Exploring Physics with Intertribal Youth at UCSD

[This is about a physics outreach event at UC San Diego this summer, and it will be published in the UCSD Fall Newsletter. Many thanks to Susan Brown for editing assistance.]

How does a speaker system work? Why do figure skaters spin faster when they draw in their arms and legs? Where does static electricity come from? How much energy does a lightbulb use? Native American students asked these kinds of questions on Friday, July 25th, as they participated in a physics outreach event at UC San Diego.

As part of a two-week visit to UCSD, San Diego State, and Cal State San Marcos, twenty five middle and high school students traveled to campus on Friday morning to engage in hand-on activities and demonstrations with physics researchers, postdocs, and grad students. They’re part of Intertribal Youth, a fourteen year-old organization directed by Marc Chavez and based in California with the purpose of enriching the lives of young students.


The event on Friday was primarily organized by Adam Burgasser, an associate professor of physics, and Dianna Cowern, an outreach coordinator, both at the Center for Astrophysics & Space Sciences. Adam, who has worked extensively on outreach and diversity programs, contacted the ITY group through the UCSD Office of Equity, Diversity and Inclusion, which resulted in this event at Mayer Hall (Revelle College) and other planned outreach events.

We planned demonstrations in five physics areas, including electricity and magnetism, vibration and sound, optics and light, solar energy, and momentum. Unfortunately, we had to skip the solar energy one because it was surprisingly cloudy for San Diego—the marine layer persisted all morning. We divided the students into four groups, and they spent about twenty five minutes exploring and learning about each of the other topics.

Drew Nguyen and I facilitated demonstrations on Mayer Hall’s balcony on linear and angular momentum, including an air rocket, a rotating chair and hand-crank bicycle wheel, and a basketball and tennis ball. Students discovered that it’s easy to make a simple rocket: we held a 2-liter plastic Coke bottle on a wooden base, poured in a little water and pumped in air with a bike pump, and then let go and watched it take off and fly a couple stories into the air! (I got a bit wet as water spurted out the bottom.) Students experimented with it and some were surprised that without the water to keep the air pressure high, the bottle had no thrust and remained grounded.


In another demo, students would spin each other on a rotating stool while keeping their arms extended. Then when the seated person brings in their arms, they rotate faster, just like a rapidly spinning figure skater, which demonstrated the conservation of angular momentum. In a related demo, we hung a bike wheel from a rope attached to its axis, and when it’s spinning rapidly, it could spin vertically or tilted, and the person holding the rope could feel the momentum of the wheel. This demo always impressed students, such as Marla and Dakota. Dakota thought it was “crazy and weird” that the wheel would rotate this way, until he and the other students figured it out. Marla realized that it’s the same principle that keeps a tilted bike from falling over when someone’s riding around a curve in the road.

The students enjoyed playing with these and other demos. For example, inside Mayer Hall, they explored a bunch of experiments related to electricity and magnetism. They particularly enjoyed the van de Graaff generator, which is a hollow metal globe on top of a stand and which uses a moving belt to generate static electricity. When you touch it with particular rods, which might be like lightning rods, it generates sparks—and the students sometimes shocked each other too. But touching the globe with your own hand makes your hair stand on end. It was hard to tear the students away from these exciting experiments and continue with them all over the course of the morning.

During those couple hours, they actively learned a couple things about physics and engaged with real-life scientists. These outreach events help to spark the students’ interest in science, and particularly in physics and astronomy, and we hope to inspire a few of them will be inspired to pursue science further as they continue their education and become the next generation of scientists.

After the demonstrations, everyone loved the liquid nitrogen ice cream, which Adam and the students made on the patio. It tastes a lot like regular ice cream, but it’s much more fun. Over the rest of their visit, the ITY students enjoyed other activities in the San Diego region including a “star party” at the La Jolla Indian Reservation on the following Tuesday night.

People’s Climate March in San Diego

Yesterday afternoon was hot, sunny, and dry in southern California, and it was as great a time as any to draw attention to climate change and demand action on it. I was one of 1,500 people who participated in the People’s Climate March and rally in San Diego, which started at City Hall and the Civic Center, went down Broadway past the train station, and ended at the County Administration Park.


It was exciting and inspiring to be involved in what may have been the largest climate protest in history. At least 300,000 people participated in the march in New York, where the UN climate summit is taking place. According to a speaker for SanDiego350, which was one of the groups organizing the local events, there were marches and rallies in over 3000 cities around the world. They were also widely reported in the media, for example in the New York Times, LA Times, Guardian, and Democracy Now. I’m not a good photographer, so I grabbed the photo above from the SD Reader and the NYC photo below came from the Guardian. I’m sure there were a few differences between the people participating in the SD and NYC protests, as I saw many people wearing flip-flops, heard chants of “¡Si Se Puede!”, and saw a few Mexican wrestler masks too.


