Put This Date on Your Calendar: August 21, 2017

A total solar eclipse will be visible in South Carolina on Monday, August 21, 2017. 
Neil DeGrasse Tyson, the director of the Hayden Planetarium at the Rose Center for Earth and Spance in New York tells us to put it on our bucket lists because it is both rare and spectacular. 

The moon’s shadow will sweep along a 70 mile wide path at 1.5 times the speed of sound, providing witnesses in that path with just about 2 minutes of spectacle. Those not in the path will see only a partial eclipse.

For those in the path “It will be like having a 360-degree sunset all around you says NASA’s Lika Guthathakurta. ‘Stars appear. The temperature drops. You can actually hear chirping of grasshoppers. So, animals actually naturally go back to their nocturnal behavior.'” 

Jay Pasachoff, a Williams College astronomer and eclipse expert will travel from his home in Massachusetts to a location along the path because “It’s a tremendous opportunity… to see the universe change around you.” (http://www.space.com/33797-total-solar-eclipse-2017-guide.html)

For those of us who are not astronomers or eclipse experts this rare event is a prod to our curiousity about how the universe, in this case the some of the workings of sun, moon, and Earth.

The textbook model of a solar eclipse is pretty simple.

A solar eclipse happens when the moon passes between Earth and the sun during the new moon phase. A lunar eclipse happens when the moon is behnd Earth during the full moon phase. 

But the simple explanation leaves two interesting questions unanswered, as “why isn’t there an eclipse of the sun each month when the new moon passes between Earth and sun?” and “Why does the path of the eclipse move from west to east?”

To fix the model, we need to add some important facts.

First, moon’s orbit is not perfectly round which means that at its perigee (or lowest point in the orbit) is about 225,000 miles from Earth and at its apogee (or highest point in the orbit) is 251,900 miles from Earth. Its mean distance from Earth is 239,000 miles.

Second, the moon’s orbit is titled by 5 degrees relative to Earth’s orbital plane. To visualize this imagine that you have two rings, a larger (representing Earth’s orbital plane as it revolves around the sun) and a smaller (representing the moon’s as it orbits Earth). If you put the smaller ring onto the larger ring and tilt it slightly (about 5 degrees) you will see that there are only two points on the ring at which the two rings are in the same plane. 

As the moon orbits Earth, (following the path of the smaller ring) it will ascend relative to Earth’s orbital plane for half of its orbit and decline for the other half.

If new moon occurs when the moon is at the top of its orbit, as it moves between Earth and the sun the moon’s shadow will miss Earth high. It it’s at the bottom of the orbit, the shadow will miss low. 

There are two points on the orbit when it crosses what is called the ecliptic, or the plane of Earth’s orbit around the sun called the “lunar nodes.” The line of the nodes align with the Sun every 346.6 days (= an Eclipse Year).

Now, our model is more complete and we can derive from it that the following conditions must be met in order to have a total eclipse of the Sun:

The moon is in the phase called new moon because it is then that it passes between Earth and Sun.

The moon is at the lunar node and thus in the same orbital plane as Earth and Sun.

Moon is relatively closer to Earth (>236,000 miles) because its shadow (umbra) will only extend 236,000 miles. If the moon is too far away, its shadow won’t fall on Earth’s surface.

All three conditions will be met on August 21, 2017, with moon’s shadow falling on the U.S. beginning in Oregon and ending in Charleston, South Carolina.

We are accustomed to thinking of the sun and moon rising in the east and moving westward. So why does the path of totality move from west to east, from Oregon to South Carolina?

You can work this out for yourself by simply changing your point of view from Earth to imagine that you that you can travel far enough into space so that you can see the sun, earth and moon in one view. 

You can see the earth rotating on its axis counterclockwise and the moon, orbiting around it, moving above it also moving counterclockwise.

As it moves across Earth, you can see its shadow moving counterclockwise, towards the east from the west.

This also helps to explain why the shadow moves so very quickly, giving each obsever only about two minutes of spectacle. 

According to NASA the moon orbits toward the east at about 3,400 km/hour while Earth rotates to the east at 1,670 km/hour near the equator. The moon’s shadow is therefore moving at 3,400 – 1,670 km/hr = 1730 km/hr.

According the NASA, you would need to travel at Mach 1.5 to keep up with the moon’s shadow!

While our model for understanding a solar eclipse is complete, a solar eclipse makes it possible to study another phenomenon that is one of astronomy’s great mysteries. 

When the moon’s shadow completely blocks the Sun, the solar corona, a beautiful aura will surround the moon, revealing it for scientific study. The solar corona is composed of plasma (the fourth state of matter). Mysteriously, the corona is much hotter than the sun’s surface. How can something farther from the source of heat be hotter than material at the source?

We will examine this mystery in a future blog.

Resources:

There are many, many resources for understanding eclipses: The following are just a few. In addition there are many apps that allow for interactive study of solar and celestial events.
MrEclipse.com
space.com
NASA.com
http://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit2/eclipses.html

Women in Science: Komal Dadlani: Making Available Science Available to All

Robert Hooke engineered a better microscope and an accurate clock.
Isaac Newton is credited with the invention of the reflecting telescope.
Robert Boyle’s experiments required the development of a vacuum pump.
The practice of observational science demands good instruments; how can you tell how fast the ball rolls without a way to accurately count the seconds?
Four centuries of invention have supplied scientists with a large array of technologies that make modern scientific investigation possible.
Unfortunately, these technologies are mostly available at the high end and that unfortunately also means, “not in schools.”
This doesn’t mean that the technology for schools is not available, but it is expensive, especially for schools that serve economically challenged communities.
Komal Dadlani who was born in Chile, where only 2 out of every ten schools has a science lab, was fortunate enough to graduate from one that did and thus was able to go to university and graduate with a master’s degree in biochemistry.
To share her good fortune, she searched for a way to provide the opportunity for a science education with others.
Her “ah ha!” moment came with the realization that while schools don’t have well-equipped labs, large proportions (between one-third to more than half) of their students do have smart phones.
The development of the smartphone, first with the iPhone from Apple and then from a host of vendors has meant that technologies that were once available only to high-end users like NASA are integrated into smartphones.
Magnetometers make the phone’s compass possible; promixity sensors signal the phone’s operating system when the phone is placed next to the ear to take or make a phone call. Quite ordinary smartphones have gyroscopes, photodetectors, acceleromters, barometers, thermometers, sensors that make them “smart.”
So while K-12 schools that do not have laboratory equipiment, these schools could take advantage of the smartphones that many of their students carry with them daily?
Tapping the power of the smartphone sensors was how Ms Dadlani and colleagues solved the problem.
Komal and her team is now in the U.S. in the process of creating a new business which they call Lab4U.
“‘We leverage these senors and design experiments,’ she explains'” in an April 7 article in People magazine.
They have release two apps (both available for both IOS and Android), one for physics and one for chemistry.
One (which I have installed on my relatively old iPhone 5) is Lab4Physics.
Once you create a free account, the user has accesss to camera, the accelerometer, the sonometer and the speedometer that can capture and graph data. You can “play physics” and do experiments in movement, force and energy, and sounds.
There is also Lab4Chemistry uses software to transform your smarphone into a colorimeter that allows for the calculation of concentrations of chemical solutions and to use spectrophotometry.
The company is still a startup and not established as yet but it demonstrates a key idea that has driven STEM for four centuries: “it’s not strength. It’s not intelligence. It’s ADAPTABILITY TO CHANGE” that makes new things possible. (https://lab4u.co/lab4physics/)
Resources:
Crunch Base: Komal Dadlani. Retrieved from https://www.crunchbase.com/person/komal-dadlani#/entity

