Overview

Course No. 1231

Peer into one of the great mysteries of modern physics—the force of gravity—in this brilliant and insightful course taught by an award-winning professor of physics. It all started with Newton’s apple. Or did it? Gravity controls everything from the falling of an apple to the rising of ocean tides to the motions of the heavens above. If you’ve ever wondered how this most puzzling force works across our entire universe, you will be delighted by this 24-part course that is accessible to any curious person, regardless of your science education.

No other product on the market presents the subject of gravity in as much detail as this course, which will follow the past 400 years of research and experimentation in the field. Your guide is Professor Schumacher, an award-winning educator, prominent theoretical physicist, and protégé of John Archibald Wheeler, the distinguished gravity theorist who first coined the term “black hole.”

Explore the intriguing features of gravity, including: why a hammer does not fall faster than a feather (neglecting air resistance, of course!); how astronauts float in space when they are still within reach of Earth’s gravitational pull; and how gravity shapes the four-dimensional fabric of the universe.

Become immersed in the fascinating study of gravity, experiencing the scientific breakthroughs alongside the great minds of physics: Galileo, Newton, Cavendish, Einstein, Hubble, Hawking, and more. Examine a recent discovery: that the expansion of our universe is accelerating due to an as-yet-unexplained cosmic antigravity known as dark energy. Delve into the Holy Grail of contemporary physics: the search for a theory that encompasses both gravity, which extends its reach across the cosmos, and quantum mechanics, which governs events at the smallest possible scale.

In Black Holes, Tides, and Curved Spacetime, you will travel to the very edges of modern physics to explore several revolutionary theories and discover that physics is just as exciting today as it was when Newton sat by that fateful apple tree.

Course Structure

01: The Strangest Force

Begin your exploration of gravity with Isaac Newton and the famous story of the apple. Why was it such a breakthrough to connect a falling apple with the faraway moon? Review the essential characteristics of gravity and learn why small asteroids and large planets have such different shapes.

Duration: 33 min

02: Free Fall and Inertia

Review three great discoveries by the “grandfather” of gravity research, Galileo Galilei. His most famous experiment may never have happened, but his principle of inertia, law of free fall, and principle of relativity are the basis for everything that comes later in the science of gravity—including key breakthroughs by Einstein.

Duration: 29 min

03: Revolution in the Heavens

Drawing on ideas and observations of Nicolaus Copernicus and Tycho Brahe, Johannes Kepler achieved a great insight about gravity by discovering three laws of planetary motion, relating to the mathematics of orbits. The cause of planetary motion, he determined, must lie in the sun.

Duration: 28 min

04: Universal Gravitation

See how Newton was able to finish Kepler’s revolution by formulating the law of universal gravitation, which says that every object exerts an attractive force on every other object. Also explore Newton’s related discovery of the three laws of motion, which underlie the science of mechanics.

Duration: 28 min

05: The Art of Experiment

Learn how distances in the solar system were first determined. Then chart Henry Cavendish’s historic experiment that found the value of Newton’s gravitational constant. Cavendish’s work allows almost everything in the universe to be weighed. Then see a confirmation of the equivalence principle, which says that gravitational and inertial mass are identical.

Duration: 30 min

06: Escape Velocity, Energy, and Rotation

Begin the first of several lectures that dig deeper into Newton’s laws than Newton himself was able to go. In this lecture, apply the key concepts of energy and angular momentum to study how gravity affects motion. As an example, use simple algebra to calculate the escape velocity from Earth.

Duration: 29 min

07: Stars in Their Courses—Orbital Mechanics

Newton was the first to realize that objects could, in theory, be sent into orbit around Earth. Explore how this works in practice, using the ideas of energy and angular momentum to study how satellites, moons, planets, and stars move through space.

Duration: 29 min

08: What Are Tides? Earth and Beyond

Trace the origin of tides to the simple fact that gravity varies from point to point in space. This leads not just to the rise and fall of the ocean, but to the gradual slowing of Earth’s rotation, Saturn’s spectacular ring system, volcanoes on Jupiter’s moon Io, and many other phenomena.

Duration: 30 min

09: Nudge—Perturbations of Orbits

For the next three lectures, study the effects of gravity on the motions of more than two bodies. Here, see how even very small orbital changes—small perturbations—are significant. Such effects have revealed the presence of unknown planets, both in our own solar system and around other stars.

Duration: 28 min

10: Resonance—Surprises in the Intricate Dance

Resonance happens whenever a small periodic force produces a large effect on a periodic motion—for example, when you push a child on a swing. Learn how resonance due to gravitational interactions between three bodies can lead to amazing phenomena with planets, asteroids, and rings of planets.

