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Physics of History

Physics of History

Professor David J. Helfand Ph.D.
Columbia University
Course No.  1252
Course No.  1252
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Course Overview

About This Course

24 lectures  |  30 minutes per lecture

In April 1991, two Alpine hikers stumbled across the well-preserved body of a Copper Age hunter half-buried in a glacier on the border between Italy and Austria. This accidental discovery, nicknamed Ötzi the Iceman, possessed a trove of invaluable information about the origins of prehistoric people. Yet while standard archaeological techniques revealed many interesting aspects of Ötzi's life—including his diet and his dress—it was only through the use of physics that more microscopic clues were uncovered; clues that, decades earlier, might have remained hidden. The strontium-to-lead ratios in Ötzi's teeth matched the ratios found in the Eisack Valley, northeast of present-day Bolzano, Italy, suggesting that was where he spent his childhood. Varying ratios of oxygen 18 to oxygen 16 in Ötzi's bones indicated that he spent much of his later life at higher altitudes. And the presence of excess copper and arsenic in Ötzi's hair suggested that he played an active role in copper smelting.

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In April 1991, two Alpine hikers stumbled across the well-preserved body of a Copper Age hunter half-buried in a glacier on the border between Italy and Austria. This accidental discovery, nicknamed Ötzi the Iceman, possessed a trove of invaluable information about the origins of prehistoric people. Yet while standard archaeological techniques revealed many interesting aspects of Ötzi's life—including his diet and his dress—it was only through the use of physics that more microscopic clues were uncovered; clues that, decades earlier, might have remained hidden. The strontium-to-lead ratios in Ötzi's teeth matched the ratios found in the Eisack Valley, northeast of present-day Bolzano, Italy, suggesting that was where he spent his childhood. Varying ratios of oxygen 18 to oxygen 16 in Ötzi's bones indicated that he spent much of his later life at higher altitudes. And the presence of excess copper and arsenic in Ötzi's hair suggested that he played an active role in copper smelting.

This is but one of the many examples of how the laws of physics can give us intimate details about history—details that are impossible to find through mere observation. In fact, the history of the entire universe and all it contains is written in the particular arrangements of the fundamental particles that constitute all matter. With recent developments in technology, scientists can now use everything they know about atoms—their origins, structure, and behavior—to uncover the truth about historical mysteries in archaeology, chemistry, geology, astronomy, and even art.

With this unprecedented access to times far earlier than those recorded by historians, scientists can now explore the rise and fall of preliterate societies, the history of the Earth's changing climate, and even the origins of the solar system 4.5 billion years ago. Using this knowledge, they can finally develop a comprehensive, stable timeline that encompasses all of history, from the beginning of time to today—all by "reading" the history of a bone, a piece of wood, the mortar in a building, a neutrino from the sun, and more.

The Physics of History, taught by award-winning Professor David J. Helfand of Columbia University, gives you the background to understand how scientists know what they do about the past. These 24 richly illustrated lectures cover an astonishing range of cases in which physics has helped to redefine history—in astronomy, archaeology, geology, climatology, art history, and other fields.

An Amazing Voyage

Your amazing voyage begins with five lectures on elementary atomic and nuclear physics. Professor Helfand then builds on this background with a series of lectures dealing with mysteries on Earth. He rounds out the course with a group of lectures that take on the problems of the cosmos, including the radical adjustment in our view of time and space required by Einstein's theory of relativity.

Immensely rewarding and enlightening, The Physics of History enhances your appreciation of both science and history by addressing questions such as these:

  • How did corn spread across the New World? Knowing the photosynthetic pathway used by corn, scientists can analyze Native American bones and chart the spread of corn cultivation, from its origin in the highlands of Mexico to New England over the course of 7,000 years.
  • When did the extinction of the dinosaurs occur? Scientists have been able to narrow down June as the month when, 64.5 million years ago, an asteroid slammed into the Yucatan peninsula and wiped out at least 50% of all living species on Earth—all from a frozen water lily leaf preserved at a particular point in its life cycle.
  • Which is older, Stonehenge or the pyramids? Archaeologists long considered Stonehenge to be much younger than the Egyptian pyramids. But in the 1960s, carbon-14 dating showed Stonehenge to be much older, predating the pyramids by hundreds of years.
  • How old is the Earth? Analysis of a pair of rare atoms in meteorites shows that the Earth and the rest of the solar system formed 4.56 billion years ago. Clues in atoms also tell scientists about the early history of the Earth, where the moon came from, and that the explosion of a nearby star may have triggered the formation of the sun and planets.