Lab4U

Toyota Mothers of Invention: Retrieved from http://paidpost.nytimes.com/toyota/mothers-of-invention-presented-by-women-in-the-world.html

You and Your Many Clocks

What is it about the Monday following the switch from standard to daylight saving time?

There is a predictable pattern of bad things happening after our “spring forward”: a spike in heart attacks, strokes, and traffic accidents, and even noticeable reduction in worker productivity that are connected to the loss of sleep because “even small changes in sleep could have detrimental effects” including full-blown illnesses.” (Reuters, 2017)

This is because our bodily processes depend upon their precise synchronization with the natural cycles of light and darkness to work properly. Loss of an hour of sleep can disrupt synchronization so that a major disruption can cause serious illness. (Friedman, 2017)

As far back as the 1960s, a German psychiatrist had heard about a woman who was apparently able to keep the demons of her depression at bay by nighttime bicycle rides.  It appeared that going without sleep could “reset” some aspect of the woman’s functioning and relieve the symptoms of depression.

He tested his hunch on a group of his depressed patients by keeping them awake for a single night as a substitute for the nocturnal bicycle ride.

The next day, he was struck by how most of the patients exhibited cheerful optimism rather than their habitual glum weariness.

In another example, physicians in a Milan hospital housing a ward of patients suffering from bi-polar disorder were struck by the fact that patients who occupied rooms that faced east were discharged earlier than those in rooms that faced west. In their reflections about why this was so, the physicians wondered whether the early sun had some therapeutic effect on the patients. (Friedman, 2017)

From ancient times people have observed the effect of day and night on living things, such as flowers opening and closing with sunrise and sunset.

Such observations led 13th century Chinese medical practitioners to connect the cycles of day and night with health and illness.

The actual mechanisms that connect the diurnal cycles to life processes were not discovered until investigators were able to examine biological processes at the molecular level.

The relationship between the organism and the alternation of light and dark based on the solar day is called the circadian cycle, (circa-around; diem-day).

There is now even a whole field of circadian biology whose research has opened new understandings about how we and our environment interact.

The patterns of daylight and darkness are not simply backdrop to our daily lives but  are deeply embedded into our personal biology. In fact, our circadian cycle is tied to the solar day; “it is influenced and kept in check by the daylight cycle.” (Friedman, 2017)

When it gets dark at night a communication channel to the pineal gland is opened activating proteins in the pineal gland that begin to produce melatonin, a hormone that regulates other hormones and is known to help maintain the body’s circadian rhythm. A number of things start to happen, various hormones are activated by the melatonin: your body temperature begins to drop, your kidneys reduce the rate at which they produce urine, and you begin to feel sleepy. (See Melatonin )

Based on this information, it is not difficult to see why the “spring forward”  weekend messes with your circadian cycle. When your alarm goes off on Monday it’s as if you have flown across an entire time zone. You effectively went to sleep in Chicago and woke up in New York, a difference of a whole time zone.  Worse it is probably still be dark,  further confusing your synchronization with the solar day.

Other activities can cause you to get out of sync.

Your television and computer screens emit short-wave length (blue) light that can make it harder to fall asleep.

Shift work especially when the worker is on sometimes during days and then must switch to night work plays havoc and can result in insomnia and even depression. (Moon et al., 2015)

Jet-lag with its fatigue, malaise, poor concentration, and mood changes is the result of flying from one city to another across multiple time zones, leaving your circadian cycle stuck in the time zone you left.  (Friedman, 2017)

So feeling grumpy on the Monday after springing forward is not trivial. The usually temporary malaise is a symptom that several of the many biological clocks that “are believed to exist at all levels of life and play a key role in the maintenance of physiological and behavioral processes” are out of sync.

Chronic disruption of one’s circadian rhythm can cause sleep problems which can adversely affect health. According to research a significant proportion of the adult population does not sleep well and night and has difficulty staying alert during the day…(Harrington, 2010) & (Ray and Reddy, 2016)

There are things you can do to help keep yourself in sync. For example, click here for tips on overcoming jet lag.

Resources:

Friedman, R. A. (2017c). Yes, Your Sleep Schedule Can Make You Sick. New York Times. Retrieved from https://www.nytimes.com/2017/03/10/opinion/sunday/can-sleep-deprivation-cure-depression.html?ribbon-ad-idx=8&src=trending&module=Ribbon&version=origin&region=Header&action=click&contentCollection=Trending&pgtype=article

Krishnan, H. C., & Lyons, L. C. (2015). Synchrony and desynchrony in circadian clocks: impacts on learning and memory. Learn Mem

Learning & Memory, 22(9), 426-437. doi:10.1101/lm.038877.115

Moon, H. J., Lee, S. H., Lee, H. S., Lee, K.-J., & Kim, J. J. (2015). The association between shift work and depression in hotel workers. Ann Occup Environ Med

Annals of Occupational and Environmental Medicine, 27, 29. doi:10.1186/s40557-015-0081-0

Ray, S., & Reddy, A. B. (2016). Cross‚Äêtalk between circadian clocks, sleep‚Äêwake cycles, and metabolic networks: Dispelling the darkness. Bioessays, 38(4), 394-405. doi:10.1002/bies.201500056

Reuters (2017) Hate daylight saving time? You may have a point, researchers say. Retrieved from http://www.reuters.com/article/us-usa-daylightsaving-idUSKBN16I0S6

The Union Public Schools: Choosing to be Excellent

The Union Public Schools: Choosing to be Excellent

A school classroom, somewhere in Oklahoma:

The students in this class are to design and build a video game in which the player must guide a cow across a busy highway. A successful program will result in either the cow successfully crossing the road resulting in the player being rewarded with a hand clap while if the cow is hit, the feedback to the player is an “Aw.”

