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OUTLINE
• First 25 minutes of the video
• Notes on waves, Doppler effect, and red/blue shift
• Mini lab on spectrums and how they are used to
understand red and blue shift
• Mini lab on the expanding universe
• Video
• Understanding the Big Bang and Atom formation
Electromagnetic Waves
• https://www.youtube.com/watch?v=oZZ4wKYtVl8 (short)• https://www.youtube.com/watch?v=nt-A1Cr6Aao (1:18, explained)• Transverse wave made up of electrical and magnetic energy• It is produced when the electric and magnetic fields switch back
and forth (vibrating) causing a disturbance that travels through space as a wave.
• This wave carries energy and information from one part of the universe to another, which is called electromagnetic radiation.
• Our instruments pick up these electromagnetic waves and change them into vibrating tunes/static
• They travel at the speed of light: 299,792.458 km/s in a vacuum
Electromagnetic Spectrum• “All electromagnetic waves travel at the same speed in a
vacuum, but they have different wavelengths and different frequencies” (Pasachoff 75).
• An electromagnetic spectrum “…is the complete range of electromagnetic waves placed in order of increasing frequency” (Pasachoff 75).
• Radio waves, Infrared rays, Visible light, ultraviolet rays, X-rays, and gamma rays.
Electromagnetic Spectrum
• Radio Waves
– Longest wavelength and lowest frequencies
– Broadcast waves and microwaves
• Infrared Rays
– Wavelengths shorter than radio waves
– The invisible heat you feel
Visible Light
• You can see these waves
• The longest wavelengths and lower frequencies (and lowest energies) appear in the red and the shortest wavelengths and higher frequencies (and higher energies)appear in the violet/blue.
• Violet Blue Green Yellow Orange Red
• Ultraviolet rays– Shorter wavelengths and higher frequencies
than visible light– They carry more energy than visible light– Pros: killing bacteria and providing vitamin D– Cons: to much exposure causes skin cancer, can
damage your eyes, and burn your skin
• X-Rays:– Shorter wavelengths and higher frequencies
than ultraviolet rays, thus can carry more energy
– Can go through most matter, except dense matter like bones
• Gamma Rays:– Have the shortest wavelength and highest
frequencies, thus has the greatest amount of energy
– Great penetrating ability– Pros: use to kill cancer cells inside the body, use
to help see inside the body– Cons: produced by nuclear reactions and can be
harmful (even deadly if exposed to too much).
“Sound Waves and Stars: The Doppler Effect”
blueblue
redred
Spectrographs• http://www.learner.org/teacherslab/science/light
/color/spectra/• Spectrum Tubes• Instrument to separate white light into the bands
of color
• This is a spectrum from our sun. The dark lines are where different elements have absorbed different frequencies of light. Each element has its own spectrum, kind of like a finger print. Scientists use spectrographs to determine what elements other stars are made of.
Spectrums A, B and C are from identical stars within our galaxy. Spectrum A represents a possible spectrum of a star not moving toward or away from Earth. Spectrums B and C show stars in motion with respect to an observer on Earth. Compare the three spectrums and answer the following questions:
HUBBLE’S DISCOVERY
• “Just as the light from a single star can be used to make a stellar spectrum, scientists can also use the light given off by an entire galaxy to create the spectrum for that galaxy” (Holt 793).
• In the 1920s, Hubble found that the spectra of galaxies, except a few near our own, were all shifted towards the red end of the spectrum.
• By measuring the redshift he was able to determine the speed at which the galaxies were moving away from us.
• Galaxies farthest away show the greatest redshift and therefore the greatest speed.
• This evidence pointed to the fact that our universe was expanding.
• Most galaxies are red-shifted (moving away from us) today. Let’s rewind the clock of time. Using the information and data from what you have learned, what can be inferred about the origin of the universe?
Balloon Lab
• Question:
– How is the universe expanding?
• Vocabulary words
– Independent variable: a factor that is changed on purpose; also called manipulated variable
– Dependent variable: a factor that is observed or measured in response to a change in the independent variable; also called responding variable
BIG BANG THEORY• The Big Bang Theory claims that the
universe has expanded from a very dense,
very hot state that existed at some time in
the past.
