AstronomyAstronomy

General Science Spring ‘07

History of the UniverseHistory of the Universe

Earth = 1 of 9 planetsSun= 1 of 100 billion stars in the Milky

Way, 1 of infinite numbers in our universe

Ancient AstronomyAncient Astronomy

Golden Age= 600 BC-150 AD in GreeceBeliefs relied on philosophy (ideas) and

observations.

Geocentric ViewGeocentric View

At first, we thought the Earth was the center of the universe

Geo=Earth -centric=center

Heliocentric viewHeliocentric view

Eventually, we realized the SUN was the center of our galaxy.

This was called the HELIOcentric view.

Modern AstronomyModern Astronomy

Ideas based more on observation

Nicholas Copernicus (1473-1543, Poland)– Earth rotates– Said Earth is a planet

(only 5 known at this point: Mercury, Venus, Mars, Jupiter, Saturn)

Johannes Kepler (1571-1630)Johannes Kepler (1571-1630)

Laws of Planetary Motion– The path of each planet

is an ellipse– Each planet travels at

its own speed– Astronomical Unit

(AU) = 150 million kilometers

Galileo Galilei (1564-1642)Galileo Galilei (1564-1642)

Around at the same time as Kepler

Favored the heliocentric viewpoint

Created the telescope (which later made him go blind

after looking at the sun through it) Discovered the four

moons of Jupiter

Sir Isaac Newton (1643-1727, Sir Isaac Newton (1643-1727, England)England)

Law of Gravity! Proved Kepler’s idea

that planets orbit in an ellipse.

Trip through our UniverseTrip through our Universe

Light year= how far light

travels in one year Speed of light= 186,000

miles per second!

Billions and billions of stars

Carl Sagan 11/9/34-10/20/96

ConstellationsConstellations

Star groups that form patterns as seen from Earth

Big dipper (ursa major)Little dipper (ursa minor)Orion

NovasNovas

When a star suddenly increases in brightness (100x) in a few hrs/days, then dims back to original state.

Gases from one binary star strike the other causing nuclear explosions which we see as light.

NovasNovas

NebulaeNebulae

We see light from stars, but most give off other types of radiation– X-Rays, Infared (heat), UV light, radio waves

All types can be seen by different types of telescopes.

NebulaeNebulae

A huge massive cloud glowing between stars.

Where new stars form

GalaxiesGalaxies

Contain stars and are major features of our universe.

There are billions of galaxies each with billions of stars of their own.

Three Types of GalaxiesThree Types of Galaxies

Spiral– Shaped like pinwheels– Andromeda– Milky Way

Three Types of GalaxiesThree Types of Galaxies

Elliptical– Vary in shape from

spherical to flat discs– Contain little dust/gas

Three types of GalaxiesThree types of Galaxies

Irregular– No ordinary shape– Least common

The Milky WayThe Milky Way

100,000 light years across!

15,000 light years thick!

It would take, traveling at the speed of light, 100,000 years to cross!

Earth and its MoonEarth and its Moon

Magnetic field- invisible lines of force that connect poles

Earth has a magnetic core

Made from iron and nickel

Earth= MagnetEarth= Magnet

Van Allen Belts– Doughnut shaped

fields that trap particles from solar wind (e- and p+), produce auroras

– Can see the aurora borealis in Canada and Alaska

Neil Armstrong + Buzz AldrinNeil Armstrong + Buzz Aldrin

First men to land on the moon

July 20,1969 Neil Armstrong first to

step on the moon

First Step on MoonFirst Step on Moon

The Moon’s MeasurementsThe Moon’s Measurements

3476 km in diameter Gravity 1/6 that of Earth 384,403 km from Earth 4.6 billion years old No H2O, no atmosphere 100oC @ noon, -175oC at

night

The Moon’s FeaturesThe Moon’s Features

Galileo was the first to observe the moon

Saw mountains and low areas.

Saw craters formed by asteroids

The Moon’s movementThe Moon’s movement

Moon revolves around EarthPerigee- closest to Earth (350,000 km)Apogee- furthest (400,00 km)27.5 days to rotate on axis27.5 days to revolve around the Earth

– Why we only see one side of the moon.

The Moon’s OriginThe Moon’s Origin

Several TheoriesAsteroid “captured” by Earth’s gravityFormed from the same nebulae as the

planetsAsteroid (size of Mars) struck Earth, ejected

chunk of Earth outward (widely accepted theory)

Nothing 100% certain

Earth, Moon and Sun Earth, Moon and Sun

The reflection of the sun on the moon results in changing appearance of moon as seen from Earth.

The Moon appears to change shapeThe Moon doesn’t shine, it reflects light.

Phases of the MoonPhases of the Moon