Tools of the Trade

In The Physics of History, you explore the resources that scientists use to investigate the past, the most important of which is radioactivity. Radioactive isotopes decay at predictable rates, from fractions of a second to billions of years, making them very precise clocks. Isotopes also serve as tracers for the circumstances that produced them, such as the explosion of a star.

One of the best-known radioactive isotopes is carbon-14. With a half-life of 5,730 years (the time required for half of the atoms to decay), it is ideal for dating carbon-containing material relating to human history. For example, the carbonate mortar in an unusual tower in Rhode Island turned out to be only 300 years old, showing that it was not built by the Vikings before Columbus, as some people believed.

You also examine other tools, many of which are used in combination:

  • Tree rings: These annual growth layers have been compiled into a continuous record extending back 12,000 years, allowing wood to be dated from distinctive patterns of ring widths, which also contain information on the weather conditions for any given year.
  • Ice cores: With ice sheets more than two miles thick, Greenland and Antarctica preserve the successive snowfalls of 750,000 years. Trapped in these layers are atmospheric gases, sea salt, and dust, which serve as time capsules of long-ago events.
  • Ocean sediments: Extending even further back than tree rings or ice cores, ocean sediments represent a continuous 5-million-year record, shedding light on climate change and continental drift.

Drama, Mystery, and Delight

One of the pleasures of The Physics of History is watching Professor Helfand tackle each of his case histories like a detective at a crime scene, using an arsenal of techniques to tease vivid stories from the slimmest of evidence. The drama and delight of his teaching style have made him a popular lecturer at Columbia University, where he was honored with a Presidential Teaching Award and a Great Teacher Award from the Society of Columbia Graduates.

Among the many mysteries you solve with him are these:

  • How to use atoms in a work of art to show whether it is a fake
  • Why a simple ratio of isotopes can signal if orange juice has been adulterated with corn syrup
  • What created the left-handed asymmetry in amino acids found in all forms of life on Earth, as well as in meteorites

The Physics of History is an insightful feast that will undoubtedly satisfy your curiosity about some of the most profound discoveries in the history of humanity—and the universe. With the wealth of information contained in this course, the next time you hear about a breakthrough scientific finding in the news, you'll be better equipped to answer the question: How did they do that?

