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Final Exam Review: Jeopardy Questions
by Dan Perley with (very) slight modifications by Nicholas McConnell
General Physics
---------------------------------100
If two objects have the same mass, their center of gravity is located
at this position.
-> Halfway between them.
200
If a visible light source is receding fast enough from an observer, its
energy may be shifted into this part of the spectrum.
-> Infrared (or radio)
--- Or, just to redder wavelengths in the visible if it's not moving so
fast.
300
In general, this is the approximate maximum size of an object which is
observed to vary in brightness on a timescale of about one year.
-> One light-year
--- See CS-266 on page 59 of your Course Reader.
400
This is the ratio of the speed of the following two photons, as
measured from Earth, as they travel through space: an ultraviolet
photon emitted by the Sun, and an radio photon emitted by a spaceship
traveling away from us at half the speed of light.
-> One
--- All photons move at the same speed in vacuum, period!
500
The force of gravity and the intensity of a light source both fall off
according to this mathematical law.
-> Inverse square (law)
Solar System
-----------100
Uranus and Jupiter are examples of this kind of planet.
-> Gas giant. (or Jovian planet)
200
This celestial object is believed to have been created by a collision
between Earth and a protoplanet.
-> The Moon
300
The presence of immense quantities of this gas causes the surface of
Venus to be hotter than even the daytime side of Mercury.
-> Carbon dioxide
400
This region of icy, orbiting debris includes among its largest members
the bodies Sedna, Quaoar, and Pluto .
-> Kuiper Belt
500
This is the largest primarily rocky object known in the Solar System.
-> Earth
--- An amusing factoid, in my opinion. The cores of the giant planets
are probably mostly rocky and substantially larger than Earth, though.
Galaxies
-------100
The Milky Way is this type of galaxy.
-> Spiral
200
In at least some cases, these very large galaxies are thought to be
formed by mergers of smaller galaxies.
-> Elliptical
300
Star formation occurs in irregular and peculiar galaxies, as well as in
this portion of a spiral galaxy.
-> Spiral arms.
400
This is the best-accepted explanation for why the rotation curve of a
galaxy doesn't look at all like the rotation curve for the solar
system, even out to very large distances.
-> Dark matter
500
Careful observations of stars in the two satellite galaxies of the
Milky Way ruled out the possibility that a large fraction of the mass
in the Universe is in the form of a class of objects grouped under this
acronym.... much to Governor Schwarzenneger's disappointment.
-> MACHOs.
--- MACHOs, MAssive Compact Halo Objects, were once thought to be a
good candidate for dark matter.
However, studies of gravitational
lensing of stars in the Magellenic clouds have largely ruled them out.
Sun / Stars
----------100
The specific nuclear fusion reaction that powers the Sun.
-> Hydrogen to helium.
200
How does the lifetime of a 2-solar-mass star compare to the Sun’s
lifetime (no math)?
-> It is shorter.
--- The lifetime of a star is inversely proportional to the cube of its
mass. A larger star lives for a shorter time than a smaller star. (My
apologies for expressing this item in question, rather than answer,
format.)
300
A star with a temperature of 3000 Kelvins and a luminosity 50 times
that of the Sun is a member of this evolutionary class.
-> Red giant.
400
What property is summarized in the mnemonic “O Be A Fine Guy/Girl, Kiss
Me Lovingly?”
 Spectral Type
---Temperature decreases from O down through L.
500
If the Sun were replaced by a star with ten times the Sun's surface
temperature but of the same physical size, this is the distance from
the Sun in AU that a planet would have to be to receive the same amount
of energy as Earth does.
-> 100
--- Since the star is the same size as the Sun, the luminosity is
simply proportional to the fourth power of the temperature: (L/Lsun) =
(T/Tsun)^4 = 10,000.
But the energy received by an object of constant
area falls of as the inverse square of the distance, so to receive the
same amount of energy as Earth, the planet would have to move the
square root of 10,000 (=100) times further away... more than twice the
distance of the orbit of Pluto.
(Note: No such stars actually exist - even the hottest (non-whitedwarf) stars are only about 6-7 times the Sun's temperature, and these
are all somewhat larger than the Sun. This is just an exercise.)