From what I could see, it was a very diverse crowd in terms of gender, race, class, and age. Climate change is now more than just an environmental issue—many people from unions, religious groups, and students and teachers attended too. People held signs and yelled chants saying a variety of things: demands for clean energy, green jobs, climate justice, and an end to fracking were common. As I mentioned in my previous post, many Californians are concerned about drought and water policies too, and I saw a few signs about these issues as well. Although we can see widespread support for action on climate change, it’s clear that conservatives and Republicans didn’t show up; climate change has become an increasingly partisan issue in the US over the past few years.

Organizers had great speakers and musicians at the beginning, middle, and end of the march. Many political leaders attended, including Rep. Susan Davis, the Congressional representative for our district. Speakers included: Todd Gloria, City Council president and former interim mayor, who gave a rousing speech to kick off the march; Nicole Capretz, Director of Environmental Policy for the city, who cited labor, women’s rights, and civil rights movements as inspiration; Monique Lopez, Environmental Health Coalition advocate, and City Council member David Alvarez. (More details about the speakers are here.)

Capretz and Gloria outlined their Climate Action Plan, which includes ambitious goals in five areas: energy and water efficient buildings; clean and renewable energy; biking, walking, and transit; zero waste; and climate resiliency. From what I can tell, their emphasis is on the first three prongs. The plan would cut San Diego’s greenhouse gas emissions by 15% by 2020 and nearly half by 2035. More than half of San Diego’s GHG emissions come from transportation, which is why investment in public transit, bike- and pedestrian-friendly areas, incentives for car-pooling, and other related measures are important. However, the plan already faces some resistance from business groups, who only approve of voluntary, incentive-based programs (but not mandatory measures) to get property owners to pursue upgrades to improve buildings’ water and energy efficiency. Mayor Kevin Faulconer is preparing to release his own version of the plan. If it’s watered down, I think he can expect San Diegans to organize more climate marches in the future.

[Although I’m a scientist and always try to lay out the facts in my blog posts, I want to be clear that I’m speaking my personal opinions here.]

Californians and the Environment

The Public Policy Institute of California (PPIC), a nonprofit, nonpartisan thinktank based in San Francisco, recently conducted a survey of Californians’ views of environmental issues. This is particularly important in light of the ongoing drought in the southwest and the upcoming elections in November. According to the report (available in PDF format), the results are based on the responses of 1,705 adult residents throughout California, interviewed in English and Spanish by landline or cell phone, and they’re estimated to have a sampling error of 4% (at the 95% confidence level). I’ll describe what I see as their most interesting results, and if you want more information, I encourage you to read the report.

Global warming: A strong majority say they are very concerned (40%) or somewhat concerned (34%) about global warming. Approximately two thirds of Californians (68%) support the state law, AB 32, which requires California to reduce its carbon emissions to 1990 levels by 2020, but the partisan divide (Democrats at 81% vs Republicans at 39%) has grown on this issue. 80% of Californians say that global warming is a very serious or somewhat serious threat to the economy and quality of life for California’s future. Only 45% of people are aware at all about the state’s cap-and-trade system, which took effect in 2012, but after being read a brief description, Californians are more likely to favor (51%) than oppose (40%) the program. Under a recent agreement between the governor and legislature, 25% of the revenues generated by the cap-and-trade program will be spent on high-speed rail, 35% on other mass transit projects and affordable housing near transit, and the rest for other purposes.


Energy policies: overwhelming majorities of adults favor requiring automakers to significantly improve the fuel efficiency of cars sold in the U.S. (85%) and increasing federal funding to develop wind, solar, and hydrogen technology (78%). Strong majorities support the requirement that oil companies produce cleaner transportation fuels and the goal that a third of California‚Äôs electricity come from renewable energy sources. But residents’ support declines significantly if these two efforts lead to higher gas prices or electricity bills. (This is unfortunate, because gas and oil companies are heavily subsidized in the US, and maybe our gas and electricity bills are too low.) Most residents (64%) oppose building more nuclear power plants, as they have since the Fukushima disaster.

The survey includes other contentious issues: 54% of Californians oppose hydraulic fracturing, or fracking, for oil and natural gas extraction. But a majority (53%) support building the Keystone XL pipeline.

Water policies: Asked about some of the possible effects of global warming in California, majorities say they are very concerned about droughts (64%) or wildfires (61%) that are more severe. 35% say that water supply or drought is the most important environmental issue facing the state today (which is 27% higher than the fraction in a 2011 survey), and this is the first environmental survey in which air pollution was not the top issue. In another measure of concern about drought, strong majorities of residents (75%) say they favor their local water districts requiring residents to reduce water use. The CA legislature is discussing a $11.1 billion state bond for water projects that is currently on the November ballot, and a slim majority of likely voters would support it (51% yes, 26% no).

