The Crisis of Classical Physics and Einstein’s Theory of General Relativity

Newton v. Einstein Newton’s Laws of motion are a very good approximation of the fundamental laws that govern our universe in the non-warped spacetime we experience here on Earth. Classical Newtonian mechanics break down in the presence of high gravitational fields. Click video to start

Newton v. Einstein Newton’s laws cannot be used to explain phenomena such as conduction of electricity in a semiconductor, optical properties of substances, and superconductivity. Explanation of these phenomena requires more sophisticated physical theory, including General Relativity and Relativistic Quantum Mechanics.

Newton v. Einstein In quantum mechanics concepts such as force, momentum, and position are defined by linear operators that operate on the quantum state; at speeds that are much lower than the speed of light, Newton's laws are just as exact for these operators as they are for classical objects. At speeds comparable to the speed of light, the second law holds in the original form F = dp/dt, which says that the force is the derivative of the momentum of the object with respect to time. Some of the newer versions of the second law (such as the constant mass approximation above) do not hold at relativistic velocities.

General Relativity Many predictions of general relativity differ significantly from those of classical physics, especially concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light.

General Relativity Examples of differences include gravitational time dilation, the gravitational redshift of light, and the gravitational time delay. General relativity's predictions have been confirmed in all observations and experiments to date. Although general relativity is not the only relativistic theory of gravity, it is the simplest theory that is consistent with experimental data. Click video to start

Elements of Physics: Modern Physics and Cosmology The following is a program on the way that modern physics has revolutionized the way we understand our universe. Physicists found that the sub-atomic world does not follow the laws of classical physics and developed quantum theory to give a more exact explanation. Einstein developed his special theory of relativity to explain what happens when objects travel close to the speed of light and later developed the general theory of relativity, which provided a new explanation of gravity. These theories have shed light on the existence of black holes and the origins of the universe. Approximate running time: 56 minutes

Citations Elements of Physics: Modern Physics and Cosmology. Discovery Education. (2006). Retrieved October 2, 2009, from Discovery Education: http://streaming.discoveryeducation.com/ General Relativity. Wikipedia. (2009). Retrieved October 2, 2009, from Wikipedia: http://en.wikipedia.org/wiki/General_relativity