Transcript The Universe in a Day - UC Berkeley Astronomy w

Prof. Geoff Marcy
Jupiter and Europa
Saturn and Enceladus
Textbook:
The Cosmic Perspective
Bennett et al. (2010)
Purchase Bookstore version
to get kit for homework:
MasteringAstronomy
www.masteringastronomy.com
www.masteringastronomy.com
Course
ID: THEPLANETSFALL2012
See instructions
at end of this lecture
Reading this week and next week: Chapters 1 and 2
“Our place in the Universe “ & “Discovering the Sky”
Homework: Due every Friday at 6pm
Chapter 1 and Chapter 2 Assignments:
due Friday Aug 31 at 6pm  Tuesday Sept. 4 @ 6pm
5% off for each wrong try. 2% for a hint.
Description of Course
• Tour of the Solar System, the Space Program and the physics,
chemistry, geology, and experiments and reasoning that explains it all.
• Observations and space missions.
• Learn physical and chemical processes that formed and continue
to shape the Solar System: Past, Present and Future.
Intended for Non-Science Majors (light on math)
Objectives of Course
• Learn the process of careful thinking and reasoning
• Work with others: group reasoning
• Learn to estimate answers with a factor of 2
Basic Science:
• Concepts of physical, chemical & biological sciences:
• Force, Energy, Atoms, Nuclei, and DNA
• How to calculate with very large and small numbers
12 Discussion Sections
• 1 hour: All start this week.
• Review, Clarification, Homework Help. Sign up on Telebears
101 Wed 9-10A,
102 Wed 1-2P,
103 Wed 2-3P,
104 Wed 3-4P,
105 Th 2-3P,
106 Tu 2-3P,
107 Th 11-12P,
108 Tu 11-12P,
109 Tu 12-1P,
110 Th 12-1P,
111 W 11-12P,
112 Wed 12-1P,
265 McCone Hall: Ben Legg
264 Evans Hall: Lea Hirsch
264 Evans Hall: Tess McEnulty
241 Cory Hall: Tess McEnulty
264 Evans Hall: Lea Hirsch
264 Evans Hall: Tess McEnulty
264 Evans Hall: Ryan Turner
264 Evans Hall: Ryan Turner
264 Evans Hall: Drummond Fielding
264 Evans Hall: Lea Hirsch
264 Evans Hall: Ben Legg
264 Evans Hall: Drummond Fielding
Observing Project #1
Two choices
A) Chart the position and shape of the moon.
Sketch where the moon is located relative to nearby buildings. Also
sketch the shape of the moon. Mark which direction is south.
Note the time and day on the sketch.
Wait 2-5 days, and do it again. (Hint: the moon is up now from 7pm-midnight)
Turn in both sketches, with time and date of observation.
Write three to four sentences about any change you saw in the position or shape.
B) Sketch where the Sun sets, relative to buildings.
Wait 4-10 days. Sketch where the Sun sets again.
Turn in both sketches, with time and date of observation.
Write three sentences about any change
in the position of sunset. Did it change? What direction?
By how many degrees (approx.)?
(The sun has an angular size of 0.5 degrees in diameter.)
Due in class, Thursday Sept. 6
1 page maximum; Handwritten is fine.
Course material on bSpace: http://bspace.berkeley.edu
• Syllabus
• Lecture slides
• Assignments: reading, homework, observing projects
• Course information
Last Time ::
The Solar System
Inner Solar System
Outer Solar System
Overview
Our place in the Universe
13 billion
Light Years
The Solar System:
Sun and 8 Planets
Moons, Rings, Asteroids, Comets, and Dust
Milky Way Galaxy
Photo taken from Earth
200 Billion Stars
You Are Here
Our Milky Way Galaxy
Our Sun and the stars orbit
around the center of the Milky
Way Galaxy every 230 million
years.
Our Sun moves relative to
the other stars in the local
Solar neighborhood.
Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies
The ``Local Group”
of Galaxies
100,000 Light Years
The Galactic Neighborhood
The ``Local Group’’
of Galaxies
And
outward…
10 Million Light Years
B
The Universe:
All matter and energy
> 100 Billion Galaxies
B
Astronomical Numbers
Best to use Exponential Notation
103 = 1000
Thousand
106 = 1,000,000
Million
109 = 1,000,000,000
Billion
1012 = 1,000,000,000,000 Trillion
Also: 10–3 = 1/1000 = 0.001
Exponential notation is handy:
10N x 10M = 10(N+M)
Example:
103 x 106 = 109
thousand
million
billion
B
Interactive Quiz
How many stars in our
visible Universe?
A.
B.
C.
D.
1012 (1 million million)
1018 (1 billion billion)
1022
infinite
B
Interactive Quiz
How many stars in our
visible Universe?
