space

• lifecycle of a star with similar mass to the sun

  clouds of gas and dust, protostar, main sequence star, red giant, white dwarf, black dwarf
• lifecycle of a star with larger mass than the sun

  clouds of gas and dust, protostar, main sequence star, red super giant, supernova, black hole or neutron star
• how are clouds of gas and dust formed?

  attracted together by gravity, towards the centre of mass of the solar system
• protostars

  heats up due to increased pressure of collapsing clouds of gas and dust. Becomes a main sequence star once fusion of hydrogen begins
• main sequence stars

  stays the same size as the force from gravity balanced by radiation pressure. Fuses elements up to and including iron. Very stable due to abundance of hydrogen.
• red giant

  similar mass to our sun
• red super giant

  larger mass than our sun
• how is a white dwarf and black dwarf formed?

  white dwarf is formed by a 'nova'. The outer layers of the star drift away leaving only the core, forming a black dwarf.
• what is a supernova?


  an explosion which scatters heavy elements throughout the universe. It fuses elements heavier than iron.
• black hole


  has a very large mass
• neutron star


  has a large mass
• the doppler effect when any source of waves is moving towards you


  wavelength of the waves is shortened and the frequency is higher
• the doppler effect when any source of waves is moving away from you


  the wavelength of the waves is longer and the frequency is lower
• what is red-shift?


  the effect that light from distant galaxies is observed to have an increased wavelength and a decreased frequency
• what does red-shift show?

  distant galaxies are moving further away from us
• how is red-shift observed?

  the increased wavelength of the light is observed by seeing that the dark lines on the spectrum are closer to the red end
• what is Hubble's Law?

  the further away the galaxy the larger the red-shift (increase in wavelength) observed in the light coming from the galaxy
• what does Hubble's Law show?

  more distant galaxies are moving faster. The velocity the galaxy is moving away at is directly proportional to the distance to it.
• what does the Big Bang Theory show?

  that the universe began from a very small region that was extremely hot and dense. The increase in wavelength of light from distance galaxies (red-shift) shows that the furthest galaxies are moving away from the Milky Way fastest, which shows that the universe is expanding, suggesting that at some point in time all matter started at the same point
• what is the centripetal force?

  the resultant force on an object acting towards the centre of a circle causing circular motion
• how does the centripetal force work?

  there is always a real force which provideds the centripetal force. When an object moves in a circle it continuously accelerates towards the centre of the circle. This acceleration changes the direction of motion of the body, not its speed. The resultant force causing this acceleration is always directed towards the centre of the circle.
• how do planetary orbits work?

  the sun's gravitational pull provides the force that keeps planets moving in their orbit. The force is directed towards the centre of the circle. The planet accelerates because its velocity is constantly changing due to its constantly changing direction. No work is done because the force is at a right angle to the motion. So no energy is transferred to or from the planet, so its kinetic energy and speed remain unchanged.
• shape of the planets' orbits

  the Earth's orbit is almost circular whereas most of the other planets orbit the Sun on orbits that are elliptical
• the importance of speed for the centripetal force

  if the launch speed is too slow the satellite falls to the surface. If the launch speed is too high, the satellite flies into space. At the correct speed the satellite moves around the Earth in a circular orbit at a constant height and speed.