Galileo backed Copernicus despite data

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Galileo backed Copernicus despite data

#1  Postby RichardPrins » Mar 05, 2010 11:56 pm

Galileo backed Copernicus despite data
Katharine Sanderson wrote:Stars viewed through early telescopes suggested that Earth stood still.

Galileo Galilei was right: Earth moves around the Sun, just as Nicolaus Copernicus said it did in 1543. But had Galileo followed the results of his observations to their logical conclusion, he should have backed another system — the Tychonic view that Earth didn't move, and that everything else circled around it and the Sun, as developed by Danish astronomer Tycho Brahe in the sixteenth century.

This is the conclusion that Christopher Graney, a physicist at Jefferson Community and Technical College in Louisville, Kentucky, came to after reading manuscripts from another astronomer who was active in the late sixteenth and early seventeenth century, at the same time as Galileo.

Graney suggested in 2008 that Galileo's observations of stars were actually diffraction patterns called Airy disks — patterns of concentric circles that arise when light from a point source, such as a star, passes through a hole. Diffraction hadn't been discovered in Galileo's time, so he was unaware of the phenomenon and believed what his eyes, or his telescope, were telling him and used the observations to estimate the size and distance of stars. As a result, he got the distances of the stars too short by a factor of thousands (see 'Galileo duped by diffraction').

After Graney realized that Airy disks had tricked Galileo, he decided to search for contemporaries of Galileo who might have seen similar things with their instruments. "There had to be someone who had a good telescope other than Galileo," says Graney.

That someone was German astronomer Simon Marius, most famous for naming the moons of Jupiter (Io, Europa, Ganymede and Callisto) and claiming to have detected them just days before Galileo.

Like Galileo, Marius mistook Airy disks as representing the stars themselves, says Graney in a paper soon to be published in the journal Physics in Perspective1.

Whereas Galileo stuck to his Copernican system view, Marius's analysis of starry data led him to very different conclusions, says Graney, who made the finding after reading a German translation of Marius's book Mundus Iovialis (The Jovian World), published in 1614.

Close call
According to Graney, Marius concluded that his observations showed that the stars were too close to Earth to satisfy the Copernican world view — which says that the stars lie at a huge distance from Earth, and so would appear as starry pinpricks to any observer. The Copernican view was shared by others: stars would be seen as points if the telescope's lens was darkened by smoke, wrote Dutch astronomer Christiaan Huygens in his book Systema saturnium, published in 1659, 17 years after Galileo's death.

Instead, Marius said that the observation of the stars as disks confirmed the Tychonic system, which put Earth, unmoving, at the centre of the system with the Moon and Sun orbiting it. The planets Mercury, Venus, Mars, Jupiter and Saturn all then orbit the Sun and the stars lie just beyond these planets in a fixed sphere.

"Marius's reasoning was more rigorous than Galileo's," says Graney. "In fact, Galileo's own data would lead to the same conclusion, had he followed it rigorously." So why did Galileo stick to his Copernican views?

"Galileo was strongly committed to Copernicanism. That he chose not to include arguments against it is not very surprising, although according to modern scientific standards he probably should have done so," says Rienk Vermij, a historian of science from the University of Oklahoma in Norman. Vermij adds that the different world views were hotly debated for many years, and that this argument about the size and distribution of the stars was only one among many. "It is not evident that this argument should be decisive, any more than other arguments," says Vermij.

Graney can't say why Galileo stuck to what turned out to be the right view, in spite of the observations. "Galileo was a very smart guy. I wonder if he didn't have more of this worked out in his head that he never got around to putting down on paper," he says.

But in a world in which, according to Vermij, the Tychonic system was regarded as a serious rival of the Copernican system, Marius's conclusions seem reasonable. "You have to hand it to Simon Marius for looking at the data and pursuing it through to its logical conclusion," says Graney.

References: 1. Graney, C. Phys. Perspect. (in the press).
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Re: Galileo backed Copernicus despite data

#2  Postby klazmon » Mar 06, 2010 10:13 am

Interesting stuff about the Airy disk possibility but it seems a bit suspect. The scopes they had in those days had really bad chromatic aberration. They couldn't possibly see an Airy disk unless they viewed through a monochrome filter.
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Re: Galileo backed Copernicus despite data

#3  Postby Darwinsbulldog » Mar 07, 2010 1:22 am

I think Galileo was interested in parsimony and simplicity. The pre-Copernican system was just ugly. Even though the data available at the time did not differentiate cleanly between one theory and another, the Copernican theory had more aesthetic value, because of its beauty and simplicity . Such a sentiment is not invariably right, but a good rule of thumb guide that is right often enough to be useful. Galileo could have been wrong, of course, but in the future the better data vindicated him.
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Re: Galileo backed Copernicus despite data

#4  Postby klazmon » Mar 08, 2010 2:20 am

Darwinsbulldog wrote:I think Galileo was interested in parsimony and simplicity. The pre-Copernican system was just ugly. Even though the data available at the time did not differentiate cleanly between one theory and another, the Copernican theory had more aesthetic value, because of its beauty and simplicity . Such a sentiment is not invariably right, but a good rule of thumb guide that is right often enough to be useful. Galileo could have been wrong, of course, but in the future the better data vindicated him.



