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
How do we know how far away, how big and how old things are in the Universe?
” We look at the light
“ Light years…distance ~ time
What did NASA’s Hubble Deep Field Image discuss?
- The Hubble Space Telescope
- the expansiveness of the Universe
- the relationship between distance and time
The forces appeared after the big bang
- Gravity
- Strong Force (holds nuclei of atoms together)
- Magnetic force (holds atoms together, drives electricity and magnetism)
- Weak force (not important for our story)
What does inflation mean?
In ~10-32 seconds after the Big Bang, the Universe (fabric of space time)
expands faster than the speed of light, from the size of an atom to the size of a galaxy.
What happened in the first 10ˆ-10 seconds after the big bang?
Only quarks, subatomic particles that form atoms, could form
10ˆ15 degrees
What happened 10ˆ-5 seconds after the big bang?
protons (H+) and neutrons formed
10ˆ10 degrees
What happened 3 mins after the big bang?
Hydrogen nuclei fuse to form helium (and deuterium, And lithium…)
10ˆ9 degrees
What is fusion (nucleosynthesis)? give examples
Fusion happens when colliding particles fuse to form a new, larger nucleus.
Which forms of hydrogen formed helium?
Deuterium and tritium are versions of hydrogen in which a proton fused to one or two neutrons, respectively. These nuclei, in turn, can collide to form a helium nucleus.
When did nucleosynthesis start happening after the nucleosynthesis?
1 second < Nucleosynthesis < 5 minutes
H+ + neutron
Deuterium (D)
2 H+ + neutrons
Helium (He)
3 H+ + neutrons
Lithium (Li)
_____ and ______ were essentially the only elements present in the early Universe, and remain to this day, the most abundant elements in the Universe.
Hydrogen
helium
How many years after the expansion and cooling did the atoms start to bond
After about 380 000 years of expansion and cooling, atoms began to bond
How did matter become neutral?
Negatively charged electrons attached to positively charged protons, matter becomes electrically neutral
What is the earliest light of Universe?
Photons are free! They form the cosmic microwave background (CMB) – the earliest light in the Universe.
What is the fuel of stars?
Hydrogen formed H2 molecules—the fuel of stars
What happened to atoms and molecules 380 000 years after the Big Bang?
Atoms and molecules coalesced into gaseous nebulae.
What is Cosmic Microwave Background?
One piece of evidence supporting Big Bang Theory:
There is a background energy coming from everywhere in the Universe from when matter went from ionized to electrically neutral.
The ancient light, called the cosmic microwave background, was imprinted on the sky when the universe was 380,000 years old.
What is Black Body Radiation?
The shape and intensity of the radiation spectrum is characteristic of a given temperature.
What happened in the first 5 minutes after Big Bang?
- forces appeared
- inflation occurred
- subatomic particles formed
- protons (H+) and neutrons formed
- helium and lithium formed due to fusion (nucleosynthesis)
What happened around 380,000 years after the Big Bang?
” matter becomes electrically neutral.
“ the cosmic microwave background (CMB) – the earliest light in the Universe.
“ Hydrogen formed H2 molecules—the fuel of stars.
“ Atoms and molecules coalesced into gaseous nebulae.
How were the elements that are heavier than H and He formed?
To produce elements heavier than H and He, nuclear particles had to be added to their nucleus in order to increase the number of protons in the nucleus.
Chemical reactions vs nuclear reactions
In contrast to chemical reactions which involve sharing of electrons in different atoms and can readily occur at room temperature, nuclear reactions require extreme temperatures (i.e., > 50 million degrees) and pressures to fuse nuclei (e.g., to overcome the electrical repulsion exerted by one proton over another).
How did heavier elements form?
To form heavier elements, we had to wait for stars to form
when did heavier elements form?
until about ~200 millions years after the Big Bang.
Where did the energy come from to form heavier elements?
Gravity!
Gravity caused collapse of gaseous nebulae, resulting in increases in:
- Temperature.
- Density.
- Rate of rotation.
True/False
Mass in nebulae was equally distributed
False
Mass in nebulae was not equally distributed
How did protostar form?
- Mass in nebulae was not equally distributed.
- An initially more massive region began to pull in gas.
- This region gained mass and density.
- Mass compacted into a smaller region and began to rotate.
- Rotation rate increased, developing a disk shape.
- The central ball of the disk became hot enough to glow.
- A protostar was born!
What happened with the growth of the protostar?
The protostar continued to grow,
- pulling in more mass and creating a denser core.
- Temperatures soared to 10 million degrees.
- At these temps, hydrogen nuclei fused to create helium. - With the start of nuclear fusion, the protostar “ignited”
- Nucleosynthesis occurs (starting with hydrogen burning to form helium)
How do starts not collapse?
Fusion releases energy at the center of the star, which pushes outwards, resisting gravity and preventing the star from collapsing.
What are the element layers on stars?
H-burnings He-burnings C-burnings Na-burnings O-burnings Si-burnings
from outside to inside
Death of a star is called
supernova
How does supernova happen?
- Silcon (Si) fusion creates iron (Fe) at the center of the star. There is not enough energy for Fe fusion, and Fe fusion absorbs energy rather than releasing energy like the fusion of lighter elements. So fusion stops.
- Gravity wins! Star collapses.
- Supernova Explosion! Enough energy to fuse iron (Fe) and create heavier elements.
- The process repeats, making more heavier elements….
This expanding cloud of gas, ejected into space from a supernova explosion whose light reached the Earth in 1054 C.E., is called the ________.
Crab Nebula
(in terms of elements) First-generation stars left _____
a legacy of heavier elements
(in terms of elements) Second-generation stars repeated _____
heavy element genesis.
What generation of star is the sun?
The sun may be a third-, fourth-, or fifth-generation star
The mix of elements found on Earth include
- Primordial gas from the Big Bang.
- The disgorged contents of exploded stars
What was the first element to form after the Big Bang?
hydrogen
A light spectrum measured from a distant star is red-shifted. That means the star is:
moving away from us
Light observed from distant stars is redshifted. This evidence supports that the ______ is _____.
universe is expanding
Fusion releases energy at the center of the star, which pushes outwards, resisting _______ and preventing the star from collapsing.
gravity
Which is the oldest planet in the Solar System?
All planets in the Solar System are the same age
Where Do Elements Come From?
- First-generation stars left a legacy of heavier elements.
- Second-generation stars repeated heavy element genesis.
- Succeeding generations contain more heavy elements
What generation star is the Sun?
The sun may be a third-, fourth-, or fifth-generation star.
The mix of elements found on Earth include
- Primordial gas from the Big Bang.
- The disgorged contents of exploded stars.
How did the solar system form according to the nebula hypothesis
A second- or third- generation nebula forms from hydrogen and helium left over from the big bang, as well as from heavier elements that were produced by fusion reactions in stars or during explosion of stars.
