From “Penn Today” At The University of Pennsylvania : “The Big Bang at 75” 

From “Penn Today”


U Penn bloc

The University of Pennsylvania

Kristina García

Penn theoretical physicist Vijay Balasubramanian discusses the 75th anniversary of the alpha-beta-gamma paper, what we know—and don’t know—about the universe and the ‘very big gaps’ left to discover.

A child stops by an image of the cosmic microwave background at Shanghai Astrology Museum in Shanghai, China on July 18, 2021. (Image: FeatureChina via AP Images)

There was a time before time when the universe was tiny, dense, and hot. In this world, time didn’t even exist. Space didn’t exist. That’s what current theories about the Big Bang posit, says Vijay Balasubramanian, the Cathy and Marc Lasry Professor of Physics. But what does this mean? What did the beginning of the universe look like? “I don’t know, maybe there was a timeless, spaceless soup,” Balasubramanian says. When we try to describe the beginning of everything, “our words fail us,” he says.

Yet, for thousands of years, humans have been trying to do just that. One attempt came 75 years ago from physicists George Gamow and Ralph Alpher. In a paper published on April 1, 1948, Alpher and Gamow imagined the universe starts in a hot, dense state that cools as it expands. After some time, they argued, there should have been a gas of neutrons, protons, electrons, and neutrinos reacting with each other and congealing into atomic nuclei as the universe aged and cooled. As the universe changed, so did the rates of decay and the ratios of protons to neutrons. Alpher and Gamow were able to mathematically calculate how this process might have occurred.

Now known as the alpha-beta-gamma theory, the paper predicted the surprisingly large fraction of helium and hydrogen in the universe. (By weight, hydrogen comprises 74% of nuclear matter, helium 24%, and heavier elements less than 1%.)

The findings of Gamow and Alpher hold up today, Balasubramanian says, part of an increasingly complex picture of matter, time and space. Penn Today spoke with Balasubramanian about the paper, the Big Bang, and the origin of the universe.

When did we first start to think about the Big Bang theory as it is known today?

There’s actually a question of whether it’s even possible to talk about the origin of the universe. But across cultures, humans seem to have an innate drive to try to discuss this sort of question. In India, there was this idea of an infinite cyclic universe that went in gigantic cycles from origin to destruction, origin to destruction, over long lengths of time. The Aztecs had a cosmology that involves gigantic cycles of creation and construction, too. In the Christian West, people had the idea that the horizon of all of time was smaller, a few thousand years, although the Bible doesn’t actually say anything specific about that.

In the 19th century, the first scientific inkling of the age of the world was given by Charles Lyell, a geologist, who wrote about the stratification of rocks. Charles Lyell basically gave Darwin the gift of time. Realizing that the earth was actually much older than a few thousand years gave room for the Theory of Evolution and expanded the horizon in time. That’s a prerequisite for being able to even conceive of the origin of the universe.

Then in 1914, Albert Einstein comes up with the modern theory of gravity [Theory of General Relativity]. This led scientists to try to understand whether you could use this theory to think about the cosmos as a whole. One of the striking things that comes out of that kind of reasoning is that you get forced into a picture where the universe has to be dynamic, basically because gravity is constantly trying to squeeze it together.

To start with, if you look around the sky, it looks reasonably stable and static. It doesn’t look like it’s going anywhere, right? So, people initially tried various ways to construct cosmologies in which they can be kind of stable and static. To do that, you’ve got to poise the universe exactly between an expanding phase and a shrinking phase. You need balance these tendencies. For example, you can give the universal an initial outward push, like a Big Bang, but gravity will try to pull everything back together. How the push and pull compete depends on the amount of kind of energy distributed in the cosmos: regular matter like the stuff that makes stars, pure energy like light, dark matter which does not make stars, and so-called dark energy which can either push the fabric of spacetime apart or try to pull it together. So theoretical physicists tried to figure out whether the laws of gravity, along with these kinds of energy, could explain the apparently static structure of observed universe.

And then a series of astronomical measurements, notably by Edwin Hubble, showed definitively that despite initial appearances, the universe on large scales is not stable and static.

