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Earth and Space
• The Big Bang Theory suggests that the universe began about 13.7 billion years ago with a violent explosion.
• This explosion may be the reason for the expansion of the universe. Scientists disagree about whether it will continue forever or may eventually cause the universe to collapse in on itself.
• Astronomers use the speed of light to measure distances in the universe. Therefore, the unit of distance in space is the light year which represents the distance travelled by light in one year, at the speed of 300 000 kilometres per second. It is a very long way.
• Radio telescopes like Australia’s Parkes Radio telescope collect radio waves from objects in space like stars and galaxies.
• The advantage of collecting radio signals from space is that this kind of electromagnetic radiation is not obstructed by clouds of dust like light energy is.
• Radio telescopes can operate all day even in cloudy weather whereas optical telescopes can only operate at night and where there are no clouds.
• Astronomers use infer-red waves or heat energy to study cooler places in the universe such as clouds of dust and gas which are star forming regions called nebula(e), faint stars and galaxies and also planets and moons of our solar system.
• Other forms of electromagnetic radiation used in the study of the universe are x-rays, gamma rays and ultra-violet energy. These radiations are collected in space by special detectors because they cannot penetrate Earth’s atmosphere.
• A galaxy consists of billions of stars. Ours is called the Milky Way.
• Stars create their energy from the nuclear fission reactions involving hydrogen gas being changed into helium gas.
• A star undergoes change overtime called a life cycle. Some large mass stars end their existence with a huge explosion called a supernova, which may result in a black hole.
• Our Sun will exist for about another 5 billion years....