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Lectures on the history of physics

Galileo and Einstein: Lectures on the history of physics

Michael Fowler – University of Virginia Physics




Claims Evidence Reasoning

Claims Evidence Reasoning, also presented as Model-Evidence Link Diagrams Project


from Dr. Doug Lombardi, Dr. Janelle Bailey, Missy Holzer et al

Climate Change MEL

The Climate Change MEL asks students to weigh the connections between evidence and alternative explanations about the causes of current climate change.

Below are links to a series of activities that will help students use the Climate Change MEL and learn more about fundamental scientific principles related to climate and weather.

Fracking MEL

The Fracking MEL asks students to weigh the connections between evidence and alternative explanations about the impact of hydraulic fracturing (fracking) on moderate-strength earthquakes.

Below are links to a series of activities that will help students use the Fracking MEL and learn more about fundamental scientific principles related to earthquakes.

Moon MEL

The Moon MEL asks students to weigh the connections between evidence and alternative explanations about the formation of the Moon.

Below are links to a series of activities that will help students use the Moon MEL and learn more about fundamental scientific principles related to the Moon and its formation.

Wetlands MEL

The Wetlands MEL asks students to weigh the connections between evidence and alternative explanations about wetlands as a natural resources.

Below are links to a series of activities that will help students use the Wetlands MEL and learn more about fundamental scientific principles related to the role of wetlands.

Supplements to the MEL

The Explanation Task is part of each MEL Activity. In this task, students provide written explanations for the arrows they drew on the diagram. The following rubric may be used to score students’ written explanations.

This Plausibility Ranking Task (PRT), which may be completed prior to using any MELs, helps students to understand the role of evidence in supporting or refuting models.

The Critical Evaluation Task (CET) asks students to consider the flaws in arguments presented in favor of and in opposition to recycling. It may be completed done prior to and after use of any and all MELs in order to assess students’ ability to be critically evaluative.

from Model-Evidence Link Diagrams Project


Claim Evidence Reasoning

If we assume global warming is a hoax, what should we expect to see

This analysis is by Phil Plait, Mar 9, 2017

Global warming GIF

I will ask you to indulge me for a moment in a thought experiment. It’s not hard, and it leads to a startlingly simple yet powerful conclusion, one I think you may find both important and terribly useful.

Still, it starts with a big ask, so forgive me. And that is: Let’s make an assumption, one you’ve heard many times before. Let’s say that global warming is a hoax.

I know, I know. But go with this, here. So, yes, let’s say that climate change deniers —people like House Science, Space, and Technology Committee chairman Lamar Smith, Senator James Inhofe, and even Donald Trump himself— are right. Whatever the reasons (Chinese hoax, climatologist cabal clamoring colossal cash, carbon dioxide isn’t a powerful greenhouse gas, or just a liberal conspiracy), let’s say that the Earth is not warming up.

In that case, the temperatures we see today on average should be much like the ones we saw, say, 20 years ago. Or 50. Sure, you’d see fluctuations. In a given spot on a given day the temperature in 1968 might have been a degree warmer than it was in 1974, or three degrees cooler than in 2010. But what you’d expect is that over time, a graph showing the temperature would be pretty much flat, with lots of short-term spikes up and down.

Now, statistically speaking, you expect some records to be broken every now and again. Over time, every few years for a given day you’d get a record high, and every few years a record low. The details will change from place to place and time to time, but again, if the average temperature trend is flat, unchanging, then you would expect to see just as many record cold days as record warm days. There might be small deviations, like, say, a handful of more cool than warm days, but the difference would be very small depending on how many days you look at.

It’s like flipping a coin. On average, you should get a 50/50 split between heads and tails. But if you flip it 10 times, say, you wouldn’t be shocked to see seven heads and three tails. But if you flip it a thousand times, you’d really expect to see a very even split. Seeing 700 heads and 300 tails would be truly extraordinary.

So, if we remind ourselves of our basic assumption —global warming isn’t real— then we expect there to be as many record high days as there are record lows. Simple statistics.

So, what do we see?

