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Solar systems, galaxies and the Universe OUR SUN is one of millions of stars that orbit the centre of… THE MILKY WAY, which is one of a billion galaxies that orbit AND move away from the centre of… THE UNIVERSE (Basically, everything in the universe orbits around something else)
The Earth & Beyond : The Seasons ( The Northern Hemisphere ) Tilted away from the Sun- Sun is low in the sky Tilted towards the Sun- Sun is high in the sky Long days Long nights Day and night the same length Day and night the same length Spring Summer Autumn Winter When it is Summer in the Northern Hemisphere, it is Winter in the Southern Hemisphere N S N S N S N S
Sunlight rays are slanted across the land Sunlight rays are almost directly on the land Why do countries close the equator not experience much change in climate from season to season?
The Earth’s surface gains most heat when the Sun is above the horizon for the most hours, and when it reaches the highest angle in the sky. This happens around JUNE 21 ST in the Northern hemisphere and DECEMEBER 21 ST in the Southern hemisphere. This midsummer day is called the SUMMER SOLSTICE. Change in Seasons
The WINTER SOLSTICE is when the Sun is at its lowest angle above the horizon and stays above the horizon for the fewest hours. Between the solstices there are two EQUINOX when the day length is equal to the night length. Change in Seasons
East- Sunrise West- Sunset June 21 st March 21 st and September 21 st Northern Hemisphere East West March 21 st Northern June 21 st December 21 st December 21 st September 21st Sunrise Sunset Choose the correct words from the box below to complete the diagram-
Nuclear Fusion It is possible for two hydrogen nuclei to join together to form a new nucleus containing 2 protons and 2 neutrons, a helium nucleus. Hydrogen converted to Helium In this process a little bit of mass is lost and reappears as a lot of energy (E = mc 2 ). The centre of the Sun is extremely hot (around 15 million degrees) and very dense. It is so hot that the atoms lose their electrons becoming bare nuclei. Usually, in cooler conditions nuclei would not get close enough to fuse, or join (electric forces push them apart), but with temperatures that are incredibly high, the nuclei can bang into one another so hard that they can actually fuse together and release enormous of energy.
Gravity - The attraction between two masses Name some objects which ‘experience’ gravity! The Earth The Moon The Sun Which of these has the most gravity? The bigger an object’s mass , the greater the effect of gravity The closer an object is to another object , the greater the effect of gravity
The bigger an object’s mass , the greater the effect of gravity The Moon walk- astronauts wore heavy boots because the effect of gravity is less on the Moon. The Moon is 1/80th the mass of the Earth and has a gravitational pull of 1/6th of the Earth
As the comet comes closer to the Sun its speed increases - a greater force must be acting to cause it to accelerate faster. The closer an object is to another object , the greater the effect of gravity
The Halley comet Edmond Halley (1656-1742), The Nucleus of the comet
Why do we have tides? The moon and the Sun cause the sea to have tides. This is because of the gravitational attraction between the Sun, moon and water in the sea. The moon has the biggest effect, as it is closer to the Earth.
The Spinning Nebula Flattens Because of the competing forces associated with gravity, gas pressure, and rotation, the nebula begins to flatten into a spinning pancake shape with a bulge at the centre.
Condensation of Protosun and Protoplanets As the nebula collapses further, gravity develops in other regions. These will become the Sun and planets, as well as their moons and other debris in the Solar System.
According to this theory, the Universe has always existed ; it had no beginning and will continue forever. Although the universe is expanding, it maintains its average density – steady-state – through the continuous creation of new matter.
Most cosmologists now reject the theory because it cannot explain background radiation or the observation that the appearance of the universe changes with time.
Cosmic Background Radiation - Whenever a telescope is aimed up into our night sky there seems to be a form of microwave radiation sensed in every direction. Supposedly this is energy left over from the early stages of the Big Bang.