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.