That this is a high school coding class would be a good guess but it is actually a class of first graders engaging in their school’s STEM for all curriculum that begins in kindergarten and continues through high school where the students design mobile apps and web pages, while tackling cybersecurity and artificial intelligence projects. (Kirp, 2017)

Although the vignette suggests an affluent district, it comes from the Union Public School District that hosts 16,000 K-12 students located on the economically challenged east side of Tulsa, Oklahoma. 70% of the students qualify for reduced lunch ( 65.5% white, 31.3% Hispanic, 14.9% AfricanAmerican, 7.9% multi-racial, 6.9% Asian, and 4.9% American Indian). (Union Public Schools Annual Report)

Among other challenges is the fact that 2,700 of the children are English Language Learners (ELL) representing 50 different languages. 

Oklahoma has not been generous in support of its schools, and thus Union has about one-third fewer dollars per student ($7,605) than the national average.

A teacher in Union with twenty years experience and a doctoral degree will earn a bit less  than $50,000 per year. For a comparison, Kirp notes that teacher with similar qualifications in Scarsdale, New York, would earn $120,000.

Despite its challenges Union does better than the national high school graduation average with an 88% graduation rate with 100% of those off to further education. The district’s accomplishments are the results of a decade of serious effort triggered by a meeting in which the superintendent reviewed by name a list of dropouts and was humiliated when none of the district principals were able to account for any of the kids.

Over the decade of rebuilding, the faculty and administration worked at making their schools responsive to the community’s children and youth. (Kirp, 2017)

In an affluent middle-class community, parents provide their children with an abundance of out of school activities: art and music lessons, visits to science museums, summer science camps, sports camps, academic tutoring and enrichment like SAT preparation courses.

In east Tulsa where most families are economically stressed, the Union schools have picked up the role filled by affluent middle class families by transforming themselves into “community schools” that provide enrichment activities for their students and their families by opening early, so parents can drop their children off on the way to work and staying open late and during summers. “They operate as neighborhood hubs, providing families with access to a health care clinic in the school or nearby; connecting parents to job-training opportunities; delivering clothing, food, furniture and bikes; and enabling teenage mothers to graduate by offering day care for their infants.” (Kirp, 2017).

Professor Kirp’s question “Who Needs Charters When You Have Schools Like These?” challenges the assumption that public schools are unable to meet the needs of students and their families.

The power of that assumption provides the rationale for the President’s 2018 budget recommendation that while cutting the federal Department of Education’s overall budget by $9 billion, there would be “an additional $1.4 billion into school choice programs.”

School choice is a policy, which is a tool that is used to accomplish a task, and policy “work best when its actually tailored to the task at hand.” (Williams, 2017)

School choice programs can be connected to equitable access and better outcomes for the traditionally underserved populations when they are well-crafted.

For example, Louisiana rebuilt its hurricane ravaged schools based on the creation of charter schools after Katrina.  A painful learning curve made it clear that the new system would not work without an aggresive accountability system that would ensure that unsuccessful charters were closed. The result is that New Orleans system of public charters is thriving.

Michigan invests heavily in charter schools. Its policies are based on the idea that the more charters the better, and accountability is weak.  The result is that “the unchecked growth of charters has created a glut of schools competing for some of the nation’s poorest students, enticing them to enroll with cash bonuses, laptops,…and bicycles…fighting so hard over students and the limited public dollars that follow them that no one thrives.”

State policy permits unsuccessful schools to shop around for new authorizing agencies and be back in business under a new name. (Zernike, 2016)

Instead of raising all schools the charter movement has resulted in “a total and complete collapse of education in this city,”  according to Scott Romney, a board member of the civic organization New Detroit. ( Zernike, 2016)

Resources:

Kirp, David (2017). Who Needs Charters When You Have Schools Like These? New York Times, April 1, 2017 Retrieved from https://www.nytimes.com/2017/04/01/opinion/sunday/who-needs-charters-when-you-have-public-schools-like-these.html

Williams, Conor P. (2017). School choice is great… Washington Post, January 19, 2017. Retrieved from https://www.washingtonpost.com/posteverything/wp/2017/01/19/school-choice-is-great-betsy-devoss-vision-for-school-choice-is-not/?utm_term=.bac9773ce27e

Zernike, Kate (2016). A Sea of Charter Schools in Detroit Leaves Students Adrift. New York Times, June 28, 2016. Retrieved from https://www.nytimes.com/2016/06/29/us/for-detroits-children-more-school-choice-but-not-better-schools.html

Tags:

accountability, STEM, school choice, public schools, U.S. Department of Education, Louisiana, Michigan, vouchers, charter schools

Phenology: A Study You Perhaps Never Heard of andA Project-Based Learning Opportunity

Building curriculum around project- and problem-based learning is both motivating for students as well as a way to help them connect their own experiences to essential knowledge.
The National Phenology Network provides opportunities for teachers and their students, to engage in project- and problem-based learning and also to contribute usable data that advances out understanding of the interaction between living things and nature’s seasonal cycles.

First a little background about phenology.

On Groundhog Day 2017: Puxsutawney Phil predicted six more weeks of winter eventhough spring was already well-established.

As one of the many newspaper reports put it: “After a mild winter across much of the United States, brought abnormally high temperatures, especially east of the Rockies. Spring weather arrived more than three weeks earlier than usual, …” (White and Fountain, 2017)

Poor Phil! But it’s really not his fault.

In fact, groundhogs across North America are having problems because they are increasingly out of sync with the seasons.

One of the most important adaptations that living organisms make is their synchrony, being on time with nature’s seasonal cycles. 

