Chapter 22: Origin of Modern Astronomy 22.1 Early Astronomy 22.2 The Earth-Moon-Sun System 22. 3 Earth’s Moon

22.1 Early Astronomy Astronomy deals with the properties of objects in space and the laws under which the universe operates. Early astronomy, known as The “Golden Age”, originated in Greece. (600 B.C.- A.D. 150) Greeks developed basics or geometry and trigonometry, for which they used to measure the sizes and distances of the sun and the moon. Greeks used the above device, known as an Astrolabe, to find the position of the sun and the stars. Observations along with this instrument helped to create modern Astronomy.

Origins of Astronomy 384-322 B.C.: Aristotle concluded that Earth is round because of the shadows it cast on the moon 276-194 B.C.: Eratosthenes was the first person credited for establishing the size of the Earth. Second Century B.C.: Hipparchus is best known for his star catalog. He determined the locations of about 850 stars; divided into six groups based on their brightness.

Geocentric Model of Universe: Milky Way The Greeks believed in a geocentric universe, in which Earth was a sphere that stayed motionless at the center. According to this model, the moon, sun, and other planets, rotated around Earth. Orbit: the path of an object as it goes around another object in space. Geocentric model is now used to describe the motion of objects in the sky as seen from Earth.

Heliocentric Model of Universe: Milky Way Sun-centered universe, proposed by Aristarchus (312- 230 B.C.), known as a Heliocentric model. According to this model, Earth and the other planets orbit the sun. Aristarchus used geometry to calculate the relative distances from Earth to the sun and from Earth to the moon. Current model of universe.

Ptolemaic System A.D. 141: Claudius Ptolemy presented a model of the universe- his theory was able to predict the motion of the planets. Each planet moves slightly eastward among the stars, but periodically the planet appeared to stop, reverse direction, and then resume an eastward motion. This was known as retrograde motion. Ptolemy explained retrograde by saying that planets moved along smaller circles (known as epicycles), which in turn moved along their own orbits around Earth. Ptolemy’s theory was wrong- but his theory was able to account for the planets’ apparent motions.

Ptolemaic System

The Birth of Modern Astronomy 1473- 1543 : Nicolaus Copernicus from Poland First great astronomer to emerge after the Middle Ages Copernicus concluded that Earth is a planet. He proposed a model of the solar system with the sun at the center. Used circles, which were considered to be the perfect geometric shape, to represent the orbits of the planets.

The Birth of Modern Astronomy 1546- 1601: Tycho Brahe – Danish Brahe became interested in astronomy while viewing a solar eclipse Persuaded King Frederick II to build an observatory Brahe designed and built instruments for 20 years, used to measure the location of the heavenly bodies. Brahe’s observations, especially of Mars, were far more precise than any made previously.

The Birth of Modern Astronomy 1571- 1630: Johannes Kepler Discovered three laws of planetary motion Concluded that the orbit of Mars around the sun is not a perfect circle, instead it’s an oval-shaped path called an ellipse. Two points inside the ellipse, called the focus, help determine the shape of the ellipse. The further apart the foci, the more stretched out the ellipse.

The Birth of Modern Astronomy Kepler’s Three Laws of Planetary Motion: The path of each planet around the sun is an ellipse, with the sun at one focus. Each planet revolved so that an imaginary line connecting it to the sun weeps over equal areas in equal time intervals…. Planets travel more rapidly when nearer to the sun and more slowly when farther from the sun. The orbital period of revolution is measured in Earth years, known as Astronomical Units (AU). The average distance between Earth and the sun is 150million kilometers.

The Birth of Modern Astronomy 1564- 1642: Galileo Galilei: Italian scientists Most important contributions were his descriptions of the behavior of moving objects. Constructed his own telescope used to observe the sky Thereafter Galileo made five important discoveries : The discovery of four satellites, or moons, orbiting Jupiter The discovery that the planets are circular disks, not just points of light, as was previously thought. The discovery that Venus has phases just like the moon. The discovery that the moon’s surface was not smooth. The discovery that the sun had sunspots, or dark regions.

The Birth of Modern Astronomy 1642 – 1727: Sir Isaac Newton Newton described a force that holds the moon in orbit around Earth. Others had theorized the existence of such a force, however Newton was the first to formulate and test the law of universal gravitation. Law of Universal Gravitation states: Every body in the universe attracts every other body The greater the mass of the object, the greater its gravitational force Weight is not the same as mass

The Birth of Modern Astronomy Without the influence of gravity, planets would move in a straight line out into space.

22.2 The Earth-Moon-Sun System Two main motions of Earth are rotation and revolution. Rotation is the turning or spinning of a body on its axis. Revolution is the motion of a body along its orbit around some point in space. Earth revolves around the sun, and the moon revolves around Earth. Precession – a slow motion of Earth’s axis that traces out a cone over a period of 26, 000 years. Stonehenge in England  provided a method of determining eclipses- likely used as the first calendar of the year

Motions of Earth Rotation: The main result of Earth’s rotation is day and night. Each rotation of Earth around it’s axis equals about 24 hours. Two ways to measure Earth’s day: Solar day- time interval from one noon to the next. Noon is when the sun has reached its highest point in the sky for that day. Sidereal day- time it takes for Earth to make one complete rotation with respect to a star other than the sun. Has a period of 23 hours, 56 minutes, and 4 seconds

Motions of Earth Revolution: The main results of Earth’s revolution are seasons. At perihelion Earth is closest to the sun- Occurs about January 3 each year. At aphelion Earth is farthest from the sun- Occurs about July 4 each year.

