I wouldn’t normally watch a basketball game, but the public school here texted out a message advising us that school uniforms wouldn’t be required today if students wanted to wear Gators or Cougars outfits instead (I would love to see the kid brave enough to wear a Houston shirt!).
Xfinity managed to stage a TV outage in our neighborhood (first time I’d tried to use cable since the Super Bowl), promising to have service restored by tomorrow evening, but I was able to see the end of the game via streaming.
Florida universities are searching for ways to pump more money into sports ahead of a proposed landmark NCAA settlement that would open the door for schools to directly pay athletes — and using state dollars could be on the table.
Florida has long held a bright line against putting tax dollars into college athletics. But that could change soon, as schools here and across the country grapple with revolutionary changes coming to the NCAA.
Athletic programs at Florida universities are by rule meant to be self-funded, paid for by student fees, ticket sales to events, NCAA distributions, sponsorships and donation dollars, among other sources.
A friend whose child recently applied to NYU downloaded the hacker’s ZIP file of liberated data (canonical link; it may be that this has been getting updated with additional redactions) and found his child’s name and other identifiable characteristics.
A dark web user claimed responsibility for briefly hacking New York University’s website Saturday, and replacing it with what appeared to be student test scores and an apparent racial epithet.
Instead of the usual images of college athletes and the Greenwich Village campus, the site featured a black background with green writing showing a message along with charts of what were purported to be SAT and ACT scores and GPAs for students in 2024, divided by race.
“On June 29 2023, racial affirmative action in college admissions was ruled illegal,” the female hacker’s message reads. “Computer N–gy Exploitation (CNE) reveals NYU continued anyway.”
My friend and his computer-oriented son played around with the data and found an interesting pattern… kids from their local high school were in the database as having applied early with certain SAT scores and GPA. The database showed that they were rejected (perhaps for being white, since their qualifications were above the medians for admitted precious Black applicants). In conversations at school, the kids claimed higher SAT/GPA numbers than they reported to NYU and the kids didn’t mention having applied to NYU (i.e., they kept their rejections secret).
What does it take to be accepted? My friend and his son found a good athlete from a Maskachusetts public high school. His (weighted GPA) was 4.15 and his SAT score was 1550. He’s the wrong kind of Brown (Indian), apparently, and was rejected.
The data download arrives as CSV files, but don’t try opening in Excel. The files are around 3 GB in size:
Whatever the test scores of the carefully-curated-by-skin-color NYU admittees. they can all be on the #RightSideOfHistory (link) with the NYU Queer Union:
There is one thing that students and faculty at Columbia say that they hate more than than the state of Israel: inequality. The flip side is that there is one thing that students and faculty at Columbia love more than the Islamic Resistance Movement (“Hamas”), UNRWA, and Palestinian Islamic Jihad: equality. Columbia has accumulated $15 billion in profits (its endowment) and, therefore, is near the top of the top 1% of the richest colleges in the U.S. (list; there are about 4,000 colleges and universities total in the U.S).
One would think thank these inequality-haters would be delighted that the Trump administration had decided to redirect money from their rich school, thus freeing up funds to be distributed to comparatively poor schools. Yet instead we learn that folks at Columbia are upset. Example video: “Columbia University staff, students aren’t pleased with $400M cut in funds”.
“The AAUP is actively working with our members across the nation in preparation to resist these draconian policies that severely undermine the academic freedom and freedom of speech and expression that are fundamental to higher education,” the statement from [union leader Todd] Wolfson reads.
An elite academic is truly free only if he/she/ze/they is receiving an unconditional paycheck from working class taxpayers? In a now-deleted tweet, a Columbia grad student wrote that her F31 grant was worth only $100,000 per year in salary and tuition and that this was “pennies”, serenely unaware at the time that quite a few taxpayers would consider $100,000/year to be actual money. (the BLS says that median wage in Q4 2024 for a full-time worker was $1,185/week = $61,620/year)
(Same question about Californians. They say that they hate inequality and then they complain that California purportedly pays more in federal taxes than it receives in federal spending. (Much if not most of this is due, I think, to Californians paying into Social Security and Medicare while working in California and then receiving Social Security and Medicare benefits in retirement after moving to other states.) Californians want money extracted from taxpayers in Mississippi for their gold-plated high-speed rail system, for example, when that is completely inconsistent with their philosophy of promoting equality.)
