ILU Exam 1
Gravity is a fact:
things fall down, planets orbit the sun...
How did discoveries of Galileo contradict old ideas?
"natural motion" - objects stayed in motion unless they felt a force to stop them, moon has mountains like earth, sun has blemishes and rotates, Saturn had "ears," Jupiter had 4 moons in orbit, phases of Venus could only be explained if it was in orbit around the sun
Which of the following is the best place to look in our solar system for life (besides Earth)?
Mars
A light year measures
9.46x10^12 m, about 10 trillion km
How does a theory progress to a "Law?"
A mathematical proof that will not allow any exceptions is required. This makes them very rare.
What is a theory in science?
A model that explains a wide variety of observations in terms of just a few general principles, which has survived numerous tests to verify its predictions and explanations.
Particle formation during the big bang
All of the hydrogen and most of the helium now present in the universe was formed during the earliest stages of the universe.
The nearest star system is
Alpha Centauri, 4.4 ly away
How is modern science rooted in ancient astronomical observations?
Ancient cultures observed the motions in the sky for religious and practical reasons. Science took root as they eventually sought to understand the patterns they had discovered.
What are we (NASA) searching for?
Anything that could be life, microbes, plants, animals, little green men, habitable worlds
Which of the following is NOT a main question of Astrobiology?
Are other civilizations interested in communicating with our planet?
Who first showed that the sun was the center of the solar system?
Aristarchus (~300 BC)
How were astronomy and astrology related in the past, and are they still related today?
Astronomy and astrology both grew out of ancient observations of the sky. Astronomy grew into a modern science. Astrology has never passed scientific tests and does not qualify as science.
What sciences form Astrobiology?
Astronomy, Planetary Science, Biology, Chemistry
How long have humans believed that life existed elsewhere than earth?
Believing that life exists beyond our Earth is not new, it has been considered for millenia
Kepler, German 17th Century
Brahe's assistant, used his data to precisely determine the orbit of Mars (& other planets), discovered orbits not perfect circles but elliptical
Our solar system has overall structure
Disk shaped, All planets go around the sun in the same direction, The sun rotates in this direction, Planets and moons rotate in this same direction
Gravity is Universal
Every object that has mass attracts every other object with mass, Newton discovered that the pull of gravity is proportional to product of the masses of the two bodies, and inversely proportional to the distance between them squared.
Newton's Law of Universal Gravitation
F=(Constant)(Mass1)(Mass2)/(distance between centers)2 - applies to all matter
Philosopher Thales asked "What is the universe made of?"
Flat disk of earth floating on an infinite ocean
Three main questions of Astrobiology that persist:
How did life get started on Earth and evolve? What conditions could support life on other planets? How do we find this life?
As one of the sciences that make up astrobiology, biology is useful in showing us:
How life works
What is SETI searching for?
Intelligent life capable of radio transmission
When diagnosing a disease, doctors frequently rule out many possibilities even though they might have the same symptoms. Why?
It makes sense to look for common things rather than unusual ones, Occam's Razor applies
Who is famous for showing that orbital paths are elliptical?
Kepler
Who were the last astronomers to cast horoscopes?
Kepler and Galileo
Universal Law of Gravitation
Kepler's laws follow logically from Newton's laws and lead to
Where would life most likely be in our solar system?
Mars is the most promising and most explored place besides our moon; also moons of the large planets: Europa, Ganymede, Callisto, Titan, Triton, Enceladus, also Earth
Which of the discoveries of Gallileo showed that not all objects revolve around the Earth?
Moons of Jupiter
Asteroids
Much smaller than planets, Rocky metallic bodies with diameters of a few meters up to ~1000 km, most between Mars and Jupiter (asteroid belt), 1st found was Ceres
Humans first had contact with alien life forms
Never
What is Gravity?
Newton explained that gravity is the same force for a falling apple as it is for the orbital behavior of the moon.
Who's model of the universe solved the problem of not being able to view stellar parallax?
No one solved this problem until the invention of the telescope
How much contact have humans had with aliens?
