Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum


The Smoking Gun of Cosmic Inflation

Physics_cosmic inflationYoung Alvy Singer got it partially right.The main character in the Woody Allen film Annie Hall explained why he gave up doing his homework: “Well, the universe is everything, and if it’s expanding, someday it will break apart and that would be the end of everything!”

The Harvard-Smithsonian Center for Astrophysics recently announced that the BICEP2 collaboration (its research partnership with Caltech/JPL, Stanford/SLAC, and UMinn) had observable evidence to prove how this expansion got started from the point of the Big Bang: through cosmic inflation.  “These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was,” said Harvard theorist Avi Loeb. Physics for the 21st Century at Learner.org provides explanatory text, images, and video to help you make sense of the discovery and the theories that led to it.

Start by looking at the text for unit 4 on String Theory to understand how cosmic inflation is responsible for the structure of the universe as it is today.

Short of running backwards the movie of all time, the Cosmic Microwave Background, or CMB, is the best link to the first moments of the development of matter. The CMB is the detection of the relic gas radiating from the Big Bang. Astrophysicists also have been able to find in their data the finger prints of gravitational waves, which are described as ripples in space-time. Dr. Nergis Mavalvala of MIT explains the relation of gravitational waves to today’s astronomy. Watch the segment of the video Gravity, beginning at 14:30 through 16:21, to learn about how these waves are propagated.

The final unit looks in on the work of two astrophysicists, Robert Kirshner and David Spergel, both trying to determine the cause of the acceleration of the expansion of the universe and whether there may be an end to it. Their chief suspect is Dark Energy. Their research may assuage Alvy Singer’s concern about the universe ultimately breaking apart.

Crystal Clear: Celebrating the International Year of Crystallography

Chemistry_saltcrystalsWhat do diamonds, ice, sand, and table salt have in common? Like most solids, they have crystalline structures: they are made up of atoms or molecules arranged in a regular, repeating order. A century ago, scientists developed a technique called x-ray crystallography that made it possible to analyze the structure of crystalline solids. Since that time crystallography has become a key tool in many scientific fields, including mineralogy, medicine, archaeology, and food science. Twenty-three Nobel Prizes have been awarded for discoveries that relied on crystallography.

The United Nations and the International Union of Crystallography have proclaimed 2014 the International Year of Crystallography to educate people about this versatile technique, which is still relatively unknown to the general public. Since crystallography is widely used in many different scientific fields, this event offers a teaching hook for chemistry, physics, and biology classes.

Annenberg’s new chemistry course, Chemistry: Challenges and Solutions, unit 13, describes the chemical bonds that hold crystalline substances together, and the insight that launched the field of crystallography. British physicist William Henry Bragg and his son William Lawrence Bragg recognized that when a beam of X-rays was aimed at a crystal, planes of atoms within the crystal would diffract (scatter) the rays in patterns that could be used to map the crystal’s internal structure. The Braggs shared a Nobel Prize in 1915 for their work.

Physical Science, session 5, “Density and Pressure,” explains X-ray diffraction and how scientists can use it to reconstruct the size and shape of particles that are too small to be seen with the naked eye. X-rays make this kind of visualization possible because their wavelengths are short enough to interact with individual atoms of molecules.

Crystallography generated key insights in early medical research. Dorothy Crowfoot Hodgkin, a British chemist, used it to map the structures of insulin, penicillin, and vitamin B-12. In 1964 Hodgkin became the third woman to receive the Nobel Prize in chemistry, following Marie Curie and Irène Joliot-Curie. Another key advance occurred when researchers found ways to crystallize biological materials, such as proteins and DNA. In Annenberg’s Rediscovering Biology course, unit 2, “Proteins and Proteomics,” Ned David describes the rapid evolution of techniques for crystallizing proteins. Drug designers use crystallography to visualize the three-dimensional structure of a protein so that they can find the best place for a drug to bind snugly to the protein.

The invention of synchrotrons (large particle accelerators that generate intense light and x-rays) has furthered the growth of crystallography. For examples of crystallography’s diverse applications, see the web page for x-ray scattering research at Lawrence Berkeley Laboratory’s Advanced Light Source. The International Year of Crystallography’s learning page has images, video and audio clips, and links to other online resources about crystallography.   

How will you be teaching about crystallography in 2014?

Expanding Girls’ Horizons in Science & Engineering Month: Astronomer Vera Cooper Rubin Persists

Physics_rubinWhat keeps scientists like Vera Cooper Rubin moving forward when the obstacles in her way are insurmountable by others? Born in 1928, Rubin faced educational limitations set on women during her time: a high school teacher who discouraged her from pursuing science, Princeton’s then policy not to accept women into astronomy programs, and skeptical peers in the science field. But she persisted in her work and gained reputable recognition as an astronomer.

In the 1970s, Rubin and collaborator Kent Ford made a significant discovery in physics. They measured the rotational velocities (how fast they spin) of interstellar matter in orbit around the center of the nearby Andromeda galaxy. Then they compared these studies with those of other galaxies and were able to infer that the galaxies must contain dark matter.

Read how Rubin and Ford arrived at their conclusion and what that meant for understanding dark matter in Physics for the 21st Century, unit 10, section 2, Initial Evidence of Dark Matter. And if you teach students who are curious about science, use Rubin’s story to encourage them to follow their interests. One of them might end up solving the mystery of dark matter altogether.