Guy Walton, a meteorologist in Georgia, took a look at the data from the NOAA’s National Centers for Environmental Information. Whenever a weather station in the US breaks a record, high or low, it’s catalogued (Walton has more info on this at the link above). He found something astonishing: For February 2017, the number of record highs across the US recorded was 6,201.

The number of record lows? 128.

That’s a ratio of over 48:1. In just one month.

Again, if temperatures were flat over time, and record highs and lows were random fluctuations, you’d expect a ratio much closer to 1:1. In other words, out of 6329 records set in total, you’d expect there to be about 3165 record highs, and 3165 record lows.

For fans of statistics, with a total of 6329 records broken, one standard deviation is the square root of that, or about 80. So, sure, something like 3265 highs and 3064 lows wouldn’t be too unusual. If you start to see more of an imbalance than that, it would be weird.

Seeing 6201 record highs to 128 lows is very, very, very weird. Like, zero chance of that happening by accident.

Now, Phil, I can hear you thinking, that’s just for the US (2% of the planet) over one month. And you’ve told us before that weather isn’t climate; weather is what you expect now, climate is what you expect over long periods of time. So, maybe this is a fluke?

Walton notes that, if you look at records in the US going back to the 1920s, the six highest ratios of record highs to lows all occur since the 1990s. Huh.

And making this more global, a pair of Australian scientists looked at their country’s data, and found that their ratios were about even…until the 1960s. After that, highs always outnumber lows. From 2000-2014, record highs outnumbered lows there by 12:1.

The University Corporation for Atmospheric Research collated data from 1800 stations across the US and binned the data by decade — by decade, which is a huge sample; any deviation from a 1:1 ratio would be extraordinary over that timescale.

They found this:

Record Highs and Lows Global warming

This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole. (©UCAR, graphic by Mike Shibao.)


Source of the above image: RECORD HIGH TEMPERATURES FAR OUTPACE RECORD LOWS ACROSS U.S. The National Center for Atmospheric Research/UCAR, Nov 12, 2009

We are seeing far more record high temperatures than record lows in the US… and in other countries, too. Credit: UCAR

Huh. Not only are there more record highs than lows, the ratio between the two is getting higher with time.

So, looking back at our initial assumption — the Earth isn’t warming, and temperatures are flat— there’s a conclusion these data are screaming at us: That assumption is completely and utterly wrong.

And of course, all the evidence backs this up. All of it. Earth’s temperature is increasing. That’s because of the 40 billion tons of extra carbon dioxide humans put into the atmosphere every year (the amount we will see this year, expected to top 410 parts per million, has never been seen before in history as long as humans have walked the Earth). This CO2 allows sunlight to warm the Earth, but prevents all of it from escaping so that a little bit of extra heat remains behind, and that’s warming our planet.

Over time, we’re getting hotter. 2014 was a record hot year, beaten by 2015, itself beaten by 2016. In fact, 15 of the 16 hottest years ever recorded have been from 2001 – 2016. That’s exactly what you’d expect if we were getting warmer, and that means our initial assumption of hoaxery was dead wrong.

The science on this is so basic, the evidence of this so overwhelming, that “not a single national science academy disputes or denies the scientific consensus around human-caused climate change”, and also the overwhelming majority of scientists who study climate do, too.

Maybe you should listen to them, and not politicians who seem ideologically opposed to the science.

Or, you could flip a coin. But if it comes up science dozens of times more often than anti-science, well —and forgive me if I sound like a broken record— the conclusion is obvious.


Fair use: This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.

§107. Limitations on Exclusive Rights: Fair Use

Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)

The growing acceptance of autism in the workplace

from CBS News, Feb 11, 2018

We like to think that good work is always rewarded. But what if some people who could do good work can’t their foot in the door in the first place? That’s where recent hiring initiatives that look beyond unfair stereotypes come in, as Lee Cowan reports in our Cover Story:

Twenty-seven-year-old Christopher Pauley thought he had it all figured out when it came to looking for a job.

He had a detailed spreadsheet of each and every position he applied for — at least 600.

