![Physics of History]()
TTC Video – Physics of History
Professor David J. Helfand | Packed size: 1.62 GB
Columbia University, Ph.D., University of Massachusetts
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.
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.
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.
24 Lectures: 30 minutes / lecture
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.
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.
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.
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.
5. Radioactivity??é¼?C¥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.
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.
7. Watching Plaster Dry??é¼?C¥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.
8. We Are What We Eat??é¼?C¥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.
9. A Plant Is What It Eats??é¼?C¥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.
10. Tree Rings??é¼?C¥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.
11. Ice Cores??é¼?C¥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.
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.
13. A Bad Day in June??é¼?C¥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.
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.
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.
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.
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.
18. Atoms Are Star Stuff??é¼?C¥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.”
19. The Lives of Big Stars??é¼?C¥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.
20. Relativity??é¼?C¥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.
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.
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.
23. The Limits of Vision??é¼?C¥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.
24. The First Few Minutes??é¼?C¥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.
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