Relativity and Quantum Mechanics Notes

1. Relativity and Quantum Mechanics Notes CP Physics Ms. Morrison

2. Einstein’s Theory of Relativity • Two parts – Special and General • Special: deals with question of whether rest and motion are relative or absolute and the consequences that result from them being relative • General: primarily applies to particles as they accelerate, is a radical revision of Newton’s theory of motion • Both theories have been confirmed to be accurate to a very high degree

3. Special Theory of Relativity (1905) • Speed of light, c, is a constant • 3 x 108 m/s • Does not matter the speed of the source of light, the speed of the observer, or the instrument used to measure it – always constant regardless of one’s frame of reference • The laws of physics are the same in any frame of reference • E = mc2 – mass can be converted into huge amounts of energy and huge amounts of energy are needed to create a tiny amount of matter

4. Special Relativity, pg 2 • As approach speed of light: • Length gets shorter • Mass becomes greater • Time slows down • Twin paradox – a space traveler could travel at speeds close to speed of light and would return to Earth younger than his twin brother

5. General Theory of Relativity (1915) • The effect of gravitational fields cause the space-time continuum to be curved or warped by large masses • The more massive the object – the more it bends the space-time around it • Real cause of gravitational attraction • Gravity not only can bend light but slow it down – time dilation

6. General Relativity, pg 2 • Predicted the existence of black holes • Because they are so massive, have very high gravity and can bend light, slow light down, and stop light from escaping • Can make time stand still – a space probe would appear to slow down and virtually stop as it speeds toward the event horizon of a black hole • One of pillars of Big Bang Theory

7. Uncertainty Principle • States: the more precisely the position of a particle is determined, the less precisely the momentum is know in this instant and vice versa • Sometimes stated differently – the act of measuring one magnitude of a particle, whether it is mass, velocity, or position causes the other magnitudes to blur • Blurring of these magnitudes is a fundamental property of nature

8. Uncertainty Principle, pg 2 • 1925 – two competing mathematical theories that attempted to explain electron orbits: • Heisenberg developed matrix mechanics that interpreted the electron as a particle with quantum behavior – quantum jumps between energy levels • Schrodinger – interprets the electron as a wave • 1926 – Schrodinger publishes proof that shows that the two theories are equivalent – an electron is a particle that can behave like a wave

9. Uncertainty Principle, pg 3 • In an experiment, though, cannot be both a wave and a particle at the same time, the experimenter must choose what to observe in the experiment • Notion that observer becomes part of the observed system is fundamentally new in physics – observer no longer external, through the act of the measurement he becomes part of the observed reality (he affects the system)