ILU Exam 1

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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


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