None
The origin point of the universe is
None
Requirements to be a planet:
Orbit the sun, Spherical under gravity, Cleared the solar system neighborhood of material
How does Planetary Science contribute to the search for life?
Our current model of planetary formation implies that planets should be common, extrasolar planets were first found in 1995
A planet is distinguished from a moon because
Planets orbit the sun and not any other body.
What are the differences between ancient Greek philosophers and modern scientists?
Plato and Aristotle relied on pure thought and intuition rather than on observation and experiment
Using Epicycles to explain retrograde motion was a system developed by:
Ptolomy
How is scientific thinking similar to other everyday thinking?
Scientific thinking involves trial and error like much other everyday thinking, but in a carefully organized way.
What is SETI?
Search for extra terrestrial intelligence
The majority of the matter that makes up the sun today was formed in
The Big Bang
Cosmic Microwave Background Radiation
The photons produced during recombination are still visible everywhere in the universe. Measured by the COBE Satellite
Big Bang model
This model is NOT a picture of an explosion, but of expansion occurring at different rates over time. The Universe HAD A BEGINNING
Galileo's discovery of the Milky Way:
a mass of innumerable stars, suggests that stars are not only more numerous but much more distant, means that parallax exists but is small
How did attempts to understand the sky start us on the road to science?
Tried to explain the motions of the sun, moon and planets; Plato and Aristotle relied on pure thought and intuition rather than on observation and experiment
The correct order of objects from largest to smallest is:
Universe, Local Group, Galaxy, Solar System, Earth
Discovery of Neptune
Uranus' orbit seemed wrong, Leverrier calculated the position of the 8th planet to "fix" Uranus' orbit, wrote a letter to Galle explaining where to look and Gall found Neptune in almost the exact spot
How is SETI searching for life?
Using radio telescopes to listen for encoded radio signals, in 1974 a signal was sent to the globular cluster M13, now we just listen
Galileo proved that the sun must be the center of the universe because:
Venus has phases
Content of the universe
We thought that matter was in stars and galaxies, A spherical halo of dark matter surrounds the galaxy, Dark energy provides a "push" against gravity so that the universe is expanding, We can see only a tiny fraction of the universe (3%)
Astrobiology seeks to answer:
What other planets have conditions similar to Earth? How do we find life? How did life get started on Earth?
Kepler's Law
a line joining a planet and the sun sweeps out equal areas in equal time intervals
theory
a model which survives repeated testing
What is scientific thinking?
a natural part of human behavior, we draw conclusions based on our experiences, progress is made through trial and error
Nuclear fusion
a reaction where heavier nuclei are created by combining (fusing) lighter nuclei, all nuclei are positively charged
What does the death of a low-mass star leave behind?
a white dwarf
A planet is found close to a star. We would expect it to
be made of rock
Pythagoras (~500 BC)
believed Earth was a perfect sphere
Eratosthenes (~200 BC)
calculated circumference of the Earth using math and logic
Astrology
claims to study how the positions of the sun, moon and planets influence human behavior, was the driving force which advanced ancient astronomy
Gravity is a theory:
detailed mathematical models explain why things fall down...
Other approaches to science
discovery, experimental, historical, hypothesis-driven
Pluto belongs to category of:
dwarf planet, determined in 2006 by IAU
Inner planets
earth-like, mainly rock, thin or no atmospheres, solid surface, high density, rock made of Si and O2 plus a mixture of heavier elements like aluminium and iron, iron-nickel core, closest to the sun
nonscience
establishes "truths" through belief, cannot and will not survive testing
Aristarchus (~300 BC) (models of universe)
estimated diameter of Moon at eclipse = .35 (actual .27), estimated relative size and distance of Sun and Moon, found Sun to be a very large distance but wrong by a factor ~20, proposed Sun was center of heavens, problem: parallax
Copernicus (1473-1543)
first person to work out the details of the heliocentric solar system, reinvented Aristarchus' heliocentric model, explained retrograde motion due to different orbital speeds of planets, explained order of planets (distance from sun); did not account for lack of observed stellar parallax, still assumed orbits were circular
Why does fusion occur in the Sun's core ?