Insect eating birds time their nesting so that there will be insects to feed the hatchlings, while insects emerge from eggs in synchrony with the plants they will eat. (USGS National Phenology Network)

The groundhog spends the cold winter months when his food is scarce hibernating and living off his store of fat accumulated by gorging on all the wild grasses, berries and farm crops like alfalfa and corn he could find.

Groundhogs begin their annual hibernation when shorter daylight and cooling fall temperatures signals the groundhog’s hypothalamus to release the cascade of hormones that control hibernation. The hormone leptin, for example, slows the groundhog’s metabolism and suppresses its appetite. 

Toward spring when temperatures begin to rise, the production the leptin tapers off and the animal’s appetite increases, eventually waking it up. As the animal transitions from winter sleep to warm weather being in sync with the seasons matters a great deal.

Thirty years ago, Colorado groundhogs came out of their hibernations during the third week in May. Now they are emerging as early as the third week in April. An earlier wake up can be dangerous for the groundhog because it means that there are fewer food sources for an animal that has depleted its energy resources during hibernation. In addition, if snow is still present, the groundhog won’t have access to all of its different burrow entrances and will be at risk of being caught in the open by one of its many predators such as hawks, coyotes, bobcats, and the occasional fox. (Gourdarzi, 2007)

When spring events occur earlier and fall events happen later serious consequences for plants and animals become more likely.

In the southeast, early springs can accelerate the germination of fruit trees making them vulnerable to late freezes. That’s what happened this spring in South Carolina when the March freeze destroyed 85 to 90 percent of the peach crop. (Purvis, 2017)

Warm winters pose another type of problem for fruit trees. Peaches, cherries, apples and pears evolved in a temperate climate. They go dormant when the temperature drops, protecting them from freezes. The cold is actually important to the tree’s fruit production. Peach and apple trees actually require a certain amount of chilling in order for new buds to grow. Peaches require from 800 to 1200 chilling hours while apples need more than 1200 chilling hours. Absent the right amount of chilling during the winter, the spring crop will be late and the fruit less bountiful. (Cold Hardiness of Fruit Trees, 2016)

The industrial revolution with its reliance of coal and oil has brought about a massive increase in the world’s population along with an ever-increasing use of fossil fuels, pumping huge amounts of carbon dioxide into the atmosphere. While there are other factors that “force” climate change (solar variability and volcanic eruptions), climate models based on over a century of weather data, show “that the whole trend in the historical simulations” in the steady rise in global temperature is due to greenhouse gas emissions that are the result of human activity. (van Oldenborgh and others, 2017).

Given the importance of the complex interactions between climate and plant and animal life, it is important to have accurate information about them.

A principal way to acquire such information is by phenological investigation. Phenology is an observational science that can be practiced by citizens of all ages and backgrounds by participating in the USA National Phenology Network (USAnpn). The USAnpn is funded by the U.S Geological Survey, U.S. Fish & Wildlife Service, National Park Service, The University of Arizona and the National Science Foundation.

Phenology (“Nature’s calendar”) employs “status monitoring,” an approach to observing specific organisms by relating their development to the calendar and location. 

Thirty years of phenological data collected by volunteers including even very young students and mapped by date and location shows how the spring in 2017 is about twenty-five days earlier than it was thirty years ago. You can see the maps here.

Phenology is a way to connect students to the natural world as well as to science practices. The Nature’s Notebook Education Program is a “place-based, hands-on” learning opportunity that has potential for educator collaboration and student engagement in project-based learning. You can find more about this at the Nature’s Notebook Website.

Resources:

Gourdarzi, Sara (2007). Global Warming Wakes Groundhogs Earlier. Live Science, February 1, 2007. Retrieved from http://www.livescience.com/1296-global-warming-wakes-groundhogs-earlier.html
Purvis, Kathleen (2017. Brace yourself for a summer without many peaches. Charlotte Observer, March 20, 2017. Retrieved from http://www.charlotteobserver.com/living/food-drink/article139682158.html
USGS National Phenology Network Taking the Pulse of the Planet.
van Oldenborgh, Geert van (KNMI), Andrew King (University of Melbourne), Friederike Otto (University of Oxford) Gabriel Vecchi (Princeton University), Claudia Tebaldi (NCAR and Climate Central) and Heidi Cullen (Climate Central) (2017). U.S. Heat, February 2017. Weather Attribution. Retrieved from https://wwa.climatecentral.org/analyses/us-heat-february-2017/
White, Jeremy & Andrew Fountain (2017). Spring Came Early. Scientists Blame Climate Change. New York Times, March 8, 2017. Retrieved from https://www.nytimes.com/interactive/2017/03/08/climate/early-spring.html
Tags:

phenology, climate change, spring 2017, groundhogs, hibernation, leptin, synchrony, problem-based learning, project-based learning, hands-on

Recent Research: Three Voucher Programs, Indiana, Louisiana, and Ohio

The policy of providing vouchers to pay tuition for public school students to attend private schools aims to give families whose income falls below a certain level or whose children attend schools that are deemed to be “failing” the option of sending their children to a private school.

The principle behind the voucher strategy is the assumption that any given private school is better than any given public school, therefore a child who can attend a private school will receive a better education than in a public school. However, because private schools have historically served children from affluent families, their supposed “better” may be an artifact of their student population.

State voucher legislation has an accountability requirement that private schools accepting state funds must use the state accountability test to measure student progress. This means that researchers are able to compare progress made by voucher students with their peers in public schools using the same criteria, a standards-based accountability examination that covers the same content for both groups.

The fact that students in private schools take the same accountability tests as their peers in public school makes it possible to test the principle results of private school superiority.

Research on voucher programs has yielded mixed results with some students in some settings doing well while other students in other settings show no differences.  So, black students in New York City experienced growth in reading and math but there were no gains for their Hispanic peers in either reading or math. In the District of Columbia voucher program reading scores improved after the third year in the program while there was no improvement in math. There was no evidence of differences in reading scores in Milwaukee. Other educational outcomes like higher rates of graduation were found in New York and DC along with higher rates of college attendance in New York. (Dynarski, 2016)

Indiana, Louisiana, and Ohio each has a voucher program and each of these has been studied over the past year and a half. The question that each of the studies tested was when compared to their academic performance in public school, was their subsequent performance in private school the same, better, or worse.

Indiana’s voucher program began in 2011 and was continued and expanded in 2014. There is now no limit to the numbers of students who can participate. In addition, the means test has been modified to allow families with higher incomes to participate.

