p2 part 2

p2 part 2

1. space

   • comets
     • have an elliptical orbit
       • inside mercury orbit, beyond pluto's orbit
         • solar winds cause tails
           • blows comets dust particles in all directions
             • no tails far away cos too far to be affected by solar winds
   • meteors
     • made from grains of dust
       • they burn up when they pass through the earths atmosphere
         • they heat up the air around them
           • which glows and the streak is known as a 'shooting star'
   • black holes
     • formed where large stars used to be
       • can't see cos light cant escape from it
         • large mass, very small size
           • high density
   • moons orbit planets
     • planets orbit stars
       • due to the centripetal force acting upon them
         • CF acts towards the centre of the circular orbit
         • gravitational attraction is the source of the CF
   • light years
     • distance light travels in one year
       • 300000km/s
       • light from sun takes 8 mins
         • light from nearest star, proxima centurai takes 4.22 years
   • exploring planets
     • unmanned probes
       • go where humans cant, into deadly conditions
         • cost less and don't put astronauts life at risk
           • but have to be reliable (no way of easily repairing)
     • manned probes
       • have to have food, water and o2
         • more expensive
     • astronauts
       • suits need
         • a dark visor
         • pressurised suit and oxygen supply
       • when travelling, they are subjected to lower gravitational forces than on earth

2. space

   • asteroids
     • mini planets/asteroids
       • most orbit between mars and jupiter
         • asteroid belt
     • orbit the sun
     • they are large rocks left over from the formation of the solar system (big bang)
   • all bodies in space, inc. planets, forming when clouds of gas and dust collapsed together due to gravitational forces of attraction
     • the mass of an object determines its gravitational force
       • asteroids have a relatively low mass compared to jupiter
         • jupiters gravitational force prevents asteroids from joining together to form another planet
   • origin of the moon
     • scientists believe our moon was a result of the collision between 2 planets in the same orbit
     • the iron core of the other planet melted and joined with earths core, less dense rocks began to orbit and they join together to form our moon
     • evidence for this idea
       • the av. density of earth is 5500kg/m3 while the moon is only 3300kg/m3
         • there is no iron in the moon
           • moon has same o2 composition as earth but rocks on mars/ meteorites have different
   • asteroids
     • geologists examine evidence to support theory that asteroids have collided with earth
       • near to an (asteroid) crater impact, large quantities of iridium are found. (a metal uncommon in earths crust, but common in meteorites)
         • many fossils are found below the layer of iridium, but few found above it
           • tsunamis have disturbed the fossil layers, carrying some fossil fragments up to 300km inland
   • comets orbit
     • as comets passes close to the sun, the ice melts and solar winds blow dust into comets tail (which always points away from the sun)
       • scientists monitor and plot the paths of comets and other near-earth objects, NEO's
         • the speed of a comet increases as it approaches the sun and decreases as it gets further away. this is because of changing gravitational attraction.
   • neo's
     • if an neo is on a collision course w/ earth, we could send a rocket to explode near it which means its course will change and miss earth

3. the big bang theory

   • almost all of the galaxies are moving away from each other w/ further galaxies moving faster

4. red shift

   • when a light source is moving away from an observer, its wavelength appears to increase which shifts light slightly towards the red end of the spectrum- red shift
   • when scientists look at light from the sun, there is a pattern of lines across the spectrum...this same pattern is observed when they look at light from distant stars but it is closer to the red end of the spectrum.
     • scientists can use this info to age the universe
       • the more red-shift, the further the star from us
         • tells us, that distant galaxies are moving away from us
           • the further the galaxy, the faster its moving
   • our sun contains helium. we know because of black lines where helium has absorbed light.
   • positions of lines have changed due to the doppler effect.
     • their wavelengths have increased (and freq. decreased)

5. moon models

   • galileo observed jupiters 4 moons
     • this confirmed that not everything orbits earth and supported Copernicus' idea that planets orbit the sun
   • roman catholic church did not support Galileo's model as they believed that earth was at centre of universe and took a long time before this was accepted
   • in 17th century, newton worked on his theory of universal gravitation which suggested that all bodies attract one another
   • today, we believe that gravitational collapse is prevented because the universe is constantly expanding as a result of the big bang.

6. a nebula is a swirling cloud of gas and dust

   • nebulas are clouds, pulled together by gravity and as the spinning ball of gas starts to get hot, it glows (this protostar cannot be seen because of the dust cloud)
     • gravity causes the star to become smaller, hotter and brighter and after millions of years, the core temp. is hot enough for nuclear fission to take place. as hydrogen nuclei join together, to form helium nuclei, energy is released and the star continues to shine while there is enough hydrogen
       • small stars shine for longer cos they have less hydrogen
         • what happens at the end of a stars life depends on its size

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