Expanding Girls’ Horizons in Science & Engineering Month: Lene Hau Stops Light

Physics_7_Hau_labHave you seen the AT&T 4g network ad in which a friendly guy in a suit asks a group of young children, “What’s better, faster or slower?” The children sing out “Faster!” and give examples of things that are fast: “my mom’s car,” “a space ship,” “a cheetah.” None of them mentions light, which travels close to 200,000 miles per hour. Anything that moves that fast has to be unstoppable, right? Wrong. Superman could stop a speeding train, but it took a super woman to stop light.

Before I get to physicist Lene Hau’s story, let’s ask why anyone would want to stop light. While the process of slowing or stopping light is incredibly complex and precise, the reason for doing so is quite simple. Light can carry a lot of information very quickly. If you can pack light with gigantic collections of information and route it to super computers, you can process more data—solve more problems—more quickly than with the puny computers we use today.

While Physics for the 21st Century is designed to explore the frontiers of modern physics, unit 7, Manipulating Light, is also a testament to the profound contributions that women are making to science. Dr. Lene Hau, recipient of a MacArthur Fellowship “genius grant,” stopped light by ignoring skeptical colleagues, by using science and mathematics to tame the weird world of quantum mechanics, and by relentlessly pursuing her goal. She is one of two featured scientists in the unit 7 video. Also, see her talk about the process of slowing down light in this video from the Harvard YouTube channel.

Physics_7_Hau_signDr. Hau never stopped calculating:

“I remember I was taking off in the airplane from Boston to Copenhagen and following the speed of the airplane on the big screen there and thinking, oh, wow; now we are going faster than my light pulse in the lab. I was calculating if I had sent a light pulse from Boston at the time I left in the airplane I would arrive in Copenhagen an hour before my light pulse.”

And she reveled in the wonder of her accomplishment:

“. . . in the middle of the night and you were just sitting there and you’re just the first person in history being in this regime of nature seeing light go this slow. It was really amazing . . .”

To make her breakthroughs—first to slow light to “bicycle speed” and then to stop it altogether—Dr. Hau lived in a world of both absolutes and mystery. Her team put the fastest known thing into the coldest known thing. Light, at billionths of a degree above absolute zero, stops. Essentially, Dr. Hau and her team were manipulating light and atoms so that they share characteristics that they don’t appear to have in common in the non-quantum world. A mile-long pulse of light is compressed to .02 millimeters (less than half the width of a hair) and sent through a Bose-Einstein condensate, a super cold cloud of sodium atoms. When the light is slowed, the information carried by the light can be imprinted in the sodium matter.

Even though Dr. Hau was manipulating light in the miniscule, sub-atomic world, she never thought small or shied from taking risks:

“If you want to probe something, probe it as hard as you possibly can without it totally blowing apart.”

We are still some years away from seeing Dr. Hau’s amazing work being put to practical use in quantum computing and other still-unknown applications, but now is just the right time to applaud her and join her in imagining where she will take us from here. Use her story to inspire your students to pursue exciting work in the sciences.

Teaching Newton’s Laws of Motion



Newton’s laws of motion were written more than 300 years ago and they are still in force.  But how do you teach them so they have impact on students, who often seem inert?

First you must ask yourself the question: Is Newton’s work still relevant in today’s high-tech world? For many years, physicists have been scratching their collective heads about how gravity can exist alongside of the other three forces of nature (electromagnetic, strong nuclear, and weak nuclear forces) because it is many factors weaker than the other forces — the 98-pound weakling at the beach, if you will.

Physicists at the University of Washington’s Eot-Wash lab are testing Newton’s Inverse Square Law at extremely minute distances, less than a hair’s width. In the program “Gravity” from Physics for the 21st Century, you’ll see their experiments and what they have learned. This law defines the force bodies have on each other at various distances. It gives students a glimpse into long-standing physics puzzles and the people working on them.

Students can test their understanding of the 2nd and 3rd laws by observing automobile collisions. You don’t have to go to the street corner and wait for two cars to crash, you can go to Learner.org’s student interactive Amusement Park Physics in the bumper cars section of the virtual park.  The bumper cars provide collisions between moving cars and cars at rest, with drivers of various masses. Students can predict the resulting motion after the collision and perhaps become more aware drivers in the future. (One can always hope.)

Newton’s laws of motion are explained with tabletop demonstrations that use CDs, balloons, eggs, and other common objects in workshop 7 of the Science in Focus: Force and Motion. Advance the video slider to about 29 minutes into the VOD at where you will also learn about how great thinkers from before Aristotle to Newton pondered the questions of the nature of forces and motion acting on objects.

Or you can visit Newton and Galileo in their studies as they work on their theories, in The Mechanical Universe…and Beyond program 6, “Newton’s Laws,” and get a feel for the times of both scientists whose names are synonymous with motion today.

These approaches to teaching Newton’s laws should give your students many ways to think about Newton’s simple and elegant set of rules for all matter.

Ferris Wheel Day (February 14, 1859)

Minnesota Historical Society

George Washington Gale Ferris, an American engineer and inventor, invented the Ferris wheel for the Chicago World’s Columbian Exposition in 1893. The first Ferris wheel, built specifically for the fair, was 250 feet in diameter and could carry 40 passengers in 36 coaches.

See a picture of the first Ferris wheel and related questions in Primary Sources, “World’s Fair Photograph.”

In America’s History in the Making, unit 16, “A Growing Global Power,” David Cope, former social studies teacher and adviser for World’s Fair documentaries, says the Columbian Exposition in Chicago provided America the opportunity to show the world its industrial might.

Students practice trigonometry by developing functions to describe the height of a Ferris wheel rider. Watch this lesson unfold in Teaching Math: A Video Library, 9-12, program 7, “Ferris Wheel.”