The Evidence for Modern Physics: How We Know What We Know

Overview

Course No. 60000

An award-winning teacher and philosopher makes sense of our strange universe. Philosophers have long puzzled over the nature of space, time, and matter. These inquiries led to the flowering of physics with the Scientific Revolution in the 17th century. Since then, the spectacular success of modern physics might appear to have made philosophy irrelevant. But new theories have created a new range of philosophical concerns: What is the shape of space? Is time travel possible? Is there a grand unified theory that unites all of physics?

Treating these and other puzzles with an entertaining and accessible approach, The Great Questions of Philosophy and Physics guides you through the concepts, theories, and speculations that underlie our understanding of reality. In 12 stimulating, half-hour lectures, award-winning teacher and philosopher Steven Gimbel of Gettysburg College covers the fundamental ideas of modern physics, highlighting the role of philosophy in setting ground rules, interpreting the results, and posing new questions.

Professor Gimbel describes the grand synthesis that Isaac Newton achieved with his universal theory of gravitation and its picture of absolute space and time. Then, you see how Albert Einstein’s theory of relativity, combined with quantum theory, overthrew the Newtonian paradigm, posing a host of philosophical puzzles. Among them is Erwin Schrödinger’s famous thought experiment about a cat that is simultaneously dead and alive according to the standard interpretation of quantum mechanics. You survey philosophical attempts to escape from this and other paradoxes, and you also investigate the role of mathematics in physical theories. Does its extraordinary success imply that the world is a mathematical system?

You close by exploring theological arguments that invoke the discoveries of physics to posit a creator God. As with other theories covered in the course, you carefully weigh both sides using scientific evidence and the tools of philosophy.

Video Lectures

01: Does Physics Make Philosophy Superfluous?

Trace the growth of physics from philosophy, as questions about the nature of reality got rigorous answers starting in the Scientific Revolution. Then see how the philosophy of physics was energized by a movement called logical positivism in the early 20th century in response to Einstein’s theory of relativity. Though logical positivism failed, it spurred new philosophical ideas and approaches.

Duration: 30 min

02: Why Mathematics Works So Well with Physics

Physics is a mathematical science. But why should manipulating numbers give insight into how the world works? This question was famously posed by physicist Eugene Wigner in his 1960 paper, “The Unreasonable Effectiveness of Mathematics in the Natural Sciences.” Explore proposed answers, including Max Tegmark’s assertion that the world is, in fact, a mathematical system.

Duration: 35 min

03: Can Physics Explain Reality?

If the point of physics is to explain reality, then what counts as an explanation? Starting here, Professor Gimbel goes deeper to probe what makes some explanations scientific and whether physics actually explains anything. Along the way, he explores Bertrand Russell’s rejection of the notion of cause, Carl Hempel’s account of explanation, and Nancy Cartwright’s skepticism about scientific truth.

Duration: 35 min

04: The Reality of Einstein’s Space

What’s left when you take all the matter and energy out of space? Either something or nothing. Newton believed the former; his rival, Leibniz, believed the latter. Assess arguments for both views, and then see how Einstein was influenced by Leibniz’s relational picture of space to invent his special theory of relativity. Einstein’s further work on relativity led him to a startlingly new conception of space.

Duration: 33 min

05: The Nature of Einstein’s Time

Consider the weirdness of time: The laws of physics are time reversible, but we never see time running backwards. Theorists have proposed that the direction of time is connected to the order of the early universe and even that time is an illusion. See how Einstein deepened the mystery with his theory of relativity, which predicts time dilation and the surprising possibility of time travel.

Duration: 29 min

06: The Beginning of Time

Professor Gimbel continues his exploration of time by winding back the clock. Was there a beginning to time? Einstein’s initial equations of general relativity predicted a dynamic universe, one that might have expanded from an initial moment. Einstein discarded this idea, but since then evidence has mounted for a “Big Bang.” Is it sensible to ask what caused the Big Bang and what happened before?

Duration: 27 min

07: Are Atoms Real?

Compare proof for the reality of atoms with evidence for the existence of Santa Claus. Both are problematic hypotheses! Trace the history of atomic theory and the philosophical resistance to it. End with Bas van Fraassen’s idea of “constructive empiricism,” which holds that successful theories ought only to be empirically adequate since we can never know with certainty what is real.

Duration: 31 min

08: Quantum States: Neither True nor False?

Enter the quantum world, where traditional philosophical logic breaks down. First, explore the roots of quantum theory and how scientists gradually uncovered its surpassing strangeness. Clear up the meaning of the Heisenberg uncertainty principle, which is a metaphysical claim, not an epistemological one. Finally, delve into John von Neumann’s revolutionary quantum logic, working out an example.

Duration: 29 min

09: Waves, Particles, and Quantum Entanglement

Quantum mechanics rests on an apparent category mistake: Light can’t be both a wave and a particle, yet that’s what theory and experiments show. Analyze this puzzle from the realist and empiricist points of view. Then explore philosopher Arthur Fine’s “natural ontological attitude,” which reconciles realism and antirealism by demonstrating how they rely on different conceptions of truth.

Duration: 30 min

10: Wanted Dead and Alive: Schrödinger’s Cat

The most famous paradox of quantum theory is the thought experiment showing that a cat under certain experimental conditions must be both dead and alive. Explore four proposed solutions to this conundrum, known as the measurement problem: the hidden-variable view, the Copenhagen interpretation, the idea that the human mind “collapses” a quantum state, and the many-worlds interpretation.

Duration: 29 min

11: The Dream of Grand Unification

After the dust settled from the quantum revolution, physics was left with two fundamental theories: the standard model of particle physics for quantum phenomena and general relativity for gravitational interactions. Follow the quest for a grand unified theory that incorporates both. Armed with Karl Popper’s demarcation criteria, see how unifying ideas such as string theory fall short.

Duration: 31 min

12: The Physics of God

The laws of physics have been invoked on both sides of the debate over the existence of God. Professor Gimbel closes the course by tracing the history of this dispute, from Newton’s belief in a Creator to today’s discussion of the “fine-tuning” of nature’s constants and whether God is responsible. Such big questions in physics inevitably bring us back to the roots of physics: philosophy.

Duration: 29 min