Cosmology Flashcards
What do scientists believe about the Universe from around 14 billion years ago?
they believe that the Universe was in one extremely tiny and dense place
it then suddenly exploded, and has been expanding ever since
this expansion is shown by the red-shift of galaxies and the energy of the explosion can be seen everywhere in the Universe as the CMBR
What was the Big Bang?
a giant explosion that caused the universe to expand from a single point, cooling as it does so, to form the Universe today
What can be seen as each galaxy in the Universe expands away from the others?
galaxies moving away from each other, and the further away they are the faster they move
What is a result of the initial explosion of the Big Bang?
the Universe continues to expand
What can be used to demonstrate galaxies moving away from each other in the Universe?
points drawn on a deflated balloon where the balloon represents space and the points represent galaxies
when the balloon is deflated, all the points are close together and an equal distance apart
as the balloon expands, all the points become further apart by the same amount
this is because space itself is expanding between the galaxies
What happens to the density of galaxies as the Universe expands?
density of galaxies fall
What are the two pieces of evidence that support the Big Bang theory?
red shift
cosmic microwave background (CMB) radiation
What evidence from the red shift supports the Big Bang theory?
if we examine the light spectra for distant galaxies we can see that the wavelengths of the light have become longer
we call this stretching of the waves ‘red-shift’. it tells us that the galaxies producing the light are moving away from us .the further away a galaxy is, the greater its red-shift, so it is moving even faster
this is evidence that the Universe is expanding and so it supports the Big Bang theory
What evidence from cosmic microwave background (CMB) radiation supports the Big Bang theory?
microwave radiation can be detected EVERYWHERE in the Universe
these are the stretched remains of high energy gamma radiation that would have been produced in the explosion that created the Universe
they have stretched because the Universe is expanding
What is cosmic microwave background (CMB) radiation a result of?
CMB radiation is a result of high energy radiation being redshifted over billions of years
What do the red/orange/brown colours on a CMB map represent?
red/orange/brown regions represent warmer temperature indicating a higher density of galaxies
What do the blue colours on a CMB map represent?
blue regions represent cooler temperature indicating a lower density of galaxies
What is expected after an explosion such as the Big Bang?
-matter is first densely packed and as it explodes it, it moves out in all directions getting further and further from the source of the expansion
-some matter will be heavier and travel at a slower speed, closer to the source of the explosion
-some matter will be lighter and travel at a greater speed, further from the source of the explosion
What is the Doppler effect?
if something that emits a wave moves whilst it is doing so (imagine a noisy motorbike coming towards you then going further away, emitting sound waves the whole time) then the wavelength of the sound will become shorter as it is moving towards you, increasing the frequency, and stretched as it is moving away, decreasing the frequency
How are the wavefronts spread out when an object emits waves whilst being stationary?
the wavefronts are spread out symmetrically
When a wave source moves relative to an observer, what will there be a change to?
there will be a change in the observed frequency and wavelength
What happens to the wavelengths and frequencies around the moving object and what is this change known as?
the wavelength of the waves IN FRONT of the source DECREASES and the frequency INCREASES
the wavelength of the waves BEHIND the source INCREASES and the frequency DECREASES
this is known as the DOPPLER EFFECT or DOPPLER SHIFT
What is the equation for the Doppler Shift?
change in wavelength (m) / reference wavelength (m)
velocity of a galaxy (m/s) /
speed of light (m/s)
What can the Doppler Shift equation be used for?
the Doppler Shift equation can be used to calculate the velocity of a galaxy if its wavelength can be measured and compared to a reference wavelength
Does the Doppler Shift have units?
NO
How does red-shift work?
the further away a galaxy is the greater its red-shift and hence the faster it is moving away from us
Does the Doppler Effect affect all types of waves?
YES including light
What is the definition of red-shift?
the idea of the wavelength of light appearing to increase when the source moves away from a observer
If an object moves towards an observer and the wavelength of light decreases, what is it known as?
BLUESHIFT
as the light moves towards the blue end of the spectrum
