Post on 01-Jul-2018
Weekly Schedule
Today
•First HW Problems assigned
• Ch 28
• Review Q’s 1-5
• RAT- 1-4
•The Big Bang
•Stars and the formation
of elements
•Lab # 1: Intro to
Science
Next Tuesday
• Quiz # 1
• Elements, bonds, and
earth materials
• Crystallization activity
Remember Dark Matter? Yesterday were able to
Alpha Magnetic Spectrometer have shown hints of what is theorized to be dark matter.
Dark matter, which is believed to hold the universe together, has never before been
directly observed.
Few Quick Definitions
• Theory- well-substantiated explanation of some aspect of the natural world, based on a body of knowledge that has been repeatedly tested and confirmed through observation and experimentation (Plate tectonics and Big Bang)
• Scientific Law is a description of an observed phenomenon (Gravity and Hubble’s)
Formation of the solar system The Big Bang
Video
• Theory—our universe began with a
primordial explosion some 13.7 billion years
ago
• Marks the beginning of space and time
Big Bang • An expanding
Universe? “When
did it all begin?”
– The Big Bang: all
mass and energy
in a single point
– It exploded ~13.7
Ga and has been
expanding ever
since.
Fig. 1.5b
Aftermath of the Big Bang • Researchers have developed a model of the
Big Bang. – During the first instant, only energy—no matter—was
present.
– Started as a rapid cascade of events.
• Hydrogen atoms within a few seconds
• At 3 minutes, hydrogen atoms fused to form helium
atoms.
• Light nuclei (atomic no. < 5) by Big Bang nucleosynthesis
– The Universe expanded and cooled.
Fig. 1.5b
After the Big Bang • With expansion and
cooling, atoms began to
bond.
– Hydrogen formed H2
molecules—the fuel of
stars.
– Atoms and molecules
coalesced into
gaseous nebulae.
• Gravity caused collapse
of gaseous nebulae.
• Collapse resulted in
increases in:
• Temperature.
• Density.
• Rate of rotation.
Evidence of The Big Bang • Continuing expansion of the universe
• Measured cosmic background radiation
• Measurements of element abundances
The Big Bang Cosmic Microwave Background (CMB):
• The figure below shows the temperature of the CMB at every point in space. The uniformity of the CMB means that at some point in time all the matter in the universe was very close together.
The Big Bang
Relative Abundance of Light Elements
• Scientists predict that if the Big Bang occurred, there would not have been enough time to form any heavy elements due to the rapidly expanding universe; only hydrogen and helium could have been formed.
• 75% of all the matter in the universe is hydrogen and about 25% is helium. (Heavy elements make up less than 1%)
Close-up of the Eagle Nebula.
• Masses of hot and cold gasses colliding
• It is at the
Interface between the different temp gasses that protostars are formed
Aftermath of the Big Bang Forming Stars
Gravity Pushes inward
Nuclear Fusion pushes
outward. H + H He + energy
Protostars eventually heat up to initiate fusion
The future of a star is almost solely determined
by its MASS 25
15 3 1.5 1.0 .75 .50
35,00030,00011,0007,000 6,000 5,000 4,000
80,000 10,000 60 5 1.0 0.5 0.03
3 15 500 3,000 10,000 15,000 200,000
Size Surface Luminosity Lifetime Msolar Temp (K) Lsolar MegaYears
Lifetime of a Star
Mass of a star determines element production
• Small mass stars (Sun)
– Produce up to C
• Large mass stars (10-100x sun)
– Produce up to Fe and may…..
Supernova
Gravity wins over fusion= collapsing core which causes
violent expulsion of the outer layers of the star
SN 1987A
Supernova get hot enough to produce all elements heavier than Fe
U is the heaviest natural element
What’s left? Dust clouds= Nebula
The Crab Nebula was created from a supernova in 1054AD. Recorded in China. But not in Europe.
Forming the solar system ~4.5 Ga
• Formation of accretion disk
– Collapsing nebula’s gas flattens out because of gravity and conservation of angular momentum
Forming the solar system • In the center of the nebula compression begins
fusion of hydrogen into helium= SUN
• Electrostatic and gravitational interactions cause the dust and ice grains in the disk to accrete into Planetesimals
Forming the Earth • Accretion continues until
the center is hot enough to melt the rock= magma
• Earth forms and begins to differentiate via density
Forming the Moon~ 4.53 ± .01 Ga
• Crater the size of Mars
• Melted the Earth and ejected a large part of the mantle into space
• Eventually accreted into the moon
Forming the Atmosphere
• Three step process-
– Volatile gases during cooling
– Sulfur and CO2 from volcanic eruptions
– Bacteria began to produce oxygen about 2.8 G
• and Oceans
Death of the Universe
• http://www.youtube.com/watch?v=lhTSfOZUNLo