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Terms in this set (27)
Big Bang Theory
The theory that the universe originated in a huge explosion that released all matter and energy.
Age of the Universe
14 billion years
Elements that existed in abundance after the Big Bang
H and He
How did the other elements form?
-Nucleosynthesis is a cosmic reaction where new nuclei are formed from existing nuclei
-Neutron stars colliding
What is the significance of the birth and death of stars to the creation of elements?
-The heavier elements remain in the interior of the star until the star dies in which a supernova occurs
-Supernovae scatter those elements back into space to become new nebular "dust."
-Moreover, other elements are created during the explosion. From that nebular material another generation of stars forms, going through the same phases of stellar evolution - accumulation of dust, gravitational energy to thermal energy, Helmholtz-Kelvin contraction, ignition of H-fusion, etc.
How do stars form?
A cloud of dust and gases collapse under the force of gravity and create a Protostar. Pressure causes nuclear fusion to begin.
What is the difference between a star and a protostar?
Protostars aren't hot enough to perform nuclear fusion
Why are thermonuclear reactions that take place in the interior of stars important in the formation of heavier elements?
1). creates elements heavier than H and He,
2). products of the burning become the fuel for the next burning
what was/is different about the nebular material from which 2nd and later generations of stars form?
They burn heavier elements
What event in a star's life is responsible for the difference? i.e. what happens to earlier generation stars that will affect the composition of the nebular material from which younger stars are made?
The nuclear material in a star affects the next generations
Is the sun a 1st generation star? How do we know?
No, because our sun is burning He instead of H
Basically, all of these theories states that nebular dust clumped together and eventually formed a planet.
What is meant by a differentiated planet?
Layered. Crust, mantle, outer and inner core.
What is a planetesimal?
Planetesimals are asteroid-like bodies with diameters of a kilometer or so.
When did the Earth and the solar system form?
4.5 billion years ago
what is meant by homogeneous accretion and how do we then account for the layering we know to exist in the planet (also related to differences in the compositions among the various planets)?
condensation (solidification) of materials and accretion occurs first, and differentiation or layering occurs later. The planet has no discrete layering.
What lines of reasoning are used to deduce the structure? the composition(s)?
earthquake seismology, the distribution of mass within the Earth, and the composition of extraterrestrial samples.
what is the "earthquake mechanism?"
mechanism known as elastic rebound. Seismic waves are elastic waves carrying the energy generated by the earthquake
What kind of seismic waves are there and how do they differ in the way they affect particle movement, velocity, etc.?
-Body waves: travel in the earth
-S or P waves. P waves are faster and S waves can't travel through liquids
-Surface waves: travel on the earths surface
-Raleigh and love waves
How do these waves travel through homogeneous vs inhomogeneous (i.e. layered) mediums or materials?
Refract and get faster when traveling through inhomo layers
What determines wave velocities?
The material properties of rocks they travel through
What are the shadow zones and what do they tell us about the earth's structure?
They exist because P-waves and S-waves bend as they travel through different materials. The bending prevents the waves from reaching some parts of Earth. S-waves provide evidence for a liquid outer core because they can't travel through liquids they are not detected past 104 degrees. While P-waves suggest and inner solid core because the shadow zone where no waves occur between 104-140 degrees.
Does seismology alone tell us the composition of the earth?
No, rather than constrain of the possibilities
Is the boundary of the earth's crust and the mantle.
This is a layer in the upper mantle (but not the uppermost!) where wave velocities slow down somewhat and then speed up again as they penetrate this layer.
how does the density and chemical composition of the earth's crust differ from the rest of the planet?
Less dense materials. Earth's more dense materials are in the core
why doesn't the earth's magnetic field originate from a permanently magnetized core? or does it?
In particular, (1) the field has non-dipolar components (so not simple dipole, but the "gross" field is essentially dipolar!), (2) the field changes in strength, the magnetic pole moves, and the polarity flips (the N- and S-poles reverse!), and (3) temperatures in the core are above the Curie temperature (so magnetic properties are "lost").
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