But despite his degree in computer science from California Polytechnic State University, he went two years with barely a nibble.

Did he get discouraged? “Oh my gosh, my morale really started to drop towards the end,” he said. “In fact, there were days where I would either hardly fill out any applications at all, or just simply not apply on anything.”

He knew he had the smarts for most jobs; he was a former Spelling Bee Champ, after all. But Pauley struggles with social and communications skills because he’s also autistic.

While precise numbers are hard to come by, by some estimates at least 80% of adults with autism are unemployed, even though their IQs are often well above average.

Sometimes their job skills can present themselves in unique ways. For Christopher, it’s video games. His ability to recognize patterns and his acute attention to detail — both hallmarks of autism — make his playing the video game Rock Band look pretty easy. And they are the same skills he was hoping would impress prospective employers in the computer programming world. But he always had to get past that interview, which was a challenge at best.

Cowan asked, “Was there, in any of those interviews, a time where you just wanted to tell somebody, ‘Look, I know my social skills maybe aren’t quite what you expect, but I know I can do this job, and I know I can do a really good job if you give me a chance’?”


“But you never said that to anybody?”

“Most of the time, no,” he replied.

“Because why?”

“I just wasn’t comfortable. It makes me come across as desperate.”

At Microsoft, however, there was no need to hide his autism; they were looking for it.

“It’s a talent pool that really hasn’t been tapped,” said Jenny Lay-Flurrie, the chief accessibility officer at tech giant Microsoft outside Seattle. “There really is, and was, a lot of data on the table that said to us that we were missing out. We were missing out on an opportunity to bring talent in with autism.”

Cowan said, “So in a way, it sounds like this was almost a business imperative.”

“Heck, yeah!” she laughed. “People with disabilities are a strength and a force of nature in this company, myself included.”

Lay-Flurrie, who is profoundly deaf, communicates by reading lips and working with an interpreter. She helped create a hiring program for Microsoft back in 2015 designed to better identify candidates with autistic talents.

Instead of the traditional job interview focusing so heavily on social skills, the company has replaced it with a vetting process that lasts for weeks, and team building exercises like one called the Marshmallow Challenge.

“Being able to watch a candidate in that environment as opposed to sitting across the table interviewing them makes all the difference in the world,” said Cowan.

“Every difference,” said Lay-Flurrie. “Every day, in any company, in any role, you’re going to be asked to work with someone else to figure out a problem or a challenge, or a project.”

“And yet in that scenario, they’re not as self-conscious that they’re being observed for a job — they’re just doing a task.”

“It’s marshmallows!”

After Christopher Pauley went through a similar, unconventional interview process back in 2016, Microsoft quickly hired him as a software engineer. His manager Brent Truell says he was immediately impressed by Christopher’s “out of the box” thinking.

“When we are faced with really complicated problems, the solutions to those aren’t always simple,” said Truell. “And Christopher always kind of brings new insights. And having that creative mind, he always brings something new to the team, which is really exciting.”

“Which is exactly why you hired him, right?


It’s an idea that’s catching on.

Last April, 50 big-name companies — including JP Morgan, Ford and Ernst & Young — came together for a summit on how to bring more autistic adults into the workforce.

It was hosted at the Silicon Valley campus of German software maker SAP, which was one of the first large companies to reach out to the autistic community.

It started its Autism at Work Program almost five years ago, and since then it’s hired 128 people on the spectrum, with the goal of hiring more than 600.

“I have been in this industry for close to 30 years, and I can tell you it’s probably the single most rewarding program that I have been involved with,” said Jose Velasco, who heads the program.

The biggest surprise for him, he says, has been the variety of candidates applying. “Very quickly we started getting resumes from people that had degrees in history, and literature in graphic design, attorneys … the whole gamut of jobs,” Velasco said.

“So really, you went into this thinking that people with autism would be good at certain jobs, and what you ended up discovering is they’re good at all jobs?” asked Cowan.

“They are good at just about every role.”

And they’re expected to perform in those roles, just like anyone else.

