ANSWERS for QUIZ 1:
1) Yes
2) We measure the minimum mass. The problem has to do with orientation.
As the planet's orbit becomes more inclined (i.e., more face-on), we measure
a smaller change in radial velocity (for face-on, it is exactly zero).
Thus, the mass we infer can be much larger.
3) He still had the planets move on circular orbits.
4) We actually measure the radial velocity of the star, which is due
to the planet's orbit.
5) A few properties are planets that are very massive, close to
the star, are in elliptical orbits, are around stars with higher
metal content, among a few others.
6) The phases of Venus proved that the Earth is not at the center.
7) Kepler uses photomety and makes a light curve to follow the eclipse.
8) To turn the Kepler candidate objects into planets we need to measure the
radial velocity curve. This data will tell us the mass of the object which
we can use to determine if it is a planet or a star or a sunspot. The
amplitude of the RVC tells us the mass of the object.
9) Pluto was downgraded since we are beginning to find other bodies
that are as massive as Pluto but at slightly larger distance from
the Sun. Thus, it looks like there is a large body of Kuiper Belt
tye objects out there.
10) For an edge-on configuration, we can detect both a proper motion
and a radial velocity.
ANSWERS for QUIZ 2:
1) neutrino
2) moving fast or being in a strong gravitational field will put you
into the future of a frame at rest. To travel into the past, you have
to travel faster than the speed of light.
3) Photons are moving maximally through space and minimally through
time. Thus, they are effectively not moving through time, so they do
not age.
4) A doppler shift is a measure of the wavelength, which would then
tell you how fast the object that emitted the light is moving. The
speed of light is just that: it is a measure of how fast the light is
moving.
5) Inside a black hole, spacetime is curved in on itself. Thus, a
straight line is a curved path around the center. Thus, you would be
trapped to only walk in that curved path.
6) Mercury is on an elliptical orbit, so it is sometimes closer to the
Sun. When it gets closer to the Sun, if spacetime is curved then
Mercury can cover more distance as it travels than if spacetime where
not curved (either think of time dilation or length
contraction). Thus, it overshoots its orbit and then precesses.
7) yes
8) the person sitting is aging faster
9) An astronaut flying around the Earth feels no weight. The
equivalence Principle tells us that this means no acceleration. No
acceleration implies constant velocity, which implies traveling in a
straight line. Thus, as the person circles the Earth, they are
traveling in a straight line. The only way for this to be true is if
spacetime is curved.
10) Comparing to light paths: in a stationary frame the light path is
shorter than in the moving frame. If speed of light is a constant in
any frame, then, since distance = c x time, time in the moving frame
much be larger, implying the clock must be running slower.
ANSWERS for QUIZ 3:
1) white dwarf, neutron star, black hole, brown dwarf
2) watching an object disappear
3) When galaxies merge, some of the material collides (mainly the
gas). The collisions cause the particles to lower their velocities and
they fall towards the center, building up a bulge component.
4) dark matter and we don't understand how gravity works (the
equations may need to be modified)
5) X-ray observations
6) Quasars appear bright and they are distant, both of these combined
imply that they must be intrinsically very bright. They are considered
small since they vary their light in a short time. In order to see
this short time variation, the light travel time across the object has
to be shorter than the time variation, otherwise the variation would
be washed out. Since the variation is short, then the object must be
small.
7) As material falls towards a black hole, it collides with each other
at high velocities. This interaction creates heat and energy, which we
see as light.
8) Since the black hole is so small, as material falls in it cannot
fit in such a small region. It then finds a weak spot in the
infalling material and it then gets funneled out into a jet.
9) Dark matter is less concentrated than normal matter in a galaxy
since the dark matter does not interact well with anything. Thus, it
stays in its original distribution. Since the normal matter interacts,
it falls in towards the center and collects there.
10) As material falls in towards the black hole it forms a jet. This
jet then pushes back on the infalling material and even forces its way
out of the galaxy. This process then does two things: it shuts off the
fuel supply to the black hole which stops the growth, and it blows off
some of the gas in the galaxy thereby halting the formation of
stars. This whole process is called feedback. This link between the
mass of the black hole and the mass in stars through the jets and
winds is what creates the relationship.
ANSWERS for QUIZ 4:
1) normal matter, dark matter, dark energy
2) candle, dieing flashlight, strobe light, etc.
3) The amount of structure that we see determines the temperture of
the dark matter, since that will determine how much it clumps. Colder
material clumps more than hot material.
4) Faster moving particles, namely neutrons, can hit the material in
the experiments and mimic dark matter. The fast moving particles come
from the cosmos, as cosmic rays. We use the Earth itself and lead to
shield the experiments from these particles.
5) V=H0 x D. V is the velocity which one determines from taking a
spectrum and measuring the redshift. D is the distance which we get
from (e.g.) a standard candle, using an image and measuring the amount
of light. H0 is the expansion rate which we get from the ratio of V
and D.
6) air, dark matter, virtual particles, etc. are distributed
isotropically. The chairs are not.
7) We measure velocity and distance. Velocity comes from taking a
spectrum and measuring the redshift. Distance comes from a standard
candle or standard ruler. The standard candle uses an image and the
total amount of energy. A standard ruler uses an image to measure a
separation.
8) When Einstein calculated the evolution of the universe, he assumed
it was static (finite and constant size). This led to it collapsing in
on itself given its age. To counter that, since we still existed, he
had to add a fudge factor to cause it to expand.
9) That Andromeda is much further away, implying that the Universe was
much larger. And that the Universe is expanding.
10) That the Universe expansion is accelerating.
ANSWERS for QUIZ 5:
1) The results from SN 1987A show that the neutrinos and the light
arrived at about the same time. Given the distance, this implies they
travel at about the same speed. The experiment shows that neutrinos
travel faster than light. Resolutions include that the experiment is
wrong due to noise, and that the different energies of the neutrinos
imply different properties (higher energy might be able to tunnel).
2) SN1a result from mass transfer from another star. When the star
gets 1.4 solar masses of material is explodes as a SN. Thus, it is
always the same mass that creates the explosion, which implies always
a similar amount of energy.
3) If SN in the past are fainter than ones now, that would cause them
to appear more distance. A reason is the chemical composition of the
SN may be different, or there may be more dust.
4) When the material in the middle of the runs out of fuel, the star
begins to contract. The core gets continually denser until it turns
into a neutron star. At that point, it acts like a solid surface, and
the material that keeps falling in hits this surface. That infalling
material then bounces off the surface.
5) The existence of the microwave background, and Big Bang
Nucleosynthesis (the relative abundances of elements).
6) The observations are measuring the relative amount of the elements
in the early universe, which include studying stars that are very old
(thus, pristine material). The theory comes from using our
understanding of nuclear reactions that can produce those
abundances. The theory relies on the density of normal matter. Thus,
the relative abundances then imply 4% normal matter according to
theory.
7) We use fluctuations in the cosmic microwave background which will
determine the amount of structure in the Universe. The amount of
structure is due to the overall density and geometry in the
Universe. The average size of the structures tells us that we are at
the critical density.
8) To have more structure than now, you could 1) increase the amount
of matter, 2) decrease the amount of dark energy
9) It is a blunder since Einstein missed the opportunity to discover
that the Universe is expanding. He basically missed that his model of
the cosmological constant placed the universe in an unstable
configuration.
10) microwave