Transcript The Universe in a Day - UC Berkeley Astronomy Department Home

Astronomy C12, Earth & Planetary Science C12, Letters & Science C70
The Planets
Prof. Geoff Marcy
Prof. Michael Manga
Tu, Th 11-12:30 am
LeConte 4
Saturn’s Moon,
Dione
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Saturn & Ring
Professors
Michael Manga 177 McCone Hall
[email protected]
(office hours MWF 11:15-12:00)
Geoff Marcy
417 Campbell Hall
[email protected]
(office hours T,Th, 1pm)
Departments of Earth & Planetary Science and Astronomy
GSIs:
Gilead Wurman
Alyssa Sarid
Shuleen Martin
Jim Watkins
[email protected]
[email protected]
[email protected]
[email protected]
8 Discussion Sections
1 hr each
(Start Next Week)
Review, Clarification, Homework Help
Sign up for Section on Telebears
Text:
The Cosmic Perspective
Bennett et al. (2008) 5th Edition
(Also: Used 4th Edition)
Web Site on bspace:
http://bspace.berkeley.edu
• Syllabus, Schedule & Lecture Figures
• Assignments: Reading, Homework, Observing Project
• Class Information
Homework: 50% of your grade
• 12 assignments during semester
• Most questions from your text
• The Astronomy Learning Center (TALC):
• 264 Evans Time: Wed @ 6pm
• First homework set available Friday
• Due by Friday Feb 1
• Turn in HW every Friday at noon:
• Box labeled Astro/EPS 12 in the basement of Campbell Hall.
Homework:
• You are encouraged to work together, but MUST
turn in your own work, in your own words
• The graders can recognize copying, and answers
found with Google
• Refer to the Berkeley Code of Student conduct if you
are unclear about what constitutes cheating or
plagiarism
Announcements
• No discussion sections this week
• Read Ch 1 of the text this week; Ch 2 by next
• First Homework Assignment: posted Friday.
Last Time ::
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The Solar System
Inner Solar System
Outer Solar System
Overview
Our place in the Universe
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13 billion
Light Years
The Solar System:
Sun and 8 Planets
Moons, Asteroids, Comets, and Dust
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Milky Way Galaxy
200 Billion Stars
Photo taken from Earth
You Are Here
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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
The Universe:
All matter and energy
> 100 Billion Galaxies
Astronomical Numbers
Best to use Exponential Notation
103 = 1000
Thousand
106 = 1,000,000
Million
109 = 1,000,000,000 Billion
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
How many stars in our
visible Universe?
a)
b)
c)
d)
e)
106 (1 million)
1012 (1 million million
1018 (1 billion billion)
1022
infinite
Federal Debt
The National Debt is
$7.6 Trillion
= $7.6 x 1012
U.S. Population
= 300 x 106
Trillions of Dollars
Calculate Your Debt:
$7.6 x 1012 / 3 x 108 =
$2.5 x 104
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02 03 04 05
Debt Total
$25,000 per person
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
SI (Systeme International) Units
Base units: 1 meter (m)
length~ 3.3 ft
1 kilogram (kg)
mass
1 second (s)
time
~ 2.2 lb
MKS System of units and measure
SI (Systeme International) Units
Base units: 1 meter (m)
length
1 kilogram (kg)
1 second (s)
mass
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
UNITS ARE IMPORTANT!!!
Mars Climate Orbiter:
Launch: 11 Dec. 1998
Orbit insertion:
23 Sep. 1999
Followed by:
of Communication
Loss
WHY?
Failed to convert from English units (inches, feet, pounds)
to Metric units (MKS)
$Billion error
Light takes time to travel:
3 x 108 m/sec
= 3 x 105 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
Driving the Mars Exploration
Rovers (MER)
• How long
does it take to
communicate
with the
rovers?
NASA/JPL/Cornell
How long does it take for radio
waves (light) to reach Mars?
a)
b)
c)
d)
e)
Less than 1 second
10 seconds
5 minutes
1 day
1 year
Powers of Ten
“Cosmic Voyage”
The Movie
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
Scale 1010:
(~ 106 miles)
14 cm
1010
Scaled Down
“Sun”
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14cm
Earth diameter:
1.3 x 104 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)
0.15 cm
b)
1.5 cm
Ans: 1500 cm = 15 meters
c) 15 cm
d) 150 cm
e) 1500 cm
How large is the Solar System?
• Let’s view it to scale
– say the Sun is the size of a large grapefruit, 15 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
You Are Here:
Earth’s
Uranus
o
Saturn
o
Jupiter
o
.
Neptune
o
Orbit
How Far is the Nearest Star?
Nearest Grapefruit:
In Washington D.C.
Grapefruit-sized
Sun in Berkeley
Alpha Centauri
d = 4 light years
= 4 x 1016 m
Scales to:
4 x 106 m
(~ 3000 mi)
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
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?
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
What is the origin of the Universe?
• The two simplest atoms (H and He) were created
during the Big Bang.
• More complex atoms were created in stars.
• 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!
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.
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…
The Earth orbits around
the Sun once every year!
The Earth’s axis is tilted
by 23.5º!
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!
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!
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!
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.
You Are Here:
Earth’s Orbit
Saturn
Uranus
o
.
Neptune
o
o
Jupiter
o
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.