Astronomy (topic 7) Flashcards
What is the heliocentric theory?
A theory which states the sun Is at the centre of the universe
What is the geocentric theory?
the theory where the earth is at the centre of the universe.
What centripetal force?
a force which acts on a body moving in a circular path and is directed towards the centre around which the body is moving. eg the moon when orbiting the earth.
What is the steady state theory?
The density of the universe stays the same yet the universe is expanding and therefore matter is always being created.
What is the big ban theory/
An explosion occurred which releases a lot of energy cause the universe to expand, as the energy slowed down it formed mass. it is supported by background radiation.
What is the difference between the sequence our sun went through and that of a black hole?
1) after a proto star is made, our sun followed into the main sequence whereas a bigger sun would become a massive main sequence
2) The black hole would then become a red super giant, then a super nova and then a back hole
what is a comet?
a small lump of ice orbiting the sun
what ae asteroids?
a small lump of rock orbiting the sun
What are geostationary satellites?
They are satellites which stay at one point over earth and are used for broadcasting
What is the definition of a satellite?
a celestial body orbiting a planet due to is gravitational pull
What are low earth satellites used for?
weather forecasting while orbiting the earth
What is the Doppler effect?
When an object moving away emits radiation, the wavelength increases because it emits radiation at the same rate but the crests are more spread out because it has travelled further in that time, stretching it out. Therefore the frequency decrease.
This also mean if it is moving towards you the wavelength decreases and frequency increases.
Why is the big bang theory better than the steady state theory?
Because it is supported by background radiation which are microwaves coming from every direction in space. The Big Bang theory says this is energy created at the beginning of the universe, just after the Big Bang, and that has been travelling through space ever since. This cant support the SST because that theory suggests that there was never a big bang or sudden appearance of energy.
What is the red shift?
When objects such as a galaxies are moving away from us, the light they emit is red shifted. This means that the wavelengths from when detected on earth will be stretched. the spectral lines will be shifted further to the red end of the spectrum, compared to a stationary object observed on earth. Also, the faster the galaxy is moving away from us, the more these lines will be shifted to the red end of the spectrum.
How does the red shift prove that the universe is expanding?
Because the furthest galaxies show more red shift than those nearer to us, this suggests that the universe it expanding.
