Astronomy 309R – Spring 2009
Study Guide to Help Prepare for Exam 3
Please read chapters 6, 7, and 8 in Hawley & Holcomb, and the articles by Gray and by
Luminet et al. that are assigned for homework.
General relativity will be on the 3
but black holes will only be on the 4
What is the Speed-of-Light Postulate?
When we say that the speed of light is constant,
what are we implying that the speed of light is independent of?
(It is independent of the
motion of the source of light and is also independent of the velocity of the observer.)
What are caveats to the applicability of the Speed-of-Light Postulate?
propagates inside water, glass, or another transparent medium, its speed is reduced.
is a consequence of the interaction of light with the medium, and does not contradict
Why can way also say that the constancy of the speed of light is a
(The constancy has been tested in numerous experiments.)
What is the speed of light in vacuum, in meters per second, or other units, such as
kilometers per second?
[While the Wikipedia is
unreliable in general
, it has a nice article on the speed of light,
please read it:
. You can also take a look in:
What is the statement of the Special principle of relativity
(this is the other postulate of
special relativity, in addition to the Speed-of-Light Postulate)?
(The special principle of
relativity is similar to the statement of Galilean invariance: All physical laws are the same
to observers moving with respect to each other, and with respect to the universe as a
whole, with constant velocities.)
The special principle of relativity can be distinguished
from the general principle of relativity, or the equivalence principle, which generalizes
the statement about all physical laws being equal to
freely falling observers.
What is a
(It is a system of coordinates, or a perspective, in relation to
which the measurements of size, position, and motion can be made.)
(An inertial frame is a reference frame moving with constant
velocity with respect to the universe; Newton’s laws of motion are applicable inside any
Any inertial frame moves with constant velocity with respect to any other
Constant velocity can include the zero velocity, that is, the absence of
motion, as a special case.)
What are the implications of the Speed-of-Light Postulate for simultaneity?
that appear simultaneous to one observer may not appear simultaneous to another.
events that are simultaneous to one observer will
appear simultaneous to any observer
moving with finite velocity with respect to the first observer along the direction
connecting the two events.)