Download CH. 26 – STUYDING SPACE The Value of Astronomy astronomy the

CH. 26 – STUYDING SPACE
The Value of Astronomy
astronomy the scientific study of the universe
Scientists who study the universe are called astronomers.
In the process of observing the universe, astronomers have made exciting discoveries, such as new planets, stars, black
holes, and nebulas.
They study about the origin of Earth and the processes involved in the formation of our solar system.
The Value of Astronomy, continued
The US Space Program has usually been less than 1% of the US Budget and yet it provides overwhelming benefits in
space exploration, improvement of life technologies, scientific study of our planet, improvements in medicine,
improvement in communication, etc.
Scientific research is supported by federal agencies, such as the National Science Foundation and NASA (National
Aeronautics and Space Administration). Private foundations and industry also fund research. ALL provide jobs!
Astronomy & space exploration benefits to society
Prevent catastrophes (ELE, hurricanes, earthquakes, tsunamis, volcanoes, fires, etc.)
Miniaturization of electronic equipment / computers. (objective is to make things lighter/smaller for space flight)
New energy technologies (solar panels, fuel cells)
Home improvements: Water filtration, air conditioning/heating, smoke detectors, cordless appliances
Satellite technology (communications, entertainment, weather forecasting, global positioning systems, military)
Scientific remote sensing: study things such as global: agriculture, fishing, pollution, climate, forests, ecosystems, etc.
Astronomy & space exploration benefits to society
Medical Benefits: Eye Screening, Ultrasound scanners, MRI, cataract surgery tools, arteriosclerosis detection, automatic
insulin pump, portable x-ray device and clean room apparel, Laser Angioplasty, Digital Imaging Biopsy System, etc…
Computer Technology: Virtual Reality, Microcomputers, Advanced keyboards, Laser Surveying, Compact Disc, Database
Management System, Aircraft controls, and Design Graphics, Ground Processing Scheduling System
Consumer products: Scratch resistant lenses, water purification system, high-density batteries, trash compactors, shockabsorbing helmets, home security systems, composite golf clubs, smoke detectors, flat panel televisions, freeze-dried
technology, quartz crystal timing equipment
Characteristics of the Universe
Organization of the Universe
The nearest part of the universe to Earth is our solar system.
The solar system includes the sun, Earth, the other planets, and many smaller objects such as asteroids and comets.
The solar system is part of a galaxy.
galaxy is a collection of stars, dust, and gas bound together by gravity
The galaxy in which our solar system resides is called the Milky Way.
Characteristics of the Universe
Organization of the Universe
The nearest part of the universe to Earth is our solar system.
The solar system includes the sun, Earth, the other planets, and many smaller objects such as asteroids and comets.
The solar system is part of a galaxy.
galaxy is a collection of stars, dust, and gas bound together by gravity
The galaxy in which our solar system resides is called the Milky Way.
Characteristics of the Universe, continued
Measuring Distances in the Universe
astronomical unit = average distance between Earth and the sun; ~150 million kilometers (symbol, AU)
Astronomers also use the speed of light to measure distance.
Light travels at 300,000 km/s. In one year, light travels 9.46 x 1012 km. This distance is known as a light-year.
Aside from the sun, the closest star to Earth is 4.22 light-years away.
Distances in the Solar System
Distances in space are measured in astronomical units (AUs)
1 AU = the distance from the Earth to the Sun
• Mercury is 0.39 AUs from the sun, about 2/3 closer than Earth
• Pluto is 39.44 AUs from the sun, 39 times farther than Earth
Observing Space
Electromagnetic Spectrum
electromagnetic spectrum all of the frequencies or wavelengths of electromagnetic radiation.
Light, radio waves, and X rays are all examples of electromagnetic radiation.
This radiation is composed of traveling waves of electric and magnetic fields that have fixed wavelengths and therefore
fixed frequencies.
Observing Space, continued
Visible Electromagnetic Radiation
The human eye can see only radiation of wavelengths in the visible light range of the spectrum.
The shortest visible wavelength of light are blue and violet, while the longest visible wavelength of light are orange and
red.
Electromagnetic radiation shorter than wavelengths of violet or longer than wavelengths of red light cannot be seen by
humans.
These invisible wavelengths include infrared waves, microwaves, radio waves (at longer wavelengths than red), as well
as ultraviolet waves, X rays, and gamma rays (at shorter wavelengths than blue). Many insects see in ultraviolet while
reptiles see in infrared.
Reading check
Which type of electromagnetic radiation can be seen by humans?
The only kind of electromagnetic radiation the human eye can detect is visible light.
Observing Space, continued
Invisible Electromagnetic Radiation
In 1800, the scientist William Herschel discovered infrared, which means “below the red.”
Infrared is electromagnetic radiation that has waves longer than those of visible light.