Another question about Columbia… most of the academics I know who get federal money said that they would leave the U.S. in the event of a second Nakba (Trump victory). Nearly all should be living in Canada or Europe by now. Why are there enough of these folks still at Columbia to soak up so much federal money?
Separately, how is the noble enricher Mahmoud Khalil doing?
the Inequality sub-department within Sociology at Columbia (14 taxpayer-funded faculty getting paid far above the median wage in the U.S. so that they can write articles about how it is bad if people get paid far above the median wage)
A friend who taught computer nerdism in Hong Kong before joining our lab at MIT used to try to intensify the pain and suffering of graduate students by remind us that the Chinese had an expression “Poor as a Professor, Dumb as a PhD”.
In an age where an average OpenAI employee earns $1 million/year and a receptionist at an NVIDIA branch office likely gets considerably more, UCLA is hiring mathematics professors for “$78,200 – $101,400 annually.” In case the original URL gets memory-holed, here are some screen shots:
Google’s AI says “The average home price near UCLA in Westwood, Los Angeles is around $1.3–1.6 million, depending on the source. The median sale price per square foot is around $857–$859.” The same AI says that a 30-year mortgage on a small house near UCLA will cost about $90,000 per year (i.e., roughly 100 percent of what UCLA is offering to pay the proud Ph.D. in mathematics.
Let’s dive into some of the specifics to figure out what a successful applicant looks like. In theory, California government employers aren’t supposed to sort applicants by skin color (the hated-by-progressives Proposition 209 from 1996). Let’s look at some of the language:
We strongly encourage applications from individuals from underrepresented racial and ethnic groups, and other individuals who are underrepresented in the field, across color, creed, race, ethnic and national origin, physical ability, gender and sexual identity, or any other legally protected basis.
If they don’t discriminate by skin color in hiring then where’s the “strong encouragement” for those who have a favored skin color?
Donald Trump is trying to eradicate DEI from federally-funded universities such as UCLA. Instead, UCLA will have “EDI”:
Statement of contributions to equity, diversity, and inclusion that includes previous and planned efforts that advance EDI through formal and/or informal mentoring, especially of Latina students
Are they trying to put together a “Hot Latinas” calendar for their nerd departments?
This search is part of a cluster hire with faculty positions in the departments of Chemistry, Mathematics, and Physics and Astronomy who will support UCLA’s goals to achieve federal designation as a Hispanic Serving Institution as early as 2025. … Faculty hired through this search are expected to maintain an active affiliation with the Chicano Studies Research Center and to have a track record or demonstrated commitment to mentoring and encouraging the success of U.S.-based Latinx and first-generation scholars. Since the Latina population is particularly under-represented in physical sciences nationwide, the Department of Mathematics and the Division of Physical Sciences are especially interested in candidates with potential to serve as outstanding mentors to Latina students.
Maybe I could be considered, despite my lack of a math Ph.D., because I consistently use the term “Latinx”:
the Office of the Chancellor and the Executive Vice Chancellor and Provost have sponsored this search in order to recruit exceptional scholars whose teaching, scholarship and/or mentoring has strong ties to Latinx experiences in the United States.
The state shall not discriminate against, or grant preferential treatment to, any individual or group on the basis of race, sex, color, ethnicity, or national origin in the operation of public employment, public education, or public contracting.
Circling back to the economics… as prestigious as some of these institutions are, how is a math professor earning $78,200/year in his/her/zir/their 30s ever going to be able to afford a family unless he/she/ze/they chooses a job at a school in a part of the country with a lower cost of living? It’s tough to have two children in a studio apartment shared with another adult.
