Our place in the universe Flashcards
Explain how the expansion of the space causes cosmological red-shift.
As radiation travel through space the wavelength stretches with expanding space.
The cosmological red-shift is greater for galaxies further away from Earth. Describe how the model of an expanding universe explains this observation.
light has been travelling for longer/ so more time for stretching of waves/Universe has changed more /(one mark for Hubble type argument)
Give an example of assumptions made when using radar.
Distance asteroid or Earth moves during time delay is very small and can be disregarded./ the velocity of light is unchanged on reflection/ other sensible suggestion/’velocity of signal constant’ insufficient for mark.
The radar-ranging method is impractical for measuring the distance or velocity of a star such as Sirius which lies about 7 light years from Earth. Suggest two reasons why this is so.
weaker reflected signal long delay in detection or other sensible. Do not accept stars moving.
Explain why background microwave radiation being the same intensity in all directions of the Universe is evidence that the Early Universe was approximately the same temperature.
The radiation is a remnant of era of recombination(accept remnant of big bag.) present distribution reflects earlier distribution.
About three hundred thousand years after the Big Bang, the universe was at a temperature of roughly 3000k. The photons emitted at the time are now observed to be at a temperature of around 3k.Calculate the ratio of the energy of the 3k photons/3000k photons.Calculate the ratio of the wavelength of the 3k photons/3000k photons.
ratio = 1/1000ratio = 1000
What does 1/Ho give a value of?
An estimate of all the time passed since the galaxies were close together.
Suggest one reason why the age of the Universe may be larger than the value 1/Ho.
-The Universe did not begin with galaxies.-variation of Hubble constant/expansion rate-variation in data
