ODU - Pt 2 Flashcards
(13 cards)
What leads us to the theory of the expanding universe?
Measurements of the velocities of galaxies and their distance from us
What can the mass of a galaxy be estimated by?
By the orbital speed of stars within the galaxy
Where does evidence supporting dark matter come from?
Comes from estimates of the mass of galaxies
Where does evidence supporting the existence of dark energy?
Comes from the accelerating rate of expansion of the universe
What is the temperature of stellar objects related to?
related to the distribution of emitted radiation over a wide range of wavelengths
What is the peak wavelength of this distribution for hot objects?
shorter for hot objects
What is the peak wavelength of this distribution for cold objects?
longer for cooler objects
Comparison of temperature and radiation?
Hotter objects emit more radiation per unit surface area per unit time than cooler objects
Time dilation
time is dilated when it is observed to be shorter/longer (compared to a stationary observer)
Length contraction
length is contracted when it is observed to be shorter/longer (compared to a stationary observer)
The doppler effect
The change in the observed frequency of a wave, when the source or observer is moving
Redshift
Knowledge that the light from objects moving away from us is shifted to longer
wavelengths (redshift).
Evidence of the big bang and an expanding universe?
-redshift of galaxies leading to hubble’s law: more distant galaxies moving away faster than newer ones, same in all directions
-cosmic microwave background: cooled radiation from the big bang observed in every direction
-olber’s paradox