Our mole inside Queers-for-Palestine Brown University signed up for Linear Algebra and was sentenced to read “Mathematical Microaggressions” by a past president of the Mathematical Association of America, Francis Edward Su. He/she/ze/they starts off by relating his/her/zir/their own personal trauma:
Here are some example microaggressions in the math world:
Turning tricks is somehow bad:
Math will be improved with more diversity:
Here’s the organization’s current “Executive Director” (“president” wasn’t a sufficiently august title?):
They’re so certain that diversity improves mathematics that they hired one of the world’s whitest white guys to be their leader?
On March 16, 2021 a man killed eight people, including six women of Asian descent, and injured one man in a shooting spree in Atlanta, Georgia. This violence has renewed broader calls to support our Asian and Asian American communities. The specifics of this tragic incident remind us that there are multiple layers of identity-based marginalization and hate related to gender, race, ethnicity, and nationality. One solidarity movement with the victims of the hate crime is #StopAsianHate. This is not a response to last Tuesday’s events, but to a broader arc of increased hate crime since the COVID-19 pandemic started.
In 2019, MAA launched the Inclusivity Award in recognition of the importance of its core value of Inclusivity and building a healthy, vibrant mathematical community where all are welcome and encouraged to flourish. The 2021 award winner is William (Bill) Hawkins, Jr.
UnderDr. Hawkins’s leadership, the SUMMA Office created an archival record of American PhDs in mathematics and mathematics education who are members of minority groups, initiated the Minority Chairs Breakfast annually, established the Tensor-SUMMA projects “to encourage the pursuit and enjoyment of mathematics by students who are members of groups historically underrepresented in the field of mathematics,” organized panels at JMM on issues that affected minority institutions or populations, published a poster on African and African-American Pioneers in Mathematics, and provided guidance to those who wanted to establish an intervention project.
“I am delighted to be able to recognize my friend and colleague, Bill Hawkins, with the 2021 Inclusivity Award,” said MAA Executive Director, Michael Pearson. “It has been my privilege to work with, and learn from, Bill during my tenure at MAA.”
Circling back to Clouseau, let’s hope that he can learn some linear algebra from YouTube while the Brown faculty teaches him about microaggressions (a $91,676/year experience for 2024-5).
President Donald Trump signed an executive order Feb. 14 to withhold federal funding from schools — including public colleges and universities — requiring COVID-19 vaccines for attendance.
The article then provides a partial list of the righteous:
Oberlin College requires that all students, faculty and staff attending or working at Oberlin receive a full COVID-19 vaccine, unless an individual has an approved medical or religious exemption.
The above list may not be complete. Tufts in Maskachusetts isn’t listed, for example, but it does require medical, dental, PA, etc. students to receive the Sacrament of Fauci plus a Booster of Faucism. (They’re still following the Science as revealed by Dr. Fauci, the CDC, and Prof. Dr. Joe Biden, M.D., Ph.D. in which the COVID-19 “vaccine” prevents transmission of SARS-CoV-2?) Does the Trump executive order come with an exemption for medical/dental schools or will Tufts have to choose between saving lives/its sacred principles and the sweet cash that flows out of Washington, D.C.?
After saying that nothing is more precious than human lives and the COVID-19 vaccine is essential, how does a college or university reverse course and explain that it no longer cares about saving lives? Will they defrost Claudine Gay so that she can explain that it is all about the context?
There’s currently a debate about whether mediocre nerds should be imported into the U.S. via H-1B or only supernerds, perhaps via the O-1 visa (both of these are “nonimmigrant” visas and yet everyone who gets one seems to end up as a permanent immigrant to the United States). The main argument supporting a massive annual influx of nerds is that Americans cannot and will not do nerd work, just as Americans cannot and will not do any hard work, which is why we need a border open to low-skill undocumented migrants.
