Scene 9
p. 66
sunspots -
Sunspots are dark areas of irregular shape on the surface of the Sun. In the dominant Aristotelian cosmology, the heavens were thought to be perfect and unchanging. A spot that comes and goes on the Sun would mean that there is change in the heavens. Given this theoretical predisposition, the difficulty of observing the Sun, and the cyclic nature of spots, it is little wonder that records of sunspots are almost non-existent in Europe before the seventeenth century. A very large spot seen for no less than eight days in 807 was simply interpreted as a passage of Mercury in front of the Sun. Other mentions of spots seen on the Sun were ignored by the astronomers and philosophers. In 1607 Johannes Kepler wished to observe a predicted transit of Mercury across the Sun's disk, and on the appointed day he projected the Sun's image through a small hole in the roof of his house (a camera obscura) and did indeed observe a black spot that he interpreted to be Mercury. Had he been able to follow up on his observation the next day, he would still have seen the spot. Since he knew that Mercury takes only a few hours to cross the Sun's disk during one of its infrequent transits, he would have known that what he observed could not have been Mercury.
The scientific study of sunspots in the West began after the telescope had been brought into astronomy in 1609. Although there is still some controversy about when and by whom sunspots were first observed through the telescope, we can say that Galileo and Thomas Harriot were the first, around the end of 1610; that Johannes and David Fabricius and Christoph Scheiner first observed them in March 1611, and that Johannes Fabricius was the first to publish on them. His book, De Maculis in Sole Observatis ("On the Spots Observed in the Sun") appeared in the autumn of 1611, but it remained unknown to the other observers for some time.
In the meantime, Galileo had shown sunspots to a number of people in Rome during his triumphant visit there in the spring of 1611. But although some of his corespondents began making regular observations a few months later, Galileo himself did not undertake a study of sunspots until April 1612.
In the winter of 1611-12, when Galileo received a copy of Scheiner's tract from Welser along with a request for his comments, he was ill, and what little energy he had he was devoting to the publication of his Discourse on Bodies in Water. When, however, that book was at the printer's, in April 1612, he turned his attention to sunspots with the help of his protégé Benedetto Castelli, who was in Florence at the time. It was Castelli who developed the method of projecting the Sun's image through the telescope, a technique that made it possible to study the Sun in detail even when it was high in the sky.
trousseau -
French; the personal possessions of a bride usually including clothes, accessories, and household linens and wares
floating bodies -
In 1612 Galileo published a Discourse on Floating Bodies, attacking Aristotelian physics.
This is the famous Principle of Archimedes:
A body immersed, or partially immersed, in a fluid is thereby acted on by an upward force of buoyancy equal to the weight of the fluid displaced.
This means that the weight of a boat, for example, must be equal to the weight of a volume of water equal to the volume of the part of the boat below the water line.
Galileo and Archimedes’ Principle
Galileo fully appreciated how important Archimedes’ Principle was in really understanding falling bodies of different weights, falling through media of different densities. In fact, he used it to great effect to demolish Aristotle’s assertion that a body ten times heavier will fall ten times faster, irrespective of the medium. Of course, this is all a little unfair to Aristotle, since Archimedes enunciated the Principle about a century after Aristotle died. The main point, which Galileo fully appreciated, is that the weight of a body, which is the force causing the constant downward acceleration, must be reduced by the buoyancy force, so the actual total downward force is the weight of the body minus the weight of an equal volume of the fluid.
p. 69
treatise on sunpots by Fabricius -
Johannes Fabricius, (born Jan. 8, 1587, Resterhafe, Neth.—died c. 1615), Dutch astronomer who may have been the first observer of sunspots (1610/1611) and was the first to publish information on such observations. He did so in his Narratio de maculis in sole observatis et apparente earum cum sole conversione (1611; “Account of Spots Observed on the Sun and of Their Apparent Rotation with the Sun”). The son of the astronomer David Fabricius, Johannes used a camera obscura as well as a telescope in his study of the Sun.
p. 74
Feast of the Immaculate Conception -
holy days of obligation, in the Roman Catholic Church, religious feast days on which Catholics must attend mass and refrain from unnecessary work. Although all Sundays are sanctified in this way, the term holy days usually refers to other feasts that must be observed in the same manner as Sunday. The number of such days has varied greatly, since bishops had the right to institute new feasts for their dioceses until the 17th century. Pope Urban VIII then limited the number of holy days throughout the church to 36. The feast of the Immaculate Conception is celebrated on December 8.