In a study conducted by Drs. R. Joseph Waddington and  Mark Berends, respectively from the University of Kentucky and the University of Notre Dame found that students switching from a public school to a public charter experience no differences in achievement. In the case where students switch to a private school using an Indiana voucher, students experienced annual loses of -0.09 SD in mathematics and -0.11 SD in English-Language Arts. Studens who switched to Catholic schools experienced losses of -0.18 SD in mathematics. (Waddington and Berends, 2016, #27765)

The Louisiana Scholarship program was studied by the Education Research Alliance for New Orleans. As with the Indiana study it also found consistently negative consequences for the academic performance of students using vouchers to attend private schools.  A student performing at the 50th percentile in math at a public school who then enrolled in a private school using a voucher saw his/her performance decline to the 34th percentile after one year. If the student was in the third, fourth, or fifth grade, the decline was to the 26th percentile. There were similar declines in reading, to the 46th percentile from the 50th. (Mills et al., 2016)

Finally, research funded by the voucher-friendly Walton Family Foundation and conducted by the Thomas B. Fordham Institute examined the Ohio EdChoice voucher program. The conclusion from the study was that “Students who use vouchers to attend private schools have fared worse academically compared to their closely matched peers attending public schools.” (Dynarski, 2016) & (Figlio and Karbownik, 2016, p. 39)

The three studies of voucher results in Indiana, Louisiana, and Ohio undercuts the assumption that is beneficial to students to move from a public to a private school.

It is a fact that since the decade of the nineties  public schools have been “under heavy pressure to improve test scores” something that private schools have not had to consider.  There is further evidence that public schools actually outperform private schools. 

In a NAEP funded study of NAEP mathematics scores, Lubienski & Lubienski (2006) found that when demographics and location were controlled, public schools “significantly out-scored Catholic schools by over 7 points in 4th grade math, and almost 4 points in 8th grade. math. Of private school types studied…the fastest growing segment of the private school sector, conservative Christian schools, were also the lowest performing, trailing public schools by more than 10 points at grades 4 and 8.” (Lubienski and Lubienski, 2006, p.4)  Note: the public schools in both Ohio and Indiana public schools performed above the national average on the most recent NAEP for fourth grade reading and mathematics.

The mixed results in earlier research on vouchers and the fairly unequivocal results of three studies described above pose interesting questions for both policymakers and parents to consider.

Rsources:

Dynarski, M. (2016). On negative effects of vouchers. Economic Studies at Brookings: Evidence Speaks Reports, 1(48). Retrieved from https://www.brookings.edu/research/on-negative-effects-of-vouchers/

Figlio, David (2016) Evaluation of Ohio’s EdChoice Scholarship Program: Selection, Competition, and Performance Effects retrieved from https://edex.s3-us-west-2.amazonaws.com/publication/pdfs/FORDHAM%20Ed%20Choice%20Evaluation%20Report_online%20edition.pdf

Lubienski, C., & Lubienski, S. T. (2006). Charter, Private, Public Schools and Academic Achievement: New Evidence from NAEP Mathematics Data. National Center for the Study of Privatization in Education. Retrieved from http://nepc.colorado.edu/files/EPRU-0601-137-OWI%5B1%5D.pdf

Mills, J., N., Egalite, A. J., & Wolf, P. J. (2016). Education Alliance for New Orleans. Retrieved from http://educationresearchalliancenola.org/files/publications/ERA-Policy-Brief-Public-Private-School-Choice-160218.pdf

Waddington, R. J., & Berends, M. (2016). School Choice in Indianapolis: Effects of Charter, Magnet, Private, and Traditional Public Schools. Education Finance and Policy. doi:doi:10.1162/EDFP_a_00225

Tags:

school choice, vouchers, private schools, Indiana, Ohio, Louisiana, test scores, parochial schools, types of private schools

The Great Mystery of Biology: The Eukaryote Cell’s Origin

The origin of eukaryotes is one of the hardest and most intriguing problems in the study of the evolution of life, and arguably, in the whole of biology.”(Koonin, 2015)
All living things are composed of either prokaryote or eukaryote cells. The prokaryote cells are simple, basically a blob of protoplasm encased in a cell membrane while the eukaryote cell is larger, possesses a nucleus, (a kind of DNA-packed control room safely enclosed in a membrane), as well as a set of specialized organelles (“little organs”) that are able to perform necessary tasks like storing molecules or protein manufacture. Significantly the eukaryote cell has its own power plant in the form of mitochondria.
For nearly 2 billion years after the appearance of life on Earth, the prokaryote model had Earth to itself. It was and continues to be highly successful at not only surviving but also thriving. Prokaryotes can be found in all of Earth’s habitats from clouds to the depths of the sea, using a repertoire of ways to survive, from the ability to cause disease, use noxious substances like crude oil for food, power themselves with energy from the Sun, and even to swap genes with one another. (Yong, 2014)
The eukaryote cell with its nucleus and mitochondria, doesn’t appear until much later in Earth’s history, about 1.5 billion years ago.
While the prokaryotes “have repeatedly nudged along the path to complexity” and while some groups of prokaryotic cells move in colonies that resemble complex life, “none of them have acquired the full suite of features that define eukaryotes: large size, the nucleus, internal compartments, mitochondria…” (Yong, 2014)
This is why the appearance of the eukaryote (“eukaryogensis”) is “regarded as one of the major evolutionary innovations in the history of our planet” because the eukaryote cell with its mitochondria, its own power plant provides “the host cell with a bonanza of energy, allowing it to evolve in new directions that other prokaryotes could never reach,” and accounts for the reason why all multicellular life is based on the eurkaryotic cell. (Zaremba-Niedzwiedzka et al., 2017 & Yong, 2014)
In an article in Nature published in January 2017, the authors argue that “most recent insights” support a variety of symbiogenesis of eukaryotic evolution. Evidence is that a still mysterious host cell from the domain Archaea merged with “an alphaprotobacterial (mitochondrial) endosymbiont.” (Zaremba-Niedzwiedzka et al., 2017)
That the mitochondria in the eukaryote cell was once a free living bacteria was first proposed by Lynn Margulis in 1967, at the time a graduate student.
Margulis argued that one driver of evolution was symbiosis, with evidence based on the fact that the mitochondria in eukaryotic cells look remarkably like bacteria. Another example for this endosymbiosis are chloroplasts which also look like bacteria. With the coming of new genetic tools, analysis of the chloroplast genome by the University of Illinois’ Carl Woese showed that the chloroplast genes were not at all like the genes in the host cells, but turned out to be the DNA of cyanobacteria. It was also found that the mitochondrial DNA resembles that which is found in the group of bacteria that causes typhus.
New technologies have expanded the tools that are available to track the relationships between organisms, adding new data to the quest to solve the mystery surrounding eukaroygenesis. While the bacteria that contributed the mitochondria to the eukaryote was from the group known as alphaproteobacteria, a group well-known to take up life within the cells of plants and animals as both mutualists and pathogens.(Williams, Sobral, & Dickerman, 2007)
But less is known about the organism from the domain Archaea that was the presumed host in the merger.
In 2015 a team from Sweden’s Uppsala University collected and analysed sediments from an ocean floor field of hydrothermal vents lying between Norway and Greenland called Loki’s Castle. The DNA found in the sample show that these Lokiarchaeota are the “best approximations that we have for that ancestral archaeon that gave rise to us all.” (Yong, 2017)
More searches in places like North Carolina, Yellowstone National Park, and New Zealand, have revealed many more varieties from this group of archaea, which the group has named Asgard (a name from Norse mythology).
The DNA from these organisms have turned up genes that until now that were thought to be unique to eukaryotes. There are genes in the asgard archaea that serve in eukaryotes for building internal skeletons, although the archaea do not have internal skeletons. Other genes are associated with the pinching off of the outer membrane of cells to create little pockets that are used to move molecules around, another eukaryotic capability not found in archaea.
It would be wrong to say that these discoveries have solved the mystery of eukaryogenesis. A lead researcher in this field describes these cells, not as eukaryotes but “primed to become eukaryotes.”(Yong, 2017)
The Agard archaea are perhaps the link that connects the most ancient life to our own.