Could the U.S. grow its own nerd supply based on native-born Americans? As it turns out, I have some experience in this area! About 25 years ago, I started “ArsDigita University”, a post-baccalaureate program in which people who had non-nerd degrees could take all of the core undergrad computer science classes in a TA-supervised cooperative open office-style environment. People just had to show up for 9-5 every day for a year and they’d come out knowing pretty much everything that a standard CS bachelor’s degree holder would know. Not a “coding camp”, in other words, but traditional CS knowledge. The big differences compared to a traditional university were (1) take one course at a time, and (2) do all of the work together in one room so that it would be easy to get help from another student or a TA.
Did it work? We ran it for just one year, but as far as I know everyone who completed the program got the kind of job that someone graduating with a CS bachelor’s would get.
As loyal readers may be aware, I’ve long been a critic of the traditional four-year college/university. Simply getting rid of summer and winter breaks would reduce the time required to get a degree and begin a career to 2.5 years. 18-20-year-olds are blessed with tremendous health and energy and shouldn’t need to take nearly half the year off. Here are some examples of my previous criticisms:
“Teaching Software Engineering” (2001), on the magic of project-based learning when the goal is to teach people how to handle engineering projects
If we’re going to cut back on H-1Bs, though, we might need to get a little more radical. Following the lead of the Germans/Swiss, we should try to set things up so that a high-school graduate is ready to begin work in the tech mines as an apprentice nerdlet. We can have some demanding career-oriented classes for smart kids where the goal is not to get into college, but instead to get a job at age 18 and continue to develop skills that are obtained via certificate programs with independently administered exams. These would be like the current Microsoft and Cisco certification programs, but with a much broader array of options, e.g., for having learned physics, math, data science, machine learning, etc. to various levels (Coursera maybe already does this). These certifications could also help older workers who’ve maintained their skills. Instead of showing an employer a 35-year-old transcript as evidence that physics and engineering classes were taken, an applicant could show the employer 6-month-old certifications that physics and engineering are currently understood.
I’m not sure what the argument, from an employer’s point of view, for the traditional 4-year-old college experience is. For the lucky kids who get to attend a top-100 school, it’s obviously great fun to hang out with friends, attend football games, have sex with a lot of different partners, and occasionally study. But how do these experiences make a person a more effective worker? I think the answer is “generally, they don’t”. One of my former neighbors in Maskachusetts spent about $1 million on private school and college for a child who is now working as a receptionist for an HVAC company in a city that is notable for its rich concentration of marijuana and meth stores. Plainly this is something that the girl could have done just as easily on graduation from high school, consistent with the book Academically Adrift:
At the heart of the book is an analysis of data from the Collegiate Learning Assessment (CLA), which requires students to synthesize data from various sources and write up a report with a recommendation. It turns out that attending college is a very inefficient way to improve one’s performance at this kind of task. After three semesters, the average college student’s score improved by 0.18 standard deviation or seven percentile points (e.g., the sophomore if sent back into the freshman pool would have risen from the 50th to the 57th percentile). After four years, the seniors had a 0.5 standard deviation improvement over the freshman, compared to 1 standard deviation in the 1980s.
Readers: Do you think employers could be talked down from H-1B and convinced to hire American 18-year-olds as apprentices who’d spend their evenings taking in-person or online classes in advanced nerdism?
Separately, I’d love to know how COBOL-coding nerds and beautiful fashion models got lumped together:
“The H-1B program applies to employers seeking to hire nonimmigrant aliens as workers in specialty occupations or as fashion models of distinguished merit and ability“
The Yale Alumni Magazine arrived in our mailbox with a cover reminding the Righteous that Yale students were on the Right Side of History (TM) against the “other apartheid regime” (i.e., not Israel) back in the 1980s:
The article, titled “The shanties on the plaza”, never explicitly mentions the noble Palestinians nor the modern apartheid state of Israel, but the parallels are pretty obvious and I think we can all agree on who was in the right back then.
