Cosmology Flashcards
What is the cosmological principle?
- universe is isotopic and homogeneous
- laws of physics are universal
What does homogeneous mean?
- the universe is of a constant matter density
What does isotropic mean?
- universe appears the same in all directions
What is the formula for red shift factor?
- v/c
- v: speed of recession
- c: speed of light
What is stellar parallax?
Apparent shift of position of a nearby star against the background of distance stars.
What is the maximum distance that can be measured using stellar parallax?
100 pc
How is stellar parallax used to measure the distance to stars?
- star is observed twice, six months apart
- angular displacement between positions is calculated
- halved to find parallax angle in arc seconds
- find distance in parsec
What is the formula for finding distances using stellar parallax?
d = 1/p
- d: distance in Pc
- p: angle in arcseconds
What is Hubble’s Law?
- recession speed of a galaxy is directly proportional to its distance from Earth
What is the equation for Hubble’s Law?
- v = H0d
What is the value of Hubble’s Constant?
- SI: 2.27×10−18 S-1
- non SI: 69.8 km/s/Mpc
How to calculate the age of the universe?
- in seconds
- 1/H0
- H0 in SI
What happened as soon as the Big Bang happened?
- time and space created
When were the first hadrons made?
- 10-3 seconds
What happened after the Big Bang?
- time and space created
- universe rapidly expands in period of inflation
- first fundamental particles gain mass
- quarks bind to create hadrons
- universe cools as it expands
- allows for formation of atoms
- nuclei capture electrons
- EM radiation from this stage forms CMBR
How was CMBR created?
- When nuclei captured electrons, resulted in transition of electrons down energy levels
- released energy in form of photons
- giving rise to EM radiation, initially Gamma
- stretched to microwaves as universe has expanded
What evidence is there of dark matter?
- discrepancy between observed rotational speed of galaxies and the predicted rotational speed
- prediction was for observed speed to drop with increased diameter
- instead observed speed was higher than prediction
- suggested a halo of matter to be present around the galaxy
What forces does dark matter interact through?
- seems to be gravitational
What is dark energy?
- energy of empty space
- used for the continuous expansion of the universe
