Transcript Cosmology

Really, just how important and
significant are you…………?
Cosmology
The study of the
contents, structure, and
evolution of the universe
from the beginning of
time……to the future.
Was Monty Python right?
“that’s orbiting at 19 miles a second”
Calculate if this is in any way an accurate
figure?
What data do you need to do this?
Earth – Sun distance = 9.29x107 Miles
Year = 365.25 days
Calculation
Orbit Radius = 9.29x107 miles
 Circumference= distance travelled= 2πR
= 2 x π x 9.29x107
= 583707915 miles
 Speed = Distance ÷ Time (Time =365.25 days)
 Speed = 1598105 miles/day
or 18.5 miles per second…Pretty close!!!
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Our Solar System
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Lets start closer to home….
watch the video “Our Solar Sytem” and
make notes.
Cosmology Projects/Presentations
The Earth, Moon and Sun
 The Moon
 The Solar System
 Stars & Constellations
Each group will also have to explain one
topic from Cosmology Mathematics.
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The Earth, Moon & Sun
Night & Day
 Seasons
 Solar Eclipses
 Solar Flares
 Aurora Borelalis
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The Moon
The Phases of the moon
 The Dark Side Moon
 Lunar Eclipse
 Tides
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Solar System Model
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Demonstration of the size and scale of our
solar system
Constellations
Identify the Great Bear, The Big Dipper,
The Plough
 Identify the North Star (Polaris)
 Orion and The Horse Head Nebula
 Taurus
 Plaeides
 Casseopia
 Star Maps
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Cosmology Mathematics
Astronomical units (AU)
 Parsecs (pc)
 Light years (ly)
 Ellipses
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Cosmology
1
Our Solar System
How it all started……
‘Heliocentric’ Solar System
‘Geocentric’
versus
Ptolemei &
Aristotle
Earth is the
centre of the
universe
Copernicus
(1609/1637) Present
idea of planets
rotating around the sun
Cosmology
Kepler’s Laws (1609)
Describe the motion of the planets around the sun.
Kepler I
The orbit of a planet around the sun
is an ellipse with the sun at one focus.
Kepler II
2 A line joining a planet and the sun
sweeps out equal areas in equal times.
clack for
K2b Movie
Click Picture for K2a Movie
Kepler III
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Describes a relationship between the
radius of the planets (average distance to
the sun) and the time taken for one
complete orbit.
T2 is proportional to R3
Click for K3
Movie
Cosmology
1
Our Solar System
Kepler’s Laws (1609)
Answer the following questions based on Kepler’s laws:
1 a) Compare planetary ellipses to circles. In what way are they different?
b) Use your worksheet ‘Structure and size of the universe’ to find out
which planet is furthest off the circle and which one is closest to a circle.
What about ‘Mars’- Kepler’s favourite…?
c) Draw an ellipse with its two focal points and the two radii.
Cosmology
1
Our Solar System
Kepler’s Laws (1609)
Answer the following questions based on Kepler’s laws:
2 a) Use Kepler’s second law of equal areas describe the planets speed
when its orbit is furthest from the sun and when its closest to the sun.
b) Does the force that keeps the planet on its path change? Explain.
3 How does the period of rotation of a planet change if the average
distance to the sun a) doubles or b) triples.
The Big Bang Theory
- Our Expanding Universe
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Cosmology is the search for
origins. It seems as if everyone
wants to know how the Universe
began.
The Big Bang theory is the result of
several important observations.
In 1927, Edwin Hubble first observed
that light from distant galaxies is red
shifted and that galaxies are moving
farther and farther away from us.
Second, he determined that the
farther away a galaxy is from us, the
faster it is receding from us.
Hubble’s Law
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What does this
graph tell us?
Note how there is a
clear proportionality
between distance
and recessional
velocity.
This proportionality
is known as the
Hubble Law.
The slope of this
line, with
dimensions of
velocity over
distance, is called
the Hubble
Constant (H).
Recessional Velocity
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The graph shows that the
recessional velocity (the
speed a galaxy is moving
away from us) is
proportional to the
distance from us.
i.e. stars further away
from us are moving away
from us faster than stars
closer to us!
What is the inference from Hubble’s
Law
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Almost all Galaxies are red shifted and are
thus moving away from us (The Milky Way)
The
most Distant
galaxies exhibit
the most red-shift,
thus the most
distant galaxies
are moving away
from us fastest.
The Hubble Constant
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Let us look more closely at the
slope of the Hubble Law Graph.
Slope = Velocity/Distance (Hubble
Constant)
The inverse of the Hubble
Constant then has the dimension
of time, and can be taken as an
estimate of the age of the
Universe!
The Hubble Constant has been
found to be between 50 and 100
km/s per kiloparsec.
The Universe has thus been
expanding for 8 to 15 billion
years
The Future of the Universe?
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Don’t Worry - if there is to be a Big
Crunch it won’t be for a very, very
long time!
The gravitational attraction will
eventually overcome the
expansion. The Universe will stop
expanding and then collapse to an
eventual big crunch This is called a
closed universe.
Alternatively the expansion slows
to zero ‘at infinity’. This is called a
flat universe.
If there is not enough mass for its
gravitation effect to overcome the
expansion, the Universe will
continue to expand forever. This is
called an open universe.
A closed universe might rebound
forever – a big bang eventually
resulting in a big crunch which
rebounds into a big bang and so
on. The whole Universe may be a
gigantic oscillator!