# Empty Space

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```					                                Senior Science

Module 9.9 ::: Space

Section 1

Empty Space

While the atmosphere has limits there is no such thing as ‘empty’ space

9.9.1.a    Discuss the concept of the atmosphere in relation to the distribution or
concentration of particles of gas

9.9.1.b    Identify that the Earth’s atmosphere is largely maintained in place by the
earth’s gravitational pull

9.9.1.c    Discuss why there is no such thing as ‘empty space’

9.9.1.i    Gather, process and present information from secondary sources to model
the relative distance of particles in a solid, liquid, gas and in space
9.9.1.a       Discuss the concept of the atmosphere in relation to the distribution or
concentration of particles of gas

CONCENTRATION OF GASES IN THE ATMOSPHERE

What to do

Read the information (dot points) about the atmosphere.
•   The atmosphere is the mixture of gases that surrounds the Earth.
•   Gravity holds the gases of the atmosphere close to the earth.
•   The higher up the thinner the atmosphere (ie less gas particles in the same volume)
•   Below 80 kilometres the atmosphere is roughly uniform (ie a similar ratio of gases
everywhere) and this layer is called the Homosphere.
•   Three of the more important gases in the Homosphere are Nitrogen (78%), Oxygen
(21%) and Carbon dioxide (0.04%).
•   In the homosphere, the gases are well mixed by convection and turbulence.
•   Most water vapour occurs below 12 kilometres.
•   Amount of water vapour in the atmosphere varies (daily) greatly below 12 kilometres.
•   80% of the air in the atmosphere occurs in the homosphere.
•   The ozone layer extends from about 20 – 50 kilometres above sea level.
•   A 10km thick section of the ozone layer would measure a few millimetres at sea level.
•   NASA regards above 80 kilometres as being in space.
•   Orbiting satellites can stay in orbit around the Earth for very long periods of time above
80 kilometres. This is because the atmosphere is so thin it creates very little drag on
the satellite.
•   Above the homosphere (above 80 kilometres) is the heterosphere.
•   The composition of the heterosphere is very different to the homosphere.
•   At heights above 80 km the atmospheric composition differs greatly from sea level.
•   The gases in the heterosphere do not mix much.
•   Turbulent mixing is absent in the heterosphere and diffusion determines composition.
•   The heterosphere consists of layers with lighter gases higher up (gaseous stratification
occurs in relation to the molecular weights of individual gases).
•   There are larger proportions of gases of low (molecular) weight (eg helium).
•   The atmosphere becomes thinner with increasing height above the Earth.
•   The Heterosphere (atmosphere) gradually fades into space, where it meets the solar
wind – that is a continuous stream of charged particles from the sun.
•   These charged particles given off by the sun are captured by the Earth’s magnetic field.
•   As well the atmosphere is affected by cosmic, solar ultraviolet and X-ray radiation
•   Gases of the lower atmosphere screen out these radiations.
•   The solar wind and the radiation cause particles in the heterosphere to be ionised
(separation of electrons from atoms, leaving a positively charged ion).
•   Collisions between these charged particles and the atmosphere produce light.
•   This results in natural light displays called the Auroras.
•   The Auroras are produced by the penetration of ionising radiation through the
atmosphere about 300km to about 80 km, particularly in the Polar Regions. The
display in the Southern Hemisphere is called Aurora Australis or Southern Lights.

Notes Questions
1. What is the atmosphere?
2. Where is the atmosphere thickest?
3. Is there much water vapour above 80 km?
4. In which part of the atmosphere do gases mix?
5. What causes the Auroras?
6. How high is the atmosphere?
7. Where does the atmosphere end?
8. Where does space start?
9. Draw a diagram of the atmosphere’s structure.
• Label the diagram with the following words – Homosphere, Heterosphere, Ozone
layer; most water vapour, and others that are appropriate
• Indicate heights above sea level on the diagram – 0, 80, 300 etc
• Indicate thicker parts of the atmosphere by using more dots.

•   Describe the distribution of particles of gas.

HSC Style Question

Discuss the concept of the atmosphere in relation to the distribution of particles of gas.
This question requires an extended answer. In order to answer such a question, you must
provide some structure.
STEP 1        Identify and highlight the important words in the question
STEP 2        Recall definitions of important words (if necessary)
• Discuss – To identify issues and provide points for and/or against.
• Concept - idea
• Atmosphere – Mixture of gases that surround the earth.
• Distribution or concentration of gases – “How spread out?”
STEP 3        Develop your own rubric that reflects the depth required
• Define atmosphere
• Describe / Draw structure of the atmosphere – indicate how the
concentration of gases varies
• (Suggest) where the atmosphere ends
STEP 4        Write your discussion
9.9.1.b      Identify that the Earth’s atmosphere is largely maintained in place by the
earth’s gravitational pull

GRAVITY and the ATMOSPHERE
Gravitation is the force of attraction that acts between objects because of their mass – that
is, the amount of matter they are made of. Because of gravity, objects that are on or near
the Earth are pulled towards it.