What about the Extremely Unrighteous? From December 2:
The incoming dictator threatened the entirely peaceful hostage-holding Gazans with “Those responsible will be hit harder than anybody has been hit in the long and storied History of the United States of America.” Considering what we did to Tokyo (100,000 civilians killed in one night), Hiroshima and Nagasaki, I’m not sure how this promise could be fulfilled.
Related:
“Nelson Mandela’s support for Palestinians endures with South Africa’s genocide case against Israel” (state-sponsored PBS): “We have stood with the Palestinians and we will continue to stand with our Palestinian brothers and sisters,” Mandela’s grandson, Mandla Mandela, said at a pro-Palestinian rally in Cape Town in October, days after the Hamas attack in southern Israel spurred the war on Gaza. Mandla Mandela, an ANC lawmaker, wore a black and white Palestinian keffiyeh around his neck as he spoke to a large crowd.
Ron DeSantis has set up all of the core functions of government so well here in Florida that it is unclear what he would need to do for the next two years (the hated Yale/Harvard graduate will be forced by term limits to leave office in January 2027). Here’s an idea for a Big Project worthy of a politician with Big Skills: develop a new campus for University of Florida that will enable the school to break out of its #30-ish rut among national universities (tied with University of Texas-Austin; #7 among state-run universities).
Why would this make sense? Florida’s population is growing and younger people have been moving into Florida, partially due to the state’s #1 ranking for education in U.S. News but mostly due to the efforts of lockdown governors in the Northeast, Illinois, and California. Florida has about half as many children as California, but only two world-class universities. The first is University of Florida in Gainesville. The second is Florida State University in Tallahassee (FSU is ranked #54 among national universities by U.S. News). California, on the other hand, has Stanford, CalTech, UC-Berkeley, UC-LA, UC-San Diego, UC-Davis, UC-Irvine, and UC-Santa Barbara (8 total ranked #54 and above). There would definitely be demand for another excellent school and Florida has the tax base to make it happen.
Why not expand and improve the schools in Gainesville and Tallahassee? They’re already huge, for one thing (60,000 and 45,000 students). More importantly, if the goal is to build a university that can rank within the top 10, they’re not in the right places. The typical elite academic doesn’t want to live in a small Southern city. Gainesville is unsuccessful at getting UF graduates to stick around and start companies (see Relocation to Florida for a family with school-age children); how is Gainesville going to woo a top researcher away from a school in New York City, Boston, or Chicago?
What are some criteria for where to locate a new university?
Politics. Academics can’t tolerate anyone questioning their beliefs, so they need to live in a city that is dominated by Democrats and where they’re unlikely to ever have a conversation with a Republican. This rules out Miami now that the Latinx have defected to Trump.
Hurricane Risk. Being an elite academic goes hand-in-hand with being a Climate Doomer. This rules out Tampa, whose luck eventually must run out (the city hasn’t been hit by a hurricane since 1926)
Airline Connections. Although elite academics are Climate Doomers, each one has the carbon footprint of a 4 million ton/year cement plant. They need to be able to jump on a flight every few weeks to a conference on the other side of the country or the ocean. You might think that this would bring Miami back into the ring, but nonstops from MIA mostly go to Latin America. Following the lead of Barbra Streisand, the escape route for an American who claims to love Brown people is always to Canada and never Mexico or, God forbid, farther south. Orlando, on the other hand, enjoys nonstop connections to cities around North America and Europe. Everyone eventually needs to come to Walt Disney World and Universal.
High-speed Rail. Intercity rail is catnip for elite progressives. This favors cities spread out along Brightline, which means Orlando, West Palm Beach, Fort Lauderdale, and Miami.
Reviewing the above criteria, Orlando is the obvious choice. It’s one of the few parts of Florida that voted correctly during the Election Nakba of 2024. It’s far enough inland that hurricanes generally lose their strength by the time they arrive over Space Mountain. Orlando is 100′ above sea level, which will reassure even the most ardent Climate Doomer that a vengeful Mother Earth won’t soon reclaim the city as part of the ocean floor. Orlando has great airline connections that will only get better as the theme parks expand. Orlando is going to be ever more connected via high-speed rail as Brightline expands (Tampa is the next big goal).
