Transcript Unit 8 Chapter 26 Studying Space

Unit 8 Chapter 26
Studying Space
Section 1 Viewing the Universe
Astronomy is the study of the universe
Astronomer is the scientist that does the studying
The Value of Astronomy
As new things are discovered in space like Black Holes, new planets, stars and
nebula, scientists can use that information to learn about Earth. Scientists
have been able to piece together the processes that involve the formation of
our planet, the solar system and the universe.
Characteristics of the Universe
Cosmology is the study of the origin, properties, processes and evolution of the
universe.
The Universe began approximately 13.7 billion years ago in what we feel was a
“Big Bang”.
Organization of the Universe
Our nearest part of the universe is our solar system. Our solar system is part
of a galaxy which is a collection of stars, dust, gas and other objects bound
together by gravity.
Our galaxy name is the Milky Way (candy named after it).
Measuring Distances in the Universe
Astronomical Unit (A.U.) is the average distance from the earth to the sun
which is 149,597,870.691 km (150 million)
Light Year measures the distance that a ray of light travels in one year, which is
approximately 9.46 X 1012 km
1 light year = 9.5 X 1012 km
1 A.U.
= 1.5 X 108 km
This means that there are 6033 X 104 A.U.’s per light year.
The next closest object to us aside from out sun is approximately 4.22 light
years away.
Electromagnetic Spectrum
Spectroscope/Spectrograph
It is an instrument that uses prisms to split light, a special
telescope and a special camera to look at stars. Each star emits its
own spectrum because each star is made of different elements
and each element emits a different wavelength.
Continuous SpectrumThey are an unbroken band of color which shows that the source is emitting all
visible wavelengths. It can be either a glowing solid (hot filament of light bulb)
or a glowing liquid (molten iron, lava) or a hot compressed gas.
Emission SpectrumThese are unevenly spaced lines of different colors and brightnesses. Bright
lines mean light of only certain wavelengths can be glowing thin gasses
(Florescent bulbs).
Absorption SpectrumIt is a continuous spectrum crossed by dark lines. This happen when
light passes through a cooler gas, actually the elements in the gas absorb
exactly the same wavelengths that they would emit if they were hot and
glowing.
Visible Electromagnetic Radiation
Visible Spectrum is the part of the electromagnetic spectrum that human
eyes can see. We see the colors of a rainbow, Red (longest), Orange, Yellow,
Green, Blue and Violet (shortest). White light is made up of all of the colors in
the spectrum.
Color shifts are used to visualize the movement of objects toward and away
from the observer. We use this when we work with meteorological maps and
viewing objects in space. In labs the changes are either to the red or the blue
side of the spectrum.
RED SHIFT- SHOWS THERE IS AN INCREASING distance
There is a wavelength increase
BLUE SHIFT- shows there is a decreasing distance
There is a wavelength decrease
Erwin Hubble discovered that most stars are red shifted. It means that all
stars are moving apart and the universe is expanding
Invisible Electromagnetic Radiation
Invisible radiation is the radiation that we can not see but we can feel it and
experience it. It will usually involve a temperature rise. In the 1800 William
Heschel discovered that there was a rise in temperature in the red end of the
spectrum if you placed a thermometer in it, hence the name Infrared, which
means below red.
Doppler Effect is the apparent change in the frequency of an object as it moves
towards or away from an observer. It can be sound or light.
Example- The sound of a siren as it comes towards you and then moves
past you. The pitch grows higher as the vehicle approaches it compresses and
makes the wavelength shorter (higher pitched) as the vehicle goes away from you the
wavelengths increase in size and the pitch drops.
Telescopes
A Telescope is used to help our eyes see further and
more clearly into space. Although he was not the
first to make it, Galileo was the first to use it to see
the “heavens”, since it was originally used to look for
ships and pirates. They gather more light than our
eye can and can magnify images.
The best place to use a telescope is in a place that is
away from light and as high as possible. Why?
Refracting Telescopes
Refracting Telescopes use two lenses to bend and then focus the light.
The bad thing about them is that it is hard to make big lenses for the
instruments, so they tend to be smaller. Also if you focus in on one color, you
will be out of focus in another.
Reflecting Telescopes
Reflecting Telescopes use a curved mirror to focus the light and an eyepiece
lens to magnify the image. Sir Isaac Newton first introduced this. These
telescopes are usually about 10 meters in diameter. The Keck telescope in
Hawaii is the largest of these so far. If smaller multiple mirrors are used instead
of one big one it is called a Multiple Mirror Telescope (MMT).
Astronomers are planning are making larger ones. An ELT, Extremely Large
Telescope at about 50meters and the OWL, Overwhelmingly Large Telescope
at about 100 meters are in the works.
Telescopes for Invisible Electromagnetic Radiation
A Radio telescope uses radio waves instead of light. It collects the sound
waves from space and transmits them into an instrument that looks like a dish.
In New Mexico there is an array of them able to act as one, the Very Large
Array (VLA). This enables astronomers to hear radio waves from outer space
(like the movie Contact).
Space Based Astronomy
In Space, Earth’s atmosphere can not interfere with the detection of
electromagnetic energy.
Space Telescopes
Hubble Telescope
A telescope launched in space from the space shuttle that enables us to see 12
billion light years away. Named after Erwin Hubble who discovered that most
(all) stars is red shifted
Other Spacecraft
Since the 1960’s we have been sending things into space to do the exploring for
us.
