cosmos [07] galileo's telescope

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Galileo Galilee

GALILEAN HELIOCENTRISM


Galileo Galilee

In Roman Catholic Italy, the Copernican hypothesis of the solar system was not a popular philosophy. The Church authorities were still upholding the concepts of Aristotle and Ptolemy that the Earth is the centre of the universe, and that the planets and the sun were in perfect circular motion around the Earth. The Copernican system was not at all welcome.However, as early as in the 1590s, Galileo Galilee (1564-1642) was already a follower of the Copernican system.


The telescope

One of the greatest things Galileo had done that the other astronomers did not was the introduction of the telescope into astronomy.The telescope was not invented by Galileo. It had long been in existence as early as the 13th century. In 1608, the Dutch spectacle maker Hans Lippershey began to make telescope that attracted attention. In 1909, Galileo heard of the invention. He constructed his own telescope and improved it to 30 time magnification.


First eyes on the sky

While Kepler was busy with his Mars project, Galileo Galilei began to use his telescope to observe the heavens in 1609.

This was the first time in history when a human being set his eye on the universe through a telescope.

Many of the new things revealed by the invention were extremely disturbing. There were craters on a supposedly perfectly spherical moon; many moons circling Jupiter and many of them did not conform to orbital patterns predicted by the Ptolemy approaches.


The satellites of Jupiter

Jupiter was the fifth planet from the Sun and the largest planet in the solar system.

Jupiter has many moons (satellites) - about 62 already known. At the time of Galileo, only four largest satellites were found observable.

Io was among one of the four largest satellites which became the centre of attention.

Callisto

Io

Ganymede

Europa

Jupiter Sizes not to scale


The satellites moved around earth

In the Ptolemaic system, the planets of should be orbiting around earth like Jupiter did.

Jupiter

Orbital round the earthEarth – Centre of universe

Io – one of Jupiter’s planets


The satellites moved around of Jupiter

However, Galileo found that the planet was actually orbiting around Jupiter just like the moon around Earth. The phenomenon could not be explained by a circular orbit about Earth, but could be easily understood if the satellite orbits Jupiter instead.

This was an important findings because it utterly contradicts to what Ptolemy expected.

Jupiter

Orbitals round the earth

Earth – Centre of universe

Io – orbits round Jupiter’s


Observation of Venus phases

When Galileo turned his telescope to Venus, another planet like Earth, he made another surprising finding.

Ptolemy's geocentric model predicted that Venus would show only the new Moon and crescent phases as it orbits Earth on its epicycles.

Venus

Earth

Orbit of Venus


Venus orbits the Sun instead of the Earth

Kepler's modified the Copernican heliocentric model and predicted that Venus would show all the phases of the Moon as Venus and Earth both orbit the Sun.

Galileo confirmed that Venus went through phases just like the moon of the Earth. This was possible only if Venus is orbiting round the sun instead of the earth.

Venus

Earth

Orbit of Venus


Promoting Heliocentrism

On the basis of these observational discoveries, Galileo began to teach the modified Copernican heliocentric model of the solar system as the correct one.

He even used Kepler's laws to calculate orbital parameters for the orbits of the satellites revolving around Jupiter.

However Scripture said that the Sun revolved around the Earth, and the Holy Office of the Inquisition found Galileo guilty of heresy for saying otherwise.


Heliocentrism as Heresy

The Church placed Copernicus's book on its Index of Restricted Books and tried Galileo before the Inquisition. Galileo was forced to recant the heliocentric theory and was placed under house arrest for the last eight years of his life.


References

The Evolving Universe. Donald Goldsmith. The Benjamin/Cummings Publishing Company. Inc. 1985.

Wikipedia.

Exploration of the Universe. George O. Abell. Saunders College Publishing,1982.

Astronomy: The Evolving Universe. Michael Zeilik. Harper & Row, Publishers. 1982.

The Universe of Galileo & Newton. William Bixby. American Heritage Publishing Co., Inc. 1964.


ISAAC NEWTONTo be continued in Part 8

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cosmos [07] galileo's telescope

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