Theories about the Universe Flashcards
the big bang theory
states that the whole Universe started out as a tiny particle/point of concentrated energy about 13.8 billion years ago
the universe expanded from this point and is still expanding today
when matter expanded outwards huge amounts of ionising radiation were released
(1920s)
steady state theory
the universe has always existed
is it expanding, and new matter is being created continuously as it expands
(1948 NOT OLDER, but not supported as much)
Doppler effect
wavelengths in front of a moving source become compressed and shorten (higher frequencies), while the wavelengths behind get longer
red shift
(light from a star doesn’t contain all the wavelengths of the EM spectrum, elements in the star absorb some, producing dark lines in the spectrum - spectral lines)
when objects that emit light (e.g. galaxies) move away from us, the light they emit is a lower frequency
this causes it to be ‘red-shifted’ - the spectral lines are shifted further to the red end of the spectrum compared with a stationary object observed on Earth
the faster the galaxy is moving away from us, the greater the red shift
How does red shift support the theory that the universe is expanding?
galaxies further away from us have a greater red shift
this means that they are moving faster, suggesting that the universe is expanding
CMB radiation
cosmic microwave background radiation
microwave signals can be detected coming from all over the sky
temperature of -270C
(1964, radio telescope)
How does the existence of CMBR support the big bang theory?
as the universe expands the wavelength of the radiation emitted by the big bang theory increases
although it started as higher frequency/hot and intense radiation it is now only detectable as microwave radiation
it has cooled over time, and is now very weak with a temperature of -270C (close to absolute 0)
it is also detected in all directions
this supports the theory that the universe started with a big bang, and provides a time frame (because of the COOL TEMPERATURE) of almost 14 billion years
How has the advancement of technology provided more evidence?
-modern technology can sense EM frequencies that the eye can’t see, allowing more observations to be made
- lots of wavelengths of EM radiation don’t penetrate the atmosphere
- telescopes based above the atmosphere (e.g. Hubble space telescope) can sense these wavelengths
- they are also not affected by weather or light levels
Describe the cosmic microwave background radiation (CMB) and explain why the Big Bang theory is the currently accepted model for the beginning of the Universe. [4]
the CMBR is detected by radio telescopes and comes from all over the sky
the big bang theory says this radiation was released at the beginning of the universe
red shift supports both the big bang and solid state theories, but the CMB only supports the big bang theory
the big bang theory is accepted because it has the most evidence supporting it
What evidence is there to support the big bang and the steady state theories? [1]
the universe is expanding supports both; red shift
Why is the CMB radiation such important evidence? [3]
correct temperature to suggest Universe started in a big bang around 14 billion years ago
Distances in space are sometimes measured in light years. Galaxy NGC 55 is 7.08 million light years away. The Pinwheel galaxy is 21 million light years away.
Explain the similarities and differences you would expect in the light from these galaxies as a result of their movement. [4]
- the universe is expanding
- so the galaxies are moving away from us and the light from them will be red shifted
- more distant galaxies are moving away from us faster, so their light will have more red shift
- the pinwheel galaxy is further away than NGC 55, so light from it will have a greater red shift