Mike Seborowski, for example, was hired three years ago and works in cybersecurity in SAP’s office outside of Philadelphia. When Cowan was visiting, Jose was helping Mike get ready for a long stint at the company world headquarters in Germany.  “If you would had told me six years ago that we would have an employee who was openly autistic in the company, going on a business trip to Germany for a month, I would have not believed you,” said Velasco.

Almost everyone has been a surprise, he says. He points to 26-year-old Gloria Mendoza.

She told Cowan, “You should see some of the videos I had when I was a child. I was not very socially skilled with the other kids. Not showing interest with other people, displaying some of the challenging behaviors that a child on the autism spectrum would have.”

Her parents, Rosaura and Enrique Mendoza, helped get Gloria years of speech and occupational therapies, as well as access to top doctors. “When she was very young, I used to worry so much because I never thought she will overcome all what she has done,” said Rosaura. “So, it was like a very dark cloud.”

Gloria made huge strides in her childhood, but her parents were still concerned about how autism might affect her future.

“We worry about her adult life — well, first of all, could she make it through high school?” said Enrique. “Then, once she does that, you know, can she make it through college? Can she be independent?”

She made it through both high school and college; in fact, she got two degrees from Gettysburg College in Pennsylvania — one in music (she has a beautiful singing voice), and another in computer science. And yet, a year after graduating — and hundreds of resumes later — she still couldn’t find a job … until she applied to SAP.

“Probably the best part about working here is that I can use the skills which I have studied whilst being among people that understand who I am and how I’m different from everybody else,” she said.

SAP put Mendoza through five weeks of training, which included working on her social skills.

She’s now in something called Digital Business Services, where she deals directly with customers.

Cowan asked, “What’s the one dream you really want to come true?”

“Probably that I can be really up there in my department, earning a lot of money, and still keeping the friends that I have,” she replied.

Her new friends are mostly co-workers in the autism program, and they try to get together regularly. Cowan watched as Mendoza and her friends participated in Game Night.

“And that, CBS, is how you play Smash Brothers!” said Gloria.

She told Cowan, “I never really had that many friends when I was younger, and having this wide variety of friends that understands me really makes all the difference for me.”

How so? “‘Cause I can express myself in ways that people won’t look at me weird. And it turns out that a lot of people have common interests as I do.”

SAP boasts a retention rate of about 90% for their autistic employees. Part of that may be due to the fact they’re not just set adrift in the workplace all alone. Each participant in the program is assigned a mentor from within the company — like an on-site guardian angel.

Gabby Robertson-Cawley, who has a cousin on the spectrum, volunteered to work with Gloria. “I think it’s just the rewards of getting to be friends with these colleagues who have autism — it’s not something you get in your typical corporate day-to-day experience,” Robertson-Cawley said.

Microsoft also has mentors. Melanie Carmosino, who works with Christopher Pauley, has a personal connection as well; she has a son who’s autistic.

Cowan asked, “What have you taken away from this whole experience, personally?”

“Hope,” Carmosino replied. “I think that this program gives hope to the autism community. It gives hope to parents like me, and it gives hope to people like my son that a company can, and will, look past their differences and see their gifts and let them contribute to society just like everybody else.”

Christopher Pauley is now independent, living on his own in a high-rise apartment, something he’s always wanted.

Cowan said, “I don’t want to ask how much you’re making, but you’re doing pretty good, it sounds like, yeah?”

“Yes,” he said.

“Could you ever imagine you’d be making this much money?”

“No, I never did! Honestly I would have been perfectly happy with, like, half the money I’m making now.”

He bought a car and drives himself to work — and for the first time, he says, looks forward to arriving at a place where he’s accepted for who he is.

He knows there are still challenges ahead, but given a chance to prove his worth, says Christopher, has given him an optimism he never had.

Cowan asked, “If other kids, or young adults, or adults with autism are watching this, what’s your message to them?”

“Don’t give up, and make sure to always aim high,” he replied. “Don’t aim in the middle You know, shoot for the stars every time, ’cause you never know what might happen.”



