The Grand Design by Stephen Hawking and Leonard Mlodinow.

This podcast is based on the book “The Grand Design” by Stephen Hawking and Leonard Mlodinow. The book explores the foundations of the universe, questioning its origin and functioning through the laws of physics, including M-theory. It examines the evolution of scientific understanding of natural laws from antiquity to modern physics, addressing concepts such as determinism and model-dependent realism. Finally, it offers a reflection on the nature of reality and the existence of multiple universes.

The sources mention several theories or models that have been proposed to explain the universe:

* Theory of the Four Elements: This theory, developed by Aristotle, stated that the world was made up of four elements: earth, air, fire, and water. Although elegant, this theory failed to make accurate predictions consistent with observations.

* Ptolemaic Model: This model, introduced around 150 CE, placed the Earth at the center of the universe, with the Sun, Moon, and stars orbiting it in complex orbits involving epicycles. This model seemed natural because we do not feel the Earth moving beneath our feet. It was adopted by the Catholic Church and remained the official doctrine for fourteen hundred years.

* Copernican Model: Proposed in 1543, this model placed the Sun at the center and the planets revolving around it in circular orbits. Although this idea was not new, its revival was met with heated resistance, as it was seen as contradicting the Bible. The Copernican model eventually led to a heated debate over whether the Earth was at rest, culminating in Galileo’s trial for heresy in 1633. The real advantage of the Copernican system is that the equations of motion are much simpler in the frame of reference where the Sun is at rest.

* Luminiferous Aether Model: To explain the constant speed of light, it was assumed that there was a medium, called the aether, through which electromagnetic waves propagated. The aether would provide an absolute frame of rest and a way to define absolute motion. However, experiments, such as the Michelson-Morley experiment, failed to detect the aether.

* Einstein's Theory of Special Relativity: Published in 1905, this theory stated that there is no such thing as absolute time and absolute rest. The implications of special relativity are not apparent in everyday life because we are not used to encountering the speeds at which it applies. However, they have been repeatedly confirmed by experiments. Special relativity led to a new understanding of the concept of spacetime.

* Einstein's Theory of General Relativity: Developed over the eleven years following special relativity, this theory extended special relativity to include gravity. It is based on the revolutionary idea that spacetime is not flat, as previously assumed, but is curved and warped by mass and energy. Although it reproduces almost all the predictions of Newton's theory of gravity when gravity is absent, general relativity predicts very different effects in situations involving strong gravity, such as gravitational waves and black holes.

* Quantum Field Theory: When the laws of classical physics were applied at the atomic and subatomic level, they were found to be inadequate. The principles of quantum physics were developed in the early decades of the 20th century. Quantum field theory combines special relativity with quantum physics.

* QED: The first force for which a quantum version was created was electromagnetism. The quantum field theory describing the electromagnetic field is called quantum electrodynamics or QED. In quantum field theories, forces are transmitted by fields, but in quantum field theories, force fields are described as consisting of various elementary particles called bosons. Bosons are force-carrying particles that fly back and forth between particles of matter, transmitting forces to them.

* Standard Model: This model encompasses the unified theory of electroweak forces and quantum chromodynamics (QCD) as a theory of strong forces. Although very successful and consistent with all current observations, the Standard Model is fundamentally unsatisfactory because it fails to unify the electroweak and strong forces and does not include gravity.

* Supergravity: In 1976, a possible solution to the problem of creating a quantum theory of gravity was found. It is called supergravity. **Supergravity has the potential to solve the infinity problem because it realizes that infinities from closed loops of force particles are positive, while infinities from