Resources:
Koonin, E. V. (2015). Origin of eukaryotes from within archaea, archaeal eukaryome and bursts of gene gain: eukaryogenesis just made easier? Philosophical Transactions of the Royal Society B, 370(1678). Retrieved from http://rstb.royalsocietypublishing.org/content/370/1678/20140333
Williams, K. P., Sobral, B. W., & Dickerman, A. W. (2007). A Robust Species Tree for the Alphaproteobacteria. Journal of Bacteriology, 189(13). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1913456/
Yong, E. (2014). The Unique Merger That Made You (and Ewe, and Yew). Retrieved from http://nautil.us/issue/10/mergers–acquisitions/the-unique-merger-that-made-you-and-ewe-and-yew
Yong, E. (2017). A Break in the Search for the Origin of Complex Life. The Atlantic. Retrieved from https://www.theatlantic.com/science/archive/2017/01/our-origins-in-asgard/512645/
Zaremba-Niedzwiedzka, Caceres, E. F., Saw, J. H., Bäckström, D., Juzokaite, L., & Vancaester, E. (2017). Asgard archaea illuminate the origin of eukaryotic cellular complexity. Nature Immunology, 541(7637), 353-358. Retrieved from http://www.nature.com/nature/journal/v541/n7637/full/nature21031.html
See the South Carolina Academic Standards and Performance Indicators for Science 2014: Biology I, Cells as a System, H.B.2.
tags:
South Carolina Biology Standards, eukaryotes, prokaryotes, Eukarya, Archaea, Bacteria, domains, Carl Woese, Lynn Margulis

Nature in the Front Yard: Evolution in the City

 

The voyage on H.M.S. Beagle that led to the theory of evolution took Charles Darwin to many remote places, most famously, the Galápagos Islands, 1000 km off the coast of Ecuador in the Pacific Ocean.

But whether on a Pacific island or in the middle of New York city, the forces of evolution are in operation because science assumes that the universe is a vast single system in which basic laws are consistent no matter where you look. (Quinn et al., 2013)

Actually urban areas are different in one important respect which is that the rapidity of evolutionary forces depends on the “strength of natural selection — the relative benefit that a particular characteristic bestows on its bearer — is strong.” Even a small difference can matter greatly, especially in an urban environment because it is about as extreme and stressful as it is possible to find with its temperatures (warmer than surrounding countryside); its noise (a constant and invasive din that drowns out the usual warning sounds); further the urban landscape is encased in concrete and other substances hostile to the gripping of claws or traction for paws.  Then there are lots of humans, with their tempting trash along with their deadly cats and dogs, their waste that pollutes water, air, and soil.  (Schilthuizen, 2016)

This means that as the world becomes increasingly urbanized, more and more organisms are either being engulfed by urban areas or are gravitating to opportunities found in them.

Biologists therefore are “beginning to realize that the expanding urban sprawl is perhaps not something to be depressed about but something very exciting, as entirely new forms of life are evolving” in them. (Schilthuizen, 2016)

Jason Munshi-South, the director of the Munshi-South “Evolution in the Anthropocene” lab at Fordham University sees New York city as not only one of humanity’s greatest accomplishments but also as the home to native wildlife that are “subject to a grand evolutionary experiment.” (Munshi-South, Ted Ed talk)

Four hundred years ago the territory that makes up modern New York was covered by forest and meadow and was the home to a huge population of white-footed mice.

Four hundred years later the forests and meadows have largely been replaced by city streets, office buildings, multi-storied apartment buildings, and lots and lots of people, with their dangerously fast moving automobiles, noise, food waste, and trash while the white-footed mice are now crowded into the small patches of forest and meadows of the city’s parks. For Munshi-South the mice provide a model of what happens when wild organisms are engulfed by an urban ecosystem.

Advances in genetics have made it possible to identify changes that have occurred in a species because an organism’s genome is a record of its genetic history as well as that of its ancestors.

Genes are short segments of DNA which carry the recipes for creating the amino acids which are the building blocks for the proteins that actually do the cell’s work: its metabolism, its immune response, its reproduction, and so on.

If it happens that a single base pair on a gene changes and the change leads to an advantage for the mouse, for example, more babies, then this change will spread through a population because it will provide the individuals possessing the trait with increased fitness in the competition for survival. (Munshi-South, 2012)

After the examination of several thousand snippets of DNA from the genomes of 191 individual mice taken from 23 sites representing samples of both urban and “wild” environments, and then comparing the results with computer models the investigators were able to trace the history of the population of white-footed mice living in the area around New York.