Physics of Batman: The Dark Knight

Batman Angular

Let’s assume that the memory fiber used in “The Dark Knight” is real, and that it can be used to change the shape of a cape into gliding wings with the application of an electrical current.  (No such material yet exists, but materials scientists may be getting close.)

Why don’t people use some form of bat wings? Let’s analyze the forces your arms would have to exert in order to successfully use bat wings.


Adapted from “The Physics of Batman: The Dark Knight – High Dive”, Adam Weiner, 08.15.2008

Batman spreads his wings & moves into a circular path.
His motion goes from vertical to horizontal.
The force of air resistance increases dramatically when he opens his wings.
This force turns his linear path into a circular path.
This inward pointing force is a centripetal force.

Law of physics: No object travels in a circular path (Newton’s 1st law), unless some force continually pulls it radially inward.

The balance of inertia and a radially inward force can create circular motion.

Centripetal force depends on the radius of the curve (r) and the radial velocity (v)

F = mv2/r

When a glider – or a Batwing – is bent into the wind, one can use the force to deflect the glider, plane or Batman.

Red arrow to upper right = “lift” (due to the wind hitting the wings)

Red arrow down = weight

Horizontal green arrow is the horizontal component of lift (aka centripetal force)

Vertical green arrow is the vertical component of lift. (If itis big enough, then one can glide for long periods of time)

What about Newton’s 3rd law of motion?

To hold his arms out, Batman has to exert the same force back on the air. So while he moves in a circle, we can calculate the force that will be exerted on Batman’s arms.

circle radius = 20 meters

man + equipment mass = 80 kg

speed remains constant during this turn

Let’s estimate the force on Batman’s arms as he sweeps through the bottom of the arc.

F = weight + centripetal force

F = m g + m v2/r = m ( g + v2/r )

= 80 kg (9.8 m/s2 + [40 m/s]2 /20 m) = 7200 N

= about 1600 pounds

This means that Batman has to hold 800 pounds on each arm!  Imagine lying on your back, on a workout bench, holding your arms out and having 800 pounds of weights placed on each one!  This is probably impossible for someone to do without super-strength.

Perhaps there is a way out of this. Maybe there are some hinges that connect the wings to the Bat suit. If so, then these hinges could be doing some of the supporting, rather than Batman’s arms.

Cartoon Laws of Physics

Cartoon Law I

Any body suspended in space will remain in space until made aware of its situation.

Daffy Duck steps off a cliff, expecting further pastureland. He loiters in midair, soliloquizing flippantly, until he chances to look down. At this point, the familiar principle of 32 feet per second per second takes over.

Cartoon Law II

Any body in motion will tend to remain in motion until solid matter intervenes suddenly.

Whether shot from a cannon or in hot pursuit on foot, cartoon characters are so absolute in their momentum that only a telephone pole or an outsize boulder retards their forward motion absolutely. Sir Isaac Newton called this sudden termination of motion the stooge’s surcease.

Cartoon Law III

Any body passing through solid matter will leave a perforation conforming to its perimeter.

Also called the silhouette of passage, this phenomenon is the speciality of victims of directed-pressure explosions and of reckless cowards who are so eager to escape that they exit directly through the wall of a house, leaving a cookie-cutout-perfect hole. The threat of skunks or matrimony often catalyzes this reaction.

Cartoon Law IV

The time required for an object to fall twenty stories is greater than or equal to the time it takes for whoever knocked it off the ledge to spiral down twenty flights to attempt to capture it unbroken.

Such an object is inevitably priceless, the attempt to capture it inevitably unsuccessful.

Cartoon Law V

All principles of gravity are negated by fear.

Psychic forces are sufficient in most bodies for a shock to propel them directly away from the earth’s surface. A spooky noise or an adversary’s signature sound will induce motion upward, usually to the cradle of a chandelier, a treetop, or the crest of a flagpole. The feet of a character who is running or the wheels of a speeding auto need never touch the ground, especially when in flight.

Cartoon Law VI

As speed increases, objects can be in several places at once.

