Spring 2007 ASTR 3740 Homepage
Spring 2007 ASTR 3740 Midterm Review
The midterm will test everything covered during the semester so far.
The midterm will be a 50 minute test.
For 2 point questions,
your answer should consist of one or two
clear, grammatically correct sentences.
Answers to questions with more points should be proportionately longer.
You get 1 point for each time you misspell Schwarzschild.
Review Questions

Electromagnetism.
What role did electromagnetism play in leading up to the
Theory of Special Relativity?
What are electromagnetic waves?

History.
Contrast the contributions of
Young,
Maxwell,
Michelson & Morley,
Fitzgerald,
Lorentz, Poincaré, and Einstein
to the historical development of the Theory of Special Relativity.

Postulates of Special Relativity.
What are the postulates of special relativity?
What is an inertial frame?
Which postulate or postulates distinguish special relativity
from its predecessor, classical Galilean space and time?

Spacetime Diagram.
Make sure you thoroughly understand spacetime diagrams.
Simultaneity,
lightcone.
Review time dilation, Lorentz contraction,
the twin paradox.

Simultaneity.
What does it mean in special relativity for two events to be simultaneous?
Describe a practical method by which simultaneity
can be defined in special relativity.
Draw lines of simultaneity on a spacetime diagram.
How do these lines change for observers with different
velocities relative to each other?

Lorentz Transformation.
What is a Lorentz transformation?
What happens to a spacetime diagram
when it is subjected to a Lorentz transformation?

Four Vectors.
Make sure you thoroughly understand four vectors.
What is a four vector?
How does it transform under Lorentz transformations?
Give some examples of four vectors.

Time Dilation.
On a spacetime diagram,
show how two people moving relative to each other can
both consider each other's clock to run slow.

Lorentz Contraction.
On a spacetime diagram,
show how two people moving relative to each other can
both consider each other's ruler to be contracted.

Energy Momentum.
Why are energy and momentum described by a 4vector in special relativity?
How does
E = m c^{2}
emerge from the special relativistic description of energy?
How is the invariant spacetime length of the energymomentum 4vector
related to rest mass?

Twin paradox.
What is the twin paradox?
Explain the twin paradox with the help of a spacetime diagram.

The Spacetime Wheel.
What is the invariant spacetime distance between two events
on a spacetime diagram?
How does the invariant spacetime distance change
under a Lorentz transformation?
How does the spacetime distance differ from the ordinary
distance between two points in 3dimensional space?
What is proper time?
What is proper distance?
How are proper time and proper distance related to the invariant spacetime distance?
When an ordinary wheel rotates, the angle of the wheel about its axis changes.
When the spacetime wheel rotates, what is happening?

What things actually look like at relativistic speeds.
Why are you not normally aware of relativistic effects?
If you move through a scene at relativistic speeds,
do you see objects whizzing by simply Lorentzcontracted and timedilated?
Answer: No, the because of the light travel time.
Explain how light travel time affects appearances.
Give an account of the rules of relativistic perspective:
draw the scene on a celestial sphere,
stretch the celestial sphere into a celestial ellipsoid,
and place the observer at a focus of the celestial ellipsoid.
Give an account of the 4 relativistic effects:
(a) aberration;
(b) redshifting and blueshifting;
(c) dimming and brightening;
(d) the apparent rate at which clocks tick.

Superluminal motion.
Blobs are seen to emerge from the nucleus of the
quasar 3C273
at about 8 times the speed of light.
Does this contradict special relativity? Explain.
The blobs are thought to be part of a jet powered by a black hole
at the center of the galaxy housing the quasars,
and that there is a second jet emerging in the exact opposite direction
from the jet that we see.
Why do we not see the second jet?
Updated 2007 Feb 14