Topic Three - Waves And The Universe Flashcards
What is a galaxy
A group of millions of stars held together by gravity
What is a planet
A natural object in space that orbits a star
What is the universe
All the stars,galaxies and space itself
What do moons orbit
Planets
What does SETI mean and what is it
Search for ExtraTerrestrial Intelligence
We are constantly beaming radio, tv and radar into space for any passing aliens to detect
- Scientists on the SETI project are looking for radio signals coming to earth from outer space that could have been sent by aliens
- SETI has been going on for about 50 years but they’ve not found anything
- Scientists are now looking for possible laser signals from outer space
What is another way of searching for life
Robots and probes can collect data and samples
Why is it important for telescopes to be located outside the earths atmosphere
- outside the atmosphere,light waves from space are not reflected or refracted by clouds and dust or even by movements of air in the atmosphere ~ clearer and brighter image
- some wavelengths of electromagnet radiation are absorbed by the atmosphere
~ telescopes detecting these types of radiation have to be located outside the earths atmosphere
~ if they we’re put on earth they would not detect anything
Life cycle of stars
1) stars form from clouds of dust and gas called NEBULAS
2) - the force of gravity makes the gas and dust spiral in together
- gravitational energy has been changed into heat energy, so the temperature rises
3) - when the temperature is high enough, hydrogen nuclei fuse together to make helium nuclei
- when they fuse they give out huge amounts of energy - a star is born
- the star then enters a long stable period
- the pressure from the heat pushing outwards is balanced by the force of gravity pulling everything inwards
- in this stable period, it’s called a MAIN SEQUENCE STAR and it can last for several billion years
4) - eventually the hydrogen in the core begins to run out
- the star then swells into a RED GIANT
5) - the star then becomes unstable
- it ejects it’s outer layer of dust and gas as a planetary nebula
6) - this leaves behind a hot, dense solid core - a WHITE DWARF, which just cools down and eventually fades
Red shift
If a source of light is moving away from us, then it’s wavelength will be longer and it’s frequency lower than we expect, I.e. It’s light is shifted towards the red end of the spectrum
- light from other galaxies is red shifted - this shows that galaxies are moving away from us
- this tells us that the universe is expanding
Big Bang theory
The whole universe and all the matter in it started out as a tiny point of concentrated energy about 13.5 billion years ago
The universe expanded from this point and is still expanded
The theory also claims that a huge amount of radiation was left behind after the Big Bang
Steady state
This alternative theory proposed in 1948 suggested that the universe has always existed and is expanding
New matter is continuously created within the universe as it expands
Big Bang theory vs steady state theory
- both theories state that the universe is expanding, with new matter being created all the time
~ the red shift in the light from other galaxies can be used to support both theories - the Big Bang theory predicts that the radiation released after the Big Bang should still be detectable as ‘cosmic microwave background radiation’
~ in 1964, 2 radio astronomers detected microwave signals coming from all over the sky-supporting the Big Bang theory
~ the steady state theory cannot explain CMB radiation - there is more supporting evidence for the Big Bang theory - accepted by most astronomers today
Doppler effect
A sound with a high frequency has a high pitch
A sound with a low frequency has a low pitch
The sound waves in front of a moving vehicle are compressed - frequency is higher - pitch is higher
The sound waves behind a moving vehicle are stretched - frequency is lower - pitch is lower
Therefore …
As an ambulance comes towards you, you hear a high pitched siren
As an ambulance moves away from you, you hear a low pitched siren
