Science Physics P1

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Ideas about the solar system
Our understanding of the solar system has changed over many centuries. Scientists such as Ptolemy, Copernicus and Galileo added their ideas to our changing understanding. We observe the universe using a variety of equipment, from telescopes to orbiters and landers. Models of the solar system

The planets and the Sun orbit the Earth in Ptolemy's model.
Our understanding of the universe has changed over time. Different civilisations have created different models to explain what the universe is and how the universe began. The Greek astronomer Ptolemy (c90-168AD) used measurements of the sky to create his geocentric model. This had the earth at the centre and all the planets and the sun orbiting around it. The geocentric model lasted a long time. It wasn’t until the mid 18th century that Nicolaus Copernicus (1473-1543) came up with a different model. His heliocentric theory put the sun at the centre if the universe. It was based on observations with the telescope – work pioneered by the Italian astronomer Galileo Galilei (1564-1642). Discovering new planets

As telescopes have improved scientists have discovered new planets. Copernicus’ model of the universe didn’t include Uranus, Neptune or the dwarf planet Pluto because telescopes at the time weren’t good enough to see them. Galileo

Galileo discovered the existane of moons
Galileo Galilei (1564-1642) was an Italian astronomer working at a time when all Scientists believed the earth was the centre of the Universe and all planets orbited it (the geocentric model). Using the newly invented telescope he discovered that Jupiter had four moons. As these moons were orbiting Jupiter itself, this showed that not everything orbited the Earth. Galileo’s findings put him into conflict with the Catholic Church as they believed the geocentric model. He spent a large amount of his life under house arrest as a result of his beliefs. Observing the universe

Distant stars and galaxies are too far away for us to reach. We cannot go to them to study them. So everything we know about distant stars and galaxies comes from analysing the radiation they produce. Telescopes are devices used to observe the universe. There are many different types and some are even sited in space. Optical telescopes

Optical telescopes observe visible light from space. Small ones allow amateurs to view the night sky relatively cheaply but there are very large optical telescopes sited around the world for professional astronomers to use. Optical telescopes on the ground have some disadvantages:

* they can only be used at night
* they cannot be used if the weather is poor or cloudy.
Other telescopes
Radio telescopes detect radio waves coming from space. Although they are usually very large and expensive, these telescopes have an advantage over optical telescopes. They can be used in bad weather because the radio waves are not blocked by clouds as they pass through the atmosphere. Radio telescopes can also be used in the daytime as well as at night. X-rays are partly blocked by the Earth's atmosphere and so X-ray telescopes need to be at high altitude or flown in balloons. Space telescopes

Objects in the universe emit other electromagnetic radiation such as infrared, X-rays and gamma rays. These are all blocked by the Earth's atmosphere, but can be detected by telescopes placed in orbit round the Earth. Telescopes in space can observe the whole sky and they can operate both night and day. However, they are difficult and expensive to launch and maintain. If anything goes wrong, only astronauts can fix them. Telescopes

We use a variety of telescopes to help us observe the Universe. Telescopes have developed over the years. They use mirrors and lenses to bend, magnify and focus the light. One type of lens used is called a converging lens. Converging lenses

A lens is transparent block that causes light to refract (changes the direction the light travels in). A converging lens...
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