A Problem of Gravity

A Problem of Gravity
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Newton realized that the same force that makes an apple fall to the ground also keeps the moon in its orbit around Earth. Explore this force, called gravity, by focusing on circular orbits. End by analyzing why an orbiting spacecraft has to decrease its kinetic energy in order to speed…
Einstein's Relativity and the Quantum Revolution - Modern Physics for Non-Scientists, 2nd Edition
"It doesn't take an Einstein to understand modern physics," says Professor Wolfson at the outset of these twenty-four lectures on what may be the most important subjects in the universe: relativity and quantum physics. Both have reputations for complexity. But the basic ideas behind them are, in fact, simple and…
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What are the two big ideas of modern physics? How can nonscientists gain a handle on these ideas and the radical changes they bring to our philosophical thinking about the physical world?
Heaven and Earth, Place and Motion
Understanding motion is the key to understanding space and time. Is there a "natural" state of motion? Learn why the ancients gave different answers to this question, and how Copernicus, Kepler, and Galileo laid the foundation for a new approach.
The Clockwork Universe
Isaac Newton was born in 1642, the year that Galileo died. You'll learn how he built on the work of Galileo and Kepler, developing the three laws of motion and the concept of universal gravitation. You'll learn why Newton's laws suggest a universe that runs like a clock.
Let There Be Light!
The study of motion is not all there is to physics. By the 18th century, scientists were delving into the relationship between the two phenomena. Today, electromagnetism is known to be responsible for the chemical interactions of atoms and molecules and all of modern electronic technology.
Speed is Relative to What?
In mechanics (the branch of physics that studies motion), the principle of Galilean relativity holds - meaning that the laws of mechanics are the same for anything in uniform motion. Is the same true for the laws of electromagnetism?
Earth and the Ether - A Crisis in Physics
In the 1880s, Albert Michelson and Edward Morley conducted an experiment to determine the motion of Earth relative to the ether. You'll learn about their experiment, its shocking result, and the resulting theoretical crisis.
Einstein to the Rescue
In 1905 a young Swiss patent clerk named Albert Einstein resolved the crisis that flowed from the Michelson-Morley result. When Einstein discarded the ether concept and asserted that the principle of relativity holds for all of physics, mechanics as well as electromagnetism, he was making a simple claim with almost…
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Why does the simple statement of relativity - that the laws of physics are the same for all observers in uniform motion - lead directly to absurd-seeming situations that violate our commonsense notions of space and time?
Muons and Time-Traveling Twins
As a dramatic example of what relativity implies, you will consider a thought experiment involving a pair of twins, one of whom goes on a journey to the stars and returns to Earth younger than her sister!
Escaping Contradiction - Simultaneity Is Relative
If, as relativity implies, "moving clocks run slow," who's to say which clock is moving?