Vocabulary: absolute brightness, absorption spectrum, apparent brightness, Big Bang theory,blueshift, Cepheid variable, Doppler shift, Hubble constant, Hubble’s law, luminosity,megaparsec, period, redshift, spectrographPrior Knowledge Questions (Do these BEFORE using the Gizmo.)Standing by the side of a lonely highway at night, you see two motorcycle headlights, one ineach direction. The headlig
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Vocabulary: absolute brightness, absorption spectrum, apparent brightness, Big Bang theory,
blueshift, Cepheid variable, Doppler shift, Hubble constant, Hubble’s law, luminosity,
megaparsec, period, redshift, spectrograph
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
Standing by the side of a lonely highway at night, you see two motorcycle headlights, one in
each direction. The headlight on your left appears brighter than the one on your right.
1. If the headlights are equally bright, which motorcycle is closer?
Explain: the headlight on the left is closer, because the closer a light source is to you, the
more light particles hit your eye and the less they have to travel and be dispersed.
2. Suppose the dim-looking headlight on the right is actually a small light on the front of a
bicycle. What can you conclude about the distance of the motorcycle and bicycle?
if i know that the light source is smaller, i can conclude that the bicycle is closer than it
appears.
Gizmo Warm-up
In 1912, an astronomer named Henrietta Swan Leavitt
studied a class of stars called Cepheid variables. These
stars change from bright to dim to bright again. Her
discoveries led to a method of measuring distances to
other galaxies and eventually helped to support the Big
Bang theory of the origin of the universe.
In the Big Bang Theory – Hubble’s Law Gizmo™, select Region A. Look at the image of the
Andromeda Galaxy, a galaxy relatively close to our own Milky Way galaxy.
1. Locate the two Cepheid variables, the stars that change in brightness over time. Star A-091
is the yellow star, and A-171 is the white star.
A. Which star reaches a greater apparent brightness?
star A-091 had a greater apparent brightness.
B. Which star takes longer to pulse?
star A-091 take longer to pulse than the other star.
2. Because both stars are in the same galaxy, they are about the same distance from Earth.
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