For recruiting faculty, the state could do a bulk purchase of annual passes (weekday only should be fine since academics don’t need to work M-F 9-5) to Disney, Universal, and Sea World. Everyone who works at UF-Orlando gets passes to all three major parks.
Is this doable? In 2016, the USTA announced the near-completion of a campus with 100 tennis courts on 63 acres next to the big Orlando airport (the plan was conceived in 2014). Celebration, built in the 1990s, is about 5,000 acres and cost about $2.5 billion in pre-Biden dollars to create (home to about 11,000 people, which means enough square footage for a sizable university). The Harvard main campus, which includes a lot of athletic fields, is only about 200 acres. Current Florida state budget surpluses are about $2 billion/year (Ron DeSantis has been using these to pay off debt, but nobody remembers a politician for fiscal prudence; it is acts of fiscal extravagance for which politicians are remembered and celebrated).
One knock against Orlando is that the summer weather is pretty miserable, with an average high of 91-92 in June, July, and August (not hot enough to keep the crowds away from the theme parks!). But that’s actually cooler than Tallahassee and no different than Gainesville and, of course, the academic elite doesn’t have to be on campus during the summer.
Here’s a map showing the new USTA campus in relation to MCO, Walt Disney World (lower left), and Celebration (lower left):
“Palm Beach unanimously approves land deal for Vanderbilt’s new business and tech campus” (vanderbilt.edu, October 28, 2024): In a unanimous vote on Oct. 22, the Palm Beach County Commission approved a deal to provide five acres of county-owned land to Vanderbilt for the development of a new campus in West Palm Beach. For several months, Vanderbilt has been in discussions with city and county officials and community and business leaders about establishing a presence in West Palm Beach to complement the region’s booming financial and tech sectors. The affirmative vote by the county, along with two acres already pledged by the City of West Palm Beach, paves the way for the university to establish a new campus in South Florida focused on graduate programs in business, computing and engineering, bringing high-impact graduate education to what has become known as “Wall Street South.” … Once operational, the West Palm Beach campus will welcome nearly 1,000 students in various business programs … Since 2020, more than $1 trillion in assets under management has relocated to Florida
University of Central Florida, a stepsister to FSU, has 70,000 students in and around Orlando and a dismal #121 ranking from U.S. News
Joel Fajans was the first friend that I made on arrival at MIT (1979) and, sadly, he died last month. He was a gentle soul who never got annoyed by the comparative stupidity of people who didn’t understand physics as well as he did. Although he was generally busy supervising graduate students at UC Berkeley and running experiments at CERN (see “Nothing’s the Matter With Antimatter, New Experiment Confirms” (NYT 2023)) he always had time to answer my questions. I will miss him. If he were alive today I would be asking him “How many rockets can Elon Musk send to Mars before the Earth’s orbit is changed?” Here’s an excerpt from his research page at Berkeley:
And here’s Joel at the intersection of Hollywood and physics:
One of my favorite memories of Joel is when a group of us went on a bike ride from his house in an upscale neighborhood of Berkeley (he saved some money as a young single academic and then married into a bit of inherited wealth). Accustomed to being able to bike in any direction over any terrain on a mountain bike, I managed to ride the borrowed hybrid over of those one-way parking lot tire destroyers and punctured both inner tubes. Joel had a spare tube for one and patched the other and we resumed the group cycle. Joel never complained about or harped on my incompetence.
About half of my class at Comair failed a stage check and received additional sim training, but I got only the bare minimum. My checkride was not too stressful either. The oral exam, which can last 2-3 hours and can include any item of minute knowledge involving regulations, the aircraft’s systems, or almost anything else aviation-related, must by regulation precede the actual flying and it tends to set the tone. The examiner to whom I was assigned was accustomed to humiliating applicants with an opening oral question that none had ever been able to answer satisfactorily. After they realized how ignorant and worthless they were he beat them down for an additional three hours before getting into the sim with the demoralized young pilot.