Evidence to support• Studies of red-shifts of distant galaxies show that
the universe is expanding.
• Cosmic Background radiation (left over
energy/heat)
• Abundance of Hydrogen and Helium
Big Bang Model• Running the expansion backward allows us to calculate
the temperature and density of the universe during its
earliest moments.
• The known laws of physics can be used to determine
the behavior of matter and energy at these temperatures
and densities.
• The model is then used to make predictions that can be
compared to observations.– The only elements in the early universe were hydrogen and helium (and a
tiny amount of lithium). The hydrogen-helium mass ratio was about 75-
25%.
– Microwaves with an energy corresponding to a temperature of about 3 K
will be found everywhere in space. From Earth they will be “seen” across
the entire sky.
TEMPERATURE
Time Temperature
One million of a second 1013 K (ten trillion Kelvin) ≡ a lot of energy
Or 179,999,999,999,540.31° F
10-thousand of a second 1012 K (one trillion Kelvin)
Or 17,999,999,999,540.33° F
10th of a second Cooling
A second Cooling
100 seconds 109 K or 1, 799,999,540.33 ° F
10 minutes cooling
380,000 years 3,000 K or 4,940.33 ° F
Now 3 degree above absolute zero or 3 K
or -454.27° F
Summary:
• It was extremely hot and then started to cool slowly until it is
now extremely cold.
• Temperature played a crucial role in the formation of matter.
Where did matter in the
universe come from?
E = mc2Mass is just “condensed”
energy
Energy →mass
A particle – antiparticle pair can be
created if the available energy equals
the mass of both particles times the
speed of light squared
A very BIG number!
Albert
Einstein
ABOUT A MILLIONTH OF A SECOND…
• 1013 K (ten trillion Kelvin) or
179,999,999,999,540.31 ° F
• Protons, anti-protons, neutrons and anti-neutrons
begin to form because of cooler temperatures
• As a proton or neutron collides with its anti-particle
they annihilate and are converted to energy in the
form of photons– Photons are light particles
protonanti-proton
anti-neutron
neutron
About one ten-thousandth of a second . . .
• Almost all particles and anti-
particles annihilate and produce
gamma ray photons.
• It is no longer hot enough to produce protons and anti-
protons (or neutrons and anti-neutrons) spontaneously from
pure energy to replace those that annihilate each other.
proton anti-proton
• Photons are constantly scattered by free particles with an
electric charge like electrons or protons
• These photons increase in wavelength as the universe
expands and will eventually become the majority of photons
that make up the cosmic background radiation
ONE TEN-THOUSANDTH OF A SECOND . . . CONTINUED
• maintains equal numbers of protons and neutrons . . .
p+ + e− ↔ n + e n + e+ ↔ p+ +e
• High energy collisions between protons, neutrons
and other particles like electrons can transform one
particle into another.
• a billion photons for every proton or neutron
About a tenth of a second . . .
• As the temperature (and available energy) drops,
transformation to protons is favored over neutrons
About one second…
• Transformation reactions can no longer occur.
Neutrons begin to decay into protons
n → p+ + e− + e
ABOUT 100 SECONDS …• Neutron decay results in a 1:7 ratio of neutrons to
protons.
• Universe is now cool enough for protons and
neutrons to bind together. This is called fusion.
This process creates new, heavier atomic nuclei and
is called nucleosynthesis.
proton
(hydrogen
nucleus)
neutron
deuterium
tritium helium
AT THE BEGINNING OF NUCLEOSYNTHESIS . . .
14 protons 2 neutrons
12 hydrogen nuclei
Atomic mass = 12
At the end of nucleosynthesis . . .
1 helium nucleus
Atomic mass = 4
Mass ratio 75% 25%
• Very little happened in nucleosynthesis for a
long time as temperature and density are too
low for fusion.
About 10 minutes . . .the end of big bang nucleosynthesis
• Temperature drops to 3000 K
• Universe is cool enough for electrons to bind with nuclei and
form stable atoms
• With most electrons now bound in atoms, photons can travel
large distances without being scattered by free electrons.
• Photons now travel in all directions, resulting in what is
called the cosmic background radiation.
ABOUT 380,000 YEARS …
HHe