Part 4: Development of the Telescope

Section 4
Question 31-40
Complete the notes below.
Write ONE WORD ONLY for each answer.

The development of the telescope

Roger Bacon (1200s) • His invention assisted 31 …………………………….. With sight problems when they were reading Lipperhey • 1680: he put concave and convex lenses together to create the telescope • The small telescope was first use in 32 ……………………………… Galileo • 1609: he tried out different lenses to improve the telescope • He started 33 ………………………. of the lenses he needed The venetian government hoped to use this instrument for the 34 ……………………………..

Galileo’s astronomical discoveries • The Moon – he discovered its surface was mountainous – he worker out the height of the mountains by identifying spots that were 35 ……………….. – he created 36 ……………………………….. of the moon’s surface • Jupiter – realized that the bodies orbiting Jupiter were not 37 ……………………………….. But moons. Further development • Scientists discovered that increasing the telescope’s 38 ………………………….. Improved its power. • 1670: Hevelius built a telescope 43 meters long. – poor results:  the telescope will would move with the 39 ……………………………… – the problem was solved by attaching it to a 40 ……………………………

Key

1. researchers
2. theatre/ theater
3. production
4. army
5. bright
6. charts
7. stars
8. length
9. wind
10. building

Transcript

Lecturer: Good morning. Today’s lecture is about the development of the telescope up until the end of the 17th century.

Lecturer: We can trace the telescope’s earliest form back to the 1200s. History records Roger Bacon as possibly the first to invent a magnifying glass. The principal use of his invention was for reading. This proved to be a benefit mostly for researchers who, until then, had been forced to give up working while still relatively young because of impaired vision.

Lecturer: In 1608, a Dutch astronomer called Lieberhei discovered that if convex and concave lenses were put together, they created a magnifying glass through which things at a distance could be seen. He created a miniature telescope. It was so small that, initially, people took it to the theater for a better view of the stage.

Lecturer: Galileo found out about Lieberhei’s invention in the spring of 1609 and immediately set about improving it. Galileo experimented with different lenses, combining a weak convex lens with a strong concave lens. He discovered that this intensified the strength of the instrument. Unfortunately, the lenses the opticians were making for glasses were unsatisfactory for what Galileo wanted to do, as they did not have powerful enough magnification. Galileo, therefore, decided that, to solve his problem, he would have to start the production of his own lenses. Eventually, he achieved a magnification about nine times more than you could see with the naked eye, an enormous improvement over everything else on the market.

Lecturer: Galileo then decided to approach the Senate of Venice to demonstrate the improved instrument. Many senators were eager to try the new telescope and climbed the highest bell towers in Venice to look through the glass at ships far out to sea. The government of Venice were impressed by his invention’s obvious potential, and envisioned the advantages this eyeglass could have for the army.

Lecturer: His first major astronomical discovery with the telescope was that the moon’s surface was mountainous, and not a perfect sphere as it had always been assumed. During the lunar cycle of 28 days, he found that the shadows seemed to vary with the light. Galileo also figured out how to estimate the altitude of the mountains on the moon by looking for bright spots in the dark areas. Galileo looked for the spots when it was a half moon and, with geometry, was able to calculate the elevation of the mountains. From these calculations, he was able to draw charts of the terrain and show the altitudes of the mountains.

Lecturer: In 1610, Galileo’s next major discovery was regarding Jupiter. Using a magnification telescope 20 times the strength of his previous ones, he looked at Jupiter on successive nights. His main observation was a trio of what initially seemed to be small stars close to Jupiter. However, by the 15th night, he realized that they were going around the planet in a daily orbit. And that, in fact, they were moons, not stars. And three days later, he saw a fourth one. This discovery showed how important a telescope was for astronomers. They would now be able to see celestial objects that could not previously be seen by the naked eye.

Lecturer: In the later 1600s, scientists started to make a stronger telescope, revealing the galaxy. Scientists realized that when they increased the length of the telescope, the intensity of magnification improved significantly. One such telescope was created in 1656 and magnified over 100 times. It had the incredible length of 4 meters.

Lecturer: Telescopes continued to become longer over the next few years. And, in fact, the astronomer, Haverius, built one in 1670 that was 43 meters long. However, these telescopes were soon to prove useless for accurate observation, because the slightest wind caused the instrument to shift.

Lecturer: Finally, in 1675, astronomers abandoned the tube telescope and instead mounted the telescope on a building. Telescopes like this were called aerial telescopes. Scientists hoped that the stability of the mount would decrease the frustration when observing stars.

Lecturer: Well, that’s about it for today, and so I…