Before the bell rings, in your notes, write out
the important aspects of a correctly designed
experiment. Make sure to include a description
of your variable and control.
To understand the Big Bang…
• We must first start understanding waves and
the Doppler Effect!
Lets First Experience the Doppler
Effect!
What causes this sound effect?
The Doppler Effect
-Here we have a sound wave emitted
from an object (car, siren, screaming 9th
grader, etc.)
-Each red dot represents an air molecule
Now lets consider the waves represented
as circles…The waves are distributed
evenly spaced in each direction (That
means the same frequency!)
What happens if we move the sound
source?
• Towards us at 50m/s…
Moving towards us faster (100m/s)
And faster yet! (300m/s)
What is happening to the length between
waves that are approaching us?
• Movement toward an object causes decrease
in distance between the waves, which causes
an increase in frequency.
• Higher Frequency = Higher Pitch (Shreekier!)
What Happens if the source is moving
away from us?
-Movement away from an object causes increase in
distance between the waves, which causes a decrease in
frequency.
-Lower Frequency = Lower Pitch
Lets sum this sound thing up!
• With stationary
sources, you can hear
the same pitch in
each direction
• If sound source is
moving toward you,
there is a higher
frequency.
• If sound source is
moving away, there is
a lower frequency.
How does this relate to the Big Bang?
Electromagnetic Spectrum and visible light
Spectrum
Named by Isaac Newton
Types of spectra
How Spectra are formed
Spectra of elements
• Each spectrum is unique, like a fingerprint
• Spectral Periodic Table
• Astronomers used spectroscopes to figure out
what elements are in stars
Spectra for some elements in the
atmospheres of stars
What elements are in this star?
Answer
• The elements in the unknown star are:
Hydrogen and Magnesium
Now how can we relate the Doppler Effect to
light, and ultimately the Big Bang?
Lets look and see if we can figure out the
following gases with our spectroscopes?
Helium
Hydrogen
Mercury
Neon
Doppler Effect on Light
Stars and Galaxies
The “Red Shift”
What does it mean?
• Stars are moving away from us
• Universe is expanding
What would cause the universe to be
continuously expanding?