 Viewing the Universe Chapter 26 Section 1

Why study astronomy?  By studying the stars, astronomers have been able to learn more about the Earth and our solar system.  May lead to improved energy sources on Earth  Protection against objects that could collide with Earth

Organization of the Universe  What is your galactic address?

Measuring Distance  Within our solar system we use astronomical units (AU) 150 million km  Outside the solar system we use light years 300,000 km/s

Observing Space  Scientists use the electromagnetic spectrum to observe space

Visible Light

Invisible EM Radiation  Infrared – longer than visible light ‘below the red’  Ultra violet – shorter than visible light ‘beyond the violet’

Telescopes  Galileo was the first to successfully build a telescope by using two lenses to make distant objects seem close.  The first telescopes only collected visible light. These are called optical telescopes.  There are two types

Problems with refractors  Can’t focus different colors at the same time  Difficult to make large lenses  Mirrors can be made as large as possible without affecting the clarity of the image

Keck Telescopes

GCT – largest telescope

Telescopes can detect different EM radiation

Problems with Earth-based telescopes  Earth’s atmosphere interferes with EM detection

Hubble Space Telescope

Chandra X-Ray Observatory

Swift Spacecraft

Spitzer Space Telescope

Voyager 1 and 2

Galileo Spacecraft

Cassini

Spirit and Opportunity

New Horizons

Human Space Exploration  Spacecraft only carrying instruments and computers are called robotic  Humans have never gone beyond our moon  12 people have landed on the moon  Humans in space are in orbit aboard the International Space Station conducting research of the effects of space on humans

International Space Station

Space Program Spinoffs  Benefits the space program have to humans include:  Television  Weather prediction  GPS navigation  Small and lighter electronics

Movement of the Earth Section 2  Why it matters:  Earth’s rotation and revolution affect natural events, weather patterns, and helps us measure time

The Sun does not move  Sun rises in the east and sets in the west because Earth rotates from west to east

The Coriolis Effect  Evidence of Earth’s rotation can be seen in ocean currents and wind belts.

Revolving Earth  Earth revolves around the Sun about 30 k/s  The path Earth takes is called an orbit  The shape of Earth’s path is an ellipse

Earth’s orbit

Constellations and Earth’s motion  A group of stars organized in a recognizable pattern  There are 88 constellations

Earth’s rotation makes the constellations seem to move in the sky

Measuring Time  The day and year are based on Earth’s motion  Each rotation is 24 hours. Each revolution around the Sun is 365 ¼ days  The ¼ is made up every four years by adding a day to February (leap year)

Time Zones  We use the Sun to measure time. The Sun is highest in the sky at noon.  Earth’s surface is divided into 24 standard time zones  Earth’s circumference is 360 degrees. Divide that by 24 hours needed for a day and you get that the Sun travels 15 degrees every hour. So each time zone is about 15 degrees apart

Daylight Savings Time  Daylight is shorter in winter than summer due to the tilt of the Earth. In March, time is set one hour forward and in November it is set back to standard time  Countries near the equator do not observe daylight savings times because daylight time does not change much

The seasons  Seasons are caused by Earth’s 23.5 degree tilt pointing toward the North Star.  Northern hemisphere summer is when the north pole points toward the Sun. Southern hemisphere is therefore in winter.  The angle of the Sun’s rays determines temperature. More of the Sun’s direct rays make it warmer

Equinoxes  The moment the Sun appears to cross the equator  The autumnal equinox occurs on Sept. 22 or 23 (first day of fall)  The vernal equinox occurs on March 21 or 22 (first day of spring)  The hours of day and night are equal EVERYWHERE on Earth.

Solstices  The beginning of summer and winter  Summer solstice June 21 or 22 (Sun strikes Earth at 90 degrees on the Tropic of Cancer)  Winter solstice on December 21 or 22 (Sun strikes Earth at 90 degrees on the Tropic of Capricorn)