Lecture 13: Lecture 12: Non-optical Astronomy

"...and I say to myself, what a wonderful world."
Louis Armstrong

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Date: October 18, 1994
Reading Assignment: pp. 38-151

Description : introduction to the Earth's hydrosphere, magnetosphere and atmosphere

Objectives

understand and be able to list the main structural parts of Earth

understand what the hydrosphere is

be able to explain tides

understand the magnetosphere

distinguish between the Ozone layer and the Greenhouse effect

Lecture Outline

Slide # 1: Lecture 11: Telescopes- All the Better to See You With

Click here for subtitle

refractors and reflectors

image detectors

why use telescopes?

Slide # 2: The Electromagnetic Spectrum

Radio

Infrared

Visible

Ultraviolet

X-ray

Gamma-ray

Slide # 3: Image Detectors- Optical

the eye

photographic plates

CCD detectors

Slide # 4: Why use a telescope?

magnification

resolution

light gathering ability

Slide # 5: High Resolution Astronomy

telescope in space

adaptive optics

interfereometry

Slide # 6: Telescopes in Space

Hubble Space Telescope

resolution 0.05 arcseconds

20x better than normal telescopes on the ground

Slide # 7: Telescopes in Space

the atmosphere is opaque to most parts of the EM spectrum

orbiting satellites can be used to observe

infrared

ultraviolet

X-ray

Gamma Ray

MOST orbiting astronomical satellites are NOT optical

Slide # 8: Interferometry

combine light from many telescopes

different blurring at each telescope

Slide # 9: Radio Interferometry

radio telescopes routinely use interfereometry

Slide # 10: Lecture 13: The Earth and its Atmosphere

hydrosphere and tides

atmosphere

ozone layer and greenhouse effect

magnetosphere

Slide # 11: Earth: The Big Picture

radius = 6378 km

mass = 6.0 x 1027 grams

Slide # 12: Density and Volume

mass/volume = density

volume = 4 x Pi X R3 / 3

volume of Earth = about 1027 cm3

Density of Earth = 5.5 gm/cm3

Slide # 13: Shape of the Earth

Almost a sphere

Rotation causes the Earth to bulge at the Equator

Slide # 14: Effects of Rotation

rotation flattens the poles

Slide # 15: The Effect of Rotation on Earth

40 km difference in diameters

EarthÕs diameter is about 13,000 km

Slide # 16: EarthÕs Structure

core

mantle

crust

hydrosphere

atmosphere

magnetosphere

Slide # 17: Hydrosphere

the oceans of Earth

approximately 70% of the surface

average depth 3.6 km

mostly in the oceans

2% in lakes, rivers, glaciers, and clouds

regulates temperature on Earth

Essential to LIFE!

Slide # 18: Tides

the ocean rises and falls twice a day

most areas have tides of about 1 meter

some areas have 20m tides

Slide # 19: The Cause of Tides

The MoonÕs and SunÕs gravity cause tides

The force of gravity depends on

distance between objects

mass of the objects

Slide # 20: Cause of Tides

opposite sides of the Earth have different distances to the Moon

Slide # 21: Causes of Tides

different points on Earth have different gravitational forces from the Moon

Slide # 22: Cause of Tides

distant objects feel less force than close objects

Slide # 23: Cause of Tides

the gravity at #1 > the gravity at #2

the gravity at #2 > the gravity at #3

Slide # 24: Tides

Tides are caused by the DIFFERENCE in forces across the Earth

Slide # 25: Tides

the Earth is deformed by the MoonÕs and SunÕs gravity

this is in addition to the rotation effects

Slide # 26: Is Earth actually distorted by the Moon?

yes- the diameter of Earth changes by a few centimeters

the oceans are affected more

Slide # 27: Sun and Moon

at times, the Sun and Moon are aligned

alignment produces bigger tides

the bigger tides are called Spring Tides

Slide # 28: Alignments

Spring tides occur at New and Full Moon

Slide # 29: Neap Tides

the Moon, Earth and Sun are at right angles

a lower than average tide occurs

forces partially cancel

Slide # 30: Neap Tides

Neap Tides occur at 1st and 3rd quarter

Slide # 31: Rotation and Tidal Forces

Tides distorts the Earth

Friction and rotation cause the bulge to be slightly ahead of the Moon

the off-center bulge slows the rotation

Slide # 32: Longer Days?

