20 - Cosmology Flashcards
what happens to wave relative to position of wave
source moving to receiver - shorterπ (squashed)
source moving away - longerπ (stretched)
changing of wavelength effect names for sound and light
sound - doppler effect
light - red/blue shift
red shift and blue shift
red - π stretched, f low (away from earth) shifted to red end of spectrum
blue - π shortens, f high (towards earth) shifted to blue end of spectrum
first piece of evidence for big bang and universe expansion
red shift - most galaxies are moving away and ones further away moving faster showing greater red shift
binary start systems and red shift
they come in many forms but specific type:
one side gets red shifted and the other gets blue shifted
amount of red shifted calculation
z=change in π / original π = v/c
faster, the bigger the change in wavelength
Hubbles law
speed of galaxy moving away is directly proportional to its distance
v=Hod where Ho is hubbles constant
t=d/s =1/Ho = age of universe
assuming expansion of universe rate is constant and also Cosmological principles
how can we tell galaxies are red shifting
by looking at absorption lines from light. Pattern is similar to our sun but is stretched. the amount of red shift can be calculated using z=change in π / original π = v/c
what is the big bang theory
universe began with colossal explosion roughly 13.7b years ago from singularity and has been expanding ever since. evidence - red shift, CMBR β¦
what is cmbr
cosmic microwave background radiation
radiation remaining from big bang that fills the whole universe, reminiscent of atom formation. formed as gamma rays during big bang but now in micro wave part of spectrum (temp 2.7K) due to cooling of universe and red shift
piece of evidence for big bang and at this time the universe became transparent and light could travel through (before was plasma)
intensity of cmbr
uniform in all directions but small ripples in intensity correspond to forming of first stars and galaxies
third piece of evidence for big bang
primordial helium and hydrogen - so much helium and hydrogen during the evolution of universe as hadrons were forming nuclei
universe evolution timeline
13.7b years ago - big bang - time and space created as a singularity - infinitely dense and hot
10-35s - no matter only energy - temp roughly 10^28K INFLATION STAGE
10-6s - quarks and leptons are made - energy > mass
10-3s - quarks combine to form hadrons
1s - matter is all made , temp roughly 10^9K
100s - hadrons combine to form nuclei (H and He)
PRIMORDIAL HYDROGEN AND HELOUM EVIDENCE 3
380,000 years - nuclei and electrons combine to form atoms, CMBR is made (atoms formed late her as it is cool enough for electrons to stay in energy levels)
30my - stars formed
200my - our galaxy is formed
4.5by - our solar system is made
400,000 years ago - first humans , temp roughly 2.7K
what is the doppler effect
the apparent shift in wavelength of a wave caused by relative motion between source and observer
how may weather doppler effect distinguish between different types of precipitation
different forms of precipitation may reflect different amounts of energy. hail may reflect more for example so difference in the reflected microwaves affects the intensity received by receiver
doppler effect to figure out speed of a tennis ball serve
source sends out microwaves that are reflected off the ball. ball acts as a source and speed measured by measuring the doppler shift of the wave
how is doppler effect used to determine relative velocity of distant galaxy?
absorption spectrum of specific element is determined laboratory. same spectrum is observed from light of distant galaxy and compared. any difference in absorption lines and wavelength is caused by relative motion of the galaxy and earth. if⦠blue shift and if⦠red shift (each absorption line changes by same percentage)
state the cosmological principle
universe is isotropic and homogeneous
why is our understanding of the universe unreliable for the early moments?
no experimental or physical evidence, energies unreproducible (high temp)
nature and origin of dark matter
hydrogen and helium gas formed after big bang, left from supernova
how does density of neutron star compare to that of materials commonly found on earth
neutron star much more dense than earth materials, density same as atomic nucleus
explain how temperature of universe changed after first millisecond
temp decreases as energy is turned into mass and work is done against attractive force
explain how universe became transparent
protons and electrons separate initially. charge prevents passage of EM waves. proton bind to electron as atoms formed, mean EM waves are no longer absorbed
explain the existence of primordial hydrogen and helium
too high to originate solely on stellar fusion
sim and diff of composition of sun and early stars
both hydrogen and helium in core fusing
sun has greater proportion of helium as hydrogen fuses to helium in sun
sun also contains traces of heavier elements up to iron
explain how hubble showed that universe was expanding by studying light from stars and galaxies
redshift data - velocity calculated by red shift z=v/c
distance data
v is proportional to d
for galaxies receding from earth - universe began from single point
why is the ultimate fate of universe not known
critical density not known
density of universe uncertain