Rather, all the stars and galaxies, as observed now, seem to be spreading apart from each other, as if they are embedded in a space-time fabric that is stretching wider as time passes.


In physical cosmology, cosmic inflation, cosmological inflation is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10^−36 seconds after the conjectured Big Bang singularity to some time between 10^−33 and 10^−32 seconds after the singularity. Following the inflationary period, the universe continued to expand, but at a slower rate. The acceleration of this expansion due to dark energy began after the universe was already over 7.7 billion years old (5.4 billion years ago).

Inflation theory was developed in the late 1970s and early 80s, with notable contributions by several theoretical physicists, including Alexei Starobinsky at Landau Institute for Theoretical Physics, Alan Guth at Cornell University, and Andrei Linde at Lebedev Physical Institute. Alexei Starobinsky, Alan Guth, and Andrei Linde won the 2014 Kavli Prize “for pioneering the theory of cosmic inflation.” It was developed further in the early 1980s. It explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the Universe. Many physicists also believe that inflation explains why the universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed.

The detailed particle physics mechanism responsible for inflation is unknown. The basic inflationary paradigm is accepted by most physicists, as a number of inflation model predictions have been confirmed by observation; however, a substantial minority of scientists dissent from this position. The hypothetical field thought to be responsible for inflation is called the inflaton.

In 2002 three of the original architects of the theory were recognized for their major contributions; physicists Alan Guth of M.I.T., Andrei Linde of Stanford, and Paul Steinhardt of Princeton shared the prestigious Dirac Prize “for development of the concept of inflation in cosmology”. In 2012 Guth and Linde were awarded the Breakthrough Prize in Fundamental Physics for their invention and development of inflationary cosmology.

Alan Guth, from M.I.T., who first proposed Cosmic Inflation.

Alan Guth’s notes:
Alan Guth’s original notes on inflation.

Nobel Prize in Physics for 2011 Expansion of the Universe

4 October 2011

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2011

with one half to

Saul Perlmutter
The Supernova Cosmology Project
The DOE’s Lawrence Berkeley National Laboratory and The University of California-Berkeley,

and the other half jointly to

Brian P. SchmidtThe High-z Supernova Search Team, The Australian National University, Weston Creek, Australia.


Adam G. Riess

The High-z Supernova Search Team,The Johns Hopkins University and The Space Telescope Science Institute, Baltimore, MD.

Written in the stars

“Some say the world will end in fire, some say in ice…” *

What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year’s Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves.

In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called Type 1a supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore, the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

*Robert Frost, Fire and Ice, 1920

This was a revelation, because physicists realized that if the universe is expanding now, if you run the movie backward, it had to be smaller earlier. In fact, some 13 billion years ago all the matter and energy in the universe had to be crammed together at incredible densities that have never been seen on Earth. You can also conclude that the universe would have been a lot hotter in this compressed phase. This is just like what happens if you compress a bicycle pump; he air inside gets hotter because you are cramming more energy into a smaller space. And when things get that hot, the microscopic processes of nuclear physics and even quantum gravity play an important role because of the enormous energies involved.

So, to summarize, the idea of the modern Big Bang comes about because General Relativity makes a prediction: Given the current expansion of the universe, if you run time backwards, you have to start from a very highly compressed phase. At some point, time begins. This didn’t have to be. It could have been very compressed forever, and time could have been infinite. But Einstein’s theory of gravity predicts a beginning for time from which the universe explodes out. That’s the Big Bang.

What are the weaknesses of the Big Bang theory and our current conception of the origin of the universe?

It involves an extrapolation of the things we know and can measure in the lab, along with rather uncertain measurements of the expansion rate of the universe. People like Hubble measured distant stars and galaxies and realized that they look as they’re moving away from us, as an expansion. You put that expansion together with the equations of general relativity. Physics can predict forward in time and can predict backward in time. The equations tell you, given the current state, what the future will look like. But they can also tell you about the past. You know, take your pick.

