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Reviewing the Beginning13.7 billion years ago
Extremely hot
Expanding “soup of particles”
Inflation: early phase rapid expansion
Cooling with steady, constant expansion
Nuclear Weak Force
Nuclear Strong Force
Cosmic Background Microwave Radiation
Baryons: Protons & Neutrons (made up of quarks)
Big Bang Fusion of nuclei Hydrogen (makes up 90% of the Universe today) Helium Lithium Beryllium
No electrons attached to these nuclei, they are too hot
Predominance of the lightest element = Evidence of the Big Bang
The Nuclear Weak ForceWhy don’t negatively charged electrons
fall into positively charged protons? THE NUCLEAR WEAK FORCE!! Neutron --> Proton + Electron!
The Weak Force is responsible for Initiating hydrogen fusion in stars the radioactive decay of subatomic
particleso Large nuclei are unstable
o β-decay: Neutrons fall apart to form a proton and an electron, the electron escaping into the orbital of the atom
Nuclear Strong ForceProtons are all positive and would love to repel
each other
The nuclear strong force holds the nucleus together You must have energy to exert a force. Nuclear energy powers the strong force.
Affects very small space
HUGE amount of energy – released in fission…bombs
Nuclear Strong Force: Squeezing a Nerf Ball
The nuclear strong force is like an invisible hand that holds the nucleus (Nerf ball) together.
Without it, there could only be Hydrogen in the Universe
FusionProton-Proton Chain
2 Hydrogen fuse to form Helium Helium fuse to form Carbon Carbon fuses with Hydrogen to form Nitrogen Nitrogen fuses with Hydrogen to form Oxygen…..
Requirements of FusionHeat-Heat-Heat
Gravity pulls the atoms together
Gravitational pressure heats the gases to millions of degrees
Mass - Stars: the bigger they are the hotter they are More Mass = More heat =
more fusion = more elements
H - He - C - O - Ne - Mg - Si - Fe
IronFusion in stars can form nuclei that have up to 26
protons = IRON Too much energy is required to overcome the
electromagnetic repulsion
• Creating elements heavier that iron requires more energy
Fusion also Creates Isotopes
Neutrons are captured by other atoms to form Isotopes
Isotopes are forms of standard elements with extra neutrons
The Heavier ElementsSupernova of extremely massive stars
Cores of these stars are saturated with iron Extreme pressure and temperature
Gamma radiation breaks the iron nuclei releasing more energy
Shock-wave produces enough energy to fuse elements heavier than iron up to and including Uranium
Light PropertiesThe Speed of Light = c
3 x 108 m/s190,000 miles/second
Light could travel around the world about 8 times in one second
EM SpectrumSpectrum means “a range”
EM spectrum ranges from long wavelengths to short
Shorter wavelength = higher energy Highest energy waves are bad for our
bodies
EM WavesHave properties of waves…Crests & troughsReflect & refract (bend)
…and particlesCan travel through empty
space
Wavelength and Frequency
λ = Wavelength, the distance between 2 peaks (or troughs)
f =Frequency, the number of waves per second
Velocity of a wave, v = λf EM waves all travel at 3 x 108 m/s A longer wavelength means a lower
frequency A shorter wavelength means a
higher frequencywww.nasa.gov
The Speed of Light
c=
c = speed of light
= frequency
= wavelength of light
Hertz (Hz) = unit of frequency Hz = 1/ second
Wavelength is measured in units of length, meters to nanometers
Energy
As frequency decreases, energy increases
E = h h = 6.626 x 10-34 Joules *second
Energy Unit J = Joule = Watts/m2
Higher energy = higher frequency= shorter wavelength
Frequency
Energy
Light as a ParticleLight = photons
Photons are considered to be both particle and a wave
What does that mean?A photon is a “wave packet”A photon is a “light particle”
Electromagnetic Radiation and YouLight is sometimes called E-M radiation
All things emit E-M radiation
You emit radia-tion• RADIO • MI-
CROWAVES• Infrared
(heat)
The Visible Spectrum
violet 380-420 nm
indigo 420-450 nm
blue 450-495 nm
green 495-570 nm
yellow 570-590 nm
orange 590-620 nm
red 620-750 nm
Visible LightNot all animals see the same wavelengths as
humans
Some see shorter wavelengths (ultraviolet) Hummingbirds Bees Mantis Shrimp
Others see longer wavelengths (infrared) Bats Snakes …and Mantis Shrimp… they do have the best eyes
on Earth, unfortunately they have very small brains and probably do not appreciate what they are seeing…
How do we know what a star is made of??
By looking at its EM spectrum
The star’s “fingerprint”
Hydrogen
How light or electromagnetic radiation is used in Astronomy
• Astronomers use spectroscopes separate starlight into its colors Identify star’s composition, temperature,
luminosity
• Different wavelengths provide different information Temperature – Blackbody Radiation Composition – Absorption Spectrum Luminosity/Brightness
Models of a Hydrogen AtomPhET's Model of a Hydrogen Atom
Composition of stars