HISTORY OF TIBETAN LITERATURE . SIKE! HISTORY OF ASTRONOMY

HISTORY OF HISTORY OF TIBETAN TIBETAN

LITERATURELITERATURE

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HISTORY OF HISTORY OF ASTRONOMYASTRONOMY

Ancient Greeks

Early Astronomy

Astronomy is the science that studies the universe. It includes the observation and interpretation of celestial bodies and phenomena.

The Greeks used philosophical arguments to explain natural phenomena.

The Greeks also used some observational data.

Ancient Greeks

Early Astronomy

Geocentric Model• In the ancient Greeks’ geocentric model, the

moon, sun, and the known planets—Mercury, Venus, Mars, and Jupiter—orbit Earth.

Heliocentric Model• In the heliocentric model, Earth and the other

planets orbit the sun.

Geocentric and Heliocentric Models

Stonehenge• A group of stones arranged in

a circle.• Lined up with the summer and

winter sunrises. • Used for ceremonies and

rituals

Babylonians

• Tracked the positions of the planets and moons

• Created first calendar

• Ptolemy: Geocentric model, including epicycles

1. Imperfect, changeable Earth,

2. Perfect Heavens (described by spheres)

Central guiding principles:

Epicycles

The ptolemaic system was considered the “standard model” of the Universe

until the Copernican Revolution.

Introduced to explain retrograde (westward) motion of

planets

Epicycles

The Birth of Modern Astronomy

Early Astronomy- Copernicus

Nicolaus Copernicus• Copernicus concluded

that Earth is a planet. Earth and all the other planets orbited the sun in perfect circles.

He proposed a model of the solar system with the sun at the center.


Early Astronomy- Brahe

Tycho Brahe• Tycho Brahe designed and built instruments to

measure the locations of the heavenly bodies. Brahe’s observations, especially of Mars, were far more precise than any made previously.


Early Astronomy- Kepler

Johannes Kepler• Kepler discovered three laws of planetary motion:

1. Orbits of the planets are elliptical.

2. Planets revolve around the sun at varying speed.

3. There is a proportional relationship between a planet’s orbital period and its distance to the sun.


Early Astronomy

Johannes Kepler• An ellipse is an oval-shaped path.• An astronomical unit (AU) is the average

distance between Earth and the sun; it is about 150 million kilometers.

Planet Revolution


Early Astronomy

Galileo Galilei• Galileo’s most important contributions were his

descriptions of the behavior of moving objects.• He developed his own telescope and made

important discoveries: 1. Four satellites, or moons, orbit Jupiter.

2. Planets are circular disks, not just points of light.

3. Venus has phases just like the moon.

4. The moon’s surface is not smooth.

5. The sun has sunspots, or dark regions.

The Solar System Model Evolves


Early Astronomy

Sir Isaac Newton• Although others had theorized the existence of

gravitational force, Newton was the first to formulate and test the law of universal gravitation.

Universal Gravitation• Gravitational force decreases with distance.• The greater the mass of an object, the greater is

its gravitational force.

Gravity’s Influence on Orbits


Early Astronomy- Herschel

Herschel Developed the first powerful telescope Saw fuzzy spots beyond our galaxy Didn’t know what they were

Modern Astronomy- WWII

World War II

1st solid -fuel rockets where developed for airplanes to provide a boost

Modern Astronomy-Russia

Visualization

Russian Konstantin Tsiolkovsky imagined how to use rocket to voyage into space

Modern Astronomy-Edwin Hubble

Edwin Hubble

Used improved telescope devices and found the fuzzy things Herschel did not understand

Fuzzy things were other galaxies Expanded our idea of space

Satellite Launch

1st Satellite Launched

Soviets launched Sputnik 1 in 1957

1st Astronaut

1st Space Traveler

A dog named Laika, survived several days on Sputnik 2 - 1957

Died of heat exhaustion after temperatures rose

Explorer 1

1st US Satellite

Noticed radiation bands across the earth 1958

Explorer 6- United States

1st Photo of Earth

1959 Most famous picture of all time

US Tiros 1

1st Weather Satellite

1960

Corona

1st Spy Satellite

US sent Corona to spy on the Soviet missile base- 1960

Soviet- Uri Gagarin

1st Human Astronaut

1961

Apollo 11- 1969

MAN ON THE MOON

Crew of Neil A. Armstrong, Buzz Aldrin, and Michael Collins

Armstrong and Aldrin collected rocks and set up a lab on the moon

Man on the Moon footage

https://youtu.be/G6A72ufn3l4

Pioneer II- 1974

Off to Jupiter

Left to inspect Jupiter but got pulled in by its gravity and was sent off toward Saturn.

It left the Solar System and in 1995, the power supply finally ran out and we lost contact

Sally K. Ride

1st Woman Astronaut

Rode on the Challenger from the US in 1983

Space Disasters• Top Five Worst Space Disasters

• https://youtu.be/dmlM9zBadX8

Cassini: 2000-2004

Cassini

Left to pass Jupiter and to land a probe on Saturn’s moon Titan

Final Space Shuttle?•July 2011- IS IT OVER?