The ultraviolet wavelengths, which are invisible to humans, are shorter than the wavelengths of violet light.
Ultraviolet means “beyond the violet.”
The X-ray wavelengths are shorter than the ultraviolet wavelengths. The shortest wavelengths are the gamma-ray
wavelengths.
The Electromagnetic Spectrum
Wave Characteristics
Telescopes
In 1609, an Italian scientist, Galileo, built a device that used two lenses to make distant objects appear closer and turned
it toward the sky.
telescope an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation
Telescopes that collect only visible light are called optical telescopes.
The two types of optical telescopes: 1) refracting telescopes and 2) reflecting telescopes.
Telescopes, continued
Refracting Telescopes
refracting telescope a telescope that uses a set of lenses to gather and focus light from distant objects
The bending of light is called refraction.
Refracting telescopes bens light that passes through their lens and focus the light to be magnified by an eyepiece.
One problem with refracting telescopes is that the lens focuses different colors of light at different distances causing the
image to distort.
Another problem is that it is difficult to make very large lenses of the required strength and clarity.
Telescopes, continued
Reflecting Telescopes
reflecting telescopes a telescope that uses a curved mirror to gather and focus light from distant objects
the light is reflected by a large curved mirror to a second mirror. The second mirror reflects the light to the eyepiece,
where the image is magnified and focused.
Unlike refracting telescopes, mirrors in reflecting telescopes can be made very large without affecting the quality of the
image.
Telescopes, continued
The diagram below shows refracting and reflecting telescopes.
Reading check, continued
What are the problems with refracting telescopes?
Images produced by refracting telescopes are subject to distortion because of the way different colors of visible light are
focused at different distances from the lens and because of weight limitations on the objective lens.
Telescopes, continued
Telescopes for Invisible Electromagnetic Radiation
Scientists have developed telescopes that detect invisible radiation, such as a radio telescope for radio waves.
One problem with using telescopes to detect invisible electromagnetic radiation is that Earth’s atmosphere acts as a
shield against many forms of electromagnetic radiation.
Ground-based telescopes work best at high elevations, where the air is thin and dry.
(http://www.almaobservatory.org/en/visuals/videos)
Space-Based Astronomy
Spacecrafts that contain telescopes and other instruments have been launched to investigate planets, stars, and other
distant objects
In space, Earth’s atmosphere cannot interfere with the detection of electromagnetic radiation.
Reading check
Why do scientists launch spacecraft beyond Earth’s atmosphere?
Scientists launch spacecraft into orbit to detect radiation screened out by Earth’s atmosphere and to avoid light
pollution and other atmospheric distortions.
Space-Based Astronomy, continued
Space Telescopes
The Hubble Space Telescope collects electromagnetic radiation from objects in space.
The Chandra X-ray Observatory makes remarkably clear images using X rays from objects in space, such as remnants of
exploded stars.
The Swift spacecraft detects gamma rays and X rays from explosions and collisions of objects such as black holes.
The James Webb Space Telescope is scheduled to be launched in 2013 to detect near- and mid-range infrared radiation
from objects in space.
Space-Based Astronomy, continued
Other Spacecraft
Since the early 1960s, spacecraft have been sent out of Earth’s orbit to study other planets.
The space probes Voyager 1 and Voyager 2 investigated Jupiter, Saturn, Uranus, and Neptune, and collected images of
these planets and their moons.
The Galileo spacecraft orbited Jupiter and its moons from 1995 to 2003.
Space-Based Astronomy, continued
Other Spacecraft, continued
The Cassini spacecraft began orbiting Saturn in 2004. In December 2004, the Huygens probe detached from the Cassini
orbiter to study the atmosphere and surface of Titan, Saturn’s largest moon.
The twin rovers Spirit and Opportunity landed on Mars in January 2004. They confirmed that water had once been
present on Mars.
In 2008, the Phoenix lander found ice on Mars.
Space-Based Astronomy, continued
Human Space Exploration
Spacecraft that carry only instruments and computers are described as robotic and can travel beyond the solar system.
The first humans went into space in the 1960’s. Between 1969 and 1972, NASA landed 12 people on the moon.
The loss of two space shuttles and their crews, the Challenger in 1986 and the Columbia in 2003, have focused public
attention on the risks of human space exploration.
Space-Based Astronomy, continued
Benefits of the Space Program
Satellites in orbit provide information about weather all over Earth.
Other satellites broadcast television signals from around the world or allow people to navigate cars and airplanes.
Inventing ways to make objects smaller and lighter so that they can go into space has also led to improved electronics.
Even medical equipment, like the heart pump, have been improved based on NASA’s research on the flow of fluids
through rockets.
