Transcript NATS1311 From the Cosmos to Earth

NATS1311 From the Cosmos to Earth
Properties of Waves
Period: time to complete one cycle of vibration
(From 1 to 5)
Frequency (f): number of crests passing a fixed point
per second
Frequency= 1/period
Example:
Period = 1/100 = 0.01 sec.
Frequency = 100 hertz (cycles/sec.)
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Amplitude (a): maximum displacement from
Equilibrium
Wave length (l): distance between successive crests
(2 to 6, 4 to 8, etc...)
Speed (of a wave) (s)= wave length x frequency
s= l x f
NATS1311 From the Cosmos to Earth
TYPES OF WAVES
Transverse:
Vibration or oscillation is perpendicular to direction
of propagation of wave.
Examples: water wave, vibrating string
Longitudinal:
Vibration or oscillation is in the same direction as
propagation of wave.
Examples: sound waves, mass on a spring,
loudspeaker
NATS1311 From the Cosmos to Earth
ELECTROMAGNETIC WAVES (LIGHT WAVES)
Velocity
186,000 miles/second
300,000 kilometers/second
3 x 1010 cm/second
• It takes 1 1/3 second for light to travel from the earth
to the moon.
• It takes 8 1/3 minutes for light to travel from the sun
to the earth.
NATS1311 From the Cosmos to Earth
ELECTROMAGNETIC WAVES (LIGHT WAVES)
Speed of propagation of a light wave:
c=lxf
c = velocity of light; c is a constant in vacuum
l = wavelength of a light wave - distance between
successive crests
f = frequency of a light wave - number of crests
passing a fixed point in 1 second
NATS1311 From the Cosmos to Earth
PHOTON
• Light propagates as quanta of energy called photons
• Photons
•move with speed of light
•have no mass
•are electrically neutral
• Energy of a photon or electromagnetic wave:
E = hf = h c/ l
where
h = Planck’s constant
f = frequency of a light wave - number of
crests passing a fixed point in 1 second
c = velocity of light
l = wavelength of a light wave distance between successive crests
NATS1311 From the Cosmos to Earth FIG. 6.4
Figure 6.4 The electromagnetic spectrum. The unit of
frequency, hertz, is equivalent to waves per second. For
example, 103 Hz means that 103 wave peaks pass by a
point each second.
NATS1311 From the Cosmos to Earth
Absorption and Emission. When electrons jump from a low energy shell
to a high energy shell, they absorb energy. When electrons jump from
a high energy shell to a low energy shell, they emit energy. This
energy is either absorbed or emitted at very specific wavelengths,
which are different for each atom.
When the electron is in a high energy shell,t he atom is in an excited state.
When the electron is in the lowest energy shell, the atom is in the ground
state.
NATS1311 From the Cosmos to Earth
The Hydrogen Atom. The hydrogen atom is the simplest of atoms. Its
nucleus contains only one proton which is orbited by only one electron.
In going from one allowed orbit to another, the electron absorbs or emits
light (photons) at very specific wavelengths.
NATS 1311 From the Cosmos to Earth Fig.6.6
Figure 6.6 (a) Photons
emitted by various
energy level transitions
in hydrogen. (b) The
visible emission line
spectrum from heated
hydrogen gas. These
lines come from
transitions in which
electrons fall from
higher energy levels to
level 2. (c) If we pass
white light through a
cloud of cool hydrogen
gas, we get this
absorption line
spectrum. These lines
come from transitions
in which electrons
jump from energy level
2 to higher levels.
NATS 1311 From the Cosmos to Earth
Kirchhoff’s Laws of Radiation
First Law. A luminous solid, liquid or gas, such as a light bulb filament,
emits light of all wavelengths thus producing a continuous spectrum
of thermal radiation.
Second Law. If thermal radiation passes through a thin gas that is
cooler than the thermal emitter, dark absorption lines are superimposed
on the continuous spectrum. The gas absorbs certain wavelengths.
This is called an absorption spectrum or dark line spectrum.
Third Law. Viewed against a cold, dark background, the same gas
produces an emission line spectrum. It emits light of discrete
wavelengths. This is called an emission spectrum or bright line
spectrum.
.
NATS 1311 From the Cosmos to Earth Fig.6.11
Fig. 6.11 This diagram illustrates Kirchhoff’s laws of
radiation.
NATS1311 From the Cosmos to Earth FIG. 6.19
Figure 6.19 The basic design of a spectrograph.