Duration: 29 min

11: The Million-Body Problem

Consider the problem of gravitational interactions between millions of bodies, such as the countless stars in a galaxy. Amazingly, mathematics can reveal useful information even in these complicated cases. Discover how the analysis of the motions of galaxies led to the prediction of dark matter.

Duration: 32 min

12: The Billion-Year Battle

Explore the physics of stars, which are balls of gas in a billion-year battle between the inward pull of gravity and the outward pressure produced by nuclear fusion. Follow this story to its ultimate finish—the triumph of gravity in massive stars that end their lives as black holes.

Duration: 30 min

13: From Forces to Fields

For the rest of the course, focus on the revolutionary view of gravitation launched by Albert Einstein. Review new ideas about fields that allowed physics to extend beyond Newtonian mechanics. Then see how Einstein modified Newton’s laws and created the special theory of relativity.

Duration: 31 min

14: The Falling Laboratory

Einstein focused on gravity in his general theory of relativity. Hear about his “happiest thought”—the realization that a man in free fall perceives gravity as zero. This simple insight resolved a mystery going all the way back to Newton and led Einstein to the startling discovery that gravity affects light and time.

Duration: 31 min

15: Spacetime in Zero Gravity

In an influential interpretation of relativity, Einstein’s former mathematics professor Hermann Minkowski reformulated the theory in terms of four-dimensional geometry, which he called spacetime. Learn how to plot events in this coordinate system in cases where gravity is zero.

Duration: 29 min

16: Spacetime Tells Matter How to Move

See how gravity affects Minkowski’s spacetime geometry, discovering that motion in a gravitational field follows the straightest path in curved spacetime. The curvature in spacetime is not caused by gravity; it is gravity. This startling idea is the essence of Einstein’s general theory of relativity.

Duration: 31 min

17: Matter Tells Spacetime How to Curve

The curvature of spacetime depends upon matter—and tidal effects. In this lecture, see how ordinary tidal effects reveal a simplified form of Einstein’s greatest discovery: the equation governing the curvature of spacetime by matter.

Duration: 30 min

18: Light in Curved Spacetime

See how Einstein’s general theory of relativity predicts the bending of light in a gravitational field, famously confirmed in 1919 by the British scientist Arthur Eddington. Learn how this phenomenon creates natural gravitational lenses—and how the bending of light reveals invisible matter in deep space.

Duration: 30 min

19: Gravitomagnetism and Gravitational Waves

The general theory of relativity predicts new phenomena of gravity analogous to those of electromagnetism. Discover how ultra-sensitive experiments have detected the gravitomagnetism of the Earth, and follow the search for elusive gravitational waves that travel through space.

Duration: 31 min

20: Gravity’s Horizon—Anatomy of a Black Hole

Plunge into the subject of black holes, which are massive objects that have collapsed completely under their own gravity. Learn how black holes distort spacetime and explore the supermassive black holes that lie at the hearts of galaxies. Then ask: Are there such things as micro-black holes?

Duration: 33 min

21: Which Universe Is Ours?

Investigate what Einstein called his “greatest mistake”—his rejection of his own theory’s prediction that spacetime should be dynamic and evolving. Chart the work of a group of scientists, including Alexander Friedman, Georges Lemaître, and Edwin Hubble, who advanced the realization that our universe is expanding from an apparent big bang.

Duration: 30 min

22: Cosmic Antigravity—Inflation and Dark Energy

Using everything you’ve learned about gravity, investigate cosmic antigravity, starting with cosmic inflation, a phenomenon that exponentially increased the size of the universe during the big bang. Then, learn why dark matter cannot be made of ordinary protons and neutrons, and explore the recent discovery that the expansion of the universe is accelerating, powered by a mysterious dark energy.

Duration: 32 min

23: The Force of Creation

Use a black hole to test the laws of thermodynamics, taking a deeper look at the capacity of gravity to pull matter together and increase entropy at the same time. Probe Stephen Hawking’s most surprising discovery, and then learn that the same force that pulls the apple down and steers the stars in their courses is also nature’s ultimate source of order and complexity.

Duration: 29 min

24: The Next Revolution

Survey the greatest unsolved problem in theoretical physics: the search for a quantum theory of gravity. Examine string theory, loop quantum gravity, and also entropic gravity, which suggests a revolutionary link with thermodynamics. Close the course with a deepened appreciation for the connection between everyday features of gravity and the most exciting questions in contemporary physics and cosmology.

Duration: 32 min