Astronomy Flashcards
Order of the solar system
Sun
Mercury
Venus
Earth
Mars
Asteroid belt
Jupiter
Saturn
Uranus
Neptune
Weight =
Mass (kg) x gravitational field strength (N)
How was Ptolemy model of the solar system different to the one of the modern day
He placed Earth at the centre of the universe
Who changed Ptolemy’s model to having the sun at the centre of solar system
Nicolas Copernicus
What is Newton’s first law
An object travelling g at a certain velocity will continue to travel at that velocity unless acted upon by a resultant force
Define solar system
The collection of eight planets and their moons in orbit around the sun
What was ptolemys model called
The geocentric model (2nd century AD)
Who invented the telescope
Galileo Galilei (1564-1642)
When was Galileo’s telescope invented
1604
What was Copernicus’ model of the solar system
Heliocentric circles positioned the sun at the centre of the universe with the planets orbiting around it in circular paths, modified by epicycles & at uniform speeds.
What did Galileo see with his new invention
He was able to look at the moon, observe a supernova, verify the phases of Venus and discover sunspots.
His discoveries proved the copernican system.
What is the only force acting on the moon
Gravity
What are the uses of artificial satellites
Photography
communication
weather forecasting
GPS
spying
Wi-Fi
service
What are polar orbits used for
Weather forecasting
What are Geostationary orbits used for
Communications
What is the difference etc between a geostationary orbit and a polar orbit
The satellites in polar orbits travel very close to the earth (200km above sea level) so they must travel at very high speeds (nearly 8000m/s) to stay in orbit.
The satellites in geostationary orbits take about 24hours to orbit the earth. These orbits are much higher than polar orbits (36000km) so the satellites travel slower (3km/s)
What shape are the orbits of comets
Elliptical
What is a comet
Made from rocky material, dust and ice
Orbits the sun
How is weight affected by different planets
Weight is proportional to the gravitational field strength of the planet
What happens to the speed and the velocity of a planet in circular orbit
The speed remains constant but the velocity changes as the direction is changing
Why doesn’t the moon fall down
Gravity is the only force that acts on the moon.
The moon will always accelerate towards the centre of the Earth (centripetal force)
The force of gravity is at right angles to the motion and remains this way so the moon moves in a curved path
What causes an object in orbit to accelerate
When an object moves in a circle at a constant speed, direction constantly changes.
A change in direction causes a change in velocity. This is because velocity is a vector quantity.
The change in velocity results in acceleration, so an object moving in a circle is accelerating even though its speed may be constant.
However an object will only accelerate if a resultant force acts on it (eg. Centripetal force)
Explain red-shift
Light from a star does not contain all the wavelengths of the electromagnetic spectrum (they absorb some of the wavelengths) so absorption lines appear.
Red-shift is when the wavelengths of light are stretched and so the absorption lines move closer to the red end of the spectrum.
This proves that the universe is expanding
What is the Steady State Theory
Says that the universe has always existed and the universe is expanding and constantly CREATING MATTER AS THE UNIVERSE EXPANDS
