Chapter 1: The Earth in Context Slide Set 1 Flashcards
Define universe
- All of space
- All of the matter and energy within it
What is cosmology?
the scientific study of the Universe.
can look at:
- Structure
- History
What did people know about the universe 3000 years ago?
- The stars are fixed relative to each other.
- All the stars rotate about a fixed point.
- The planets move against the background of stars.
What did people not know about the universe 3000 years ago?
- They did not know that Earth is a planet.
- They did not know how “heavenly bodies” move.
Up until the end of the Middle Ages (ca. 476-1400 C.E.) it
was thought that the Universe was ______
geocentric
What does geocentric mean?
- Earth sat at the center of the universe.
- The moon, planets, and stars circled a motionless Earth.
- Ptolemy (100–170 C.E.) proposed equations to predict the movements of planets.
The _______ model of universe gained acceptance during the Renaissance (15th century).
heliocentric
What does heliocentric mean?
- The sun lay at center of the universe.
- Earth and planets orbited the sun.
Who are the scientist in renaissance that studied the universe and what did they propose?
- Copernicus & Galileo—studies led to acceptance that Earth and planets orbit the sun
- Newton—planet motion was explained by Theory of Gravity
What was proposed about the universe in modern era?
Neither the Earth nor the Sun are at the center of the Universe, and everything is in motion
What are stars?
immense balls of incandescent gas
______binds stars together into vast galaxies.
gravity
How many galaxies are there in the visible universe?
Over 100 billion galaxies exist in the visible universe.
Where is our Solar System located in the Milky Way galaxy?
Our Solar System is on an arm of the Milky Way galaxy.
How many stars are there in the Milky Way Galaxy?
Our sun is just one of 300 billion stars in the Milky Way
How far is the sun from Earth?
The sun is “only” 150 million km away
What is a light-year?
A light-year is the distance light travels in one year.
- equal to about 10 trillion km.
How far away is the closest star to our sun?
The closest star beyond our sun is over 4 light-years away.
How many light years is our Milky Way Galaxy across?
Our Milky Way galaxy is 120,000 light-years across
How far away is the edge of the visible universe?
Edge of the visible universe: >13 billion light-years away
In the geocentric model of the Solar System, ____ is the center of the Solar System.
The Earth
Our Solar System lies ___ of the Milky Way Galaxy.
on an outer arm
What is The Big Bang Theory?
13.8 x 109 years ago, all mass and energy was contained in an infinitesimally small point. It was unimaginably hot, and expanding unimaginable rapidly (like an explosion), and cooling. The modern Universe is still expanding.
When did The Big Bang happen?
13.8 x 109 years ago (13.8 billion)
What is the Doppler Effect?
Sound waves compress or relax with relative motion
The Doppler effect is observed whenever the source of waves is moving with respect to an observer. The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding
Which color has higher frequency: red or blue?
blue
What is a frequency?
Time interval between the passage of each wave through a fixed point.
What is a wavelength?
Distance between successive waves.
Moving away from a source will be _____ wavelength
red-shifted
Moving towards a source will be _____ wavelength
blue-shifted
Hydrogen atoms in a star absorb certain specific wavelengths of light. How do we see these wavelengths on a light spectrum?
We see these wavelengths as dark lines on a light spectrum.
Hydrogen light observed from distant galaxies, shifted to longer wavelengths or towards the _____ of the light spectrum thus called ______
red
Red Shift