading to stop photosynthesis for a couple of years (aerosols are flushed out in under two years no matter the amount since they sediment and are removed by cloud formation and rain) it would not explain the mass extinction in the oceans.   Even in the upper layer, oceans have much longer mixing timescales compared to the atmosphere.   So stopping photosynthesis would not result in instant die off.  

A collapse of productivity lasting a year or so could have--and apparently did--finish off the mosasaurs, ammonites and other mesozoic life. Btw energy may not have been the only issue; loss of photosynthesis probably also meant cooling--not good for the thermophilic marine life of the period.

The role assigned to the meteor impact in driving the extinction is exaggerated.

Initially I was no fan of Alvarez and argued for other factors. But for quite some time the impact theory has been firmly established. Some years ago a symposium reviewed all the evidence and confirmed it.

 

The mass extinction was already in progress

Researchers have long claimed dinosaur diversity waned in Laramidia by latest Maastrichtian time. Some studies, however, conclude there is no evidence for a similar decline in South America or Europe (In fact there seems to have been preliminary extinction in Europe but not much of it). Even in Laramidia, the apparent drop in diversity does not appear like a "mass extinction already in progress" since the last fauna persisted to the K-Pg.