Spring Equinox (March 20/21) -Equal parts sunlight and darkness Autumn Equinox (September 22/23) - Equal parts sunlight and darkness Summer Solstice (June 21/22) - Longest day of the year- most sunlight Winter Solstice (December 21/22) - Shortest day of the year- least sunlight

Motions of the Earth-Moon-Sun System Earth has one natural satellite, the moon. Moon makes one revolution around Earth in ~ one month Perigee when the moon is closest to Earth Apogee when the moon is farthest from Earth On a monthly basis, we observe the phases of the moon as a change in the amount of the moon that appears lit. Lunar (moon) phases are caused by the changes in how much of the sunlit side of the moon faces Earth. 8 total phases of the moon

No Light Shines On Moon Surface New Moon Phase No Light Shines On Moon Surface Waxing (increases) Crescent Waning (decline) Crescent First Quarter: Half-moon visible Third Quarter: Half-moon visible Full Moon Waxing (increasing) Gibbous Waning (decline) Gibbous

Motions of the Earth-Moon-Sun System One lunar cycle takes 29 ½ days, called the synodic month. 27.3 days to get around earth Addition 2 days gets the moon, back fully to it’s “starting” position Basis for the first Roman calendar Moon’s rotation and revolution take the same amount of time (27.3 day), because of this the same side of the moon faces Earth- only astronauts and flying satellites have seen the “back” or dark side of the moon.

Eclipses Solar Eclipse Lunar Eclipse When the moon moves in line directly between Earth and the sun, it casts a dark shadow on Earth- occurs in a new moon phase When the moon moves in line of Earth’s shadow, the moon is elapsed- occurs in a full moon phase

22.3 Earth’s Moon: Lunar Surface Craters: most obvious features- round depressions in the surface of the moon. Most craters were produced by the impact of rapidly mobbing debris or meteoroids.

22.3 Earth’s Moon: Lunar Surface Highlands: densely pitted, light-colored areas Cover most of the surface of the far side of the moon Mountain ranges exist within the highland region Largest mountain is 1 km shorter than Mt. Everest

22.3 Earth’s Moon: Lunar Surface Maria: dark, relatively smooth area (mare). Maria, ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out. - Long channels called rilles are associated with maria. Look like valleys or trenches- remnants of lava flow.

22.3 Earth’s Moon: Lunar Surface Regolith: soil-like layer composed of igneous rock, glass beads, and fine lunar dust.

Chapter 22: Origin of Modern Astronomy 22.1 Early Astronomy 22.2 The Earth-Moon-Sun System 22. 3 Earth’s Moon

22.1 Early Astronomy Astronomy deals with __________________________________ __________________________________ _________________________________. Early astronomy, known as The “Golden Age”, originated in _______. (____ B.C.- A.D. _____) Greeks developed basics or geometry and trigonometry, for which they used to measure the sizes and distances of the sun and the moon. Greeks used the above device, known as an ______________, to find the position of the sun and the stars. Observations along with this instrument helped to create modern Astronomy.

Origins of Astronomy ________________.: Aristotle concluded that Earth is round because of the shadows it cast on the moon _______________Eratosthenes was the first person credited for establishing the size of the Earth. Second Century B.C.: _____________ is best known for his star catalog. He determined the locations of about 850 stars; divided into six groups based on_____________________.

Geocentric Model of Universe: Milky Way The Greeks believed in a _______________________________, in which Earth was a sphere that stayed motionless at the center. According to this model, the moon, sun, and other planets, rotated around ________________. Orbit: __________________________________ ______________________. Geocentric model is now used to describe the motion of objects in the sky as seen from Earth.

Heliocentric Model of Universe: Milky Way Sun-centered universe, proposed by Aristarchus (312- 230 B.C.), known as a ___________________________. According to this model, Earth and the other planets orbit _______________________. Aristarchus used geometry to calculate the relative distances from Earth to the sun and from Earth to the moon. ____________________________.

Ptolemaic System A.D. 141: ___________________ presented a model of the universe- his theory was able to predict the motion of the planets. Each planet moves slightly eastward among the stars, but periodically the planet appeared to stop, reverse direction, and then resume an eastward motion. This was known as __________________________. Ptolemy explained retrograde by saying that planets moved along smaller circles (known as epicycles), which in turn moved along their own orbits around Earth. Ptolemy’s theory was wrong- but his theory was able to account for the planets’ apparent motions.

Ptolemaic System

The Birth of Modern Astronomy 1473- 1543 : Nicolaus Copernicus from _____________. First great astronomer to emerge after the ___________________. Copernicus concluded that Earth is a planet. He proposed _______________ ___________________________________. Used circles, which were considered to be the perfect geometric shape, to represent the orbits of the planets.