If you assume Einstein’s theory of relativity and you run the movie backward, time begins some 13 or 14 billion years ago. The question is, should you believe such a wild prediction?

While there are excellent reasons to believe the general theory of relativity—there’s lots of evidence about many things that it gets right—in the history of science, it’s been often the case that a well-tested theory, extrapolated to regimes very far from the region where it was tested, will need corrections of some kind.

We’re extrapolating into regions that have been out of the reach of laboratory experiments to date, for which we do not have direct observational evidence. We should keep in mind that this theory may need corrections, and things like string theory attempt to correct it. Then there are unknown factors that the theory didn’t include, new forms of energy that could prevent the expansion or shrinking or could stabilize the universe.

I’m laying out here the many uncertainties of the theory, but that’s partly because that’s where the opportunities are. If everything was already done, we wouldn’t have to think about it anymore.

Physicists can imagine stuff that makes the world work. That’s what we do for a trade. We imagine stuff that would be necessary for the logical consistency of the world around us. The alpha-beta-gamma paper took Einstein’s theory for granted. They predicted the abundances of the primordial elements, the hydrogen-helium ratio, which turns out to be right. They said, ‘Okay, well, if the universe was very hot, it had to have cooled down over time. So if it cooled down, I’m going put all I know about nuclear physics in the lab to represent the expansion of the universe. As it cools, the primordial soup will freeze out into quarks and gluons and electrons, and those things will freeze out some more, and eventually, when it’s done freezing out, based on what I know about nuclear reaction rates, I predict the following ratio of hydrogen to helium.’ That’s what they did.

The theory then proceeded to predict that you will see a glow in the distant sky as the Big Bang cooled down to a few degrees Kelvin. The discovery of that glow, the cosmic microwave background, in the 1960s, really nailed it.

How do you predict this theory will evolve, or be adjusted, with time?

The hydrogen-helium ratio and the cosmic microwave background are two primary reasons to support the Big Bang theory. Those are certainties that we are seeing now. But what does Hamlet say? ‘There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.’

We keep discovering that our assumptions about the nature of the universe are incorrect or approximate.

The laws of physics are full of laws that turn out not to be laws. They turn out to be approximations. So, Newton’s laws, which we still call Newton’s laws out of respect for Newton, are approximations to the more general laws of general relativity and quantum mechanics. There’s a progression in science where we devise rules and descriptions of nature that work extremely well in some regime, and then, as you push outside the regime, you have to be able to edit them. I try to remain aware that, while the default conclusion is there was a big bang, understood as a singularity in space and time, about 13, 14 billion years ago. There may be escape routes from that conclusion, if our understanding of the laws of nature or something in the data has not been fully correct.

Questioning where the cosmos came from has long been part of human speculation, in philosophy and religion. Ancient peoples drew pictures in caves involving their cosmologies. There’s clearly a human need to talk about origins and causation of the universe. It is kind of amazing and remarkable that we live in a time when there’s a scientific approach to such questions, which we can use with any kind of confidence.

We’re just little people sitting on this irrelevant little planet of a very medium-sized solar system on the edge of a no-account galaxy that is part of a local cluster. We’re sort of just tiny things, right? And yet, we’re claiming to be able to say something about the actual origin of everything. It’s amazing that we have a hope of doing that. But there’s pretty good evidence, that at least in the rough, that this picture is correct: There was a hot, dense space about 13 some billion years ago, and it’s expanded since then.

The core description fits beautifully. The ballpark version seems correct. But the detailed version has gaps, so there is a lot left to do in this process of discovery to understand how the universe is organized and what is in it, Today the most important questions involve dark matter, a form of matter that does not form stars, and dark energy, a form of energy that appears to be forcing the universe apart at an ever faster rate. Together, these substances appear to constitute about 96% of the energy in the universe and have huge consequences for the large-scale organization of the cosmos, its past history, and its future. The race is on to figure out what dark matter and dark energy are.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


Please help promote STEM in your local schools.

