Transcript Ch 26-Studying Space

Ch 26-Studying Space
• Objectives
– Describe the characteristics of the universe in terms of time,
distance, organization
– Visible and nonvisible parts of electromagentic spectrum
– Refracting and reflecting teloscopes
– Explain how telescopes for nonvisible electromagnetic radiation
differ from light telescopes
– Evidence for Earth’s rotation
– Explain how the change in apparent positions of constellations
provides evidence of Earth’s rotation and revolution around the
sun
– Summarize how Earth’s rotation and revolution provide a basis
for measuring time
– Explain how the tilt of Earth’s axis and Earth’s movement cause
seasons
Characteristics of Universe
• How have people studied the sky in the past?
What is astronomy?
– Scientific study of the universe
– Astronomers
– Why is astronomy important?
• Cosmology-study of origin, properties,
processes, and evolution of universe
• Big bang-big explosion 14 billion yrs ago
• Universe-large and objects far apart
• What tools are used to see distant objects?
Organization of Universe
• What makes up the solar system?
– Sun, Earth, other planets, asteroids and
comets
• Galaxy-collection of stars, dust, and gas
bound together by gravity
• What galaxy do reside in?
– Milky Way
– Beyond are billions of other galaxies
Measuring Distances in Universe
• Approximately 150 million km between
Earth and sun-this is known as
astronomical unit
• Use speed of light to measure distance
• Travels at 300,000 km/s
• Light yr-light travels 9.46 x 10^12 km
• Closet star other than the sun to
Earth=4.22 light yrs away
Observing Space
• Electromagnetic spectrum-all frequencies or
wavelengths of electromagnetic radiation
– Light, radio waves, x rays
• Visible electromagnetic radiation-different colors
result because each color of light has
characteristic wavelength
• Shortest wavelengths-blue and violet, longestred and orange
• Wavelengths not visible-infrared waves,
microwaves, radio waves, ultraviolet rays, x
rays, gamma rays
Models of Solar System
• Aristole-model in which Earth was center,
everything revolved around Earth
• Ptolemy-planets moved in small circlesepicycles, revolved around in larger circles
around Earth
• Copernicus-sun centered, planets
revolved around sun in same direction but
at different speeds and distances from sun
Kepler’s Laws
• Law of ellipses-Each planet orbits the sun in a
path called a ellipse, not a circle
– Elliptical orbits can vary in shape
– Eccentricity-degree of elongation of an elliptical orbit
• Law of equal areas-objects travel at different
speeds in their orbits, equal areas are covered in
equal amounts of time as an object orbits the sun
– Mars travels fastest when closet to sun
• Law of periods-describes the relationship between
average distance between planet and sun and
orbital period of planet
– What is orbital period?
Newton
• Hypothesized moving objects will keep moving
and resist change in speed until acted upon by
outside force
• Inertia-tendency of an object to resist being
moved or resist change in speed or direction
until outside force acts on object
• Newton’s Model of Orbits-gravity causes the
orbit to curve
– Gravity pulls object toward sun, inertia keeps object
moving forward in straight line
– Weaker gravitational pull further away from sun
– Longer orbits=outer planets
Telescopes
• Who constructed the 1st telescope?
– Galileo, 1609, viewed craters on moon and Milky Way
• Instrument that collects electromagnetic radiation from
the sky and concentrates it for better observation
• Optical telescopes-only collect visible light
• Refracting telescopes-uses a set of lenses to gather and
focus light from distant objects
– Focuses different colors of light at different distances
• Reflecting-uses curved mirror to gather and focus light
from distant objects
– Issac Newton
– Gather more light than refracting
Telescopes for Invisible
Electromagnetic Radiation
• Telescopes that detect invisible radiation
• Earth’s atmosphere acts as shield against
many forms of electromagnetic radiation
– Prevents short wavelengths from reaching
Earth’s surface
• Only way to study many forms of radiation
is from space
Space Based Astronomy
• Space telescopes-launched into space to collect
electromagnetic radiation from objects in space
– Examples-Hubble Space Telescope, Chandra X-ray Observatory,
Compton Gamma Ray Observatory, Spitzer Space, James Webb
Space Telescope
• Voyager 1 and 2 investigated Jupiter, Saturn, Uranus,
Neptune in 1977
• Galileo investigated Jupiter and moons from 1995-2000
• Robotic-are spacecraft that carry only instruments and
computers
• Humans never went past moon
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1969-1972, 12 people landed on moon by NASA
Mars
Welcome to Discovery Education Player
Challenger and Columbia
Sec 2-Movements of Earth
• Rotation-spin of a body on its axis, complete
rotation= 1 day
• How do scientists know Earth rotates?
• Foucault pendulum-evidence of Earth’s rotation
by using pendulum
– Jean Bernard Leon Foucault
• Coriolis Effect-movement of ocean surface
currents and wind belts by rotation of Earth
• Revolution-motion of a body that travels around
another body in space
• Orbit-the path that a body follows as it
travels around another body in space
• Ellipse-closed curve, shape is determined
by 2 pts w/in ellipse
– Earth orbits the sun in a ellipse
• Perihelion-pt in orbit of a planet at which
planet is closest to sun
• Aphelion-pt in orbit of a planet at which the
planet is farthest from sun
Constellations and Earth’s Moon
• What is a constellation?
– Group of stars organized in recognizable pattern
– 88 constellations
– Greek names-2000 yrs ago
• Earth moves, constellations do not. Rotation of
Earth on its axis causes change in position
• Earth’s revolution, causes positions to change
over several weeks
– Different constellations will appear in night sky as
seasons change
Measuring Time
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Day and yr are based on periods of Earth’s motion
Rotation=1 day
Revolution=365 ¼ days
Formation of calendar-created for measuring long
intervals of time by dividing time into periods of days,
weeks, months, and yrs
– Who created calendar?
• Egyptians, Bablonians, Aztecs
– Extra ¼ day added to February, leap yr
• Modern calendar-keep calendar aligned w/ seasonsPope Gregory XIII
• Time zones- Earth divided into 24 time
zones
– Earth’s time zones cover about 15 deg each
• International date line-runs N to S through
P ocean. Friday west, Thursday east
– No islands or continents
• Day light saving time-clocks set 1 hr
ahead of standard time in April, set back to
standard time in october
– No daylight savings time in equatorial region12 hrs of day
Seasons
• Axis tilted at 23.5 deg
• Sun rays change as Earth moves toward orbit
• Seasonal Weather-changes in angle at which the sun’s rays strike
Earth’s surface cause the seasons
– N Pole tilted away from sun in winter
• Equinoxes-moment when sun appears to cross the celestial
equator-line drawn on sky directly overhead from equator on Earth
– Autumnal equinox-Sept 22 or 23
– Vernal equinox-Mar 21 or 22
• Summer solstices-pt at which sun is as far N or as far S of equator
as possible. June 21 or 22
– 24 hrs of daylight during summer solstice at Arctic Circle, opposite at
Antarctica
• Winter solstices-N Pole is titled to farthest pt away from sun. Dec 21
or 22