The Birth of Modern Astronomy 1546- 1601: Tycho Brahe – ______ Brahe became interested in astronomy while viewing _______ ______________. Persuaded King ______________ to build an observatory Brahe designed and built instruments for 20 years, used to measure the location of the heavenly bodies. Brahe’s observations, especially of _________, were far more precise than any made previously.

The Birth of Modern Astronomy 1571- 1630: __________________ Discovered three laws of planetary motion Concluded that the orbit of Mars around the sun is not a perfect circle, instead it’s an oval-shaped path called __________________ Two points inside the ellipse, called the ________, help determine the shape of the ellipse. The further apart the foci, the more stretched out the ellipse.

The Birth of Modern Astronomy Kepler’s Three Laws of Planetary Motion: The path of each planet around the sun is an ellipse, _______________ ___________________________________. Each planet revolved so that an imaginary line connecting it to the sun weeps over equal areas in equal time intervals…. Planets travel more rapidly ___________________________ and more slowly when farther from the sun. The orbital period of revolution is measured in Earth years, known as ____________________________________. The average distance between Earth and the sun is 150million kilometers.

The Birth of Modern Astronomy 1564- 1642: Galileo Galilei: Italian scientists Most important contributions were his descriptions of the behavior of moving objects. Constructed his own telescope used to observe the sky Thereafter Galileo made five important discoveries : The discovery of _____________________________________________. The discovery that the planets are circular disks, not just points of light, as was previously thought. The discovery that ___________________________________________. The discovery that the moon’s surface was not smooth. The discovery that the _______________________________________.

The Birth of Modern Astronomy 1642 – 1727: ________________________ Newton described a force that holds the moon in orbit around Earth. Others had theorized the existence of such a force, however Newton was the first to formulate and test the law of ________________________ Law of Universal Gravitation states: Every body in the universe attracts every other body The greater the mass of the object, the greater its gravitational force Weight is not the same as mass

The Birth of Modern Astronomy Without the influence of gravity, planets would move in a straight line out into space.

22.2 The Earth-Moon-Sun System Two main motions of Earth are rotation and revolution. ______________ is the turning or spinning of a body on its axis. ______________ is the motion of a body along its orbit around some point in space. Earth revolves around the sun, and the moon revolves around Earth. ________________ – a slow motion of Earth’s axis that traces out a cone over a period of 26, 000 years. Stonehenge in England  provided a method of determining eclipses- likely used as the first calendar of the year

Motions of Earth Rotation: The main result of Earth’s rotation is ___________________________. Each rotation of Earth around it’s axis equals about 24 hours. Two ways to measure Earth’s day: ___________________- time interval from one noon to the next. Noon is when the sun has reached its highest point in the sky for that day. ___________________- time it takes for Earth to make one complete rotation with respect to a star other than the sun. Has a period of 23 hours, 56 minutes, and 4 seconds

Motions of Earth Revolution: The main results of Earth’s revolution are seasons. At _____________Earth is closest to the sun- Occurs about ________ each year. At _____________Earth is farthest from the sun- Occurs about _____each year.

_____________(March 20/21) -Equal parts sunlight and darkness Autumn Equinox (September _________) - Equal parts sunlight and darkness Summer Solstice (June ______) - Longest day of the year- most sunlight _____________(December 21/22) - Shortest day of the year- least sunlight

Motions of the Earth-Moon-Sun System Earth has one natural satellite, ___________________. Moon makes one revolution around Earth in ~ one month ________ when the moon is closest to Earth ________ when the moon is farthest from Earth On a monthly basis, we observe the _____________________as a change in the amount of the moon that appears lit. Lunar (moon) phases are caused by the changes in how much of the sunlit side of the moon faces Earth. _____________ phases of the moon

Motions of the Earth-Moon-Sun System One lunar cycle takes 29 ½ days, called the __________________. 27.3 days to get around earth Addition 2 days gets the moon, back fully to it’s “starting” position Basis for the first __________________ Moon’s rotation and revolution take the same amount of time (27.3 day), because of this the same side of the moon faces Earth- only astronauts and flying satellites have seen the “back” or dark side of the moon.

Eclipses ___________________ ___________________ When the moon moves in line directly between Earth and the sun, it casts a dark shadow on Earth- occurs in a new moon phase When the moon moves in line of Earth’s shadow, the moon is elapsed- occurs in a full moon phase

22.3 Earth’s Moon: Lunar Surface Craters: most obvious features- round depressions in the surface of the moon. Most craters were produced _________________________ __________________________________________________.

22.3 Earth’s Moon: Lunar Surface Highlands: __________________________________________ Cover most of the surface of the far side of the moon Mountain ranges exist within the highland region Largest mountain is 1 km shorter ______________________

22.3 Earth’s Moon: Lunar Surface Maria: __________________________________________________ Maria, ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out. - Long channels called _________ are associated with maria. Look like valleys or trenches- remnants of lava flow.

22.3 Earth’s Moon: Lunar Surface Regolith: soil-like layer composed of ___________________________ _____________________________________________________________.