Friday, March 8, 2008
Announcements:
- Let's keep the family and friends of Eve Carson in our thoughts and prayers.
Assignments:
- Review the answers to the conceptual questions for Chapter 11.
- Read Chapter 12 and be prepared to discuss on Monday, March 17.
- Submit your topic ideas for the physics Web Project.
- Group project topics are due Monday, March 17
Chapter 10 - Special Relativity
Special relativity deals
with
inertial frames of reference (a = 0)
General relativity (a <>
0)
Examples of inertial and non-inertial reference
frames: a) space ship traveling in a straight line, b) space
shuttle in orbit, c) this classroom
Consequences of Special Relativity: As v -> c, several
physical parameters change by factor of gamma = 1/sqrt(1-v^2/c^2)
Ponderable:
What are "relativistic" speeds? (see table below)
Time dilation: t =
to*gamma
Length contraction: L =
Lo/gamma
Mass increase: m =
mo*gamma
Relativistic energy: E =
mc^2 = gamma*Eo
Relativistic KE: K =
Eo*gamma - Eo
Applications of
relativity: nuclear power, GPS
Black holes: Light
cannot
escape a star with a radius less than or equal to the Schwarzschild radius: R =
2GM/c^2
Step by Step into a Black Hole - Simulated views of a black hole. Interactive Black Hole Simulation
Chapter 11 - General Relativity
General relativity deals with accelerated reference frames and the
curvature of spacetime as a result of gravity.
Equivalence principle - All physical experiments yield identical
results in
an accelerated reference frame as they do in a gravitational
field. (i.e. No experiment can distinguish between an
accelerated lab in zero gravity or a stationary lab on Earth.)
Gravitational lensing - the gravitational attraction due to a massive
object (a star, black hole, or galaxy) can bend light much like a lens
refracts light.
Diagram
showing gravitational lensing caused by a galaxy.
Excellent
examples and class notes from a lecture on general relativity at
Berkeley.
Based on observations from astronomy, there is evidence that the
universe is expanding at an accelerated rate. NASA's WMAP website
Color image of
the microwave background of the universe from WMAP.
The "discovery of the blackbody form and anisotropy of the cosmic
microwave background radiation" is so important in physics that it
received a Nobel prize last year (Mather
and Smoot, 2006)
The shape of the universe: closed, flat, or open?
Euclidean geometry deals with the three
familiar coordinate directions for 3D objects: x, y, z
A
fourth
dimension of space is one that is orthogonal (perpendicular) to the
first three, which is difficult to visualize.
In terms of relativity,
time
is generally considered to be the fourth dimension.
Evidence of dark matter and dark energy is measured using gravitational
lensing. Examples are in a recent issue of Physics Today.
Minute Paper:
1) What did you learn today?
2) What questions or comments do you have?