The Earth’s atmosphere is largely maintained in place by the earth’s gravitational pull.

9.9.1.c      Discuss why there is no such thing as ‘empty space’

EMPTY SPACE???

What do we know about space?

Below are a series of questions and information about space.
• Suggest answers to the questions and
• Consider the information provided.

1. What is space?
2. Where is space?
3. Once astronauts leave the atmosphere are they in empty space?
4. Do spacecraft ever have a collision with objects in space?
5. There are millions of pieces of ‘space junk’ (pieces of satellites) orbiting the earth
6. Most space junk orbits from 500-2000 kilometres above the earth’s surface.
7. The earth orbits the sun. Both are in space. What other large bodies are in space?
8. Are comets, which orbit the sun, in space?
9. What are meteors, meteorites and shooting stars?
10. You could see five shooting stars in an hour, on a clear night?
11. What is the solar wind?
12. Is the solar wind dangerous?
13. Is the moon in space?
14. The sun is a huge glowing ball of gases at the centre of the solar system. There is a
continuous flow of gases from the sun. These gases travel at about 500 kilometres per
second or 1½ - 3 million kilometres an hour. This flow of gases is called the solar
wind. The density of these particles is about 5 per cubic centimetre. These particles
are prevented from reaching the earth’s surface by the earth’s magnetic field.
15. How many stars are there in space?
16. How many stars are there in a galaxy?
17. How many galaxies are there?

18. In the 19th century people studying the night sky discovered that “dark patches” blocked
the light coming from certain regions of space. By the 1930’s astronomers were able to
identify these dark patches as huge clouds of interstellar dust and gas (called nebula).
They form because gravity causes the dust grains to clump together.
19. The source for these clouds is matter from dying “stars”. Atoms emitted by these stars
can cling onto the surface of the dust grains. The atoms can combine and recombine
to form dozens of simple and complex molecules. Today nearly 100 organic
substances have been identified (by radio astronomy) in the dust clouds.
20. Examples of molecules identified in interstellar gas clouds.
Inorganic     Hydrogen (H2),              Silicon monoxide (SiO),
Sulfur dioxide (SO2),       Ammonia (NH3)
Organic       Carbon monoxide (CO),       Formaldehyde (H2CO),
Ethyl alcohol (CH3CH2OH)
21. There is one dust particle in every one million cubic metres (that is a cube 100 metres x
100 metres x 100 metres). This matter in dust clouds makes up about 1% of
interstellar matter.
22. The other 99% of matter in interstellar space does not occur in gas clouds. This matter
is mostly free floating atoms (mostly hydrogen, but also oxygen, carbon and nitrogen).
They are so widely spread that they rarely meet. On average, hydrogen atoms in the
Milky Way Galaxy have a temperature of –2000C. There are about 300,000 hydrogen
atoms in a cubic metre. This seems like an enormous number of atoms. However, the
distance between interstellar atoms is roughly 100 million times larger than the size of
the atoms. If a similar distance separated two people, they would be about 100 million
kilometres apart.

HSC Style Question
Discuss why there is no such thing as ‘empty space’
This question requires an extended answer. Provide some structure for your answer.
STEP 1 Identify and highlight the important words in the question
STEP 2 Recall definitions of important words (if necessary)
• Discuss – To identify issues and provide points for and/or against.
• Why – provide reasons
• Space – Area of universe outside the atmosphere
STEP 3 Develop your own rubric that reflects the depth required
• Define space
• Issue 1 – Compare matter concentration in space and atmosphere.
• Issue 2 – Consider matter in near space
• Issue 3 – Consider matter in interstellar space
STEP 4 Write your discussion
9.9.1.i      Gather, process and present information from secondary sources to model
the relative distance of particles in a solid, liquid, gas and in space

RESEARCH

1. Complete the diagram below to represent the relative distance between particles in
space. Diagrams for a solid, liquid and a gas have been drawn.
The pictures (distances and particle size) are not drawn to scale. They do reflect relative
sizes and distances.

Space

2. How far apart are two particles in a solid?
3. How far apart are two particles in a liquid?
4. How far apart are two particles in a gas?
5. How far apart are two particles in space?
6. Describe how you could model the relative distances between particles of a solid, liquid
and a gas, and particles in space.

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