Excerpted from Encyclopedia Britannica and the Galileo Project
sunspots -
Sunspots are dark areas of irregular shape on the surface of the Sun. In the dominant Aristotelian cosmology, the heavens were thought to be perfect and unchanging. A spot that comes and goes on the Sun would mean that there is change in the heavens. Given this theoretical predisposition, the difficulty of observing the Sun, and the cyclic nature of spots, it is little wonder that records of sunspots are almost non-existent in Europe before the seventeenth century. A very large spot seen for no less than eight days in 807 was simply interpreted as a passage of Mercury in front of the Sun. Other mentions of spots seen on the Sun were ignored by the astronomers and philosophers. In 1607 Johannes Kepler wished to observe a predicted transit of Mercury across the Sun's disk, and on the appointed day he projected the Sun's image through a small hole in the roof of his house (a camera obscura) and did indeed observe a black spot that he interpreted to be Mercury. Had he been able to follow up on his observation the next day, he would still have seen the spot. Since he knew that Mercury takes only a few hours to cross the Sun's disk during one of its infrequent transits, he would have known that what he observed could not have been Mercury.
The scientific study of sunspots in the West began after the telescope had been brought into astronomy in 1609. Although there is still some controversy about when and by whom sunspots were first observed through the telescope, we can say that Galileo and Thomas Harriot were the first, around the end of 1610; that Johannes and David Fabricius and Christoph Scheiner first observed them in March 1611, and that Johannes Fabricius was the first to publish on them. His book, De Maculis in Sole Observatis ("On the Spots Observed in the Sun") appeared in the autumn of 1611, but it remained unknown to the other observers for some time.
In the meantime, Galileo had shown sunspots to a number of people in Rome during his triumphant visit there in the spring of 1611. But although some of his corespondents began making regular observations a few months later, Galileo himself did not undertake a study of sunspots until April 1612.
In the winter of 1611-12, when Galileo received a copy of Scheiner's tract from Welser along with a request for his comments, he was ill, and what little energy he had he was devoting to the publication of his Discourse on Bodies in Water. When, however, that book was at the printer's, in April 1612, he turned his attention to sunspots with the help of his protégé Benedetto Castelli, who was in Florence at the time. It was Castelli who developed the method of projecting the Sun's image through the telescope, a technique that made it possible to study the Sun in detail even when it was high in the sky.
trousseau -
French; the personal possessions of a bride usually including clothes, accessories, and household linens and wares
floating bodies -
In 1612 Galileo published a Discourse on Floating Bodies, attacking Aristotelian physics.
This is the famous Principle of Archimedes:
A body immersed, or partially immersed, in a fluid is thereby acted on by an upward force of buoyancy equal to the weight of the fluid displaced.
This means that the weight of a boat, for example, must be equal to the weight of a volume of water equal to the volume of the part of the boat below the water line.
Galileo and Archimedes’ Principle
Galileo fully appreciated how important Archimedes’ Principle was in really understanding falling bodies of different weights, falling through media of different densities. In fact, he used it to great effect to demolish Aristotle’s assertion that a body ten times heavier will fall ten times faster, irrespective of the medium. Of course, this is all a little unfair to Aristotle, since Archimedes enunciated the Principle about a century after Aristotle died. The main point, which Galileo fully appreciated, is that the weight of a body, which is the force causing the constant downward acceleration, must be reduced by the buoyancy force, so the actual total downward force is the weight of the body minus the weight of an equal volume of the fluid.
p. 69
treatise on sunpots by Fabricius -
Johannes Fabricius, (born Jan. 8, 1587, Resterhafe, Neth.—died c. 1615), Dutch astronomer who may have been the first observer of sunspots (1610/1611) and was the first to publish information on such observations. He did so in his Narratio de maculis in sole observatis et apparente earum cum sole conversione (1611; “Account of Spots Observed on the Sun and of Their Apparent Rotation with the Sun”). The son of the astronomer David Fabricius, Johannes used a camera obscura as well as a telescope in his study of the Sun.
p. 74
Feast of the Immaculate Conception -
holy days of obligation, in the Roman Catholic Church, religious feast days on which Catholics must attend mass and refrain from unnecessary work. Although all Sundays are sanctified in this way, the term holy days usually refers to other feasts that must be observed in the same manner as Sunday. The number of such days has varied greatly, since bishops had the right to institute new feasts for their dioceses until the 17th century. Pope Urban VIII then limited the number of holy days throughout the church to 36. The feast of the Immaculate Conception is celebrated on December 8.
Excerpted from Encyclopedia Britannica and the Galileo Project