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Understanding the PHYSICS of the Cosmic Times Inquiring into the Nature of the Universe. Adapted from Dr. James Lochner USRA & NASA/GSFC Sandra Sweeney, Joseph Petsko Perkiomen Valley School District, PA. Cosmic Times 1919. Newton. Einstein. Science is about Questions and Tools. - PowerPoint PPT Presentation
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Adapted from Dr. James LochnerUSRA & NASA/GSFC
Sandra Sweeney, Joseph PetskoPerkiomen Valley School District, PA
Newton Einstein
Our understanding of the nature of the Universe has changed as our questions
and technology have changed.
What are some questions we might ask?
What are the tools we might use?
1. Give a description of the theory of gravity.http://en.wikipedia.org/wiki/Gravitation
1. How does it explain the motions of the planets?
2. What prediction does it make for the bending of light, and the upcoming eclipse in 1919?
Information Exchange(1918)
Einstein discovered that gravity is curved space-time. His theory predicted that
light would bend when passing near a massive object.
Einstein discovered that gravity is curved space-time. His theory predicted that
light would bend when passing near a massive object.
1919 Solar Eclipse verified Einstein’s prediction.
Mass of the objects Distance between them
Inertia: the resistance to change in motion and direction of motion in an object The more mass something has, the more it
resists a change in its motion – the more inertia it has!!!
solar eclipse in Varanasia vid
Sleep and smart phones
“Tomorrow the outlook may change and new methods may dwarf our knowledge and beliefs of today, or convert them into remote history. Soon we may look far beyond the last frontier, now 140,000,000 light years away. We, or our successors, may actually know familiarly the farthest borders of this vast Universe and learn facts about it so astounding that astronomers of today would be nearly unable to comprehend their significance.” -1927
1. What did Hubble say to become famous?
2. What was his evidence?
3. Create an analogy for comparing Cepheid variable stars to a real-world scenario.
Shapley thought they were part of Milky Way because he couldn't determine their true distance.
Hubble settled the question – when he determined the distance to Andromeda Galaxy.
1. Use Cepheid variable stars
Henrietta Leavitt first used
How to use:1. c.v.s. flash rate tells their
absolute magnitude (aka true brightness)
2. Comparing absolute magnitude and apparent magnitude (brightness to observer) tells distance
2. Use 100” Hooker telescope at Mt Wilson, CA Better telescopes
allowed astronomers to see further and with more clarity
Hubble determined distance to Andromeda Galaxy to be 900,000 LY (light years)– outside the Milky Way!!
A light year is the DISTANCE light travels in a year.
It is equivalent to 6 trillion miles (6,000,000,000,000)
Distances to galaxies determined using Cepheid variable stars
Andromeda galaxy outside the Milky Way We are in only one of MANY galaxies
Is the motion of galaxies static? Is the motion of galaxies random? Are the galaxies getting closer or further
apart?
What data do we need to answer this question?
The Universe is expanding!
Car horn passing by Doppler effect video Doppler effect animation Racecars Starlight and space ship interactive
Observations showed most “nebulae” appeared red. Red shift: Stars/galaxies moving away from
us show light that is shifted to the red end of the visible spectrum
Some galaxies appeared blue. What does that mean? Blue shift: Stars moving towards us show
light shifted to the blue end.
Understanding Doppler Effect helps in understanding redshift of light.
Demo: Hubble rubber band
Apparent shift of wavelengths as objects approach or move away
Wavelengths bunch up and get shorter as a wave approaches (higher frequency) Higher pitch or
blueshift
Wavelengths spread out and get longer as wave recedes (lower frequency) Lower pitch or redshift
Click here to hear and see – Minute Physics vid
Use images of Cepheid stars and galaxies to determine their distances
Put this together with their redshift data
Size of galaxy
100,000 light years
What does the graph tell us?
