Physics 107
Ideas of Modern Physics
Course home page:
http://uw.physics.wisc.edu/~himpsel/107/Lectures/lectures.htm
Syllabus:
http://uw.physics.wisc.edu/~himpsel/107/Lectures/Syllabus.pdf
Course info:
http://uw.physics.wisc.edu/~himpsel/107/Lectures/107info.htm
Your job
• Read the lecture notes, consult textbook for details
 Hobson, Physics Concepts and Connections
• Participate in the lectures
 Interrupt me any time you have a question, idea, …
• Participate in the discussion sections (optional)
 Starting next week
• Do the homework
 Assigned Wednesdays, due the following Wednesday
• Write an essay or give a presentation
 See the link on the course home page
• Take the exams
 Three exams (incl. final); Two best of three counted
Grading
Two best of three exams: 25%+25%
Homework: 25%
Essay or presentation: 25%
Topics of the course
• Ideas that revolutionized physics
• The big questions in physics today
• The impact of physics on our life
Goethe’s Faust makes a pact with the devil to find out
“whatever holds the world together at its inner core” :
"was die Welt im Innersten zusammenhält"
• Critical judgment
• Back-of-the-envelope calculations
• Separating science from religion, philosophy, myth, …
From the small …
Nanoscience
Manipulating single atoms
to create quantum waves
… to the large :
Cosmology
How did the Universe begin ?
How will it end ?
The top 11 questions
in astrophysics
• What Is Dark Matter?
• What Is the Nature of Dark Energy?
• How Did the Universe Begin?
• Did Einstein Have the Last Word on Gravity?
• What Are the Masses of the Neutrinos?
• How Do Cosmic Accelerators Work?
• Are Protons Unstable?
• What Are the New States of Matter at Exceedingly High Density?
• Are There Additional Space-Time Dimensions?
• How Were the Elements from Iron to Uranium Made?
• Is a New Theory of Matter and Light Needed at the Highest Energies?
The Physics of Weather
Storms
Where do storms get their energy from ? From water vapor.
It takes a lot of energy to vaporize liquid water on a stove.
This energy is released when water vapor is converted back
to liquid water in clouds (which consist of little droplets).
A large storm sweeps up water vapor from vast stretches
of warm ocean, particularly in the tropics.
With global warming the oceans get warmer. More water
evaporates and produces more fuel for storms.
Hurricanes
1) Moist air (orange) is pulled into the low pressure region
at the center of a hurricane (the eye).
2) It rises at the eyewall and forms clouds. Condensing water
releases energy, which gets converted into wind energy.
3) The air is expelled at the top forming thin clouds (blue).
Formation of spirals in cyclones
(hurricanes, low pressure systems)
Satellite photo: A low pressure system over Iceland forms a
spiral with counter-clockwise rotation. So does a hurricane.
Why ? Low pressure pulls the air towards
the center of a storm (blue arrows). The
rotation of the Earth creates the Coriolis
force (red arrows). It deflects the wind
towards the right in the Northern Hemisphere. The two forces become balanced
when the air moves in counter-clockwise
fashion (opposite red and blue arrows).
Low
For details, download Cyclone from the Lecture Notes.
Passage of a low pressure system
H
Madison
Cold
front
Warm
front
Typically, low pressure systems move from West to East
at latitudes north of Madison. As a system moves through,
the wind rotates from South to West and North, following
the counter-clockwise rotation around the low pressure.
Global Wind Patterns
High
Low
High
Westerlies
Trade Winds
Low
High
Low
The Trade Winds
N
Low
Low
Low
Low Low Low Low
S
Hot air rises at the Equator
and creates a ring of low
pressure. Air is pulled towards the low pressure
(blue arrows). The Coriolis
force deflects the wind towards the West (red arrows)
until the two forces balance
each other ( red and blue
arrows opposite).
Hurricane Tracks
Hurricanes start near Africa, carried west by the trade winds.
They drift north and catch the Westerlies, which carry them
back east. That’s how Columbus sailed to America and back.
Summary
A variety of weather patterns can be explained by a combination of the Coriolis force and the force pulling air towards low
pressure. The spiral pattern of cyclones (Hurricanes and low
pressure systems) is created by a central disk of low pressure.
The global wind pattern is generated by a ring of low pressure
around the Equator, where hot air rises.
The Coriolis force is caused by the rotation of the Earth. It
deflects winds to the right in the Northern Hemisphere (to
the left in the Southern Hemisphere (mnemonic: southpaw
= left-handed).
Adding the pull towards low pressure to the Coriolis force
causes the (counter-intuitive) counter-clockwise rotation of
cyclones in the Northern Hemisphere.