To the modern reader, Aristotle's views on astronomy, as presented in Metaphysics, Physics, De Caelo (On the Heavens) and Simplicius' Commentary, will most likely seem very bizarre, as they are based more on a priori philosophical speculation than empirical observation. Although Aristotle acknowledged the importance of "scientific" astronomy - the study of the positions, distances and motions of the stars - he nevertheless treated astronomy in the abstract, linking it to his overall philosophical world picture. As a result, the modern distinction between physics and metaphysics is not present in Aristotle, and in order to fully appreciate him we must try to abandon this pre-conception. Aristotle argued that the universe is spherical and finite. Spherical, because that is the most perfect shape; finite, because it has a center, viz. the center of the earth, and a body with a center cannot be infinite. He believed that the earth, too, is a sphere. It is relatively small compared to the stars, and in contrast to the celestial bodies, always at rest. For one of his proofs of this latter point, he referred to an empirically testable fact: if the earth were in motion, an observer on it would see the fixed stars as moving, just as he now observes the planets as moving, that is from a stationary earth. However, since this is not the case, the earth must be at rest. To prove that the earth is a sphere, he produced the argument that all earthly substances move towards the center, and thus would eventually have to form a sphere. He also used evidence based on observation. If the earth were not spherical, lunar eclipses would not show segments with a curved outline. Furthermore, when one travels northward or southward, one does not see the same stars at night, nor do they occupy the same positions in the sky. (De Caelo, Book II, chapter 14) That the celestial bodies must also be spherical in shape, can be determined by observation. In the case of the stars, Aristotle argued that they would have to be spherical, as this shape, which is the most perfect, allows them to retain their positions. (De Caelo, Book II, chapter 11) By Aristotle's time, Empedocles' view that there are four basic elements - earth, air, fire and water - had been generally accepted. Aristotle, however, in addition to this, postulated a fifth element called aether, which he believed to be the main constituent of the celestial bodies.
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1/9/2020 0 Comments Output DevicesOutput devices are things we use to get information OUT of a computer. Here are some examples of output devices:- Monitor George Doyle/Stockbyte/Getty ImagesThe most common computer output device is the monitor or computer screen. Monitors create a visual display from processed data that users can view. They come in a variety of screen sizes and visual resolutions. There are two types of computer monitors, CRT and flat panel. CRT monitors use phosphorescent dots to create the pixels that make up display images. Flat panel monitors usually use LCD or plasma to create output. Light is passed through liquid crystals to create the pixels. All monitors rely on a video card that is located on the computer motherboard or in a special expansion slot. The video card processes the computer data into image details that the monitors can display.PrinterRyan McVay/Photodisc/Getty ImagesPrinters produce a hard copy version of processed data such as documents and photographs. The computer sends the image data to the printer, which then physically recreates the image onto an object. There are three types of computer printers: ink jet, laser and dot matrix. Inkjet printers spray tiny dots of ink on a surface to create an image. Laser printers use toner drums that roll through magnetized pigment and then transfer the pigment to a surface. Dot matrix printers use a print head to imbed images on a surface, using an ink ribbon. There are also colour printers which help to improve the appearance of a document or project.Speakers/HeadphonesZedcor Wholly Owned/PhotoObjects.net/Getty ImagesComputers produce audio data that require output devices such as speakers and headphones to deliver the sound to the user. Audio data is created by the computer and then sent to the audio card, which is located in an expansion slot. The card translates the data into audio signals, which are sent to the audio output device.CD/DVD/Floppy DiscJupiterimages/Comstock/Getty ImagesCD, DVD and floppy disc are output devices that can also be used as storage and input devices. The computer sends data to the disc, where it is embedded and can be later retrieved. Compact disc, or CD, is an optical device that stores audio and visual data in a digital format. Data is placed on the disc, using a laser writer that embeds the data into the disc’s coating. Digital Versatile Disc, or DVD, is an optical device that stores visual data in a media format. DVDs feature a dual coating system that allows audio and visual data to be written at the same time by using a laser. Floppy disc is a magnetic storage device. A layer of magnetized material is placed within a proactive plastic casing. The computer embeds the data into the magnetized material, using a writing head.ProjectorIT Stock/Polka Dot/Getty ImagesProjectors are display devices that project a computer created image. The computer sends the image data to the video card which then sends the video image to the projector. They are typically used for presentations or for viewing videos.PlotterStockbyte/Stockbyte/Getty ImagesPlotters create a hard copy rendition of a digitally rendered design. The design is sent to the plotter via a graphics card, and creates the design using a pen. Generally used with engineering applications, plotters basically draw an image using a series of straight lines.
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