cosmology Flashcards
what is cosmology
Study of the structure and evolution of the Universe
what image did ancients used to have of the universe
- geometric image
- flat earth
- “Proven” by Ptolemy
*A rebirth of rational thinking e.g. Heliocentric ideas happened in 15th-century Europe
3 things Newton devised
- The Law of Universal Gravitation
- The Three Laws of Motion
- The mathematics of change (calculus)
< He proved that natural law governs natural events
2 evidence for a spherical Earth
- A curved shadow crossed the Moon during eclipses
- Only the tops of distant sailing ships were visible
who circumnavigated the spherical earth
Magellan, 1520
difference between how a flat earth would receive the sun compared to a round one
- flat Earth - receive light at a right angle at noon everywhere
- round Earth - receive light at diminishing angles toward the poles
who almost accurately measured the earth
Eratosthenes
who proved Earth’s rotation
Jean Bernard Léon Foucault’s pendulum (1851)
*Clearly visible in a time-lapse photograph of the night sky
what is wavelength
spacing of waves - compress or relax with relative motion
what is frequency
waves passing a point in an interval of time
in the visible light spectrum is blue of red higher frequency
- Blue = Higher frequency
- Red = Lower frequency - more spaced out waves
how does light from an approaching and receding star vary
- Light from an approaching star is compressed - higher frequency
- Light from a receding star is expanded - lower frequency
what is the Doppler shift / effect and how it relates to the modern universe
Hubble concluded galaxies were moving away from us rapidly as Light from distant galaxies appeared “red shifted.” instead of “blue shifted” - evidence for expansion of the universe
explain the Big Bang theory
When the expanding Universe began
- All of the mass and energy in the Universe was packed into a single small point
- It exploded ~14 Ga and has been expanding ever since
what are nebulae
vast gas clouds that formed from the 1st atoms (hydrogen and helium) of the universe developing soon after the big bang
one strong evidence for the Big Bang
Universe Composition
- Started out ~100% Hydrogen and Helium
- NUCLEOSYNTHESIS occurred during the earliest stages of the Big Bang
- Explains present composition:
~90% H
~10% He
«1% heavier elements
explain the process of star formation and evolution after the Big Bang
- Post-Big Bang Expansion & Cooling → H₂ formed, fueling future stars
- Formation of Gaseous Nebulae → Atoms and molecules gathered under gravity
Gravity-Induced Collapse → Caused:
Increased temperature & density
Faster rotation - Formation of accretion discs
- Nuclear Fusion Ignition → Created first-generation stars, consuming hydrogen rapidly
- Star Death (Supernova) → When hydrogen ran out:
Stars collapsed & heated - Heavy elements were produced
- Explosive supernova released these elements into space, enriching the universe
- This cycle of star birth + death eventually led to the formation of galaxies, planets, and life
how do stars create elements
through nucleosynthesis -> stars are “element factories”
what did Stellar Nucleosynthesis form
elements up to iron (Fe, atomic #26) inside stars
what did Supernova Nucleosynthesis form
elements heavier than iron during supernova explosions.
what determines the elements that stars produce
Star Mass
- Small Stars (e.g., the Sun) → Burn slowly, live longer (10 billion years), create lighter elements up to carbon
- Large Stars (10–100x Sun’s mass) → Burn rapidly, live shorter (millions of years), create heavier elements up to iron
planet characteristics
- large solid body orbiting a star (e.g., the Sun)
- nearly spherical shape
- cleared its neighborhood of other objects
*Pluto, previously defined as a planet, is now excluded (belonging to the Kuiper Belt)
what is included in our solar system
- 7 other planets
- The moon - solid body locked in orbit around a planet
- The Sun – An average star
- Asteroids – Rocky or metallic fragments
- Comets – Fragments of ice orbiting the Sun
- Kuiper Belt and Oort Cloud objects
what is the Nebular Theory
Explains how the Solar System formed 4.56 billion years ago (Ga) from a 3rd, 4th, or nth generation nebula