Energy technology (fuels cells, solar panels)
Motion and the Solar System
Everything in the solar system is in constant motion
• Planets revolve around the sun: 1 revolution = 1 year
• Moons revolve around their planets: 1 revolution = 1 month
• All objects, even the sun, rotates on its axis: 1 rotation = 1 day
The Rotating Earth
rotation the spin of a body on its axis
Each complete rotation of Earth takes about one day.
As Earth rotates from west to east, the sun appears to rise in the east in the morning. The sun then appears to cross the
sky and set in the west.
At any given moment, the part of Earth that faces the sun experiences daylight. At the same time, the part of Earth that
faces away from the sun experiences nighttime.
The Revolving Earth
As Earth spins on its axis, Earth also revolves around the sun.
Even though you cannot feel Earth moving, it is traveling around the sun at an average speed of 29.8 km/s.
revolution the motion of a body that travels around another body in space; one complete trip along an orbit
Each complete revolution of Earth around the sun takes 365 1/4 days, or about one year.
The Revolving Earth, continued
Earth’s Orbit
The path that a body follows as it travels around another body is called an orbit.
Earth’s orbit around the sun is an ellipse, a squashed circle.
The Revolving Earth, continued
Earth’s Orbit, continued
Because its orbit is an ellipse, Earth is not always the same distance from the sun.
perihelion in the orbit of a planet or other body in the solar system, the point that is closest to the sun
aphelion in the orbit of a planet or other body in the solar system, the point that is farthest from the sun
The Revolving Earth, continued
The diagram below shows the Earth’s orbit.
The Rotating Earth, continued
The Coriolis Effect
The rotation of Earth causes ocean currents and wind belts to curve to the left or right. This curving is caused by Earth’s
rotation and is called the Coriolis effect.
Constellations and Earth’s Motion
A constellation is a group of stars that are organized in a recognizable pattern.
Evidence of Earth’s Rotation
Over a period of several hours, the constellations appear to have changed its position in the sky. The rotation of Earth on
its axis causes the apparent change in position.
Evidence of Earth’s Revolution
As Earth revolves around the sun, the night side of Earth faces in a different direction of the universe. Thus, as Earth
moves, different constellations are visible in the night sky from month to month and from season to season.
Constellations and Earth’s Motion, continued
The diagram below shows how constellations move across the sky.
Reading check
How does movement of the constellations provide evidence of Earth’s rotation and revolution?
Constellations provide two kinds of evidence of Earth’s motion. As Earth rotates, the stars appear to change position
during the night. As Earth revolves around the sun, Earth’s night sky faces a different part of the universe. As a result,
different constellations appear in the night sky as the seasons change.
Gravity and the Solar System
• Gravity is the force of the attraction between any two objects in the universe
• The amount of gravitational attraction between two objects depends on two things:
A. Their masses: The more massive an object, the greater its gravitational force
B. Their distance from each other: The closer two objects are, the more gravitational force they exert on each other
The Effects of Gravity on Orbits
• The Sun is the most massive object in the solar system. Its strong gravitational force keeps all planets in orbit around
it.
• The gravitational pull of each planet keeps their moons in orbit around them.
• Planets also exert force on each other. This pull makes their paths slightly oval, or elliptical.
• The sun’s gravitational pull on the moon also makes its orbit around Earth elliptical.
More Effects of Gravity
Tides and the Moon
All points on Earth have two high tides and two low tides daily
The moon’s gravitational force pulls most strongly on the waters directly below it and water surges forward creating
high tides
Water pulled from sides create low tides on either side 90⁰ away
An indirect high tide occurs 180⁰ from the moon
Tides and the Sun
The sun has less influence on tides since it’s much farther away
When the moon and sun are aligned,
their combined gravity creates especially
high tides
- Called Spring Tides
- 2x a month, at new and full moons
Measuring Time
Earth’s motion provides the basis for measuring time.
A day is determined by Earth’s rotation on its axis. Each complete rotation of Earth on its axis takes one day, which is
then divided into 24 hours.
The year is determined by Earth’s revolution around the sun. Each complete revolution of Earth around the sun takes
365 1/4 days, or one year.
A month was originally determined by the period between successive full moons, which is 29.5 days. However, the
number of full moons in a year is not a whole number. Therefore, a month is now determined as roughly one-twelfth of
a year.
Measuring Time, continued
Formation of the Calendar
A calendar is a system created for measuring long intervals of time by dividing time into periods of days, weeks, months,
and years.
Because the year is 365 1/4 days long, the extra 1/4 day is usually ignored. Every four years, one day is added to the
month of February. Any year that contains an extra day is called a leap year.
Measuring Time, continued
The Modern Calendar
Because the year is not exactly 365 days long, over centuries, the calendar gradually became misaligned with the
seasons.
In the late 1500s, Pope Gregory XIII formed a committee to create a calendar that would keep the calendar aligned with
the seasons. We use this calendar today.