NATS 1311 From the Cosmos to Earth Fig. 6.7
Figure 6.7 Emission line spectra for helium, sodium, and
neon. The patterns and wavelengths of lines are different for
each element, giving each a unique spectral fingerprint.
NATS 1311 From the Cosmos to Earth Fig. 6.13
Figure 6.13 The Doppler
effect. (a) Each circle
represents the crests of
sound waves going in all
directions from the train
whistle. The circles
represent wave crests
coming from the train at
different times, say, 1/10
second apart. (b) If the
train is moving, each set
of waves comes from a
different location. Thus,
the waves appear
bunched up in the
direction of motion and
stretched out in the
opposite direction. (c)
We get the same basic
effect from a moving light
source.
NATS 1311 From the Cosmos to Earth Fig. 6.14
Figure 6.14 Spectral lines provide the crucial reference
points for measuring Doppler shifts.
NATS1311 From the Cosmos to Earth
Lenses and Mirrors
Object distance: do distance from lens or mirror to object.
Image distance: di distance from lens or mirror to image
Focal length: Distance from lens or mirror to image when
the object is at infinity (a long distance away).
Lens formula:
1 1 1
 
f do di
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Lens and Mirror Aberrations
SPHERICAL (lens and mirror)
Light passing through different parts of a lens or reflected from
different parts of a mirror comes to focus at different distances
from the lens.
Result: fuzzy image
CHROMATIC (lens only)
Objective lens acts like a prism.
Light of different wavelengths (colors) comes to focus at
different distances from the lens.
Result: fuzzy image
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth FIG. 6.15
Figure 6.15
(a)The basic
design of a
refracting
telescope.
(b) The 1meter
refractor at
the University
of Chicago's
Yerkes
Observatory
is the world's
largest
refracting
telescope.
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth FIG. 6.17
Figure 6.17 Alternative designs for reflecting telescopes.
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth FIG. 6.20
Figure 6.20 Observatories on the summit of Mauna Kea in Hawaii.
The twin domes near the far right house the two Keck telescopes.
NATS1311 From the Cosmos to Earth FIG. 6.25
Figure 6.25 The Arecibo radio telescope in Puerto Rico is
the world's largest single radio dish.
NATS1311 From the Cosmos to Earth FIG. 6.21
Figure 6.21 This
diagram shows
the basic
components of the
Hubble Space
Telescope, which
orbits the Earth.
The entire
observatory is
roughly the size of
a school bus.
NATS 1311-From the Cosmos to Earth
Solar System
% Mass of Solar System
Sun
99.85%
Jupiter
00.10%
Others
00.05%
Terrestrial Planets:
•Mercury, Venus, Earth, Mars
– Rocky, Silicates, Metals
Jovian Planets:
•Jupiter, Saturn, Uranus, Neptune, Pluto (icy moon)
– Gases, Liquids
NATS 1311-From the Cosmos to Earth
Solar System
Figure 7.1 Side view of the solar system. Arrows indicate the orientation of the
rotation axes of the planets and their orbital motion. (Planetary tilts in this
diagram are aligned in the same plane for easier comparison. Planets not to
scale.) Seen from above, all orbits except those of Mercury and Pluto are
nearly circular. Most moons orbit in the same direction as the planets orbit and
rotate--counterclockwise when seen from above Earth's North Pole.
NATS1311 From the Cosmos to Earth
Full
moon
NATS1311 From the Cosmos to Earth
Moon
Distance from earth:
Diameter:
Mass moon/mass earth:
Density:
Gravity:
238,000 miles
2100 miles (1/4 earth)
0.012
3.34 gm/cm3
1/6 that of earth
NATS1311 From the Cosmos to Earth
Moon
Appearance:
Highlands - heavily cratered
Maria- smoother
Mountain ranges
Rilles - clefts in surface
Craters
Diameter 200 miles to 1 millimeter
Rims higher than grand canyon
Rotation - phase locked to earth
Synodic period - 29 1/2 days
Sidereal period - 27 1/3 days
Surface - igneous rocks - cooled lava
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Apollo 17
Lunar Mass
Spectrometer
on surface of
moon.
Close-up of mass spectrometer on lunar surface.
Apollo 17 mass spectrometer found principal gases
in atmosphere to be hydrogen, neon and argon.
