There was another man, working at around the same time as Kepler, who made an even greater contribution to the dawn of modern astronomy and single-handedly pioneered modern mathematical physics. This was a man who laid down virtually all the groundwork for Newton and his name was Galileo Galilei (usually referred to only as Galileo). He has been called by some as the father of both modern astronomy and modern physics and certainly his role as a pivotal figure in the development of both these sciences is beyond question. On top of this he was also the pioneer of modern experimental scientific method.
It was Galileo that finally provided proof of the
Copernican theory, and thus confirming Kepler's work to be
correct.
He also had time to lay down the foundations of correct
understanding of
dynamics and of gravity.
But we are getting ahead of ourselves here.
Before Galileo began so much of his ground breaking work in astronomy an invention was to come along and help him out, that invention was the telescope and in the arms of Galileo it was the instrument that was to revolutionise the science of astronomy, allowing Galileo to peer into the heavens and see at a magnification many times what any human had seen before.
The discovery of the telescope is usually credited to Hans Lippershey in 1608, although there is some evidence that there was one or possibly even two people before him to invent a telescope, but this evidence remains very much inconclusive, so we shall not break from tradition here!
Galileo and AstronomySo back to Galileo, in 1609 (about the same time as Kepler was about to publish his first two laws) from only simple reports of this new invention, Galileo, using his skills, was able to construct a vastly superior model to Lippershey's telescope and is said to be the first to use the refracting telescope. Some of his early observations included:
- The Moon was not smooth but actually covered in mountains and craters.
- The planets were discs not points of light.
- The Milky Way was composed of an enormous number of stars (agreeing with Copernicus' idea of the universe being much vaster than previously thought, also destroying the only argument for the Taychoic system, by providing reason for why, in a heliocentric system there would appear to be no stellar parallax).
As a collective what these observations did was to raise the
issue of the credibility of the Ptolemaic system, how could
Aristotle and Ptolemy's work be trusted to be correct when there
was so much of the universe they didn't know?
Galileo's early observations convinced him of the accuracy of the
Copernican system and he began to argue strongly for it, basing
his arguments on his observations with his telescope.
In this work there are 3 further observations in particular that deserve special mention:
His observations of the Moons of Jupiter
Galileo used the so called Galilean moons to prove a major argument against the Copernican system was incorrect.The argument suggested that given the moon orbited the Earth, if the Earth then orbited the Sun, the Moon would be left behind. With the discovery of the moons around Jupiter it was clear that a planet could orbit a body without leaving behind any moons that were in turn orbiting it.
Observations of Sunspots
| With the observation of Sunspots not only did Galileo prove that the Sun was not perfect (remember at the time the held ideas continued to be Aristotle's theory that God made all the celestial bodies and so they must be perfect) but he also observed that these imperfections were moving. This implied that the Sun was rotating on an axis which meant it was more feasible for the earth to be rotating (the idea of the Earth rotating in the Copernican model was one of the greatest arguments against it as such rotation could not be felt). | |
Galileo's view of Sunspots From Galileo's own sketches |
A 2001 view of Sunspots Courtesy of SOHO/MDI |
Observations of the Phases of Venus
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Galileo's most important achievement in astronomy was
demonstrating that the planet Venus, as seen from the Earth, went
through a complete set of phases just like the Moon, which he
first noticed in 1610. This wasn't just ground breaking it was earth shattering, it provided conclusive evidence that was consistent with the Copernican model but not with the Ptolemaic model. How? Well if the Earth was the centre of the Universe then due to the position of the Earth, Venus and the Sun, we would only ever see Venus in crescent phases because Venus would always be between the Earth and the Sun (see Ptolemaic system below). |
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The Ptolemaic System |
The Copernican System |
In 1632 Galileo published his work Dialogue Concerning The
Two Greatest World Systems. This latest work, supporting the
Copernican model and proving the geocentric system wrong was not
received well by the Roman Catholic Church! Indeed they were
incensed by this work as it was contrary to scripture, contrary
to the very foundations of religion. Of course a century before
Copernicus himself and delayed the publication of his work for
fear of the reprisal of the church, and it appears that his fear
was justified.
In 1633 Galileo was summoned to Rome and quickly convicted of
hearsay, he was forced to make a public confession of his error
in judgement and withdraw his support for the Copernican model,
he was also forbidden to publish any further work and sentenced to life
imprisonment. Due to his age, however, he was permitted to serve
his sentence under house arrest.
| As a point of interest Galileo also discovered what he called the 'ears' of Saturn (of course we now know these to be rings but Galileo's telescope was not powerful enough to determine this). |
A chronology of how Galileo saw the rings of Saturn |
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| All images are original Galileo sketches |