time…and distance moon: mars: sun: pluto: 212,000 miles 48,000,000 miles 93,000,000 miles 3.6...
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Time…and distance
Moon:
Mars:
Sun:
Pluto:
212,000 miles
48,000,000 miles
93,000,000 miles
3.6 billion miles
Milky Way Galaxy> 100 billion suns
60,000 light yearswide
Earth
Nearest star?
Alpha Centauri:4.3 light years or25 trillion miles
Galaxy Clusters
Hubble telescope estimates >125 billion galaxies
Nearest? Andromeda2 millionlight years away
For every grain of sandon Earth, there are a million stars.
Geologic Time Scale
How do you determine ages?
1. Relative age dating. Comparing the age of one thing relativeto something else.
2. Absolute age dating. Using analytical techniques to determinethe real age of an object.
Superposition
Sediments accumulating on top are younger thanthose below.
Cross-Cutting
Rocks which cross-cut are younger than those they cut.
Unconformity
Sediment deposition, followed by a period of eroison,then more sediment deposition. End result? A time gap.
Age Placing
Grand Canyon
Canyon Ages
Layers on Mars
Index Fossils
Organisms which lived only during a specific periodof time.
Correlation
Same rock layers, correlated over vast distancesSame rock types, ages, fossils, etc.
Continental Drift
Correlation was used during the development of the continental drift theory, years ago.
Absolute Age Dating
Relative age dating placed rock layers intoa specific order.
Radiometic age dates were used to determinethe age of the rock layers and verify theordering.
The AtomAtom: In the nucleus, there are protons (+) and neutrons (neutral charge)
Surrounding the nucleus are negatively charged electrons- used for bonding with other atoms to form molecules
Atomic number = number of protons in the nucleus
Atomic weight = # protons + # neutrons
Isotope: Same number of protons, different number of neutrons
Radioactivity
Some isotopes are unstable. These will “decay” to stable isotopes calleddaughter products.
As isotopes decay, they give off subatomic particles + heat
Radiation
Nuclear Fuel Rods
To build a nuclear reactor, what you need is some mildly enriched uranium. Typically, the uranium is formed into pellets with approximately the same diameter as a dime and a length of an inch or so. The pellets are arranged into long rods, and the rods arecollected together into bundles. The bundles are then typically submerged in water inside a pressure vessel. The water acts as a coolant. In order for the reactor to work, the bundle, submerged in water, must be slightly supercritical. That would mean that, left to its own devices, the uranium would eventually overheat and melt.
To prevent this, control rods made of a material that absorbs neutrons are inserted into the bundle using a mechanism that can raise or lower the control rods. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the rods are raised out of the uranium bundle. To create less heat, the rods are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to shut thereactor down in the case of an accident or to change the fuel.
Nuclear Meltdown
Chernobyl, Ukraine: 1986
Explosion released 200 times more radiation than theHiroshima and Nagasaki bombs combined.
Chernobyl plume
Contaminated Areas
Sarcophagus
Alpha Emission
Beta Emission
Electron Capture
Examples
Unstableisotope
Stable daughterproduct
Half Life
Half life: Over a given period of time, half the parent isotopedecays into its daughter product.
Examples
Uranium 238 to Lead 206: 4.5 billion yearsUranium 235 to Lead 207: 713 million yearsThorium 232 to Lead 208: 13.9 billion yearsRubidium 87 to Strontium 87: 50 billion yearsPotassium 40 to Argon 40: 1.5 billion years
Mineral Examples
ZirconCommon in granites
Zr+Si+O
Trace amounts of Th & U
Link to radonRadium->Radon->Polunium
Radon half life: 3.8 days
EPA action level:4 picocuries per liter
Carbon 14 Dating
Half-life: 5730 yrsLive organisms maintain a fixed amount of C-14C-14 decays to N-14 after death.