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24 Lectures
  • 1
    The Vast Reaches of Time and Space
    Atoms tell the story of events that are inaccessible to the methods of traditional historians. Begin your study of this hidden history by investigating simple analogies that allow you to comprehend the vast realms of time and space that are covered in the course. x
  • 2
    Fundamentally, What's the World Made Of?
    Everything is made of atoms, but what are atoms made of? In this lecture, peel back their layers, discovering that the atomic nucleus can serve as an invaluable clock and that electrons behave in distinctive ways that identify atoms across millions of light-years of space. x
  • 3
    Energy in the Atomic World
    Investigate the forces through which atoms and their particles interact. These interactions are manifested as energy. As an example, you tally the human requirement for energy at the atomic level, coming up with an average of about 2,000 calories per person, per day. x
  • 4
    The Atomic Basis of the Senses
    Professor Helfand shows how your sensations are mediated by a cascade of atomic interactions, starting in the external world and ending in the brain. For all their power, the senses miss a great deal; for instance, there's a good evolutionary reason why your nose can't detect carbon monoxide. x
  • 5
    Radioactivity—Nature's Imperturbable Clock
    It is impossible to say when something happened without a clock to measure the passage of time. Learn that for a wide range of time scales, nature provides imperturbable clocks in the radioactive decay of different isotopes. x
  • 6
    From Detecting Forgeries to the First Art
    Discover that by bombarding a painting with neutrons, it's possible to determine the pigments employed. If you find modern pigments that were not in use when the work was supposedly created, then you know something is amiss. Carbon-14 dating is another technique for unmasking forgeries. x
  • 7
    Watching Plaster Dry—And Dating It
    Carbon-14 decay is ideal for dating material that was once alive, or indeed for any chemical process that involves carbon. In this lecture, learn how this technique helped debunk a story about the Vikings in Rhode Island. x
  • 8
    We Are What We Eat—The History of Diet
    Since every atom in your body comes from consuming and inhaling atoms, a detailed analysis of your atomic makeup says quite a lot about you. Investigate the ancient Iceman, whose probable birthplace and subsequent wanderings are revealed in the atoms of his bones and hair. x
  • 9
    A Plant Is What It Eats—Tracing Agriculture
    Investigate three separate biochemical pathways for photosynthesis. Thanks to the pathway that evolved for drought tolerance in plants such as corn, scientists are able to chart the ancient spread of corn cultivation from Mexico to New England over the course of 7,000 years. x
  • 10
    Tree Rings—Seasons of the Past 12,000 Years
    Leonardo da Vinci pioneered the idea of reading past seasons in tree rings. However, the field did not take off until the 20th century. This lecture shows how isotopic analysis of tree rings yields records of temperature and humidity, year by year, for a dozen millennia. x
  • 11
    Ice Cores—Climate Records for 800 Millennia
    Remarkably, an ice core provides all the records of a modern weather station, extending over a time interval five times longer than humans have inhabited the Earth. Study past periods of climate change and the lessons they hold for today's warming planet. x
  • 12
    Ocean Sediments Reveal 5 Million Years
    Explore another archive of information: ocean sediments. As sea plants and animals die and sink to the ocean floor, their remains preserve the isotopic ratios of oxygen and hydrogen present when they were alive, providing a continuous record of sea-surface temperatures over millions of years. x
  • 13
    A Bad Day in June—Death of the Dinosaurs
    One of the most celebrated incidents of prehistory is the asteroid impact that led to the extinction of the dinosaurs. Follow the trail of evidence that helped investigators deduce the time, place, and outcome of this Earth-shaking event, which paved the way for the rise of mammals. x
  • 14
    The Origin and Early History of Life
    Life emerged on Earth from commonplace interstellar chemicals. Look at the early history of life, including the peculiar fact that the amino acids on Earth and in meteorites are left-handed, a situation that may relate to the violent effects of a nearby neutron star. x
  • 15
    The History of Earth's Atmosphere
    Clues from other planets and from the geological record allow scientists to reconstruct the long-term history of Earth's atmosphere and the dramatic differences in climate over time. Learn why dragonflies with 30-inch wingspans were possible in the distant past but not today. x
  • 16
    The Age of the Solar System
    In this lecture, look at historical estimates for the age of Earth and the solar system. Thanks to a pair of rare atoms, we now know the answer: 4.56 billion years. Analysis of moon rocks adds further details about cataclysms that shaped the early Earth. x
  • 17
    What Happened before the Sun Was Born?
    Here, investigate how an isotope found in meteorites suggests that a massive star blew up in the region that later saw the formation of the solar system. This blast may have provided the push that a localized cloud of gas needed to collapse and form the sun. x
  • 18
    Atoms Are Star Stuff—Cooking Up Carbon
    What is a star? Professor Helfand makes sense of the astronomer's definition: "A star is a plasma, gravitationally bound, supported by thermal pressure in hydrostatic equilibrium (usually), emitting blackbody radiation, and powered by nuclear fusion." x
  • 19
    The Lives of Big Stars—Cooking Up Big Atoms
    All that you eat, except for hydrogen atoms, was cooked for you inside stars. Explore why this is so and investigate the life cycles of stars of different masses and how all the elements from carbon to uranium are forged inside them. x
  • 20
    Relativity—Space and Time Become Spacetime
    Moving beyond the Milky Way galaxy, examine the surprising relationship between space and time discovered by Einstein. An understanding of his theory of relativity is crucial for the course's final quest to explain the origin of matter at the beginning of time. x
  • 21
    (Almost) Everything Is Relative
    The finite speed of light and the constancy of this speed for all observers is the basis for Einstein's special theory of relativity. Explore some consequences of the theory, such as the time dilation effect, which makes two clocks run at different rates depending on their relative motion. x
  • 22
    Matter Vanishes; Light Speed Is Breached?
    Relativity does not forbid faster-than-light travel, however, the strange consequences of such a phenomenon have never been observed. Discover how, in a world with theoretical faster-than-light particles, an effect could precede its cause in time. Also, learn about the equivalence of mass and energy. x
  • 23
    The Limits of Vision—13.7 Billion Years Ago
    Continuing your journey to the beginning of time, look back to the origin of the cosmic microwave background, a universal glow that permeates all of space and that records the state of the universe just 380,000 years after the big bang. x
  • 24
    The First Few Minutes—Where It All Began
    Arrive at the events that gave rise to matter itself. Professor Helfand likens this early period to an extreme form of musical chairs, when fundamental particles "froze out" at different times. End the course by following the history of a single quark, from its birth to its surprising fate today. x

Lecture Titles

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David J. Helfand
Ph.D. David J. Helfand
Columbia University
Dr. David J. Helfand is Professor of Astronomy at Columbia University, where he has taught for over 30 years. He was an undergraduate at Amherst College and earned his Ph.D. in Astronomy from the University of Massachusetts, Amherst, where he worked under Professor Joseph Taylor, the 1993 Nobel Laureate in Physics. Professor Helfand's research has covered many areas of modern astrophysics, including radio, optical, and X-ray observations of celestial sources ranging from nearby stars to the most distant quasars. He is involved in a major project to survey our galaxy with a sensitivity and resolution a hundred times greater than what is currently available. The goal is to obtain a complete picture of stellar birth and death in the Milky Way. Professor Helfand received a Presidential Teaching Award and a Great Teacher Award from the Society of Columbia Graduates. At Columbia, he realized a long-term goal to introduce a science course into the university's famed Core Curriculum. In addition to his teaching duties, Professor Helfand lectures extensively on science to the general public, has appeared on the Discovery Channel's Science News, and is featured in the National Geographic Channel's Known Universe.
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Reviews