About 12,000 years ago (coincident with the end of the last North American ice age) when rising sea levels separated Manhattan from the mainland, the genomes of the mice on Manhattan began to diverge from those on the mainland. Then about 400 years ago when Europeans began the settlement that soon became New York, more genetic divergence began to appear as the green space gave way to urban development. As Stephan Harris, a postdoctoral evolutionary biology researcher at Columbia University said, “The exciting thing is that the times of the divergence that we inferred lined up with the arrival of Europeans in New York.” (Netburn, 2016)

In the relatively brief time that New York has been populated by humans, the once genetically similar population of white-footed mice have evolved into genetically distinct populations each inhabiting a different park. The mice in one park are distinctive enough that the home park of a randomly selected New York white-footed mouse can be identified by examining just 18 snippets from its genome.

More significantly, the mice in different parks have developed park-specific traits related to their response to infection, their metabolism, and even their tolerance for environmentally occurring heavy metals like chromium and lead. (Munshi-South, 2012)

You don’t need a berth on the H.M.S. Beagle that will take you around the world to find evolution in action.

There are lots of great opportunities for “citizen science” projects where you can study nature in your home and neighborhood by tracking your local cats or the microscopic mites (Demodox) that are at home in the pores of your skin (yes, yours and mine).

You can find more about these projects at the Your Wild Life website.

 

Resources:

 

Menninger, Holly & Rob Dunn. Your Wild Life: Exploring biodiversity in our daily lives.

Munshi-South, Jason (2017). Evolution in Anthropocene. Retrieved from http://nycevolution.org

 

Munshi-South, Jason (2012). TED Ed.  Evolution in the Big City, retrieved from http://ed.ted.com/lessons/evolution-in-a-big-city

 

Netburn, D. (2016c). Why the City Mouse and the Country Mouse Have Different Genes. Los Angeles Times. Retrieved from http://www.latimes.com/science/sciencenow/la-sci-sn-city-mouse-20160415-story.html

 

Schilthuizen, Menno (2016). Evolution is Happening Faster Than We Thought.  New York Times, Sunday Review, July 23, 2016. Retrieved from https://www.nytimes.com/2016/07/24/opinion/sunday/evolution-is-happening-faster-than-we-thought.html?_r=0#st

 

Quinn, Helen R., Schweingruber, Heidi, Keller, Thomas, & others, A. A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. Washington, DC: National Research Council of the National Academies. Retrieved from http://www.nap.edu

 

tags:

evolution, urban ecosystem, fitness, gene, genome, genetics, white-footed mouse, New York, natural selection, citizen science, project-based curriculum

 

 

Our Ever-Stranger Universe

For most of human history, we believed that what we saw, heard, and felt was all that made up the real world. This changed around the beginning of the 20th century when modern science began to make uncomfortable discoveries such as that by Wilhelm Conrad Roentgen whose discovery of X-Rays revealed that even more of a reality that was invisible and undetectable by our ordinary senses, or by our “common sense.”
Roentgen won the first Nobel Prize for physics in 1901. Subsequent Nobel Prizes have continued to show how our normal world is really composed of many strange new worlds as revealed by microscopes, telescopes, X-rays, and gravity waves.
What we once imagined as being strange (“goblins, ghosts, and things that go ‘bump’ in the night”) are nothing when compared to the strangeness that science has revealed. As the British evolutionary biologist J.B.S. Haldane noted the universe is not only queer, “but even queerer than we can suppose.”
And now it turns out that “everything on Earth, everything ever observed with all of our instruments, all normal matter,” represents only about 5 percent of reality. The remaining 95 percent is composed of something called Dark Matter and Dark Energy, which are undetectable except by their effects.
The road to this discovery began with a series of investations made in the 1970s by Vera Rubin, a researcher at the Carnegie Institute in Washington, DC.
Rubin’s work focused on the dynamics of stars within galaxies, how the gravity within galaxies affects the stars in the galaxy. She was measuring the speed of the stars in various parts in a spiral galaxy by examining the spectra of light emitted by the stars. A star that is moving away from the observer will show that its spectrum will shift toward the red end of the spectrum while one moving toward the observer will shift to the blue end. The shift will be proportional to the star’s speed. (The Doppler Effect: the change in frequency or wavelength of a wave (or other periodic event) for an observer moving relative to its source.)
According to our understanding of the effect of gravity on the motion of stars, those at the center of a spiral galaxy (where there is more mass) should rotate faster than those farther from the galaxy’s center. (The phenomenon is known as the “galactic rotational curve.”) Strangely Rubin’s measurements showed that stars farther from the center of the galaxy were rotating as fast as those nearer the center.
Rubin and a colleague checked their data by examing the motion of stars in 60 other spriral galaxies and found the same outcomes. The outcomes revealed that there was a “galaxy rotational problem.”
Rubin’s solved it by using the rotational speed of the stars she studied in order to calculate how much mass was needed to account for the gravity needed for the stars to attain their observed rotational speed.
Her calculations revealed that the galaxies must contain about 10 times more mass than could be accounted for by the visible stars, and concluded that 90 percent of the mass in the galaxies she tested was invisible. “What you see in a spiral galaxy is not what you get,” Rubin observed. (AMNH, 2000)
Rubin’s results were treated with skepticism until, when in the 1990s, astronomers began to calculate what they anticipated would be the deceleration of the Universe’s expansion. The surprise was that, the Universe appeared to be accelerating instead. Calculations of the total visible mass in the universe against the gravity that was holding galaxies and solar systems together revealed a “missing matter problem.”
Every mass in the universe attracts every other mass proportionally to the product of their masses and inversely proportional to the square of the distance between them. Calculations of the gravity needed to account for how objects are held in galaxies and galaxy clusters, reveals that the visible universe (“everything on Earth, everything ever observed with all of our instruments, all normal matter”) accounts for only about 5 percent of the mass needed. (You can see the calculations required to support these conclusions here.)
The remaining “roughly 68%” of the universe is dark energy while 27% is dark matter. (NASA, Universe)
So the normal matter, what has been studied deeply is not actually normal. What is normal, the “dark” matter and “dark” energy interacts gravitationally just like ordinary matter does—clumping into galaxies and galaxy clusters. It is “dark” because it doesn’t interact in any way that we can so far detect with light. “It is not made up of atoms and doesn’t carry an electron charge.” (Randall, 2017)
This is science, so investigations continue.
Brian Koberlein, an astronomer at Oberlin College, explains the facts that support the Dark Matter/Dark Energy theory.
Since the 1920s discrepencies have been found that are explained by either that our understanding of gravity is wrong or that there is more mass in the universe than we can see.
But our current gravitational model does seem to work and alternatives that have been proposed have been disproved by observation, leading to the conclusion that the second clause in the previous sentence is true.
Next the proposition that there are examples of mass that only interacts weakly with light is true. Neutrinos have mass and weakly interact with light but there must be additional types of dark matter.
Koblein concludes with the statement that we “know…how much Dark Matter and Dark Energy. there is in the universe, as well as its distribution among the galaxies. “Dark Matter is not just a name we use to hide our ignorance.”