This is particularly true of tooth-and-claw fights, in which a character’s head may be glimpsed emerging from the cloud of altercation at several places simultaneously. This effect is common as well among bodies that are spinning or being throttled. A ‘wacky’ character has the option of self- replication only at manic high speeds and may ricochet off walls to achieve the velocity required.

Cartoon Law VII

Certain bodies can pass through solid walls painted to resemble tunnel entrances; others cannot.

This trompe l’oeil inconsistency has baffled generations, but at least it is known that whoever paints an entrance on a wall’s surface to trick an opponent will be unable to pursue him into this theoretical space. The painter is flattened against the wall when he attempts to follow into the painting. This is ultimately a problem of art, not of science.

Cartoon Law VIII

Any violent rearrangement of feline matter is impermanent.

Cartoon cats possess even more deaths than the traditional nine lives might comfortably afford. They can be decimated, spliced, splayed, accordion-pleated, spindled, or disassembled, but they cannot be destroyed. After a few moments of blinking self pity, they reinflate, elongate, snap back, or solidify.

Corollary: A cat will assume the shape of its container.

Cartoon Law IX

Everything falls faster than an anvil.

Cartoon Law X

For every vengea nce there is an equal and opposite revengeance.

This is the one law of animated cartoon motion that also applies to the physical world at large. For that reason, we need the relief of watching it happen to a duck instead.

Cartoon Law Amendment A

A sharp object will always propel a character upward.

When poked (usually in the buttocks) with a sharp object (usually a pin), a character will defy gravity by shooting straight up, with great velocity.

Cartoon Law Amendment B

The laws of object permanence are nullified for “cool” characters.

Characters who are intended to be “cool” can make previously nonexistent objects appear from behind their backs at will. For instance, the Road Runner can materialize signs to express himself without speaking.

Cartoon Law Amendment C

Explosive weapons cannot cause fatal injuries.

They merely turn characters temporarily black and smoky.

Cartoon Law Amendment D

Gravity is transmitted by slow-moving waves of large wavelengths.

Their operation can be wittnessed by observing the behavior of a canine suspended over a large vertical drop. Its feet will begin to fall first, causing its legs to stretch. As the wave reaches its torso, that part will begin to fall, causing the neck to stretch. As the head begins to fall, tension is released and the canine will resume its regular proportions until such time as it strikes the ground.

Cartoon Law Amendment E

Dynamite is spontaneously generated in “C-spaces” (spaces in which cartoon laws hold).

The process is analogous to steady-state theories of the universe which postulated that the tensions involved in maintaining a space would cause the creation of hydrogen from nothing. Dynamite quanta are quite large (stick sized) and unstable (lit). Such quanta are attracted to psychic forces generated by feelings of distress in “cool” characters (see Amendment B, which may be a special case of this law), who are able to use said quanta to their advantage. One may imagine C-spaces where all matter and energy result from primal masses of dynamite exploding. A big bang indeed.

© 1997 William Geoffrey Shotts. Last update: Thursday, December 4, 1997

Hovercraft build project

Hovercraft project:Choose 2 of the 3 options

I. Build and demonstrate a hovercraft, or

II. Write a typed report, with a cover page, 3 double-spaced pages of text, and 1 page of citations/references, on what a hovercraft is, how they work, and how they use Newton’s laws of motion, or

III. Create a computer presentation on what a hovercraft is, how they work, and how they use Newton’s laws of motion. Present it to the class.

You may use software such as Microsoft PowerPoint, OpenOffice Impress, Corel Presentations, or any other software you like. All of these programs are very similar. OpenOffice is a package of programs very much like MS Office, but totally free. http://www.openoffice.org/

The entire project may be found in this document: TO BE ADDED

How to build your own hovercraft

Photos from a hovercraft project

Build a remote control hovercraft!

Can a hovercraft go up the walls?

A simple to build project

Mod your toy helicopter; turn it into a hovercraft

EGR 100 — Hovercraft Design Project: College freshmen majoring in engineering build and design hovercrafts


Hovercraft calculator – used only for building larger hovercraft that can actually carry passengers.