for fusion to occur, nuclei must be moving fast enough to overcome E-M repulsion, this requires high temperatures & pressures, When nuclei touch, the nuclear force binds them together
nucleosynthesis
formation of nuclei
The Solar Nebula Theory refers to
formation of the solar system
Outer planets
gas giants, larger than inner, deep hydrogen-rich atmospheres, low density, rich in light elements, solid ice/rock core
How is Einstein's explanation of gravity different from Newton's?
gave a new description of gravity - general theory of relativity, close to the sun, Newton's law doesn't work, consider gravity a curvature of space-time
Discovery science
going out and looking at nature in hopes of finding something new
Massive stars
have more fuel, brighter so they use it up faster
How did discoveries of Galileo contradict old ideas?
he explained "natural motion" which showed that objects stayed in motion unless they felt a force to stop them, heaven is not perfect and unchanging (moon has mountains just like earth), Sun has blemishes and rotates, Saturn has "ears" - not a perfect sphere, Jupiter has 4 moons in orbit, Venus exhibits phases that could only be explained if it was in orbit around the sun - final proof of heliocentric model, Milky Way - a mass of innumerable stars
What were the ideas of Aristotelians?
held that all elements had a "natural place:" rocks fall down, flames rise up, argued that there could only be one Earth, this becomes entwined in Christian theology (1200s) since a divine creator is required to explain the existence of the one and only Earth
What were the ideas of Atomists?
held that the heavens were made of infinite numbers of the four elements: fire, water, earth, air, allowed that infinite numbers of worlds like ours exist and arise out of natural processes
What are the models of the universe?
heliocentric, geocentric
Fusion in a star is
how heavy elements are made
Comets
icy bodies of size ~10 km or less, grow huge trails (dust and ion) when they are near the Sun, have highly elliptical or non-returning orbits, thousands in Kuiper belt, trillions in Oort Cloud
stellar parallax
if the sun is at the center, then as Earth orbits the sun we should see closer stars appear to move with respect to more distant stars, not measured until 1838
The carbon in your body was made
in the core of low-mass (high-mass) stars
2 types of planets
inner (terrestrial), outer (jovian)
Ptolemy (~150 AD)
invented "epicycles" to explain retrograde motion of plantes (planets move in small circles as they orbit the earth), solved retrograde motion and geocentric heavens ruled for the next ~1400 years
The center of the universe
is right here, does not exist
the early Universe likely could not support life because
it contained only H and He, life needs more, all other elements formed in the cores of stars and their explosions
How does Biology contribute to the search for life?
it defines life, except our single example of life on Earth may be too narrow of a view
How can we distinguish science from nonscience?
it seeks explanations for observed phenomena that rely solely on natural causes, it progresses through the creation and testing of models, must make testable predictions
Solar nebula theory
it took a few million years for a cloud to collapse and become a rotating disk with a bulge at the center, bulge became a young sun
Reasons that life might be common
life got started very early on Earth (easy), organic molecules form in a wide variety of harsh conditions implying that the chemistry for life is available everywhere, life exists under a broad variety of extreme conditions on Earth so the possibilities of places to search is broad
Compared to low-mass stars, high-mass stars:
live much shorter lives, die as a supernova; low-mass die as a nebula, can fuse elements heavier than Carbon, may leave either a neutron star or black hole behind, are far less numerous
Historical science
looks at present day evidence in an effort to learn something about the past
Two groups of stars
low mass, high mass
Tycho Brahe, Danish 16th Century
made very large and sensitive instruments to track stars and planets with great precision, found no evidence for stellar parallax, observed supernova in 1572, last to hold onto geocentric model
pseudoscience
masquerades as science, but does not follow the scientific rules of evidence (tabloids and fiction)
The most fundamental part of a star's properties is its
mass
Over time, the theory of gravity has changed. Newton explained gravity as _____________ and Einstein explained gravity as _______________.
