Content |
Description |
Drawing Minkowski diagrams |
This task guides
you through drawing a minkowski (space-time) diagram.
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Minkowski Problems |
This task (powerpoint
presentation) requires you to plot minkowski diagrams in order
to find the distance and velocity of some nearby objects. |
Parallax measurements |
There are
lots of units used to measure astronomical distances. Your
teacher will explain about measuring distances in light seconds,
light years, and parallax seconds. When you are happy you
understand try the questions on
this sheet.
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Standard Candles |
Look at
this powerpoint presentation which explains about some of
the methods we can use to measure the distance to distant
galaxies using "standard candles".
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Comparing the brightness of lamps |
Lamps of different brightness can appear the same
brightness if they are at different distances - rather like our
"standard candles". Answer
these questions to develop your understanding of how to
calculate the apparent brightness of lamps at different
distances. You should see how this is analogous to our
"standard candles", such as Cepheid variable stars and type 1a
supernovae.
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Brighter stars are not always nearer... |
This exercise looks at how the luminosity and brightness of
stars are related, by comparing the amount of light they emit
and their apparent brightness. |
Doppler shift - demonstrations |
Listen to the sound from this "whirly-tube".
What causes the apparent variation in pitch? Note that the
person swinging it hears a constant tone!
You may also want to watch this short video,
which shows the doppler shift of a car horn for a moving
vehicle:
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Doppler shift II - Applets |
These applets will help to clarify what is
happening to cause the change in the pitch.
This
yenka applet
shows the effect brilliantly, but note that you will need the
yenka plug-in installed (see DP).
Otherwise,
this applet ilustrates the principle reasonably well, or
this one by Walter Fendt. |
Redshift I - what is a spectral line? |
Light from distant galaxies undergoes a doppler
shift. To understand this properly, we will need to remind
ourselves about the absorption lines observed in the solar
spectrum.
This
powerpoint presentation has some useful images to help you
understand the significance of these spectral lines.
If you need a reminder of why the spectral
lines appear at these specific wavelengths, then this simulation
will help!
Teacher note: can be useful to demo the K and H lines for
calcium, using the CLEA software. |
Redshift - quantifying redshift |
Your teacher will explain how to
calculate the redshift "Z" of a wave, and how this quantity is
related to velocity. When you are happy you understand,
try
these questions (Q55S). |
Hubble
investigation software |
The CLEA "red shift" software allows you to
collect data for a wide range of galaxies, by measuring the
apparent magnitude, and the red shift of the K and H calcium
absorption lines. Record your results in
this spreadsheet.
The approximate distance to the galaxy can be
deduced from the apparent magnitude, and recession velocity can
be calculated from the red shift measurements. Your
teacher will explain how to do these calculations. When
you have collected the data, plot a graph of recession velocity
(km/sec)
against distance (Mpc) and find the
gradient.
Teacher note: you will need to install the software on your
computer (install file here -
hublab.exe). It should already be available on the
pupil's computers.Pupils use the spreadsheet provided.
There is a copy pre-filled with some basic data and with the
graph already plotted
here. Visit the CLEA homepage
here for more awesome software! |
Modelling a one dimensional expanding universe... |
Class activity - model
expansion of the universe using a long piece of elastic (approx
4-5m), with a number of galaxies placed along it (sticky labels
or post-it notes - 5 works well). Measure positions of
galaxies, then expand universe (student runs to other end of
room!). Measure time taken for expansion. Consider
distance each galaxy has receded from our galaxy (nominate any
one of your choice!). Find apparent velocity of each
galaxy. Find hubbles constant for elastic universe!
Repeat for an observer in any other galaxy.
Consider 1/Ho as approximation for age of universe.
There is a worksheet
here in word format. Should ideally be enlarged to A3
size. |
Redshift of Quasars |
Try
these questions (Q95S), which look at the red-shifts
observed for "Quasi Stellar Radio Sources" (usually abbreviated
to QSR or "quasar"), and the associated scale of the universe. |
Cosmic Microwave Background Radiation |
Cosmic
Microwave Background Radiation can be seen all around us, and is
in fact extremely red-shifted radiation
from the early stages of the formation of the universe.
There is a powerpoint with a few useful slides
here.
[Insert
link to "COBE" images, insert link to formation of atoms
"transparent universe", images on page 88 of text book useful].
Answer
these questions
(Q100S). |
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