A.
B.
C.
D.
1012 (1 million million)
1018 (1 billion billion)
1022
infinite
Number of Stars in a galaxy: ~100 billion = 1011
Number of galaxies in Universe: 100 billion = 1011
Federal
There are 1011 stars in the galaxy.
That used to be a huge number.
But it's only a hundred billion. It's
less than the national deficit! We
used to call them astronomical
numbers. Now we should call them
economical numbers.
Richard Feynman
B
B
Federal Debt
In 2005, the National Debt was
$7.6 Trillion
= $7.6 x 1012
U.S. Population
= 300 x 106
Trillions of Dollars
Calculate Your Personal Debt:
$7.6 x 1012 / 3 x 108 = $2.5 x 104
= $25,000
$25,000 per person in 2005.
02 03 04 05
Debt Total
B
Population of France: 65 million
Loss per person: $7x109 / 6.5x107 = $107
Transfer of 350 million Euros
Population of Germany: 75 million
Loss per person: 4.66 Euros -- Cheap!!
B
Population of US: 300 million
Cost per person: $7.87x1011 / 3x108 = $2623
B
B
All UC campus have 200,000 students.
How much will your annual fees increase?
(A) $100
(B) $250
(C) $1000
(D) $2500
5×108 / 2×105=2.5×103=$2500
B
Distance, time and number :
Scientific notation:
Radius of our Galaxy:
6,000,000,000,000,000,000 m =
Radius of a Hydrogen atom:
0.00000000005 m =
6 x 1018 m
0.5 x 10–10 m
Time for one vibration of an oxygen molecule, O2:
0.00000000000001 s =
1 x 10–14 s
Age of the Universe:
470,000,000,000,000,000 s =
4.7 x 1017 s = 14 billion years
B
SI (Systeme International) Units
Base units: 1 meter (m)
length ~ 3.3 ft
1 kilogram (kg)
mass ~ 2.2 lb
1 second (s)
time
MKS System of units and measure
B
SI (Systeme International) Units
Base units: 1 meter (m)
length
1 kilogram (kg)
mass
1 second (s)
time
MKS System of units and measure
Sometimes easier to derive other units from these:
km, g, ms, µs, …
km = 103 m
kilo
g = 10-3 kg
kilo
ms = 10-3 s
milli
µs = 10-6 s
micro
B
UNITS ARE IMPORTANT!!!
Mars Climate Orbiter:
Launch: 11 Dec. 1998
Orbit insertion:
23 Sep. 1999
Followed by:
Loss of
Communication
WHY?
Failed to convert from English units (inches, feet, pounds)
to Metric units (MKS)
$Billion error
B
Light takes time to travel:
3 x 108 m/sec
= 3 x 105 km/sec = 300,000 km/sec
= 0.3 m/ns
(1 ns = 10-9 s)
Light Year = 9 trillion km = 6 trillion miles
Light Hour
Light Minutes are unit of Distance:
How far Light Travels in that interval of time
1 light second = 3 x 105 km
1 light ns = 30 cm ≈ 1 foot
How long does it take the sun’s light to reach the Earth?
Distance
d = 1AU = 1.5x1011m
Speed of light v = 3x108 m/s
d 1.5 1011 m
3
t 

0.5
10
s  8 min
8
v 3 10 m /s
Time

B
B
Driving the Mars Exploration
Rovers (MER)
• How long
does it take to
communicate
with the
rovers?
NASA/JPL/Cornell
B
Interactive Quiz
How long does it take for radio
waves (light) to reach Mars?
A.
B.
C.
D.
Less than 1 second
1 minute
10 minutes
1 hour
B
Interactive Quiz
How long does it take for radio
waves (light) to reach Mars?
A.
B.
C.
D.
Less than 1 second
1 minute
10 minutes
1 hour
Earth-Mars distance: between 55 and 400 million km.
tmin = dmin/v = 5.5×107 km / (3×105 km/s ) =1.8×102s= 3 minutes
tmax = dmax/v = 4.0×108 km / (3×105 km/s ) =1.3×103s= 22 minutes
G
Powers of Ten
“Cosmic Voyage”
The Movie
G
How to deal with very large & small numbers
•Develop a useful arithmetic
Exponential notation; convert between units
•Visualize using a sequence of images (movie)
Use different sequences
•Visualize by way of a scale model
Try different models
A Scaled Model of the Solar System
10 Billion x Smaller
Sun’s diameter: 14 x 1010 cm
Reduce by 1010:
1010
Scaled Down
“Sun”
14 cm
14cm
Earth diameter:
13000 km
Jupiter’s diameter: 150,000 km
0.13 cm
1.5 cm
Earth’s distance from Sun: 1 “Astronomical Unit” = 1 “AU”
1 AU
?? cm
= 1.5 x 108 km
A. 1.5 cm
B. 15 cm
Ans: 1500 cm = 15 meters
C. 150 cm
D. 1500 cm
G
How large is the Solar System?
