P16- Waves and the universe Flashcards
What process occurs in stars?
Nuclear Fusion
Why do we know that our solar system is the result of a supernova?
Elements have been found which are heavier than Iron
How was the Sun formed?
Sun formed at the centre of a spinning cloud of dust, gas, and rock due to the force of gravitational attraction
Sun’s heat evaporated the ice and drove the gas away from the inner solar system. leaving rocks behind
Rocky planets formed near the Sun
Gas Giants formed further away
Minor planets orbit beyond the gas giants
What are the gas giant planets?
Jupiter
Saturn
Uranus
Neptun
What are the rocky planets?
Mercury
Venus
Earth
Mars
Where is the asteroid belt located?
Between Mars and Jupiter
What force pulls together the gas, rocks and dust?
Gravitational attraction
When the clouds merge together, they become a what?
Protostar
As the protostar becomes denser, what happens to the particles and temperature?
They speed up
Temperature increases
When the protostar becomes denser, what energy transfer occurs?
Gravitational Potential into thermal energy
What happens when the protostar becomes hot enough?
The Hydrogen nuclei fuse
What is released by nuclear fusion and what happens to the star?
Energy is released
This causes the star to get hotter, brighter and starts to shine
Some objects may form which are far too small to become stars. What happens to them?
They can be attracted to a protostar to become planets orbiting the star
Stars such as the Sun radiate energy because of Hydrogen fusion in the core. What are these called?
Main Sequence Stars`
How long can main sequence stars maintain their energy output for?
Millions of years
How does radiation such as gamma radiation flow out from the core?
Steadily, in all directions
Why are stars stable?
Forces within it are balanced
Inwards force of gravity
Outwards force of radiation
These forces stay in equilibrium until most of the H nuclei have been fused to He nuclei
What is the heaviest known natural element and what is its half life?
Uranium - 4.5 Billion years
What has happened to elements heavier than Uranium?
They have decayed
What happens to stars smaller in size than our Sun?
They become a red giant
What happens to stars larger in size than our Sun?
They become a red supergiant
What happens to a red giant?
They become a white dwarf then a black dwarf?
What happens to a red supergiant?
They explode (die) as a supernova
What happens after a supernova?
A neutron star or black hole is formed, depending on its mass
Why can’t elements heavier than Iron be formed via nuclear fusion?
It requires too much energy
Around how old is the Sun?
5 Billion years old
In what shape does the Earth orbit the sun?
Circular
In what shape do most other planets orbit the Sun?
Elliptical
Give an example of a natural satellite?
The Moon
What shape is the Moon’s orbit?
Circular
Describe centripetal force in terms of the solar system
The force of gravity acting on a planet from the Sun, acts towards the centre of the Sun.
This force is the resultant force on the planet because no other forces act on it.
This is an example of centripetal force because it acts towards the centre of the circle
What is changed by centripetal force?
A planet’s velocity
What is true about the direction of motion of any planet?
In a circular orbit, it is at right angles to the direction of the force of gravity on it.
In which direction does a planet in a circular orbit experience acceleration? Why?
Towards the centre of the circle
The resultant force on it acts towards the centre of the circle
Explain why the speed of a planet in a circular orbit does not change.
The force on it is at right angles to its direction of motion
No work is done by the force on the planet
Kinetic energy and speed of the planet do not change
What happens to satellites which orbit too close to the Earth? Why?
They gradually lose speed
Atmospheric drag of Earth’s upper atmosphere.
What will happen when a satellite loses speed?
It will gradually spiral inwards until it hits the Earth
A satellite in a circular orbit above the Earth’s atmosphere moves around the Earth at a constant height above the surface. True or False?
True
What must happen for a satellite to stay in an orbit of a particular radius?
It has to move at a particular speed
The same is true for a planet orbiting the Sun in a circular motion.
The further a planet is from the Sun, means what?
The less speed it needs to travel at to stay in a circular orbit
The longer the planet takes to make a full orbit
Is the speed of a satellite in orbit changes, what must happen?
The radius of the orbit must change
At what distance do communications satellites often orbit at?
36,000 km
Describe the orbit of communications satellites
36,000km above the surface of the Earth
Orbits in the same direction as the Earth’s rotation
Geostationary - They stay above the same place.
Uses of monitoring satellites?
They are fitted with TV cameras so:
Weather forecasting
Monitoring the environment
Describe the orbit of monitoring satellites
Lower than geostationary satellites
Orbits the Earth once every two to three hours
What galaxy is our solar system found in?
The milky way
What can be used to split light into the colours of its spectrum?
A glass prism
What is red shift?
The increase of the wavelengths of the light emitted by galaxies moving away
What is the name of the shift of a galaxy moving towards you?
Blue shift
In 1929, what did an astronomer discover, and who was he?
Edwin Hubble
Discovered:
Light from distant galaxies were red-shifted
The further a galaxy is, the larger its red shift
What did the astronomer in 1929 conclude?
Distant galaxies are moving away from the Earth
The greater the distance a galaxy is from Earth, the greater the speed at which it is receding
Describe the Big Bang Theory?
A theory which states that the universe has been forever expanding after exploding suddenly, from a very small and extremely hot and dense region.
What was created in the Big Bang?
Space, Time and Matter
Describe the Steady State Theory
A theory which states that the galaxies are being pushed apart by the matter entering the universe through “white holes” (the opposite of black holes)
Until what year was the Steady State Theory widely accepted?
1965
What evidence is there for the Big Bang?
High energy radiation is thought to have been emitted by the Big Bang
As the universe has been expanding, the radiation would have stretched into low level radiation
Experiments were formulated to detect this radiation.
In 1965, what was concluded?
The existence of CMBR (Cosmic Microwave Background Radiation)
This could only be explained by the Big Bang Theory
What is CMBR?
High energy gamma radiation which has stretched into Microwaves with the expansion of the universe.
What do astronomers call the missing mass of the universe? Why?
Dark matter because it cannot be seen
What does dark matter’s presence mean?
The average density of the universe is much larger than it would be if dark matter did not exist
What would happen if the universe’s density was below a particular amount?
It will expand forever. The stars will die out, as will everything else. This is called the “Big Yawn”
What would happen if the universe’s density was more than a particular amount?
The universe will stop expanding and fall back on itself - “The Big Crunch”
What have astronomers concluded about the universe’s future?
It could be that the universe is heading for a Big Ride then a Big Yawn
What is dark energy?
The name given to the energy thought to be pushing the galaxies apart
Why can’t gravity be used to explain the acceleration/expansion of the universe?
It is an attractive force
