I know, I know, this is trivial, but it is so hysterically funny!
Someone pointed this out to me and I couldn't stop giggling. So of course I have to share it with all of you! This is a jobs ad from Kennedy-King College, one of the City Colleges of Chicago. They are looking for someone to be an adjunct physics faculty member to, presumably, teach physics.
I'm doing a screen capture here, because I expect someone there will see this and make corrections to it soon... or maybe not!
I am guessing that two different people did this, because the category for the job is correct (circled in green), and the required qualification is also spelled correctly, but then it goes hysterically wrong in the job description. It says:
ADJUNCT FACULTY PSYCHICS/ PART-TIME
CITY COLLEGES OF CHICAGO, KENNEDY-KING COLLEGE
Kennedy-King College is currently seeking a part-time Faculty to teach Psychics during the Fall 2018 semester.
Well of course they're looking for Psychics. This is because they want a part-time Faculty to teach it during this upcoming Fall semester!
Dear Kennedy-King College, you may want to have someone proof-read your ad. The spell-check would not have flagged you for this hilarious error. And for an academic institution, this is an embarrassing boo-boo. Having psychics to teach physics is like having heretics coming in to teach Sunday School.
The team compared the position and velocity measurements from GRAVITY
and SINFONI respectively, along with previous observations of S2 using
other instruments, with the predictions of Newtonian gravity, general
relativity and other theories of gravity. The new results are
inconsistent with Newtonian predictions and in excellent agreement with
the predictions of general relativity.
.
.
.
The new measurements clearly reveal an effect called gravitational redshift.
Light from the star is stretched to longer wavelengths by the very
strong gravitational field of the black hole. And the change in the
wavelength of light from S2 agrees precisely with that predicted by
Einstein’s theory of general relativity. This is the first time that
this deviation from the predictions of the simpler Newtonian theory of
gravity has been observed in the motion of a star around a supermassive
black hole.
For those who are purist and prefer the thin-crust, Neopolitano-style pizza, this one might be right up your alley.
This preprint on ArXiv tackles the question on whether baking such pizza is better done in a stone over rather than the standard metal ovens. Which one do you think will win?
Stone ovens heat up to very high temperatures, higher than typical home ovens. But ceramic or stone surface also has low thermal conductivity while having a high specific heat. It means that it retains heat longer and does not cause the dough to burn. It is why this is also the preferred way to bake rustic, crusty bread.
I guess we all just have to build a brick pizza oven in our backyards! :)
A lot of people are ignorant of the fact that a smartphone, or any device, for that matter, is a result of research work done by many people and organization and over a very long time. The iPhone was not solely the work of Apple. Apple benefited from all the scientific and technological progress and accumulation of knowledge to be able to produce such a device. These knowledge and progress are often done many years ago by researchers who work on a particular topic that eventually found an application in a smartphone.
I found this interesting website that highlights how research that originated out of universities under various funding agencies, resulted in the smartphone that we currently have. It lists one aspect of each of the major component of a smartphone that had it initial incubation in university research. A lot of these research work is physics-related. It is why I continue to say that physics isn't just the LHC or the Higgs or the blackhole. It is also your MRI, your iPhone, your GPS, etc...
If you need more background info on this, check out this page.
Another giant in our field, especially in elementary particle physics, has passed away. Burton Richter, Nobel Laureate in physics, died on July 18, 2018.
Richter’s Nobel Prize-winning discovery of the J/psi subatomic particle,
shared with MIT’s Samuel Ting, confirmed the existence of the charm
quark. That discovery upended existing theories and forced a
recalibration in theoretical physics that reverberated for years. It
became known as the “November Revolution.” One Nobel committee member at
the time described it as “the greatest discovery ever in the field of
elementary particles.”
He would be shortchanged if all the public ever remembers him is for his Nobel Prize discovery, because he did a whole lot more in his lifetime.
A lot of people use Khan Academy's video lessons. I know that they are quite popular, and I often time get asked about some of the material in the video, both by my students and also in online discussions. Generally, I have no problems with their videos, but I often wonder who exactly design the content of the videos, because I often find subtle issues and problems. It is not unusual for me to find that they were inaccurate in some things, and these are usually not the type of errors that say, an expert in such subjects would make.
I was asked about this photoelectric effect lesson by someone about a month ago. I've seen it before but never paid much attention to it till now. And now I think I should have looked at it closer, because there are a couple of misleading and inaccurate information about this.
Here is the video:
First, let's tackled the title here, because it is perpetuating a misconception.
Photoelectric effect | Electronic structure of atoms
First of all, the photoelectric effect doesn't have anything to do with "structure of atoms". It has, however, something to do with the structure of the solid metal! The work function, for example, is not part of an atom's energy level. Rather, it is due to the combination of all the atoms of the metal, forming this BANDS of energy. Such bands do not occur in individual atoms. This is why metals have conduction band and atoms do not.
We need to get people to understand that solid state physics is not identical to atomic/molecular physics. When many atoms get together to form a solid, their behavior as a conglomerate is different than their behavior as individual atoms. For many practical purpose, the atoms lose their individuality and instead, form a collective property. This is the most important message that you can learn from this.