mass attracted to other mass, curvature of space-time
In the current search for life in the universe, we are specifically looking for:
microbes, plants, little green men
Aristotle (300 BC)
naked eye observation, curved shape of Earth's shadow on Moon during lunar eclipse, earth spherical not flat
The model proposed by Copernicus with the sun in the center of the universe was still "wrong" by our understanding today because he failed to recognize that
objects move in elliptical paths, not circles, stars exist at much farther distances, our sun is the center of a solar system in a much larger universe
Retrograde motion has been described many different ways in the past. What are these ways?
planets moving on circles around other circles, planets moving around the sun, gods of the sky changing their minds
Hypothesis-driven science
proposing an idea and then performing tests to see if it works
What is hypothesis-driven science
proposing an idea and then performing tests, what the "scientific method" usually refers to
How did the Copernican Revolution alter the ancient debate on extraterrestrial life?
proving Aristotelians wrong means Anatomists were right, so many worlds could exist with life on them, still a wrong assumption today for its reason not necessarily its conclusion
How did the Copernican Revolution alter the ancient debate on extraterrestrial life?
proving the Aristotelians wrong must mean the Atomists were right, so many worlds could exist with life on them, still a wrong assumption today for its reason, not necessarily conclusion
The scientific method
question, hypothesis (tentative explanation), prediction, test, result-confirm, reject, or modify (should be the same no matter who conducts the test
A supernova
results from the death of a massive star, produces heavy elements (larger than iron), releases matter for re-use by other stars.
Hallmarks of science
seeks explanations for observed phenomena that rely solely on natural causes, progress through creation and testing of models of nature that explain the observations as simply as possible, makes testable predictions about natural phenomena. If predictions do not agree with observations, model must be revised or abandoned
Experimental science
seeks to learn general principles of how things work
The universe, smallest to largest
solar system, galaxy-Milky Way, Galaxy cluster-Local Group, Supercluster-Local Supercluster
Cosmic expansion
space-time itself is expanding in those places where it is not bound by gravity or the EM force, Center of expansion is not in present-day 3-D space
Formation of Planets
started out as planetesimals, which accreted first by electric attraction, and then through gravitational attraction and collisions into protoplanets, collisions incredibly common in SS, computer models produce similar results
What three main areas does Astrobiology focus on?
study the conditions conducive to the origin and ongoing existence of life, looking for such conditions on planets in our solar system and around other stars, looking for the actual occurrence of life elsewhere
The Iron (Fe) Problem
supergiant has an inert Fe core which collapses & heats, Fe cannot fuse, Fe core continues to collapse until it is stopped by electron degeneracy (white dwarf)
Where do elements higher than iron come from?
supernovae
Planets are different for different locations around the sun because of
temperature
What is meant by Celestial Sphere?
the heavens must be a perfect sphere (Aniximander), stars no matter how distant, are pictured as being on a single crystalline sphere
Our galaxy cluster is called
the local group
Kepler's Law
the orbit of a planet about the sun is an ellipse with the sun at one focus, Venus has the most circular orbit while Pluto has the most elongated orbit, Earth's orbit is non circular by a factor only ~1/30
How does Astronomy contribute to the search for life?
the physical laws that operate on Earth seem to apply to all other locations of the universe
Kepler's Law
the square of the sidereal period of a planet is directly proportional to the cube of the semi major axis of its orbit: P2=a3
Stellar evolution
they are born, grow up, mature, and die, mass determines what life path it will take
What is the definition of life?
this question is central to biology, life is hard to define
What is retrograde motion?
to move backward in an orbit, of celestial bodies
The event of recombination made the universe
transparent
How did Greece bring the origin of modern science?
tried to understand nature without resorting to supernatural explanations, development of mathematics in the form of geometry, explanations of the world could not be right if they disagreed with observed facts, developed models
Newton's Laws of Motion (gravity)
used simple experimental evidence and theory to deduce the underlying physical laws that govern all motions on Earth and in the heavens
Occam's Razor
when 2 or more explanations for an event exist, the simpler one is generally true, works because more complex explanations require more assumptions
