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Midterm

GSC 102 Midterm: gsc 102 exam 2 study guide


Department
Geological Sciences
Course Code
GSC 102
Professor
Leech Peter
Study Guide
Midterm

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Lecture 12: The Age of the Universe
Lightyears
- the distance that light can travel in one year. (1 lightyear = 5,900,000,000,000 miles)
Parallax
- to determine the distance to (relatively) nearby objects. A parsec is the distance to an
object whose parallax angle is 1 arcsecond when using a 1 AU baseline.
Nebulae
- There are plenty of fuzzy, gassy, diffuse nebulae in the galaxy. For example, this is the
Orion Nebula, in the Orion Constellation.
Cepheid stars and the Andromeda Galaxy
- Cepheid stars pulse with a frequency which is proportional to their luminosity. By
measuring how dim Cepheid stars in the Andromeda Galaxy appeared to be, Hubble
determined that it is about 2.5 million lightyears from Earth thus The Andromeda Galaxy
is about the most distant thing you can see with the naked eye
Light waves and the Doppler effect
- Light is a wave. Different WAVELENGTHS correspond to different colors. The
DOPPLER EFFECT is when a wave emitted or received by a moving object appears to
change. Light from things moving towards us gets bluer, and from things moving away
from us gets redder.
Redshift ad Hule’s Law
- It turns out that all very distant galaxies are REDSHIFTED. HUBBLE’S LAW observes
that more distant galaxies are moving away from us more quickly
Expansion of the Universe and age of the Universe
- Hubble’s Law implies that space is expanding. We can extrapolate this expansion
backwards to get an age for the Universe: 13.7 billion years.
Cosmic microwave background and blackbody radiation
- Anything with a temperature emits blackbody radiation. As something gets hotter, it
emits wavelengths (or colors) of higher energy. The cosmic microwave background is
essentially the temperature of the Universe. If we know what temperature it was produced
at, and we know its temperature now, we can calculate how long the Universe has been
cooling for.
Age of the Universe from cosmic microwave background
- Black body radiation the color of the universe, we can calculate how long the universe is by
going back and seeing how hot it was.
Dark energy
- However, the expansion actually appears to be ACCELERATING. This acceleration is
explained by DARK ENERGY. The effect of dark energy is very small. However,
because it appears to be constant everywhere, it is actually the main thing in the
Universe.
Lecture 13: Atoms and the Milky Way
Hydrogen and helium
- As the Universe expands and cools, they combine to form the simplest atoms, hydrogen
and helium. The early universe was composed almost entirely out of hydrogen and
helium.
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Cosmic microwave background and galaxies
- Variations in the Cosmic Background Microwave show that the early Universe was
slightly lumpy. These lumps are areas of slightly more dense gas which would eventually
begin to collapse under the influence of gravity.
- As the gas clumps collapse, they begin to spin faster, which causes them to expand into
disks
- Clumps of gas within a galaxy collapse to form stars
- evolution of most galaxies includes collision with other galaxies. However, this does not
appear to have occurred recently with the Milky Way.
Fusion of lighter elements into heavier elements
- Small isotopes can undergo FUSION, although it requires huge temperatures and
pressures. Hydrogen atoms have one proton. Helium atoms have two protons.
- This is how our Sun works, by fusing hydrogen into helium. Fusing higher elements
requires higher temperatures and pressures.
Why even-numbered elements are generally more common than odd-numbered elements
- In bigger stars, with higher pressures, you can start jamming helium nuclei onto other
atoms. The bigger your atom, the harder this is, and the less energy you produce
Why iron-56 is more abundant than similar elements
- Iron-56 is the most stable isotope
S-process (slow process) the s-process produces approximately half of the isotopes of the
elements heavier than iron, and therefore plays an important role in the galactic chemical
evolution
R-process (rapid process) and where it occurs The r-process is element formation in
SUPERNOVAS. its faster rate of neutron capture of more than one neutron before beta-decay
takes place.
Gravitational lensing
- We can measure the masses of galaxies by using gravitational lensing
Gravitational lensing suggests that galaxies are heavier than they look
Rotation of galaxies
- bodies orbiting a large mass should move faster when they are closer to it, ---But
galaxies don’t rotate like that. The distant stuff orbits at the same speed as the near stuff.
Dark matter
- are embedded in a disk or halo of matter that we cannot does not interact with light
- around 85% of all mass in the Universe is dark matter.
Lecture 14: Formation of the Earth and Moon
Chronometric vs stratigraphic ages
- The Precambrian Eons are defined CHRONOMETRICALLY.
The Eras and Periods of the Phanerozoic will be defined STRATIGRAPHICALLY.
Accretion of the Solar System
- Around 4.6 billion years ago, the Solar System forms from a huge rotating cloud of dust
and gas by accretion
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Conservation of angular momentum
- is the rotational analog of linear momentum. It is an important quantity in physics
because it is a conserved quantity the angular momentum of a system remains constant
unless acted on by an external torque.
Homogenous accretion and differentiation of the Earth
- The Earth (like the other planets), forms by homogeneous accretion. It is a completely
mixed mass of metals and stony materials. But when the Earth melts, the materials
separate out.
Earth’s first atosphere: hdroge ad heliu
- Earth’s “First Atmosphere” is probably composed of hydrogen and helium. It probably
escapes to space pretty fast.
Frost line
- Beyond the “frost line”, planets accumulated gases and volatiles
After mars its beyond frost line
Where the Moon comes from
- The GIANT IMPACT HYPOTHESIS suggests that the Moon was formed around 4.5
billion years ago by a collision between the Earth and another Mars-sized planet
- The Moon has three layers, just like the Earth, but the core is relatively small, and there is
much less iron than the Earth has
Origi of darker ares or seas o the luar surfae
- Between 3-3.5 billion years ago, volcanic eruptions released darker basalt-like material
onto the Moon’s surface
- Lunar MARES like the Sea of Tranquility are made of roughly the same stuff as oceanic
crust on Earth
-
Late heavy bombardment and the Nice model
- One suggested reason for this is the LATE HEAVY BOMBARDMENT, around 4 billion
years ago
- The NICE MODEL suggests that the Late Heavy Bombardment was caused by Jupiter
migrating through an asteroid field.
-
Tides, hages i the Moo’s orit ad rotatio, ad hages i the Earth’s rotatio
- The tides act as a brake on the Earth’s rotation, but also speed up the orbit of the Moon
- As the orbit of the Moon speeds up, the Moon moves further away from the Earth (at
about an inch per year today)
- When the Moon formed, it was probably about 15,000 miles away
- The Moon has already become TIDALLY LOCKED to the Earth. That’s why you always
see the same side of the Moon.
Acasta gneiss and plate tectonics
- is probably the oldest exposed surface rock in the world, (very) roughly 4 billion years
old
- a metamorphized version of a granite-like material, plate tectonics must have been
operating in the early Archaean
-
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