Resources:
Kobelein, Brian (2017). Dark Matter Works. Retrieved from https://briankoberlein.com/page/2/?s=dark+matter

NASA Universe. Dark Energy, Dark Matter. Retrieved from https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

Randall, Lisa (2017). “Why Vera Rubin Deserved a Nobel Prize
NASA (2017). Dark Energy, Dark Matter. Retrieved from https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

Vera Rubin (2000). Retrieved from http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_rubin.htm

Tags:
dark matter, dark energy, Vera Rubin, gravity, strange universe, Nobel Prize, astronomy, cosmology

Changing the Relationship Between Knowledge and the Child

Robotics combines engineering, engineering design, and technology in ways that, in the words of Marina Bers of the Tufts DevTech group, “connects the T and the E of STEM” and certainly merits a prominent position in STEM education.
Robotics appears to fit into the STEM sequence as a subject for older students. At the Tufts DevTech research group however, robotics has been introduced successfully to pre-Kindergarten children reasoning that because interventions that begin early are, in the long run, less costly and also have greater impacts than those that begin later, robotics should be begun early
Watch this DevTech produced video clip that documents the robotics work of young children.
The spirited dancing of the children is accompanied by dance movements enacted by two-wheeled robots, which while less enthusiastic are more rhythmic and more disciplined than the children’s.
It is notable that although the robots are better at following the music’s rhythms, the robots’ movements were programmed by the same somewhat syncopated children. The video supports the case that young children are quite capable of engaging in robotics in non-trivial ways.
In their work with young children the DevTech research group uses a computer language called CHERP (Creative Hybrid Environment for Robotic Programming). The CHERP language substitutes a set of interlocking wooden blocks for typed in text. Each block is labeled with a graphic representing a command such as FORWARD, BACKWARD, BEGIN, or END. The program is “written” by assembling the commands by arranging the blocks. “The shape of the interlocking blocks and icons creates a physical syntax that prevents the creation of invalid programs and also eliminates the possibility of typographical errors,” notes Marina Bers. Once the blocks have been arranged to create a program for the robot to follow, a scanner on the robot is used to read the program into the robot’s memory.
The behavior of the robot will mimic the program developed by the child-programmer. Because the program is represented by the arrangement of blocks, children are able to make changes to the program by a rearrangement of the blocks. In addition, they can observe one another’s work and to see how other children have solved a particular problem (“how did you make the robot spin five times?”)
In a number of published studies Bers and her colleagues have collected evidence that
Robotics offers young children and teachers a new and exciting way to tangibly interact with traditional early childhood curricular themes. This study demonstrates that it is possible to teach Pre-Kindergarten children to program a robot with developmentally appropriate tools, and, in the process, children may not only learn about technology and engineering, but also practice foundational math, literacy, and arts concepts. While there are many challenges to overcome when implementing robotics in a busy Pre-Kindergarten classroom, our work provides preliminary evidence that teaching young children about and through computer programming and robotics using developmentally appropriate tools may be a powerful tool for educating children across multiple domains.
What is the reason that in addition to robotics and computer programming the “children may not only learn about technology and engineering, but also practice foundational math, literacy, and arts concepts?”
Seymour Papert who was a developer of the computer language LOGO in the 1970s asserted that a programming language like LOGO (or CHERP) changes the relationship between the child and knowledge.
He argued that most school instruction was based on “transmission” or the passing of “knowledge” from its possessor (the teacher) to the receiver (the student). When computers are used in schools, Papert’s argument continued, they are used to “program the child” in the same way that teachers program the child with the “required” knowledge.
The LOGO computer language was designed to enable the child to communicate with the computer. LOGO included a graphical Turtle that the computer’s user could move around on the screen. RIGHT would cause the Turtle to turn 90° to the right. FORWARD 10 would command the Turtle to move 10 paces ahead and so forth.
In the LOGO environment, the traditional relationship between the child and the knowledge was changed.
[t]he child, even at preschool ages, is in control: The child programs the computer. And in teaching the computer how to think, children embark on an exploration about how they themselves think. The experience can be heady: Thinking about thinking turns the child into an epistemologist, an experience not even shared by most adults. (Papert)
In addition, in the usual “teacher as source of knowledge,” model the child is placed in the “got it right/wrong” mode, and worse may not know either what was wrong or how to fix the error.
As Papert notes, when you learn to program, you seldom get it right the first time. “Learning to be a master programmer is learning to become highly skilled at isolating and correcting “bugs,”….
This is also the case with products of the intellect; they are usually neither “right” or “wrong” but are “buggy” works in progress.
If Papert is correct, changing the relationship between the child and knowing is fundamental to learning. Robotics with young children is perhaps a place to begin the change.
Resources:
Epistemologist: one who studies epistemology: the theory of knowledge, especially with regard to its methods, validity, and scope. Epistemology is the investigation of what distinguishes justified belief from opinion.
Marina Umaschi Bers, Safoura Seddighin, and Amanda Sullivan
Ready for Robotics: Bringing Together the T and E of STEM in Early Childhood Teacher Education Jl. of Technology and Teacher Education (2013) 21(3), 355-377

Sullivan, A., Kazakoff, E. R., & Bers, M. U. (2013). The Wheels on the Bot go Round and Round: Robotics Curriculum in Pre-Kindergarten. Journal of Information Technology Education: Innovations in Practice, 12, 203-219. Retrieved from http://www.jite.org/documents/Vol12/JITEv12IIPp203-219Sullivan1257.pdf

Seymour Papert (1980). Mindstorms, Basic Books.