In this Gregorian calendar, century years, such as 1800 and 1900, are not leap years.
Measuring Time, continued
Time Zone
Using the sun as the basis for measuring time, we define noon as the time when the sun is highest in the sky.
Earth’s surface has been divided into 24 standard time zones to avoid problems created by different local times.
The time in each zone is one hour earlier than the time in the zone to the east of each zone.
Measuring Time, continued
International Date Line
The International Date Line was established to prevent confusion about the point on Earth’s surface where the date
changes.
This imaginary line runs from north to south through the Pacific Ocean.
The line is drawn so that it does not cut through islands or continents. Thus, everyone living within one country has the
same date.
Measuring Time, continued
The diagram below shows the Earth’s 24 different time zones.
Reading check
What is the purpose of the International Date Line?
Because time zones are based on Earth’s rotation, as you travel west, you eventually come to a location where, on one
side of time zone border, the calendar moves ahead one day. The purpose of the International Date Line is to locate the
border so that the transition would affect the least number of people. So that it will affect the least number of people,
the International Date Line is in the middle of the Pacific Ocean, instead of on a continent.
Measuring Time, continued
Daylight Savings Time
Because of the tilt of Earth’s axis, daylight time is shorter in the winter months than in the summer months.
During the summer months, days are longer so that the sun rises earlier in the morning.
The United States uses daylight savings time. Under this system, clocks are set one hour ahead of standard time in
March, which provide an additional hour of daylight during the evening.
In November, clocks are set back one hour to return to standard time.
The Seasons
Earth’s axis is tilted at 23.5˚.
As Earth revolves around the sun, Earth’s axis always points toward the North Star.
The North Pole sometimes tilts towards the sun and sometimes tilts away from the sun.
When the North Pole tilts towards the sun, the Northern Hemisphere has longer periods of daylight than the Southern
Hemisphere.
When the North Pole tilts away from the sun, the Southern Hemisphere has longer periods of daylight.
The Seasons, continued
The diagram below shows how the seasons change with the Earth’s tilt.
The Seasons, continued
Seasonal Weather
Changes in the angle at which the sun’s rays strike Earth’s surface cause the seasons.
When the North Pole tilts away from the sun, the angle of the sun’s rays falling on the Northern Hemisphere is low.
This means the Northern Hemisphere experiences fewer daylight hours, less energy, and lower temperatures.
Meanwhile, the sun’s rays hits the Southern Hemisphere at a greater angle. Therefore, the Southern Hemisphere has
more daylight hours and experiences a warm summer season.
The Seasons, continued
Equinoxes
equinox the moment when the sun appears to cross the celestial equator
During an equinox, the sun’s rays strike the Earth at a 90° angle along the equator. The hours of daylight and darkness
are approximately equal everywhere on Earth that day.
The autumnal equinox occurs on September 22 or 23 of each year and marks the beginning of fall in the Northern
Hemisphere.
The vernal equinox occurs on March 21 or 22 of each year and marks the beginning of spring in the Northern
Hemisphere.
The Seasons, continued
Summer Solstices
solstice the point at which the sun is as far north or as far south of the equator as possible
The sun’s rays strike the Earth at a 90° angle along the Tropic of Cancer.
The summer solstice occurs on June 21 or 22 of each year and marks the beginning of summer in the Northern
Hemisphere.
The farther north of the equator you are, the longer the period of daylight you have.
The Seasons, continued
Winter Solstices
The sun’s rays strike the Earth at a 90° angle along the Tropic of Capricorn. The sun follows its lowest path across the sky
on the winter solstice.
The winter solstice occurs on December 21 or 22 of each year and marks the beginning of winter in the Northern
Hemisphere.
Places that are north of the Arctic Circle then have 24 hours of darkness. However, places that are south of the Antarctic
Circle have 24 hours of daylight at that time.
What Causes Earth’s Seasons?
• Earth’s axis is tilted at 23.5 ⁰ It always points in the same direction in space. This causes hemispheres to alternate in
amount of light and heat they receive
Lunar Phases
• The moon revolves around the
Earth once every 29.5 days.
• It has no light of its own, what
we see is reflected sunlight
• The moon’s shape appears to
change because different
amounts of the illuminated
side of the moon are facing us
New Moon - the moon is between
the sun and the Earth
Waxing – moon is growing
Full Moon - the Earth is between
the sun and moon
Waning - shrinking phases
Eclipses
Eclipses occur when the Earth, sun, and moon line up and the shadow of one covers, or eclipses, the other
Solar Eclipses
• Occur when moon passes between sun and Earth
(Sun-Moon-Earth)
•Moon crosses in front of sun
• Only occurs during new moons
Lunar Eclipses
•Occur when Earth passes between sun and moon
(Sun-Earth-Moon)
•Earth’s shadow falls on the moon
• Only occurs during full moons