• Let’s view it to scale
– Say the Sun is the size of a large grapefruit, 14 cm (6 inches)
- then:
Planet
Dist (AU)
Scaled Dist (m)
Where?
Mercury
0.4
6
6 rows back
Venus
0.7
10
10 rows
Earth
1.0
15
15 rows
Mars
1.5
22
22 rows
Jupiter
5
75
3/4 football field away
Saturn
10
150
1.5 football field away
Uranus
20
300
Sproul Plaza
Neptune
30
450
Bancroft Ave
Pluto
50
750
Durant Ave
Oort Cloud 50,000
5 x 105
Oakland
G
You Are Here:
Earth’s Orbit
Saturn
Uranus
o
.
Neptune
o
o
Jupiter
. o
G
How Far is the Nearest Star?
Alpha Centauri
d = 4 light years
= 4 x 1016 m
Scales to:
4 x 106 m
(~ 3000 mi)
Grapefruit-sized
Sun in Berkeley
Nearest Grapefruit:
In Washington D.C.
G
A Universe in motion
• Contrary to our perception, we are not “sitting still.”
• We are moving with the Earth.
– and not just in one direction
The Earth rotates around
it’s axis once every day!
G
The Earth orbits around
the Sun once every year!
The Earth’s axis is tilted
by 23.5º!
B
Looking back in time
• Light, although fast, travels at a finite speed.
• It takes:
– 8 minutes to reach us from the Sun
– 8 years to reach us from Sirius (8 light-years away)
– 1,500 years to reach us from the Orion Nebula
• The farther out we look into the Universe, the farther
back in time we see!
B
What is the origin of the Universe?
(1) The two simplest atoms
(H and He) were created
during the Big Bang.
(2) More complex atoms were
created in stars.
(3) When the star dies, chemical
elements are expelled into
space…. to form new stars and
planets!
Most of the atoms in our bodies
were created in the core of a star!
B
Balloon experiment
B
The Milky Way moves with the expansion of
the Universe!
• Mostly all galaxies
appear to be moving
away from us.
• The farther away they
are, the faster they are
moving.
– Just like raisins in a raisin
cake; they all move apart
from each other as the
dough (space itself)
expands.
B
How old is the
Universe?
• The Cosmic
Calendar
– if the entire age of
the Universe were
one calendar year
– one month would be
approximately 1
billion real years
B
Key Issues So Far:
• What does our solar system look like when
viewed to scale?
• How far away are the stars?
• How do human time scales compare to the age
of the Universe?
B
TODAY’S LECTURE
• Solar System Resides within our Milky Way Galaxy
• Ranges of distances and time are huge.
• Exponential notation and models are a real Help!
• Distance Units:
1 Astronomical Unit (AU) = Earth - Sun Distance
= 93 million miles
= 150 million km
B
The Universe in a Day
Look at the entire history of the Universe as though it
took place in a single day. The present is at the stroke of
midnight at the end of that day. Since it is about 13.5
billion years old, each hour will be ~0.5 billion years. A
million years takes only a little over 7 seconds.
The Big Bang (a dense, hot explosion) and the formation
of H and He all take place in the first nanosecond. The
Universe becomes transparent in about 2 seconds. The
first stars and galaxies appear after about 2am.
Our Galaxy forms at 4am. Generations of stars are
born and die.
B
The Universe in a Day
The Solar System does not form until 3pm. The first life (bacterial)
appears on the Earth by 4pm. Our atmosphere begins to have free
oxygen at 7 or 8 pm, and this promotes the development of
creatures which can move more aggressively and eat each other.
Life does not begin to take on complex forms (multicellular) until
10:45pm. It moves onto land at 11:10. The dinosaurs appear at
about 11:40, and become extinct at 11:52. Pre-human primates
appear at around 14 seconds before midnight, and all of recorded
history occurs in the last 70 milliseconds.
Looking to the future, we can expect the Universe of stars to go on
for at least another millennium (using the same time compression
factor). After that, there are other ages of the Universe (not
dominated by stars), which grow colder and more bizarre, and take
place on astronomical timescales…
What is the Earth’s velocity about the Sun?
Radius of Orbit (1 AU): 150 x 106 km
Circumference: 2 π x radius
Distance around the Sun that the Earth travels:
2 π x (1.5 x 108 km) = 9 x 1011 m
Earth orbits the Sun once a year:
1 yr = 3 x 107 s
Velocity = Distance/Time = 9 x 1011 m / 3 x 107 s
= 3 x 104 m/s = 30 km/s
110,000 km/hr or 75,000 miles/hr!
B