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
South pole of moon
NATS1311 From the Cosmos to Earth
South pole craters
NATS1311 From the Cosmos to Earth
Silver
spur
NATS1311 From the Cosmos to Earth
Lunar
rover
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Earthrise as seen from the
moon
NATS1311 From the Cosmos to Earth
Apollo lunar exploration results
1. Surface composition
Earth - like rocks but not exactly
Basalt - rapidly cooled lava - abundant on
Earth
Anorthosite- more slowly cooled lava- found
Principally in adirondac mountains
Breccias - mixture of fragments of other
types of rocks
Kreep - potassium, rare earth, phosphorus
Rocks found in highlands mounts
Soils - contain tiny glass beads - elements with
High melting points
No water
Regolith - ground up rock
NATS1311 From the Cosmos to Earth
2. Chronology
Moon formed 4.6 billion years (by) ago
Oldest rocks - 4.4 by
Youngest rocks - 3.1 by
Volcanism from 3.8 to 3.1 by ago internal heating
Moon dead for last 3.1 by
3. Interior
Core - probably molten metal
Mantle - silicate materials
Crust
40 mile thick on near side
80 mile thick on far side
Mascons - regions of high gravity under the maria
NATS1311 From the Cosmos to Earth
4. Origin - 4 theores, first three have problems listed below
each theory
1. Fission - moon split off from earth chemical dissimilar low iron in moon angular momentum
2. Capture - came from elsewhere in solar system orbital
mechanics chemical similarities - low iron in moon
3. Double planet - both formed locally chemical
differences angular momentum
NATS1311 From the Cosmos to Earth
4. Giant lmpact - Body 10% size of earth impacted
young earth at a grazing angle. Melted but
threw off layer of material that condensed into
moon. ~
Most likely theory.
5. Atmosphere
Very rarified
Pressure: one 100th of one trillionth of earth
(10-14 of earth)
A very good vacuum
Composition: mostly noble gases
NATS 1311 From the Cosmos to Earth Fig. 7.9
Figure 7.9 Artist's conception
of the impact of a Mars-size
object with Earth, as may have
occurred soon after Earth's
formation. The ejected
material comes mostly from
the outer rocky layers and
accretes to form the Moon,
which is poor in metal.
NATS1311 From the Cosmos to Earth
Mercury
Property
Earth
Mercury
1
0.4
5.5
5.4
1
0.4
365
88
1
59
23.5°
7°
Inclination of orbit to ecliptic plane
0°
7°
Maximum angle from sun
~
28°
Surface temperature
~
Day: 800°F
~
Night: -280°F
1 atmosphere
10-15 atmosphere
N2, O2
Helium, sodium,
potassium, oxygen
Equatorial Diameter
Density (gm/cm3)
Avg. Distance from Sun (AU)
Orbital Period (days)
Sidereal Rotation Period (days)
Inclination of axis to orbital plane
Atmosphere - pressure
Atmosphere - composition
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
The orbit of Mercury
At an average distance of only 58 million kilometers (36
million miles) from the sun, mercury takes a mere 88 days
to go around its orbit.
As viewed from earth, mercury can be seen only near times
of greatest eastern or western elongation.
At greatest western elongation (when the planet is farthest
west of the sun in the sky), mercury rises about 1 1/2
hours before sunrise.
At greatest eastern elongation (when the planet is farthest
east of the sun in the sky), mercury sets about 1 1/2 hours
after sunset.
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Mariner 10 view of Mercury, March 29,1974 from
125,000 miles away
NATS1311 From the Cosmos to Earth
Mercury, Mariner 10
photo.
Large valley to right is
4 miles wide and 60
miles long.
It leads into crater 50
miles in diameter.
NATS1311 From the Cosmos to Earth
Mercury.
Picture taken form
3700 miles away.
Relatively level surface
resembles mare
regions of moon.
NATS1311 From the Cosmos to Earth
Mercury.
Long scarp
diagonally
across
picture.
NATS1311 From the Cosmos to Earth
Mercury.
Crater at lower
left is 40 miles
in diameter.
Slows flow
front extending
across crater
floor.
NATS1311 From the Cosmos to Earth
Differences between the Moon and Mercury
1. Areas between craters on Mercury smoother than on Moon.
2. Secondary impact craters don't scatter as much on Mercury.
3. Gravitational acceleration on Mercury twice that of moon.
4. Mercury has scarps - caused by shrinkage of its surface.
5. Mercury's atmosphere consists of sodium and potassium
(sputtered form surface by the solar wind), helium and
oxygen.
6. Atmospheric pressure about the same as on the Moon.