And now, the content of the video. I guess the video is trying to tackle a very narrow topic on how to use Einstein's equation, but they are very sloppy on the language that they use. First of all, if you don't know anything else, from the video, you'd get the impression that a photon is an ordinary type of "particle", much like an electron. The illustration of a photon reinforced this erroneous picture. So let's be clear here. A "photon" is not a typical "particle" that we think of. It isn't defined by its "size" or shape. Rather, it is an entity that carries a specific amount of energy and momentum (and angular momentum). That's almost all that we can say without getting into further complications of QED.
But the most serious inaccuracy in the video is when it tackled the energy needed to liberate an electron from the metal. This energy was labelled as E_0. This was then equate to the work function of the metal.
E_0 is equal to the work function of the metal ONLY for the most energetic photoelectrons. It is not the work function for all the other photoelectrons. Photoelectrons are emitted with a range of energies. This is because they came from conduction electrons that are at the Fermi energy or below it. If they came from the Fermi energy, then they only have to overcome the work function. These will correspond to the most energetic photoelectrons. However, if they come from below the Fermi energy, then they have to overcome not only the work function, but also the binding energy. So the kinetic energy of these photoelectrons are not as high as the most energetic ones. So their "E_0" is NOT equal to the work function.
This is why when we have students do the photoelectric effect experiments in General Physics courses, we ask them to find the stopping potential, which is the potential that will stop the most energetic photoelectrons from reaching the anode. Only the info given by these most energetic photoelectrons will give you directly the work function.
Certainly, I don't think that this will affect the viewers ability to use the Einstein equation, which was probably the main purpose of the video. But there is an opportunity here to not mislead the viewers and make the video tighter and more accurate. It also might save many of us from having to explain to other people when they tried to go into this deeper (especially students of physics). For a video that is viewed by such a wide audience, this is not the type of inaccuracies that I expect for them to have missed.
In this article, Ethan Siegel valiantly tried to explain, in simple language, what "multiverse" is within the astrophysical/cosmological context:
Inflation doesn't end everywhere at once, but rather in select,
disconnected locations at any given time, while the space between those
locations continues to inflate. There should be multiple, enormous
regions of space where inflation ends and a hot Big Bang begins, but
they can never encounter one another, as they're separated by regions of
inflating space. Wherever inflation begins, it is all but guaranteed to
continue for an eternity, at least in places.
Where inflation ends for us, we get a hot Big Bang. The part of the
Universe we observe is just one part of this region where inflation
ended, with more unobservable Universe beyond that. But there are
countlessly many regions, all disconnected from one another, with the
same exact story.
Unfortunately, as is the problem with String theory, none of these have testable prediction that can push it out of the realm of speculation and into being a true science.
I feel as if these are the golden years for astronomy and astrophysics.
First there was the discovery of gravitational waves. Then a major astronomical event occurred, and we were able to detect it using the "old" standard technique via EM radiation, and via the detection of gravitational waves from it. So now astronomy has two different types of "messengers" to tell us about such events.
Well now, make way for a third messenger, and that is ubiquitous neutrinos. Two papers published in Science last week detected neutrinos (along with the accompanying EM radiation) from a "blazer". The neutrino detection part was made predominantly at IceCube detector located in the Antarctica.
Both papers are available as open access here and here. A summary of this discovery can be found at PhysicsWorld (may require free registration).
Chalk this up to an application of high-energy physics in the medical diagnostic field. The first human has been scanned by a new type of x-ray scanner (registration required to read article at this moment).
The MARS scanner uses Medipix3 technology developed at CERN
to produce multi-energy images with high spatial resolution and low
noise. Medipix is a family of read-out chips originally developed for
the Large Hadron Collider and modified for medical applications.
The Medipix3 detector measures the energy of each X-ray photon as it
is detected. This spectral information is used to produce 3D images that
show the individual constituents of the imaged tissue, providing
significantly improved diagnostic information.
I'll repeat this, maybe to those not in the choir, that many of the esoteric experiments that you think have no relevance to your everyday lives, may turn out to be the ones that might save your lives, or the lives of your loved ones, down the road. So think about this when you talk to your elected political representatives when it comes to funding basic science.
Archibald and colleagues’ study breaks new ground because the
gravitational energy inside a neutron star can account for as much as
20% of the body’s mass.
The authors’ results therefore imply that the accelerations of
gravitational energy and matter differ by no more than a few parts per
105 — a tenfold improvement over the bound from lunar laser ranging.
More
importantly, the authors have provided what is known as a strong-field
test of general relativity. Unlike the Solar System, for which
Einstein’s theory predicts only small deviations from Newton’s theory of
gravity, the motion of a neutron star in a gravitational field invokes
full general relativity in all its complex glory. Einstein’s theory
passes this strong-field test with flying colours.
The more they test it, the more convincing it becomes.
Zz.
[1] A.M. Archibald et al., Nature, 559, p73
(2018).
A new bibliometric study has found that authors can be roughly grouped into three categories: lead scientists who are already prominent in their fields, successors who are early career scientists, and toilers, which are those who do a lot of the dirty work but aren't going anywhere.
When looking at the citation data for mathematicians, psychologists and
physicists, the authors identified three broad clusters that are
“loosely based” on how the citations per year changes over time. Leaders
tend to be experienced scientists who are widely recognized in their
fields, which results in an annual citation increase. The successors
tend to be early-career scientists who have had a surge in their
citations in recent years. Toilers, meanwhile, may have a high citation
count, but this stays mostly constant and may even drop slightly.
Not sure of the significance of this study, but hey, it's another criteria to classify people!