If you’re interested, the PPIC has useful information and publications on water policies and management of resources: see this page and this blog post series. Water policy analysts argue that in the Central Valley, where most agricultural water use occurs, the failure to manage groundwater sustainably limits its availability as a drought reserve. In urban areas, the greatest potential for further water savings lies in reducing landscaping irrigation—a shift requiring behavioral changes, not just the adoption of new technology. Finally, state and federal regulators must make tough decisions about how and when to allocate water during a drought: they must balance short-term economic impacts on urban and agricultural water users against long-term harm—even risk of extinction—of fish and wildlife.

People’s Climate March

This is a different topic and has nothing to do with the survey, but I want to use this opportunity to plug the People’s Climate March, which will be taking place on Sunday. (This website can direct you to events in your area.) One of the biggest marches and rallies will be in New York City, where the UN climate summit will soon be taking place. Even Ban Ki-moon will be participating! For San Diegans, you can find information about Sunday’s downtown events here. Californians also organized a “People’s Climate Train” to take activists and participants by train from the Bay Area through Denver and Chicago to New York, where they’ll be arriving tonight. Finally, I recommend reading this well written piece by Rebecca Solnit on Dr. Seuss’s The Lorax and the need to raise our voices on Sunday.

Astrophysicists Gather in Aspen to Study the Galaxy-Dark Matter Connection

I just returned from a summer workshop at the Aspen Center for Physics, and I enjoyed it quite a bit! The official title of our workshop is “The Galaxy-Halo Connection Across Cosmic Time.” It was organized by Risa Wechsler (Stanford) and Frank van den Bosch (Yale) and others who unfortunately weren’t able to attend (Andreas Berlind, Jeremy Tinker, and Andrew Zentner). The workshop itself was very well attended by researchers and faculty from a geographically diverse range of institutions, but since it was relatively late in the summer, a few people couldn’t come because of teaching duties.

photo 1

Since I grew up in Colorado, I have to add that Aspen is fine and I understand why it’s popular, but there are many beautiful mountain towns in the Colorado Rockies. Visitors and businesses should spread the love to other places too, like Glenwood Springs, Durango, Leadville, Estes Park, etc… In any case, when we had time off, it was fun to go hiking and biking in the area. For example, I took the following photo after hiking to the top of Electric Peak (elev. 13635 ft., 4155 m), and lower down I’ve included photos of Lost Man Lake (near the continental divide) and the iconic Maroon Bells.

photo 11

The Aspen Center for Physics (ACP) is a great place for working and collaborating with colleagues. As they say on their website, “Set in a friendly, small town of inspiring landscapes, the Center is conducive to deep thinking with few distractions, rules or demands.” As usual, we had a very flexible schedule that allowed for plenty of conversations and discussions outdoors or in our temporary offices. Weather permitting, we had lunch and some meetings outside, and we had many social events too, including lemonade and cookies on Mondays and weekly barbecues. It’s also family-friendly, and many physicists brought their spouses and kids to Aspen too. I’ve attended one ACP summer workshop on a similar theme (“Modeling Galaxy Clustering”) in June 2007, and it too was both fun and productive. Note that the ACP workshop is very different than the Madrid workshop I attended earlier this summer, which had specific goals we were working toward (and I’ll give an update about it later).

This year’s Aspen workshop connected important research on the large-scale structure of the universe, the physics of dark matter halo assembly, the formation and evolution of galaxies, and cosmology. We had informal discussions about the masses and boundaries of dark matter haloes in simulations, ways to quantify the abundances and statistics of galaxies we observe with telescopes and surveys, and how to construct improved models that accurately associate particular classes of galaxies with particular regions of the “cosmic web”—see this Bolshoi simulation image, for example, and the following slice from a galaxy catalog of the Sloan Digital Sky Survey:


While some of these issues have plagued us for years and remain unresolved, there are some subtle issues that have cropped up more recently. We (including me) have successfully modeled the spatial distribution of galaxies in the “local” universe, but now we are trying to distinguish between seemingly inconsistent but similarly successful models. For example, we know that the distribution of dark matter haloes in numerical simulations depends on the mass of the haloes—bigger and more massive systems tend to form in denser environments—as well as on their assembly history (such as their formation time), but these correlations can be quantified in different ways and it’s not clear whether there is a preferred way to associate galaxies with haloes as a function of these properties. For the galaxies themselves, we want to understand why some of them have particular brightnesses, colors, masses, gas contents, star formation rates, and structures and whether they can be explained with particular kinds of dark matter halo models.


The main purpose of these workshops is to facilitate collaborations and inspire new ideas about (astro)physical issues, and it looks like we accomplished that. The previous workshop I attended helped me to finish a paper on analyzing the observed spatial distribution of red and blue galaxies with dark matter halo models (arXiv:0805.0310), and I’m sure that my current projects are already benefiting from this summer’s workshop. We seem to be gradually learning more about the relations between galaxy formation and dark matter, and my colleagues and I will have new questions to ask the next time we return to the Rockies.

Finally, here are those Maroon Bells you’ve been waiting for: