P1 - The Universe Flashcards
Which states of matter does sound travel through the fastest and slowest?
Faster in solids than liquids
Faster in liquids than gases
What causes sound waves?
Vibrating objects
Which type of wave is sound?
Longitudinal
Why do echoes happen?
They are reflected sound waves
What else can sound waves do?
Diffract and refract
What effect does changing the frequency of a sound wave?
The higher the frequency, the higher the pitch
What effect does changing the amplitude of a sound wave have?
The higher the amplitude, the louder the sound
How is the universe changing?
It is expanding and all galaxies are moving away from each other
How do we know that the universe is expanding?
The light from other galaxies is red-shifted
Describe red-shift
Different chemicals absorb different frequencies of light so each element produces a specific set of dark lines at the frequencies that it absorbs in the visible spectrum
The dark lines in light from distant galaxies are shifted towards the red side of the spectrum
This is red-shift
What causes red-shift?
The doppler effect
Describe the doppler effect
The frequency of a source moving towards you will seem higher so the wavelength will seem shorter and frequency will be higher
The opposite is true for an object moving away from you
What type of wave does the doppler effect occur in?
Both transverse and longitudinal
What effect does changing the distance to a galaxy have in red-shift and why?
The further away the galaxy, the greater the red-shift because galaxies further away are moving away from us faster than nearer ones
What are the 2 theories for the origin of the universe?
Big bang theory
Steady state theory
Describe the big bang theory
All matter and energy in the universe must have been compressed into a very small space and then it exploded from that point and started expanding
Describe the steady state theory
The universe has always existed as it does now and always will do
The universe is expanding because matter is being created in the spaces as the universe expands
Why is the big bang theory accepted over the steady state theory?
It is the only theory that explains the cosmic microwave background radiation
What is cosmic microwave background radiation?
Low frequency electromagnetic radiation coming from all parts of the universe
How does big band theory explain the cosmic microwave background radiation?
Just after the big bang the universe was very hot so everything in the universe emitted high frequency radiation
As the universe expanded it cooled so the radiation dropped in frequency to microwaves
What are the 2 problems with the big bang theory?
There are observations the theory can’t explain (universe’s expansion is increasing when it should be slowing)
No explanation for what caused the explosion