1977 Voyager 1 and Voyager 2 investigated Jupiter, Saturn, Uranus & Neptune
1995-2003 Galileo orbited Jupiter
2004 Cassini orbited Saturn
2004 Huygens studied the surface of Titan
2004 Mars rovers Spirit and Opportunity landed
2008 Phoenix found ice on Mars
Human Space Exploration
The first humans went into space in the 1960’s. Between 1969 and 1972 12
humans have landed on the moon. NASA is still researching and sending
crews out to space stations now.
Spin-offs of the Space Program
We have satellites that we use to help us see and hear things better, for
commercial or government use. Medical equipment is also being experimented
on in the space station for use on earth.
Section 2 Movement of the Earth
If we can understand the motions of the Earth, we can understand the
motions of other bodies in our solar system.
The Rotating Earth
The earth rotates counter clockwise as seen from above the North Pole
(from west to east).
The earth rotation and its tilt also cause:
changes in the amount of sunlight per day
length of the day (24 hours)
direction of the sunset;
Summer – north of West
Winter – south of West
direction of sunrise;
Summer – north of East
Winter – south of East
Apparent movement of the sun across the Sky
The earth is 40,074 km at the Equator, it rotates 15o/hr therefore it must rotate
1670 km/hr. At the north and South Pole, it rotates at the grand speed of 0
km/hr. At 41o N Lat. It is approximately 1325 km/hr.
The Foucault Pendulum
In 1851 Jean Foucault constructed a freely swinging pendulum that appeared to
change its direction in a very predictable manner. The pendulum appeared to move
15o per hour.
The Coriolis Effect
Objects in the Northern Hemisphere appear to go to the right
Objects in the Southern Hemisphere appear to go to the left
The Revolving Earth
As Earth spins on its axis, it also travels around the sun. The average
speed of the orbit is approximately 29.8km/s which takes us about 365 ¼ days
to go around the sun.
Earth’s Orbit
Because the earth’s orbit isn’t a perfect circle we are closer in the winter
and further away in the summer.
Aphelion-July 4 furthest from the sun
Perihelion Jan. 2 closest to the sun
http://www.windows2universe.org/physical_science/physics/mechanics/orbit/perihelion_
aphelion.html
Constellations and Earth’s Motions
Evidence of Earth’s motions can also be seen in the motions of
the constellations.
Constellations
Are groups of stars that seem to form an object or Pattern.
They were named for mythic heroes. 88 constellations can be
seen from Earth’s northern and southern hemispheres.
Evidence of Earth’s Rotation
All stars appear to move in an arc in the sky except for Polaris.
Why
____________________________________________________
Evidence of Earth’s Revolution
Not only does the daily position of celestial objects change, the
position changes throughout the year, why?
___________________________________________________
Measuring Time
Earth’s motion provides the basis for measuring time. Each day is
divided into 24 hours.
A year is divided into 365 ¼ days and a month was based on the
cycle of the moon which was approximately 29.5 days. Now it is
based on being 1/12th of the year.
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 about 365 1/4 days long, the extra 1/4 day is
usually ignored to make the number of days on a calendar a
whole number. To keep the calendars on the same schedule as
Earth's movements, we must account for the extra time. So, every
four years, one day is added to the month of February. Any year
that contains an extra day is called a leap year.
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 unless the
century years are exactly divisible by 400. Thus, 2000 was a leap
year even though it was a century year. However, 2100, 2200, and
2300 will not be leap years.
Time Zones
Standard time zones the world is divided in 24 different time zones each
15o of longitude, called time meridian.
International Date Line
International Date Line – because of the changes of time either ahead or back,
people can lose or gain a whole day. This line (imaginary) represents where the
date will change.
West – one day ahead
East – one day earlier
Daylight Savings Time
Because there is a different amount of day light hours in the winter and
summer, the United States decided to adjust out clocks to accommodate this.
We turn our clocks ahead in the spring, in which we lose an hour of time, and
then we fall back, in which we gain an hour. This was due to help with the
energy crisis.
The Seasons
Since our axis is tilted about 231/2o off of perpendicular this which means that a
different area of the earth receives different amounts of light each day. And since it
takes us 12 months to complete a revolution around the sun, it takes approximately 3
months to change the area being exposed.
Seasonal Weather
As the Earth moves, it causes changes in the area exposed which creates
different weather in areas on the earth. So the seasons are caused by the tilt
of Earth's axis and not by Earth's distance from the sun.
Equinoxes
Spring – March 21st (Vernal)
Fall – September 23rd (Autumnal)
Sun is directly above the equator, 12 hrs of daylight all over the earth
Sun Sets directly West and Rises directly East
Summer Solstice
Summer Solstice (June 21st)
Direct rays of the sun on Tropic of Cancer
23 1/2o North Latitude
15 hrs of daylight on L.I. (sunrise N. of E.)
24 hrs of daylight on the North Pole
12 hrs of daylight on the Equator
0 hrs of daylight on the South Pole
Winter Solstice
Winter Solstice (December 21st)
Direct rays of the sun on Tropic of Capricorn
23 1/2o South Latitude
9 hrs of daylight on L.I. (sunrise S. of E.)
0 hrs of daylight on the North Pole
12 hrs of daylight on the Equator
24 hrs of daylight on the South Pole
Zenith – point directly over head
The sun is NEVER at the zenith
anywhere in
the contiguous U.S.
Altitude – suns angle with the horizon
The altitude is measured in degrees
from the observer’s horizon to the
object. There are 900 from the horizon
to the Zenith.