P7 Flashcards
What did Ptolemy suggest about the universe?
That the Earth was at the centre
What did the Copernicus suggest about the universe?
The Sun is the centre and the planets orbit it
What did Galileo contribute to theories about the universe?
- he used telescopes to support Copernicus’s suggestions about the Sun
- suggested that moons orbit planets
Explain why for a stable orbit, the radius of orbit must change if the speed changes
- at higher speeds, the objet requires a greater centripetal force
- this can be done by increasing gravitational force
- which requires a smaller orbit-radius
Describe the Steady State theory
Is a theory that says that the universe has always existed but is expanding and creating matter to counteract the loss in density
Describe the Big Bang Theory
Is a theory that states that the universe expanded from a very small dense point about 14 billion years ago
What is red-shift?
A perceived increase in wavelength of light due to the source moving away from the observer
What did scientists observed provide evidence that the universe is expanding at an ever faster rate?
- observed supernovae
- before this expansion was expected to occur more slowly
- this is caused by gravitational forces
What does CMBR stand for, and how does it provide evidence for The Big Bang?
- cosmic microwave background radiation
- believe that it originated from the radiation produces in big bang
How does CMBR support the expansion of the universe?
- thought that gamma rays released in big bang
- expansion has stretched this, resulting in the microwaves in present today
Describe the transition of the star from the nebula stage to the main sequence
- nebula increases in size until it is pulled in due to gravity. This causes GPE to be turned into KE
- collisions cause this kinetic energy to turn into thermal energy
- eventually the nebula will become dense enough to start fusion
What occurs in the stage when a star is in main sequence?
- fusion releases energy
- this energy balances out with the gravitational potential energy
- star is in equilibrium
What happen when the star reaches the red giant stage?
- the star begins to fuse helium
- causes star to expand
Why are telescopes located outside the earths atmosphere?
- earths atmosphere absorbs many electromagnetic waves
- light pollution makes images less clear
- telescopes operate day and night
What is the difficulty of telescopes outside the atmosphere?
- difficult to maintain
- difficult to be brought down (very expensive)
