Oct 15 Class Summary

Observable Universe Energy Content

~68% Dark Energy, ~27% Dark Matter, ~5% Ordinary Matter

Breakdown of Ordinary Matter in Universe

~90% interstellar/intergalactic gas and ~10% in stars

Galaxy Mass Composition

~90% Dark Matter halo and ~10% stars/gas/dust

Top 2 Elements in Cosmic Abundance

Hydrogen (~75% by mass) and Helium (~23% by mass)

Top 2 Elements in Whole Earth

Iron (~32%) and Oxygen (~30%)

Top 2 Elements in Earth's Crust

Oxygen (~46%) and Silicon (~27%)

Top 2 Elements in Earth's Atmosphere

Nitrogen (~78%) and Oxygen (~21%)

Top 2 Elements in Human Body by Mass

Oxygen (~65%) and Carbon (~18%)

Top 2 Elements in Human Body by Atom Count

Hydrogen (~63%) and Oxygen (~24%)

Dark Matter Effect & Distribution

Exerts attractive gravitational force; forms a vast spherical halo around galaxies

Dark Energy Effect

Exerts repulsive cosmic force that causes accelerating expansion of the Universe

Inverse-Square Law

A physical law stating that force is inversely proportional to the square of the distance (1/r^2)

Newton's Law vs Coulomb's Law Forces

Gravity is always attractive; electrostatic force can be attractive or repulsive

Subatomic Charges

Proton (+1e), Electron (-1e), Neutron (0)

Matter vs Dark Energy on Expansion

Matter slows expansion (deceleration); Dark Energy speeds expansion (acceleration)

Escape Speed Definition

Minimum velocity needed for an object to escape a body's gravitational pull without further thrust

Escape Speed of Earth

11.2 km/s (~7 miles per second)

Total Elements vs Naturally Occurring

118 total known elements in Periodic Table; 94 occur naturally

Big Bang Nucleosynthesis Products

Created all Hydrogen, most Helium, and trace Lithium in the Universe

Origin of Elements Heavier than Iron

Synthesized during supernova explosions and collisions of neutron stars

Hydrogen Atom Structure

1 proton, 0 neutrons, 1 electron

Helium-4 Atom Structure

2 protons, 2 neutrons, 2 electrons