The Earth in Space - Notes
10.1 Objectives
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Describe what is in the Universe.
Describe what is in a galaxy.
Galaxies
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Voyager 1 and Voyager 2 were launched from Earth in 1977.
In 1979, Voyager 1 passed Jupiter.
Both probes passed through the Kuiper belt (rocks and dust beyond Neptune) and
beyond the edge of the Solar System.
Voyager 1 is about 23 billion kilometers away from Earth – the furthest any
human-made object has travelled.
Both Voyagers will spend over 10,000 years travelling through the Oort cloud
(objects weakly held by the distant Sun’s gravity).
After exiting the Oort cloud, they will still be inside the Milky Way galaxy.
What is a galaxy?
A galaxy consists of:
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Thousands of millions of stars.
Planetary systems (most stars are believed to have planetary systems).
Stellar dust and gas (from stars that exploded or left over from the formation of the
Universe).
⚠ Fact: Our galaxy is just one of thousands of millions of galaxies in the Universe.
Our Galaxy - The Milky Way
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"Galaxy" comes from the Greek word for "milky."
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The Milky Way is the hazy white band across the sky, visible from dark places.
The nearest star to the Sun is Proxima Centauri:
o Its diameter is seven times smaller than the Sun.
o Has at least one exoplanet, making it our nearest solar system.
Our Solar System and Proxima Centauri’s system are part of the Milky Way
galaxy.
Most of the stars visible to the naked eye are in the Milky Way.
The Sun and all stars in our galaxy orbit a huge black hole at the center.
The Milky Way is a spiral galaxy:
o Curved arms form a disc shape with a bulge in the middle.
The images we have of the Milky Way are models, not real photographs, made using
telescope observations.
The hazy white band we see is a concentration of stars along the disc.
Fewer stars are visible when looking away from the disc.
Other Galaxies
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Not everything bright in the night sky is part of the Milky Way.
Some bright, fuzzy objects are other galaxies outside the Milky Way.
Andromeda Galaxy:
o The nearest spiral galaxy to us.
The Large and Small Magellanic Clouds are two of our neighbouring galaxies.
Not all galaxies are spiral.
Without a telescope, galaxies appear as fuzzy discs.
The Universe
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The Universe is everything that exists:
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o Stars, planets, moons, comets, asteroids, meteors, and all matter, including
humans.
Some people ask what is outside the Universe, but science currently cannot answer
this – there may be no "outside."
The observable Universe extends 13.7 billion light years in every direction.
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Key points
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The Solar System is surrounded by gas and dust in the Kuiper belt and Oort cloud.
A galaxy includes stars, planetary systems, stellar dust, and gas.
A galaxy contains thousands of millions of stars.
There are thousands of millions of galaxies in the Universe.
We are located on a planet in a solar system on a spiral arm of the Milky Way
galaxy.
Asteroids
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In 2017, an object from interstellar space was detected in our Solar System. Initially,
astronomers thought it was a comet, but it was later classified as an asteroid. This
object was named 'Oumuamua.
What is an Asteroid?
o An asteroid is a piece of rock that orbits the Sun.
o Smaller than a planet, but some are large enough to be called minor planets.
o Asteroids range in size from less than 10 meters to over 500 kilometers in
diameter.
o Most asteroids are irregularly shaped, but some are nearly spherical.
o The total mass of all the asteroids in the Solar System is less than the mass of the
Moon.
o More than 100 asteroids also have moons.
o The term "asteroid" comes from the Greek word meaning "star-like," as they
appeared star-like through early telescopes, even though they are not stars.
How Do Asteroids Form?
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Asteroids are leftover debris from the formation of the Solar System.
o About 4.6 billion years ago, gravity pulled dust and gas together to form the
Solar System, and the remaining pieces of rock are what we call asteroids.
o Jupiter's gravity may have broken up some smaller planets into pieces of rock
that became asteroids.
It is believed that most stars have planetary systems, like the Sun, and these systems
probably have asteroids for the same reason as our Solar System.
Where Are the Asteroids?
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Over a million asteroids exist in the Solar System.
o Most of these asteroids are located in the asteroid belt between Mars and
Jupiter.
o Some asteroids are in the same orbit as larger planets, such as Jupiter.
o Some asteroids have orbits that bring them close to Earth, and astronomers
closely monitor these to provide warnings if one might hit Earth.
