Deep Time & The Beginning of Everything

Cosmic Microwave Background Radiation

It's leftover thermal energy from the Big Bang, now cooled to just above absolute zero and detectable in all directions in space. Example: Satellite missions like COBE and WMAP detected this faint glow, providing strong evidence for the Big Bang.

Redshift of galaxies

Redshift shows that galaxies are moving away from us, indicating that the universe is expanding from an initial explosion. Example: Edwin Hubble observed that the farther away a galaxy is, the faster it moves away—known as Hubble's Law.

Abundance of light elements

The universe contains large amounts of hydrogen, helium, and small amounts of lithium, consistent with early universe conditions predicted by the Big Bang theory. Example: The observed helium concentration in stars aligns with predicted values from Big Bang nucleosynthesis.

Nebular Hypothesis

A theory stating the Solar System formed from a rotating cloud of gas and dust (solar nebula) about 4.6 billion years ago. Example: The flattening of the solar nebula into a disk explains the planets' orbits on a common plane.

Planetesimals formation

Dust and ice particles stuck together through static and gravitational forces, forming small bodies that collided and grew. Example: Planetesimals merged to form protoplanets like Earth and Mars.

Role of gravity in Solar System formation

Gravity pulled matter inward, forming the Sun at the center and causing accretion in orbiting material. Example: Gravity caused heavier elements to sink inward and form rocky planets.

Terrestrial planets

Rocky planets with solid surfaces, typically smaller and denser than gas giants. Example: Mercury, Venus, Earth, and Mars.

Gas giants and ice giants

Large planets composed mostly of hydrogen, helium, and ices, with thick atmospheres. Example: Jupiter and Saturn are gas giants; Uranus and Neptune are ice giants.

Dwarf planets

Celestial bodies orbiting the Sun that are spherical but haven't cleared their orbital path. Example: Pluto, Ceres, and Eris.

Asteroids and comets

Asteroids are rocky bodies mostly found in the asteroid belt; comets are icy and develop tails when near the Sun. Example: Halley's Comet orbits the Sun every 76 years.

Earth formation

Earth formed from accreting planetesimals, with heat from collisions and radioactive decay melting the interior. Example: Differentiation caused denser materials like iron to sink to form the core.

Planetary differentiation

The process where heavier materials sink to the center and lighter materials rise, forming layers. Example: Earth's core is mostly iron, while the crust is silicate-rich.

Earth's main compositional layers

Crust, mantle, and core, each with distinct materials and densities. Example: The mantle is composed of silicate rocks richer in magnesium and iron.

Earth's physical layers

Lithosphere, asthenosphere, mesosphere, outer core, and inner core.

Asthenosphere

Partially molten layer that allows tectonic plates to move.

Temperature and Density Change

Both temperature and density increase as depth increases.

Inner Core

The hottest and densest layer of Earth.

Mohorovičić Discontinuity (Moho)

The boundary between Earth's crust and mantle where seismic waves speed up.

Chemical and Physical Changes Across the Moho

Chemically, the composition changes from basalt/granite to peridotite; physically, wave speeds increase.

Whole-Earth Sketch Layers

Inner core, outer core, mantle, lithosphere, and asthenosphere in correct order and scale.

Lithosphere

Thinner than the mantle but includes the crust and uppermost mantle.

Deep Time

A concept describing Earth's immense age (4.6 billion years), beyond typical human time scales.

Geologists and Deep Time

To understand processes like plate tectonics and evolution that require vast timescales.

Common Misconception About Deep Time

Many think Earth is only thousands of years old, often due to literal interpretations of religious texts.

Deep Time Misconceptions Effects

They can lead to rejection of scientific evidence and misunderstanding of Earth's processes.

Relative Dating in Geology

Determining the order of events without exact dates, using principles like superposition.

Absolute Dating

Determining an exact age using radioactive decay and isotopes.

Radiometric Dating

A method that uses the decay of radioactive isotopes to determine age.

Fossils and Rock Dating

Index fossils indicate specific time periods and help correlate rock layers.

James Hutton

Known as the 'Father of Modern Geology', he proposed uniformitarianism.

Charles Lyell

He expanded on Hutton's ideas and wrote Principles of Geology, influencing Darwin.

Alfred Wegener

Proposed the theory of continental drift, suggesting continents were once connected.

Nicolaus Steno

Formulated principles of stratigraphy, such as superposition and original horizontality.