announcements exam 2 is next time (march 4). will cover chapters 1 – 3 and chapter 4 through page...
TRANSCRIPT
Announcements• Exam 2 is next time (March 4). Will cover Chapters 1 – 3
and Chapter 4 through page 98 (up to but not including Waves) of Foundations of Modern Cosmology. Sample Questions are posted
• Project topics are due before spring break (March 6). Decide on a topic and come talk to me about it. The topic can be anything of current cosmological interest. A two or three sentence “abstract” will be due next time (worth 5% of the project grade).
The Universe according to Quantum Mechanics
• You can’t tell precisely where anything is.
• You can’t tell precisely how fast anything is moving.
• Particles act like waves.
• Waves act like particles.
• Particles can pass through “solid walls”
• A very non-deterministic universe completely contrary to Newton’s mechanical universe
According to the Bohr
model you cannot tell where the electron is,
only what its energy is.
Heisenberg's Uncertainty Principle says xp
Ionization
If an incoming photon has enough energy it can completely knock the electron out of the atom
What are protons and neutrons made of?
If they can decay into something else, they must be made of something smaller.
en p e
The Four Fundamental Forces: The Strong Nuclear Force
The best thing we have to describe the strong nuclear force is called quantum chromodynamics or QCD
The Gravitational Force
which best describes gravity is Einstein’s General Relativity. We will go into GR in much more detail later
Newton’s Universal Gravitation works well for most situations but the theory
Work & EnergyEnergy is a relatively new concepts. Gottfried Leibniz first proposed something similar to kinetic energy in the late 1600’s. Thomas Young was the first to use “energy” in the modern sense in 1807
Gottfried Leibniz 1646 - 1716
Thomas Young 1773 - 1829
Potential Energy: the ability to do work
Each of the four fundamental forces has a potential energy associated with it. The one we see the most is gravitational potential energy. The electromagnetic potential is the foundation of chemistry (and circuits). Nuclear potential is important in the interiors of stars and the early universe.
The Zeroth Law of Thermodynamics
Thermodynamic Equilibrium means there is no net heat flow from one object to another
Second Law of Thermodynamics
Any system which moves heat from a cool temperature to a warmer temperature must have some energy input.
Any system which does work by removing heat from a heat source must exhaust some heat
Third Law of Thermodynamics
You can’t get there from here!
It is impossible to achieve a temperature of absolute zero