Stem Education Coalition

U Penn campus

Academic life at The University of Pennsylvania is unparalleled, with 100 countries and every U.S. state represented in one of the Ivy League’s most diverse student bodies. Consistently ranked among the top 10 universities in the country, Penn enrolls 10,000 undergraduate students and welcomes an additional 10,000 students to our world-renowned graduate and professional schools.

Penn’s award-winning educators and scholars encourage students to pursue inquiry and discovery, follow their passions, and address the world’s most challenging problems through an interdisciplinary approach.

The University of Pennsylvania is a private Ivy League research university in Philadelphia, Pennsylvania. The university claims a founding date of 1740 and is one of the nine colonial colleges chartered prior to the U.S. Declaration of Independence. Benjamin Franklin, Penn’s founder and first president, advocated an educational program that trained leaders in commerce, government, and public service, similar to a modern liberal arts curriculum.

Penn has four undergraduate schools as well as twelve graduate and professional schools. Schools enrolling undergraduates include the College of Arts and Sciences; the School of Engineering and Applied Science; the Wharton School; and the School of Nursing. Penn’s “One University Policy” allows students to enroll in classes in any of Penn’s twelve schools. Among its highly ranked graduate and professional schools are a law school whose first professor wrote the first draft of the United States Constitution, the first school of medicine in North America (Perelman School of Medicine, 1765), and the first collegiate business school (Wharton School, 1881).

Penn is also home to the first “student union” building and organization (Houston Hall, 1896), the first Catholic student club in North America (Newman Center, 1893), the first double-decker college football stadium (Franklin Field, 1924 when second deck was constructed), and Morris Arboretum, the official arboretum of the Commonwealth of Pennsylvania. The first general-purpose electronic computer (ENIAC) was developed at Penn and formally dedicated in 1946. In 2019, the university had an endowment of $14.65 billion, the sixth-largest endowment of all universities in the United States, as well as a research budget of $1.02 billion. The university’s athletics program, the Quakers, fields varsity teams in 33 sports as a member of the NCAA Division I Ivy League conference.

As of 2018, distinguished alumni and/or Trustees include three U.S. Supreme Court justices; 32 U.S. senators; 46 U.S. governors; 163 members of the U.S. House of Representatives; eight signers of the Declaration of Independence and seven signers of the U.S. Constitution (four of whom signed both representing two-thirds of the six people who signed both); 24 members of the Continental Congress; 14 foreign heads of state and two presidents of the United States, including Donald Trump. As of October 2019, 36 Nobel laureates; 80 members of the American Academy of Arts and Sciences; 64 billionaires; 29 Rhodes Scholars; 15 Marshall Scholars and 16 Pulitzer Prize winners have been affiliated with the university.


The University of Pennsylvania considers itself the fourth-oldest institution of higher education in the United States, though this is contested by Princeton University and Columbia University. The university also considers itself as the first university in the United States with both undergraduate and graduate studies.

In 1740, a group of Philadelphians joined together to erect a great preaching hall for the traveling evangelist George Whitefield, who toured the American colonies delivering open-air sermons. The building was designed and built by Edmund Woolley and was the largest building in the city at the time, drawing thousands of people the first time it was preached in. It was initially planned to serve as a charity school as well, but a lack of funds forced plans for the chapel and school to be suspended. According to Franklin’s autobiography, it was in 1743 when he first had the idea to establish an academy, “thinking the Rev. Richard Peters a fit person to superintend such an institution”. However, Peters declined a casual inquiry from Franklin and nothing further was done for another six years. In the fall of 1749, now more eager to create a school to educate future generations, Benjamin Franklin circulated a pamphlet titled Proposals Relating to the Education of Youth in Pensilvania, his vision for what he called a “Public Academy of Philadelphia”. Unlike the other colonial colleges that existed in 1749—Harvard University, William & Mary, Yale Unversity, and The College of New Jersey—Franklin’s new school would not focus merely on education for the clergy. He advocated an innovative concept of higher education, one which would teach both the ornamental knowledge of the arts and the practical skills necessary for making a living and doing public service. The proposed program of study could have become the nation’s first modern liberal arts curriculum, although it was never implemented because Anglican priest William Smith (1727-1803), who became the first provost, and other trustees strongly preferred the traditional curriculum.

