How did Galileos observation of Jupiter and venus support Copernicus' model?

Answer 1

Galileo's discoveries with the telescope sowed doubts about the ancient Ptolemaic model which had the Earth at the centre. First, Jupiter's moons orbited round Jupiter and not the Earth, the first objects that had been discovered that were not orbiting the Earth. Secondly the discovery of the phases of Venus raised doubt about the Ptolemaic model, particularly the gibbous phase when, we now know, Venus is round behind the Sun as seen from Earth. In the Ptolemaic model Venus never goes behind

the Sun (as seen from Earth) and the gibbous phase cannot happen.

By implying in the title of his book 'Dialogue of the two world systems' that there were only two models in contention, those of Ptolemy and Copernicus, Galielo insinuated that if the Ptolemaic model was incorrect the Copernican system must be correct. This was logically flawed because at the time there were two other systems in the public domain that both explained Venus's phases. These were the models of Tycho, which was geocentric, and finally Kepler's which was heliocentric.

Of these four, Kepler's was eventually accepted by everyone after Newton's theoretical discoveries showed that Kepler's elliptical orbits for the planets agreed with the new theory of dynamics.

Answer 2

Galileo's discoveries with the telescope did not support Copernicus's theory directly but they showed problems with the ancient Ptolemaic theory. The moons of Jupiter were the first things discovered that clearly did not orbit the Earth, while the range of Venus's phases was not fully explained by the Ptolemaic theory.

However Tycho Brahe had a theory that explained Venus's phases properly, while still having the Earth at the centre.

In the end the theory that gained acceptance was Kepler's, which also had the Sun at the centre. So Galielo was right all along, although there was no way of proving it during his lifetime.

Answer 3

Galileo saw the four largest moons of Jupiter in orbit around the planet, proving that the Ptolemaic system was not simpler - the solar system was not geocentric (the planets and the sun did not orbit around the earth).

As far as the observations of Venus go, Galileo saw that Venus displayed phases very much like our moon. Now, according to the Ptolemaic system, Venus could only display a crescent phase because its epicycle put it always in between Earth and the sun. The Copernican system put everything rotating around the sun, and in this way it explained the phases of Venus.

Think of it this way, if Venus is always in between the sun and the earth, how can we ever see it completely lit up, like a full moon? The sun is always on the other side of it, so Venus must at some point go on the other side of the sun.

Answer 4

Galileo saw the four largest moons of Jupiter in orbit around the planet, proving that the Ptolemaic system was not simpler - the solar system was not geocentric (the planets and the sun did not orbit around the earth).

As far as the observations of Venus go, Galileo saw that Venus displayed phases very much like our moon. Now, according to the Ptolemaic system, Venus could only display a crescent phase because its epicycle put it always in between Earth and the sun. The Copernican system put everything rotating around the sun, and in this way it explained the phases of Venus.

Think of it this way, if Venus is always in between the sun and the earth, how can we ever see it completely lit up, like a full moon? The sun is always on the other side of it, so Venus must at some point go on the other side of the sun.

Answer 5

Galileo saw the four largest moons of Jupiter in orbit around the planet, proving that the Ptolemaic system was not simpler - the solar system was not geocentric (the planets and the sun did not orbit around the earth).

As far as the observations of Venus go, Galileo saw that Venus displayed phases very much like our moon. Now, according to the Ptolemaic system, Venus could only display a crescent phase because its epicycle put it always in between Earth and the sun. The Copernican system put everything rotating around the sun, and in this way it explained the phases of Venus.

Think of it this way, if Venus is always in between the sun and the earth, how can we ever see it completely lit up, like a full moon? The sun is always on the other side of it, so Venus must at some point go on the other side of the sun.

Answer 6

Galileo was the first to observe the planets with a telescope and he made important discoveries.
Looking at Jupiter, he discovered four moons orbiting it. Up until then nothing had been found that was not orbiting the Earth, as they thought at that time. So it was a wake-up call indicating possible doubts about the old Ptolemaic system.

Looking at Venus, he discovered the phases of Venus as it moves in its orbit. The Ptolemaic model explains the crescent phase but it fails to account for the gibbous phase because in the Ptolemaic model Venus never goes round behind the Sun. So this was a definite fault with the Ptolemaic system.

Neither of the above were conclusive 'proofs' of the Copernican system, because Tycho Brahe then came up with a model that had Mercury and Venus orbiting the Sun, while the Sun and the other planets still orbited the Earth. This explained all the phases of Venus while still placing the Earth at the centre.

So nothing that Galileo discovered was a 'proof' of the Copernian system and in fact when Kepler came up with the model we use today it used the novel idea of elliptical orbits. The Sun was at the centre and this is the only part of Copernicus's model that has survived the test of time, with all the scientific discoveries that have been made since then.

Answer 7

Galileo's discoveries with the telescope did not support Copernicus's theory directly but they showed problems with the ancient Ptolemaic theory. The moons of Jupiter were the first things discovered that clearly did not orbit the Earth, while the range of Venus's phases was not fully explained by the Ptolemaic theory.

However Tycho Brahe had a theory that explained Venus's phases properly, while still having the Earth at the centre.

In the end the theory that gained acceptance was Kepler's, which also had the Sun at the centre. So Galielo was right all along, although there was no way of proving it during his lifetime.