PHYSCI WEEK 1-5

• The Greeks were much noted for their contributions in different fields. They were not only great philosophers but great scientists and mathematicians as well.
• Ptolemic System


  A model that claims the planets moved in a complicated system of circles. This geocentric model had the Earth at the center of the universe.
• Oblate spheroid


  The shape of the Earth, with a bulging equator and squeezed poles.
• The North Star was believed to be in a fixed position in the sky. However, when the Greeks traveled to places nearer the equator, like Egypt, they noticed that it is closer to the horizon.
• Aristotle


  A student of Plato and considered as one of the great philosophers of his time; his earth-centered view dominated for almost 2,000 years.
• Eclipse


  An astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured by passing into the shadow of another body or by having another body pass between it and the viewer.
• Shadow


  A dark (real image) area where light from a light source is blocked by an opaque object.
• Eratosthenes


  A Greek philosopher who computed the circumference of the Earth and who gave the most accurate size during their time.
• Retrograde Motion


  An apparent change in the movement of the planet through the sky. It is not real in that the planet does not physically start moving backwards in its orbit. It just appears to do so because of the relative positions of the planet and Earth and how they are moving around the Sun.
• Winter Solstice


  A moment when the Sun's path in the sky is farthest south in the Northern Hemisphere or farthest north in the Southern Hemisphere.
• Summer Solstice


  The longest day of the year. In the Northern Hemisphere it is in June, while in the Southern Hemisphere it's in December.
• Heliocentrism


  The astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System.
• Geocentrism


  Any theory of the structure of the solar system (or the universe) in which Earth is assumed to be at the center of it all.
• Nicolaus Copernicus


  He considered the sun as the stationery center of the universe. He classified Earth as a planet just like Mercury, Venus, Mars, Jupiter, and Saturn.
• Gelileo Galilei


  He was the greatest Italian scientist of the Renaissance. Due to the telescope, he was able to discover and observe important astronomical facts such as lunar craters, the phases of the Venus, the moons of Jupiter, sun spots, and the sizes of the stars.
• Astrology


  A type of divination that involves the forecasting of earthly and human events through the observation and interpretation of the fixed stars, the Sun, the Moon, and the planets. Devotees believe that an understanding of the influence of the planets and stars on earthly affairs allows them to both predict and affect the destinies of individuals, groups, and nations.
• Astronomy


  The study of everything in the universe beyond Earth's atmosphere. That includes objects we can see with our naked eyes, like the Sun, the Moon, the planets, and the stars. It also includes objects we can only see with telescopes or other instruments, like faraway galaxies and tiny particles.
• Astrology has some of the trappings of genuine science, such as the use of certain mathematics and complex charts and a specific terminology, from around the 17th Century began to be cast aside as a science.
• Around 500 B.C., most Greeks believed that the Earth was round, not flat. It was Pythagoras and his pupils who were first to propose a spherical Earth.
• In 500 to 430 B.C., Anaxagoras further supported Pythagoras' proposal through his observations of the shadows that the Earth cast on the Moon during a lunar eclipse. He observed that during a lunar eclipse, the Earth's shadow was reflected on the Moon's surface. The shadow reflected was circular.
• Around 340 B.C., Aristotle listed several arguments for a spherical Earth which included the positions of the North Star, the shape of the Moon and the Sun, and the disappearance of the ships when they sail over the horizon.
• Aristotle argued that if the Moon and the Sun were both spherical, then perhaps, the Earth was also spherical.
• Anaxagoras


  Was able to explain what causes the phases of the moon. According to him, the moon shone only by reflected sunlight. Since it is a sphere, only half of it illuminated at a time. This illuminated part that is visible from the earth changes periodically.
• Eudoxus


  Proposed a system of fixed spheres. He believed that the Sun, the moon, the five known planets and the stars were attached to these spheres which carried the heavenly bodies while they revolved around the stationary Earth.
• Aristotle


  Was a student of Plato. For him, the earth is spherical in shape since it always casts a curved shadow when it eclipses the moon. He also believed that the earth was the center of the universe. The planets and stars were concentric, crystalline spheres centered on the earth.
• Aristarchus


  Is the very first Greek to profess the heliocentric view. The word helios means sun; centric means centered. This heliocentric view considered the sun as the center of the universe. He learned that the sun was many time farther than the moon and that it was much larger than the earth. He also made an attempt to calculate the distance of the sun and the moon by using geometric principles. He based his calculations on his estimated diameters of the earth and moon, and expressed distance in terms of diameter. However, the measurements he got were very small and there were a lot of observational errors.
• Eratosthenes


  The first successful attempt to determine the size of the earth was made by him. He did this by applying geometric principles. He observed the angles of the noonday sun in two Egyptian cities that were almost opposite each other- Syene (now Aswan) in the south and Alexandria in the north. He assumed they were in the same longitude.
• Hipparchus


  Is considered as the greatest of the early Greek astronomers. He observed and compared the brightness of 850 stars and arranged them into order of brightness or magnitude. He developed a method for predicting the times of lunar eclipses to within a few hours. Aside from this, he also measured the length of the year to within minutes of the modern value.
• Claudius Ptolemy


  He believed that the earth was the center of the universe. His Ptolemic Model claimed that the planets moved in a complicated system of circles. This geocentric model also became known as the Ptolemic System.
• Constellations


  • Grouping of stars
  • Significance varied from culture to culture
  • Stimulated story-telling and creation of great myths
• Constellations


  • Honored great heroes like Hercules and Orion
  • Served as navigational aids for travelers and sailors
  • Provided a guide for planting and harvesting crops
• Constellations were seen to move periodically in the sky, in concert with the seasons
• Charts of these periodic movements became some of the first calendars
• Stars


  Points of light on great revolving celestial sphere having the earth as its center
• Positions of the sphere were believed to affect earthly events and so were carefully measured
• Keen observations and logical reasoning gave birth to both Astrology and later, to Science
• Moon


  A natural object that orbits a larger object
• Eclipse


  When one celestial body such as a moon or planet moves into the shadow of another celestial body
• Solar eclipse


  A type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks the light from the Sun
• Lunar Phase


  One of the cyclically recurring apparent forms of the moon