1. Natural Sciences Grade 7
Term 4: Planet Earth and Beyond
Historical development of astronomy
(ppt 2)

2. Topic 3 Historical development of astronomy
Modern developments
Natural Sciences - Grade 7

3. Natural Sciences - Grade 7
Guess what this is……
Look at the image and identify the picture.
Find out if the learners know the definition of the following words:
narrow; flimsy; shaky
Establish if they know what the function of a telescope is.
Natural Sciences - Grade 7

4. Nicolaus Copernicus [1473 – 1543]
Renaissance scientist.
In 1514 he claimed that the Earth revolves around the Sun.
Scientists and religious uproars started.
In 1543 he used Maths geometrical techniques when he discussed the following about his heliocentric model:
- Earth’s centre is not the Universe’s centre.
- Stars do not move.
- Every planet rotates around the Sun.
- Celestial bodies do not all revolve around a
single point.
- The motion of the Earth causes the Sun to
move.
Picture of Nicolaus Copernicus:
Discoveries have been made for centuries.
Simple instruments were used to measure the positions of objects in the sky.
Mathematics was used to give an explanation about their predictions as they calculated.
Natural Sciences - Grade 7

5. Natural Sciences - Grade 7
Galileo Galilei [1564 – 1642]
He used science to gain more information about the solar system.
He was not the inventor of the telescope, but he was the first scientist who directed it to the sky.
He used it to study the planets and the stars.
He discovered the Milky Way and saw that it was made up of millions of stars; Jupiter’s four biggest moons. After he had constructed an improved 20x refractor telescope; Venus went through phases that was similar to lunar phases.
Pictures of Galileo Galilei: :
Natural Sciences - Grade 7

6. Natural Sciences - Grade 7
Galileo Galilei [1564 – 1642]
He observed and explained sunspots.
The stars were all at different distances from the Earth.
When he observed the Moon, he discovered that it
had valleys, craters and mountains.
He is named the father of observational astronomy.
He spent his life under house arrest due to heresy.
He is the author of Two New Sciences [presently it is
called Kinematics and strength of materials].
Pictures of Galileo Galilei: :
Natural Sciences - Grade 7

7. The Orion Constellation
Galileo Galilei viewed the Pleiades [also known as the Seven Sisters and Messier 45] through a telescope.
He discovered that it is an open star cluster in a constellation.
The Pleiades’ nine brightest stars are named [Maia, Sterope, Alcyone, Celaeno, Electra and Merope for the Seven Sisters of the Greek mythology.
More pictures of the Seven Sisters:
Natural Sciences - Grade 7

8. Natural Sciences - Grade 7
Johannes Kepler [1571 – 1630]
He was a German Mathematician.
He observed Mars’ orbit.
He formulated the laws of the planets’ movement in 1609.
He discovered that all the planets moved in elliptical [oval shaped] orbits.
He made a suggestion that Galileo’s telescope work could be used to confirm the theory of Nicolaus Copernicus.
There was no distinction between astrology and astronomy in his time.
Pictures of Johannes Kepler:
Natural Sciences - Grade 7

9. Natural Sciences - Grade 7
Isaac Newton [1642 – 1727]
His gravity law was a very important discovery.
He explained how gravity kept:
- the Earth in its orbit around the Sun.
- the Moon in its orbit around the Earth.
- objects in the solar system to keep their positions to
the Sun.
It started when he noticed an apple falling from a tree; all objects with mass attract each other.
Research work: Why can we walk and jump on Earth? [Gravity is suppose to hold us].
Pictures of Isaac Newton:
Natural Sciences - Grade 7

10. Natural Sciences - Grade 7
Isaac Newton [1642 – 1727]
In 1666, at the age of 25, he discovered that when white light passes through a prism, it spreads out into a spectrum of seven colours.
The gravity force between two objects become smaller as the distance between the two objects become bigger.
He published a famous article called Principia in 1687 in which calculations were shown that Nicolaus Copernicus was correct.
The Law of Gravitation is universal [planets, stars, galaxies and Moon movements can be predicted by this law].
Research work: Why can we walk and jump on Earth? [Gravity is suppose to hold us].
Pictures of Isaac Newton:
Natural Sciences - Grade 7