Collisions between asteroids can break off pieces of rock that can become meteors
when they enter the Earth’s atmosphere.
Asteroid, Meteor, Comet: What's the Difference?
It can be confusing to remember the differences between objects seen in the sky. Here's a
breakdown:
Object
Definition
Asteroid
A large piece of rock orbiting the Sun
Meteoroi
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Meteor
A smaller piece of rock that has broken off
from an asteroid or comet
A meteoroid that enters Earth's atmosphere
Meteorite A meteor that reaches the ground without
burning up in the atmosphere
Comet
An object made of ice and dust that develops
a tail when it gets close to the Sun
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Approximate Size
Smaller than a planet, larger
than a meteoroid
1 meter in diameter or
smaller
1 meter in diameter or
smaller
Varies in size
About 10 km in diameter
Meteorites are fragments of meteoroids that mostly vaporize in the atmosphere but
land on the Earth’s surface.
Meteorites
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Meteorites are sometimes found on the ground. These are fragments of meteoroids that
have mostly vaporized in the atmosphere but still reach the Earth's surface.
PHYSICS-14 chapter
Planning the Investigation:
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Decision: Investigate length of wire.
o Measure the current for different wire lengths.
o Calculate resistance using current and voltage.
o Keep other variables (thickness, material, voltage) constant.
Preliminary Work:
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Goal: Decide on wire type, thickness, and voltage.
o Preliminary findings:
▪ High voltage causes wires to overheat.
▪ Chose 1.5 V to prevent overheating.
▪ Use secondary sources to find suitable wire.
Choosing Equipment:
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Instruments:
o Digital ammeter: Measures current to nearest 0.1 A.
o Ruler: Measures wire length to nearest 1.0 mm.
Setup: Use clips to change wire length and connect different positions.
Assessing Hazards and Controlling Risk:
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Hazard: Wire can heat up.
Safety Measures:
o Place wire on heatproof mat.
o Avoid leaving the battery connected for too long.
Obtaining and Considering Evidence:
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Data Collection:
o Measure current for different wire lengths.
o Repeat each test three times for reliability.
o Discard anomalous results before calculating averages.
Analysis:
o Plot results on a graph to find patterns.
Material of
Wire
Copper
Iron
Aluminum
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1
1
Length
(m)
Voltage
(V)
1.5
1.5
1.5
Current
(A)
0.2
0.15
0.18
Resistance
(Ω)
7.5
10
8.33
Key Points:
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Planning an investigation involves:
o Identifying variables
o Doing preliminary work
o Choosing equipment
o Assessing hazards and controlling risks
Extension 14.5: Energy and Power
Objectives:
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Describe the difference between energy and power.
Calculate power.
What is Power?
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Power is the rate at which energy is transferred or converted.
A bright lamp transfers more energy per second than a dim lamp.
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The lighthouse lamp is much brighter than the lamps used in torches, houses, or
offices.
Power is measured in watts (W) or kilowatts (kW).
o 1 kW = 1000 W.
How to Calculate Power?
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The formula for calculating power is:
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Power(W)= Energy transferred (J)
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Torch Lamp Example:
o Energy transferred: 120 J per minute.
o Power:
Time taken (s)
Lighthouse Lamp Example:
o Energy transferred: 24,000 J per minute.
o Power:
o The lighthouse lamp is 200 times more powerful than the torch lamp.
How Do Light Bulbs Differ?
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Filament (Incandescent) Bulbs:
o Contain a thin piece of wire that glows when it gets hot.
Compact Fluorescent Lamps (CFLs):
o Energy-saving lamps first introduced in 1981.
Light Emitting Diodes (LEDs):
o Highly efficient and produce a lot of light for their size.
o Can be made small enough for various applications, including sewing into
clothes or cancer treatments.
o Used in major events like the London and Rio de Janeiro Olympics for light
displays.
Comparison of Light Bulb Power (Energy per second)
Light Intensity
(lumens)
800
1800
2800
Incandescent
Lamp (W)
60
100
150
15
25
45
CFL (Energy-Saving)
Lamp (W)
LED Lamp
(W)
10
18
26
How Do You Pay for Electricity?
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When paying electricity bills, consumers pay for the fuel burned to produce energy
and transfer it via electrical current.
The amount of energy transferred depends on the power of appliances and how
long they are used.
Energy (J) formula:
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Energy is commonly measured in kilowatt-hours (kWh):
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Key Points: