Download Demo: An Expanding universe

Demo: An Expanding Universe:
Background: In fact, the universe is getting even bigger than it already is! Astronomers
believe that the universe is expanding - that distant galaxies in the universe are getting
farther apart all the time. It's not that stars and galaxies are getting bigger; rather, the
space between all objects is expanding with time. You can make a model of the universe to
show how this expansion works. Scientists often use models to help them understand what is
happening on a larger scale.
Directions:
1) Take a balloon and a marker; these will be the tools to make the universe.
2) Mark the balloon in a manner similar to the image below by making 4 dots. Don't put all
the dots in a straight line; spread them out a little. Each of these dots represents a galaxy.
Example:
3) Now blow your balloon half way so that the dots are easier to label and measure.
DO NOT TIE the balloon. Make a mental note about what happens as you blow up the balloon.
Label one dot “MW” for the Milky Way and label the others 1, 2 & 3.
2
3
1
MW
4) Use a ruler to measure the distances in centimeters between the center of the Milky Way
and the center of the Galaxies labeled 1, 2 & 3. Record this in the data table on your Lab
Report Sheet, round to the nearest tenth of a centimeter.
5) Now connect the MW dot with the furthest galaxy with a wave that has a short
wavelength. Make a mental note about the size of this wavelength. This balloon simulates
our early universe, so this wave represents light energy emitted by this galaxy as seen from
earth in the Milky Way Galaxy.
6) Inflate the balloon completely without letting it pop. Then tie the end. Measure again the
distance between the Milky Way and the other three galaxies, using the center of each dot.
Record this in the data table on your Lab Report Sheet.
Station #1: An Expanding Universe Conclusion
After Thought: Your balloon model behaves similarly to the real universe. But like any
model, it has its limitations. For one thing, the surface of the balloon (where you drew the
dots) is two-dimensional, while the universe is three-dimensional. A three-dimensional model
of the universe might be raisin bread dough rising in an oven. As the dough rises, each of the
raisins gets farther away from all the other raisins. (See figure below) But the raisin bread
dough model has its limitations too - you couldn't have measured the distances between the
chips as easily as you could have with the balloon model.
Conclusion Questions
a. What happened to the distance between the Milky Way and the other Galaxies?
Did it increase or decrease?
b. What happened to the wavelength of your light wave as the balloon grows? Did it
get longer or shorter?
e. What has a longer wavelength: red light or blue light.
Activity #2: Doppler Effect Computer Program:
Background: When an object is moving relative to an observer it distorts the way the
observer perceives the object’s electromagnetic radiation. Whoa! What does that mean?
Think about when an ambulance drives by, going very fast. The pitch of the siren changes as
the ambulance approaches you and passes you. This is because the sound waves’ frequency is
increased as it approaches you and then decreased as it drives away. Visualize this concept
using the diagrams and the interactive animation at this station.
Directions:
1) Go to NOVA | Stellar Velocity: The Doppler Effect using the following URL:
http://www.pbslearningmedia.org/resource/phy03.sci.phys.energy.doppler/stellar-velocity-thedoppler-effect/
2) Launch the Interactive. Record Notes as you go from one screen to the next.
3) Answer the Conclusion Questions on your Lab Report Sheet using your observations and the
diagrams.
Conclusion Questions:
1. Describe the Doppler effect. What causes it?
2. What is a redshift?
3. How can the degree of redshift in the color spectra of a supernova tell astronomers about the
movement and location of stars?
Activity #2 Diagrams: Doppler Effect
Activity #3: Using a Spectroscope
Did you know?
The color light that our eye interprets is
actually a combination of many colors of
the visible spectrum. For example, white
light is actually a combination of all the
colors of the electromagnetic spectrum.
We can separate these colors with the
use of a prism, just like on the cover of
the Pink Floyd “Dark Side of the Moon”
album. Use a spectroscope and look at
the light to see for yourself.
Background: Astronomers use this same principle to look at the light from stars. Each star
has a unique spectrum of color that combines to form the visible light that we see with the
naked eye. This spectrum is dependent on the elements in the star and the temperature of
the star. In order to see the spectrum of colors of any light scientists must use an
instrument called a Spectroscope. During this activity you will get to use a real spectroscope
to look at different light sources.
Directions:
1) Look through the spectroscope at a plain white 60 Watt bulb. Aim the vertical slit directly
at the light. Since this is a white light, to the right of the slit you should see bands of color
underneath the numbers that look like this:
4
5
6
7
2) Now look at a colored glow stick. Again aim the vertical slit
directly at the light. Notice that this light is not made of a continuous spectrum of color
like the white Light Source A.
3) Using color pencils, draw the spectrum of light on the diagram on your Lab Report
Sheet.
Activity #3: Using a Spectroscope Conclusion
After Thought: Due to the Doppler Effect, depending on how a light source is moving
relative to us, we perceive the electromagnetic waves differently. In other words the
electromagnetic spectrum of color that we observe with our spectroscope will shift if the
light source is moving toward us or away from us. Use your knowledge of this principle and
your ESRT to answer the following questions.
Conclusion Questions:
a. An astronomer can estimate the temperature of a star by observing its
1) size
2) shape
3) color
4) brightness
b. The diagram below shows the spectral lines for an element.
Which diagram best represents the spectral lines of this element when its light is
observed coming from a star that is moving away from Earth?
1)
2)
3)
4)
Activity #4 Cosmic Background Radiation & History Connect:
Directions:
1) Listen to what scientists believe the “Big Bang” might of sounded like.
2) Read the 1965 News Article “Murmur of a Bang”
Conclusion Questions:
a. What do scientists propose the Big Bang really sounded like?
b. In what form do we detect this energy from the Big Bang today?
c. What happens to the sound waves as the Universe expands?
d. What type of radiation was discovered coming from all regions of space?
e. What is the importance of this discovery? What does it provide supporting evidence for?
f. What are the names of the two scientists who discovered this radiation and what were
they actually trying to find when they discovered the radiation?
Answer Sheet
DEMO:
Distance between the Dots
MW and 1
Small Balloon
Larger Balloon
MW and 2
MW and 3
Station #1: An Expanding Universe Conclusion
1. What happened to the distance between the Milky Way and the other Galaxies?
Did it increase or decrease?
2. What happened to the wavelength of your light wave as the balloon grows? Did it get longer or
shorter?
3. What has a longer wavelength: red light or blue light?
Activity #2: Doppler Effect Computer Program:
1. Describe the Doppler effect. What causes it?
2. What is a redshift?
3. How can the degree of redshift in the color spectra of a supernova tell astronomers about the
movement and location of stars?
Activity #3: Using a Spectroscope
Conclusion Questions
a. An astronomer can estimate the temperature of a star by observing its
1) size ____
2) shape
3) color
4) brightness
b. The diagram below shows the spectral lines for an element.
Which diagram best represents the spectral lines of this element when its light is observed coming from a
star that is moving away from Earth?
1)
2)
3)
4)
Conclusion Questions:
a. What do scientists propose the Big Bang really sounded like?
b. In what form do we detect this energy from the Big Bang today?
c. What happens to the sound waves as the Universe expands?
d. What type of radiation was discovered coming from all regions of space?
e. What is the importance of this discovery? What does it provide supporting evidence for?
f. What are the names of the two scientists who discovered this radiation and what were they
actually trying to find when they discovered the radiation?