fossils indicate a day was about 22 hours 500 Myr ago

the Moon is moving farther away and the Earth is slowing down

eventually Earth will be Òtidally lockedÓ with the Moon

Slide # 33: Tides on the Moon

the gravity from the Earth causes tides on the Moon

the tidal forces have stopped the MoonÕs rotation

the Moon is Òtidally lockedÓ with the Earth

Slide # 34: The Atmosphere- a darn useful thing to have

the air we breath

protection from high energy EM radiation

protection from meteors

Slide # 35: The EarthÕs Atmosphere

78% Nitrogen

21% Oxygen

0.9% Argon

0.03% Carbon Dioxide

Water Vapor 0.1 to 3 percent

Slide # 36: Oxygen

Unique in the Solar System

Slide # 37: Atmospheric Layers

troposphere

lowest layer- <15 km

weather zone

air cools and thins with altitude

Slide # 38: Atmospheric Layers

stratosphere

15km to 40km

ozone layer

mesosphere

40km - 90km

thermosphere

> 90 km

Slide # 39: The Ozone Layer

in upper stratosphere, oxygen is found as O3

O3 is called Ozone

Ozone is opaque to most UV and X-ray photons

Slide # 40: Ozone

most X-rays and UV are blocked by the Ozone layer

X-rays and UV are bad for life on Earth

Slide # 41: Destruction of the Ozone Layer

freon and chlorofluorocarbons destroy Ozone

one freon molecule destroys millons of Ozone molecules

Slide # 42: The Ozone Hole

near the South Pole, most of the Ozone layer has been destroyed

Slide # 43: Surface Heating of Earth

Earth is warm mostly from the SunÕs energy

sunlight strikes Earth and is absorbed

Earth warms

Earth radiates as a Black-Body

Slide # 44: A Balance Between Radiation and Absorption

energy radiated = energy absorbed

(on average)

Slide # 45: The Temperature of Earth

without the Atmosphere, Earth would have an average temperature of -23C

the average temperature is about 10C

Slide # 46: The Greenhouse Effect

carbon dioxide and water vapor block infrared radiation

most of the SunÕs energy is visible light

most of the EarthÕs radiated Energy is infrared

Slide # 47: The Greenhouse Effect

visible light passes through the atmosphere

Slide # 48: The Greenhouse Effect

the light is absorbed by the Earth

Slide # 49: The Greenhouse Effect

the Earth warms up and radiates infrared energy

Slide # 50: The Greenhouse Effect

Most of the Infrared Energy is blocked by the water vapor and carbon dioxide

Slide # 51: The Greenhouse Effect

the Earth absorbs the extra infrared energy

the Earth heats up a bit more

Earth is about 40K hotter than the Moon because of our atmosphere

Slide # 52: The Runaway Greenhouse Effect

the amount of carbon dioxide in the atmosphere is increases 4% per decade

global temperatures are slowly rising

the global climate is being altered by MAN

Slide # 53: Origin of the Atmosphere

primary atmosphere- Hydrogen and Helium

gases common in the solar system

escaped from Earth

secondary atmosphere

volcanic outgassing

Nitrogen, CO2, sulfur dioxide, wator vapor, methane

most of these gases are trapped in rocks now

Slide # 54: The Current Atmosphere

early plant life changed most of the CO2 into O2

ozone layer formed from the oxygen

Slide # 55: Why is the sky blue?

dust particles scatter more blue light than red

Slide # 56: Sunset

red light passed through atmosphere

most blue light is scattered

Slide # 57: The Magnetosphere

the EarthÕs Magnetic Field

Slide # 58: The Magnetosphere

high energy particles are trapped by the magnetic field

radiation zones form

the Van Allen belts

Slide # 59: Aurora

the magnetic field traps particles from the ÒSolar WindÓ

the particles strike atmosphere near the Poles

Northern and Southern lights result

Slide # 60: Magnetosphere

also protects Earth from high energy particles