1. In Europe 500 years ago, old books had more authority than direct observations The old books claimed that the Earth was rough and raw, and the heavens were perfect

2.  To the naked eye, the Moon is just a bright object in the sky with some vague patterns  With the help of the telescope much more detail can be seen

3. Telescopes showed the rough surface of the Moon The Moon has ‘mountains’ that create dark shadows at sunrise and sunset - just like the mountains on Earth Observations clashed with the authority of ancient books

4. Sunspots were another observed imperfection in the heavens - on the face of the Sun itself This is a modern image of the Sun made with ultraviolet light, using spacecraft cameras The telescopes of 400 years ago were also good enough to make sunspots visible

5. The authority of old books stated that everything in the heavens is in orbit around the Earth - in accordance with a geocentric model of the Universe But telescopes revealed new wanderers in the sky - always close to Jupiter but changing their positions, night by night They seem to be moons of Jupiter, and not in orbit around the Earth

6. Venus, like the Moon, has ‘phases’ when seen from the Earth Just as for the Moon, the sunlit side of Venus sometimes faces towards us and sometimes away from us Observation of the phases falsifies the geocentric model of the Solar System

7. This is a prediction of the phases of Venus that is based on the idea that the Sun is at the centre of the Solar System The Sun-centred model is the heliocentric model The heliocentric model as used in this diagram agrees with observations from Earth Observations of the phases of Venus support the heliocentric model

8. Slide 1 - Fekete Csaba Slide 2 - NASA/JPL Slide 3 - NASA/JPL Slide 4 - ESA/NASA/SOHO Slide 5 - NASA/JPL/Malin Space Science Systems Slide 6 - NASA/JPL Slide 7 - The Project Gutenberg