Earth and Space Science: Key Concepts in Geology and Astronomy

Observation

Fact-based description.

Inference

Interpretation of an observation.

Hypothesis

Testable explanation of facts or observations.

Prediction

If/then statement describing what will happen if hypothesis is correct.

Theory

Well-supported explanation for why/how.

Law

Rule describing observations considered unchanging.

Good Science

Tentative, testable, reproducible, natural cause.

Bad Science

Attacks scientists, bad stats, cause/effect confusion.

Doppler Effect

Frequency change due to motion.

Light Year

Distance light travels in one year.

Big Bang Theory

Universe began 13.8 billion years ago with rapid expansion.

Nebular Model

Gas/dust clouds clumped to form star + planets.

Astronomical Unit (AU)

Distance from Earth → Sun.

Magnetic Field

Deflects solar wind, generated by Earth's core.

Terrestrial Planets

Mercury, Venus, Earth, Mars (rocky).

Jovian Planets

Jupiter, Saturn, Uranus, Neptune (gas).

Dwarf Planet

Pluto.

Crust

Outer layer, rich in O + Si.

Continental Crust

Felsic, high silicon/oxygen

Oceanic Crust

Mafic, high Fe/Mg.

Lithosphere

Rigid crust + upper mantle.

Mantle

Ultramafic, high Fe/Mg.

Asthenosphere

Plastic part of mantle, flows slowly.

Lower Mantle

Solid mantle below asthenosphere.

Core

Iron + Nickel

Outer Core

Liquid, generates magnetic field.

Inner Core

Solid.

P-Waves

Compression waves, travel through solids/liquids.

S-Waves

Side-to-side waves, only through solids.

Igneous Rock

From cooling magma/lava.

Intrusive Igneous

Large crystals, cools inside Earth.

Extrusive Igneous

Small crystals, cools at surface.

Mafic

Dark igneous rocks, Fe/Mg rich.

Felsic

Light igneous rocks, Si/O rich.

Ultramafic

Mantle rocks, very low Si, very high Fe/Mg.

Sedimentary Rock

From compacted and cemented sediments.

Metamorphic Rock

Rock changed by heat and pressure.

Relative Dating

Sequence of events without exact ages.

Original Horizontality

Rocks start flat.

Superposition

Oldest at bottom, youngest at top.

Uniformitarianism

Present is the key to the past.

Cross-Cutting Relationships

Cutter is younger.

Unconformity

Missing time in rock record.

Inclusion

Rock fragments inside another are older.