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study guide

17 Pages
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Department
Astronomy & Astrophysics
Course Code
AST201H1
Professor
Stefan Mochnacki

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AST201
Universe
Totality of space, time, energy, and matter
No outside
Big Bang: Beginning of the expansion of the universe
About 13.7 billion years old
Elements are manufactured by the recycling of stars
Observable universe is separated from the rest of the universe by a
horizon
Observable universe is the part of the universe that the laws of physics
allow us to see
How much can be seen of the universe (Observable Universe)?
1)Speed of light = c = 300 million m/s (in a vacuum)
a.Light Year = DISTANCE light travels in one year = 9.46 trillion
km
b.Observation of objects many light years shows us what
happened to those objects that many years ago (Since light
takes time to travel to us, looking far away means we are looking
back in time)
c.Light from the end of the universe have not reached us
d.Limit imposed by nature to how far we can see (Observable
universe)
e.Closest star is Alpha Centauri (4.4 light years away)
Structures in the Universe
1)Planets spherical bodies which orbit stars directly; can be rocky,
gassy, liquid, or icy
a.Pluto = dwarf planet (has not cleared its orbit)
2)Stars enormous spheres of very hot gas which produce energy by
nuclear fusion exp. Sun
3)Solar system one or more planets orbiting a star
4)Galaxy Collection of Billions of stars all orbiting a common center
a.Most galaxies are rotating like a disk
i.Virtually every galaxy outside the Local Group is moving
away from us
ii.The more distant the galaxy, the faster it appears to be
racing away
b.Earth is in the Milky Way galaxy (Spiral Galaxy)
www.notesolution.com
c.Closest (large) neighbor galaxy Andromeda Galaxy (Spiral
Galaxy)
5)Local Group Few of the galaxies who all orbit one another
a.All of the galaxy clusters in the Universe are moving apart from
one another
6)Superclusters Enormous group of galaxies all orbiting one another
(1000s or 1000000s of member galaxies)
a.Our supercluster = Virgo Supercluster
Science Process of trying to find natural explanations for natural
phenomena by repeatedly following a cycle of hypothesis, prediction, and
observation or experiment
Scientific propositions must be falsifiable (can be proven false)
Hypothesis Educated guess
Scientific Method: 1) Make Observations, 2) Ask a question, 3) Suggest
Hypothesis, 4) Make a Prediction, 5) Perform Test
Motion
Earths Rotation daily spin
Earths Orbit Revolution around the sun (years)
- Earth is on an axis tilt (results in seasons)
1)Speed Rate at which an object moves (m/s) = distance/time
2)Velocity Speed and Direction
3)Accelerations any change in velocity units of speed/time (m/s
2)
Acceleration of Gravity
All falling objects accelerate at the same rate (vacuum)
g = 9.81 m/s
2 on Earth
Does not change regardless of mass
Momentum = mass x velocity
Net force changes momentum, which generally means an acceleration
Rotational momentum of a spinning or orbiting object is known as
angular momentum
Angular Momentum = mass x velocity x radius
Mass amount of matter in an object
Weight Force that acts upon an object
Astronauts are weightless in space
oThere is gravity in space
www.notesolution.com
oWeightlessness due to constant state of free fall (Nothing to stop
acceleration due to gravity)
Newtons Laws
Discovered laws of motion and gravity
Realized the same physical laws that operate on Earth also operate
elsewhere in the universe
First Law of Motion: An object moves at constant velocity unless a net force
acts to change its speed or direction
Second Law of Motion: Force = Mass x Acceleration
Third Law of Motion: For every force, there is always an equal and opposite
reaction force
Conservation Laws in Astronomy
1)Conservation of Momentum
a.Total momentum of interacting objects cannot change unless an
external force is acting on them
b. Interacting objects exchange momentum through equal and
opposite forces
2)Conservation of Angular Momentum = mass x velocity x radius
a.Angular momentum of an object cannot change unless an
external twisting force (torque) is acting on it: therefore angular
momentum stays constant (increase of radius = decrease of
velocity)
b.Planets move more faster when it is closer to the Sun
c.Earth experiences no twisting force as it orbits the Sun, so its
rotation and orbit will continue indefinitely (except tidal forces)
Objects Energy
Energy makes matter move
Energy is conserved
oTransfer from one object to another
oChange in form
1)Kinetic (motion)
2)Radiative (light)
3)Stored or potential
4)Thermal Energy
www.notesolution.com

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Description
AST201 Universe Totality of space, time, energy, and matter No outside Big Bang: Beginning of the expansion of the universe About 13.7 billion years old Elements are manufactured by the recycling of stars Observable universe is separated from the rest of the universe by a horizon Observable universe is the part of the universe that the laws of physics allow us to see How much can be seen of the universe (Observable Universe)? 1) Speed of light = c = 300 million ms (in a vacuum) a. Light Year = DISTANCE light travels in one year = 9.46 trillion km b. Observation of objects many light years shows us what happened to those objects that many years ago (Since light takes time to travel to us, looking far away means we are looking back in time) c. Light from the end of the universe have not reached us d. Limit imposed by nature to how far we can see (Observable universe) e. Closest star is Alpha Centauri (4.4 light years away) Structures in the Universe 1) Planets spherical bodies which orbit stars directly; can be rocky, gassy, liquid, or icy a. Pluto = dwarf planet (has not cleared its orbit) 2) Stars enormous spheres of very hot gas which produce energy by nuclear fusion exp. Sun 3) Solar system one or more planets orbiting a star 4) Galaxy Collection of Billions of stars all orbiting a common center a. Most galaxies are rotating like a disk i. Virtually every galaxy outside the Local Group is moving away from us ii. The more distant the galaxy, the faster it appears to be racing away b. Earth is in the Milky Way galaxy (Spiral Galaxy) www.notesolution.com c. Closest (large) neighbor galaxy Andromeda Galaxy (Spiral Galaxy) 5) Local Group Few of the galaxies who all orbit one another a. All of the galaxy clusters in the Universe are moving apart from one another 6) Superclusters Enormous group of galaxies all orbiting one another (1000s or 1000000s of member galaxies) a. Our supercluster = Virgo Supercluster Science Process of trying to find natural explanations for natural phenomena by repeatedly following a cycle of hypothesis, prediction, and observation or experiment Scientific propositions must be falsifiable (can be proven false) Hypothesis Educated guess Scientific Method: 1) Make Observations, 2) Ask a question, 3) Suggest Hypothesis, 4) Make a Prediction, 5) Perform Test Motion Earths Rotation daily spin Earths Orbit Revolution around the sun (years) - Earth is on an axis tilt (results in seasons) 1) Speed Rate at which an object moves (ms) = distancetime 2) Velocity Speed and Direction 3) Accelerations any change in velocity units of speedtime)(ms Acceleration of Gravity All falling objects accelerate at the same rate (vacuum) g = 9.81 ms2 on Earth Does not change regardless of mass Momentum = mass x velocity Net force changes momentum, which generally means an acceleration Rotational momentum of a spinning or orbiting object is known as angular momentum Angular Momentum = mass x velocity x radius Mass amount of matter in an object Weight Force that acts upon an object Astronauts are weightless in space o There is gravity in space www.notesolution.com
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