This is the same reasoning that led Kepler to back the Copernican theory. He also discovered in 1605 using Tycho's data that when viewed from a fixed point on the orbit of the planet Mars, that the Earth obeys his second law with respect to the apparent orbit of the Earth around the Sun. Also that the center of the Earth's orbit around the Sun lay between the Sun and what should be the equant. It is not possible to reconcile standard Tychonic theory theory with these two facts. As far as Kepler was concerned, Tychonic theory was dead in the water without radical ad hoc modifications. When Kepler published his Rudolphine tables in 1627, it was obvious to any astronomers that the Copernican system based on Kepler's laws was spot on the money.
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Re: Galileo backed Copernicus despite data

#5  Postby klazmon » Mar 08, 2010 2:21 am

:roll:
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Re: Galileo backed Copernicus despite data

#6  Postby baboo » Mar 24, 2010 6:17 pm

The comment about Kepler's work is correct--as presented by Kepler it could only be reconciled with the Copernican system. But Galileo rejected much of Kepler's work, insisting that orbits were circular, much like he rejected Kepler's (correct) explanation of the tides. The reality is that Galileo was hell-bent on supporting Copernicanism, regardless of the data. If we are honest with ourselves, we will be critical of those who are "right" for the wrong reasons. Galileo, unfortunately, fell into this category too often.

With regard to the issue of simplicity and parsimony, while scientists often cite this notion as a guide to theory-making, it is not a reliable nor objective criterion and should largely be dismissed as hooey. Most theories are only simple to the folks who dream them up, or to those who become enamored with them, and look complicated to everyone else. Anyone actually familiar with the Copernican system knows that it was extremely complicated, complete with epicycles and eccentrics. From a mathematical point of view, it was no better than the Ptolemaic system. In any case, the work reported here offers an important reminder that no direct evidence of Copernicanism existed in Galileo's lifetime, and that his singlemindedness--as admirable as it might have been--strayed far from the objective pursuits that we value in science today.
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Re: Galileo backed Copernicus despite data

#7  Postby MattHunX » Mar 25, 2010 10:52 am

Just so I understand this clearly, the order is Tycho>Copernicus>Galileo/Kepler/Marius. Never heard of Marius before only the correspondence between Kepler and Galileo.

I've also read that Kepler got the Moon's effect on the tides right, but Galileo dismissed those ideas as mere fiction. Well, every one of them was wrong about something in their conclusion. Only human.
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Re: Galileo backed Copernicus despite data

#8  Postby jeepyjay » Mar 26, 2010 7:46 pm

As regards dates, apart from Copernicus, they overlapped quite a bit.

Nicholas Copernicus 1473-1543
Tycho Brahe 1546-1601
Giordano Bruno 1548-1600
Thomas Harriot 1560-1621
Galileo Galilei 1564-1642
Johannes Kepler 1571-1630
Simon Marius 1573 -1624

Bruno and Harriot favoured an infinite universe.
Harriot was an astronomer interested in optics, so was unlikely to be fooled by Airy disks.
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Re: Galileo backed Copernicus despite data

#9  Postby MattHunX » Mar 26, 2010 8:27 pm

jeepyjay wrote:As regards dates, apart from Copernicus, they overlapped quite a bit.

Nicholas Copernicus 1473-1543
Tycho Brahe 1546-1601
Giordano Bruno 1548-1600
Thomas Harriot 1560-1621
Galileo Galilei 1564-1642
Johannes Kepler 1571-1630
Simon Marius 1573 -1624

Bruno and Harriot favoured an infinite universe.
Harriot was an astronomer interested in optics, so was unlikely to be fooled by Airy disks.


Damn! I messed up Tycho and Copernicus. Of course! :doh: I misremembered of the wiki.

Thanks! :cheers:
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Re: Galileo backed Copernicus despite data

#10  Postby Jakov » Apr 19, 2010 4:24 pm

The headline is misleading, it implies Galileo ignored /all/ the evidence and dogmatically backed one system.
What happened was Galileo was weighing up the evidence, he had seen the phases of Venus which might have convinced him of the heliocentric system.
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Re: Galileo backed Copernicus despite data

#11  Postby james1v » Apr 19, 2010 6:10 pm

:popcorn:
"When humans yield up the privilege of thinking, the last shadow of liberty quits the horizon". Thomas Paine.
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Re: Galileo backed Copernicus despite data

#12  Postby King David » Apr 19, 2010 10:56 pm

Jakov wrote:The headline is misleading, it implies Galileo ignored /all/ the evidence and dogmatically backed one system.
What happened was Galileo was weighing up the evidence, he had seen the phases of Venus which might have convinced him of the heliocentric system.


Yes I thought it was mostly the phases of Venus which led to the adoption of the Copernican system, not the size of stars or "airy discs" whatever that is. Then again I'm no science historian.
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Re: Galileo backed Copernicus despite data

#13  Postby rEvolutionist » Apr 19, 2010 11:04 pm

:popcorn:
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