Geosciences
Safwan
Lec3_Universe.pptxElectromagnetic radiation (EMR)
Doppler Effect / EMR spectral shifts
Early observations of redshift in galaxies
The Hubble Plot
The Big Bang Theory
Origin of the Universe - the pieces of the puzzle
Please make sure to grab a handout for participation credit today.
Frequency – How many wave crests pass a given point per second.
Wavelength – Distance between two wave crests.
EMR: Energy that travels as waves (oscillating electric and magnetic fields). Can travel through a vacuum. Travels at the speed of light (roughly 300 million m/s).
Scientists think a lot about scale…
Longer wavelength
Shorter wavelength
Wavelength corresponds to energy: Shorter wavelength = higher energy (HOTTER).
Ex: UV light does damage to your body while radio waves do not.
1 nm = one billionth of a meter
The Doppler Effect
The Doppler Effect: Change in wavelength as an object moves relative to a STATIONARY observer.
Example: A siren or car horn sounds higher pitched as it approaches an observer and sounds lower pitched as it moves away from the observer.
THIS HAPPENS WITH LIGHT AS WELL
1 nm = one billionth of a meter
Blue shifted
Red shifted
Handout Page 1
In 1912 at Lowell Observatory in Flagstaff, Arizona, Vesto Slipher was the first to measure the redshift of spiral nebula (now known as a galaxies).
If the light emitted from the object has a different spectrum of light when it reaches Earth than it had when it first left the object = shifted.
Red shifted = toward red end of spectrum
http://spiff.rit.edu/classes/phys301/lectures/spec_lines/spec_lines.html
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Slipher noticed that galaxies were red shifted. In other words, their light spectra were shifted toward the red end of the spectrum.
What question do you think he asked?
To clarify, red shift DOESN’T MEAN THEY LOOK RED!
The color of a star/galaxy doesn’t matter when looking at red or blue shift.
Look at spectra --> what other info do you see? Any questions come to mind?
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Vesto Slipher noted not only were they moving away from Earth but they were moving away at tremendous speeds! Pretty amazing for 1912!
Remember, red shift DOESN’T MEAN THEY LOOK RED!
The color of a star/galaxy doesn’t matter when looking at red or blue shift.
Handout page 2 (#6-12) – read the instructions carefully. Everything you need to know to answer the questions is in the very first paragraph! DON’T OVERTHINK IT!
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Vesto Slipher noted not only were they moving away from Earth but they were moving away at tremendous speeds! Pretty amazing for 1912!
In 1929, Edwin Hubble and Milton Humason put their observations together in a way that led to the first realization that the universe is changing over time –
OBSERVE the plot at right – what do you see?
Putting Data to Work
A scientist sees …
Relationship?
Slope?
Axes?
Pattern?
Recessional velocity recede = move away from
So…what does this graph mean?
X-Axis:
Mpc = megaparsec
30 billion billion km
or
3 x 1019 km
Y-Axis:
km/s
For reference, the earth spins at 0.5 km/sec, which is 1,040 miles per hour.
Handout pp 3-4 – Expansion of the Universe
The Hubble Plot!
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The Big Bang Theory – came from the observations and data generated by Slipher, Hubble, Humason and others that indicated galaxies are moving away from us
Episode of rapid expansion (Big Bang) from a much more compact form, somewhere between 11 billion and 20 billion years ago (current best estimate is about 14 billion years ago)
Big Bang created simple elements (hydrogen, helium) from subatomic particles
Vast majority of Universe is Hydrogen (about 75%) and Helium (a little less than 25%)
Universe is still expanding
Turn in handout – name clearly on front page if you want credit for participation!
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