What was the question? “Why does the Canadair Regional Jet have both an alternating current (AC) electrical system and a direct current (DC) system as well?” As it happened, I had wondered the same thing myself just a couple of weeks earlier. I’d carefully studied the electrical diagrams for the airplane and had a one-hour phone discussion with a friend who is a physics professor at UC Berkeley. Without giving the guy any hint as to my non-aviation background or the fact that I’d discussed this with a physicist, I went up to the whiteboard and gave a 5-minute talk about how Maxwell’s equations explained that a time-varying magnetic field, like you would get from using engine power to rotate permanent magnets, generates a time-varying electric field, i.e., alternating voltage potential. This AC power is ideal for driving the heaviest load on the airplane, the hydraulic pumps for the flight controls (a spinning motor having more or less the same structure as a generator). Having AC power at a high voltage also makes it easy to have lighter wires to move the power around the airplane and then transform down to lower voltage for radios, etc. A transformer will pass AC voltage but not DC.
He said “Your oral is complete. We’re getting into the sim now.”
Searching through my Gmail, I found a good 2007 answer to one of my helicopter student’s questions:
(Student) from Principles of Helicopter Flight, p. 4: “Equilibrium means a state of zero-acceleration. When an object travels in a straight line at a constant speed, its velocity is constant (since there is no change in either speed or direction). It can then be said that the object is in equilibrium. If an object travels at a steady 50 mph on a curve, however, it must be accelerating because its direction is constantly changing and it can then not be in equilibrium.
(Joel) The solar system is in a pretty good equilibrium. (Alright, you can prove that it isn’t but its lasted a long time. A system consisting of just the sun and the earth would be in equilibrium.) The earth is traveling in a circle. So the quote from “Principles…” is incorrect.
A centrifugal force is a fictitious force, but as any fighter pilot would tell you, it feels pretty real.
You are correct that some force must be applied to force a plane into a circle.
However, if you want to pretend that the reference frame rotating with the plane is “normal”, than, in that frame, the forces are balanced…the centrifugal force is balanced by a force from the wings pointing towards the center of rotation.
The question is not profound…just semantics.
Modern thinking on how to teach physics (teaching that I don’t subscribe to) bans mentioning fictitious forces. The claim is that it just confuses the students.
A 2008 discussion about “why treadmill incline makes walking harder”, in which I quote Joel:
I asked Joel Fajans, physics nerd, and he said “consider what happens if you stop walking; you go backwards but also down”. Joel says that if you want to get fancy, you can go for a special relativity-style argument about frames of reference.
Anyway, the incline does in fact make you work harder than simply lifting your legs from a lower position to a higher one. The fact that your body isn’t going up doesn’t mean you aren’t working because the treadmill is creating a new reference frame.
In response to a 2008 question about why airplane generators are rated in KVA (kilo-volt-amperes) rather than in watts:
watts are true power, while kVA are apparent power. The difference has to do with the phase relationship between the voltage and current. With a resistive loads (light bulbs) the voltage and current are in perfectly in phase. Then kVA=kW. But with a pure inductive load (or pure capacitive load) the voltage and current are 90deg out of phase. Inductors (capacitors) do not dissipate average power; there maybe substantial voltages across them and currents, but there is no net power. So the load in watts is zero. The kVA load is not zero…it is the product of the RMS voltage times the RMS current. So what is this extra “load”? It is power sloshing back and forth between the load and the generator…first the generator stores energy in the load, and then the load puts the energy back into the generator.
Loads in the real world tend to be somewhere between perfectly resistive and perfectly inductive, with phase angles in the range of 10-30%.
The amount of coal you have to burn is proportional to the watts, not the KVA (assuming perfect conductors carrying the power to the load.) But in practice, a generator may fry even with a perfect inductor because the instantaneous demanded currents can be quite high. SO on an airplane you would protect for kVA, not kW.
