Lecture 33. Mysteries of the Sky
Lecture 33. Mysteries of the Sky
A. Class Business
- Again,
review topics* and readings list*, both on main page
- Homework 6. due at end of this class --
NO LATE WORK ACCEPTED:
solutions before you're out the door!
- I will not be here during final. Your grader,
Ijaz (pronounced "EE-jahz") will be!
I have given trial versions of final to others,
and they found no problems, so you should be okay!
B. Good Theory: Explains Observations,
Makes Testable Predictions
- Newton's gravity: explains tides, orbits, etc.,
and predicts location of unknown planet, Neptune
- Einstein's general relativity:
explains Mercury's precession, predicts bending of light
C. Extraterrestrial Life
-
The Drake Equation*
-- number of alien civilizations in the Milky Way
attemping to communicate with us
Ncomm =
(Nmw) x (fp) x (nl)
x (fl) x (fi) x (fc)
x (fL)
- Nmw = # stars in Milky Way
- fp = fraction of stars with planets
- nl = number of planets capable of
supporting life
- fl = fraction that do support life
- fi = fraction on which intelligence evolves
- fc = fraction of intelligent life
that tries to communicate
- fL = fraction of planet's existence
during which intelligent life survives
- Want to help in the search? Try
SETI at home.*
D. Mysteries of the Sky --
in order of difficulty to solve
- neutrino masses
- solar cycle/coronal heating
- dark matter
- quasars
- big bang/cosmology
- E.T.'s