P12: Red Shift Flashcards
The Doppler Effect
The change of wavelength (and frequency) of the waves from a moving source depending on whether they are in front of or behind the observer.
How does a sound change when the source is moving towards you?
> The sound waves get compressed.
The wavelengths get more frequent.
The pitch is higher.
How does a sound change when the source is moving away from you?
> The sound waves get spread out.
The wavelengths get less frequent.
The pitch is lower.
Red Shift
> When an object is moving away from us.
The wavelengths get more spread out.
This causes the spectrum of light to shift to the red side.
Blue Shift
> When an object is moving towards us.
The wavelengths get more squashed together.
This causes the spectrum of light to shift to the blue side.
The faster a star or galaxy is moving (relative to us) …
… The larger the red/blue shift.
Evidence for the expanding universe.
> The light from distant galaxies is red-shifted.
> The further the galaxy is from us, the bigger the red-shift is.
The Big Bang Theory
The theory that space, time and matter were all created in a massive explosion staring from a very small initial point and the universe has been expanding ever since.
The Steady State Theory
An outdated theory that proposed the galaxies were being pushed apart by ‘white holes’ that were leaking matter into the universe.
Cosmic Microwave Background Radiation
> Created as high energy gamma radiation after Big Bang.
Been travelling through space ever since.
As the universe expanded, its wavelengths stretched to longer wavelengths and now it it detected as microwave radiation.
Evidence for the Big Bang:
Cosmic Microwave Background Radiation- The BBT is the only way of explaining it.
The future of the universe if its density is less than a certain amount:
> The universe will expand forever.
The stars will die out.
The universe ill end in a Big Yawn.
The future of the universe if its density is more than a certain amount:
> The universe will stop expanding and do the reverse.
> The universe will end in a Big Crunch.