Velo
city
Distance
#3:Further galaxies are moving away at higher velocities than nearby galaxies!!The Universe is accelerating apart
Hubble put together the amount of redshift of galaxies
Velo
city
Distance
Refer to pg 17 in your Earth Science Textbook as we do this activity together
Follow-up questions: 1. Did the distance between A and B or between
C and B show the greater rate of change? 2. Did the rate of change for either set of dots
differ during the first or second time period? 3. Suppose C and A represent galaxies and dot
B represents the Earth. How does the distance between galaxies and Earth relate to the rate at which they are moving apart?
Velocity: the distance traveled over a certain time in a given direction
v=d/t*fundamental units are in ()
v = velocity, measured in meters per second (m/s)
d = distance, measured in meters (m) t = time, measured in seconds (s)
1. If a star travels 3000 kilometers in ten seconds, what is its velocity?
2. How can you rewrite the formula v=d/t to solve for d? For t?
1. If a comet is travelling at 200 kilometers per second for 20 seconds, how far did it travel?
During the wartime blackouts in California, Walter Baade discovered two different populations of stars in Andromeda
This led to realizing there are two types of Cepheids, with two different period-luminosity relationships.
Hubble had unknowingly used the wrong relationship.
Yardstick vs Metersticks
Steady State Theory: As universe expands, matter is created.
Big Bang: running expansion backwards leads us to a point of high density and high temperature from which universe originated. (Create everything all at once)
[show clip of 1955 Cosmic Times showing “Origin of Everything” article ?]
Fred Hoyle, Hermann Bondi and Thomas Gold see the movie The Dead of Night, in which the end of the story circles back to its beginning.
Unchanging situations need not be static New matter can be created spontaneously as the universe
expands (a few hundred atoms per year per galaxy) Expansion of universe and creation of new matter balanced
via a negative energy. The universe is constant in its overall density
Starting from earlier work, George Gamow & Ralph Alpher worked out the conditions in the early universe
Universe is expanding from a state of high density and pressure.
Hydrogen & Helium were formed as universe cooled. There should be left over a background radiation
with a temperature of ~ 5 Kelvin
Hoyle scoffed at this theory and coined the term “Big Bang”
Scientists Sort through Theories by examining Evidence and making Inferences
Bowl of Evidence
Penzias and Wilson were using a 20-foot horn detector to make radio observations of the Milky Way.
Effort to reduce noise in the detector left them with a 3 K residual. But they didn’t know its origin.
Peebles and Dicke (Princeton) had just calculated an estimate for the temperature of the residual background temperature, and found it was detectable in the microwave region. Peebles and Dicke were convinced that Penzias and Wilson had found it.
This solved the Steady State vs Big Bang question.
Show clip from 1965 CT, with “Murmur of a Bang” and “Big Hiss”
How can we envision an expanding universe?
1965 CMB Activity
1919 - Confirmation of Einstein’s Theory of Gravity
1929 - Hubble’s discovery of Expanding Universe
1955 - Debate between Big Bang and Steady State
1965 - Discovery of the Cosmic Microwave Background
1993 - COBE Results; Development of Inflation Theory
2006 - Grappling with Dark Energy.
Our understanding of the Expansion of the Universe
Nature of Supernovae The size and scale of the Universe
A number of other themes also appear. Impact of improved technology. Role of Women in early astronomy.
Objectives: The students identify and describe unfamiliar scientist “heroes” that contributed to the field of science up to the year 1929.
Summary: identify the women scientists of the Harvard
College Observatory use the world wide web to complete a product
on one of the these unfamiliar scientific “heroes” that they discovered in their research.
A print of this Harvard College Observatory photograph was found in an album that had once belonged to Annie Jump Cannon.
These women assisted Pickering in measuring stars and features on the photographic plates.
Pickering’s Harem
“Newsletter version” for individual student use
http://cosmictimes.gsfc.nasa.gov/
1919 & 1929 Posters and Lessons now Available
This presentation is available (with links to lessons)
1955 materials available soon. Sign up for email updates