Rated 4.5 out of 5 by 41 reviewers.
Rated 5 out of 5 by When Did it Happen? How do you Know? When Did it Happen? How do you Know? Dr. Helfand is good. And the course is fun, and you walk away more comfortable in the Universe. As much as it sounds like it, this isn't a history course. An unexamined glance at the title might convey the idea that this does deal with history, the professor early on straightens out that misconception. It is a physics course, but it seeks to answer one of the critical questions of history, “When did it happen?” Dinosaurs, stars, paintings, plaster, ceramics, trees, people, everything is identified with some point in time, the time of creation or the time of death. Things as big as the universe, and as infinitesimal as muons, Dr. Helfand relates how we have pinned dates and durations on all of them. Dr. Helfand does a hard thing. He teaches his course to non-scientists. To those of us who have had to do this, that he is successful proves the depth of his knowledge of the topics. He must be able to dig down into the mathematics and convert it to word pictures that don't depend on involved mathematical relationships. He does this hard thing, and he does it extremely well. With a technical audience, the speaker is able to point to a questionable step in the process and say, “It obviously follows that...” and point to the next step. Few members of the audience will have the courage to admit their own lack of immediate comprehension. When the audience doesn't have the background, the speaker doesn't have this cover. Dr. Helfand doesn't need it. His explanations of isotope ratios as clocks is easy to follow, from the creation of the isotopes down to the total conversion to the daughter isotopes. The technical exposition is interleaved with a narrative history of the field that draws you in. Radiocarbon dating, used to date things as long ago as 50,000 years in the past, uses techniques that are younger than I am. The great thing about it is that I understand it, at least well enough to seek more information when I want it. . September 9, 2014
Rated 5 out of 5 by Wonderfully Illuminating As one whose degrees are in history and political science, my experience with science courses is relatively limited. Despite this handicap, I found Dr. Helfand's course to be very enlightening and stimulating. He is a very pleasant and engaging presenter, and appropriately uses visual aids in explaining the intricacies of atomic interactions. While some may find (as I did) that the first few lectures -- I learned more about the behavior of atoms (within and without) than I had ever wished to know before -- they are nonetheless interesting and quite necessary in order to appreciate the richness of subsequent lectures. This course is a wonderful complement to the many fine historical and geological courses offered by the Teaching Company, but it also supplements them beautifully. By the completion of this course, I was more in awe of this marvelous universe -- inside, around, and outside us -- than ever before. The closer we peer, the more we understand, and the more we marvel at the beauty and mystery of the universe. Another home run by the good folks at the Teaching Company! August 22, 2014
Rated 4 out of 5 by Demanding But Informative I don't want to piggy back on what previous reviewers have wrote about this course, but I can't but help emphasize that this is not a 'History of Physics' but a PHYSICS course that demands the viewer's attention and assumes the student has a least a passing knowledge of physics, chemistry, and astronomy. Professor Helfand certainly does because he does not take the time to explain the principles and theories behind the lectures. My only complaint about the course is that, while it is not a history course, I wish the professor had arranged the course materials in more of a chronological (historical) order. November 4, 2013
Rated 5 out of 5 by Difficult but amazing DVD review. ©2013. Guidebook 146 pages. OK. I’ll confess. This was the hardest TGC course I’ve seen. I’m terrible at physics and chemistry, so I actually had to watch the first disc 4-5 times until it clicked. I’d try, then put it on the bookcase; try again, put it back and wait a while. Finally, on the last viewing, everything started clicking and it became absorbing and I blew through the whole course. I found it fascinating, wonderful, and amazing. At the end I just felt astonished by the progress humans have made to uncover what many believe to be the mysterious workings of the universe. I can’t speak more highly about the course and Professor Helfand. The foundation lectures are essential to understanding the rest of the course. They’re about energy, atoms, radioactivity, etc. No problem with the professor or his delivery. Failure was on my own poor background on physics and chemistry. The Resources were excellent; I found myself constantly reviewing the glossary. There’s more math than in other courses; it wasn’t terribly difficult, as the professor goes through it step by step. Just keep in mind that this is a SCIENCE course, not a HISTORY course. I highly recommend this course and it’s a great supplement to Big History. October 10, 2013
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