Franklin assembled a board of trustees from among the leading citizens of Philadelphia, the first such non-sectarian board in America. At the first meeting of the 24 members of the board of trustees on November 13, 1749, the issue of where to locate the school was a prime concern. Although a lot across Sixth Street from the old Pennsylvania State House (later renamed and famously known since 1776 as “Independence Hall”), was offered without cost by James Logan, its owner, the trustees realized that the building erected in 1740, which was still vacant, would be an even better site. The original sponsors of the dormant building still owed considerable construction debts and asked Franklin’s group to assume their debts and, accordingly, their inactive trusts. On February 1, 1750, the new board took over the building and trusts of the old board. On August 13, 1751, the “Academy of Philadelphia”, using the great hall at 4th and Arch Streets, took in its first secondary students. A charity school also was chartered on July 13, 1753 by the intentions of the original “New Building” donors, although it lasted only a few years. On June 16, 1755, the “College of Philadelphia” was chartered, paving the way for the addition of undergraduate instruction. All three schools shared the same board of trustees and were considered to be part of the same institution. The first commencement exercises were held on May 17, 1757.

The institution of higher learning was known as the College of Philadelphia from 1755 to 1779. In 1779, not trusting then-provost the Reverend William Smith’s “Loyalist” tendencies, the revolutionary State Legislature created a University of the State of Pennsylvania. The result was a schism, with Smith continuing to operate an attenuated version of the College of Philadelphia. In 1791, the legislature issued a new charter, merging the two institutions into a new University of Pennsylvania with twelve men from each institution on the new board of trustees.

Penn has three claims to being the first university in the United States, according to university archives director Mark Frazier Lloyd: the 1765 founding of the first medical school in America made Penn the first institution to offer both “undergraduate” and professional education; the 1779 charter made it the first American institution of higher learning to take the name of “University”; and existing colleges were established as seminaries (although, as detailed earlier, Penn adopted a traditional seminary curriculum as well).

After being located in downtown Philadelphia for more than a century, the campus was moved across the Schuylkill River to property purchased from the Blockley Almshouse in West Philadelphia in 1872, where it has since remained in an area now known as University City. Although Penn began operating as an academy or secondary school in 1751 and obtained its collegiate charter in 1755, it initially designated 1750 as its founding date; this is the year that appears on the first iteration of the university seal. Sometime later in its early history, Penn began to consider 1749 as its founding date and this year was referenced for over a century, including at the centennial celebration in 1849. In 1899, the board of trustees voted to adjust the founding date earlier again, this time to 1740, the date of “the creation of the earliest of the many educational trusts the University has taken upon itself”. The board of trustees voted in response to a three-year campaign by Penn’s General Alumni Society to retroactively revise the university’s founding date to appear older than Princeton University, which had been chartered in 1746.

Research, innovations and discoveries

Penn is classified as an “R1” doctoral university: “Highest research activity.” Its economic impact on the Commonwealth of Pennsylvania for 2015 amounted to $14.3 billion. Penn’s research expenditures in the 2018 fiscal year were $1.442 billion, the fourth largest in the U.S. In fiscal year 2019 Penn received $582.3 million in funding from the National Institutes of Health.

In line with its well-known interdisciplinary tradition, Penn’s research centers often span two or more disciplines. In the 2010–2011 academic year alone, five interdisciplinary research centers were created or substantially expanded; these include the Center for Health-care Financing; the Center for Global Women’s Health at the Nursing School; the $13 million Morris Arboretum’s Horticulture Center; the $15 million Jay H. Baker Retailing Center at Wharton; and the $13 million Translational Research Center at Penn Medicine. With these additions, Penn now counts 165 research centers hosting a research community of over 4,300 faculty and over 1,100 postdoctoral fellows, 5,500 academic support staff and graduate student trainees. To further assist the advancement of interdisciplinary research President Amy Gutmann established the “Penn Integrates Knowledge” title awarded to selected Penn professors “whose research and teaching exemplify the integration of knowledge”. These professors hold endowed professorships and joint appointments between Penn’s schools.