Supernovae / Stellar remnants / black holes
------------------------------------------100
A type-II supernova leaves this super-dense object in its wake.
-> Neutron star (or black hole)
200
These cosmic lighthouses have strong magnetic fields and spin rapidly.
-> Pulsars
300
Both types of supernovae emit the majority of their energy in this
form.
-> Neutrinos
--- Visible light comprises only a small fraction of the energy emitted
by any supernova.
400
These two explosive phenomena are both thought to be triggered by
matter from a nearby star accreting onto a white dwarf.
-> Novae, and Type I-a supernovae.
--- Type II supernovae are caused by core-collapse and explosion of a
supergiant star.
500
This is the ultimate fate of a binary system containing two neutron
stars, each with a mass of about 3 solar masses.
-> Coalescence (due to GR) and formation of a black hole.
--- General relativity says that a close binary system will slowly
decay, causing the objects to eventually merge. The upper limit of a
neutron star is around 3 solar masses, so the resulting object (which
would have a mass of about 6 solar masses) would be a black hole and
not another neutron star.
Black Holes, Quasars and Cosmology
---------------------------------100
This mysterious entity comprises about 70% of the current energy
content of the universe.
-> Dark energy
200
A universe with a matter density precisely equal to the critical
density is described by this kind of geometry.
-> Flat (Euclidean).
300
Quasars were first discovered by observations in this region of the
electromagnetic spectrum.
-> Radio
400
The *only* supermassive black hole whose mass is known from
measurements of the positions of stars in orbit around it is located in
this galaxy.
-> Milky Way
--- Supermassive black holes in other galaxies were found by Doppler
studies of gas orbiting the center of the galaxy.
500
The age of the universe is determined by the inverse of this parameter
- *if* the universe contains no matter or antigravity.
-> The Hubble "constant".
--- A matter-dominated universe would be younger than this. An
antigravity-dominated universe would be older than this. (The real
universe is a combination of matter and antigravity, with antigravity
the dominant component at the present, although matter was the dominant
component in the distant past. Interestingly, the two effects of the
two components almost completely cancel each other out - so in fact the
inverse of the Hubble constant is actually within 2% of the actual age
of 13.8 billion years... even though the universe is definitely NOT
empty.)
The Big Bang
-----------100
The full name of the "afterglow" of the big bang, which was discovered
in 1965.
-> Cosmic (Microwave) Background Radiation. (CBR)
200
This is the heaviest element created by the Big Bang itself.
-> Lithium (no penalty for saying helium)
--- A large amount of hydrogen and helium were created, along with a
trace amount of Lithium-7. NO heavier elements were created in the Big
Bang; they were all formed in stars and supernovae.
300
In the theory we primarily discussed in class, the energy for inflation
is thought to be related by a symmetry breaking between these two
things.
-> Forces (strong nuclear and electroweak, *or* gravity and grandunified)
--- This is just one hypothesis, but is the one Alex focused on in
lecture.
400
The two main problems with the original bang theory were that the
universe is very nearly flat, and this.
-> The homogeneity problem: universe (the CBR in particular) is too
uniform on large scales.
500
"The Big Bang happened at a specific point in the universe currently
occupied by this galaxy."
-> NO ANSWER. The Big Bang did not happen at a "specific point".
Everybody who *doesn't* answer this question (or says "no answer") gets
1000 points!!!
Final Jeopardy: The Origin of the Elements
-----------------------------------------An element, and the process or object which ultimately created it.
Possible Answers:
Hydrogen - Created in the Big Bang.
Helium - Created in the Big Bang, somewhat later than hydrogen. A
relatively small amount was created in normal (and giant) stars, and in
supernovae.
Lithium - Created in the Big Bang, somewhat later than hydrogen. A
small amount was created by cosmic rays (not covered in this class).
Beryllium, Boron - Created by cosmic rays interacting with other
elements (not covered in this class).
Carbon, Nitrogen, Oxygen - Created in red giant stars, and to some
extent in supernovae.
Fluorine through Iron - Created in supergiant stars and in supernovae
(in various proportions depending on the particular element).
Elements heavier than Iron - Created ONLY in supernovae.