Chapter 3

These are the Q&A from Chapter 3 – Astronomy Through The Ages. Again, if you notice anything wrong, just add a post!

1. Give one reason why Aristotle believed that the Earth is a globe rather than a flat plane.
Aristotle believed the Earth was a globe, because certain stars were either in different positions or not there at all, when he was stood somewhere else. E.g. The Pole Star would be higher up in Italy, but in Egypt the Pole star would be closer to the horizon.

2. What was the main contribution made by Copernicus to astronomical knowledge?
The main contribution made by Copernicus was his decision to place The Sun in the centre of the planetary system. This caused astronomical knowledge to change from a n Earth centred planetary system.

3. What did Johannes Kepler discover about the shapes of the orbits of the planets?
Johannes Kepler discovered that the ideas of perfectly circular orbits, which had been an anchor of astronomical knowledge, was in fact not true. Kepler discovered that the orbits of the Earth and the other planets were elliptical. However, he decided that the Sun was one focus and that there was another focus, which was empty.

4. Explain the main reason why Greenwich Observatory was founded in 1675.

Greenwich Observatory waGreenwich Observatorys founded in 1675 by express order of the King, Charles II. He wanted an up to date and accurate catalogue of the stars to help assist British Sea Navigators. Stars were used to help work out what longitude a ships was on, when out of sight of landmarks, and to judge the route to get back to land.

5. Herschel set out to determine the shape and form of the Galaxy. What was his main conclusion about this?
Herschel discovered reasonably accurately the shape and form of the Galaxy. He decided that it was a ‘cloven grindstone’ shape, however, that sometimes it likened to the shape of to fried eggs thrown together, back to back.

6. Explain how it was possible to work out the position of Neptune, in 1846, before the planet was actually seen.
Before it could even be seen, the existence and position of Neptune could be worked out by it’s own affects. Two Astronomers noticed how Uranus seemed to being pulled out of it’s orbit by some unknown force. They both decided that there had to be another Planet, further away from the than Uranus, pulling it of it’s predicted path. Using this idea, Neptune’s existence was known.

7. Why can a reflecting telescope be made to a larger aperture than a refractor?
A reflecting telescope can be made to a larger aperture than a refracting telescope because in a refracting telescope, because the lens can only be supported by the edge; the bigger it is, the more gravity pull there is on the centre of the lens. The reflecting telescope can have a larger aperture because it is supported by the whole side opposite it’s reflecting face.

8. What important discovery was made by Karl Jansky in 1931?
In 1931 Karl Jansky was using an improvised aerial to study ‘static’, when he suddenly found his aerial picking up long-wavelength radiation from the Milky Way. This was where Radio Astronomy began and is the branch of Astronomy that Jodrell Bank investigates.

9. Give two advantages and two disadvantages of positioning a telescope above the Earth’s atmosphere.
One advantage of a telescope above the Earth’s atmosphere is that there is no atmosphere in the way to hide anything. Another advantage is that there are no artificial light sources to disturb any equipment. This means the telescope will only pick up the stars.

An disadvantage is that it can be difficult and costly to transport materials up there, because they can’t be too big or heavy, and they need sufficient protection whilst transported. It is also very difficult to assemble. A second disadvantage is the health risk of working and living in a space. No one astronaut can stay up there forever, because there is a health risk. So many astronauts would be needed over a long time period and they all need to be specially trained. And it is expensive and difficult to get supplies up to those supervising the observatory.

10. Discuss some of the advantages of international co-operation in astronomy.
An advantage of international astronomical co-operation is that when there is a life-changing discovery, then it can be shared with everyone.
Another advantage is that certain data can be confirmed by different observatories around the world. E.g. If a planet suddenly looks pink instead of green, then different countries can be asked to confirm the sighting.
A third advantage is different data can be taken at the same time in different places to create a bigger picture of an event or an anomaly.


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