Penn is also among the most prolific producers of doctoral students. With 487 PhDs awarded in 2009, Penn ranks third in the Ivy League, only behind Columbia University and Cornell University (Harvard University did not report data). It also has one of the highest numbers of post-doctoral appointees (933 in number for 2004–2007), ranking third in the Ivy League (behind Harvard and Yale University) and tenth nationally.

In most disciplines Penn professors’ productivity is among the highest in the nation and first in the fields of epidemiology, business, communication studies, comparative literature, languages, information science, criminal justice and criminology, social sciences and sociology. According to the National Research Council nearly three-quarters of Penn’s 41 assessed programs were placed in ranges including the top 10 rankings in their fields, with more than half of these in ranges including the top five rankings in these fields.

Penn’s research tradition has historically been complemented by innovations that shaped higher education. In addition to establishing the first medical school; the first university teaching hospital; the first business school; and the first student union Penn was also the cradle of other significant developments. In 1852, Penn Law was the first law school in the nation to publish a law journal still in existence (then called The American Law Register, now the Penn Law Review, one of the most cited law journals in the world). Under the deanship of William Draper Lewis, the law school was also one of the first schools to emphasize legal teaching by full-time professors instead of practitioners, a system that is still followed today. The Wharton School was home to several pioneering developments in business education. It established the first research center in a business school in 1921 and the first center for entrepreneurship center in 1973 and it regularly introduced novel curricula for which BusinessWeek wrote, “Wharton is on the crest of a wave of reinvention and change in management education”.

Several major scientific discoveries have also taken place at Penn. The university is probably best known as the place where the first general-purpose electronic computer (ENIAC) was born in 1946 at the Moore School of Electrical Engineering.


It was here also where the world’s first spelling and grammar checkers were created, as well as the popular COBOL programming language. Penn can also boast some of the most important discoveries in the field of medicine. The dialysis machine used as an artificial replacement for lost kidney function was conceived and devised out of a pressure cooker by William Inouye while he was still a student at Penn Med; the Rubella and Hepatitis B vaccines were developed at Penn; the discovery of cancer’s link with genes; cognitive therapy; Retin-A (the cream used to treat acne), Resistin; the Philadelphia gene (linked to chronic myelogenous leukemia) and the technology behind PET Scans were all discovered by Penn Med researchers. More recent gene research has led to the discovery of the genes for fragile X syndrome, the most common form of inherited mental retardation; spinal and bulbar muscular atrophy, a disorder marked by progressive muscle wasting; and Charcot–Marie–Tooth disease, a progressive neurodegenerative disease that affects the hands, feet and limbs.

Conductive polymer was also developed at Penn by Alan J. Heeger, Alan MacDiarmid and Hideki Shirakawa, an invention that earned them the Nobel Prize in Chemistry. On faculty since 1965, Ralph L. Brinster developed the scientific basis for in vitro fertilization and the transgenic mouse at Penn and was awarded the National Medal of Science in 2010. The theory of superconductivity was also partly developed at Penn, by then-faculty member John Robert Schrieffer (along with John Bardeen and Leon Cooper). The university has also contributed major advancements in the fields of economics and management. Among the many discoveries are conjoint analysis, widely used as a predictive tool especially in market research; Simon Kuznets’s method of measuring Gross National Product; the Penn effect (the observation that consumer price levels in richer countries are systematically higher than in poorer ones) and the “Wharton Model” developed by Nobel-laureate Lawrence Klein to measure and forecast economic activity. The idea behind Health Maintenance Organizations also belonged to Penn professor Robert Eilers, who put it into practice during then-President Nixon’s health reform in the 1970s.

International partnerships

Students can study abroad for a semester or a year at partner institutions such as the London School of Economics(UK), University of Barcelona [Universitat de Barcelona](ES), Paris Institute of Political Studies [Institut d’études politiques de Paris](FR), University of Queensland(AU), University College London(UK), King’s College London(UK), Hebrew University of Jerusalem(IL) and University of Warwick(UK).