End of an Era

Motions of Earth

The Earth–Moon–Sun System

The two main motions of Earth are rotation and revolution. Precession is a third and very slow motion of Earth’s axis.

Motions of Earth


Rotation• Rotation is the turning, or spinning, of a body on

its axis.

• Two measurements for rotation:1. Mean solar day is the time interval from one

noon to the next, about 24 hours.

2. Sidereal day is the time it takes for Earth to make one complete rotation (360º) with respect to a star other than the sun—23 hours, 56 minutes, 4 seconds.

Sidereal Day

Motions of Earth


Revolution• Revolution is the motion of a body, such as a

planet or moon, along a path around some point in space.

• Perihelion is the time in January when Earth is closest to the sun.

• Aphelion is the time in July when Earth is farthest from the sun.

Motions of Earth


Earth’s Axis and Seasons

• Because of the inclination of Earth’s axis to the plane of the ecliptic, Earth has its yearly cycle of seasons.

• The plane of the ecliptic is an imaginary plane that connects Earth’s orbit with the celestial sphere.

The Ecliptic

Motions of Earth


Precession• Precession traces out a cone over a period of

26,000 years.

Earth–Sun Motion• The solar system speeds in the direction of the

star Vega.

• The sun revolves around the galaxy.

• Earth is presently approaching one of its nearest galactic neighbors, the Great Galaxy in Andromeda.

Precession

Motions of the Earth–Moon System


Perigee is the point at which the moon is closest to Earth.

Apogee is the point at which the moon is farthest from Earth.



Phases of the Moon• The phases of the moon are the progression of

changes in the moon’s appearance during the month.

• Lunar phases are a result of the motion of the moon and the sunlight that is reflected from its surface.

Phases of the Moon



Lunar Motions• The synodic month is based on the cycle of the

moon’s phases. It lasts 29 1/2 days.

• The sidereal month is the true period of the moon’s revolution around Earth. It lasts 27 1/3 days.



• The difference of two days between the synodic and sidereal cycles is due to the Earth–moon system also moving in an orbit around the sun.

Lunar Motions

• The moon’s period of rotation about its axis and its revolution around Earth are the same, 27 1/3 days. It causes the same lunar hemisphere to always face Earth.

Eclipses


Solar eclipses occur when the moon moves in a line directly between Earth and the sun, casting a shadow on Earth.

During a new-moon or full-moon phase, the moon’s orbit must cross the plane of the ecliptic for an eclipse to take place.

Lunar eclipses occur when the moon passes through Earth’s shadow.

Solar Eclipse

Lunar Eclipse

The Lunar Surface

Earth’s Moon

• A crater is the depression at the summit of a volcano or a depression produced by a meteorite impact.

Craters

• Most craters were produced by the impact of rapidly moving debris.

• Rays are any of a system of bright, elongated streaks, sometimes associated with a crater on the moon.

The Moon’s Surface

Mare Tranquillitatus(Sea of Tranquility)

Mare Imbrium(Sea of Rains)

KeplerCrater

CopernicusCrater

Formation of a Crater

The Lunar Surface

Earth’s Moon

• Most of the lunar surface is made up of densely pitted, light-colored areas known as highlands.

Highlands

• Maria, ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out.

Maria

• A rille is a long channel associated with lunar maria. A rille looks similar to a valley or a trench.

The Lunar Surface

Earth’s Moon

• The lunar regolith is a thin, gray layer on the surface of the moon, consisting of loosely compacted, fragmented material believed to have been formed by repeated impacts of meteorites.

Regolith

Major Topographic Features of the Moon

Lunar History

Earth’s Moon

The most widely accepted model for the origin of the moon is that when the solar system was forming, a body the size of Mars impacted Earth. The resulting debris was ejected into space, began orbiting around Earth, and eventually united to form the moon.

Formation of Earth’s Moon

What were the epicycles in Ptolemy’s model supposed to explain?

1. The fact that planets are moving against the background of the stars.

2. The fact that the sun is moving against the background of the stars.

3. The fact that planets are moving eastward for a short amount of time, while they are usually moving westward.

4. The fact that planets are moving westward for a short amount of time, while they are usually moving eastward.

5. The fact that planets seem to remain stationary for substantial amounts of time.

In the Copernican “Universe”, the orbits of planets and moons were …

1. Perfect Circles

2. Ellipses

3. Spirals

4. Epicycles

5. None of the above.

How did William Herschel contribute to the astronomy community?

• Created the most powerful telescope to date

What was the first satellite launched into space?• Sputnik I

How Long is a Sidereal Day?

• 24 Hours

• 23 Hours 56 Minutes

• 24 Hours 50 Minutes

Why is the summer longer than winter?

1. Because of the precession of the Earth’s axis of rotation.

2. Because of the moon’s 5o inclination with respect to the Ecliptic.

3. Because the Earth is rotating around its axis more slowly in the summer (→ longer days!).

4. Because the Earth is closest to the sun in January and most distant from the sun in July.

5. Because the Earth is closest to the sun in July and most distant from the sun in January.

What is the difference between a solar and lunar eclipse?

Do you agree with the Impact Theory as the theory for the creation of the Moon?

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HISTORY OF TIBETAN LITERATURE . SIKE! HISTORY OF ASTRONOMY