Student Exploration: Big Bang Theory – Hubble’s Law
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? Left
Explain: it is brighter because its closer.
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? Yellow star
B. Which star takes longer to pulse? Yellow star
2. Because both stars are in the same galaxy, they are about the same distance from Earth.
Based on what you see, how is the brightness of the star related to how quickly it pulses?
Based on the observation the more a star pulses the dimmer the star is… when a star moves
away from the earth, its light is shifted toward.
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? Left
Explain: it is brighter because its closer.
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? Yellow star
B. Which star takes longer to pulse? Yellow star
2. Because both stars are in the same galaxy, they are about the same distance from Earth.
Based on what you see, how is the brightness of the star related to how quickly it pulses?
Based on the observation the more a star pulses the dimmer the star is… when a star moves
away from the earth, its light is shifted toward.