A 2008 exchange:
(me) Can you make [a jet-powered airplane] generator of equivalent power with fewer windings and lighter weight at 400 Hz. compared to 60 Hz? If you want to run the whole airplane on AC power, forgetting about any rectification to DC, does it make sense to use 400 Hz? I figured the 60 Hz. or 400 Hz. would relate more to the speed with which the rotor was spinning and not the number of windings. In that case there is a gearing issue where it would be a lot cheaper to gear the 30,000 rpm power turbine down to 400 Hz. instead of 60 Hz.
(Joel) Running at higher frequencies makes transformers much smaller. For example, I have a 200A power, 10kW power supply that runs at 60Hz and weighs about 300lbs. I have another power supply, which runs at about 30kHz, which supplies 1000A at 6kW which weighs only about 30lbs.
Most power supplies these days are “switchers”. Rather than working at 60Hz to convert AC to high quality DC, they first convert that AC to very low quality DC (glitchy, not well regulated) and convert the low quality DC to 20-60kHz. Then they take the 20-60kHz and convert it back into high quality DC. This takes a lot of extra circuitry, but is definitely worth in terms of weight and cost. All computer power supplies are switchers, for instance. The only down side is that they tend to have noise at the fundamental and harmonics of the switching frequency, which can be problematic, particularly in the sorts of physics stuff I do. (We are fighting such noise at the moment.)
Anyway, the only thing I’d quarrel with is the claim on the web site that there are extra losses at 400Hz. This isn’t quite as simple as described on the web site. Inductive “losses” aren’t really losses…to first order no power is dissipated, so no extra fuel has to be consumed. It simply means that there are voltage drops on the lines. And I can’t believe that its very large.
One issue not mentioned on the web site, which represents a real power loss, is skin depth. See http://en.wikipedia.org/wiki/Skin_depth It turns out that AC current only flows on the outer “skin” of a wire. The skin depth is the thickness of the layer in which current flows. At 60Hz in copper, this depth is about 1cm, but at 400Hz it decreases by the square root of the frequency to about 0.4cm. But this effect doesn’t matter unless the cables are of thickness comparable to the skin depth. I can’t imagine that there are any cables of radius ~0.4cm on an airplane (maybe on an AWACS plane). It is a real problem, however, on long distance transmission power lines.
Joel held strictly orthodox progressive Democrat Cambridge-/Berkeley-style political beliefs. He attributed America’s woes to the existence of stupid/uneducated people in the South, none of whom he had ever met in person. He recognized that California failed to deliver what local and state Democrats promised and assigned 100 percent of the blame for this failure to Republicans because of their role in promoting Proposition 13 and its limits on property tax. (Joel himself was a huge beneficiary of Prop 13 because he and his wife purchased a house in 1999 and, therefore, paid tax on a slightly adjusted original purchase price.) I would point out (a) that California collected a relative high percentage of residents’ income (Tax Foundation) and, (b) California Democrats were in 100% control of the state and could revoke Prop 13, impose a wealth tax, raise income and sales tax rates, charge a congestion fee for use of the roads, etc. This wouldn’t convince him to hate Republicans less. One of Joel’s core yearnings was for higher tax rates and I couldn’t persuade him that the government’s greed was infinite and that, therefore, tax rates were likely already set at a revenue-maximizing level (i.e., to get more tax revenue, the government would have to introduce new taxes, such as value-added tax, not tweak rates; see these charts of revenue vs. rates). Our final political conversation was in March 2024 and regarded the battles in Gaza (I was with him last month, but he was too weak to talk). Joel, an American secular Jew, said “a pox on both their houses”, agreeing with another Jewish Berkeley resident that Hamas and Israel were equally bad. (While this sounds like a nuanced and balanced position, it is highly favorable to the Palestinians. The same people who say that Hamas and Israel are comparable also deny that Hamas was elected to power by Palestinians. Hamas either seized power or is somehow accidentally in charge of Gaza. Once Hamas is gone, Palestinians will revert to
