Module 1 (The Universe)

19問 • 1年前

問題一覧

In modern astronomy, ____________is defined as the apparent daily motion of stars and other celestial bodies across the sky due to Earth’s rotation. Man has observed the sun rising from the east and set in the west. Man has observed the sun rising from the east and set in the west.

Diurnal Motion

is the apparent yearly motion of stars and other celestial bodies across the sky due to Earth’s revolution. Below are events under annual motion.

Annual motion

If we trace the path the sun takes in the celestial sphere as we see on Earth, we would have traced the ecliptic. A band of thirteen constellations collectively called zodiac can be seen in the ecliptic. Ancient civilizations have observed that these constellations changes through months as constellations are visible at different times in a year. These constellations served to mark the time for planting and used by astronomers to develop a chart called horoscope.

Zodiac and the ecliptic

are the two days in a year in which the sun crosses the celestial equator occurring near March 20 (vernal equinox) and near September 22 (autumnal equinox). Midway between these two equinoxes is the solstices. Solstices are the two days in a year in which the Sun is at the farthest declination (north or south) from the celestial equator. Ancient Greeks and Early Chinese civilizations have recorded solstices by observing the declination of the sun for several days before and after the solstice. The calculated half-way between the days with the equal declination of the sun at noon would be the solstice. This method also applies for equinoxes.

Equinoxes and Solstices Equinoxes

Hipparchus in 150 BCE has discovered based on his observation that the north celestial pole has changed during the period of a half - century. He noticed that the slow and continuous change in the direction in which the sky is moving. We understand at present that precession is the slow ‘wobbling’ of Earth’s axis of rotation due to the gravitational pull of the Moon and Sun.

Precession

___________usually rise from east to west as we see in the celestial sphere. However, it was observed by the ancient astronomers that the planets seem to move westward for several weeks and move eastward again in the succeeding weeks. In our current situation, we can explain that these retrograde motions were due to the difference in the period of revolution of the planets around the sun. With Earth being closer to the sun, it moves faster than the planets farther from the Sun. Ptolemy in his time held the belief that the Earth does not revolve and is the center of the universe.

Planets

___________a Danish astronomer continuously and precisely recorded the position of the sun, moon, and planets for over 20 years using instruments that are like giant protractors. He noted based on his observations that the positions of the planets differ from those that were published. However, he was not able to develop a better model than Ptolemy’s as he didn’t have the ability to analyze his data.

Tycho Brahe

Years before his death, he hired ___________ as a research assistant to aid in analyzing his data. Brahe was reluctant to provide such data to Kepler, but at his death, the observational data was possessed by Kepler. Being knowledgeable in geometry, Kepler was able to derive from Brahe’s data that the orbital path of Mars was elliptical contrary to the previous investigators who were trying to fit the planetary paths in circles.

Johannes Kepler

_______________have described ‘fixed stars’ moving in the sky at the same arrangement and speed as most of the stars are. Stars whose movements deviate from what seems to be fixed stars were called ‘planetes’ which means ‘wandering stars’ in Greek.

The greek astronomers

The distance between ______________ was found to be 5000 stadia (approx. 800 km). Thus, Eratosthenes thought the Earth’s circumference must be 50 x 5000 stadia or 250,000 stadia (40,000 kilometers).

Syene and Alexandria

__________________ a Greek Mathematician told that no vertical shadow was cast as the sun rays fall vertically in the city of Syene in Egypt during summer solstice.______________ noted that at the same time a shadow was cast as the sun rays fell at an angle of 7.2° [one fiftieth (1/50) of a circle in ancient Greek writings] in the city of Alexandria. He assumed that the sun was so distant that the rays fall parallel to each other on the Earth’s surface and that the difference in the shadows cast in the two cities was due to the curvature of Earth’s round surface.

Eratosthenes

Even before__________, the Greeks have deduced that the Earth is spherical based on the observation that the shadow cast by the Earth during a lunar eclipse is circular and that the only shape that can cast a circular shadow at whatever direction it is pointed is a sphere.

Plato

____________were also able to measure the diameter of the Earth.

The greek

___________ also noted that the stars are viewed differently as they travel north and south.

The greek

The sense of symmetry by Greeks demands a spherical Earth located at the center of the ___________.

sphere of heavens

The __________ also kept track of the yearly cycle of the star Sirius which corresponds to the flooding of Nile.

Egyptians

Early __________ civilizations kept track of the comets, meteors, and dark spots of the Sun.

Chinese

____________ also developed a calendar based on the movements of Venus.

Mayan civilization

the ____________ utilized the stars for navigation. Below are astronomical events before telescope was invented.

Polynesians

Physical Science

Al-Walli Bayotlang · 44問 · 1年前

Physical Science